KNES259 Physiology Final PDF

259 Physiology Final Nervous System- Membrane Potentials and Action Potentials Cell Communication - Endocrine (hormones)- chemical messages, longer lasting, more widespread - Nervous- communicate fast with the cells, tissues, organs, and systems they control Neural Communication...

259 Physiology Final Nervous System- Membrane Potentials and Action Potentials Cell Communication - Endocrine (hormones)- chemical messages, longer lasting, more widespread - Nervous- communicate fast with the cells, tissues, organs, and systems they control Neural Communication - Nerve and muscles are excitable tissues- they can undergo rapid changes in membrane potentials (which is critical to the function of the neurons and muscles) Neuron- single nerve cell - Composition o Dendritic region- increase surface area for receiving signals, sends signal towards cell body (neuron input zone) o Cell body- house nucleus and organelles o Axon hillock- where axon meets cell body, neuron’s trigger zone o Axon- nerve “fibre”, conducts impulses away from the cell body o Axon terminals- synapses with other neurons of eGector organ, releases chemical messengers Nerve- bundle of neurons Kinesins- carry nutrients, enzymes, organelles away from the cell body Dyneins- carries recycled vesicles, chemical messengers back towards the cell body Microtubule- “railway” Membrane Potential - Plasma membrane of all living cells has a membrane potential (polarized electrically) - Separation of opposite charges across plasma membrane - Due to diGerences in concentration and permeability of key ions Nerve and Muscle Cells - Excitable cells- can produce rapid transient changes in their membrane potential Resting Membrane Potential - Constant in cells of non-excitable tissues and excitable tissues at rest - 1 electrode in cell, 1 electrode outside (diGerence between the two)  - Na+ and K+ gates are closed - Na+/K+ working Movement of Ions - Permeability- controlled by channels - Electrical Gradient- positive charge is drawn to negative - Concentration Gradient- moves from high to low concentration Nest Equation- describes equilibrium potential for an ion (Na+= 60mV, K+= -84mV) Maintenance of Membrane Potential - Impermeable membrane - Na+/ K+ ATPase pump - Increased permeability to K+ (leaks out) - Anions inside membrane Membrane States - Polarization- state when membrane potential is other than 0mV - Depolarization- membrane becomes less polarized than at rest- Na+ rushes in +30 mV - Repolarization- membrane returns to resting potential after a depolarization- K+ rushes out (Na+ gate is closed) - Hyperpolarization- membrane becomes more polarized than at rest- K+ is slow to close -80mV (overshoot) Neural Communication - Graded Potential- serve as short distance signals - Action Potentials- serve as long-distance signals, once initiated action potentials are conducted throughout a nerve fibre Graded Potentials - Initiated by mechanical stimulus, chemical stimulus, electrical stimulus in dendrites (receptor cells) - Local- die away quickly - Can be added together to become larger in amplitude - Amplitude depends on strength of stimulus - Can summate - Vary in size - Can be excitatory or inhibitory (depolarizing or hyperpolarizing  - No refractory period (temporal eGect) - Ex. Postsynaptic potentials, receptor potentials, end-plate potentials, pacemaker potentials, slow-wave potentials Action Potentials - Brief rapid, large (100mV) changes in membrane potential o Potential actually reverses o Na+ and K+ involved - Do not decrease in strength as they travel from their site of initiation - Ion changes produce the phase of action potential (resting potential, depolarization, repolarization, hyperpolarization) - Resting RMP (-70mV) - Graded potentials reach threshold (-55mV) which triggers and action potential - Sodium is pumped into the extracellular fluid - Potassium is pumped into the intracellular fluid - All-or-None principle- neurons either reach threshold and produce a full-sized action potential or no action potential is produced at all - Refractory Periods- Na+ gates need time to rest (ions need time to rest), overshoot of K+ gates causes the cell to hyperpolarize- requires greater graded potential to reach threshold o Absolute Refractory Period- when a second action potential is not possible even with a large stimulus o Relative Refractory Period- a second action potential is possible when a greater than normal stimulus - Self-propagating- an impulse in one region is enough of a disturbance to cause the neighbouring regions to reach threshold and trigger an action potential - Uni-directional movement- refractory period cause the impulse to move inone direction only State Ions Resting Na+ out, K+ in Depolarization Na+ moves in, K+ stays in Repolarization Na+ still in, K+ moves out Refractory Period (ions reset) Na+ moves out, K+ moves in (overshoot of K+) Propagation - Contiguous Conduction- conduction in unmyelinated fibres, action potential spreads along every portion of the membrane  - Saltatory Conduction- rapid conduction in myelinated fibres, impulses jumps over section of the fibre covered with insulating myelin, ~50 times faster - Myelin- fatty insulator, primarily composed of lipid (formed by oligodendrocytes in CNS and formed by Schwann cells in PNS), leaves exposed nodes - Multiple Sclerosis- loss of myelin, decreased speed of impulses, loss of coordination in muscles and nerves Nerve Conduction - Depends on neuron diameter, myelination, temperature Regeneration of Nerve Fibres - Regeneration of nerve fibres depends on its location - Schwann cells in PNS guide the regeneration of cut axons - Fibres in CNS myelinated by oligodendrocytes do not have regenerative ability o Oligodendrocytes inhibit regeneration of cut central axons Synapses- junction between 2 neurons, primary mean by which one neuron directly interacts with another Convergence- many neurons input onto one Divergence- one neuron synapse with many Anatomy of a Synapse - Presynaptic Neuron- conducts action potential toward synapse - Synaptic Knob- contains synaptic vesicles - Synaptic Vesicles- stores neurotransmitter (carries signal across a synapse) - Post Synaptic Neuron- neuron whose action potentials are propagated away from the synapse - Synaptic Cleft- space between the presynaptic and postsynaptic neuron Synapse - Action potential arrives at terminal end - Voltage-gated Ca2+ open - Ca2+ moves into knob - Triggers release of neurotransmitter (Ca2+ binds to synaptotagmin- stimulates SNARE proteins (ensnare vesicle)) - Neurotransmitter migrates across synapse - Binds to receptor site o Opens ion gate  o Triggers graded potential - Signals at synapse either excites or inhibits the postsynaptic neuron o Excitatory synapses (Na+ or ion gates) o Inhibitory synapses (K+ gates or Cl- gates) Post-Synaptic Membrane - Actives ionotropic receptors- actual ion channels Or - Metabotropic receptors- 2nd messenger activation of channel - Synaptic delay-.2 to.5 msec Size of Post-Synaptic Potential - Depends on: o Calcium levels (fatigue) o Neurotransmitters levels o Desensitization/ hypersensitization o Pre-synaptic inhibition or facilitation Spatial Summation- summation of many EPSP’s occurs at diGerent locations on the dendrites at the same time Temporal Summation- summation of many EPE’s occurring at the same location over a very short period of time Pre-Synaptic Facilitation/ Inhibition- opiates, neuron A release neurotransmitter that can either increase or decrease release from neuron B Neurotransmitters - Vary from synapse to synapse - Same neurotransmitter is always released at a particular synapse o Quickly removed from the synaptic cleft - Common neurotransmitters o Acetylcholine § Cholinergic receptors Parasympathetic system/ muscle Muscarinic vs nicotinic receptors (agonist) broken down by acetylcholinesterase and recycled o Sarin- inhibits this enzyme Alzheimer’s Disease  o Dopamine/ serotonin o Norepinephrine/ epinephrine o Histamine o Glutamate o Gamma-aminobutyric acid (GABA) Neuropeptides - Large molecules consisting of from 2 to 40 amino acids - Neuropeptides o Substance P (pain) o Enkephalins/ Endorphins o Dynorphins o Hypothalamic releasing and inhibiting hormones o Angiotensin II o Cholecystokinin Catecholamines - Epinephrine/ norepinephrine o AGect consciousness, mood, attention o BP, HR - Adrenergic/ Noradrenergic Receptors o Broken down by MAO (monoamine oxidase) o MAO inhibitors increase epi levels in synapse § Anti-depressant Serotonin - From tryptophan/ modulates (slow onset) - Excitatory on muscle control - Inhibitory on sensory mediation - Mood, anxiety, wakefulness - Block reuptake with Paxil (anti-depressant) o Also LSD - Parkinson’s Disease o Decrease release of L-dopa from basal nuclei o Tremors/ muscle rigidity Synaptic Drug Interactions - Possible drug actions  o Altering the synthesis, axonal transport, storage, or release of a neurotransmitter o Modifying neurotransmitter interaction with the postsynaptic receptor o Influencing neurotransmitter reuptake or destruction o Replacing a deficient neurotransmitter with a substitute transmitter Possible drug eNects on synaptic eNectiveness - Release and degradation of neurotransmitter inside the axon terminal - Increased neurotransmitter release into the synapse - Prevention of neurotransmitter release into the synapse - Inhibition of synthesis of the neurotransmitter - Reduced reuptake of the neurotransmitter from the synapse - Reduced degradation of the neurotransmitter in the synapse - Agonists (evoke same response as neurotransmitter) or antagonists (block response to neurotransmitter) can occupy the receptors - Reduced biochemical response inside the dendrite Drug Interactions - Agonist- mimic neurotransmitters when they bind (morphine (opiates)) - Antagonists- bind but don’t activate receptor- blocks site (atropine (ach)) Drugs that alter synaptic transmission - Cocaine o Blocks reuptake of neurotransmitter dopamine at presynaptic terminals - Strychnine o Competes with inhibitory neurotransmitter glycine at postsynaptic receptor site § Convulsions Increasing Extracellular K+ - Eg. KCl injection o Concentration gradient of K+ across the cell membrane is reduced § Less K+ flows out of the cell through the “leak” current channels § Intracellular concentration rises § Membrane potential closer to threshold o Will depolarizes the neuron § More likely to undergo an action potential o In the brain  § Likely to produce seizures § Hypothesized cause of seizure activity in some forms of epilepsy o Astrocyte usually “absorb” excess potassium from the extracellular space by way of potassium channels in the membranes Curare - South and central America o Paralyzing poison used on arrows - Competes with Ach at nicotinic Ach receptors o Inhibits action of Ach at the neuromuscular junction o Causes muscle weakness/ paralysis o Eventual death by asphyxiation § Paralysis of diaphragm Tetrodotoxin (TTX) - Poison from puGerfish o Also in some newts, octopus and sea stars (made by symbiotic bacteria) o Ingestion, inhalation, injection or open skin - Inhibits voltage sensitive Na+ gates o No depolarization possible o Loss of sensation, paralysis of voluntary muscles (diaphragm), stopping breathing Box Jellyfish Toxin - Sea wasp o Toxin to kill 60 people - Cells become porous o Allowed potassium leakage § Hyperkalemia § Lose K+ gradient for neural cells Cardiovascular collapse Death as quickly as within 2 to 5 minutes General Anaesthetic- Sevoflurane - AGects K+ leak channels that help maintain the resting membrane potential - This will hyperpolarize the membrane o Harder to reach threshold § Less likely to send action potentials  - Inhalation anaesthetics prefer to target neurons in the brainstem that control consciousness and respiration (Reticular Activating System and sleep) o Reduces level of consciousness and respiratory rate o Entire CNS is depressed- decrease muscle action, reduced heart rate Lidocaine- Local Anaesthetic (Xylocaine) - Blocks voltage-sensitive Na+ channels in sensory neurons o No action potentials § Numbing o Also blocks in cardiac motor neurons § Raises threshold § Reduces arrythmias DDT - In insects- acts to open Na+ gates o Over-firing o Spasms and death - Over-use in humans o Stimulates estrogens § Lower sperm count/ miscarriages o Cancer-causing o Neural degradation Central Nervous System ANerent Neurons - Ascending - Dendrites in periphery - Terminal ends in CNS ENerent Neurons - Descending - Dendrites in CNS - Terminal ends in periphery - Only have autonomic nerves have synapses outside the CNS o Ganglia Interneurons - 99% of all neurons Glial Cells - Make up 90% of CNS cells and ~1/2 the volume - Support cells o Physical and metabolic support for the CNS - Types: o Astrocytes § Hold neurons in place § General maintenance of space Metabolic support and repair § Helps form blood-brain barrier o Microglia § Immune- protect from pathogens o Ependymal Cells § Ciliated epithelial membrane lining ventricles § Secrete cerebrospinal fluid Shock absorption Nutrients § Cerebrospinal Final made in choroid plexus Flows through ventricles Into sub-arachnoid space Absorbed- arachnoid villi o Oligodendrocytes - Myelin o Increased conduction velocity o Secreted by Schwann cells in PNS o Secreted by oligodendrocytes in CNS Electroencephalogram- external recording of brain wave patterns (summation of action potential, EPSP’s, IPSP’s Brain Waves - Alpha o Lower frequency o Relaxed state (eyes closed) - Beta o Higher frequency o Alert and concentrating - Theta  o Light sleep - Delta o Deep sleep Sleep Patterns - Alternate between non-REM and REM sleep o Stage 1 à4 à 1 NR o Then REM sleep o Back to Non-REM - Non-REM sleep (4 stages) o Rest and repair o Thera and delta waves - REM sleep o Dream state o Rapid eye movement o Problem solving o Reverse learning o Elevated breathing heart rate o Beta waves Association areas- link sensory input and motor output areas Speech Areas - Broca’s area o Speech - Wernicke’s area o Speech and comprehension - Dyslexia o Poor connections between visual and language areas o Or between areas Limbic System - Emotion, learning and memory - Hippocampus o Learning and memory - Inputs to hypothalamus Short Term vs Long Term Memory - Short term  o Limited capacity o Fast retrieval o Temporary neural trace (minutes to hours) - Long term o Huge capacity o Slower retrieval o Permanent neural trace § Days to years Transfer from Short Term Memory to Long term Memory - Relates to past events and memories - Emotional response related to memory - Repetition - Sleep - Exercise and diet Memory - Habituation o Decreased response to repeated indiGerent stimuli o Decreased calcium at synapse - Sensitization o Increased response to mild stimuli o More calcium released at synapse o Ie. Emotional response involved Spinal Cord - Two vital functions o Neuronal link between brain and PNS o Integrating center for spinal reflexes The Spinal Cord Cross-Section - Sensory input via the dorsal root - Motor output via the ventral roots Gray Matter - Unmyelinated nerve cell bodies - Dendrites - Axon terminals White Matter - Myelinated axons - Contains very few cell bodies Spinal Reflexes - Protective reflexes o Faster when brain is not involved § After-thought message only o Often monosynaptic Autonomic Reflexes- some visceral reflexes are spinal reflexes Skeletal Muscle Reflexes - Proprioceptors o Golgi tendon organ and muscle spindle o Located in muscle, joints and ligaments § Carry input to CNS - Alpha motor neurons o Carry input to muscle Stretch Reflex - Stretch of receptor sends action potentials up sensory neuron o Increases firing of motor neuron o Reflex contraction Golgi Tendon Organ - Stretch receptor in tendon - Prevents over-stretch of the tendon o Triggers reflex relaxation in the muscle o Ie. Sudden fail of a muscle Withdrawal Reflex - Triggered by pain receptor o Synapses with motor neurons to flexors § Contract to withdraw o Synapses with motor neurons to extensors § Inhibits - Simultaneous with Crossed Extensor Reflex  o Opposite side § Contraction of extensors § Inhibition of flexors Autonomic Nervous System - Homeostasis is a dynamic balance between the autonomic branches - Two antagonistic branches o Autonomic reflexes o Control of cardiac and smooth muscle, and glands in homeostasis - Sympathetic nervous system o Fight or flight o Adrenalin rush o Thoracic and lumbar regions o Increased heart rate and contractility o Increased breathing rate and depth o Blood vessel eGects § Vasoconstriction to non-essentials (ie. Gut) § Vasodilation to muscle o Decrease gut activity and secretions o Decrease kidney function and urine output o Pupil dilation - Parasympathetic nervous system o Rest and digest o Cranio-sacral o Decrease heart rate and contractility o Decrease breathing rate and depth o No eGect on blood vessels o Increase gut activity and secretions o Increase kidney function and urine output o Pupil constriction The Hypothalamus, Pons and Medulla - Coordination of homeostatic response o Autonomic o Endocrine o Behavioral Autonomic Branches  - Sympathetic neurons o Short pre-ganglionic neurons o Long post-gang ionic neurons o Ach at ganglion, Epi at eGector organ - Parasympathetic neurons o Long pre-ganglionic neurons o Short post-ganglionic neurons o Ach at ganglion and eGector organ Cholinergic Receptors - Bind Acetylcholine - Nicotinic receptors found at the o Sympathetic ganglia o Parasympathetic ganglia o Neuromuscular junction (skeletal muscle) - Muscarinic receptors found at the o Parasympathetic eGector organs Adrenergic Receptors - Alpha 1 (epi and norepi) o Vasoconstricts blood vessels- heart, muscle, gut, kidneys, skin o Increased sweat gland secretion/ goose bumps o Dilates pupils o Propels urine - Alpha 2 (epi and norepi) o Inhibits insulin release/ constricts gut sphincters o Decreases norepinephrine release - Beta 1 (epi and norepi) o Increases heart rate and contractility o Increased renin from kidney - Beta 2 (only epi) o Vasodilates blood vessels- muscle, heart o Bronchodilation o Relaxes gut wall and uterus - Beta 3 o Lipolysis- fat tissue o Relaxes bladder Sensory Physiology Sense General senses- touch, temperature, pressure, pain, itch Special Senses- vision hearing, smell, taste Visceral Senses- pH, osmolarity, chemoreceptors Proprioceptors- stretch, position, over-contraction Sensory Receptors Two types - Specialized endings of a neuron (touch) - Separate cell that signals to aGerent neuron (rods and cones) Receptor Field - Area of skin that a sensory receptor innervates - Size will vary Characteristics of Sensory Receptors - Modality o Receptor type § Each respond to one type of stimulus only (except pain) Chemoreceptors Mechanoreceptors Proprioceptors thermoreceptors - Intensity o Coded by frequency § Since action potentials are all-or-none o Higher stimulus will also stimulate more fibres - Adaptation o When the neuron stops sending action potentials in response to a continuous stimulus o Phasic or fast-adapting receptors § Respond to change in stimulus (temp, touch, smell) o Tonic or slow-adapting receptors  § Continues to send action potentials in response to constant stimulus (pain, vison, proprioceptors (non-adapting)) - Localization or acuity o Ability to distinguish between stimulus points o Depends on § Receptor field size § Receptor field overlap § Area of representation in cortex § Lateral inhibition Receptor Field ENect - If receptor field size increases o Acuity or ability to localize decreases (back less sensitive than fingers) o With more overlap of receptor fields- acuity increases (fingers) Area of Representation in Cortex - Greater area of representation o Greater ability to localize (face and fingers) Lateral Inhibition - Receptor fields continuous - Increases “contrast”- so increases acuity Pain - Primarily a protective mechanism o Behavioural reposes and emotional reactions o Memory helps us avoid harmful events in future - Subjective perception o Influenced by other past experiences - Nociceptors o Do not adapt to sustained stimulation - Cytokines will lower nociceptor’s threshold o Greatly enhances receptor response to noxious stimuli o Hyper-algesia o Ie. Prostaglandins, bradykinin, histamines Nociceptors - Mechanical nociceptors  o Respond to damage such as cutting, crushing, or pinching - Thermal Nociceptors o Respond to temperature extremes - Polymodal Nociceptors o Respond equally to all kinds of damaging stimuli Fast Pain Slow Pain Occurs on stimulation of mechanical and Occurs on stimulation of polymodal thermal nociceptors nociceptors Carried by large myelinated A-delta fibers Carried by small, unmyelinated C fibers Produces sharp, prickling sensation Produces dull, aching, burning sensation Easily localized Poorly localized Occurs first Occurs second, persists for longer time, more unpleasant Pain - Two best known pain neurotransmitters o Substance P § Activates ascending pathways o Glutamate § Major excitatory neurotransmitter o Brain has built in analgesic system § Suppresses transmission in pain pathways § Depends on presence of opiate receptors Endogenous opiates- endorphins, enkephalins, dynorphin Eye Structures - Schleroid o White of the eye o Continuous with cornea - Choroid o Blood vessel layer o Iris and ciliary body - Retina o Back and sides only o Photoreceptors Vitreous and Aqueous Humour - Vitreous humour o Gelatinous  o Maintains shape of eye - Aqueous humour o Provides nutrients to cornea o 5mL/day Glaucoma - Blocked drainage duct o Aqueous humour fluid builds o Build-up of pressure o Can damage nerve Iris and Pupil - Pupil o Eye opening for light - Iris o Colour of the eye o Controls amount of light entering eye o Circular muscles constrict pupil o Radial muscles dilate pupil - Convex structures of eye produce convergence of diverging light rays that reach eye Light refraction - Refraction is a result of o Cornea § Contributes most to refraction § Refractive ability remains constant because curvature never changes o Lens § Refractive ability can be adjusted by changing curvature as needed for near or far vision Accommodation - For far vision o Light rays are parallel- need less bending o Lens should be flatter - For near vision o More bending needed o Rounder lens - Involves  o Ciliary muscles o Suspensory ligaments - For far vision o Ciliary muscle relax o Suspensory ligament are pulled taut o Lens is flatter/ weaker - For near vision o Ciliary muscles contract o Suspensory ligaments go slack o Tension in lens causes it to become rounder/ stronger Lenses - Convex lens o Convergent o Bends light rays in o Ie. Lens of eye - Concave lens o Divergent o Bends light rays out Eye Conditions - Emmetropia o Normal vision - Myopia o Near-sightedness o Lens is too strong or eye too long o Focus is in front of retina o Corrected with a concave lens - Hypermetropia or hyperopia o Far-sighted-ness o Lens too weak or eye to short o Focus is behind retina o Corrected with a convex lens - Presbyopia o Loss of vision with age o Due to stiGening of lens § Harder to become round o Correct with reading glasses  Light Transduction - Occurs on the retina - Photoreceptors o Rods and cones - Bipolars - Ganglions - Optic nerve - Horizontal cells- lateral inhibition - Amacrine cells- assist? Retinal Layers - Light must filter through cell layers before hitting the rods and cones - Blind spot- where optic nerve leaves eye Retina - Fovea o Pinhead-sized depression in centre of retina o Most distinct vision o Has only cones (no filtering) - Macula Iutea o Area immediately surrounding fovea o High acuity § Cones only- but with overlaid bipolars and ganglions Macular Degeneration - Loss of cones in macula - Lose central vision - Leading cause of blindness in western hemisphere - “doughnut” vision - Wet- more blood vessels- bleeding - Dry- atrophy of pigment Photo receptors - Rods and cones - Consists of three parts o Outer segment § Directs light stimulus o Inner segment  § Contains metabolic machinery of cell o Synaptic terminal o Transmits signal generated in photoreceptor on light stimulation to next cells in visual pathway Rods Cones 100 million per retina 3 million per retina Vision in shades of grey Colour vision- 3 main types High sensitivity Low sensitivity Low acuity High acuity Night vision Day vision Much convergence in retinal Little convergence in retinal pathway pathways More numerous in periphery Concentrated in fovea Rods - 100:1 wiring (rods to bipolars) o Low light needed to stimulate 1 bipolar - Larger receptor field o Poor acuity Cones - 1:1 wiring o Need a lot of light for action potential - Smaller receptor field o High acuity Photopigments - Rod pigment o Provide vision only in shades of grey o Rhodopsin- absorbs all/ most visible wavelengths - Cone pigment o Colour vision § Red cones § Green cones § Blue cones - Chemical change when activated by light - Consists of 2 components  o Opsin § Protein that is integral part of disc membrane o Retinene § Derivative of vitamin A § Light-absorbing part of photopigment Resting State- in Dark - Na+ gates are open o Rods and cones are depolarized o Release inhibitory neurotransmitter- glutamate o Bipolar cells are inhibited o No action potentials to ganglions/ optic nerve In Light - Light breaks down photopigment o Activates transduction/ decrease in cGMP o Closes Na+ gates o Hyperpolarize membrane o Decreases inhibition of bipolars § Bipolars excited § GP’s to ganglions § Action potentials to optic nerve Colour Blindness - Poor or lack of function in one or more colour cones o Protanopia- lack of red cones o Deuteranopia- lack of green cones o Tritanopia- lack of blue cones - Poor function of cones o Protanomaly- poor red function o Deuteranomaly- poor green function o Tritanomaly- poor blue function Dark Adaptation - Go from light to dark o Re-form more photopigment § Changes threshold o Eyes become more sensitive  o More rods used o Vitamin A needed for regeneration o Ie. Entering movie theatre Light Adaptation - When you go from dark to bright light o Sudden break-down of photo-pigment (bleaching) - Eyes become less sensitive with less photopigment - Ie. Walking outside after a movie Hearing - Pitch (tone) of sound o Depends on frequency of air waves - Intensity (loudness) o Depends on amplitude of air waves - Timbre (quality) o Determined by overtones Ear Structure - Outer ear o Pinna § Visible ear o External auditory meatus § Ear canal o Tympanic membrane § Ear drum § Entry to middle ear - Middle ear o Amplifies sound by 20-30x o Ear ossicles § Malleus § Incus § Stapes o Eustachian tube § Equalizes ear pressure o To oval window - Inner ear o Cochlea  § Contains organ of corti, endolymph, perilymph § Transduction from waves (ripples) to action potentials Organ of Corti - Receptors- hair cells - Basilar membrane- contains hair cells - Tectorial membrane- stiG, tips of hair cells, imbedded here Transmission of Sound - Sound waves hit tympanic membrane o Membrane oscillates o Moves ear ossicles- amplified waves o Oval window moves in and out- sets perilymph in motion - Standing waves form in perilymph, transfer into endolymph - Basilar membrane will then oscillate - Pushes hair cells against tectorial membrane - Bends hair cells- GP’s - Action potentials down auditory nerve - Location of bent cells determines pitch Deafness - Conduction deafness o Problem with amplification of sound § Ear ossicles, tympanic membrane § Hearing aids will help § Ie. Ear infection, or otosclerosis - Sensory deafness o Problem with hair cells or auditory nerve § Hearing aids cannot help § Ie. Loud music damage Equilibrium - Vestibular apparatus o Inner ear o Balance and body position o Consists of § Semicircular canal § Utricle and saccule  - Mechanical deformation of hair cells o Created by body movement - Vestibular nerve o To cerebellum o Balance and posture o Motion and orientation o Eye movement - Deceleration o Hair cells stop- endolymph continues o Bends hair cells in other direction Semi-Circular Canals - Detects acceleration and deceleration o Uses endolymph and hair cells o In all planes - As body accelerates o Hair cells move o Endolymph lags behind o Bends hair cells o Ion gates altered o Action potentials Utricle and Saccule - Detects linear motion - Endolymph contains otoliths o Calcium “stones” - As head moves o Heavier endolymph moves forward o Bands hair cells- action potentials Taste and Smell - Chemoreceptors o Binding of molecules will trigger graded potential and action potentials - Smell o Olfactory nerve - Taste o Facial nerves o Glossopharyngeal nerves Smell - Scent moles must be dissolved in mucous- support cells - 140+ scent receptors identified so far- 2 month lifespan (then replaced) - Closely associated with taste - Input to limbic system- emotional response, related to memories Taste - Receptors are taste buds o Lifespan of 10 days o 5 types § Salty § Sweet § Sour § Bitter § Umami o Support cells § Mucous Do you have a Taste Bud map - Facial nerve o Front 2/3 of tongue o Salty and sweet - Glossopharyngeal nerve o Back 1/3 of tongue o Sour bitter - Umami o Central concentration- some in periphery - Some people show regions of sensitivity while others do not