Unit 5 - ANS, Special Senses Flashcards
1
Q
What is the difference between sensation and perception? What are the types of sensory modalities?
A
sensation: conscious/subconscious awareness of changes in environment
perception: conscious interpretation of sensations mainly performed by cerebral cortex
each type of sensation is called a sensory modality
general senses: somatic (tactile, thermal, proprioception), visceral (pressure, chemicals, stretch, nausea, hunger, temp)
special - smell, tase, vision, hearing, equilibrium
2
Q
What sensation do free nerve ending detect?
A
pain, temperature, tickle, itch and some touch
3
Q
What sensations do encapsulated nerve ending sense?
A
pressure, vibration, and some touch
enclosed in a capsule of CT
4
Q
Describe exteroreceptors, interoreceptors, and proprioceptors. How are they grouped?
A
some receptors are grouped based on location/origin of the stimuli that activate them
exteroreceptors - at or near external surface of body
- hearing, vision, smell, taste, touch, pressure, vibration, pain
interoreceptors - monitors the body’s internal environment (blood vessels, visceral organs, etc.)
proprioreceptors - provide info about body position, muscle length/tension, and position/movement of joints
5
Q
What are the 3 types of sensory receptors that are based on microscopic structure?
A
- free nerve endings (bare dendrites) - pain, thermal, tickle, itch and some touch
- encapsulated nerve endings (dendrites with CT) - pressure, vibration, and some touch
- separate cells - receptors synapse with first-order sensory neurons
- located in retina, inner ear, and taste buds
6
Q
What are the 6 types of receptors that are classified by the type of stimulus detected?
A
- mechanoreceptors - detect mechanical stimuli (touch, pressure, vibration, hearing, stretching of blood vessels, etc)
- thermoreceptors - detect changes in temp
- nociceptors - respond to painful stimuli from physical or chemical damage to tissue
- photoreceptors - detect light that strike the retina
- chemoreceptors - detects chemicals in mouth, nose and bodily fluids
- osmoreceptors - detect chemicals in moth, nose and body fluids
7
Q
What are the somatic sensations and what are the tactile sensations?
A
somatic - tactile, thermal, pain and proprioceptive
tactile - touch, pressure, vibration, itch and tickle
8
Q
What are the two types of pain? What is superficial somatic pain?
A
fast - acute, sharp, or prickling
- perceived within 1 second
- A fibers, note felt in deeper tissue
slow - chronic, burning, aching, throbbing
- perceived a second of more after the stimulus
- C fibers, increases intensity over time
superficial somatic pain - pain that arises from skin receptors
9
Q
Describe deep somatic and visceral pain. What is referred pain?
A
deep somatic - affects skeletal muscles, joints, tendons and fascia
visceral - stimulation of pain receptors in visceral organ
- presents in or deep to the skin that overlies the simulated organ
referred pain - a type of diffuse visceral pain
- felt in a surface area far from the stimulated organ
10
Q
Describe muscle spindles, tendon organs and joint kinesthetic receptors and their role with proprioception
A
muscle spindles - type of proprioceptor, found in skeletal muscle
- monitors muscle length, involved in stretch reflexes
tendon organs - type of proprioceptor, found at junction of muscle/tendon
- protects muscles/tendons from damage due to overstretching
joint kinesthetic receptors - type or proprioceptor, exits in and around the joint capsule of synovial joints
- respond to pressure, acceleration and deceleration during movement, help prevent strain
11
Q
Describe the following tactile receptors: Meissner and pacinian corpuscles, hair root plexus
A
Meissner - capsule surrounding mass of dendrites in dermal papillae of hairless skin
- onset of touch and low-frequency vibration
Pacinian - oval, layered capsule surrounds dendrites in dermis and subQ, submucosal tissue, joints, periosteum and viscera
- high frequency vibration
hair root plexus - free nerve endings wrapped around hair follicles in skin
- movements on skin that move hair
12
Q
Describe the following tactile receptors: tactile discs, Ruffini corpuscles, itch and tickle receptors
A
tactile discs - saucer shaped free nerve ending that make contact with tactile epithelial cells in epidermis
- touch and pressure
Ruffini - elongated capsule surrounds dendrites deep in dermis and in ligaments and tendons
- skin stretching and pressure
itch and tickle - free nerve ending and mucous membranes
- itching and tickling
13
Q
Describe the somatic sensory pathway. What are the three neurons that this pathway consists of?
A
somatic sensory pathway - carries info from somatic sensory receptors to primary somatosensory area and cerebellum
three neurons:
- first order neurons: impulses from somatic receptors to the brainstem/spinal cord
- second order neurons: impulses from brainstem/spinal cord to thalamus
- third order neurons: impulses from thalamus to primary somatosensory area of the cortex on the same side
14
Q
What do both the posterior and anterior spinocerebellar tract do? What is it important for?
A
both posterior and anterior spinocerebellar tract carry proprioceptive impulses to cerebellum
both pathways important for posture, balance, and coordination of skilled movement
15
Q
What are lower motor neurons?
A
nerves that extend out of the brain stem/spinal cord
LMNs innervate skeletal muscles of the face and head through cranial nerves, skeletal muscles of the body through spinal nerves
- only LMNS provide output from the CNS to skeletal muscle fibers
16
Q
What are the 4 functions of the cerebellum?
A
- monitoring intentions of movement
- monitoring actual movement - input from proprioceptors
- comparing command signals with sensory information
- sensing out corrective feedback
- feedback to UMNs: continuously provides error corrections to UMNs, decreases errors and smoothes motion
17
Q
What are the 4 integrative functions of the cerebellum?
A
- wakefulness and sleep
- relies on reticular activating system (RAS)
- REM/non-REM sleep - coma - state of unconsciousness in which an individual has little or no response to stimuli
- learning and memory
- immediate - ability to recall ongoing experiences for few seconds
- short term - ability to recall memories for few minutes
- long term - language
- Wernike’s association area
- Broca’s motor area
18
Q
Describe Parkinson’s
A
60+
too little dopamine
tremor and hypokinesia - muscle has decreased range in motion
19
Q
What are some major differences between somatic and autonomic motor systems?
A
somatic - effect is always excitation
autonomic - can be exciting or inhibiting
hard to control ANS
Somatic NT’s - ACh
Autonomic - ACh, NE, (chromaffin - EPI and NE)
20
Q
What are the divisions of the ANS and what is dual innervation?
A
sympathetic - fight of flight
- increased alertness and metabolic activities that help prepare for emergency
parasympathetic - rest and digest
- conserve and restore body energy during times of rest
- output mostly to GI and respiratory tracts
dual innervation - receive impulses from both sympathetic and parasympathetic neurons
21
Q
What are the two motor neurons that are found in each division of the ANS?
A
preganglionic neuron: cell body is located in the brain/spinal cord and exits the CNS via nerve
SYMPATHETIC - thoracolumbar division - cell bodies in lateral gray horns in T1-L3
PARASYMPATHETIC - craniosacral division - located in nuclei of CN of the brainstem - III, VII, IX, X, in the lateral gray matter of S2-S4
postganglionic neuron: entirely in PNS - cell body and dendrites located in autonomic ganglion
- autonomic ganglion: where they synapse
22
Q
Describe the sympathetic trunk ganglia
A
lie in vertical row on wither side of the vertebral column, extending from the base of the skull to the coccyx
- innervates organs above the diaphragm (head, neck, shoulders, heart)
- neck has specific sympathetic trunk ganglia: superior, middle and inferior cervical ganglia
since they are near the spinal cord, sympathetic PREGANGLIONIC axons are short, most sympathetic postganlgionic axons ae long
23
Q
Describe the pre vertebral (collateral) ganglia of the sympathetic nervous system
A
lies anterior to the vertebral column and close to the large abdominal arteries
-innervates organs below the diaphragm
5 major pre vertebral ganglia: celiac ganglion, superior mesenteric, inferior mesenteric, aorticorenal ganglion, renal ganglion
24
Q
Describe the parasympathetic ganglia
A
Preganglionic axons of parasympathetic division synapse with postganglionic neurons in terminal (intramural) ganglia
- located close to or actually within the wall of visceral organ
terminal ganglia in the head have specific names: ciliary ganglion, pterygopalatine, submandibular, otic ganglion
because terminal ganglia are located close to or in the wall of the visceral organ - parasympathetic preganglionic axons are long
25
Once axons of the sympathetic preganglionic neurons pass to the sympathetic trunk ganglion, what are the 4 ways that they connect with postganglionic neurons?
1. axon synapses with the first postganglionic neuron it reaches
2. axon may ascend or descend to higher/lower ganglion
3. axon may continue without synapsing, go through the sympathetic trunk ganglion and end at the pre vertebral ganglion
4. axon may extend to chromaffin cells on the adrenal medullae
26
What is divergence? How does the sympathetic nervous system display it?
projection of one single sympathetic preganglionic fiber has many axon collaterals that can synapse with 20+ postganglionic neurons
- helps explain why many sympathetic responses affect almost the entire body simultaneously
27
Does the parasympathetic response have a whole body response like the sympathetic response?
No - responses typically are localized to single effectors
parasympathetic presynatpic neurons usually only synapse with 4-5 postsynaptic neurons that all supply a single visceral effector
28
What are autonomic plexuses? Where re they?
autonomic plexuses - network of axons of both sympathetic and parasympathetic in the thorax, abdomen, and pelvis
- lie along major arteries
29
What are the autonomic plexuses in the thorax?
cardiac plexus - supplies the heart
| pulmonary plexus - supplies the bronchial tree
30
What are the autonomic plexuses in the abdomen and pelvis?
Celiac (solar) plexus - the largest autonomic plexus and surrounds the celiac trunk
- two large celiac ganglia
- two aorticorenal ganglia
superior mesenteric plexus - contains the superior mesenteric ganglion - small and large intestines
inferior mesenteric plexus - contains the inferior mesenteric ganglion
- extends through the hypogastric plexus - anterior to the L5: supplies the pelvic viscera
renal plexus - contains the renal ganglion - supplies the renal arteries within the kidneys and uterus
31
Describe the organization of sympathetic trunk ganglia
pair - anterior and lateral to the vertebral column, one on each side
3 cervical, 12 thoracic, 5 lumbar, 5 sacral sympathetic trunk ganglia
- 1 coccygeal ganglion
- right and left coccygeal ganglion are fused together and usually lie on the midline
extends from neck to coccyx, but only receive preganglionic axons from the thoracic and lumbar segments of spinal cord
32
What is Horner's syndrome?
sympathetic innervation to one of the side of the face is lost due to inherited mutation, injury or disease
- affects sympathetic outflow through the superior cervical ganglion
symptoms: ptosis (eyelid droop), miosis (constriction of pupil), anhidrosis (no sweat)
33
What is a cholinergic autonomic neuron? What neurons in the ANS are cholinergic?
neuron that releases ACh, includes:
1. all sympathetic and parasympathetic pre ganglionic neurons
2. sympathetic postganglionic neurons that innervate most sweat glands
3. All parasympathetic post ganglionic neurons
34
What are the cholinergic receptors? What are the two types?
cholinergic receptor - binds ACh
nicotinic receptor- when ACh binds, excitation - found in:
- plasma membrane of dendrites/cell bodies of sympathetic and parasympathetic postganglionic neurons
- chromaffin cells
- neuromuscular junction
muscarinic receptors - can be excitation or inhibition - found in:
- plasma membrane of all effectors
- most sweat glands
nicotine does not activate muscarinic receptors, muscarine does not activate nicotinic receptors
ACh quickly inactivated by acetylcholinesterase - effects are short
35
Describe adrenergic neurons
release norepinephrine
most SYMPATHETIC POSTGANGLIONIC neurons are adrenergic
NE can either cause excitation or inhibition of effector cell
36
Describe the relationship between adrenergic receptors and NE and EPI
can bind NE and epi
NE can be released either as:
- NT by sympathetic post ganglionic neurons
- hormone by chromaffin cells of adrenal medullae
EPI released as hormone
NE - stimulates alpha receptors more strongly than beta
EPI - strong stimulator of both alpha and beta receptors
NE - taken up by axon or enzymatically inactivated - remains in synaptic cleft longer than ACh
37
Describe adrenergic neurons. What is alpha and beta?
Alpha receptors and Beta receptors - found on visceral effectors innervated by sympathetic post ganglionic axons
- subtypes based on specific responses they select by selective binding of drugs that activate/block them
- A1/B1 - typically produces excitation
- A2/B2 - typically cause inhibition
- B3 - present only on cells of brown adipose tissue for thermogenesis
cells of most effectors contain either alpha or beta receptors, come visceral effectors have both
38
What are receptor agonist and antagonist and give an example
Agonist - binds and activates receptor - mimicking the effect of natural NT or hormone
- phenylephrine - adrenergic agonist - reduces mucus production and relieves nasal congestion
antagonist - binds and blocks receptor, prevents natural NT or hormone to exert effects
- atropine - blocks muscarininc ACh receptors - dilated pupils, reduces gland secretion and relaxes smooth muscle of GI tract
39
What is autonomic tone
balance between sympathetic and parasympathetic activity
| - regulated by the hypothalamus
40
What are the structures that only receive sympathetic innervation?
```
sweat glands
erector pili muscles
kidneys
spleen
most blood vessels
adrenal medullae
```
41
What effects are longer, sympathetic or parasympathetic stimulation? Why?
sympathetic stimulation are longer and more widespread due to:
1. sympathetic post ganglionic axons diverse more extensively - many tissues activated simultaneously
2. ACh-ase quickly inactivated ACh, but NE remains in synaptic cleft for al longer period
3. EPI and NE secreted into the blood from the adrenal medullae
- blood borne hormones circulate through the body and effect all tissues with A/B receptors
- NE/EPI destroyed by enzymes in the liver
42
What are the parasympathetic responses that are the "three decreases"? What is SLUDD?
1. decrease heart rate
2. brochoconstriction
3. constriction of the pupils
SLUDD - salivation, lacrimation, urination, digestion and defecation
43
What are autonomic reflexes? What are they good for? Describe a pathway. What is the hypothalamus important for?
autonomic reflexes - responses that occur when nerve impulses pass through an autonomic reflex arc
- plays key roll in regulating controlled conditions in the body
- adjusts activity in visceral effector without conscious perception
1. receptor
2. sensory neuron - impulse from receptors to CNS
3. integrating center - HYPOTHALAMUS AND BRAINSTEM
- some integrate in the spinal cord (pee poop)
4. preganglionic and post ganglionic neuron
5. effectors - smooth muscle, cardiac muscle and glands
hypothalamus - major control and integration center of the ANS
- connected to both the sympathetic and parasympathetic divisions
44
What are the accessory structures of the eye? What are the functions of the palpebra? Function of the lacrimal caruncle?
eyelids, eyelashes, eyebrows, lacrimal apparatus, extrinsic eye muscles
palpebra functions - shade for eyes during sleep, protect eyes from excessive light/foreign objects, spread lubricating secretions over the eyeball
lacrimal caruncle - contains sebaceous and sudoriferous (sweat) glands
45
What is the tarsal plate and its glands? What another name for its glands? What happens when the tarsal glands get infected?
tarsal plate - thick layer of CT that gives support and form to the palpebra
tarsal glands - Meibomian glands
- secrete fluid that helps keep the palpebra from adhering to one another
Chalazion - when tarsal glands get infected and produce a cyst
46
What is the conjunctiva and what is it function? Where is it found? What happens when it gets infected?
conjunctiva - protective mucous membrane, composed of nonkeratinized stratified squamous epithelium, numerous goblet cells and supported by areolar CT
- palpebral: lines inner space of eyelids
- bulbar: lines surface of eyeball - sclera but no cornea
dilation/congestion of blood vessels of the bulbar conjunctiva causes bloodshot eyes
47
What are the purpose of eyelashes and eyebrows? What structures are important for them, and what happens when that structure gets infected?
protect the eye from foreign objects, perspiration and direct sun rays
contain sebaceous ciliary glands that release lubricating fluid to the follicles
- infection of these glands cause sty - painful, pus filled swelling
48
What is the lacrimal apparatus? What is lacrimal fluid? What is its function?
group of structures that produces/drains lacrimal fluid or tears
lacrimal gland - secretes lacrimal fluid that drains from 6-12 excretory lacrimal ducts
- tears emptied onto surface of conjunctiva of upper lid
lacrimal gland supplied by parasympathetic fibers of facial (VII) nerves
lacrimal fluid - contains salts, some mucus and lysozyme - protective bactericidal enzyme that cleans, lubricates the eye
- each gland produces about 1mL of lacrimal fluid per day
49
What CN are the eye muscles supplied by?
Occulomotor (III), trochlear (IV), or abducens (VI)
50
What is the fibrous tunic? What are the functions of both sections? What is it composed of?
superficial layer of eyeball, consists of:
1. anterior cornea: transparent coat that covers iris
- curved - helps focus light onto the retina
- outer surface: NKSSET, middle - collagen and fibroblast, inner: simple squamous ET
2. posterior sclera: white of eye - made mostly of dense CT, collagen and fibroblast
- covers entire eyeball besides cornea
- gives shape to eyeball
- protects inner parts
- serves as site of attachment for extrinsic eye muscles
51
What is the scleral venous sinus? What is another name for it? What is its function, and where is it?
AKA canal of Schlemm - located at junction of cornea and sclera
- drains aqueous humor - liquid that gives nutrients to inner part of eye
52
What is the choroid and what tunic is it part of?
vascular tunic - dark due to high concentration of melanin
functions:
- highly vascularized for nutrients for posterior surface of retina
- many melanocytes to absorb stray light - allow image cast on retina from cornea and lens to look sharp and clear
53
Describe the ciliary body. What is it composed of? What tunic is it part of?
ciliary body - anterior portion of the vascular tunic
- extends form the ora serrata to junction of sclera and cornea
appears dark brown due to melanin
consists of two parts:
1. ciliary processes: contain blood capillaries and secrete aqueous humor
- zonular fibers (suspensory ligaments) - extend from the ciliary processes and attach to the lens - contacts and relax to control the lens
2. Ciliary muscles - circular band of smooth muscle that contacts and extends to change the tightness of zonular fibers
- alters the SHAPE OF THE LENS when adapting to near or far vision
54
What is the iris and what determines its color? What is its function? Why is the pupil black?
iris - colored portion of the eyeball
consists of melanocytes, circular and radial smooth muscle fibers
- amount of melanin determines eye color
function - regulates the amount of light entering the eyeball through the pupil
pupil black bc we see heavily pigmented back of eye (choroid, retina)
- bright light causes red eye due to blood vessels or retina
55
What happens when bright light stimulates the eye? What happens to eye in dim light?
autonomic reflex - pupil diameter regulated
bright light - parasympathetic fibers of the oculomotor (III) nerve stimulate the CIRCULAR MUSCLES or SPHINCTER PUPILLAE of the iris to contract to decrease size of pupil
dim light - sympathetic neurons stimulate the RADIAL or DILATOR PUPILLAE of the iris to contract, causing increase in pupils size - dilation
56
What are the layers of the retina? What tunic is it part of? What is an ophthalmoscope?
retina is its own tunic
pigmented later - sheet of melanin containing epithelial cells to help absorb stray light rays
neural (sensory) layer - sends nerve impulses into axons that form the optic nerve
ophthalmoscope - provides magnified image of retina and blood vessels, Optic nerve
57
What are the three distinct layers of retinal neurons? What are the layers between them? What are the order that light hits them?
1. ganglion cell layer
2. inner synaptic layer
3. bipolar cell layer - also contains horizontal and amacrine cells - modify the signals being transmitted along the neural pathway
4. outer synaptic layer
5. photoreceptor layer - specialized cells that begin the process by which light rays are ultimately converted to nerve impulses
58
What are the two types of photoreceptors? What happens once photoreceptors are stimulated?
Rods - allow us to see in dim light
Cones - produce color
three types of cones: blue, red and green - sensitive to light of that color
from photoreceptors, info flows through the outer synaptic layer to the bipolar cells
- bipolar cells through inner synaptic layer to ganglion
- axons go ganglion cells extent posteriorly to optic disc - exits eyeball via optic nerve (II)
59
Describe the following structures of the retina: macula lutea, fovea centralis, optic disc.
macula lutea - exact center of posterior part of eye
fovea centralis - small depression n center of macula lutea
- contains ONLY cones - area of highest visual acuity/resolution
- rods absent in fovea centralis, more plentiful in periphery of retina
optic disc - blind spot: no rods or cones
- where axons exit to optic nerve (II)
60
What is the lens? What is it structure? What protein does it contain? What is its function?
lens - contains protein called crystallins that are arranged like an onion
- refractive media of the lens - typically transparent and lacks blood vessels
- enclosed by clear CT capsule, held in position by zonular fibers that attach it to ciliary processes
lens function - helps focus images on the retina to facilitate clear vision
splits the eye into anterior CAVITY and vitreous chamber
61
What does the anterior cavity consist of? What is it filled with?
anterior cavity - space anterior to the lens, consists of two chambers:
- anterior chamber - between cornea and iris
- posterior chamber - behind iris and lies in front of lens
both chambers of anterior cavity filled with aqueous humor - clear watery fluid that nourished the lens and cornea
62
Describe the flow of tears
Lacrimal gland secretes tears to
Excretory lacrimal ducts, that distribute tears over surface of eye
Superior and anterior puncta are holes that drain to the superior and inferior lacrimal canaliculi, that drains liquid to
Lacrimal sac, which drains into
Nasolacrimal duct, which drains to
nasal cavity
63
Describe aqueous humor. What is its pathway?
clear, watery fluid that nourished the lens and cornea
Ciliary process - filters out of blood capillaries and enters posterior chamber of anterior cavity
drains into the Canal of Schlemm and into the blood
aqueous humor is typically replaced every 90 minutes
64
Describe the vitreous chamber. What is the hyaloid canal?
Posterior to the lens
contains vitreous body - transparent jellylike substance that holds the retina flush against the choroid
- keeps shape of eye interocular pressure
vitreous body - formed during embryo, consists of water, collagen fibers, hyaluronic acid
- also contains phagocytic cells that remove debris
hyaloid canal - narrow channel that runs through vitreous body to lens
- fetus - hyaloid artery
65
What is intraocular pressure?
pressure in the eye - maintains shape of eyeball and prevents eye from collapsing
produced mainly by aqueous humor and partly vitreous body - normally about 16mmHg
66
Describe refraction of light and its role in image formation
Cornea - both surface refracts light about 75%
Lens - both surfaces refracts light about 25% - allow light to come into exact focus on the retina
images focused on the retina are INVERTED (upside down) and
RIGHT-TO-LEFT REVERSAL - light from R side of object strikes L side of retina, vice versa
When an object is 6m (20 ft) from the viewer, light rays reflects from object are nearly parallel to one another
- lens must bent parallel rays so that they fall exactly on central fovea - sharp vision
67
Describe accommodation for near and far vision. What happens to the lens?
near - when light rays are closer than 20 ft , they are divergent instead of parallel
lens changes shape - becomes more curved (convex) - increased focusing power and causes greater convergence of light rays
- ciliary muscle contracts - pulls ciliary process and choroid toward lens,
- less tension on lens and zonular fibers
distant - ciliary muscle of ciliary body is relaxed
lens is flatter - stretched in all directions by taught zonular fibers
68
What is the near point of vision?
near point of vision: minimum distance from the eye that an object can be clearly focused with maximum accommodation
distance about 10 cm (4 in) in young adult - aging causes it to increase
69
describe the following refraction abnormalities: presbyopia, myopia, hypermetropia and astigmatism. What is an emmetropic eye?
presbyopia - lens losing elasticity - less ability to curve to focus on close object due to aging
- 40: near point 20 cm (8 in)
- 60: can be as much as 80 cm
- react more slowly to light and dark
myopia - near sighted - eyeball longer than it should be
- image converges in front of the retina
- close images sharp, distant blurry
hypermetropia - far sighted - eyeball shorter than it should be
- image converges behind the retina
- far objects clear, near blurry
emmetropic - normal eye, reflects light correctly
astigmatism - condition where the cornea or lens has an irregular curve
- blurred/distorted vision
- can be corrected by glasses, contacts, or LASIK
70
Describe constriction of the pupil and its role in forming images.
constriction of pupil - narrowing of the diameter of the hole through which light enters the eye due to contraction of the circular muscle of the iris
- prevents light rays from entering the eye through the periphery of the lens
71
Describe convergence of the eyes. What is binocular vision?
binocular vision - both eyes focus on one set of objects
- occurs when light rays from an object strike corresponding points on the two retinas
convergence - medial movement of eyeballs so that both are directed toward object being viewed
- nearer the object, greater the degree of convergence to maintain binocular vision
- coordinated action of extrinsic eye movement causes convergence
72
What are photopigments? What photopigments do each of the photoreceptors have?
photopigment - colored protein that undergoes structural change when absorbing light
- light absorption initiates events that lead to receptor potential
rods - contain only rhodopsin
- pigmented layer of retina adjacent to photoreceptors stores large quantity of vitamin A, contributes to regeneration of rods
- in darkness, rods release inhibitory glutamate: inhibits bipolar cells from transmitting signals to ganglion cells
cones - three different photopigments for each of the types of cones - red, blue, green
- regenerate much more quickly than rhodopsin in rods
73
What happens at the outer segment and inner segment of the rods and cones?
outer segment - closer to pigment epithelial cell
- transection of light energy into a receptor potential occurs in outer segment
inner segment - contains cell nucleus, Golgi complex, mitochondria
- proximal end of inner segment - expands into bulblike synaptic terminals filled with synaptic vesicles
74
What are the two parts of the photopigments that are associated with vision? How do they react to light?
opsin - glycoprotein
- 4 types of opsins - 3 cones and one rods (rhodopsin)
retinal - vitamin A derivative - formed from carotene
1. in darkness - retinal has BENT shape - cis-retinal - fits in opsin portion of photopigment
- isomerization: when cis-retinal absorbs light, straightens into trans-retinal - first step of visual transduction
- chemical intermediated form and disappear - lead to production of receptor potential
2. trans-retinal separates from opsin - product colorless = bleaching of photopigment
3. enzyme called retinal isomerase converts trans retinal back to cis retinal
4. cis-retinal binds to opsin - reforms functional pigment
- regeneration - resynthesis of a photopigment
75
Describe light adaptations and ark adaptation. What is faster?
light - occurs when someone moves from dark to light
- occurs in seconds
dark - light to dark area
- takes minutes
length due to rates of bleaching and regeneration of photopigments in rods and cones
- light causes rod receptors to degrease their release of inhibitory glutamate
76
Visual signals undergo processing in the retina. What cells does this occur in? What happens after?
visual signals undergo considerable amount of processing at synapses among various types of neurons in retina - horizontal, bipolar and amacrine cells
axons of retinal ganglion cells provide output from retina to brain - exits via optic (II) nerve
some visual features get enhanced while others are discarded
input can converge of diverge into postsynaptic neurons - convergence predominates
77
What happens once receptor potentials arise in the outer segment of the rods and cones? How many rods and cones synapse with bipolar cells?
once receptor potentials arise in the outer segments of rods and cones, they spread to inner segments to synaptic terminals
at synaptic terminals, NTs are released by rods and cones to induce graded potentials in bipolar and horizontal cells
6-600 rods synapse with 1 bipolar cell
- excitement only
1 cone synapses to 1 bipolar cells
- can excite or inhibit
- cone vision - less sensitive but sharper bc of 1-1 synapse
78
What is the purpose of horizontal cells and amacrine cells when processing visual input in the retina?
horizontal - transmit inhibitory signals to bipolar cells to assist in differentiation of various colors
amacrine cells - when excited by bipolar depolarizes ganglion cells and initiates nerve impulses
79
What is the visual field? Describe what happens when the fibers of the optic tract terminate at the superior colliculi and pretectal nuclei.
visual field - everything that can be seen by one eye
superior colliculi - some fibers in optic tract terminate at superior colliculi to control extrinsic eye movement
pretectal nuclei - some fibers in optic tract terminate at pretectal nuclei to control pupillary and accommodation reflexes
80
What is binocular visual field?
binocular visual field - large region where the visual fields of the two eyes over lap
- anterior location of eyes leads to visual field overlap
81
Describe how the two visual fields of each eye are split up. What part of the brain does it go to?
visual fields of each eye are nasal (medial) and temporal (lateral)
visual information from the RIGHT half of each visual field travels to the left side of the brain
visual information from the LEFT half of each visual field travels to the right side of the brain
82
Describe the steps of the visual pathway
1. exits eye via optic nerve (II), forms optic chiasm
2. axons from temporal half continue to thalamus on same side
- nasal half: cross at optic chiasm to thalamus on opposite side
3. axons of thalamic neurons form OPTIC RADIATIONs - project to primary visual cortex
83
What are the three separate systems for visual signals to be processed in the cerebral cortex?
1. processes info related to shape
2. processes information related to color
3. processes info related to movement, location and spatial organization
84
What does the external ear consist of and what are the function of these structures?
auricle (pinna) - captures sound
external auditory canal - transmits sound to eardrum
- ceremonious glands - secretes cerumen to protect canal/eardrum from water/insects
- contains a few hairs - with cerumen, prevents dust/foreign object from entering
tympanic membrane - partition between external auditory canal and middle ear
- tear: perforated eardrum from pressure, trauma, middle ear infection - heals in month
85
Describe the middle ear. What separates it from the external and internal ear?
separated from external ear by tympanic membrane
separated from internal ear by thin bony partition that has two membrane openings:
- oval window, round window
bones: malleus, incus, stapes
- base of stapes fits into oval window
round window - enclosed by membrane called the secondary tympanic membrane
86
What are the muscles of the middle ear and what cranial nerves control them? What is the auditory tube?
tensor tympani - supplied by mandibular branch of trigeminal (V) nerve
- limits movement and increases tension on eardrum
- prevents damage to the inner ear from loud noises
stapedius muscle - supplied by facial (VII) nerve
- dampens large vibrations of the stapes due to loud noises
- protects inner ear from prolonged loud noises
auditory tube - AKA Eustachian tube
- connects middle ear with nasopharynx
- normally closed at pharyngeal end
- when you swallow or yawn, it opens - allows air to enter/leave middle ear until P in inner ear and atmosphere equalize
87
Describe the outer bony labyrinth of the internal ear. What structures does it contain and what is it filled with?
encloses the inner membranous labyrinth
three areas: semicircular canals, vestibule, cochlea
lined with periosteum and contains perilymph
perilymph - chemically similar to cerebrospinal fluid
- surrounds membranous labyrinth
- houses receptors for hearing and equilibrium
88
Describe the epithelial inner membranous labyrinth. What liquid does it contain? What Is the vestibule and what are the structures within it? What are the semicircular canals, and what is the ampulla?
surrounded by outer bony labyrinth
membranous labyrinth contains endolymph
- high [K] in endolymph - plays role in generation of auditory signals
vestibule - membranous labyrinth in vestibule consists of two sacs: utricle, saccule
- projecting superiorly and posteriorly to vestibule are semicircular ducts - connect via utricle
anterior, posterior and lateral semicircular canals lie approximately at right angles of each other
- semicircular ducts - portions of membranous labyrinth inside semicircular canal
ampulla - swollen enlargement at the end of each semicircular canal
89
Describe the nerves in the inner ear that derive from the vestibular branch of there vestibulocochlear nerve
Vestibular branch of vestibulocochlear (VIII) consists of: ampullary, utricular, and saccular nerves
- contain both first order secondary and motor neurons that synapse with receptors fore equilibrium
cell bodies of the sensory neurons are located in the vestibular ganglia
90
What are the three divisions of the cochlea? What is the modiolus?
cochlear duct - continuation of membranous labyrinth into the cochlea
- filled with endolymph
scala tympani - ends at the round window
scala vestibuli
both scala tympani and vestibuli are part of BONY labyrinth - filled with perilymph
- helicotrema - opening at the apex of cochlea that is only opening to cochlear duct
bone core of the cochlea
- makes 3 turns around a central bony core
91
Describe the vestibular membrane and the basilar membrane. What is on the basilar membrane?
vestibular membrane - separates cochlear duct from scala vestibuli
basilar membrane - separates cochlear duct from scala tympani
Organ of corti - spiral organ - sits on basilar membrane
- coiled sheet of epithelial cells: supporting cells and hair cells - receptors for hearing
92
Describe inner and outer hair cells. What do they synapse with? Where are the cell bodies of the sensory neurons located?
inner hair cells - organized in single row
outer hair cells - organized in three rows
at the apical tip of each hair cell are 40-80 stereo cilia
at their basal ends, hair cells synaptic with:
- first order sensory neurons
- motor neurons from the cochlear branch of the vestibublochochlear (VIII) nerve
cell bodies of sensory neurons are located in spiral ganglion
93
Describe the tectorial membrane
flexible gelatinous membrane that covers hair cells in spiral organ
- ends of stereocilia of hair cells are embedded into the tectorial membrane
94
What is the audible range? What make sound louder? Describe the hearing threshold
audible range - 20 to 20K Hz
larger the intensity (amplitude) or vibration, the louder the sound
hearing threshold - point at which an average young adult can distinguish sound from silence
95
Describe the physiology of hearing in steps.
1. Auricle directs sound waves into external auditory canal
2. Sound waves strike tympanic membrane - causes it to vibrate
- vibration depends on pitch - low = slow, high = fast
3. Central area of the tympanic membrane connects to the malleus - vibrates along with tympanic membrane
- transmitted from the malleus to incus to stapes
4. As stapes vibrates, it vibrates oval window
5. Movement of stapes/oval window sets up fluid pressure waves in perilymph of cochlea
- as oval window bulges inward, pushes on perilymph of the scala vestibuli
6. pressure waves transmitted from the Scala vestibuli to scala tympani - eventually to round window
- round window bulges toward inner ear
7. pressure waves travel through perilymph of scala vestibule to vestibular membrane, then moves into endolymph in cochlear duct
8. pressure waves in endolymph causes basilar membrane to vibrate, which moves hair cells of spiral organ against tectorial membrane
- this bends the steriocilia - generation of nerve impulses in first order neurons in the cochlea nerve
9 sound waves of various frequencies cause certain regions of the basilar membrane to vibrate more intensely than others
96
What causes nerve impulses in hearing? How does different frequencies effect regions of basilar membrane? How does intensity affect the basilar membrane?
When the pressure waves of the endolymph cause the basilar membrane to vibrate, it moves the hair cells on the spiral organ against the tectorial membrane
steriocilia bend and generate nerve impulses in first-order neurons in cochlear nerve fibers
each segment of the basilar membrane is tuned for a particular pitch
- base of cochlea (closer to oval window): smaller/stiffer, high frequency pitches induce maximal vibration
- apex of cochlea - bigger/more flexible - low sounds cause maximal vibration
high intensity sound waves cause larger vibrations of basalar membrane - higher frequency of nerve impulses
97
How can we locate the source of a sound?
slight differences in timing of nerve impulses arriving from the two ears at the end of superior oliviary nuclei
98
How do the auditory nerve impulses reach the primary auditory area?
bending of stereocilia generates nerve impulses to the cochlear nerve
reaches spiral ganglia, gets conducted along axons in the cochlear branch of vestibulocochlear (VIII) nerve
synapse in cochlea nuclei in medulla:
- then goes to pons, lateral meniscus, inferior colliculi, thalamus then to primary auditory cortex
Some axons decussate in the medulla - R and L primary auditory areas received impulses from both ears
99
What are the two types of equilibrium?
static - refers to the maintenance of the position of body (mainly head) relative to the force of gravity
- body movements that stimulate the receptors for static equilibrium: tilting head, linear decel/acceleration
dynamic equilibrium - maintenance of body position (mainly head) in response to sudden movement
- rotational acceleration/deceleration
100
What is the vestibular apparatus and what does it consist of?
receptor organs for equilibrium
static organs: saccule, utricle
dynamic equilibrium - semicircular ducts
101
What is the macule? What kind of cells does it consist of?
thickened portion of the utricle and saccule that contain the receptors for equilibrium
composed of hair and supporting cells
102
What frequency is best heard at the base of the cochlea? The apex?
base of cochlea - narrower and stiffer - high frequency
apex of cochlea - wider and more flexible - low frequency
103
What is a tip link protein? What are stereocilia and kinocilia? What happens when it gets bent in each direction?
tip link - protein connects tips of stereocilia
stereocilia - hair like projections of hair cell
kinocilia - tallest stereocilia
when bent toward kinocilia - opens mg ion channels, lets in K
- depolarization: allows Ca to open
- Ca releases glutamate
- generates nerve impulses
bending away from kinocilia - hyperpolarization, reduces NT release
104
What are otoacoustic emissions? What causes them?
cochlea produces noise - caused by vibrations of outer hair cells in response to sound waves/motor neuron signals
in deaf babies - reduced/not produced
105
What is a hair bundle? What is the otolithic membrane? What is an otolith and what is it made of?
hair bundle - stereocilia and kinocilia
otolithic membrane - thick gelatinous glycoprotein layer that rests on hair cells, sits on top of the macula
otoliths - layer of dense calcium carbonate crystals that extends over surface of otolithic membrane
106
How do motor neurons affect hair cells?
motor neurons synapse with hair cells and sensory neurons - they can regulate the sensitivity of hair cells and sensory neurons
107
What is the crista? What is the cupula? What is the ampulla?
crista - group of hair cell + support cells
cupula - gelatinous material that covers the crista
ampulla - dilated portion of the semicircular ducts, contains crista
- contains endolymph - lags behind hair cells
108
Where do nerve impulses for the vestibular branch of the vestibularcochlear nerve go?
vestibular ganglia becomes the vestibular branch of the vestibulocochlear (VIII) nerve to the vestibular nuclei in pons and medulla
- also has input from vision and proprioception
vestibular nuclei projects to:
- thalamus to vestibular area - conscious awareness of position and movement of head and limbs
- occulomotor nerve (III) - eye
- trochlear nerve (IV) - eye
- abducens (V) - eye
- accessory (XI) - head and neck
- cerebellum
- vestibulospinal tract - muscle tone
109
What is presbycusis? Tinnitus?
presbycusis - hearing loss, happens around age of 60
tinnitus - ringing of the ears
vestibular imbalance also occurs in elderly
110
What are the similarities between olfaction and gustation?
chemical senses - requires molecules to be dissolved to be sensed by receptors
both propagate in the limbic system - can evoke strong emotional response
111
Where are olfactory receptors found? What are their structures like?
olfactory epithelium, area is about 5 cm2 in the superior part of nasal cavity
bipolar neuron - axon projects through cribiform plate to olfactory bulb
- olfactory hairs - respond to odorants
bind odorants to trigger generator potential - triggers one or more nerve impulses
112
What are support and basal cells in the olfactory receptors? What are Bowman's glands? What do bowman's and support glands have in common?
support - columnar cells forming mucous membrane that lines nose
- provide support, nourishment, insulation and detoxification
basal - stem cells
Bowman's glands - produce mucous to moisten olfactory epithelium and dissolve odorants
support/bowman's innervated by facial (VII) bc they secrete
- stimulate lacrimal glands and mucous glands in nose
113
Describe adaptation in scent
about 50% in first second, very slowly afterward
| - reduced sensitivity involved adaptation process in CNS
114
What is the pathway for smell? Where else does it project? What is the orbitofrontal area?
olfactory receptor to olfactory nerve
- olfactory bulb to olfactory tract
- goes directly to primary olfactory area in the cortex - NO THALAMUS
some axons project to the limbic system and the hypothalamus
orbitofrontal area - important for odor identification
115
What are the 5 chemical taste and what cause them? What are their different thresholds?
sour - H+ ions
salt - Na ions
bitter, sweet, umami - bind to receptors that are linked to G proteins
- activate second messengers that cause release of NT
bitter - lowest
sour - higher
salty and sweet higher than both
different tastes arise from activation of different groups of neurons
- each gustatory receptor cell responds to more than one of the primary tastes, just stronger than others
116
Where are receptors for taste found?
tongue, soft palate, pharynx and epiglottis
117
What are the cells that make taste buds?
Basal - stem cells
supporting cells
Gustatory cell - life span of about 10 days
- synapse with dendrites of neurons that form the gustatory pathway
- each first order neuron is highly branched and makes contact with several taste buds
118
What are papillae? What are their functions? What are the types
elevations of the tongue that contain taste buds
- increase SA and provide rough texture
Vallate - 12 large
fungiform - scattered across entire surface of tongue
foliate - leaf like, degenerate in childhood
filiform - entire surface of mouth
- tactile receptors but NO TASTE BUDS
- increase friction to move food
119
What happens when tastings are dissolved in saliva?
can make contact with gustatory hairs - sites of taste transduction
produces receptor potential - simulates exocytosis of NT to trigger nerve impulses
receptor potential arises differently for different tastings
ex. salt Na causes depolarization
120
how long does taste adaptation last?
```
1-5 minutes of continuous stimulation
due to changes in
- taste receptors
- olfactory receptors
- neurons of the gustatory pathway in the CNS
```
121
What three cranial nerves contain axons of the first order gustatory neurons? What is its pathway to the primary gustatory area? What are other places it projects to?
Facial (VII) ant 2/3 tongue
Glossopharyngeal (IX) - post 1/3
vagus (X) - throat and epiglottis
all project to gustatory nucleus in medulla, then thalamus then 1 gustatory area on insula
some project to the hypothalamus and limbic system
122
Axon collaterals of the optic ganglia project to the midbrain and the hypothalamus. What do they do there?
midbrain - constriction of the pupils, coordination of head and eye movement
hypothalamus - patterns of sleep, circadian rhythms
