The document summarizes different sensory receptors in the human body. It describes several types of receptors for touch including free nerve endings, root hair plexuses, Merkel disks, Meissner corpuscles and Pacinian corpuscles. It also discusses muscle spindles and Golgi tendon organs. The document then summarizes receptors related to smell including olfactory receptors and bulbs. It compares human and canine olfaction and describes the neural pathways involved in smell. Finally, it briefly discusses taste buds and their role in taste perception.
The document discusses the anatomy and physiology of several human sensory systems. It provides details on:
1) The main sensory receptors in the skin including free nerve endings, Meissner's corpuscles, Pacinian corpuscles, and others.
2) The olfactory system including olfactory receptor cells in the nose and the pathways to the olfactory bulb and brain.
3) Gustation including the taste buds on the tongue and soft palate connected to facial and glossopharyngeal nerves.
4) The auditory system from the pinna collecting sounds to the cochlea and auditory nerve pathways to the brainstem and cortex.
5) The vestibular system including the
The document summarizes the key aspects of olfaction and the sense of smell. It describes the main parts of the olfactory system including the olfactory bulb, mitral cells, bone, nasal epithelium, glomerulus, and olfactory receptor neurons. It notes that dogs have a much stronger sense of smell than humans, with 300-10,000 times more olfactory receptor neurons. The document also discusses how smells can enhance our experiences and memories, and how loss of smell (anosmia) affects one's ability to experience flavors.
Three distinct patterns of olfactory bulb maturation were identified on MRI:
1) In infants under 6 months, bulbs were round with a dark outer rim and bright central area.
2) Between 6 months and 2 years, bulbs became U-shaped with thinning tops and maintained bright centers.
3) After 2 years, bulbs were small and round or J-shaped with uniform signal intensity, resembling the adult form.
Maturation was complete by 2 years when signal patterns matched cerebral white matter, paralleling brain development.
Olfaction, or the sense of smell, occurs when odorant molecules bind to olfactory receptors in the nasal cavity. Humans have two olfactory systems - the main olfactory system detects airborne chemicals, while the accessory olfactory system detects pheromones. Evolution has led to changes in vertebrate olfaction, including the development of nasal turbinates in mammals which increase surface area for smell. Diseases and disorders can impair olfaction through conductive issues like nasal obstruction or central issues like viral infection of olfactory neurons.
This document discusses sensory receptors and how they function during the Christmas holiday season. It provides examples of how sensory receptors detect stimuli like hunger cues from cookies left out for Santa, different moods conveyed through Christmas versus Halloween songs, and sensations like pain experienced by characters in Christmas movies. The document then explores the anatomy and physiology of various sensory receptors, including their location, structure, and role in senses like smell, taste, hearing, vision, balance and proprioception.
The document discusses the sense of smell (olfaction). It describes how odorants are detected by olfactory receptor neurons in the nasal cavity and signals are sent to brain structures like the olfactory bulb and limbic system. It notes that dogs have a much more sensitive sense of smell than humans, with more olfactory receptor neurons. The summary provides an overview of the key topics and structures involved in the sense of smell.
The olfactory nerve detects smells in the nasal cavity. Olfactory receptor neurons in the nasal mucosa detect smells and send signals along axons through the cribriform plate to the olfactory bulb. The olfactory bulb performs initial processing of smell signals before sending them to areas of the brain involved in emotion and smell perception like the amygdala, hippocampus, and orbitofrontal cortex.
The document discusses the anatomy and physiology of several human sensory systems. It provides details on:
1) The main sensory receptors in the skin including free nerve endings, Meissner's corpuscles, Pacinian corpuscles, and others.
2) The olfactory system including olfactory receptor cells in the nose and the pathways to the olfactory bulb and brain.
3) Gustation including the taste buds on the tongue and soft palate connected to facial and glossopharyngeal nerves.
4) The auditory system from the pinna collecting sounds to the cochlea and auditory nerve pathways to the brainstem and cortex.
5) The vestibular system including the
The document summarizes the key aspects of olfaction and the sense of smell. It describes the main parts of the olfactory system including the olfactory bulb, mitral cells, bone, nasal epithelium, glomerulus, and olfactory receptor neurons. It notes that dogs have a much stronger sense of smell than humans, with 300-10,000 times more olfactory receptor neurons. The document also discusses how smells can enhance our experiences and memories, and how loss of smell (anosmia) affects one's ability to experience flavors.
Three distinct patterns of olfactory bulb maturation were identified on MRI:
1) In infants under 6 months, bulbs were round with a dark outer rim and bright central area.
2) Between 6 months and 2 years, bulbs became U-shaped with thinning tops and maintained bright centers.
3) After 2 years, bulbs were small and round or J-shaped with uniform signal intensity, resembling the adult form.
Maturation was complete by 2 years when signal patterns matched cerebral white matter, paralleling brain development.
Olfaction, or the sense of smell, occurs when odorant molecules bind to olfactory receptors in the nasal cavity. Humans have two olfactory systems - the main olfactory system detects airborne chemicals, while the accessory olfactory system detects pheromones. Evolution has led to changes in vertebrate olfaction, including the development of nasal turbinates in mammals which increase surface area for smell. Diseases and disorders can impair olfaction through conductive issues like nasal obstruction or central issues like viral infection of olfactory neurons.
This document discusses sensory receptors and how they function during the Christmas holiday season. It provides examples of how sensory receptors detect stimuli like hunger cues from cookies left out for Santa, different moods conveyed through Christmas versus Halloween songs, and sensations like pain experienced by characters in Christmas movies. The document then explores the anatomy and physiology of various sensory receptors, including their location, structure, and role in senses like smell, taste, hearing, vision, balance and proprioception.
The document discusses the sense of smell (olfaction). It describes how odorants are detected by olfactory receptor neurons in the nasal cavity and signals are sent to brain structures like the olfactory bulb and limbic system. It notes that dogs have a much more sensitive sense of smell than humans, with more olfactory receptor neurons. The summary provides an overview of the key topics and structures involved in the sense of smell.
The olfactory nerve detects smells in the nasal cavity. Olfactory receptor neurons in the nasal mucosa detect smells and send signals along axons through the cribriform plate to the olfactory bulb. The olfactory bulb performs initial processing of smell signals before sending them to areas of the brain involved in emotion and smell perception like the amygdala, hippocampus, and orbitofrontal cortex.
This document provides an overview of the physiology of olfaction. It discusses:
- The anatomy of olfactory stimulation including the nasal passageways, olfactory mucus, and olfactory epithelium.
- The main cell types in the olfactory epithelium: ciliated olfactory receptors, microvillar cells, supporting cells, and basal cells.
- How odorant molecules stimulate the olfactory receptors and initiate the transduction pathway.
- The pathways that olfactory information takes from the olfactory epithelium to the olfactory bulb and onto various regions in the brain involved in olfaction.
- Theories on olfactory transduction and coding of odorant molecules.
-
Stereochemical theory of olfaction.docx 1Tanvir Nehal
The Stereochemical theory of olfaction states that a molecule's smell is due to its specific 3D structure fitting the "lock and key" mechanism of olfactory receptors in the nasal epithelium. Stereochemistry involves the study of the spatial arrangement of atoms that form molecular structures, including stereoisomers which have the same molecular formula and bonded atoms but differ in 3D orientation. The theory proposes that stereoisomers of volatile oil molecules will bind to different olfactory receptors and be detected as different smells, such as the stereoisomers of carvone smelling like mint versus caraway.
This document discusses the anatomy and physiology of four sensory systems - acoustic, vestibular, gustatory, and olfactory. It describes the receptor, conduction, and central processing components of each system. Key points include the roles of the cochlea, semicircular canals, taste buds, and olfactory epithelium as receptor sites, and how signals are transmitted by cranial nerves to processing centers in the brainstem and cortex. Theories of sound perception and mechanisms of smell detection are also summarized.
1. The sense of smell occurs in the olfactory epithelium located in the upper part of the nasal cavity. Olfactory sensory neurons here detect odorant molecules and transmit signals to the olfactory bulb.
2. When an odorant molecule binds to an olfactory receptor, it triggers a signal transduction pathway involving cAMP that leads to an action potential. This signal is transmitted via the olfactory nerve to the olfactory bulb.
3. The olfactory pathway projects from the olfactory bulb to areas involved in perception and emotion processing like the piriform cortex, amygdala and orbitofrontal cortex. Factors like concentration, adaptation and injury can influence olfactory function.
The document discusses the different types of sense organs in insects, including mechanoreceptors, auditory receptors, chemoreceptors, thermoreceptors, and photoreceptors. It provides examples of each type of sense organ and their functions, such as trichoid sensilla which detect touch, Johnston's organ which detects antennal movements, and compound eyes which allow insects to detect light, form, and color. The sensory organs help insects perform important functions like finding hosts, food, and mates as well as sensing their environment.
The document discusses olfactory receptors and compares the olfactory receptor gene OR4D11 between humans and chimpanzees. It finds that OR4D11 is a pseudogene in humans but intact in chimpanzees. It also summarizes the results of BLAST searches comparing the human and chimpanzee OR4D11 sequences and structures, finding them to be 96% similar. Phylogenetic analysis shows OR4D11 is conserved in other species like mice, dogs, and rats.
This document discusses the senses of smell (olfaction) and taste. It notes that smell and taste have a cooperative relationship, with odor contributing approximately 80% of what we perceive as flavor. The main points covered include:
- Smell and taste are classified as special senses along with sight, hearing, and balance
- The olfactory system includes receptors in the nose, olfactory bulbs, and pathways to the brain regions involved in emotion and behavior
- Pheromones influence behaviors through a vomeronasal system present in many animals
- Humans have a less developed sense of smell compared to most animals
- The olfactory epithelium regenerates sensory neurons throughout life but this capacity declines with age
The document provides an overview of the special senses of taste, hearing, smell, and vision. It includes the following key points:
- Taste is detected by taste buds on the tongue and involves four basic tastes: sweet, sour, salty, and bitter. Taste pathways transmit signals to the brainstem.
- Hearing involves the outer, middle and inner ear. Sound waves cause the eardrum and bones of the middle ear to vibrate, transmitting signals through nerves to the brain.
- Smell receptors in the nose detect odors which activate pathways to areas of the brain involved in memory and emotion.
- Vision involves light entering the eye through the cornea and lens, with
The document discusses chemoreceptors, which include taste receptors and olfactory receptors. Taste and smell rely on chemical receptors being stimulated by certain molecules. Humans can taste sweet, sour, bitter, salty, and umami; taste and smell are directly related because they use the same types of receptors. Olfactory receptors are located in the nose, while taste receptors are located in the tongue and oral cavity. Both system detect chemicals and transmit signals to the brain.
The document discusses abnormalities of smell and olfactory disorders. It describes the main components of the olfactory system and pathways. Several types of smell disorders are defined, including anosmia, hyposmia, dysosmia, and phantosmia. Causes of smell disturbances include upper respiratory infections, head trauma, nasal/sinus disease, tumours, and neurodegenerative diseases. Clinical evaluation involves a history, smell tests, and physical exam including the nose and sinuses. Treatment depends on whether the impairment is conductive or sensorineural.
1. Disorders of olfaction can be conductive, resulting from nasal obstruction, or sensorineural, due to damage to the olfactory neuroepithelium.
2. Common causes of sensorineural disorders include upper respiratory infections, head trauma, tumors near the olfactory region, congenital defects, toxins, age-related changes, and neurodegenerative diseases.
3. Specific conditions that can cause olfactory disorders are post-viral olfactory dysfunction, Kallmann syndrome, septo-optic dysplasia, holoprosencephaly, exposure to metals or other toxins, Alzheimer's disease, Parkinson's disease, and epilepsy presenting with olfactory auras.
Olfaction is very important for us and also for other animals.
Dog’s sense of smell is 1000 times more than humans. People use dog’s keen sense of smell in many ways---
Govt. agencies use specially trained dogs in search and rescue missio
Detection of narcotics.
Detection of forensic cadaver material.
Due to lack of smell the following disorders may be seen---
Anosmia : lack of ability to smell
Hyposmia- decreased ability to smell
Phantosmia- [“hallucinated smell”] often unpleasant in nature
Dysosmia- things smell differently than they should.
Hyperosmia- an abnormally acute sense of smell
Some times olfaction serve as marker for Perkinson’s diseases. Some illness can be diagnosed by their associated smell( e.g. acetone and diabetes). So smell therapy and clinical use of odour is an area for future.
Olfaction, or the sense of smell, is an ancient sensory system that together with taste enables an organism to detect chemicals in the external environment. Olfaction is one of the five major human senses (vision, hearing, olfaction, taste, and touch) that occurs when odorants bind to specific sites in olfactory receptors.Olfaction is present in most species such as insects, worms, fish, amphibians, birds, and mammals. It is essential for survival by permitting the location of food, mates, and predators, although in humans, olfaction is often viewed as an esthetic sense capable of triggering emotion and memory.
This document discusses the senses of smell and taste. It describes how odor receptor cells detect smells and transmit signals to the olfactory bulb. The vomeronasal organ detects pheromones through direct contact. The trigeminal nerve detects irritating stimuli through chemesthesis. Smell and taste provide important sensory information and influence many behaviors and memories.
The document summarizes the results of 5 sensory experiments:
1. A taste test identified regions of the tongue most sensitive to different tastes.
2. Pupil size changes with attention to near and far objects were measured.
3. Hearing sensitivity was measured by timing detection of clock ticks.
4. Sensitivity to hot and cold temperatures was tested by submerging hands.
5. Reaction time to pain stimulus was measured by timing removal of hand from ice.
The experiments measured sensitivity levels for different human senses like taste, sight, hearing, touch and pain. Results were recorded to understand how the senses function.
The olfactory system contains three main cell types in the olfactory epithelium: basal, supporting, and olfactory receptor cells. Basal cells act as stem cells that generate olfactory receptor cells, which are bipolar neurons that detect smells. The olfactory receptors send signals along the olfactory nerve to the olfactory bulb and tract in the brain. Loss of smell, or olfactory dysfunction, can be conductive due to blockage or sensorineural involving receptor or central nervous system damage. Common causes include upper respiratory infections, head trauma, nasal/sinus issues, and sometimes idiopathic causes. Evaluation involves smell identification tests to assess the ability to perceive and identify odors.
The document discusses the five basic human senses - sight, hearing, smell, taste, and touch. It provides details on the anatomy and physiology of how each sense works, including the sensory receptors involved and pathways in the brain. The key points made are that touch is not considered a special sense, while sight, hearing, smell and taste are the four special senses. Somatic senses include the various aspects of touch like pressure, temperature, and pain.
This document summarizes the chemical senses of taste and smell. It discusses the four primary tastes of sour, salty, sweet, and bitter. It describes taste buds, their locations in the tongue, and the mechanisms of taste stimulation and transmission to the brain. For smell, it outlines the olfactory membrane, olfactory cells and cilia, stimulation mechanisms, and transmission of smell signals to the olfactory bulb and brain. It also notes some clinical implications like taste blindness and disorders of smell.
The olfactory nerve (CN I) is the first and shortest cranial nerve. It transmits smell information from olfactory receptor cells in the nasal epithelium to the olfactory bulb. Axons from the receptor cells penetrate the cribriform plate and synapse with mitral cells in the olfactory bulb. Second order neurons in the olfactory tract carry signals to the primary olfactory cortex, involved in memory and appreciation of smells. The olfactory nerve is unique as a special sensory nerve that detects odors.
This document discusses sensory receptors, including their types, structures, and functions. It covers exteroceptors, visceroceptors, proprioceptors, mechanoreceptors, chemoreceptors, thermoreceptors, nociceptors, photoreceptors, olfactory receptors, taste receptors, hearing receptors, and balance receptors. Key points include that sensory receptors receive stimuli from both internal and external environments and relay this information to the nervous system, and that different receptor types are activated by mechanical, chemical, thermal, or light stimuli.
The document discusses various sensory organs and systems. It begins by explaining how sensations are initiated by stimuli and receptors. It then covers the different types of receptors - exteroceptors which detect stimuli near the body surface, interoceptors which detect internal stimuli, and proprioceptors which detect deep stimuli. Specific sensory systems are then described in more detail, including touch, pain, temperature, smell, taste, hearing and sight. The anatomy and physiology of the eye, ear and other sensory organs are explained.
This document provides an overview of the physiology of olfaction. It discusses:
- The anatomy of olfactory stimulation including the nasal passageways, olfactory mucus, and olfactory epithelium.
- The main cell types in the olfactory epithelium: ciliated olfactory receptors, microvillar cells, supporting cells, and basal cells.
- How odorant molecules stimulate the olfactory receptors and initiate the transduction pathway.
- The pathways that olfactory information takes from the olfactory epithelium to the olfactory bulb and onto various regions in the brain involved in olfaction.
- Theories on olfactory transduction and coding of odorant molecules.
-
Stereochemical theory of olfaction.docx 1Tanvir Nehal
The Stereochemical theory of olfaction states that a molecule's smell is due to its specific 3D structure fitting the "lock and key" mechanism of olfactory receptors in the nasal epithelium. Stereochemistry involves the study of the spatial arrangement of atoms that form molecular structures, including stereoisomers which have the same molecular formula and bonded atoms but differ in 3D orientation. The theory proposes that stereoisomers of volatile oil molecules will bind to different olfactory receptors and be detected as different smells, such as the stereoisomers of carvone smelling like mint versus caraway.
This document discusses the anatomy and physiology of four sensory systems - acoustic, vestibular, gustatory, and olfactory. It describes the receptor, conduction, and central processing components of each system. Key points include the roles of the cochlea, semicircular canals, taste buds, and olfactory epithelium as receptor sites, and how signals are transmitted by cranial nerves to processing centers in the brainstem and cortex. Theories of sound perception and mechanisms of smell detection are also summarized.
1. The sense of smell occurs in the olfactory epithelium located in the upper part of the nasal cavity. Olfactory sensory neurons here detect odorant molecules and transmit signals to the olfactory bulb.
2. When an odorant molecule binds to an olfactory receptor, it triggers a signal transduction pathway involving cAMP that leads to an action potential. This signal is transmitted via the olfactory nerve to the olfactory bulb.
3. The olfactory pathway projects from the olfactory bulb to areas involved in perception and emotion processing like the piriform cortex, amygdala and orbitofrontal cortex. Factors like concentration, adaptation and injury can influence olfactory function.
The document discusses the different types of sense organs in insects, including mechanoreceptors, auditory receptors, chemoreceptors, thermoreceptors, and photoreceptors. It provides examples of each type of sense organ and their functions, such as trichoid sensilla which detect touch, Johnston's organ which detects antennal movements, and compound eyes which allow insects to detect light, form, and color. The sensory organs help insects perform important functions like finding hosts, food, and mates as well as sensing their environment.
The document discusses olfactory receptors and compares the olfactory receptor gene OR4D11 between humans and chimpanzees. It finds that OR4D11 is a pseudogene in humans but intact in chimpanzees. It also summarizes the results of BLAST searches comparing the human and chimpanzee OR4D11 sequences and structures, finding them to be 96% similar. Phylogenetic analysis shows OR4D11 is conserved in other species like mice, dogs, and rats.
This document discusses the senses of smell (olfaction) and taste. It notes that smell and taste have a cooperative relationship, with odor contributing approximately 80% of what we perceive as flavor. The main points covered include:
- Smell and taste are classified as special senses along with sight, hearing, and balance
- The olfactory system includes receptors in the nose, olfactory bulbs, and pathways to the brain regions involved in emotion and behavior
- Pheromones influence behaviors through a vomeronasal system present in many animals
- Humans have a less developed sense of smell compared to most animals
- The olfactory epithelium regenerates sensory neurons throughout life but this capacity declines with age
The document provides an overview of the special senses of taste, hearing, smell, and vision. It includes the following key points:
- Taste is detected by taste buds on the tongue and involves four basic tastes: sweet, sour, salty, and bitter. Taste pathways transmit signals to the brainstem.
- Hearing involves the outer, middle and inner ear. Sound waves cause the eardrum and bones of the middle ear to vibrate, transmitting signals through nerves to the brain.
- Smell receptors in the nose detect odors which activate pathways to areas of the brain involved in memory and emotion.
- Vision involves light entering the eye through the cornea and lens, with
The document discusses chemoreceptors, which include taste receptors and olfactory receptors. Taste and smell rely on chemical receptors being stimulated by certain molecules. Humans can taste sweet, sour, bitter, salty, and umami; taste and smell are directly related because they use the same types of receptors. Olfactory receptors are located in the nose, while taste receptors are located in the tongue and oral cavity. Both system detect chemicals and transmit signals to the brain.
The document discusses abnormalities of smell and olfactory disorders. It describes the main components of the olfactory system and pathways. Several types of smell disorders are defined, including anosmia, hyposmia, dysosmia, and phantosmia. Causes of smell disturbances include upper respiratory infections, head trauma, nasal/sinus disease, tumours, and neurodegenerative diseases. Clinical evaluation involves a history, smell tests, and physical exam including the nose and sinuses. Treatment depends on whether the impairment is conductive or sensorineural.
1. Disorders of olfaction can be conductive, resulting from nasal obstruction, or sensorineural, due to damage to the olfactory neuroepithelium.
2. Common causes of sensorineural disorders include upper respiratory infections, head trauma, tumors near the olfactory region, congenital defects, toxins, age-related changes, and neurodegenerative diseases.
3. Specific conditions that can cause olfactory disorders are post-viral olfactory dysfunction, Kallmann syndrome, septo-optic dysplasia, holoprosencephaly, exposure to metals or other toxins, Alzheimer's disease, Parkinson's disease, and epilepsy presenting with olfactory auras.
Olfaction is very important for us and also for other animals.
Dog’s sense of smell is 1000 times more than humans. People use dog’s keen sense of smell in many ways---
Govt. agencies use specially trained dogs in search and rescue missio
Detection of narcotics.
Detection of forensic cadaver material.
Due to lack of smell the following disorders may be seen---
Anosmia : lack of ability to smell
Hyposmia- decreased ability to smell
Phantosmia- [“hallucinated smell”] often unpleasant in nature
Dysosmia- things smell differently than they should.
Hyperosmia- an abnormally acute sense of smell
Some times olfaction serve as marker for Perkinson’s diseases. Some illness can be diagnosed by their associated smell( e.g. acetone and diabetes). So smell therapy and clinical use of odour is an area for future.
Olfaction, or the sense of smell, is an ancient sensory system that together with taste enables an organism to detect chemicals in the external environment. Olfaction is one of the five major human senses (vision, hearing, olfaction, taste, and touch) that occurs when odorants bind to specific sites in olfactory receptors.Olfaction is present in most species such as insects, worms, fish, amphibians, birds, and mammals. It is essential for survival by permitting the location of food, mates, and predators, although in humans, olfaction is often viewed as an esthetic sense capable of triggering emotion and memory.
This document discusses the senses of smell and taste. It describes how odor receptor cells detect smells and transmit signals to the olfactory bulb. The vomeronasal organ detects pheromones through direct contact. The trigeminal nerve detects irritating stimuli through chemesthesis. Smell and taste provide important sensory information and influence many behaviors and memories.
The document summarizes the results of 5 sensory experiments:
1. A taste test identified regions of the tongue most sensitive to different tastes.
2. Pupil size changes with attention to near and far objects were measured.
3. Hearing sensitivity was measured by timing detection of clock ticks.
4. Sensitivity to hot and cold temperatures was tested by submerging hands.
5. Reaction time to pain stimulus was measured by timing removal of hand from ice.
The experiments measured sensitivity levels for different human senses like taste, sight, hearing, touch and pain. Results were recorded to understand how the senses function.
The olfactory system contains three main cell types in the olfactory epithelium: basal, supporting, and olfactory receptor cells. Basal cells act as stem cells that generate olfactory receptor cells, which are bipolar neurons that detect smells. The olfactory receptors send signals along the olfactory nerve to the olfactory bulb and tract in the brain. Loss of smell, or olfactory dysfunction, can be conductive due to blockage or sensorineural involving receptor or central nervous system damage. Common causes include upper respiratory infections, head trauma, nasal/sinus issues, and sometimes idiopathic causes. Evaluation involves smell identification tests to assess the ability to perceive and identify odors.
The document discusses the five basic human senses - sight, hearing, smell, taste, and touch. It provides details on the anatomy and physiology of how each sense works, including the sensory receptors involved and pathways in the brain. The key points made are that touch is not considered a special sense, while sight, hearing, smell and taste are the four special senses. Somatic senses include the various aspects of touch like pressure, temperature, and pain.
This document summarizes the chemical senses of taste and smell. It discusses the four primary tastes of sour, salty, sweet, and bitter. It describes taste buds, their locations in the tongue, and the mechanisms of taste stimulation and transmission to the brain. For smell, it outlines the olfactory membrane, olfactory cells and cilia, stimulation mechanisms, and transmission of smell signals to the olfactory bulb and brain. It also notes some clinical implications like taste blindness and disorders of smell.
The olfactory nerve (CN I) is the first and shortest cranial nerve. It transmits smell information from olfactory receptor cells in the nasal epithelium to the olfactory bulb. Axons from the receptor cells penetrate the cribriform plate and synapse with mitral cells in the olfactory bulb. Second order neurons in the olfactory tract carry signals to the primary olfactory cortex, involved in memory and appreciation of smells. The olfactory nerve is unique as a special sensory nerve that detects odors.
This document discusses sensory receptors, including their types, structures, and functions. It covers exteroceptors, visceroceptors, proprioceptors, mechanoreceptors, chemoreceptors, thermoreceptors, nociceptors, photoreceptors, olfactory receptors, taste receptors, hearing receptors, and balance receptors. Key points include that sensory receptors receive stimuli from both internal and external environments and relay this information to the nervous system, and that different receptor types are activated by mechanical, chemical, thermal, or light stimuli.
The document discusses various sensory organs and systems. It begins by explaining how sensations are initiated by stimuli and receptors. It then covers the different types of receptors - exteroceptors which detect stimuli near the body surface, interoceptors which detect internal stimuli, and proprioceptors which detect deep stimuli. Specific sensory systems are then described in more detail, including touch, pain, temperature, smell, taste, hearing and sight. The anatomy and physiology of the eye, ear and other sensory organs are explained.
The nose is responsible for smell and breathing. The cavity is lined with mucous membranes containing smell receptors connected to the olfactory nerve. Smells are detected by receptor cells in the nose interacting with odor molecules and transmitting sensations to the brain. The nose has a bony and cartilaginous framework supporting its structure and function. Olfactory receptors in the nose detect smells and transmit information through the olfactory bulb and tract to areas of the brain involved in perceiving odors. The nose also functions to warm, humidify, and filter air during breathing.
This document discusses different types of sensory receptors in the human body. It describes exteroceptors, which receive external stimuli from areas like the skin, and visceroreceptors, located in internal organs. It also discusses proprioceptors, which provide information about body position and movement. It then explains different categories of receptors based on what they detect, such as mechanoreceptors for touch and pressure, chemoreceptors for chemicals, thermoreceptors for temperature, and photoreceptors for light. The document also mentions nociceptors, which detect potentially painful stimuli.
This document summarizes the main sensory organs in the body - vision, hearing, taste, smell, and touch. It describes the anatomy and physiology of the eye, ear, taste buds, olfactory system, and receptors for touch. The eye contains the retina with rods and cones for vision. The ear is divided into external, middle, and inner sections for hearing and balance. Taste buds contain gustatory cells that detect the five basic tastes. The olfactory region contains sensory cells that detect smells. Various receptors throughout the body sense touch, pain, temperature, and proprioception.
The document discusses the special senses of vision, hearing, balance, taste and smell. It focuses on the anatomy and physiology of hearing and balance. Key points include:
- The ear is divided into external, middle and inner sections. Sound waves cause the eardrum and ossicles to vibrate, transmitting vibrations to the cochlea.
- The cochlea contains the organ of Corti with hair cells that transduce vibrations into nerve impulses. Different hair cell regions respond to different frequencies.
- Loudness is determined by vibration amplitude and number of activated hair cells. Reflexes protect from loud noises.
- The vestibular system detects head position
The document provides information on the somatic and special senses. It discusses the different types of receptors including chemoreceptors, nociceptors, thermoreceptors, mechanoreceptors, and photoreceptors. It then describes the specific senses - touch, pain, temperature, taste, smell, hearing, equilibrium, sight. For each sense, it outlines the receptors involved, their location, and how sensory information is transmitted to the brain. The document also reviews the anatomy and physiology associated with smell, hearing, taste, equilibrium, and vision.
Nose anatomy & physiology sensory systemPooja Rani
The nose consists of the external nose and nasal cavity divided by a septum. The external nose has two nostrils separated by the nasal septum. The framework of the external nose is made up of nasal bones, frontal processes of maxillae, and nasal part of frontal bone. The nose contains 10-100 million olfactory receptors for smell within the olfactory epithelium in the nasal cavity. Olfactory receptors are neurons that transmit signals from inhaled chemicals to the olfactory bulb.
This document summarizes key aspects of human olfaction and the sense of smell. It discusses:
1) How humans have fewer olfactory receptors than other animals like dogs, but our receptors can still detect single odorant molecules.
2) The structures involved in smell including the olfactory epithelium, olfactory sensory neurons, olfactory bulbs, and their connections to the limbic system and cortex.
3) Theories of how we perceive smells, with the dominant theory being that the pattern of odorant binding in the epithelium determines our scent perception.
4) Factors that influence our olfactory detection thresholds and ability to smell over time.
Animals have developed specialized sensory organs like eyes and ears to actively seek information from the environment. These organs evolved to help detect things like food from a distance. The eye detects light and vision, while the ear detects sound and hearing. Both eyes and ears have complex structures that are finely tuned to receive and process sensory inputs. The eye contains light-sensitive rods and cones in the retina to detect color and vision. The ear detects sound waves through the outer, middle, and inner ear structures that funnel and amplify sound before vibrations are converted to nerve signals. These special senses allow animals to effectively interact with their surroundings.
This document provides information about the five basic human senses and their associated sensory organs. It discusses the skin, eyes, ears, tongue and nose. For each sense organ, it describes the structures involved in sensation, how stimuli are received and transmitted to the brain, and examples of common disorders. The skin, largest sensory organ, protects the body and regulates temperature. It has three layers - epidermis, dermis and subcutaneous tissue. The eyes contain the retina, lens and other structures that allow vision. Sound waves are received by the outer, middle and inner ear before signals reach the brain. Taste buds on the tongue can detect the four basic tastes. Odor molecules stimulate receptors in the nasal cavity to provide the sense
This document summarizes key aspects of human olfaction including embryology, anatomy, physiology, and causes of olfactory dysfunction. It describes:
- The development of the olfactory system during embryogenesis and the role of olfactory receptors, placodes, and sacs.
- The main anatomical structures involved in olfaction like the olfactory epithelium, bulb, tract and cortex and their functions.
- The physiology of odorant molecule detection by receptors, transduction and coding in the olfactory epithelium and bulb.
- Theories to explain odor quality and stimulation like vibration, shape, penetration and enzyme theories.
- Types of olfactory dysfunction like anosmia, hyposmia and
1. The document provides an in-depth look at the nervous system through recipes related to sensory receptors and special senses.
2. It details the various types of sensory receptors, including their locations, stimuli detected, and structures. It also examines the special senses of smell, taste, hearing, balance, and vision.
3. The recipes describe the key components and processes of each sensory system, such as olfactory receptors and pathways for smell, taste buds and neural pathways for taste, and the mechanism of hearing and visual pathway.
1. The document provides an in-depth look at the nervous system through recipes related to sensory receptors and special senses.
2. It details the various types of sensory receptors, including their locations, stimuli detected, and structures. It also examines the special senses of smell, taste, hearing, balance, and vision.
3. The recipes describe the key components and processes of each sensory system, such as olfactory receptors and pathways for smell, taste buds and neural pathways for taste, and the mechanism of hearing and visual pathway.
The document summarizes the anatomy and physiology of the olfactory system. It describes the main parts including the olfactory epithelium containing olfactory receptor cells that detect odors, as well as supporting and basal cells. It explains how odors bind to receptors and trigger signals to the olfactory bulb and various parts of the brain involved in smell perception and response, like the limbic system and orbitofrontal cortex. The olfactory system is divided into very old, less old, and newer parts associated with more primitive and learned odor responses.
The document discusses the sense of smell (olfactory) in humans. It explains that smell involves odorant molecules dissolving in mucus in the olfactory epithelium located in the upper part of the nose, activating olfactory receptor neurons. These neurons transmit signals to the olfactory bulb and then parts of the brain involved in emotion and memory. The brain interprets these signals as the perception of specific odors. Richard Axel and Linda Buck discovered that humans have around 1000 olfactory receptor genes and that each receptor neuron expresses only one type.
The nose is responsible for smell and plays an important role in the brain's formation of memories and navigation. Smells are detected by receptors in the nose which send signals to the olfactory bulb. The olfactory bulb then synchronizes neural networks through brain waves to link smells to memories. New research traces the connections between the nose, olfactory bulb, and other limbic system structures involved in emotions, motivation, and memory formation. The limbic system translates sensory data from smells into behavioral responses.
Senses : any of the physical processes by which stimuli are received, transduced, and conducted as impulses to be interpreted in the brain.
The special senses consist of the eyes, ears, nose, throat and skin.
Each of these organs have specialized functions that make if possible for us to experience our environment and to make that experience more pleasant
The document discusses lung volumes and capacities, including tidal volume, inspiratory reserve volume, expiratory reserve volume, vital capacity, residual volume, total lung capacity, and minute ventilation. It provides definitions and normal ranges for these measurements and how they are used to understand lung function and disease states. An experiment is described to measure these values and correlate them with clinical conditions like fibrosis and emphysema.
This document discusses lung volumes and capacities, including tidal volume, inspiratory reserve volume, expiratory reserve volume, vital capacity, residual volume, and total lung capacity. It provides definitions of each term and an experiment measuring these volumes. Males generally have slightly higher lung capacities than females. Conditions like fibrosis decrease total lung capacity and vital capacity by making lungs stiffer, while emphysema decreases vital capacity but not total lung capacity due to increased residual volume.
This document analyzes blood typing results for 4 patients and discusses key aspects of blood typing such as agglutinogens, agglutinins, and blood types. It also addresses important applications of blood typing like transfusions and issues like hemolytic disease in newborns. Key points covered include how blood type is determined based on antigens on red blood cells, the antibodies found in plasma, and which blood types are compatible for transfusions. Taking multiple samples when performing blood counts is also discussed as an important method to reduce errors.
This document analyzes blood typing results from four patients: Mrs. Smith, Mr. Jones, Mr. Green, and Ms. Brown. It identifies their agglutination reactions to different blood serum antibodies and determines their blood types. Additional questions are asked about blood type compatibility for transfusions, the definition of erythroblastosis fetalis, minimizing disease transmission in blood labs, and the potential benefits of a synthetic blood substitute.
The document discusses electrocardiograms (EKGs) and how they are used to analyze the electrical activity of the heart. It provides the following key points:
- An EKG records the electrical events in the heart as it beats, showing the natural conduction pathways and contractions of the atria and ventricles.
- The different waves in an EKG (P, QRS, T) represent different stages of the heartbeat and can indicate heart conditions if abnormal.
- By placing electrodes in different positions, additional information can be gleaned from EKG tracings about the direction of electrical activity in the heart.
- Doctors can analyze EKG tracings for abnormalities that may indicate conditions like
This document analyzes blood typing results for 4 patients and discusses key aspects of blood typing such as agglutinogens, agglutinins, and blood types. It also covers topics like erythroblastosis fetalis, uses of blood typing, minimizing disease risk, and potential future advances. The document contains a table summarizing each patient's test results and questions testing the reader's understanding of blood type analysis and compatibility.
This document discusses electrocardiograms (EKGs) and how they are used to analyze the electrical activity of the heart. It provides the following key points:
1. An EKG records the electrical signals produced by the heart during each beat and can be used to determine heart rate and identify any abnormalities.
2. The main components of an EKG waveform are labeled P, Q, R, S, and T and correspond to different stages of electrical conduction through the heart.
3. Doctors can examine EKG tracings to diagnose conditions like arrhythmias, heart attacks, or damage to heart muscle based on changes in waveforms and timing of intervals between components.
1. The data tables show the subject's baseline blood pressure and heart rate measurements, as well as measurements taken after exercising. Systolic, diastolic, and mean arterial pressures all increased after exercise, as did heart rate.
2. Cardiac output increased from 2225 mL/min at baseline to 2775 mL/min after exercise due to an increase in stroke volume from 75 mL to 100 mL and a decrease in heart rate from 89 bpm to 71 bpm.
3. Pulse pressure, the difference between systolic and diastolic pressure, increased after exercise primarily due to an increase in stroke volume ejected from the left ventricle with each heartbeat.
The document describes an experiment where a subject immersed their foot in ice water, measuring changes in their blood pressure and heart rate. Their systolic, diastolic, and mean arterial pressures all increased in response to the cold stimulus. Their heart rate reached a maximum of 106 BPM after 38 seconds, then fell to a rebound rate of 94 BPM after 34 seconds as it returned to homeostasis. The document also discusses an exercise experiment where the subject's blood pressures and heart rate increased with exercise, then recovered within a minute, indicating good physical fitness.
The document contains data tables and analysis of changes in vital signs (blood pressure, heart rate, etc.) in response to cold water immersion and exercise. Key findings include:
1) Cold water immersion caused increases in systolic/diastolic blood pressure, mean arterial pressure, and heart rate, preparing the body for "fight or flight."
2) Exercise similarly increased these vital signs. Cardiac output increased by 5,800 mL/min based on a stroke volume increase from 75 to 100 mL/beat and heart rate change.
3) Recovery heart rate returned to resting levels 20 seconds after reaching maximum, showing homeostasis mechanisms act more slowly than stress responses.
The document contains data tables and analysis of blood pressure and heart rate responses to exercise. Table 1 shows baseline blood pressure readings. Table 2 shows increases in systolic, diastolic and mean arterial pressure after exercise. Table 3 lists heart rates at rest, maximum exertion, and recovery. Analysis explains trends of increased blood pressure and heart rate in response to exercise to increase cardiac output. Pulse pressure increases due to higher systolic pressure from exercise. Recovery time relates to fitness level. Congestive heart failure causes faster heart rates to compensate for weaker pumping. Medicines can regulate abnormal heart rates.
The document contains data tables and analysis of blood pressure and heart rate responses to exercise. Table 1 shows baseline blood pressure readings. Table 2 shows readings after exercise, with increases in systolic, diastolic, and mean arterial pressures. Table 3 lists heart rates at rest, maximum, and recovery. Analysis calculates changes in cardiac output and pulse pressure with exercise. It compares the subject's heart rates and recovery time to classmates and discusses expected responses in heart conditions like congestive heart failure.
When exposed to a cold stimulus, the participant's blood pressure, including systolic, diastolic, and mean arterial pressure increased, as did their heart rate. These physiological responses prepare the body for the fight or flight response by increasing blood flow. The participant's maximum heart rate of 80.32 bpm occurred after 60.07 seconds of submerging their foot in ice water. Their heart rate then returned to its resting rate of 72.01 bpm within 20 seconds, demonstrating the body's mechanisms for maintaining homeostasis. Prolonged fear can cause the heart rate to drop too low, reducing blood flow and pressure to the brain, potentially leading to fainting.
When exposed to a cold stimulus, the participant's blood pressure, including systolic, diastolic, and mean arterial pressure increased, as did their heart rate. These physiological responses prepare the body for the fight or flight response by increasing blood flow. The participant's maximum heart rate of 80.32 bpm occurred after 60.07 seconds of submerging their foot in ice water. Their heart rate then returned to its resting rate of 72.01 bpm within 20 seconds, demonstrating the body's mechanisms for maintaining homeostasis. Prolonged fear can cause the heart rate to drop too low, reducing blood flow and pressure to the brain, potentially causing fainting.
The document contains 3 tables that provide baseline blood pressure measurements, blood pressure measurements after exercise, and heart rate data. It then poses 8 questions for analysis.
The blood pressure and heart rate all increased with exercise, and the change in cardiac output was calculated to be 5,800. Pulse pressure rises during exercise due to increased heart rate and breathing. Recovery time was slightly shorter than peers due to better physical fitness from softball. Congestive heart failure would cause a faster heart rate at rest and during exercise to compensate for reduced pumping strength. Medication should be given to slow a resting heart rate of 120 beats per minute.
Cartilage is a specialized connective tissue containing cells called chondrocytes that secrete an extracellular matrix. There are three main types of cartilage - hyaline, elastic, and fibrocartilage - each with different compositions and locations in the body. Growth plates are areas of cartilage at the ends of long bones that allow for bone growth in children through endochondral ossification as cartilage is replaced by bone.
Cartilage is a specialized connective tissue containing cells called chondrocytes that secrete an extracellular matrix. There are three main types of cartilage - hyaline, elastic, and fibrocartilage - each with different compositions and locations in the body. Growth plates are areas of cartilage at the ends of long bones that allow for bone growth in children through endochondral ossification as cartilage is replaced by bone.
The cerebellum is divided into three main parts - the vermis, paravermis, and cerebellar hemispheres. It regulates muscle tone and coordinates movement, and also contributes to cognitive processes. The diencephalon includes the thalamus and hypothalamus. The thalamus relays sensory information and controls memories and emotions, while the hypothalamus regulates body processes. The cerebral cortex controls sensations, movement, thought, reasoning, and memory through its folded surface area.
The document repeats the phrase "Our Theme is Reference Book/dictionary" multiple times and provides two pictures without captions or context. It then discusses how voluntary muscle movement takes longer for the brain to signal than involuntary movement caused by tendon stimulation, and cites research finding the speed of involuntary movement to be 100m/s on average based on repeated tests of multiple people.
This document contains 5 citations related to synapses and neurotransmitters:
1. A 2002 study on spatial summation for single and multi-line motion stimuli.
2. The 2008 Gale Encyclopedia of Science entry on neurotransmitters.
3. The 2008 Gale Encyclopedia of Science entry on synapses.
4. A 2000 study on electrophysiological methods for assessing regional analgesia.
5. A 2009 article critiquing neurotransmitter testing methods.
1. Structure
• Free nerve ending: a form of peripheral ending of sensory nerve fibers in which
the terminal filaments end freely in the tissue.
Synonyms: terminationes nervorum liberae (40)
• Root Hair Plexuses: free nerve endings associated with hair follicle - very sensitive
to touch which moves the hair (41)
• Merkel Disks: Merkel's disks are located in the epidermis, where they are precisely
aligned with the papillae that lie beneath the dermal ridges. They account for
about 25% of the mechanoreceptors of the hand and are particularly dense in the
fingertips, lips, and external genitalia. (42)
• Meissner Corpuscle: enclosed in connective tissue capsule, just below epidermis in
hairless areas of skin such as lips, finger tips, nipples, external genitalia, palms of
hands and soles of feet - fine touch and pressure (41)
• Pacinian Corpuscles: enclosed in multilayered connective tissue capsule, in
deeper skin and tendons, sensitive to deep pressure and high pressure vibrations
(41)
• Muscle Spindles: small sensory organs that are enclosed within a capsule. They
are found throughout the body of a muscle, in parallel with typical muscle fibers.
There are several small, specialized muscle fibers known as intrafusal fibers. (43)
• Golgi tendon Organs: are in series with muscle fibers, located in the tendons that
attach muscle to bone. The sensory dendrites of the Golgi tendon organ afferent
are interwoven with collagen fibrils in the tendon. (43)
4. SMELL
Smell (give diagram of nose indicating receptors)
Describe each
(1) smell, also called Olfaction, the detection and identification by sensory organs of
airborne chemicals. The concept of smell, as it applies to humans, becomes less distinct
when invertebrates and lower vertebrates (fish and amphibians) are considered, because
many lower animals detect chemicals in the environment by means of receptors in
various locations on the body, and no invertebrate possesses a chemoreceptive structure
resembling the vertebrate nasal cavity. For this reason, many authorities prefer to regard
smell as distance chemoreception and taste as contact chemoreception.
Left Right
receptor receptor
bulb bulb
(20)
6. Olfactory receptors
olfactory receptor, also called
smell receptor, of binding odour
molecules that plays a central role
in the sense of smell (olfaction). In
terrestrial vertebrates, including
humans, the receptors are located
on olfactory receptor cells, which
are present in very large numbers
(millions) and are clustered within
a small area in the back of the
nasal cavity, forming an olfactory
epithelium. (2)
(20)
OLFACTORY RECEPTOR BULB
7. Olfactory pathways
Olfactory
OLFACTORY
straie
RECEPTOR
(yellow)
BULB (blue)
(20)
The sense of smell can create a powerful and long lasting memories.
These memories couples with unique sensory inputs especially ordor,
often persist from early child hood to death. New car, baby, kitchen and
people odors are all olfactory triggers that often bring back memories of
events that have occurred from the past. There is a huge relationship
between the olfactory and gustatory pathways because our sense of
smell and taste are closely related. (8)
8. Com paring human and canine olfaction
(5)Taste bud organ located on the tongue in terrestrial vertebrates that
functions in the perception of taste. In fish, taste buds occur on the lips, the
flanks, and the caudal (tail) fins of some species and on the barbells of
catfish. In most animals, including humans, taste buds are most prevalent on
small pegs of epithelium on the tongue called papillae The taste receptor
cells of other animals can often be characterized in ways similar to those of
humans, because all animals have the same basic needs in selecting food.
(4)
9. Neural pathway
The gustatory sensations or taste are closely associated with olfaction. Taste
receptors are located inside structures called taste buds that line the surface
of the tongue, and are found on the soft palate, pharynx, and larynx.
Nervous impulses generated in the anterior two thirds of the tongue travel
over the facial nerve where they are generated from the posterior one third
are conducted by fibers of the glossopharynegal.(10)
(9)
10. Taste
(20)
Taste buds:
bitter,
sweet,
papillaeh
sour,
salty
The taste buds are embedded in the epithelium of the tongue and make
contact with the outside environment through a taste pore.
Taste Buds are small organs located on the tongue in
terrestrial vertebrates that functions in the perception of taste
Taste buds are composed of groups of between 50 and 150 columnar taste receptor
cells bundled together like a cluster of bananas. The taste receptor cells within a bud
are arranged such that their tips form a small taste pore, and through this pore
extend microvilli from the taste cells. The microvilli of the taste cells bear taste
receptors.
12. The Mechanism of Hearing
When one hears a sound or someone speaking, then an image
comes to mind that is called the cartilaginous tissue, or the pinna.
The pinna directs the sound energy into the ear canal. The eternal
meatus is about one inch in length and is closed at the inner end
near the ear drum; it forms a passage way in which sound energy
may be transmitted into the inner reaches of the ear. (30)
(45)
13. Neuronal pathway of Hearing
Cochlear N. to the brain stem interneurons to multi-neuron pathway
to the thalamus then to the auditory cortex
The Organ of Corti with its sound-sensitive hair cells and basilar
membrane are important parts of the sound transducing system for
hearing. Mechanical vibrations of the basilar membrane generate
membrane potentials in the hair cells which produce impulse
patterns in the cochlear portion of the vestibulocochlear nerve
(cranial nerve VIII). (53)
15. Vestibule and semicircular canals
The vestibule has a round open space that accesses various passageways, it is
the central structure within the inner ear. The outer wall of the vestibule contains
the oval and round windows (which are the connection sites between the middle
and inner ear). Internally, the vestibule contains two membranous sacs, the
utricle and the saccule, which are lined with tiny hair cells. (47)
The semicircular canals have three bony tubes that form loops. Each tube ends
in a bulge, or ampulla, containing sensors that detect the movement of fluid in
the loop—which depends on your body’s movement. Similar receptors called
maculae detect how upright you are. Your brain uses these signals to correct your
balance. (48)
The vestibular system serves the bodily functions of balance and equilibrium. It
accomplishes this by assessing head and body movement and position in space,
generating a neural code representing this information, and distributing this
code to appropriate sites located throughout the central nervous system.
Vestibular function is largely reflex and unconscious in nature. (46)
16. Having a sense of balance is…
The semicircular canals are three pretzel-like curved tubes arranged at
angles roughly perpendicular to each other, with the two vestibular sacs
located at their base. Both the canals and sacs contain fluid and tiny hair
cells, which act as receptors. When a person's head moves, the fluid
disturbs the hair cells, which stimulate a branch of the auditory nerve,
signaling the brain to make adjustments in the eyes and body. A
movement at any given angle will have its primary effect on one of the
three canals. Overstimulation from extreme movements will produce
dizziness and nausea. (32)
17. Dynamic Equilibrium…
The special sense which interprets balance when one is moving, or
at least the head is moving; the semicircular canals contain the
receptors for dynamic equilibrium; within each semicircular canal
is a complex mechanoreceptor called a crista ampullaris which
contains the mechanoreceptors (Hair cells) for dynamic
equilibrium; when the perilymph in one of the semicircular canals
moves, the hair cells in the crista ampullaris are stimulated to send
nerve impulses to the brain; this advises the brain of whether or
not a person has their balance during body movements or if their
body is in motion, such as moving their head side-to-side.(50)
18.
19. Cavities and humors of the eye
• Humors- is the clear gel that fills the space between the
lens and the retina of the eyeball of humans and other
vertebrates. It is often referred to as the vitreous body
or simply "the vitreous".
• Cavities of the eye- the anterior cavity is actually
divided into two subcategories.
• the anterior chamber ( from iris to cornea)
• the posterior chamber ( from iris to lens)
20. Muscles of the eye
Since only the fovea provides sharp distinct vision, the eye must move to
follow a target. It must be precise and fast. This is seen in scenarios like
reading, wherein the reader must shift gaze constantly, or following a small
object like a golf ball, in which the extraocular muscles must lead the eye to
follow the head movements. Although under voluntary control, most
movement is done without thinking, such as those based on head or other
body movement, or movement of objects in the area. Researchers still have
some work in order to find the parallel nature of the environment-based
(involuntary) and voluntary control
21. accessory structures
The site of accessory structures of
the eye are as follows: eyebrows,
eyelashes, eyelids, conjunctiva,
and lacrimal apparatus.
22. Photopigments
The photopigments that absorb light all have a
similar structure, which consists of a protein
called an opsin and a small attached molecule
known as the chromophore. The chromophore
absorbs photons of light, using a mechanism that
involves a change in its configuration. In
vertebrate rods the chromophore is retinal, the
aldehyde of vitamin A1
23. Retinal image
formation of focused images on the
photoreceptors of the retina depends on the
refraction (bending) of light by the cornea and the
lens . The corna is responsible for most of the
necessary refraction, a contribution easily
appreciated by considering the hazy out-of-focus
images experienced when swimming underwater.
Water, unlike air, has a refractive index close to
that of the cornea; as a result, immersion in water
virtually eliminates the refraction that normally
occurs at the air/cornea interface.
24. Rods & cones
Rods are responsible for vision at low light levels (scotopic vision). They do
not mediate color vision, and have a low spatial acuity.
Cones are active at higher light levels (photopic vision), are capable of color
vision and are responsible for high spatial acuity. The central fovea is
populated exclusively by cones. There are 3 types of cones which we will
refer to as the short-wavelength sensitive cones, the middle-wavelength
sensitive cones and the long-wavelength sensitive cones or S-cone, M-
cones, and L-cones for short
25. Questions
Why don't deer see Hunters who wear Bright orange?
Deer have no red-sensitive cone cells in their eyes, so they can't tell red or
orange from green and brown.
What is the difference between "nearsighted" and "farsighted"? How are
each of these corrected?
There are several differences between being nearsighted and being
farsighted, as these are two different vision problems. Nearsightedness is
called myopia, and farsightedness is known as hyperopia. The main
biological difference in the two is that in myopia, the images seen are
focused in front of the retina, rather than directly on the retina. In
hyperopia, the images are focused behind the retina, rather than on top of
it. You can fix these problems by simply getting eye glasses