Physiology of Nervous Systems PDF

& ↑ L27 ORGANIZATION OF THE NERVOUS SYSTEM Murtala Abubakar (2024) S Sultan Qaboos University © College of Me...

& ↑ L27 ORGANIZATION OF THE NERVOUS SYSTEM Murtala Abubakar (2024) S Sultan Qaboos University © College of Medicine and Health Sciences Objectives L27. ORGANIZATION OF THE NERVOUS SYSTEM 1. Explain the general organization of the nervous system into central and peripheral 2. Discuss the functional division of the nervous system; the sensory, motor and integrative 3. Describe how brain is organized 4. Explain the functional organization of the cerebral cortex. 5. Explain hemispheric specialization. ↑ 6. Briefly discuss the functions associated with cerebellum 7. Define brain waves and understand their significance  Nervous System - The nervous system detects environmental changes that affect the body, then works in tandem with the endocrine 7m % endocrine system to respond to such events. nervous system &. work system - together to respond to the events It is responsible for all our behaviors, memories, and movement. it do this How ??? It is able to accomplish all these functions because of the - excitable characteristic of nervous tissue, which allows for & the generation of nerve impulses (action potentials). - excitable characteristic : mean in can generate to anywhere in the body action Potentials That. if excite it: it can you sent signal to all you body  Functions of the Nervous System The nervous system basically operates through 3 -W fundamental steps: 1.A sensory function detects internal and external stimuli. -is - 2.An integrative function is made (analyse and makes - decision). about thinking information from - 3.A motor function occurs (effector). receive - the brain  Organization of the Nervous System Nervous system is organized into two main subdivisions: - 1. The central nervous system (CNS) L --S1 --- Consists of the brain and spinal cord Within the CNS, some neurons that share similar functions are grouped into Collectian a aggregations called nuclei - thene a 2. The peripheral nervous system (PNS) Includes sensory receptors for various kinds of stimuli, the peripheral portions of spinal and cranial nerves, and all the peripheral portions of the autonomic nervous system Peripheral ganglia are groups of nerve cells - concentrated into small knots or clumps that - - are located outside the CNS. > Organization of the nervous system  Organization S of the central nervous system The central nervous system (CNS) consists of: cerebral corten 1. The brain El Dieception Basel nuclei Dien cephalon Cerebrum - Basal nuclei · ·Cerebral cortex · /12341 Diencephalon Forebrain thalamus hypothalamus Cerebellum · zi Midbrain 2 Pons Brain stem Medulla ⑪ 2. The spinal cord  The Cerebrum by corpus * The right hemisphere to the send information Collosum left hemisphere by to exchange Corpus callosum the information from right to left and rise versa A neural link its on The two cerebral hemispheres are connected by the corpus callosum The corpus callosum serves as the body's "information superhighway," allowing the two brain hemispheres to communicate and work together by continuously exchanging information through this neural link.  Organization of the cerebral cortex in to lobes The four pairs of lobes in the cerebral cortex each specialize in & different functions. Occipital Lobes: responsible for visual processing. 82614 Temporal Lobes: receive auditory (sound) input. Parietal Lobes: receive and process sensory input. Frontal Lobes: Voluntary motor activity · bi 1 Speaking ability -514g Elaboration of thought l e Organization of the cerebral cortex The cortex is topographically organized in two ways: First, certain areas of the cortex mediate specific functions. for motor For example, the area that activity mediates motor control is a well-defined strip of cortex touch located in the frontal lobe if you - something Lot called motor cortex. touch cdd something - The area that receive or somatosensory information is located in the parietal lobe Second, within a portion of cortex that manages a specific function (e.g., motor control, somatic sensation, hearing, or vision), the parts of the body spatially map onto this cortex in an&orderly way The most Point important Cortical Somatotopy: Homunculus : · how the body is The face I hand represented in the have large representation somatosensory area and the inthesensation e us primary motor area of # The face The hard and is occupying a very large ara face is more of the brain abendance in because of the complex movement Sensory (speak eat)olids , there and mortar As we grow , this to area becoming big accommodate the complexity of our need to speak # hand is also large ↓ involved in many activities Sensory homunculus Motor homunculus  The Association Areas Several large areas of the cerebral cortex that do not fit into the rigid categories of motor and sensory areas. function + - - , - > - integrationof the of Cerebral They are called&association areas because they receive and Cortex analyze signals simultaneously from multiple regions of both the motor and sensory cortices, as well as from subcortical structures. Association edit si Ares These areas make up about half of the cerebral cortex and are involved in higher brain functions (beyond motor, sensory, and language functions). analysis They perform mainly integrative functions thinking - for meaning they combine information from different brain regions to perform advanced tasks that motor, sensory, or language areas alone cannot accomplish.  The Association Areas Three main association areas: location Prefrontal Association Cortex (Front of Frontal Lobe): - Planning voluntary activity Decision-making and evaluating consequences ↑ Creativity and personality expression - ste is , blj -y g Working Memory: Temporarily stores and actively processes - - ~ information for reasoning and planning. Parietal–Temporal–Occipital Association Cortex (Interface of Three Lobes): / Hist &I Integrates sensory inputs (somatic, auditory, visual) for complex - - perception. - Language Processing: Connects Wernicke’s area to auditory and visual cortices. Limbic Association Cortex (Inner Temporal Lobe): Involved in: Motivation, emotion, and memory formation. -1 & 15 j - = ↳ & Dijd b· The Association Areas &  Speech and Language § Speaking and understanding language - are complex activities that involve several sensory, association and motor areas of the cortex. § In 97% of the population, these language areas are located in the left- hemisphere. The areas involved are: - for speech 1. The Broca’s area speaking Located in the left frontal lobe near the motor areas that control muscles for speaking (larynx, lips, mouth, respiratory system, and you listening when the wernids activate are will very be other accessory muscles of speech) undera wernickes ove That "steningng Responsible for speaking ability occipital - 2. The Wernicke’s area (a General Interpretative Area) Barietalen ↑ Located in the left cortex at the meeting of the parietal, temporal and occipital lobes. This area is concern with language understanding (spoken and written. 2nd -1  sing , Diancephalon 1 2014 # from = sensation , +1 = 2153 All Thalamus: exept of sensation of the body olfaction - Main relay station for sensory information going to - cerebral cortex as i , 811 - Hypothalamus Main regulator of homeostasis Control of ANS Autonomic NS - Regulation of eating and drinking - - - Control of body temperature ( & - Regulation of circadian rhythm (body internal clock) - -111 Regulation of emotion (together with the limbic > system) Epithalamus ⑳ · hormone Melatonin odi (Dina ( Contains pineal gland which produces hormone u pies, in as melatonin (release edio se during darkness and thought to promote sleeping) -  Brainstem (Midbrain, Pons, and Medulla) -+ I Receive sensory (afferent) information, and send out motor & (efferent) signals through paired nerves (cranial nerves). Contain important control centers6 for the ANS. interconnected collection % active very midbrain Contains a loosely organized interconnected I collection of E when you Paus neurons and fibers called the reticular formation which not sleep L Skill/l affects the level of consciousness or arousal depend ↳ The activities on how much active we are The medulla is involved in regulating the vital functional - controle Vital centers eg: functional HR Ø Cardiovascular center: heart rate, force of its - contraction and diameter of blood vessels = Ø The respiratory rhythmicity center (rate and rhythm of breathing) area) & Pons help control breathing (apneustic and pneumotaxic = Hemispheric laterization and Hemisphere Specialization § Although the brain is almost symmetrical on its right and left sides and shares performance of many functions, there are some anatomical and physiological differences between the two hemispheres. § Hemispheric Dominance: § Language Areas: Typically located in the left hemisphere, which is - also dominant for fine motor control. - § Handedness: Most people are right-handed due to left hemisphere control over right side body movements. - - s i · · -4 = &I - % left hemisphere right hemisphere  Hemispheric laterization and Hemisphere Specialization § Left Hemisphere Specialization: ·i t - § Excels in logical, analytical, sequential, and verbal tasks. - = - § & Key skills: Math, language, and philosophy. - - & § Processes information in a fine-detail, fragmentary way. side § Often associated with "thinkers". --1 - > § Right Hemisphere - Specialization: 04/10 % %1 · § Excels in old nonlanguage skills like spatial perception, artistic, and n musical talents. & § Views information in a big-picture, holistic way. - +1 Often associated with "creators". - - § § Cerebral Lateralization: § This specialization allows each hemisphere to excel in certain tasks, complementing one another through constant information sharing. corpus callosum ،‫يتيح هذا التخصص لكل نصف كرة أن يتفوق في مهام معينة‬.‫ويكمل كل منهما اآلخر من خالل تبادل املعلومات بشكل مستمر‬ Cerebellum normall moving The cerebellum, or “little brain”, is the second largest part of the brain Its main function is · I igh est Smooth coordination of skilled movement Balance and posture make normal rate ↳ can't stand , in you car , driving  Brain waves § Brain waves are rhythmic patterns of electrical activity in the brain, & generated by the synchronized firing of neurons & § Electrodes placed on the forehead O and scalp can be used to make a recording called an electroencephalogram (EEG). & § EEG are useful both in § studying normal brain functions, such as changes that occur during sleep, and in => § diagnosing a variety of brain disorders, such EEG is also utilized to determine if “life” is as epilepsy, tumors, trauma, hematomas, present, that is, to establish or confirm that metabolic abnormalities, sites of trauma, brain death has occurred. and degenerative diseases. -  Types of brain waves Summing waves of different frequency produces some characteristic, and diagnostic patterns. & - (frequency ( § Alpha waves (low frequency) are present much of the day when awake but disappear during sleep. § Beta (higher frequency) waves are present with - sensory input and mental activity when the nervous system is active during > much of the day. § Gamma waves (fastest with smallest - amplitude), associated with peak SWI's s concentration 5 19 § Theta (slower frequency) waves indicate /relaming / extreme relaxation, drowsiness or light when sleeping => sleep. - § Delta (greatest amplitude and slowest frequency) waves appear during deep * li is dreamless sleep especially - in adult y  L28 SOMATIC SENSATION Murtala Abubakar (Fall 2024) [email protected] Sultan Qaboos University © College of Medicine and Health Sciences T Objectives L28. SOMATIC SENSATION 1.Describe sensory receptors [Sense organ] and their classification. 2.Explain the generation of receptor potential that leads to action potential. 3.Describe the term stimulus and the four attributes of sensation. 4.Explain adaptation of sensory receptors. 5.Briefly describe two major ascending systems. 6.Describe that primary somato-sensory cortex. I  Somatic Sensation & 31/ , Somatic sensation refers to sensations from the skin, muscles, bones, tendons and joints. It is initiated by a variety of sensory receptors collectively called somatic receptors. These receptors respond to: Touch and pressure - - /Is Sense of posture and movement - Temperature :,St Pain ''YI 3  Sensory modalities § Each unique type of sensation (pain, touch, sight, sound..etc) is called ao sensory modality correct that massage neuron § Each sensory neuron usually carries information for only one - modality. ⑭ information modality ? one sensory Sensoryi § Sensory modalities are either General senses (somatic and modality Si wit sensory visceral) or special senses (vision, taste, hearing etc) - special general /: id somatic/visceral - / § Somatic senses include tactile sensations (touch, pressure, vibration, itch, and iii , tickle), thermal sensations (warm and cold), pain sensations, and proprioception (awareness of limb and joint position in space) abnormal position proprioception will set in you § Visceral senses provide information about conditions within internal organs - His % Y ·  Process of sensation - In I 2, / For a sensation to arise, four events typically occur: 1. Stimulation of the sensory receptor - an appropriate stimulus must occur within the receptor’s receptive field & &S 2. Transduction of the stimulus - a sensory receptor converts energy in a stimulus into a graded potential (generator potential/receptor potential). genera for graded by CNS Potential potential · 3. Generation of nerve impulses – occurs when the sum of graded potentials reach threshold in first-order neurons (the first neuron in a specific tract – in this case transmitted to the CNS from the PNS to the CNS) See n 4. Integration of sensory input – occurs when a convert it to and particular region of the CNS integrates a number (and Potential action even a variety) of sensory nerve impulses and results in conscious sensations or perceptions  Sensory receptors find came you overlak between Sensory receptors can be grouped into several classes based on o classefication e one structural and functional characteristics: und another 1. Microscopic structure – e.g. free nerve endings vs encapsulated endings a wherethereceptor 2. Location of the receptors and the origin of the stimuli that activate them 3. The type of stimulus detected (nociceptors for pain, mechanoreceptors for pressure, etc.) nociceptors - Pain mechanoreceptors - > Pressure 4. Mode of activation Sensory receptors based on E microscopic structure The differen  S Sensory receptors transform an external signal into a membrane potential the pain de feet complex => release neurotransmitter cause the  Sensory receptors based on location , -, - Exteroceptors, are located at or near the external surface E of the body and respond to external stimuli (e.g somatosensory receptors in the skin) - - Interoceptors (visceroceptors), which are located in blood vessels, organs, and muscles and produce impulses which usually are not consciously perceived % G ja Is JSI. Proprioceptors, which are located in muscles, tendons, joints, and the inner ear. They provide information about body position and movement of joints Sensory receptors based on type of stimulus 5-w/1  Sensory receptors based on mode of activation Mechanoreceptors, which are sensitive to deformation deformation > - Pressure Thermoreceptors, which detect changes in temperature Nociceptors, which respond to painful stimuli Photoreceptors, which are activated by photons of light Chemoreceptors, which detect chemicals in the mouth (taste), - nose (smell) and body fluids - Osmoreceptors, which detect the osmotic pressure of body fluids  Receptors and Stimuli Key Concept: Understanding how receptors respond to stimuli and initiate signaling in neurons. detected it when The stimulus , Overview: will changes thePermeability of sensory receptor's the membrane &' Wi - flow the ions (out/in] more easily A stimulus changes receptor permeability. > - to - This change leads to a graded receptor potential. Potential , ↳ mean : small change in membrane Types of Receptors depending the type of on ion mevement Specialized Ending of an Afferent Neuron - - jja1s Separate Receptor Cell closely associated with the neuron's &:410 peripheral ending. - :, w /1 F I W  Receptor Activation and Membrane Permeability Key Mechanism: Stimulation alters membrane permeability. membranepotential w ill Chr see - How it works: not voltage gated Usually opens channels allowing Na⁺ influx. > - Causes depolarization of the receptor membrane. when it get stimulation Note: Photoreceptors are an exception – they hyperpolarize on stimulation. in your eyes - The Receptor Potential ⑤ Definition: -1 The local depolarization that occurs upon stimulation. Characteristics: Graded Potential: Stronger stimulus → Greater permeability change → Larger receptor potential. Summation Possible: No refractory period, so can respond to successive ⑳ stimuli. period Receptor Potential doesn't have refractory · Successive stimuli  = Hi - there are "AD" & 11 ef "gi · so no massive influx of Nat Why No Action Potentials in the Receptor Region? That large enough is Reason: Few voltage-gated Na⁺ channels at the receptor.To P cause Action Implication: High threshold, so action potentials do not > make > - That occur at the receptor itself. - receptor have high threshold The Channel Types: Receptor channels respond to specific stimuli and are not voltage-gated Na⁺ channels. why the cell have to convert not voltage-gated Graded Potential channels - Action Potential ??? have to convent Conversion to Action Potentials potential into action Problem: Graded potentials can’t travel long distances. Solution: Receptor potential must be converted into action > potentials. Mechanism: Action potentials propagate along the afferent fiber for signal transmission to the central nervous system (CNS). Propagation Along the Afferent Fiber: The action potential travels along the afferent nerve fiber (the sensory neuron’s axon) towards the CNS without losing strength. Summary of Key Concepts Stimulus Response Pathway: Stimulus → Alters receptor permeability → Graded receptor potential → Conversion to action potential. Relevance: Essential for transmitting sensory information to the CNS.  Receptor potential activate the voltage gated non-voltage gated allows large of number Nat to inter The cell S - separate receptor Sensory like "Photoreceptor" [ first chemical gated Then voltage-gated  Adaptation in sensory receptors Adaptation: Sensory · darting queck a receptors often reduce receptor their response to a constant - stimulus over time. - Mechanism: The receptor ‫ ﺗﻘﻞ ﻗﺪرة‬:‫اﻵﻟﯿﺔ‬ potential decreases in - ،‫اﻟﻤﺴﺘﻘﺒﻞ ﻓﻲ اﻟﺴﻌﺔ‬ amplitude, leading to fewer ‫ﻣﻤﺎ ﯾﺆدي إﻟﻰ‬ - ‫اﻧﺨﻔﺎض ﻋﺪد‬ nerve impulses to the cerebral ‫ اﻟﻨﺒﻀﺎت اﻟﻌﺼﺒﯿﺔ إﻟﻰ‬cortex..‫اﻟﻘﺸﺮة اﻟﻤﺨﯿﺔ‬ ‫ ﯾﺘﻼﺷﻰ‬:‫ اﻟﻨﺘﯿﺠﺔ‬Result: Sensation perception ‫إدراك اﻹﺣﺴﺎس ﻋﻠﻰ‬ ‫اﻟﺮﻏﻢ ﻣﻦ وﺟﻮد‬ fades despite the continuous.‫ اﻟﻤﻨﺒﮫ ﺑﺸﻜﻞ ﻣﺴﺘﻤﺮ‬presence of the stimulus. Types of Receptors: Rapidly Adapting Receptors: Quick decrease in response, suited for detecting changes.· Slowly Adapting Receptors: : 175 - Maintain response longer, & suited for sustained sensations. Rapid vs. Slow receptor adaptation -  Somatic sensation Tactile sensations: (touch, pressure vibration, -- - itch tickle) Many types Thermal sensation: Free nerve endings, two types cold and warm - - receptors Pain sensation (nociception): Carried by free nerve endings, pain receptors Two types of pain: J jg 1. Fast pain (acute, pricking pain), medium diameter myelinated A fibers) ja 5, 7 2. Slow pain( chronic, burning, aching & throbbing) C fibers Proprioceptive sensation: sense of our position and movement 1. Muscle spindles I Sj 2. Golgi tendon bodies · - 3. Joint kinesthetic receptors · Primary somato-sensory areas What are the two major ascending pathways? convert the somatic sensations 1. The posterior column-medial lemniscus pathway. 2. The anterolateral (spinothalamic) pathway  The posterior column-medial lemniscus pathway touch, pressure vibration and proprioceptors column - - - Two white matter tracts : Posterior posterior tract (spinal cord) and medial- fasciculve lemniscus (mid brain). Gracile Caricate Gabischikule · a in from thalamus In the spinal cord, the posterior - to the somato sensory column are of two parts: Corten Cuniate fasciculus upper limb, 1 jo upper trunk and neck) Gracile fasciculus (lower limb and lower trunk) &1 from the medulla to medial lemniscus Axons of second order neurons to the thalamus Ja - cross to the cross in the medulla to the other opposite side fromSin a , side and enter the medial medulla lemniscus tract to ascend to the thalamus Axons of third order neurons ascend from thalamus to 1ry somatosensoty cortex.  The anterolateral (spinothalamic) pathway Pain, temperature, itch, tickle 1st order neuron: From receptors to spinal cord. 2nd order neurons: Cell bodies in the posterior gray horn. Synapse with 1st order neurons Axons cross to the other side and join spinothamaic tract. 3rd order neurons Synapse with axons of second order in thalamus (cell bodies in the thalamus). Project to primary cerebral cortex In the posterior root ganglion, they will cross to the opposite side immediately، they don't have to wait until they reach to the medulla  Somatic pathways Posterior column medial lemniscus Pathway- Spinothalamic - Da thwoy  L29 PHYSIOLOGY OF VISION Murtala Abubakar (Fall 2024) [email protected] Sultan Qaboos University © College of Medicine and Health Sciences L29: Objectives 1. Explain the optics of eye 2. Explain focal length of lens. 3. Explain formation of an image 4. Explain errors of refraction. 5. Discuss photoreceptors and their role in vision (rods and cones). 6. Discuss how ganglion cells axons form optic nerve. 7. Discuss information processing in primary visual cortex. 8. Describe color vision (three cone system). 9. Describe color blindness. The electromagnetic radiation Vision is possible because our photoreceptors are able to “catch” photons of electromagenetic radiation (energy in the form of waves that radiates from the sun). - The range of electromagnetic radiation is called electromagnetic spectrum. I I ↳ 00nm electromagnetic spectrum 700 nm Visible lights (400-700 nm wavelengths) exhibit in different colors depending on the wave length (400 is violet, 700 red). -. al reflect all color white / - don't reflect any Black Objects absorb and reflects colors colors -We see green because object absorbs all -I & - colors and reflects green = -We see white = reflects all wave lengths -We see black =absorbs all and does not reflect Distance between two consecutive waves  wi ↓ moved in light were are Refraction of light rays different media (fluid - Air) Normal image formation depends on: § refraction of light waves n a § accommodation of the lens %.% - § constriction of the pupil, and. - j1 § convergence of the two eyes defrection Refraction is the process of bending light rays. Both the cornea and the lens refract light rays, and both must be functioning in order to properly focus - light onto the right spot on the retina to produce clear vision -refraction of light wave # Cornea and lens. 2 accomodation refract light rays of the lens to focus onto the 3 constriction of. refina The Pupil 4. convergence of Two. eyes  21/ Focal Length of a Lens , 5 mi Parallel medium share of The focal length of a convex lens is the distance - from the lens to the point Diverging where parallel rays E converge to a single focal by changing Local length I point. Y mediumThe Parallel vs. Diverging Rays Parallel Rays: When rays change themediumthe convexity enter the lens parallel to each other, they converge at the focal point, defining the focal length. Diverging Rays (from a point source): Rays originating from a nearby point source enter the lens already diverging, so they focus further from the lens than parallel rays.  Physiologic-anatomy of the eye -g to change aght Contraction and relaxation of the iris of it muscle adjust the amount of light that increased enters the pupil & muscle · Iris muscle > - adjust amount of light the That enters the pupil Contraction and relaxation of the ciliary muscle External muscles adjust the Move eye ball s 51 > control the movement curvature of - of eyes lens (accommod ation) muscle ciliary - adjust the curvature of Lens contract and relax to it The Convexity so can or reduce increase the convexity · ,  Refraction and Image formation enj Accommodation: The ability to adjust the strength of the lens, i.e its shape which is regulated by ciliary muscle (under autonomic nervous system control). Parasympathetic stimulation & contracts the ciliary muscle causing the lens to round up more. for near Sympathetic relaxes the muscle and the lens flattens. for distant object object 58 When the eye is focusing on a close object, the lens become more curved causing greater refraction of the light rays. more convexity The lens elasticity is reduced with aging and can no longer assume spherical shape - required to accommodate for near vision resulting in prebyospia (old people require reading glasses) Presbyopia (ii) & %5 ; 5 g  Errors of refraction myogia htedness near : I ess nearsig es s gi i a i ab Myopia (nearsightedness) · as 28 , d Only close objects can be seen clearly: light rays Emmetropic: from distant objects are focused in front of the normal eye t retina. focal Point is front of the retina focus light on Correction involves the use of a concave the retina. use - (negative) lens.- =, Concave lens are curved towards inside don't react the retina Hyperopia (farsightedness) use Only distant objects can be seen clearly Light rays coming in from nearer objects are ia focused behind the retina. is 95I & % Focal Point behind the retina. - is Correction involves the use of a convex (positive) lens. behind the retina 2i - bisin Astigmatism (blurry vision) Convex lens is curved to outside. The cornea or the lens has irregular > - Lens refract incoming rays toward each other - curvature. shape Structure of the retina-the photoreceptors  Structure of photoreceptors § Specialized cells that transduce light rays into Rods (dim black and receptor potential. white vision) Has one type of § Two types: Rods and photoreceptor called cones. rhodopsin ↑ § Named for their outer segment shape-the distal end of the Cones (bright coloured photoreceptor next to vision) the pigmented layer. Three types, corresponding to the § Each retina has about 6 type of pigment they million cones and 120 contain: red, green or million rods. blue - rad in more - retina that B The 120 million · /6 million Cones ↳ a Cones  How do the ganglion cells axons form the optic nerve? § Ganglion cells are the final output neurons of the retina. § They receive visual information from bipolar · and amacrine cells, which process signals from the photoreceptors (rods and cones). Rod § The axons of the ganglion gene cells converge at a specific point in the retina called the optic disc (also known as the blind spot). - § At the optic disc, these axons bundle together to form the optic nerve. This is inactive Response of photopigment to light [ form which is - =19 : - type bound to opsin "Cis-retinal 8. I I 6 in photoreceptor cell Cones- This is the different § In darkness, retinal has a bent - between Red and comes but they have the shape called cis-retinal same process ·& trans-retinal 81 cis-retinal 65s %18 Bil is merization , isomerization § Absorption of a photon of light trans-retinal cis-refinal causes it to straighten into the - > trans-retinal form in a process called isomerization § Trans-retinal completely separates from the opsin; since the final products look colorless, this & part of the cycle is called Gos bleaching of photopigment trans-retinal cis-retinal from : o § An enzyme converts trans- by enzyme retinal→ cis-retinal All photopigments associated with vision § The cis-retinal regenerates the contain two parts: a glycoprotein known as photopigment opsin and a derivative of vitamin A called from vitamin "A retinal (light absorbing part) come  Light and dark adaptation § In daylight, regeneration of rhodopsin cannot keep up with the bleaching process, so rods contribute little to. & Rod daylight vision. is fast cones adation in but Rod dise is slow § In contrast, cone photopigments regenerate rapidly enough that some of the cis form is always present, even in ‫ ﺗﺘﺠﺪد اﻟﺼﺒﻐﺎت اﻟﻀﻮﺋﯿﺔ‬،‫ﻋﻠﻰ اﻟﻨﻘﯿﺾ ﻣﻦ ذﻟﻚ‬ very bright light ‫اﻟﻤﺨﺮوطﯿﺔ ﺑﺴﺮﻋﺔ ﻛﺎﻓﯿﺔ ﺑﺤﯿﺚ ﯾﻜﻮن ﺑﻌﺾ‬ ‫ ﺣﺘﻰ ﻓﻲ ﺿﻮء‬،‫اﻟﺸﻜﻞ اﻟﺴﯿﺲ ﻣﻮﺟﻮًدا داﺋًﻤﺎ‬ ‫ﺳﺎطﻊ ﻟﻠﻐﺎﯾﺔ‬ § As a consequence, light adaptation (from dark conditions  light conditions , visual system adjust to bright light) happens in seconds; dark adaptation (from light  dark) takes minutes to occur (up to 40 minutes to = fully adapt).  Information processing in primary visual cortex Thalamus is the first relay station in the visual pathway. Functions: Separates visual information from each - eye. is locatea lobe Relays processed data to the primary - ↳ visual cortex through optic radiations. Visual Cortex in the Occipital Lobe Receives input from the thalamus and further processes it. - Topographical Neural Mapping Retinal Maps in the thalamus and visual > cortex represent the retina point for point. Distortions in Mapping: 819 is located in wo The fovea, responsible for sharp vision, has a occipital node disproportionately large representation. ‫ڡﺴ'ٮﺮ اﻟﺮﺳﻢ‬$"‫ٮ‬ Peripheral retina areas have smaller :(Fovea) ‫اﻟ(ٮ*ڡﻄﺔ اﻟﻤﺮﻛزيﺔ‬ 4 ‫ٮﺼريﺔ‬-‫ى اﻟ*ڡﺸﺮة اﻟ‬D‫ٮ'ٮﺮ ڡ‬-‫ٮﺸكﻞ ﻛ‬- ‫ٮﻞ‬N‫ٮ*ﻤ‬ :‫اﻟﻤﺴﺎر‬ representation..‫ٮﻬﺎ ﻣﺴؤوﻟﺔ ﻋﻦ اﻟرؤيﺔ اﻟﺤﺎدة‬4‫ﻷ‬ ‫ٮواﺳﻄﺔ‬- ‫اﻟﻀﻮء ٮ 'ﻠ*ٮ*ڡﻂ‬ Cortical Resources for Vision ‫ٮﺸكﻞ أ*ڡﻞ‬- ‫ٮﻞ‬N‫ ٮ*ﻤ‬:‫ٮﺔ‬8‫ٮﻜ‬6‫اﻷﻃراف اﻟﺸ‬ ‫ٮﺮ‬-‫ٮ*ٮ*ڡﻞ ﻋ‬4' ‫ٮﻜ'ٮﺔ → ٮ‬-‫اﻟﺸ‬ Visual processing uses ~40% of the cortex: ‫ٮﻬﺎ أ*ڡﻞ د*ڡﺔ‬4‫أﻫﻤ'ٮﺔ ﻷ‬ ‫ٮﺮ‬-‫ٮﺼري → ٮ 'ﻌ‬-‫اﻟﻌﺼﺐ اﻟ‬ → ‫ٮﺼري‬-‫ٮﺪ اﻟ*ٮﺼﺎﻟﺐ اﻟ‬4‫ﻋ‬ Much higher compared to touch (8%) and → ‫ٮﺼري‬-‫ٮ'ٮﻞ اﻟ‬-‫ٮﺮ اﻟﺴ‬-‫ٮ 'ﻤﺮ ﻋ‬ hearing (3%). ‫ى اﻟﻤﻬﺎد → ٮ 'ﺮﺳﻞ‬D‫ڡ‬4 ‫ٮ 'ﻌﺎﻟﺞ‬ ‫ٮﺮ‬-‫ٮﺼريﺔ ﻋ‬-‫إﻟﻰ اﻟ*ڡﺸﺮة اﻟ‬ ‫ٮﺼريﺔ‬-‫اﻹﺷﻌﺎﻋﺎت اﻟ‬  Color Vision Color Vision and Photoreceptor Types Cones: Enable color vision with three types: Red cones (long wavelengths) -J & Green cones (medium wavelengths) & Blue cones (short wavelengths)-it's - n de sit Rods: Provide vision in shades of gray, important for low-light (night) conditions. Photopigments photopigment : Four types of photopigments: rods : Rhodopsin blue Rhodopsin in rods. cones : red , gran , One photopigment in each cone type (red, green, and blue). , cipio Shared component: Retinal. Rod and come has different Distinct component: Opsin, which L obsin from each others determines wavelength absorption. 01-41 , - -11-  How Photopigments Work Light Absorption and Wavelengths every photo pignant Each photopigment absorbs a specific wavelength range with a peak wavelength for maximum absorption. ss Rods: Broad range of absorption, / -N : detecting intensity but not color. - - Cones: Overlapping absorption ranges 342n allow multiple cones to respond to the · S i - same wavelength but to different = s extents. ↑ Color Vision Mechanism The brain compares responses from red, , and blue cones to distinguish colors in daylight. Example: Equal activation of red and - - green cones creates a yellow green perception. - * - yellow Vision in Shades of Gray Rods do not differentiate o wavelengths; they only detect intensity. - Night vision relies on rods, resulting in monochrome perception.  Color Perception mechanism Color Perception Mechanism Cone types (red, , blue) transmit signals via parallel pathways to the brain. The primary visual cortex combines and processes these inputs to generate color perception. What is Color Blindness? : /11 Occurs when an individual lacks one Die type of cone, resulting in color vision - Ga based on only two cone types instead & 189 of three. Effects: Difficulty distinguishing certain colors. Reduced ability to perceive the variety of colors. T Example: Red–Green Color Blindness Individuals cannot differentiate red from green. Compensate by relying on brightness or position (e.g., traffic lights).  focal Point - - o - - astigmatisme frontabove of the the retina(concave retire (criven hyperopia -o emmetropic - regular -  cell cell Bipolar cell o a macrine - gangilian optic a nerve ↳ optic u gagile > - - - - e "N 54 ijd\us - -  L30 PHYSIOLOGY OF HEARING AND EQUILIBRIUM Murtala Abubakar (Fall 2024) [email protected] Sultan Qaboos University © College of Medicine and Health Sciences L30: Objectives 1. Explain how the middle ear converts pressure waves in the air into fluid vibration in the inner ear. 2. Discuss the role of the hair cells in the organ of Corti (mechano-electric transduction). 3. Briefly describe the pitch discrimination, loudness and direction of sound. 4. Describe different types of deafness. 5. Describe the structure of the vestibular apparatus and the vestibular receptors 6. Discus the role of the macula in detection of gravitational forces and of crista in in detection of angular acceleration 7. Describe the vestibular pathway to the cerebral cortex and cerebellum  Hearing Parts of the Ear: -A - 1 The ear consists of three main parts: 1. External Ear 2. Middle Ear 3. Inner Ear Functions: m The external and middle ear: - St M = 1 - Transmit airborne sound waves to - Ha : / g14d the fluid-filled inner ear. Amplify sound energy. -all jij · , The inner ear: Houses two sensory systems: Cochlea: Converts sound waves into nerve impulses for hearing. Vestibular Apparatus: Maintains the sense of equilibrium.  Equalizing Pressure on the Tympanic Membrane - For the membrane to move freely, air pressure on - both sides must be equal. easie - External pressure reaches the membrane via the ear canal.> - will i - Internal pressure is connectwitsign , regulated by the eustachian ‫ﯾﺘﻢ ﺗﻨﻈﯿﻢ اﻟﻀﻐﻂ اﻟﺪاﺧﻠﻲ ﻋﻦ‬ tube, which connects the ‫ اﻟﺘﻲ‬،‫طﺮﯾﻖ ﻗﻨﺎة اﺳﺘﺎﻛﯿﻮس‬ ‫ﺗﺮﺑﻂ اﻷذن اﻟﻮﺳﻄﻰ ﺑﺎﻟﺒﻠﻌﻮم‬ middle ear to the pharynx. -  The Middle Ear and Sound Transmission 1. Role of the Middle Ear The middle ear transfers membrane * Basilar jligye vibrations from the tympanic membrane (eardrum) to the inner ear & fluid. no complexity offluid - Vibrations are conveyed by a movable chain of three small - bones (ossicles): Malleus: Attached to the tympanic - - membrane. Incus: Middle bone in the chain. Stapes: Attached to the oval - window (entrance to the cochlea). -  The Middle Ear and Sound Transmission 2. Amplification of Sound T Two mechanisms amplify sound pressure: a. Surface Area Difference: The tympanic membrane is much larger than the oval window. ‫ٮﺚ‬5‫ﻌﻂ ﺣ‬1‫ ويﺆدي ﻫﺬا إﻟﻰ زيﺎدة اﻟﻀ‬This increases pressure as force is.‫ﻌﺮ‬1‫ڡﻮة ﻋﲆ ﻣﺴﺎﺣﺔ أﺻ‬8‫تﺮﻛﺰ اﻟ‬8‫ٮ‬ O concentrated on a smaller area. b. Lever Action of Ossicles: The bones act as levers, further - increasing the force applied to the oval window. Result: The pressure at the oval window is 20 times greater than if sound waves struck it directly. This pressure is sufficient to move the cochlear fluid, enabling ossicle hearing. Y mallers 1 stages oral incus al winde  The Middle Ear and Sound Transmission 3. Sound Transmission to the Inner Ear Vibrations of the ossicles at the same frequency as the tympanic membrane produce pressure waves in the cochlear fluid. Basilne The amplified pressure compensates for the greater resistance of fluid compared to air, enabling effective sound transmission. action Potential All the Segment are Stimulus : The sound The  The Cochlea and the Organ of Corti -1 -n -54 The cochlea is the pea-sized, snail- shaped portion of the inner ear responsible for hearing. The cochlea % is divided 100 into three - longitudinal compartments: Scala Vestibuli (upper compartment): Follows the inner contour of the cochlea. Contains perilymph fluid. Scala Tympani (lower compartment): sacal Vestibuli oval window ↓ Follows the outer contour of the cochlea. Contains perilymph fluid. Scala media Cochlear Duct (Scala Media) (middle ( compartment): -51j05 wi sensory organ = Tunnels through the center of the cochlea. of hearing E Contains endolymph, a slightly different Sacal fluid. Tympan ; Fluid Continuity: At the cochlear duct's tip, the helicotrema ‫ ﯾﺮﺑﻂ اﻟﻤﻐﺰل اﻟﺤﻠﺰوﻧﻲ ﺑﯿﻦ ﺷﻮﻛﺔ‬،‫ﻋﻨﺪ طﺮف اﻟﻘﻨﺎة اﻟﻘﻮﻗﻌﯿﺔ‬ connects the scala vestibuli and scala tympani. ‫اﻟﺪھﻠﯿﺰ وﺷﻮﻛﺔ اﻟﻄﺒﻠﺔ‬  of Role of hair cells in the organ of corti · sensory hearing 1. Overview of Organ of Corti: Located on the basilar membrane of the cochlea. Contains 15,000 hair cells in each Receptor cochlea, arranged in four rows: convert the 1. Inner Hair Cells (1 row): signal E 2. sound to action Responsible for hearing. - Potential Outer Hair Cells (3 rows): Sig fest jus Enhance sound detection. - e ⑳ Stereocilia: Stereocilia alt with tectorial membrain & Hair cells are topped with stereocilia, actin-stiffened microvilli arranged in a E i bi staircaselike pattern.. Stereocilia interact with the tectorial High intensity sounds waves cause large membrane, an overhanging structure. vibrations, higher frequency of nerve fixed the Hair Ced to impulses and may stimulate a larger number of hair cells  How Hair Cells Transduce Sound 2. Sound Wave Transmission: ossicles Y ↓ I stage Stapes action creates pressure ↓ em mallers incus waves in the cochlear fluid. Basilar membrane movement · jijel vibrates the Organ of Corti. Cortis r Stereocilia movement caused by The Stereocilia bound to tectorial basilar membrane deflection membrane then there is mechanical stimulus relative to the tectorial membrane: causes back-and-forth # The louder the mechanical deformation of the sound - caused hairs which alternately opens by the more vibration and closes mechanically gated channels cation channels open Nat mechanical gated in the Basilar membrane that caused more action propagation of resulting in alternating Potential depolarizing and hyperpolarizing potential changes—the receptor Potenial potential creat action  mallers - in cas - stapes Pathway for sound transduction. Oval window * vibration of Basilar membrane cause birding the hair cell with tectorial membrane  Function of Hair Cells sound vibration - electrical 1. Inner hair cells signals · Primary Role: Transform sound vibrations into electrical signals for hearing. Mechanism: -? / / o5 9 Oscillations of the basilar membrane deform stereocilia, producing receptor potentials. &+1 > Inner hair cells release glutamate, stimulating afferent auditory nerve - fibers. Inner hair cells are the real sensory receptors of hearing. inner 2. Outer Hair Cells motion of basilar membrane o improving They amplify the hair cell stimulation Electromotility: Outer hair cells actively change length: ↓ Shorten during depolarization. -- - Lengthen during hyperpolarization. - & This amplifies the motion of the basilar membrane, improving inner hair cell stimulation..‫ﺗﻌﺰﯾﺰ ﺣﺴﺎﺳﯿﺔ ﺷﺪة اﻟﺼﻮت وﺗﻤﯿﯿﺰ درﺟﺔ اﻟﺼﻮت‬ Role: Enhance sound intensity sensitivity and pitch discrimination. -  - - Pitch Discrimination and the Basilar Membrane wi or 1. Pitch Discrimination? The ability to distinguish among various frequencies of incoming sound waves. Depends on: & The shape and properties of the basilar membrane. 2. Structure of the Basilar Membrane 12, 5 Gradients of the Membrane: & & 1. Narrow and Stiff near the oval window: Responds best to high- -19 frequency sounds. ja 2. Wide and Flexible near the helicotrema: Responds best to low-frequency sounds. Different regions vibrate maximally at specific frequencies.  Loudness Discrimination 1. What is Loudness Discrimination? · ois/i The ability to distinguish sound intensity (loudness). Determined by the amplitude of vibration caused by sound waves. 2. How Loudness is Detected movement of basal member & Amplitude and Vibration: - Louder sounds cause greater vibration amplitude of the tympanic membrane, moving ↓ ↓ ↓ vigorously. it more This translates to greater basilar membrane movement in the cells region of peak responsiveness. & causing binding to the hair Cstereocilia ( Effect on Hair Cells: Greater movement of the basilar membrane causes more significant bending of hair cells' stereocilia in that region. The CNS interprets greater hair bending as a louder sound. & es of wil e No,  Loudness vs. Pitch Discrimination Loudness Discrimination: & Depends on "how much" the basilar membrane vibrates. stiff / Narrow if it in the oral window - night ,frequest Pitch Discrimination: ↓ if it helicotrema in low frequeng- Depends on "where" the basilar membrane => vibrates maximally. which Per t is stimula night and low  Deafness or Hearing Loss § Loss of hearing that may be: - S § Temporary or permanent. Es &2 § Partial or complete. § Types of Deafness: i gol 1. Conductive Deafness: & will syst § Sound waves are not -Idl - conducted through the external or middle ear to the inner ear. 2. Sensorineural Deafness: -15:d Jos § Sound waves reach the b 501) , inner ear but are not - = - , 51 converted into nerve signals.  Physiology of equilibrium to be in normal your ability ↳ Equilibrium is another function of the position have antigravity muscles inner ear we vestibular apparatus Is controlled by thee vestibular apparatus (the saccule and utricle of the vestibule, - and the 3 semicircular canals) - There are two kinds of equilibrium- Balance:- -j/5) - 19. 81) : 1. Static equilibrium: the maintenance of the position of the body (mainly the head) relative to the force= - of gravity. 2. Dynamic equilibrium: is the maintenance of body position (mainly the head) in response to sudden is - Jus jjt Contains endolymph 7- scala media movements such as rotation, and perilymph like cocklea due - / Vestibuli acceleration, and deceleration. - cochlea ↑ scala Scala Tympani  - Static equilibrium & Is controlled by the sensory hairs within the macula of the utricle and saccule Saccule utricle ,& - macular - nin- The walls of utricle and saccule contain & : , Es a thickened area called: maculae Jil, carbonate crystals (receptors for static equilibrium) The maculae consists of hair cells (hair %1 01 bundle) with many stereocilia and one kinocilium. otolithic memram An otolithic membrane (thick ↓ receptor cells jelatenous), studded with dense calcium calcium carbonate crystals (otoliths) Carbonat crystals The bending of hair cells causes otoliths Vestibular apparatus depolarisation and repolarisation Succule & utricle (transduction) leading to nerve maculae impulses. is hair Stereocilia cells ① Kinocilium and otolithic membrane consect of "otolithkin Carbon crystal Static equilibrium § An otolithic membrane and otoliths responds to gravity when head position is changed. Slides over hair cells. § This movement opens - transduction channels in the hair cells, producing local potentials, movement of and release of the hair cel generation of neurotransmitter. The Action Potential § Action potential in the vestibular branch of vestibulocochlear nerve.  canals Dynamic equilibrium 51 semicircular ampulla § Dynamic equilibrium is controlled by the sensory hairs within the ampulla of the 3 important semicircular canals (lie at right angle to more E one another in three planes. This position permits detection of rotational & acceleration o