Exam 6 Learning Outcomes PDF

What you need to know for the "new" part (85%) of Exam 6. Cumulative questions will make up about 15%. **Ch. 15: Autonomic Nervous System** ==================================== Section 15.1 General Properties of the Autonomic Nervous System ---------------------------------------------------------...

What you need to know for the "new" part (85%) of Exam 6. Cumulative questions will make up about 15%. **Ch. 15: Autonomic Nervous System** ==================================== Section 15.1 General Properties of the Autonomic Nervous System --------------------------------------------------------------- 1. Explain how the autonomic and somatic nervous systems differ in form and function. (see table 15.1 and fig. 15.2) a. Somatic- division on PNS that controls body & skeletal muscle b. Autonomic- involuntary, controls glands, cardiac & smooth muscles, don't depend on autonomic to function i. Sympathetic- **fight or flight** ii. Parasympathetic- **rest & digest** c. Enteric- brain of the gut 2. Describe visceral reflex arcs, including structural and functional details of sensory and motor (autonomic) components. (see fig. 15.1) d. Sensory receptor- nerve endings that detect stretch, tissue damage, blood chem, body temp & other stim e. Sensory neuron f. Integration center g. Motor neuron h. Effector 3. Explain how the two divisions of the autonomic nervous system differ in general function. i. **Sympathetic** iii. Increase HR iv. Pupil dilation v. Short pre & long post neurons vi. Bronchiole dilation vii. Increased lipid breakdown viii. **Thoracolumbar** division- neurons emanate from those areas of SC ix. Output affects renin release, glucose levels & thermoregulation j. **Parasympathetic** x. Long pre & short post neurons xi. Increased urination xii. Increased digestion xiii. **Craniosacral** division- neurons emanate from those areas of SC k. Define autonomic tone. xiv. Balance b/w sympathetic & paras activity together xv. Generally, S excites & P inhibits l. Identify the anatomical components and nerve pathways of the sympathetic and parasympathetic divisions. m. Contrast the anatomy of the parasympathetic and sympathetic systems, including central nervous system outflow locations, ganglia locations, pre-/post-ganglionic neuron relative lengths, and ganglionic and effector neurotransmitters. (see fig. 15.2, 15.8) n. **Sympathetic** xvi. Cell bodies in lateral horns of thoracic & lumbar areas of SC xvii. How do pre connect with post? 1. Synapse at sympathetic trunk ganglion 2. Synapse at prevertebral ganglia 3. Synapse at the adrenal medulla xviii. ACh- post-ganglionic neurons xix. NE- preganglionic neurons, somatic motor neurons o. **Parasympathetic** xx. Cell bodies in cranial nerves of BS & lateral horns of sacral area of SC xxi. NE- pre & post-ganglionic neurons p. Discuss the relationship of the adrenal glands to the sympathetic nervous system. xxii. Adrenal cortex- outer layer 4. Secretes steroid hormones adrenal medulla (inner layer) xxiii. Essentially a sympathetic ganglion xxiv. Modified post neurons w/o dendrites or axons- stim by preganglionic S neurons that terminate on these cells xxv. Secrete a mix of hormones into the bloodstream Section 15.2 Anatomy of the Autonomic Nervous System ---------------------------------------------------- 4. Identify the anatomical components and nerve pathways of the sympathetic and parasympathetic divisions q. Sympathetic xxvi. **Thoracolumbar division** 5. Cell bodies of its preganglionic neurons are in the lateral horns & gray matter of thoracic lumbar areas of SC 6. Short pre & long post 7. Each paravertebral ganglion is connected to a spinal nerve by 2 branched called communicating rami 8. Their axons exit the cord by way of spinal nerves T1 & T2 xxvii. Synapse with post-ganglionic neurons most at sympathetic chain (paravertebral) ganglia, or at adrenal medulla xxviii. Longitudinal series of ganglia that lie adjacent to both sides of vertebral column from the cervical to coccygeal level xxix. Interconnected by longitudinal nerve cords xxx. **Splanchnic nerve** 9. Nerves that pass through the chain without synapsing, continue as this r. Parasympathetic xxxi. **Craniosacral division** 10. Cell bodies in cranial nerves of the brain & lateral horns of the sacral area of SC 11. Signaling pathways being in the brain & sacral region of SC, travel in certain cranial & sacral nerves xxxii. Synapse with post-ganglionic neurons most commonly at terminal ganglia near organ 12. Long pre & short post xxxiii. Cranial nerves that carry parasympathetic fibers: 13. **Oculomotor-** control lens & pupil by terminating at ciliary muscle & pupillary constrictor 14. **Facial-** regulate tear, salivary, nasal glands 15. **Glossopharyngeal-** salivation 16. **Vagus nerve** (CN X): carries 90% of all parasympathetic preganglionic fibers 5. Discuss the relationship of the adrenal glands to the sympathetic nervous system (see fig. 15.6 and section 15.2b) s. Essentially a sympathetic ganglion t. Sympathetic pre-ganglion fibers penetrating through cortex & terminate on these cells u. Closely related in development & function- sympathoadrenal system 6. Describe the enteric nervous system of the digestive tract and explain its significance. v. Complex neural circuitry that does not arise from BS or SC w. Brain of the gut Section 15.3 Autonomic Effects on Target Organs ----------------------------------------------- 7. Name the neurotransmitters employed at different synapses of the ANS. (see fig. 15.8) x. Sympathetic preganglionic fibers: ACh y. Sympathetic postganglionic fibers: NE z. Parasympathetic preganglionic fibers: ACh a. Parasympathetic postganglionic fibers: ACh A diagram of a nervous system Description automatically generated 8. Name the receptors for these neurotransmitters and explain how they relate to autonomic effects. b. Types of cholinergic receptors xxxiv. **Muscarinic** 17. Excitatory in paras target organs & smooth muscle 18. Inhibitory in cardiac muscle 19. Muscarine mimics actions of ACh 20. G-protein coupled xxxv. **Nicotinic** 21. Usually excitatory 22. Found at NMJ, all post-gang neurons & adrenal medulla 23. Nicotine mimics actions of ACh 24. Ionotropic c. Differentiate between locations of cholinergic and adrenergic nerve fibers (see Table 15.4) xxxvi. Cholinergic- 25. Pre- sympathetic & para 26. Post para xxxvii. Adrenergic- 27. Mostly post-sympathetic d. Know the locations and effects of all adrenergic receptors. xxxviii. **Table below** xxxix. **Alpha 1- can be found in multiple organs & BV and cause constriction of BV** e. Know which enzymes break down of xl. ACh- AChE xli. E- COMT and MAO (monoamine oxidase) 9. Explain how the ANS controls many target organs through dual innervation. f. Heart- S speeds up & P slows down xlii. Dual innervation- nerve fibers stim same call g. BV (of viscera) xliii. No dual innervation- only S fibers to constrict h. Bronchioles xliv. No dual innervation- only S fibers to dilate i. Pupil diameter- S dilates & P constricts xlv. Antagonistic effects- each division innervates different effector cells xlvi. S in the iris and P in constrictor cells j. Sweat glands xlvii. No dual innervation- only S fibers 10. Define dual innervation (section 15.3b, see fig. 15.9) k. Receive nerve fibers from S and P l. S & P effects are often antagonistic but can also be cooperative in some tissues- salivation m. Most body organs will have innervation from both divisions n. **NOT**- xlviii. S & P effects always occur simultaneously or all tissues have equal innervation 11. Explain how control is exerted in the absence of dual innervation (section 15.3c, see fig. 15.10) o. An increase in firing constricts vessel, while a decrease in firing dilates vessel +-----------------------+-----------------------+-----------------------+ | **Adrenergic** | **Major Locations** | **Effect** | | | | | | **Receptor** | | | +=======================+=======================+=======================+ | **β1** | Heart, kidneys, | Increase heart rate | | | adipose tissue | and force of | | | | contraction, | | | | stimulates kidneys to | | | | secrete renin | +-----------------------+-----------------------+-----------------------+ | **Β2** | Lungs, blood vessels | Mostly inhibitory, | | | serving heart, liver, | dilates blood vessels | | | skeletal muscle | and bronchioles, | | | | relaxes smooth muscle | +-----------------------+-----------------------+-----------------------+ | **β3** | Adipose tissue | Stimulates lipolysis | +-----------------------+-----------------------+-----------------------+ | **α1** | Blood vessels of | Constricts blood | | | skin, mucosae, | vessels and visceral | | | abdominal viscera, | organ sphincters, | | | kidneys, salivary | dilates pupils | | | glands, sympathetic | | | | organs except heart | | +-----------------------+-----------------------+-----------------------+ | **α2** | Membrane of | Inhibits NE release | | | adrenergic axon | from adrenergic axon | | | terminals, pancreas, | terminals, inhibits | | | blood platelets | insulin secretion by | | | | pancreas, promotes | | | | blood clotting | +-----------------------+-----------------------+-----------------------+ Section 15.4 Central Control of Autonomic Function -------------------------------------------------- a. Identify what parts of the brain influence the autonomic nervous system. a. Cerebral cortex i. Limbic system is involved in emotional responses & connects to hypothalamus ii. Site of nuclei of autonomic control b. Hypothalamus iii. Major control center of visceral motor system iv. Hunger, thirst, thermoreg, emotions & sexuality c. Midbrain, pons & medulla oblongata v. Centers for cardiac & vasomotor control, salivation, swallowing, sweating GI secretion, bladder control, pupillary con/di vi. Autonomic output from these nuclei travel through SC & oculomotor, facial, glossopharyngeal & vagus nerves d. SC vii. Elimination or urine & feces **Ch. 16: Special Senses** ========================== Section 16.1 Properties and Types of Sensory Receptors ------------------------------------------------------ 1. Define *receptor* and *sense organ.* a. Detects stim b. Structure that combines nervous tissue with other tissues that enhance its response to a certain type of stim 2. Define transduction. c. The conversion of one form of energy to another 3. List the four kinds of information obtained from sensory receptors and describe how the nervous system encodes each type. d. **Modality**- type of stum or sensation produced e. **Location** -- detects stimuli within receptive field i. Receptive field- area of skin neuron covers ii. Two-point discrimination- 2 touches on back vs face f. **Intensity** g. **Duration** iii. Adaptation- prolonged stim= firing gets slower over time= less aware iv. Phasic receptors vs tonic receptors 1. Phasic- burst of AP when first stimulated then quickly adapt & sharply reduce or stop signaling, even if stim continues 2. Tonic- adapt more slowly & generate signals more steadily h. Phenomenon of adaptation ?? 4. Outline three ways of classifying receptors: i. **Type of stim**: thermoreceptors, photoreceptors, nociceptors, chemoreceptors, mechanoreceptors j. **Body location**: exteroceptors, interceptors, proprioceptors k. **Structural complexity**: general vs. special senses Section 16.2 The General Senses ------------------------------- 5. List the types of somatosensory receptors (see Table 16.1). (general) l. **Unencapsulated endings** v. Free nerve endings- warm, cold, pain vi. Tactile discs- light touch & pressure vii. Hair receptors- light touch & movement of hairs m. **Encapsulated endings** viii. Fiber terminals are enclosed in CT capsule ix. Tactile (Meissner's) corpuscles- discriminative touch, phasic, dermal papilla x. Lamellar (Pacinian)- on/off deep pressure, vibration, deep dermis/subQ xi. Bulbous (Ruffini)- continuous deep pressure, dermis/subQ/joint capsules xii. Muscle spindles- muscles stretch, reflex initiation, perimysium of muscle xiii. Tendon organs- proprioceptors stretched by muscle contraction, detect muscle tension, reflex initiation, tendons xiv. Joint kinesthetic receptors- proprioceptors, monitor stretch in articular capsules of synovial joints, info on joint position & motion 3. Lamellar & bulbous corpuscles, free nerve endings, tendon organs n. Special xv. Limited to the head & are innervated by cranial nerves and employ relatively complex organs o. Describe each of the following types of receptors, indicating what sensation it detects and giving an example of where it can be found in the body: xvi. Nociceptors- pain xvii. Temperature xviii. Mechanoreceptors (proprioceptors and baroreceptors/pressoreceptors) 4. Mostly encapsulated xix. Chemoreceptors xx. Photoreceptors 6. Refresh your memory on somatosensory projection pathways (see section 16.2c, also originally part of the information on spinal tracts from Ch 13) p. Sensory projection is the transmission of info from a receptor or a receptive field, to a specific locality in the cerebral cortex enabling the brain to detect & identify the stim q. Pathway flowed by sensory signals to their ultimate destinations in the CNS are called projection pathways r. From receptor to final destination in the brain, most somatosensory signals travel by way of first, second & third neurons s. First order fibers synapse with second that decussate & lead to thalamus 7. Describe the types and mechanisms of pain. t. Define pain xxi. Warns of actual/impending tissue damage, strong motivation to take action xxii. Visceral 5. Noxious stim of receptors in thoracic/abdominal cavity 6. Vague & dull ache 7. Travels along the same routes as somatic pain xxiii. Deep somatic 8. From bones, joints, muscles at related sources xxiv. Neuropathic 9. From nerves, SC, meninges or brain xxv. Referred 10. Pain from one part is perceived as coming from another part u. Know the **projection pathways for pain** (fig 16.3) 11. Piking finger- info comes into posterior to 2^nd^ order neuron 12. Info crosses over into the [spinothalamic], up to the thalamus with 3^rd^ order neurons, up to the primary somatosensory cortex in the finger v. Analgesic xxvi. Pain relieving mechanisms in CNS related to long-known analgesic effects of opium, morphine & heroin xxvii. Fibers stop pain signals at dorsal horn w. Endorphins- larger analgesic, pain suppression by the brain x. Opioids- y. Know how spinal gating works (fig. 16.5). xxviii. 1^st^ order neurons fiber conducts a pain signal to posterior horn of SC, 2^nd^ conducts it to thalamus & 3^rd^ to cerebral cortex 13. Signals from the spinothalamic tract pass through the thalamus 14. Signals from the spinoreticular bypass thalamus to sensory cortex xxix. It stops pain signals at the posterior horn 15. Nociceptor releases sub P onto spinal interneuron 16. 2^nd^ order fiber conducts signal up spinothalamic tract to thalamus 17. 3^rd^ order fiber relays signal to somesthetic cortex 18. Into from hypothalamus & cerebral cortex converge on central gray sub of the midbrain 19. [Midbrain] relays signal to reticular formation of medulla oblongata 20. Some descending analgesic fibers from medulla secrete serotonin into inhibitory spinal interneurons 21. Spinal interneurons secrete [enkephalins], blocking pain transmission by postsynaptic inhibition of 2^nd^ order pain neuron 22. Other descending analgesic fibers synapse of 1^st^ order pain fibers, blocking pain transmission by presynaptic inhibition xxx. Note- the first steps from the first-order neuron from the nociceptor through the third-order neuron that lands in the cerebral cortex is the same pathway as the spinothalamic tract Section 16.4 Hearing and Equilibrium ------------------------------------ 8. Identify the properties of sound waves that account for pitch and loudness. z. Pitch xxxi. Sense of whether a sound if high or low xxxii. Determined by the frequency at which the sound source, eardrum & other parts of the ear vibrate a. Loudness xxxiii. Perception of sound energy, intensity or amplitude of vibration xxxiv. Expressed in decibels with 0 to dB defined by a sound energy that corresponds to threshold of human hearing 9. Describe the gross and microscopic anatomy of the ear (see fig. 16.11 and 16.13) b. Outer, middle & inner ear c. Outer & middle are concerned with transmitting sound to inner d. Inner is where vibration is converted to nerve signals e. Identify the hearing structures of the outer, middle and inner ear. xxxv. **Outer ear:** 23. Essentially, it is a funnel for conducting airborne vibration to the eardrum 24. Auricle- funnels sound waves 25. Auditory canal (meatus)- extends from auricle to eardrum xxxvi. **Middle ear:** 26. Tympanic membrane- eardrum a. Boundary b/w external & middle ears composed of CT b. Transfers sound energy to auditory ossicles 27. Ossicles (malleus, incus, stapes) c. Transmit vibrations of eardrum to oval window 28. Oval window- males internal ear fluids 29. Round window- cochlea & covered by membrane xxxvii. **Inner ear:** 30. **Cochlea** d. Organ of hearing- coiled tube that arises from anterior side of vestibule e. Divided into 3 chambers i. **Scala vestibuli**- continuous with vestibule ii. **Scala tympani**- terminates at round window iii. Scala media 31. Cochlear duct f. Middle fluid chamber in cochlea 32. **Bony labyrinth** g. Vestibule- contain equilibrium receptors h. Semicircular canals- contain equilibrium receptors 33. **Membranous labyrinth** i. Utricle & saccule iv. Responsible for static equilibrium & sense of linear acceleration j. Semicircular ducts v. Membranous part that detects rotary movements k. Ampulla(e) vi. Dilated sac in the utricle vii. Houses a mound of hair cells & supporting cells xxxviii. Receptors: 34. Spiral organ- hearing receptors 35. Macula & crista- path of hair & support cells 36. Ampullaris f. Roles of the accessory structures xxxix. Describe the functions of the **ceruminous glands** 37. Secretions mix with dead skin cells to form earwax 38. Very sticky & coats guard hairs, making them more effective in blocking foreign particles from auditory canal xl. Describe the role of the auditory tube in drainage and equalization of pressure in the middle ear. 39. Serves to aerate & brain 40. It is normally flattened & closed but swallowing or yawning opens it & allows air to enter or leave the tympanic cavity 41. This equalizes air pressure on both sides of tympanic membrane, allowing it to vibrate freely 42. Excessive pressure on one side of the other muffles the sense of hearing & can cause pain 10. Explain how the ear converts vibrations to nerve signals and discriminates between sounds of different intensity and pitch. g. **Describe how the various structures of the outer, middle and inner ear function in hearing.** xli. External ear- auricle & external acoustic meatus, ceruminous glands 43. Made of elastic cartilage & used to catch sound xlii. Tympanic membrane- partition b/w external & middle ear xliii. Middle ear- ossicles 44. Air filled cavity- acts as a lever that amplifies the force of vibration xliv. Internal ear- bony labyrinth & membranous labyrinth xlv. **Steps** 45. Sound waves vibrate the tympanic membrane 46. Auditory ossicles vibrate- pressure is amplified 47. Pressure waves created by stapes pushing on the oval window move through fluid in scala vestibuli 48. Sound with frequencies below hearing travel through helicotrema & do not excite hair cells 49. Basilar membrane moves up & down, and stereocilia of the hair cells embedded in the tectorial membrane bend 50. Then nerve impulses begin in the cochlear nerve & travel to the brain 51. When they reach the auditory cortex in the temporal lobe, they are interpreted as sound xlvi. Describe how the spiral organ converts sound waves into action potentials (see fig. 16.17) 52. When unstimulated, the K gate is closed 53. When hair cells are stimulated, K membrane opens causing delop/excitatory h. Describe the sound conduction pathway from the auricle (pinna) to the fluids of the inner ear and the path of nerve impulses from the spiral organ to various parts of the brain. (See fig. 16.16 for some of the first part and fig 16.19 for the last part from the cochlear nerve ---\> auditory cortex) xlvii. Hear a sound wave- auricle picks up on this sound wave & it travels through external auditory canal xlviii. This vibrates the tympanic membrane which shakes the auditory ossicles & puts pressure on fluid (perilymph) in oval window xlix. Sound then goes to cochlear ducts which vibrate hair cells in basilar membrane l. Bending of hair cells lead to receptor potential leading to a nerve impulse i. Explain how the structures of the ear enable differentiation of pitch and loudness of sounds. (See fig. 16.18) li. **High** frequency 54. Causes the basilar membrane to vibrate near the base of cochlea lii. **Low** frequency 55. Causes the basilar membrane to vibrate near apex of the cochlea 11. Explain how the **vestibular apparatus** enables the brain to interpret the body\'s position and movements. j. Contains fluid & semicircular canals, utricle & saccule k. When we move so does the fluid, agitating its hair cells that will then release NT (glutamate) to CN Vll & pons that will interpret body position/movement l. Distinguish between static and dynamic equilibrium. (See section 16.4d) liii. Static- perception of the orientation of the head space liv. Dynamic- perception of motion or acceleration m. Describe the structure of the maculae and their function in static equilibrium. (See fig. 16.20) Include: otoliths, otolithic membrane, hair cell, supporting cell, vestibular nerve. lv. Saccule & utricle contain patches of air & supporting cells (macula). Each hair cells is embedded in a gelatinous otolithic membrane- weighted with protein Ca called otoliths. This adds to the inertia of the membrane & enhances sense of gravity & motion lvi. Understand that gravity acts on the otolithic membrane when you move your head or accelerate, and the movement of the otolithic membrane causes the hair cells to bend, which causes depolarization of hair cells. 56. With the head erect, the otolithic membrane bears directly down on hair cells- stimulation is minimal 57. When you tilt your head down, heavy otolithic membrane sags & bends- stimulating hair cells 58. Any orientation of the head causes a combination of stimulation to utricle (horizontal) & saccule (vertical) 59. The brain interprets head orientation by comparing these inputs to each other and input from eyes & neck to detect if only the head is tilted or the entire body is lvii. Head position is determined in your brain by how the otolithic membrane sags/bends hair cells in your right and left macula sacculi and right and left macula utriculi. As your head changes positions, the rate of action potentials changes in each receptor. 60. The inertia of the otolithic membranes is important in detecting linear acceleration 61. When the fair cells bend toward kinocilium the hair cell depolarizes, exciting the nerve fiber, which generates more frequent AP 62. When hair cells bend away from kinocilium, the hair cells hyperpolarize, inhibiting the nerve fiber & decreasing the AP n. Describe the structure of the crista ampullaris and its function in dynamic equilibrium. lviii. Include: semicircular ducts, cupula, endolymph, hair cells, vestibular nerve fibers. 63. Head movement leads to semicircular ducts & hair to move with it & hair bundles bend causing receptor potential & nerve impulse which is vestibular branch of the vestibulocochlear nerve 64. Semicircular ducts are filled with endolymph- each one opens into the utricle & has a dilated sac called ampulla; within is a group of hair cells called the crista ampullar- they are embedded in membrane (culpula) 65. When the head turns the duct rotates but endlymph lags; it pushes on the cupula & bends stimulating the hair cells o. Describe how the vestibular apparatus enables the brain to interpret the body's position and movements (vestibular projection pathways, see fig. 16.22) 66. **Cerebellum**- integrates vestibular info into its control of head & eye movements, muscle tone & posture 67. **Reticular formation**- is though to adjust breathing & blood circulation to changes in posture 68. **Spine**- where fibers descend the 2 vestibulospinal tracts on each side & synapse on motor neurons that innervate the extensor muscles 69. **Thalamus**- relays signals to 2 areas of cerebral cortex l. One is inferior is sensory regions of face & it is here that we become conscious of body position & movements m. Other end is thought to be involved in motor control of the head & body 70. Nuceli of CN 3,4,6 these produce eye movement that compensate for movements of head 12. Disorders to know (look up if not in the text) a. Otitis media (see deeper insight 16.1 pg. 580) i. Middle ear inflammation ii. Common result of sore throat iii. Frequent case of hearing loss in children iv. Eardrum bulges & becomes inflamed v. Usually treated with antibiotics vi. Accumulation of large amounts of fluids b. Conduction deafness vii. Something hampers sound conduction to the fluids of internal ear viii. Ex- compacted earwax or ruptured eardrum c. Sensorineural deafness ix. Damage to any neural structures b/w cochlear hair cells & auditory cortical cells Section 16.5 Vision ------------------- 13. Describe the anatomy of the eye and its accessory structures. p. Know the 6 extrinsic eye muscles, what actions they perform, and which cranial nerve innervates them. (see fig 16.25) Extrinsic Eye Muscle Action Cranial Nerve ---------------------- -------------------------------------- ------------------ Lateral Rectus Moves eye Laterally Abducens (VI) Medial Rectus Moves eye Medially Oculomotor (III) Superior Rectus Elevates eye and turns it medially Oculomotor (III) Inferior Rectus Depresses eye and turns it medially Oculomotor (III) Inferior Oblique Elevates eye and turns it laterally Oculomotor (III) Superior Oblique Depresses eye and turns it laterally Trochlear (IV) q. Know the function of the fovea centralis and macula lutea lix. **Fovea centralis**- tiny pit in the center 71. Contains only cones 72. Images are focused when placed directly on your fovea lx. **Macula lutea** 73. Oval "yellow spot" in exact posterior 74. Lateral to optic disc r. Why is the optic disc called the blind spot? (Pg. 596) lxi. Weak spot- no photoreceptors or sclera 14. Discuss the structure of the retina and its receptor cells. s. Inner layer t. Originates from the brain u. Millions of photoreceptors transduce light energy v. 2 layers lxii. Outer pigment- absorbs light lxiii. Inner neural- vision 75. Ora serrata 76. Optic disc 77. Macula lutea 78. Fovea centralis w. Rod cells- night vision x. Cone cells- day vision 15. Explain how the optical system of the eye creates an image on the retina. y. Admit light rays, bend them & focus images on the retina z. Trace the path of light as it passes through the eye to the retina and the path of nerve impulses from the retina to various parts of the brain. lxiv. **Pathway** 79. Cornea 80. Aqueous humor (brains) 81. Lens 82. Vitreous humor 83. Neural layer of retina 84. Photoreceptors lxv. **Path of light**- Light at an angle is refracted by the cornea, but no lens or aqueous humor all light is refracted to fixed point on back of retina. Then light passes through lens to form inverted image on retina lxvi. **Path of nerve**- when bipolar cells detect fluctuations in light intensity, they stimulate ganglion cells directly or indirectly 85. Ganglion cells are the [only] retinal cells that produce AP and respond to bipolar cells with rising & falling firing frequencies 86. Via optic nerve, these changes provide visual signals to the brain lxvii. Light bends 3 times 87. Entering cornea 88. Entering lens 89. Leaving lens lxviii. The lens is elastic & its light-bending power can change for better focusing lxix. Understand that the light refracts (bends) light when it comes into the eye at the cornea and the lens 90. The cornea & lens refract light rays so they converge on a focal point- image is inverted upside down & reversed from left to right a. Define emmetropia lxx. State in which the eye is relaxed & focused on an object more than 6m away, the light rays coming from the object are essentially parallel & rays are focused on the retina w/o effort b. Describe the near response (see fig. 16.33) lxxi. **Accommodation**- changes lens shape lxxii. **Constriction of pupils**- enhances accommodation, prevents most divergent light rays from entering eye lxxiii. **Convergence of eyes**- medial rotation of the eye c. Describe hyperopia and myopia and what type of lenses correct for these. (fig. 16.35) lxxiv. **Hyperopia** 91. Farsightedness 92. Distant objects seen clearly 93. Image is focused behind the retina 94. Use convex lens lxxv. **Myopia** 95. Nearsightedness 96. Close objects seen clearly 97. Image is focused in front of retina 98. Use concave lens 16. Discuss how the retina converts this image to nerve signals (phototransduction) d. Describe how light activates photoreceptors. (see fig 16.39) lxxvi. Visual pigments: rhodopsin 99. **Opsin**- protein part n. Cones have 3 types- blue, green & red o. Rods have 1- rhodopsin 100. **Retinal**- light-absorbing part p. Made from vit A q. Absorption of light by a visual pigment leads to structural changes lxxvii. Rhodopsin bleaching lxxviii. Steps 101. In light rhodopsin absorbs photons of light- cons are working 102. Retinal isomerizes to trans-retinal (changes shape to straight tail) 103. Opsin triggers reaction cascade that breaks down cGMP 104. Trans-retinal separates from opsin (becomes bleached) 105. Into the dark, the trans retinal is converted back to cis retinal 106. Opsin & cis-retinal enzymatically combine to regenerate rhodopsin lxxix. **Light activated** rhodomisn activates (g-protein) which deactivates cGMP; this hyperpolarization lxxx. In **the dark** the cGMP binds cation channels to keep them open, Na & Ca enter & depolarize cell e. Explain the mechanism of generating visual signals (fig. 16.40) lxxxi. Darkness: 107. Rods are depolarized because sodium ion channel is open. The rod releases glutamate onto bipolar cells. 108. Bipolar cells are hyperpolarized (glutamate inhibits them) 109. Ganglion cells receive no stimulus from bipolar cells, and therefore do not send any action potentials along the optic nerve. r. cGMP gated channels open, allowing cation influx s. photoreceptors depolarize t. voltage gated Ca channels open u. NT is released v. NT causes ISPS- hyperpolarization occurs w. Hyperpolarization closed voltage gated Ca channels, inhibiting NT release x. No ESPS occur in ganglion cells y. No AP occurs lxxxii. Light: 110. Rods are hyperpolarized because sodium ion channel closes. 111. Bipolar cells are depolarized because there is a [lack] of glutamate/inhibition from the rods. Bipolar cells release neurotransmitter that binds to receptors on ganglion cells. 112. Ganglion cells are depolarized (from bipolar cell neurotransmitter binding to receptors on ganglion cell), and ganglion cells send action potentials along optic nerve. z. cGMP channels close, photoreceptors hyperpolarize a. voltage gated Ca channels close in synaptic terminal b. no NT is released c. lack of IPSP cell results in depolarization d. depolarization opens voltage gated Ca channels, NT gets released e. EPSP occurs lxxxiii. Rods and bipolar cells can depolarize/hyperpolarize but cannot send action potentials. Only ganglion cells can send action potentials. f. Compare and contrast the function of rods and cones in vision. lxxxiv. **Rods** 113. Dim light, peripheral vision, black/white & most common 114. Ex- star gazing lxxxv. **Cones** 115. Bright light, high resolution color & not as common 17. Explain the process of light and dark adaptation. (Pg. 602-603) g. Light adaptations- dark to light is fast h. Dark adaptations- light to dark is slow i. Cones regenerate rapidly whereas rhodopsin regenerates more slowly j. Reflexive changes in pupils occur during adaptation 18. Describe the mechanism of color vision (generally) k. Three type of cones are named for absorption peaks of their photopsins- lxxxvi. **Short-wavelength** (S) peak sensitivity at 420 nm lxxxvii. **Medium-wavelength** (M) peak at 531 nm lxxxviii. **Long-wavelength** (L) peak at 558 nm l. Color perception based on mixture of nerve signals representing cones of different absorption peaks 19. Trace the visual projection pathways in the brain. (see fig. 16.45) m. Axons of retinal ganglion cells= optic nerve= optic chiasma= optic tract= thalamus= optic radiation (axons from thalamic neurons to cerebral white matter)= primary visual cortex (occipital lobe) 20. Eye diseases and disorders to know: a. Myopia (see table 16.2) a. Nearsightedness- eyeball is too long b. Light rays come into focus before they reach the retina c. Corrected with concave lenses b. Hyperopia (see table 16.2) d. Farsightedness- eyeball is too short e. Retinal lies in front of the focal point of the lend & light rays have not yet come into focus when they reach the retina f. Fixed with convex lenses c. Diplopia (see section 16.5d) g. Eyes cannot converge h. Ex- when the extrinsic eye muscles are weaker in one eye than the other i. Double vision d. Cataracts (see deeper insight 16.3) j. This occurs as the lens fibers darken with age, fluid-filled clefts appear b/w them & they accumulate debris from degenerating fibers k. Clouding of lenses causing vision to appeak milky or looking from behind a waterfall l. It can arise as a complication of diabetes & can be worsened by smoking, radiation, drugs & viruses e. Macular degeneration (see deeper insight 16.3) m. Death of receptor cells in the macula or central part of the retina & location of sharpest vision n. Can develop so slowly that one fairs to notice change in vision f. Strabismus -- double vision due to the inability to fixate on the same point with both eyes o. Double vision due to the inability to fixate on the same point with both eyes Cumulative material to consider reviewing: ========================================== - The somatic nervous system (the neurons that participate in the neuromuscular junction) - Somatic reflex arcs - Cranial nerves that participate in the autonomic nervous system, vision, and hearing/equilibrium - Cerebral white matter tracts in the brain, especially projection tracts - Spinal sensory tracts involved in pain - G protein-coupled/second messenger receptor systems 1. NT receptor in membrane 2. NE (hormone) bind to receptor 3. Receptor activates G-protein 4. G-protein activates adenylate cyclase (enzyme) 5. This uses ATP to make thousands cAMP (second messanger) 6. This can a. Change membrane permeability (open ligand-gated channels) to let ions in b. Activate enzymes = metabolic change c. Start genetic transcription = enzyme synthesis = metabolic change - E and NE are synthesized from tyrosine AA