IB BIOLOGY 6.5.5 Explain how a nerve impulse passes along a non-myelinated neuron
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In a non-myelinated neuron, an action potential is triggered when a stimulus opens voltage-gated sodium channels, causing sodium ions to diffuse into the neuron and depolarize the membrane. This depolarization then triggers adjacent areas of the neuron to open their sodium channels, creating a domino effect that propagates the action potential along the axon. After transmission, potassium channels open, allowing potassium ions to flow out and repolarize the membrane, restoring the resting potential between activations.
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6.5 neurons and synapses
Neurons transmit electrical signals along their axons through the propagation of action potentials. An action potential is triggered when the membrane potential of the neuron reaches its threshold. This causes voltage-gated sodium channels to open, allowing sodium ions to rush into the neuron and depolarize the membrane. The membrane then repolarizes as voltage-gated potassium channels open and sodium channels close, restoring the ion gradients. This process repeats as the action potential travels down the axon. Some axons are wrapped in myelin sheaths which allow saltatory conduction, speeding up signal propagation.
Action potential
It is over 60 years since Hodgkin and
Huxley1 made the first direct recording of
the electrical changes across the neuronal
membrane that mediate the action
potential. Using an electrode placed inside a
squid giant axon they were able to measure a
transmembrane potential of around 260 mV
inside relative to outside, under resting
conditions (this is called the resting membrane
potential). The action potential is a
transient (,1 millisecond) reversal in the
polarity of this transmembrane potential
which then moves from its point of initiation,
down the axon, to the axon terminals. In a
subsequent series of elegant experiments
Hodgkin and Huxley, along with Bernard
Katz, discovered that the action potential
results from transient changes in the permeability
of the axon membrane to sodium (Na+)
and potassium (K+) ions. Importantly, Na+ and
K+ cross the membrane through independent
pathways that open in response to a change
in membrane potential.
As testimony to their pioneering work, the
fundamental mechanisms described by
Hodgkin, Huxley and Katz remain applicable
to all excitable cells today. Indeed, the
predictions they made about the molecular
mechanisms that might underlie the changes
in membrane permeability showed remarkable
foresight. The molecular basis of the action
potential lies in the presence of proteins
called ion channels that form the permeation
pathways across the neuronal membrane.
Although the first electrophysiological
recordings from individual ion channels were
not made until the mid 1970s,2 Hodgkin and
Huxley predicted many of the properties now
known to be key components of their
function: ion selectivity, the electrical basis
of voltage-sensitivity and, importantly, a
mechanism for quickly closing down the
permeability pathways to ensure that the
action potential only moves along the axon in
one direction.
Resting membrane potential and action potential
The document discusses the resting membrane potential and action potential in neurons. It explains that:
1) The resting membrane potential is around -70mV, created by different ion concentrations inside and outside the neuron.
2) Graded potentials are local, short-lived changes in membrane potential caused by ion channels opening briefly in response to stimuli.
3) Action potentials are brief, large changes in potential from -70mV to +30mV caused by voltage-gated sodium and potassium channels. The influx of sodium ions depolarizes the membrane before potassium channels repolarize it.
4) Action potentials propagate along the axon as one area repolarizes and depolarizes the next, allowing nerve
Conduction of action potential
Conduction of action potential through neurons which is a basic phenomena of transmission of information through the neurons within the human brain.
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Large food molecules need to be broken down through digestion to allow for absorption and assimilation of nutrients. Digestion is made possible by enzymes, which are protein catalysts that break down substrates into products. The three main enzymes involved in digestion are amylase, protease, and lipase. Amylase breaks down starches into sugars in the small intestine, protease breaks down proteins into amino acids, and lipase breaks down fats into fatty acids and glycerol. The digestive system includes the mouth, esophagus, stomach, small intestine, and large intestine, each playing an important role in the multi-step process of breaking down food and absorbing nutrients.
Action potential by Hamidul Kowsar
An action potential is a rapid change in the electrical potential of a nerve or muscle cell membrane in response to stimulation. It allows electrical impulses to travel across the cell membrane. There are six stages of an action potential: 1) Resting stage with a large negative potential, 2) Depolarization from sodium ion influx, 3) Repolarization by potassium ion efflux, 4) A spike potential from the sharp depolarization and repolarization waves, 5) A negative after potential where the potential does not fully return to resting, and 6) Sometimes hyperpolarization where the potential becomes more negative than resting due to excess potassium permeability.
Action potential of heart
Cardiac muscle contraction occurs when an action potential travels through the conduction system and excites the contractile fibers of the atria and ventricles. During depolarization, the opening of voltage-gated sodium channels allows sodium ions to enter the fiber, rapidly depolarizing the membrane. The plateau phase is maintained by calcium entry through slow calcium channels, which triggers calcium-induced calcium release from the sarcoplasmic reticulum and contraction. Repolarization occurs when various potassium channels open, restoring the negative resting potential as calcium channels close.
Nerve Impulse
1) Nerve impulses propagate along axons via the movement of sodium and potassium ions across the axon membrane.
2) At rest, the axon maintains a negative charge due to higher concentrations of potassium and organic ions inside the axon and higher concentrations of sodium and chloride ions outside.
3) When an impulse is generated, the permeability of the axon membrane to sodium briefly increases, allowing sodium to flow inside and depolarize the membrane. This creates an electrical signal called an action potential.
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6.5 neurons and synapses
Neurons transmit electrical signals along their axons through the propagation of action potentials. An action potential is triggered when the membrane potential of the neuron reaches its threshold. This causes voltage-gated sodium channels to open, allowing sodium ions to rush into the neuron and depolarize the membrane. The membrane then repolarizes as voltage-gated potassium channels open and sodium channels close, restoring the ion gradients. This process repeats as the action potential travels down the axon. Some axons are wrapped in myelin sheaths which allow saltatory conduction, speeding up signal propagation.
Action potential
It is over 60 years since Hodgkin and
Huxley1 made the first direct recording of
the electrical changes across the neuronal
membrane that mediate the action
potential. Using an electrode placed inside a
squid giant axon they were able to measure a
transmembrane potential of around 260 mV
inside relative to outside, under resting
conditions (this is called the resting membrane
potential). The action potential is a
transient (,1 millisecond) reversal in the
polarity of this transmembrane potential
which then moves from its point of initiation,
down the axon, to the axon terminals. In a
subsequent series of elegant experiments
Hodgkin and Huxley, along with Bernard
Katz, discovered that the action potential
results from transient changes in the permeability
of the axon membrane to sodium (Na+)
and potassium (K+) ions. Importantly, Na+ and
K+ cross the membrane through independent
pathways that open in response to a change
in membrane potential.
As testimony to their pioneering work, the
fundamental mechanisms described by
Hodgkin, Huxley and Katz remain applicable
to all excitable cells today. Indeed, the
predictions they made about the molecular
mechanisms that might underlie the changes
in membrane permeability showed remarkable
foresight. The molecular basis of the action
potential lies in the presence of proteins
called ion channels that form the permeation
pathways across the neuronal membrane.
Although the first electrophysiological
recordings from individual ion channels were
not made until the mid 1970s,2 Hodgkin and
Huxley predicted many of the properties now
known to be key components of their
function: ion selectivity, the electrical basis
of voltage-sensitivity and, importantly, a
mechanism for quickly closing down the
permeability pathways to ensure that the
action potential only moves along the axon in
one direction.
Resting membrane potential and action potential
The document discusses the resting membrane potential and action potential in neurons. It explains that:
1) The resting membrane potential is around -70mV, created by different ion concentrations inside and outside the neuron.
2) Graded potentials are local, short-lived changes in membrane potential caused by ion channels opening briefly in response to stimuli.
3) Action potentials are brief, large changes in potential from -70mV to +30mV caused by voltage-gated sodium and potassium channels. The influx of sodium ions depolarizes the membrane before potassium channels repolarize it.
4) Action potentials propagate along the axon as one area repolarizes and depolarizes the next, allowing nerve
Conduction of action potential
Conduction of action potential through neurons which is a basic phenomena of transmission of information through the neurons within the human brain.
Digestion (core)
Large food molecules need to be broken down through digestion to allow for absorption and assimilation of nutrients. Digestion is made possible by enzymes, which are protein catalysts that break down substrates into products. The three main enzymes involved in digestion are amylase, protease, and lipase. Amylase breaks down starches into sugars in the small intestine, protease breaks down proteins into amino acids, and lipase breaks down fats into fatty acids and glycerol. The digestive system includes the mouth, esophagus, stomach, small intestine, and large intestine, each playing an important role in the multi-step process of breaking down food and absorbing nutrients.
Action potential by Hamidul Kowsar
An action potential is a rapid change in the electrical potential of a nerve or muscle cell membrane in response to stimulation. It allows electrical impulses to travel across the cell membrane. There are six stages of an action potential: 1) Resting stage with a large negative potential, 2) Depolarization from sodium ion influx, 3) Repolarization by potassium ion efflux, 4) A spike potential from the sharp depolarization and repolarization waves, 5) A negative after potential where the potential does not fully return to resting, and 6) Sometimes hyperpolarization where the potential becomes more negative than resting due to excess potassium permeability.
Action potential of heart
Cardiac muscle contraction occurs when an action potential travels through the conduction system and excites the contractile fibers of the atria and ventricles. During depolarization, the opening of voltage-gated sodium channels allows sodium ions to enter the fiber, rapidly depolarizing the membrane. The plateau phase is maintained by calcium entry through slow calcium channels, which triggers calcium-induced calcium release from the sarcoplasmic reticulum and contraction. Repolarization occurs when various potassium channels open, restoring the negative resting potential as calcium channels close.
Nerve Impulse
1) Nerve impulses propagate along axons via the movement of sodium and potassium ions across the axon membrane.
2) At rest, the axon maintains a negative charge due to higher concentrations of potassium and organic ions inside the axon and higher concentrations of sodium and chloride ions outside.
3) When an impulse is generated, the permeability of the axon membrane to sodium briefly increases, allowing sodium to flow inside and depolarize the membrane. This creates an electrical signal called an action potential.
action potential presentation
This document provides an overview of action potentials. It defines an action potential as a change in electrical potential associated with the passage of an impulse along a muscle or nerve cell membrane. It describes how action potentials are generated by voltage-gated ion channels in the cell membrane that allow ions like sodium and potassium to flow in and out. The stages of an action potential are then outlined, including resting, depolarization, repolarization, and afterpotential stages. Examples of action potentials in neurons transmitting signals along nerves to muscles are also provided.
Nerve impulse synapses
The nerve impulse is an electrical signal transmitted by neurons in the nervous system. It occurs when voltage-gated sodium channels in the neuron's membrane open, allowing sodium ions to flow into the neuron and depolarize it. This then causes voltage-gated potassium channels to open, allowing potassium ions to flow out and repolarize the neuron, restoring the resting potential. The nerve impulse travels rapidly along the axon via this process of local depolarization and repolarization. At synapses, neurotransmitters are released by the presynaptic neuron, which can either excite or inhibit the postsynaptic neuron, determining whether or not an impulse continues along the nerve circuit.
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1. An action potential, or nerve impulse, occurs when a neuron reaches its threshold level and is stimulated to send a message along its axon.
2. The action potential involves two steps - depolarization, where sodium ions rush into the neuron, reversing the charge; and repolarization, where potassium ions rush out, restoring the charge.
3. After repolarization, the sodium-potassium pump restores the ion concentrations to prepare the neuron to fire again if stimulated. Myelin insulation allows the impulse to jump from node to node, speeding up conduction.
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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.
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The document presents information on the transmission of nerve impulses through neurons and synapses. It discusses how the nervous system is divided into the central and peripheral nervous systems. It describes how neurons transmit electrical signals called nerve impulses through changes in their membrane potentials. When a neuron is stimulated, sodium ions enter the neuron during depolarization, reversing the potential and triggering further sodium and potassium ion exchanges that allow the impulse to travel down the neuron. At synapses, neurotransmitters released by the presynaptic neuron can trigger signals in the postsynaptic neuron across the narrow synaptic cleft.
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- The all-or-none principle states that an action potential will only be generated if the threshold is reached. Speed and propagation depends on myelination.
- Different cell types like cardiac and smooth muscles exhibit variations in their action potential waveforms.
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1. An action potential, or nerve impulse, occurs when a neuron reaches its threshold level and is stimulated to send a message along its axon.
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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.
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The document presents information on the transmission of nerve impulses through neurons and synapses. It discusses how the nervous system is divided into the central and peripheral nervous systems. It describes how neurons transmit electrical signals called nerve impulses through changes in their membrane potentials. When a neuron is stimulated, sodium ions enter the neuron during depolarization, reversing the potential and triggering further sodium and potassium ion exchanges that allow the impulse to travel down the neuron. At synapses, neurotransmitters released by the presynaptic neuron can trigger signals in the postsynaptic neuron across the narrow synaptic cleft.
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- An action potential is initiated when the membrane reaches its threshold potential due to sodium influx. It involves stages of depolarization, repolarization and refractory periods.
- The all-or-none principle states that an action potential will only be generated if the threshold is reached. Speed and propagation depends on myelination.
- Different cell types like cardiac and smooth muscles exhibit variations in their action potential waveforms.
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The document discusses the resting potential, graded potential, and action potential in neurons. It provides details on:
1) The resting potential of neurons is normally between -60 to -80 mV due to concentrations of potassium and sodium ions inside and outside the cell. The sodium-potassium pump helps maintain this gradient.
2) A graded potential is an intermediate voltage change before an action potential. It involves the opening of voltage-gated potassium and sodium ion channels, making the intracellular voltage more negative or less negative.
3) An action potential is a brief, all-or-nothing increase in voltage caused by the rapid influx of sodium ions through opened voltage-gated channels, followed by the efflux
Excitable t is issues.pptx
- Nerve and muscle cells are excitable tissues that respond to stimuli through generation of electrical impulses.
- Nerve cells called neurons transmit signals through electrical impulses called action potentials. Action potentials are generated when the membrane potential rapidly changes from resting potential to threshold potential.
- At chemical synapses, an action potential causes release of neurotransmitters which may excite or inhibit the next neuron. Summation of multiple synaptic signals can trigger action potentials in post-synaptic neurons.
Electrodiagnosis.pptx
This document summarizes the generation and propagation of action potentials in neurons. It discusses:
- The resting membrane potential is maintained by selective permeability to potassium ions.
- Action potentials are initiated by the opening of voltage-gated sodium channels, causing rapid depolarization. If the threshold is reached, an action potential fires.
- After firing, potassium channels open to repolarize the membrane back to the resting potential. Some axons are myelinated to promote faster signal conduction via saltatory propagation between nodes of Ranvier.
Y1 s1 membrane potentials
Excitable tissues like neurons and muscles have a resting membrane potential of -70mV due to ion gradients established by pumps and permeability. An action potential occurs when the membrane reaches a threshold for opening voltage-gated sodium channels, causing rapid depolarization to +30mV then repolarization as potassium channels open. This propagates along membranes to transmit signals. The sodium-potassium pump restores ion gradients for the next action potential.
Cell membrane potential.pdf
The document discusses cell membrane potential and action potentials. It explains that cell membranes maintain a voltage gradient called the membrane potential due to different ion concentrations inside and outside the cell. Ion channels, including passive, chemically-gated, and voltage-gated channels, control the flow of ions across the membrane and influence the membrane potential. An action potential occurs when the membrane potential rapidly changes from its normal resting potential of -70mV to +30mV before repolarizing back. This wave of depolarization propagates along the membrane via opening and closing of sodium and potassium ion channels.
Nerve action potential
The document discusses nerve action potentials and myelination. It describes how myelin is produced in the periphery and central nervous system and how it speeds up signal transmission along axons via saltatory conduction. Unmyelinated gaps called nodes of Ranvier allow signals to jump between myelinated segments. Myelinated bundles form white matter, while gray matter contains cell bodies. Neurons communicate via electrical signals called action potentials, which are based on ion movements across the axon membrane. The document outlines the stages of the action potential and how voltage-gated sodium and potassium channels are involved in depolarization and repolarization.
physiology of a neuron(1).pptx
The document summarizes the physiology of neurons and how nerve impulses are generated and propagated. It discusses how ions like sodium and potassium contribute to the resting membrane potential and how an action potential is initiated. When a neuron is stimulated enough to reach threshold, sodium channels open causing depolarization as sodium ions rush in. Then potassium channels open leading to repolarization as potassium ions rush out, restoring the resting potential. The document also describes the differences between continuous and saltatory conduction in unmyelinated and myelinated neurons respectively.
Physiology com3-week2
The document discusses membrane potential and action potentials. It begins by defining action potentials as signals that trigger communication between cells through electrical and chemical signaling. It then discusses:
- Excitable cells like neurons, muscle and endocrine cells that are able to generate and conduct action potentials.
- The resting membrane potential of -70mV that exists due to ion concentration gradients established by the sodium-potassium pump and selective permeability of the membrane.
- How action potentials are initiated when the membrane potential rapidly depolarizes past a threshold due to opening of voltage-gated sodium channels, then repolarizes due to opening of voltage-gated potassium channels.
Y1 s1 membrane potentials 2013
This document discusses excitable tissues and their resting membrane potential and action potentials. It begins by defining excitable tissues as those capable of generating and transmitting electrochemical impulses along their membranes, such as nerves and muscles. It then explains that excitable tissues maintain a more negative resting membrane potential than non-excitable tissues due to ion distributions and gradients established by ion pumps and channels. When an excitable cell is stimulated past its threshold, voltage-gated sodium channels open, allowing sodium to rush in and depolarize the membrane. This triggers voltage-gated potassium channels to then repolarize the membrane, before the sodium-potassium pump restores ion gradients. This process propagates as an action potential along the
6.5 Neurons and synapses
Neurons transmit electrical signals along their axons via action potentials. At synapses, neurotransmitters carry signals between neurons. When an action potential reaches a presynaptic neuron, calcium ions enter and cause neurotransmitter vesicles to fuse and release their contents. Neurotransmitters diffuse across the synapse and bind to receptors, sometimes triggering an action potential in the postsynaptic neuron. Myelination allows saltatory conduction to increase signal propagation speed along axons.
Ch 11b
This document summarizes key concepts about neuron function and membrane potentials. It explains that neurons generate action potentials in response to stimuli and propagate signals along their axons. The membrane potential is maintained by ion gradients established by ion channels and pumps. Opening of voltage-gated sodium channels causes rapid depolarization during an action potential, while voltage-gated potassium channels cause repolarization. Myelination increases conduction velocity. Diseases like multiple sclerosis disrupt myelin and slow nerve impulses.
Ch 11b
This document summarizes key concepts about neuron function and membrane potentials. It explains that neurons generate action potentials in response to stimuli and transmit signals along their axons. The membrane potential is maintained by ion gradients established by ion channels and pumps. Depolarization occurs when stimuli open ion channels, altering the membrane potential. A large enough depolarization will trigger an action potential, which propagates by opening voltage-gated sodium channels. The refractory period prevents repeated firing to ensure proper signal transmission. Myelination increases conduction velocity. Diseases like multiple sclerosis disrupt myelin and slow nerve impulses.
PPt action potential.pptx
- An action potential is a brief change in the membrane potential of an excitable cell, such as a neuron, that occurs when the membrane potential rapidly rises and falls.
- The phases of an action potential include the resting stage, depolarization, repolarization, and hyperpolarization. Depolarization is caused by an influx of sodium ions, repolarization by an efflux of potassium ions.
- For an action potential to occur, the membrane potential must reach the threshold potential, around -55 mV. Once initiated, the action potential propagates along the cell membrane via voltage-gated ion channels.
Nerve Action Potential (1).pptx
1. An action potential is a brief change in the membrane potential of a muscle or nerve cell triggered by the stimulation of voltage-gated ion channels.
2. During an action potential, sodium channels open allowing sodium ions to enter the cell, causing rapid depolarization. Then, potassium channels open and sodium channels close, repolarizing the membrane back to its resting potential.
3. The stages of an action potential are resting, depolarization, and repolarization. After an action potential occurs, the cell enters an absolute refractory period where it cannot generate another action potential, followed by a relative refractory period.
Electrophysiology of The Heart(1) (1)..pdf
The heart contracts rhythmically due to electrical impulses generated by specialized pacemaker cells. There are two types of cardiac muscle cells: contractile cells that pump blood and pacemaker cells that initiate and conduct electrical impulses. The impulse conducting system consists of the sinoatrial node, atrioventricular node, bundle of His, and Purkinje fibers. An action potential occurs when the membrane potential changes from resting potential (-90 mV) to depolarized (0 mV) and back again due to the movement of ions through membrane channels. Pacemaker cells spontaneously depolarize to initiate each heartbeat.
Neuronal conduction.pptx
Neural signals are transmitted through both electrical and chemical means. An electrical signal travels down a neuron's dendrites to its cell body. If the signal reaches the axon hillock's threshold, the axon is activated and fires, transmitting an electrical signal down the axon. At the axon terminals, neurotransmitters are released across the synaptic cleft to the next cell. The membrane potential, maintained by ion concentration gradients and sodium-potassium pumps, underlies the neuron's resting potential. When neurotransmitters bind to receptors on the post-synaptic cell, they generate graded excitatory or inhibitory post-synaptic potentials that are integrated and can trigger an all-or-none action potential for signal transmission along the ax
Nervous coordination
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.
Nerve and Muscle 1.pdf
1. Nerve and muscle cells are excitable tissues that can generate electrochemical impulses. In nerves, these impulses propagate signals along the axon when stimulated, whereas in muscles they cause contraction.
2. The resting membrane potential of these cells is maintained by ion concentration gradients and selective permeability of the membrane to ions like sodium, potassium, and chloride. At rest, the intracellular fluid is negatively charged relative to the extracellular fluid.
3. An action potential occurs when the membrane potential rapidly changes from the resting potential to a positive overshoot then back again. This is driven by changes in sodium and potassium conductance across the membrane.
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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
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2. Satheesh Gopi, Basic Civil Engineering, Pearson Publishers.
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IB BIOLOGY 6.5.5 Explain how a nerve impulse passes along a non-myelinated neuron
- 1. 6.5.5 Explain how a nerve impulse passes along a non-myelinated neuron
- 2. NERVE IMPULSE • An electrical current which carry information that travels along dendrites and axons of a neuron
- 3. NON-MYELINATED NEURON • Neuron without myelin sheath
- 5. RESTING POTENTIAL • The potential difference across a nerve cell membrane when it is not stimulated. (-70mV) • A nerve impulse is an electrical current that travels along dendrites or axons due to ions moving through voltage-gated channels in the neuron’s plasma membrane. • The voltage-gated channels are the sodium and potassium channels, which means that they can open and close depending on the voltage across the membrane.
- 6. • When the neuron is not sending an impulse, the charge difference is maintained inside and outside of the axon cell. This is called the resting potential where it is polarized.
- 7. • The resting potential is due to the active transport of Na+ ions and K + ions through sodium-potassium pumps. • The pumps sends Na+ ions out of the axon cell and brings K + ions in. • There are negatively charged ions (Cl-) located permanently in the cytoplasm of the axon. This leads to the net positive charge outside the axon membrane and a net negative charge inside the axon membrane.
- 9. ACTION POTENTIAL • The potential difference produced across the plasma membrane of nerve cell when it is stimulated. • Due to the diffusion of ions from outside the axon to the inside and from the inside of axon to the outside.
- 10. • Action potential is triggered by a stimulus received at a receptor or sensitive nerve ending causes a sodium channel to open. • The Na+ ions which is actively transported out diffused into the membrane. This causes the local region inside the membrane to have net positive charge while the outside having net negative charge. • The membrane is said to be “depolarized”. The resting potential is reversed from -70mV to +40mV. ~
- 11. • This area of axon then initiates the next area of the axon to open up the other sodium channels. (Domino effect) • Therefore, the moving depolarization is called an action potential. • After a short while, the sodium channels closed, and the potassium channels are opened.
- 12. • This causes the rapid flow of K + ions out of the membrane and thus, “repolarizing” the membrane. • So, the inside is again negatively charged and the outside is positively charged. • The resting potential of the membrane is restored.