The nervous system is composed of specialized cells called neurons that convey messages using electrical impulses. The nervous system has two main parts: the central nervous system comprising the brain and spinal cord, and the peripheral nervous system. Neurons are classified as sensory neurons, motor neurons, or interneurons. Sensory neurons detect stimuli and transmit impulses to the central nervous system. Motor neurons transmit impulses from the central nervous system to muscles and glands. Interneurons connect sensory and motor neurons within the central nervous system. At rest, neurons maintain a negative membrane potential due to the selective permeability of the cell membrane to sodium and potassium ions. When a threshold is reached due to stimulation, an action potential is generated where the
cape biology unit 2 -_health_and_diseaseHilton Ritch
Health can be defined as a person's physical, mental and social well-being, while disease disrupts good health through disorders or malfunctions. Good health requires proper shelter, nutrition, hygiene, exercise and access to medical care. Diseases can be acute with sudden onset and short duration, or chronic with long-term effects. Smoking causes several diseases like lung cancer and heart disease by exposing the body to toxic chemicals in cigarettes that damage tissues over time. Statistics on disease patterns help identify causes and transmission routes to improve public health.
Cape biology unit 2 -_circulatory_system_in_humans_and_exerciseHilton Ritch
The circulatory system transports blood, nutrients, gases, hormones, and wastes throughout the body via the heart and blood vessels. The human circulatory system is a double circulatory system, with the heart having four chambers that separate oxygenated and deoxygenated blood. Blood flows from the heart through arteries, then narrows into arterioles before reaching capillaries where gas, nutrient and waste exchange occurs. Venules collect blood from capillaries which flows back to the heart through increasingly large veins. The heart pumps blood in a repeating cardiac cycle of atrial systole, ventricular systole and diastole.
Cape biology unit 2 -_atp_respiration_and_photosynthesis_version_2Hilton Ritch
Metabolism refers to the chemical reactions that take place in cells. These reactions are organized into metabolic pathways, with intermediates called metabolites. Catabolic reactions like respiration release energy by breaking down molecules, while anabolic reactions like photosynthesis use energy to synthesize molecules. Photosynthesis and respiration are reverse processes that convert light energy from the sun into chemical energy stored as ATP that powers cellular functions.
Cape biology unit 2-_the_kidney_and_osmoregulationHilton Ritch
The kidneys remove waste from the blood to form urine. They have an extensive blood supply so waste does not build up. Each kidney contains thousands of nephrons that filter blood to form urine in 5 steps: ultrafiltration, reabsorption, concentration in the loop of Henle, secretion in the distal tubule, and further concentration in the collecting duct. Hormones like ADH regulate water concentration to form either dilute or concentrated urine for excretion.
Cape biology uni 2 -_ecosystems_population_ecology_and_practical_methods_of_e...Hilton Ritch
This document discusses methods for estimating population sizes and distributions in ecology. It explains that directly counting all individuals in a population is often impossible, so sampling techniques are used instead to estimate population parameters. Common sampling methods described include quadrat sampling, transect sampling, and mark-release-recapture. Factors that influence the accuracy of population estimates, such as sample size and randomization, are also discussed.
The major factors that contribute to tourism development in Ocho Rios, St. Ann include its location, physical features, and population. Ocho Rios benefits from its proximity to the airport and a cruise ship dock. Its beaches, mountains, and coastal landscape attract tourists. While some residents harass tourists, others contribute to tourism through small businesses showcasing Jamaican culture, food, and art. The physical environment and local population have both helped and hindered tourism growth in Ocho Rios.
This document presents the research findings of a study on labeling theory and its impact on juvenile behavior in high schools. The study utilized questionnaires distributed to students across two high schools to collect primary data, along with statistical data from school administrators. Key findings included that lower class boys and middle class girls were more susceptible to deviant acts. Peer pressure was identified as the main motivation for such acts. Over 80% of respondents believed dysfunctional families contributed to the number of deviants in schools. The research aimed to understand the motivations and impacts of labeling on juvenile behavior, in fulfillment of the sociology syllabus requirements.
cape biology unit 2 -_health_and_diseaseHilton Ritch
Health can be defined as a person's physical, mental and social well-being, while disease disrupts good health through disorders or malfunctions. Good health requires proper shelter, nutrition, hygiene, exercise and access to medical care. Diseases can be acute with sudden onset and short duration, or chronic with long-term effects. Smoking causes several diseases like lung cancer and heart disease by exposing the body to toxic chemicals in cigarettes that damage tissues over time. Statistics on disease patterns help identify causes and transmission routes to improve public health.
Cape biology unit 2 -_circulatory_system_in_humans_and_exerciseHilton Ritch
The circulatory system transports blood, nutrients, gases, hormones, and wastes throughout the body via the heart and blood vessels. The human circulatory system is a double circulatory system, with the heart having four chambers that separate oxygenated and deoxygenated blood. Blood flows from the heart through arteries, then narrows into arterioles before reaching capillaries where gas, nutrient and waste exchange occurs. Venules collect blood from capillaries which flows back to the heart through increasingly large veins. The heart pumps blood in a repeating cardiac cycle of atrial systole, ventricular systole and diastole.
Cape biology unit 2 -_atp_respiration_and_photosynthesis_version_2Hilton Ritch
Metabolism refers to the chemical reactions that take place in cells. These reactions are organized into metabolic pathways, with intermediates called metabolites. Catabolic reactions like respiration release energy by breaking down molecules, while anabolic reactions like photosynthesis use energy to synthesize molecules. Photosynthesis and respiration are reverse processes that convert light energy from the sun into chemical energy stored as ATP that powers cellular functions.
Cape biology unit 2-_the_kidney_and_osmoregulationHilton Ritch
The kidneys remove waste from the blood to form urine. They have an extensive blood supply so waste does not build up. Each kidney contains thousands of nephrons that filter blood to form urine in 5 steps: ultrafiltration, reabsorption, concentration in the loop of Henle, secretion in the distal tubule, and further concentration in the collecting duct. Hormones like ADH regulate water concentration to form either dilute or concentrated urine for excretion.
Cape biology uni 2 -_ecosystems_population_ecology_and_practical_methods_of_e...Hilton Ritch
This document discusses methods for estimating population sizes and distributions in ecology. It explains that directly counting all individuals in a population is often impossible, so sampling techniques are used instead to estimate population parameters. Common sampling methods described include quadrat sampling, transect sampling, and mark-release-recapture. Factors that influence the accuracy of population estimates, such as sample size and randomization, are also discussed.
The major factors that contribute to tourism development in Ocho Rios, St. Ann include its location, physical features, and population. Ocho Rios benefits from its proximity to the airport and a cruise ship dock. Its beaches, mountains, and coastal landscape attract tourists. While some residents harass tourists, others contribute to tourism through small businesses showcasing Jamaican culture, food, and art. The physical environment and local population have both helped and hindered tourism growth in Ocho Rios.
This document presents the research findings of a study on labeling theory and its impact on juvenile behavior in high schools. The study utilized questionnaires distributed to students across two high schools to collect primary data, along with statistical data from school administrators. Key findings included that lower class boys and middle class girls were more susceptible to deviant acts. Peer pressure was identified as the main motivation for such acts. Over 80% of respondents believed dysfunctional families contributed to the number of deviants in schools. The research aimed to understand the motivations and impacts of labeling on juvenile behavior, in fulfillment of the sociology syllabus requirements.
The document outlines how to write a plan and design experiment for testing which color of lime (yellow or green) has a higher level of acidity. It includes sections for the problem statement, hypothesis, aim, apparatus and materials, method, variables, expected results, treatment of results, chemical principles, and sources of errors/assumptions/limitations. The hypothesis is that yellow limes have the highest acidity. The aim is to measure and compare the pH levels of lime juice from each color lime. Yellow lime juice is expected to give a lower pH reading, supporting the hypothesis that it has a higher acidity.
Caribbean Studies Internal Assessment (Sample) OmziiNella Bell
The document discusses a study on the impact of dancehall music on students at Black River High School. Data was collected through questionnaires given to students and observation at a school concert. Most students listened to dancehall for entertainment and agreed it promotes negative messages and gang violence. They felt the lyrics and artists' actions influence moods and behavior. While some saw artists as role models, most did not and suggested banning dancehall to reduce its negative effects. The findings indicate dancehall impacts students' emotions and may contribute to misconduct.
This document summarizes a study on the causes and effects of land pollution in the community of Catherine Hall, Jamaica. The study involved surveying 15 residents through questionnaires and interviews. It found that the main causes of land pollution were infrequent garbage collection, improper waste disposal by residents, and stray animals. Effects included increased medical issues for residents, decreased property values, and financial burdens. To address the problem, residents and authorities need to work together through more frequent cleanups and better waste management practices.
This document outlines the requirements and structure for a student's English SBA. It includes sections for a cover page, table of contents, plan of investigation, 3 articles with reflections, an oral presentation, and a group written report. The student must investigate a topic, analyze 3 related articles using comprehension and literary devices, reflect on what they learned, complete an oral presentation of 3-5 minutes, and contribute to a 250-300 word group report on the research process.
This document is a school-based assessment report on truancy among online students. It includes sections on the problem statement, research purpose, methodology, data collection instruments, procedures, data presentation, analysis, findings, and recommendations. The student researcher conducted an online survey of 20 students to investigate the causes of truancy in online classes. The main findings were that lack of supervision at home and lack of internet access were the primary reasons for students displaying truant behavior or not attending online classes. Recommendations included having parents join virtual classes to monitor students and address truant behavior.
1. The document describes an experiment to determine the specific heat capacity of a metal using the method of mixtures.
2. A metal sample was boiled in water for 5 minutes and then quickly transferred to a Styrofoam cup containing water.
3. The temperatures of the metal and water were measured before and after mixing to calculate the specific heat capacity of the metal, which was found to be 368°C compared to the theoretical value of 380°C.
This document summarizes two biology lab reports by a student. The first lab involved classifying 10 organisms found around the student's school into their scientific kingdoms, phyla, and classes. The second lab investigated interdependence between organisms by constructing food chains and a food web of 10 organisms and their food sources. Key findings were that organisms can be classified into taxonomic groups and that living things rely on each other through predator-prey relationships and the transfer of energy up the food chain from producers to consumers.
This paper seeks to serve as a guide to unconscious CAPE students who could use a push or central idea of what a Caribbean Studies internal assessment should look like.
This document provides an introduction and background to a research project investigating the impacts of socialization on students from single-parent families at St. Jago High School in Jamaica. The research team acknowledges those who assisted with the project. The document includes a table of contents and overview of the research design which will utilize a questionnaire to collect quantitative data from a stratified random sample of 15 students. It discusses the sociological perspective of positivism that will guide the research.
This project analyzed the fairness of a coin toss through a series of experiments. Data was collected by tossing a coin 50 times under different conditions and recording whether it landed heads or tails. The results found the probability of each side landing face up was close to the theoretical 50% probability, demonstrating a coin toss is generally unbiased. While some individual trials showed slightly more of one side, overall the differences were small. The conclusion is that a coin toss can be used as a fair way to make a random selection.
CSEC Geography- Vegetation and Soils. This document defines an ecosystem and describes the major components of an ecosystem. It also looks on the two major biomes, tropical rainforest and tropical marine.
This document contains a 10 question survey to collect data for a geography student's examination on flooding in Ward Avenue, Mandeville. The survey asks questions about the respondent's business in the area, how flooding affects them, what they believe causes flooding, and what strategies they think could help reduce flooding. Respondents are assured confidentiality and asked to answer all questions truthfully to aid the student's research.
The document is a research study on bullying among students at Princes Town West Secondary that examines the causes and effects of bullying through a questionnaire. It finds that verbal and physical bullying are most common, negatively impacting students' self-esteem, with 45% of bullied students believing the bullying is true. The study aims to understand bullying's effects to help address the issue and improve students' well-being.
This document is a school-based assessment project on alcohol consumption among students ages 13-18 in Kingston, Jamaica. The student researcher conducted a survey of 30 students at Wolmer's Boys and Girls High School using a questionnaire to understand the extent of alcohol use and factors influencing consumption. Key findings included that 30% of students drank most at ages 15-16, 50% began drinking by personal choice, and 43% reported alcohol affected their behavior negatively. The researcher recommends educating parents on consequences of underage drinking, limiting youth access to parties promoting underage alcohol use, and enforcing strict rules for event promoters.
The document is a student portfolio on depression among teenagers in Trinidad and Tobago. It includes an introduction outlining the purpose of examining this issue and discussing the author's personal connection. It also includes a table of contents, preface, reflective short story, and analysis. The reflective short story, titled "Beena's Dilemma", depicts the life of a teenager named Beena who is suffering from depression due to bullying at school and abuse at home from her alcoholic father. After being verbally abused by her father one night, Beena attempts suicide by slashing her wrists. She is rushed to the hospital and survives. Her parents realize their role in her depression and seek counselling and therapy to help Beena
Cape biology unit 2 -_matter_and_energy_flow__recycling_in_the_environmentHilton Ritch
The document discusses energy and matter, food chains, and material and nutrient cycles in ecosystems. It defines key terms like producers, consumers, trophic levels, and decomposers. It explains that energy enters ecosystems from the sun and is either passed up food chains, stored in detritus, or lost as heat. Matter cycles between biotic and abiotic parts of ecosystems, with producers taking in simple molecules like CO2 and releasing complex organic molecules, and decomposers breaking these down and releasing simple molecules. Microbes play major roles in nutrient cycles like carbon and nitrogen.
A student named Shavaun Salmon is conducting a survey for a school assignment on marijuana abuse in their community. The letter requests assistance answering a series of multiple choice and open-ended questions about marijuana use, including age, occupation, ethnicity, frequency of use, sources of marijuana, reasons for using, and strategies to stop smoking marijuana. The responses will be kept confidential.
English SBA for CSEC. *The file has been protected and has been submitted to CXC. Do not copy as the digital signature of the file cannot be removed or edited. Use as a guide only
This document is a social studies research project submitted by Raheme Matthie to investigate unemployment in the George Mason Drive community. It includes an introduction outlining the topic, a statement of the problem, and reasons for selecting the topic. It then describes the methodology, which involved distributing questionnaires. The findings from analyzing the collected data show that most unemployed persons are males between 19-25 years old. It was found that the main causes of unemployment were a lack of education and skills training. The recommendations call for more educational and job opportunities to address unemployment in the community.
cape biology unit 2-_transport_systems_in_plantsHilton Ritch
Plants have sophisticated transport systems to move water and nutrients throughout the plant. Water and dissolved minerals are transported up the xylem vessel through root, stem, and into the leaves. Transpiration through leaf stomata creates a pulling force that draws water up the xylem. Sugars produced by photosynthesis are actively transported down the phloem to areas in need, such as roots and growing parts. The mass flow mechanism uses energy from active transport and transpiration to circulate fluids between the xylem and phloem.
This document provides information about the structure and properties of water and carbohydrates. It begins by explaining the chemical structure of water molecules and how hydrogen bonding gives water unique properties important for life, such as being an excellent solvent and having a high heat capacity. It then discusses monosaccharides like glucose, disaccharides like sucrose, and polysaccharides like starch, glycogen and cellulose. Starch is the plant storage polysaccharide while glycogen serves the same function in animals. Cellulose forms strong cell walls in plants. Carbohydrates exist as monomers, dimers and polymers joined by glycosidic bonds.
The document outlines how to write a plan and design experiment for testing which color of lime (yellow or green) has a higher level of acidity. It includes sections for the problem statement, hypothesis, aim, apparatus and materials, method, variables, expected results, treatment of results, chemical principles, and sources of errors/assumptions/limitations. The hypothesis is that yellow limes have the highest acidity. The aim is to measure and compare the pH levels of lime juice from each color lime. Yellow lime juice is expected to give a lower pH reading, supporting the hypothesis that it has a higher acidity.
Caribbean Studies Internal Assessment (Sample) OmziiNella Bell
The document discusses a study on the impact of dancehall music on students at Black River High School. Data was collected through questionnaires given to students and observation at a school concert. Most students listened to dancehall for entertainment and agreed it promotes negative messages and gang violence. They felt the lyrics and artists' actions influence moods and behavior. While some saw artists as role models, most did not and suggested banning dancehall to reduce its negative effects. The findings indicate dancehall impacts students' emotions and may contribute to misconduct.
This document summarizes a study on the causes and effects of land pollution in the community of Catherine Hall, Jamaica. The study involved surveying 15 residents through questionnaires and interviews. It found that the main causes of land pollution were infrequent garbage collection, improper waste disposal by residents, and stray animals. Effects included increased medical issues for residents, decreased property values, and financial burdens. To address the problem, residents and authorities need to work together through more frequent cleanups and better waste management practices.
This document outlines the requirements and structure for a student's English SBA. It includes sections for a cover page, table of contents, plan of investigation, 3 articles with reflections, an oral presentation, and a group written report. The student must investigate a topic, analyze 3 related articles using comprehension and literary devices, reflect on what they learned, complete an oral presentation of 3-5 minutes, and contribute to a 250-300 word group report on the research process.
This document is a school-based assessment report on truancy among online students. It includes sections on the problem statement, research purpose, methodology, data collection instruments, procedures, data presentation, analysis, findings, and recommendations. The student researcher conducted an online survey of 20 students to investigate the causes of truancy in online classes. The main findings were that lack of supervision at home and lack of internet access were the primary reasons for students displaying truant behavior or not attending online classes. Recommendations included having parents join virtual classes to monitor students and address truant behavior.
1. The document describes an experiment to determine the specific heat capacity of a metal using the method of mixtures.
2. A metal sample was boiled in water for 5 minutes and then quickly transferred to a Styrofoam cup containing water.
3. The temperatures of the metal and water were measured before and after mixing to calculate the specific heat capacity of the metal, which was found to be 368°C compared to the theoretical value of 380°C.
This document summarizes two biology lab reports by a student. The first lab involved classifying 10 organisms found around the student's school into their scientific kingdoms, phyla, and classes. The second lab investigated interdependence between organisms by constructing food chains and a food web of 10 organisms and their food sources. Key findings were that organisms can be classified into taxonomic groups and that living things rely on each other through predator-prey relationships and the transfer of energy up the food chain from producers to consumers.
This paper seeks to serve as a guide to unconscious CAPE students who could use a push or central idea of what a Caribbean Studies internal assessment should look like.
This document provides an introduction and background to a research project investigating the impacts of socialization on students from single-parent families at St. Jago High School in Jamaica. The research team acknowledges those who assisted with the project. The document includes a table of contents and overview of the research design which will utilize a questionnaire to collect quantitative data from a stratified random sample of 15 students. It discusses the sociological perspective of positivism that will guide the research.
This project analyzed the fairness of a coin toss through a series of experiments. Data was collected by tossing a coin 50 times under different conditions and recording whether it landed heads or tails. The results found the probability of each side landing face up was close to the theoretical 50% probability, demonstrating a coin toss is generally unbiased. While some individual trials showed slightly more of one side, overall the differences were small. The conclusion is that a coin toss can be used as a fair way to make a random selection.
CSEC Geography- Vegetation and Soils. This document defines an ecosystem and describes the major components of an ecosystem. It also looks on the two major biomes, tropical rainforest and tropical marine.
This document contains a 10 question survey to collect data for a geography student's examination on flooding in Ward Avenue, Mandeville. The survey asks questions about the respondent's business in the area, how flooding affects them, what they believe causes flooding, and what strategies they think could help reduce flooding. Respondents are assured confidentiality and asked to answer all questions truthfully to aid the student's research.
The document is a research study on bullying among students at Princes Town West Secondary that examines the causes and effects of bullying through a questionnaire. It finds that verbal and physical bullying are most common, negatively impacting students' self-esteem, with 45% of bullied students believing the bullying is true. The study aims to understand bullying's effects to help address the issue and improve students' well-being.
This document is a school-based assessment project on alcohol consumption among students ages 13-18 in Kingston, Jamaica. The student researcher conducted a survey of 30 students at Wolmer's Boys and Girls High School using a questionnaire to understand the extent of alcohol use and factors influencing consumption. Key findings included that 30% of students drank most at ages 15-16, 50% began drinking by personal choice, and 43% reported alcohol affected their behavior negatively. The researcher recommends educating parents on consequences of underage drinking, limiting youth access to parties promoting underage alcohol use, and enforcing strict rules for event promoters.
The document is a student portfolio on depression among teenagers in Trinidad and Tobago. It includes an introduction outlining the purpose of examining this issue and discussing the author's personal connection. It also includes a table of contents, preface, reflective short story, and analysis. The reflective short story, titled "Beena's Dilemma", depicts the life of a teenager named Beena who is suffering from depression due to bullying at school and abuse at home from her alcoholic father. After being verbally abused by her father one night, Beena attempts suicide by slashing her wrists. She is rushed to the hospital and survives. Her parents realize their role in her depression and seek counselling and therapy to help Beena
Cape biology unit 2 -_matter_and_energy_flow__recycling_in_the_environmentHilton Ritch
The document discusses energy and matter, food chains, and material and nutrient cycles in ecosystems. It defines key terms like producers, consumers, trophic levels, and decomposers. It explains that energy enters ecosystems from the sun and is either passed up food chains, stored in detritus, or lost as heat. Matter cycles between biotic and abiotic parts of ecosystems, with producers taking in simple molecules like CO2 and releasing complex organic molecules, and decomposers breaking these down and releasing simple molecules. Microbes play major roles in nutrient cycles like carbon and nitrogen.
A student named Shavaun Salmon is conducting a survey for a school assignment on marijuana abuse in their community. The letter requests assistance answering a series of multiple choice and open-ended questions about marijuana use, including age, occupation, ethnicity, frequency of use, sources of marijuana, reasons for using, and strategies to stop smoking marijuana. The responses will be kept confidential.
English SBA for CSEC. *The file has been protected and has been submitted to CXC. Do not copy as the digital signature of the file cannot be removed or edited. Use as a guide only
This document is a social studies research project submitted by Raheme Matthie to investigate unemployment in the George Mason Drive community. It includes an introduction outlining the topic, a statement of the problem, and reasons for selecting the topic. It then describes the methodology, which involved distributing questionnaires. The findings from analyzing the collected data show that most unemployed persons are males between 19-25 years old. It was found that the main causes of unemployment were a lack of education and skills training. The recommendations call for more educational and job opportunities to address unemployment in the community.
cape biology unit 2-_transport_systems_in_plantsHilton Ritch
Plants have sophisticated transport systems to move water and nutrients throughout the plant. Water and dissolved minerals are transported up the xylem vessel through root, stem, and into the leaves. Transpiration through leaf stomata creates a pulling force that draws water up the xylem. Sugars produced by photosynthesis are actively transported down the phloem to areas in need, such as roots and growing parts. The mass flow mechanism uses energy from active transport and transpiration to circulate fluids between the xylem and phloem.
This document provides information about the structure and properties of water and carbohydrates. It begins by explaining the chemical structure of water molecules and how hydrogen bonding gives water unique properties important for life, such as being an excellent solvent and having a high heat capacity. It then discusses monosaccharides like glucose, disaccharides like sucrose, and polysaccharides like starch, glycogen and cellulose. Starch is the plant storage polysaccharide while glycogen serves the same function in animals. Cellulose forms strong cell walls in plants. Carbohydrates exist as monomers, dimers and polymers joined by glycosidic bonds.
This document provides an overview of Caribbean society and culture. It discusses the geographic location and definitions of the Caribbean region, as well as characteristics of Caribbean society such as cultural diversity and the impact of historical processes like slavery and indentureship. The document also examines social stratification in the Caribbean and the hybridization of cultures. It analyzes the effects of geography, institutions, and global interactions on Caribbean society and culture, as well as Caribbean influences abroad through areas like migration, music, and festivals.
The document discusses the evolution of nervous systems across different animal species. It begins with the simplest nervous systems found in cnidarians like hydra, which have a nerve net without central control. It then covers increasing centralization in jellyfish and other species. Bilateral animals showed cephalization with sensory organs and feeding structures concentrated in the head. Invertebrates like worms, insects, and mollusks exhibited more complex centralized nervous systems. Research on invertebrate systems like squid giant axons provided insights. Vertebrate brains evolved from three bulges at the front of the spinal cord. Trends in vertebrate brains included increasing size, compartmentalization, and convolutions. Mammalian brains incorporated
Lina Vargas attends bartending school from 6:30 am to 1:30 pm on Mondays and Fridays. Her daily routine includes waking up at 5:15 am, making her bed, taking a shower, eating breakfast at 6:10 am, and leaving for school by 6:30 am. After returning home at 1:30 pm, she has lunch at 2:00 pm, does chores and homework, watches TV, has dinner with her family at 8:00 pm, and goes to bed at 10:00 pm.
This short document promotes creating presentations using Haiku Deck, a tool for making slideshows. It encourages the reader to get started making their own Haiku Deck presentation and sharing it on SlideShare. In just one sentence, it pitches the idea of using Haiku Deck to easily create engaging slideshows.
The presentation shows how much the developed countries releases carbon di oxide every year compared to India, the source wise gas releases, the effect of Global warming on Crop production and water use,What are the action needed by Government to minimize gas releases and in the last slide what the public can do to decrease the gas release to control Global warming. This is a summary for public awareness.
cape biology unit 2 -_respiration_and_photosynthesis_version_1Hilton Ritch
Metabolism refers to the chemical reactions that take place in cells. There are thousands of metabolic reactions that are organized into pathways. The two main types are catabolic reactions, which release energy, and anabolic reactions, which use energy. Photosynthesis and cellular respiration are key metabolic pathways that involve the interconversion of light energy, chemical energy, and heat energy. Cellular respiration breaks down glucose and uses oxygen to produce carbon dioxide, water, and ATP as energy. It takes place in three main stages - glycolysis, the Krebs cycle, and the electron transport chain - within the mitochondria. Photosynthesis is the reverse process that uses light energy, carbon dioxide, and water to produce glucose and oxygen. It also occurs
cape biology unit 2-_hb_dissociation_curve_and_bloodHilton Ritch
- Blood has several vital functions including transport, defense, formation of lymph and tissue fluid, and homeostasis. It is composed of plasma, red blood cells, white blood cells, and platelets.
- Red blood cells contain hemoglobin which transports oxygen. They are biconcave in shape to maximize surface area for gas exchange.
- White blood cells help defend the body against pathogens and produce antibodies. There are two main types: granulocytes and agranulocytes.
- Platelets help form blood clots to prevent blood loss from damaged blood vessels.
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Licia Dones wants to become a health educator after witnessing her grandfather's struggles with diabetes and kidney failure that resulted in an amputation. Seeing family and friends disregard their health made Licia believe that with proper education on health conditions, lives could be improved or saved. Licia sees the role of a health educator as providing patients information to prevent health issues and make suggestions, rather than prescribing treatments. Health educators can reach diverse populations in various settings such as schools, hospitals, and corporations. Licia's coursework is enhancing her knowledge to become a successful health educator, and she has experience educating others, such as high school students about sexually transmitted diseases. Licia's philosophy is to "Educate
This document summarizes the results of a survey on substance use, mental health, risky behaviors, and service needs among grade 8-10 learners in Western Cape schools in 2011. Some key findings include:
- Alcohol, tobacco, and cannabis were the most commonly used substances. Two-thirds of learners reported alcohol use, nearly half reported tobacco use, and about a quarter reported cannabis use.
- Males generally reported higher rates of substance use than females. They were more likely to report behaviors like binge drinking, weekly alcohol and tobacco use, and smoking more than 10 cigarettes per day.
- Hard drug use like cocaine, mandrax, ecstasy, heroin, and methamphetamine was relatively low at
This document defines excitable tissues as nerve and muscle tissues that can receive and respond to stimuli. It describes the structure and function of neurons, including their different parts like dendrites, cell body, axon, and synaptic knobs. It explains how action potentials are generated through changes in ion channel permeability, and how they propagate along axons. It also describes how neurons communicate through chemical synaptic transmission, releasing neurotransmitters that can induce excitatory or inhibitory postsynaptic potentials.
This document discusses neurons and neuronal communication. It describes two main types of communication - neuronal communication via electrical signals transmitted by neurons, and hormonal communication via slower-acting chemical signals from hormones. It provides details on the structure and function of neurons, including the key parts of neurons (cell body, dendrites, axon), properties of excitability and conductivity, and types of neurons (sensory, intermotor, motor). The document explains the mechanisms of neuronal signaling, including resting membrane potential, action potentials, and synaptic transmission. It compares chemical and electrical synapses and provides illustrations and animations of these processes.
This document discusses the resting membrane potential in neurons. It explains that the plasma membrane of a resting neuron is polarized with negatively charged fluid inside and positively charged fluid outside, resulting in a resting membrane potential of around -70 mV. This polarization is maintained by the sodium-potassium pump and concentration gradients of sodium and potassium ions. When an action potential is triggered, the permeability to sodium ions increases, causing depolarization and propagating the nerve impulse down the axon.
The document discusses how nerve cells transmit impulses through the nervous system. It explains that:
- Nerve cells have a resting potential of around -70mV due to the distribution of ions inside and outside the cell.
- When a nerve is stimulated, it causes voltage-gated sodium channels to open, allowing sodium ions to rush in and depolarize the cell. This creates an action potential.
- The cell then repolarizes as sodium channels close and potassium channels open, restoring the resting potential and allowing another impulse to be transmitted.
- This process of depolarization and repolarization via ion channel activation allows rapid and efficient transmission of nerve impulses through the nervous system.
Lab Report- Neurophysiology Of Nerve Impulses EssayStephanie King
The document provides an overview of nerve impulses and action potentials in neurons. It discusses:
1) Neurons transmit electro-chemical signals via extensions called dendrites that receive signals and axons that transmit signals to other neurons.
2) When a neuron is stimulated, sodium ion channels open to depolarize the membrane and potassium channels then open to repolarize it, generating an action potential.
3) Myelin insulates axons to speed up action potential propagation between nodes of Ranvier, where regeneration occurs.
A compound action potential (CAP) is the summed response of multiple single action potentials from different nerve fibers within a nerve. A CAP differs from a single action potential in that it exhibits graded responses based on stimulus intensity, with higher intensities activating more fibers and producing a larger CAP. Increasing the stimulus intensity results in progressively more nerve fibers reaching threshold and contributing to the CAP until all fibers are activated, producing the maximal CAP response. Other stimulus parameters like frequency and duration can also affect a nerve's ability to generate a CAP.
The nervous system allows for coordination in the body through electrochemical signaling between neurons. It consists of neurons and neuroglia. Neurons receive and transmit signals via dendrites, the cell body, and the axon. There are three types of neurons - sensory, motor, and inter. A nerve impulse is generated through changes in the neuron's membrane potential and the opening and closing of ion channels, causing the signal to propagate along the axon. At a synapse, neurotransmitters transmit the signal to the next neuron. Reflexes are automatic responses to stimuli.
An action potential occurs when a neuron reaches its membrane threshold. This causes sodium channels to open, allowing sodium ions to enter the neuron and depolarize the membrane. Then, potassium channels open, allowing potassium ions to exit the neuron and repolarize the membrane back to its resting potential. This process of depolarization and repolarization propagates as a self-sustaining wave along the neuron, conducting the nerve impulse. Myelinated neurons enhance conduction velocity through salutatory conduction, where the action potential jumps between nodes of Ranvier.
This document provides information about synapses and synaptic transmission in the central nervous system (CNS). It defines a synapse as the junction between two neurons and discusses the key anatomical structures involved, including the presynaptic terminal, synaptic cleft, and postsynaptic membrane. It describes how an action potential in the presynaptic neuron leads to calcium ion influx and neurotransmitter release into the synaptic cleft. The neurotransmitters then bind to receptors on the postsynaptic membrane, which can result in excitation via EPSPs or inhibition via IPSPs depending on the specific neurotransmitter and receptor type involved. Higher-level functions such as learning and memory emerge from the complex integration of signals at numerous synapses throughout the CNS neural circuits.
1) Neurons communicate with each other via electrical and chemical signals. Electrical signals allow for faster transmission than just chemical signals alone.
2) The basic parts of a neuron include dendrites that receive signals, an axon that conducts signals, and axon terminals that transmit signals to other cells at synapses. Some neurons have a fatty myelin sheath that insulates the axon and speeds transmission.
3) Neurons maintain a voltage difference across their cell membranes called the membrane potential. An "action potential" is generated when the membrane potential rapidly changes, propagating a nerve impulse down the axon via voltage-gated ion channels.
1. Neuron membrane maintains resting potential until threshold stimulus is received.
2. Sodium channels open, sodium ions diffuse in, depolarizing the membrane.
3. Potassium channels open, potassium ions diffuse out, repolarizing the membrane.
4. The resulting action potential propagates as a nerve impulse down the axon.
The nervous system is composed of the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS). The CNS receives sensory input, integrates information, and directs motor responses. Within the CNS, the brain is responsible for higher functions like thinking and memory, while the spinal cord transmits signals between the brain and body. Neurons are the basic functional units and communicate via electrical and chemical signals across synapses. The nervous system allows animals to integrate internal and external sensory information to direct activities and maintain homeostasis.
The Resting Potential And The Action Potentialneurosciust
An action potential occurs when a neuron is stimulated enough to reach its threshold of excitation. This causes sodium channels to open, allowing sodium to rush into the neuron and depolarize it. The neuron then repolarizes as potassium leaves and the sodium-potassium pump restores the ion gradients. After an action potential, the neuron enters an absolute refractory period where it cannot fire again, followed by a relative refractory period where a stronger stimulus is needed to trigger another action potential. This process allows neurons to rapidly transmit signals down axons to synapse with other neurons.
Synapses consist of a presynaptic ending containing neurotransmitters, a postsynaptic ending containing receptor sites, and a synaptic cleft between them. An action potential cannot cross the cleft; instead, neurotransmitters are released from vesicles in the presynaptic ending and diffuse across the cleft to bind to receptors in the postsynaptic ending. This may initiate an action potential in the postsynaptic neuron. Synapses allow neurons to communicate via chemical signaling and integrate inputs from multiple neurons.
This document discusses neurophysiology and summarizes key aspects of nerve cells and signal transmission. It describes the basic anatomy of neurons including the cell body, dendrites, axon, and synaptic terminals. It explains how myelin sheaths insulate neurons and how synapses facilitate chemical transmission between neurons. It also summarizes how nerve impulses are generated through changes in ion permeability and the roles of sodium-potassium pumps in restoring polarization.
The document summarizes the structure and function of the human nervous system. It describes the three main types of neurons - sensory, motor, and interneurons - and how they transmit nerve impulses via electrical and chemical signals. It also explains the process of synaptic transmission between neurons and how homeostasis is maintained through negative feedback mechanisms that monitor and respond to changes in the internal environment.
Sensory receptors detect changes in the environment and transmit this information as nerve impulses along neurons. At synapses, neurotransmitters are released by the presynaptic neuron and bind to receptors on the postsynaptic neuron, generating an action potential if the threshold is reached. Myelination speeds up signal transmission along long neurons. Communication between neurons allows homeostasis to be maintained.
The document summarizes key concepts about the nervous system including:
- Neurons are the basic structural and functional units that transmit electrochemical signals called nerve impulses. Nerves are bundles of axons.
- The central nervous system (CNS) contains gray matter with neuron cell bodies and unmyelinated axons, and white matter with bundles of myelinated axons.
- There are three main types of neurons - sensory, interneurons, and motor neurons. Neuroglial cells provide support and insulation for neurons in the CNS.
- The peripheral nervous system connects the CNS to other body parts and allows sensory input, integrative processing, and motor output functions.
The document summarizes the neural and endocrine systems. It describes how the central nervous system is connected to the peripheral nervous system via afferent and efferent nerves. It also explains the basic structure and function of neurons, including their cell bodies, dendrites, axons, and how nerve impulses are transmitted through myelinated and unmyelinated fibers. Synaptic transmission between neurons is discussed.
1) An impulse travels along a neuron when the inside becomes more positively charged than the outside due to the flow of sodium ions into the cell during depolarization.
2) The sodium-potassium pump normally keeps the inside negatively charged by pumping out 3 sodium ions and pumping in 2 potassium ions for each pump cycle.
3) When the membrane potential reaches threshold, voltage-gated sodium channels open, sodium rushes in, and the inside becomes positively charged, allowing the impulse to move along. Then, voltage-gated potassium channels open and potassium exits, repolarizing the cell back to its resting potential.
Similar to cape biology unit 2-_fundamentals_of_the_nervous_system (20)
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
Philippine Edukasyong Pantahanan at Pangkabuhayan (EPP) CurriculumMJDuyan
(𝐓𝐋𝐄 𝟏𝟎𝟎) (𝐋𝐞𝐬𝐬𝐨𝐧 𝟏)-𝐏𝐫𝐞𝐥𝐢𝐦𝐬
𝐃𝐢𝐬𝐜𝐮𝐬𝐬 𝐭𝐡𝐞 𝐄𝐏𝐏 𝐂𝐮𝐫𝐫𝐢𝐜𝐮𝐥𝐮𝐦 𝐢𝐧 𝐭𝐡𝐞 𝐏𝐡𝐢𝐥𝐢𝐩𝐩𝐢𝐧𝐞𝐬:
- Understand the goals and objectives of the Edukasyong Pantahanan at Pangkabuhayan (EPP) curriculum, recognizing its importance in fostering practical life skills and values among students. Students will also be able to identify the key components and subjects covered, such as agriculture, home economics, industrial arts, and information and communication technology.
𝐄𝐱𝐩𝐥𝐚𝐢𝐧 𝐭𝐡𝐞 𝐍𝐚𝐭𝐮𝐫𝐞 𝐚𝐧𝐝 𝐒𝐜𝐨𝐩𝐞 𝐨𝐟 𝐚𝐧 𝐄𝐧𝐭𝐫𝐞𝐩𝐫𝐞𝐧𝐞𝐮𝐫:
-Define entrepreneurship, distinguishing it from general business activities by emphasizing its focus on innovation, risk-taking, and value creation. Students will describe the characteristics and traits of successful entrepreneurs, including their roles and responsibilities, and discuss the broader economic and social impacts of entrepreneurial activities on both local and global scales.
Chapter wise All Notes of First year Basic Civil Engineering.pptxDenish Jangid
Chapter wise All Notes of First year Basic Civil Engineering
Syllabus
Chapter-1
Introduction to objective, scope and outcome the subject
Chapter 2
Introduction: Scope and Specialization of Civil Engineering, Role of civil Engineer in Society, Impact of infrastructural development on economy of country.
Chapter 3
Surveying: Object Principles & Types of Surveying; Site Plans, Plans & Maps; Scales & Unit of different Measurements.
Linear Measurements: Instruments used. Linear Measurement by Tape, Ranging out Survey Lines and overcoming Obstructions; Measurements on sloping ground; Tape corrections, conventional symbols. Angular Measurements: Instruments used; Introduction to Compass Surveying, Bearings and Longitude & Latitude of a Line, Introduction to total station.
Levelling: Instrument used Object of levelling, Methods of levelling in brief, and Contour maps.
Chapter 4
Buildings: Selection of site for Buildings, Layout of Building Plan, Types of buildings, Plinth area, carpet area, floor space index, Introduction to building byelaws, concept of sun light & ventilation. Components of Buildings & their functions, Basic concept of R.C.C., Introduction to types of foundation
Chapter 5
Transportation: Introduction to Transportation Engineering; Traffic and Road Safety: Types and Characteristics of Various Modes of Transportation; Various Road Traffic Signs, Causes of Accidents and Road Safety Measures.
Chapter 6
Environmental Engineering: Environmental Pollution, Environmental Acts and Regulations, Functional Concepts of Ecology, Basics of Species, Biodiversity, Ecosystem, Hydrological Cycle; Chemical Cycles: Carbon, Nitrogen & Phosphorus; Energy Flow in Ecosystems.
Water Pollution: Water Quality standards, Introduction to Treatment & Disposal of Waste Water. Reuse and Saving of Water, Rain Water Harvesting. Solid Waste Management: Classification of Solid Waste, Collection, Transportation and Disposal of Solid. Recycling of Solid Waste: Energy Recovery, Sanitary Landfill, On-Site Sanitation. Air & Noise Pollution: Primary and Secondary air pollutants, Harmful effects of Air Pollution, Control of Air Pollution. . Noise Pollution Harmful Effects of noise pollution, control of noise pollution, Global warming & Climate Change, Ozone depletion, Greenhouse effect
Text Books:
1. Palancharmy, Basic Civil Engineering, McGraw Hill publishers.
2. Satheesh Gopi, Basic Civil Engineering, Pearson Publishers.
3. Ketki Rangwala Dalal, Essentials of Civil Engineering, Charotar Publishing House.
4. BCP, Surveying volume 1
B. Ed Syllabus for babasaheb ambedkar education university.pdf
cape biology unit 2-_fundamentals_of_the_nervous_system
1. The Nervous System - Summary
The 'neurone'
The nervous system carries messages around the body using specialised cells
calledneurones. Neurones convey their 'messages' using electrical impulses.
The central nervous system and the peripheral nervous system
The nervous system (NS) is made up of two parts:
Central nervous system comprising the brain and spinal cord.
Peripheral nervous system.
A simple way of thinking about the interaction between the two systems is to imagine
them as roads, and the messages as cars.
The 'car' starts off in small roads (peripheral nervous system) and heads towards to
the brain. In order to get there faster it takes the motorway (central nervous
system) which gets the 'car' to its final destination - the brain - very quickly.
See how this happens in the diagram below:
The somatic (voluntary) and autonomic (involuntary) nervous system
Different areas of the nervous system are used for different types of nervous
reaction:
Conscious control - for example, your brain consciously deciding to move a moving
skeletal muscle, and this uses the somatic/voluntary NS.
Non-conscious control - for example, your body automatically reacting to, and this
uses the autonomic NS.
Generally, with the autonomic NS, if the outcome increases activity - for example, if the
heart rate goes up, it involves the sympathetic NS.
If the outcome is to decrease activity - for example, if the breathing rate goes down, it
involves theparasympathetic NS.
2. Sensory neurones and motor neurones
Receptors are cells that detect stimuli - for example, heat, pressure, light.
Sensory neurones bring impulses from receptors to the central nervous system
(CNS).
From there, the impulse may pass on to a motor neurone to be taken to a muscle or
gland (the effector).
Sometimes there is an intermediate neurone (also known as a 'relay' neurone)
within the CNS linking the sensory neurone with the motor neurone.
To be able to understand how the impulses are transmitted through a neurone, you
must first know what the cell is like at rest.
3. Formation and Transmission of Impulses
Resting potential
In the surface membrane of a cell there are protein carriers.
These actively pump Na+ (Sodium) ions out of the cytoplasm to the outside of the cell.
At the same time, K+ (Potassium) ions are pumped from the outside in.
This active pumping of Na+ and K+ ions requires energy (in the form of ATP) because
the ions are being moved against their concentration gradients (from where they are at
a lower concentration to where they are at a higher concentration). K+ and Na+ ions
diffuse back down their concentration gradient but K+ diffuses back out of the cell
faster than Na+ can diffuse back in.
This means there is a net movement of positive ions out of the cell making the inside of
the cell negatively charged, relative to the outside.
This charge is the resting potential of the cell and is about -70mV.
Action potential
When a receptor is stimulated, it will create a positive environment inside the cell.
This is caused by a change in the concentrations of Na+ and K+ ions in the
cell and happens in a number of steps:
1. There is a change in permeability (the ability of the cell membrane to let ions through
it) to Na+ and K+ in the cell surface membrane at the area of stimulation, which
causes Na+ channels in that area to open.
2. Na+ therefore floods into the cytoplasm down the concentration gradient.
3. As this happens the membrane depolarises (this means that the resting potential of
the cells starts to decrease). If this depolarisation reaches a certain level, called
the threshold level (about -55 to -50 mV), then an action potential has been
generated and an impulse will be fired. If it does not reach this level, nothing will
happen.
4. Once +40mV is reached the Na+ channels close and K+ channels open. K+ floods out of
the cytoplasm so that the overall charge inside goes back down. This stage is
called repolarisation.
4. 5. The K+ channels then close, the sodium-potassium pump restarts, restoring the normal
distribution of ions either side of the cell surface membrane and thus restoring the
resting potential.
An example of an action potential being reached would be pressure receptors cells in
the skin which. If your hand was squashed, the pressure receptors cells in your skin
would be would be pressed out of shape (this would be the external stimuli).
In response to this the Na+ channels in that area would open up, allowing Na+ ions to
flood into the cell and thus reducing the resting potential of the cells. If the resting
potential of the cell drops to the threshold level, then an action potential has been
generated and an impulse will be fired.
The above has only described one area of the neurone and not how the impulse is
carried along the neuron, this happens by another chain reaction.
Once an impulse is made, a local current is set up between the area where there is an
action potential and the resting area next to it. The flow of some Na+ sideways towards
the negative area next to it causes the Na+channels in that area to open and
depolarisation to occur there. That way, the action potential is moved down the
neurone.
There is a length of time called the refractory period when the resting potential is
being re-established. During this time no new action potential can be generated.
In this way the action potential can only travel in one direction down the neurone
because the area behind the action potential is in a state of recovery.
Saltatory conduction
Generally cells are covered in a fatty myelin sheath and therefore the Na+ and
K+ cannot flow through this. This means that the ions can only flow through
unprotected cell-surface membrane.
In the case of a myelinated neurone, the ions can only move in and out of the
cytoplasm at the nodes of Ranvier.
Because of this, the action potential will 'jump' from one node to the next, a process
called saltatory conduction, and so will travel much faster than in an unmyelinated
neurone.
Other factors that affect the speed of conduction are diameter of the axon (the bigger,
the faster) and temperature (up to 40°C, the higher the faster).
5. Action potentials themselves do not change size as they move down the neurone. All
stimuli, as long as they cause the threshold level to be reached, cause an action
potential of +40mV, no more or less. The speed of conduction is not altered by the
intensity of the stimulus either.
If the stimulus is large, it will produce a greater frequency of impulses. Another one will
very quickly follow the previous action potential (i.e. the intensity is frequency
modulated).
Another consequence of an intense stimulus is that more than one neurone is likely to
be affected. That way the brain, receiving more action potentials from more neurones,
will interpret the stimulus as being strong.
Synapses
When an action potential reaches the end of one neurone there must be a way to start
an action potential in the next neurone.
The two neurons will not be in direct contact and action potentials cannot jump across
the gap, called a synapse (or synaptic cleft), so another method is employed...
Release of neurotransmitters
As you can see above, the electrical impulse cannot cross the synaptic cleft, so a
chemical called aneurotransmitter is released at the end of the first neurone out of
the presynaptic membrane. It diffuses across the synapse, binds with the second
neurone on the postsynaptic membrane and generates an action potential.
Two examples of neurotransmitters are acetylcholine (ACL) and noradrenaline.
They are synthesised in vesicles, which requires energy, so the synaptic knobs have
many ATP-producing mitochondria in them.
Generation of a new action potential
As the action potential reaches the end of the first neurone, Ca2+ channels are also
opened. Ca2+ flows into the cell and this induces several hundred vesicles containing
the neurotransmitter to fuse with the presynaptic membrane. The neurotransmitter is
released into the synaptic cleft.
The molecules of neurotransmitter bind with complementary receptors (similar to an
enzyme and substrate fitting together) in the postsynaptic membrane. This makes the
6. Na+ channels open and depolarisation occurs in the postsynaptic membrane thus
starting an action potential.
To stop the neurotransmitter continually generating action potentials either the
neurotransmitter is actively absorbed back into the presynaptic neurone or an enzyme
is released to break it down before reabsorption.
Synapses break up the flow of action potentials and so slow down the
transmission of impulses but they are useful...
they ensure that the impulses travel only in one direction.
they allow neurons to connect via neurotransmitters with many, many other neurons.
This increases the range of possible responses to any particular stimulus or group of
stimuli.
Many drugs act by affecting the events at synapses:
Nicotine:
Lowers the threshold for activation of neurons by mimicking the
action of acetylcholine on the post-synaptic membrane because
it is a similar shape.
Caffeine:
Causes the release of calcium ions from cell stores, thereby
making firing easier.
Organophosphate
insecticides:
Prevent the enzyme breaking down acetylcholine after it has
produced an action potential. This allows acetylcholine to
produce a continuous stream of action potentials, leading to an
uncoordinated response in the effectors.
Curare:
(Used on the tips of arrows by some tribes) blocks the
acetylcholine at the junction between neurone and muscles.
This means that the victim is paralysed. Also used medically as
a reversible muscle relaxant during heart surgery.
7. The Nervous System – Details
Humans, like all living organisms, can respond to their environment. Humans have two complimentary
control systems to do this: the nervous system and the endocrine (hormonal) system. The human nervous
system controls everything from breathing and producing digestive enzymes, to memory and intelligence.
Nerve Cells
The nervous system composed of nerve cells, or neurones:
Motor Neurone:
Efferent Neuron – Moving toward a central organ or point
Relays messages from the brain or spinal cord to the muscles and organs
Sensory Neurone:
Afferent Neuron – Moving away from a central organ or point
Relays messages from receptors to the brain or spinal cord
9. Sensory neuron Interneuron Motor Neuron
Length of
Fibers
Long dendrites and short
axon
Short dendrites and short or
long anxon
Short dendrites and long
axons
Location
Cell body and dendrite are
outside of the spinal cord;
the cell body is located in a
dorsal root ganglion
Entirely within the spinal
cord or CNS
Dendrites and the cell body
are located in the spinal
cord; the axon is outside of
the spinal cord
Function
Conduct impulse to the
spinal cord
Interconnect the sensory
neuron with appropriate
motor neuron
Conduct impulse to an
effector (muscle or gland)
A neurone has a cell body with extensions leading off it. Numerous dendrons and dendrites provide a
large surface area for connecting with other neurones, and carry nerve impulses towards the cell body. A
single long axon carries the nerve impulse away from the cell body. The axon is only 10µm in diameter
but can be up to 4m in length in a large animal (a piece of spaghetti the same shape would be 400m
long)! Most neurones have many companion cells called Schwann cells, which wrap their cell membrane
around the axon many times in a spiral to form a thick insulating lipid layer called the myelin sheath.
Nerve impulse can be passed from the axon of one neurone to the dendron of another at a synapse.
A nerve is a discrete bundle of several thousand neurone axons.
There are several differences between axons and dendrites:
10. Axons Dendrites
Take information away from the cell body
Smooth Surface
Generally only 1 axon per cell
No ribosomes
Can have myelin
Branch further from the cell body
Bring information to the cell body
Rough Surface (dendritic spines)
Usually many dendrites per cell
Have ribosomes
No myelin insulation
Branch near the cell body
Neurons are similar to other cells in the body because:
1. Neurons are surrounded by a cell membrane.
2. Neurons have a nucleus that contains genes.
3. Neurons contain cytoplasm, mitochondria and other organelles.
4. Neurons carry out basic cellular processes such as protein
synthesis and energy production.
Neurons differ from other cells in the body because:
1. Neurons have specialised extensions called dendrites and
axons. Dendrites bring information to the cell body and axons
take information away from the cell body.
2. Neurons communicate with each other through an
electrochemical process.
3. Neurons contain some specialized structures (for example,
synapses) and chemicals (for example, neurotransmitters).
11. The Reflex Arc
The three types of neurones are arranged in circuits and networks, the simplest of which is the reflex arc.
In a simple reflex arc, such as the knee jerk, a stimulus is detected by a receptor cell, which synapses
with a sensory neurone. The sensory neurone carries the impulse from site of the stimulus to the central
nervous system (the brain or spinal cord), where it synapses with an interneurone. The interneurone
synapses with a motor neurone, which carries the nerve impulse out to an effector, such as a muscle,
which responds by contracting.
Reflex arc can also be represented by a simple flow diagram:
12. The Resting Membrane Potential
When a neurone is not sending a signal, it is at ‘rest’. The membrane is responsible for the different
events that occur in a neurone. All animal cell membranes contain a protein pump called the sodium-
potassium pump (Na+K+ATPase). This uses the energy from ATP splitting to simultaneously pump 3
sodium ions out of the cell and 2 potassium ions in.
The Sodium-Potassium Pump (Na+K+ATPase)
(Provided by: Doc Kaiser's Microbiology Website)
Three sodium ions from inside the cell first bind to the
transport protein. Then a phosphate group is
transferred from ATP to the transport protein causing
it to change shape and release the sodium ions
outside the cell. Two potassium ions from outside the
cell then bind to the transport protein and as the
phospate is removed, the protein assumes its original
shape and releases the potassium ions inside the cell.
If the pump was to continue unchecked there would be no sodium or potassium ions left to pump, but
there are also sodium and potassium ion channels in the membrane. These channels are normally
closed, but even when closed, they “leak”, allowing sodium ions to leak in and potassium ions to leak out,
down their respective concentration gradients.
13. Concentration of ions inside and outside the neurone at rest:
Ion
Concentration inside
cell/mmol dm-3
Concentration
outside cell/mmol
dm-3
Why don’t the ions move down their concentration
gradient?
K+ 150.0 2.5 K+ ions do not move out of the neurone down their
concentration gradient due to a build up of positive charges
outside the membrane. This repels the movement of any more
K+ ions out of the cell.Na+ 15.0 145.0
Cl- 9.0 101.0
The chloride ions do not move into the cytoplasm as the
negatively charged protein molecules that cannot cross the
surface membrane repel them.
The combination of the Na+K+ATPase pump and the leak channels cause a stable imbalance of Na+ and
K+ ions across the membrane. This imbalance of ions causes a potential difference (or voltage) between
the inside of the neurone and its surroundings, called the resting membrane potential. The membrane
potential is always negative inside the cell, and varies in size from –20 to –200 mV (milivolt) in different
cells and species (in humans it is –70mV). The Na+K+ATPase is thought to have evolved as an
osmoregulator to keep the internal water potential high and so stop water entering animal cells and
bursting them. Plant cells don’t need this as they have strong cells walls to prevent bursting.
The Resting Membrane Potential is always negative (-70mV)
K+ pass easily into the cell
Cl- and Na+ have a more difficult time crossing
Negatively charged protein molecules inside the neurone cannot pass the membrane
The Na+K+ATPase pump uses energy to move 3Na+ out for every 2K+ into neuron
The imbalance in voltage causes a potential difference across the cell membrane - called the
resting potential
14. The Action Potential
The resting potential tells us about what happens when a neurone is at rest. An action potential occurs
when a neurone sends information down an axon. This involves an explosion of electrical activity, where
the nerve and muscle cells resting membrane potential changes.
In nerve and muscle cells the membranes are electrically excitable, which means they can change their
membrane potential, and this is the basis of the nerve impulse. The sodium and potassium channels in
these cells are voltage-gated, which means that they can open and close depending on the voltage
across the membrane.
The normal membrane potential inside the axon of nerve cells is –70mV, and since this potential can
change in nerve cells it is called the resting potential. When a stimulus is applied a brief reversal of the
membrane potential, lasting about a millisecond, occurs. This brief reversal is called the action potential:
An action potential has 2 main phases called depolarisation and repolarisation:
At rest, the inside of the neuron is slightly negative due to a
higher concentration of positively charged sodium ions outside
the neuron.
When stimulated past threshold (about –30mV in humans),
sodium channels open and sodium rushes into the axon, causing
a region of positive charge within the axon. This is
calleddepolarisation
15. The region of positive charge causes nearby voltage gated
sodium channels to close. Just after the sodium channels close,
the potassium channels open wide, and potassium exits the
axon, so the charge across the membrane is brought back to its
resting potential. This is called repolarisation.
This process continues as a chain-reaction along the axon. The
influx of sodium depolarises the axon, and the outflow of
potassium repolarises the axon.
The sodium/potassium pump restores the resting concentrations
of sodium and potassium ions
(provided by: Markham)
16. Action Potential has two main phases:
Depolarisation. A stimulus can cause the membrane potential to
change a little. The voltage-gated ion channels can detect this
change, and when the potential reaches –30mV the sodium
channels open for 0.5ms. The causes sodium ions to rush in,
making the inside of the cell more positive. This phase is referred
to as a depolarisation since the normal voltage polarity (negative
inside) is reversed (becomes positive inside).
17. Repolarisation. At a certain point, the depolarisation of the
membrane causes the sodium channels to close. As a result the
potassium channels open for 0.5ms, causing potassium ions to
rush out, making the inside more negative again. Since this
restores the original polarity, it is called repolarisation. As the
polarity becomes restored, there is a slight ‘overshoot’ in the
movement of potassium ions (called hyperpolarisation). The
resting membrane potential is restored by the Na+K+ATPase
pump.
How do Nerve Impulses Start?
We and other animals have several types of receptors of mechanical stimuli. Each initiates nerve
impulses in sensory neurons when it is physically deformed by an outside force such as:
touch
pressure
stretching
sound waves
motion
Mechanoreceptors enable us to
detect touch
monitor the position of our muscles, bones, and joints - the sense of proprioception
detect sounds and the motion of the body.
E.g. Touch
Light touch is detected by receptors in the skin. These are often found close to a hair follicle so even if the
skin is not touched directly, movement of the hair is detected.
In the mouse, light movement of hair triggers a generator potential in mechanically-gated sodium
channels in a neuron located next to the hair follicle. This potential opens voltage-gated sodium
channels and if it reaches threshold, triggers an action potential in the neuron.
Touch receptors are not distributed evenly over the body. The fingertips and tongue may have as many
as 100 per cm2; the back of the hand fewer than 10 per cm2. This can be demonstrated with thetwo-
point threshold test. With a pair of dividers like those used in mechanical drawing, determine (in a
18. blindfolded subject) the minimum separation of the points that produces two separate touch sensations.
The ability to discriminate the two points is far better on the fingertips than on, say, the small of the back.
The density of touch receptors is also reflected in the amount of somatosensory cortex in the brain
assigned to that region of the body.
Proprioception
Proprioception is our "body sense".
It enables us to unconsciously monitor the position of our body.
It depends on receptors in the muscles, tendons, and joints.
If you have ever tried to walk after one of your legs has "gone to sleep", you will have some
appreciation of how difficult coordinated muscular activity would be without proprioception.
An action occurs due to an increase in membrane permeability to Na+
An action potential is initiated by receptor cells that cause sodium channels to open
An action potential can only occur if the depolarisation of the membrane reaches the threshold
point. This is the all or nothing law.
How are Nerve Impulses Propagated?
Once an action potential has started it is moved (propagated) along an axon automatically. The local
reversal of the membrane potential is detected by the surrounding voltage-gated ion channels, which
open when the potential changes enough.
19. The ion channels have two other features that help the nerve impulse work effectively:
20. For an action
potential to
begin, then the
depolarisation
of the neurone
must reach the
threshold value,
i.e. the all or
nothing law.
After an ion
channel has
opened, it
needs a “rest
period” before it
can open again.
This is called
therefractory
period, and
lasts about
2 ms. This
means that,
although the
action potential
affects all other
ion channels
nearby, the upstream ion channels cannot open again since they are in their refractory period, so
only the downstream channels open, causing the action potential to move one-way along the
axon.
The refractory period is necessary as it allows the proteins of voltage sensitive ion channels to restore to
their original polarity.
The absolute refractory period = during the action potential, a second stimulus will not cause a
new action potential.
Exception: There is an interval in which a second action potential can be produced but only if the
stimulus is considerably greater than the threshold = relative refractory period
21. The refractory period can limit the number o faction potentials in a given time.
Average = about 100 action potentials per second.
Nerve Impulses travel in one direction
This is due to the refractory period i.e. Na+ channels are open or recovering.
The refractory period allows the voltage sensitive ion channels to restore their original polarity
o Absolute refractory period - Na+ channels are open or recovering
o Relative refractory period - Occurs when the membrane is hyperpolarised (-80mV),
where the K+ channels are open. Action potentials are more difficult to generate during
this period relative to resting potential (-70mV)
22. How Fast are Nerve Impulses?
Action potentials can travel along axons at speeds of 0.1-100 m/s. This means that nerve impulses can
get from one part of a body to another in a few milliseconds, which allows for fast responses to stimuli.
(Impulses are much slower than electrical currents in wires, which travel at close to the speed of light,
3x108 m/s.) The speed is affected by 3 factors:
Temperature - The higher the temperature, the faster the speed. So homoeothermic (warm-
blooded) animals have faster responses than poikilothermic (cold-blooded) ones.
Axon diameter - The larger the diameter, the faster the speed. So marine invertebrates, who live
at temperatures close to 0°C, have developed thick axons to speed up their responses. This
explains why squid have their giant axons.
Myelin sheath - Only vertebrates have a myelin sheath surrounding their neurones. The voltage-
gated ion channels are found only at the nodes of Ranvier, and between the nodes the myelin
sheath acts as a good electrical insulator. The action potential can therefore jump large distances
from node to node (1mm), a process that is called saltatory propagation. This increases the
speed of propagation dramatically, so while nerve impulses in unmyelinated neurones have a
maximum speed of around 1 m/s, in myelinated neurones they travel at 100 m/s.