Section 1 Flashcards
How does a receptor send a signal to the CNS?
stimulus strength dictates AP frequency
receptor threshold dictates sensitivity to stimulus
tonic receptors
continues to send APs with continued stimulus
ex. nociceptors and prociceptors
phasic receptors
send AP with initial stimulus and with removal of stimulus
no signal with continued stimulus
ex. touch receptors
receptive field
area covered by one receptor
large -> more sensitive, less discriminatory
stretch reflex
stretch detected
afferent signal back to spinal cord
activates motor neuron of stretched (agonist) muscle
leads to muscle contraction of agonist
also activates inhibitory interneuron
inhibits activation of motor neuron for antagonist muscle
leads to relaxation of antagonist muscle
deep tendon reflex
receptor: golgi tendon organ
purpose: protect against over contraction
stimulus: tension in tendon
response: relaxation of muscle contraction (agonist), activation of antagonist muscle
flexor(withdrawal) reflex
receptors: nociceptors
purpose: move away from dangerous stimulus
stimulus: pain
response: flexor muscles cause withdrawal
taste cells
Taste receptors, not the neuron
Have several gustatory hairs (microvilli) to increase surface area
gustatory supporting cells
to give shape to taste buds
gustatory basal cells
stem cells to replace taste cells
papillae
gives rough texture
often contains taste buds
filliform
provide friction
circumvallate
form V on back of tongue
fungiform
smaller round, more abundant
anterior 2/3 of the tongue
taste buds
taste pore to let chemicals in
sweet taste
sugars, alcohol, some amino acids, and lead
salty taste
metal ions ex. NaCl
sour taste
Acids ex. H+
bitter taste
alkaloids ex. caffeine, morphine, nicotine, narangin
100x more sensitive to bitter than sour
Umami(savory) taste
amino acids(especially glutamine) meats
minty flavors
cold receptors
spicy flavors
capsacin lowers threshold for warm receptors -> feel hot in mouth and all over the body
taste pathway
specialized membrane receptors open to certain chemicals
cause depolarization(some second messenger, some directly producing action potentials)
leads to AP on sensory neurons
synapse in medulla
synapse in thalamus(integration with other sensations except smell)
ending in gustatory cortex(parietal lobe by temporal lobe)
olfactory receptor cells
bipolar neurons constant turnover(60 day lifespan)
olfactory supporting cells
surrounding olfactory cells, provide stability and shape
olfactory basal cells
stem cells for olfactory receptors
olfactory pathway
molecules bind to membrane receptor
starts second messenger system
opens ion channels
depolarize olfactory neuron
olfactory nerve stimulates nuerons in olfactory nerve(in olfactory bulb)
one tract goes to olfactory cortex of the frontal lobe
also sent to hypothalamus(emotional response) and limbic system (memory: hippocampus, emotions)
right nostril: more emotional connection
left nostril: more accurate
eyebrow function
shade and catch sweat
eyelid function
spread lubricants and protectant
tarsal gland function
secrete oily solution lubricates eye movements
conjunctiva
mucous membrane lining the inside of the eyelids
keeps eye moist
lacrimal gland
part of lacrimal apparatus
makes and secretes tears
stimulated by facial nerve VII
tears made of?
mucous: moistens, lubricates, protects
antibodies: destroy microorganisms
lysozymes: destroy bacteria
sclera function
fibrous tunic
outer white part
shapes eye, attachment for muscles
cornea function
fibrous tunic
anterior portion
bends light, protects
choroid function
vascular tunic
posterior region, contains pigment cells
absorbs light and minimizes scattering, supplies blood
cilliary body function
vascular tunic
anterior region, smooth muscle under parasympathetic control (Oculomotor III)
controls lens shape
cilliary process function
vascualr tunic
secrete aqueous humor to fill anterior part of eye
Iris function
vascualr tunic
pigment part
determines pupil size
pupil function
vascular tunic
central hole
determines how much light enters eye
parasympathetic activation
oculomotor III -> contracts pupillary sphincter muscle -> constricts pupil for: near vision/protection -> less light
sympathetic activation
contract pupillary dilator muscle -> dilate(not a cranial nerve) -> far vision/stress -> more light, more vision needed
sensory tunic(retina) function
pigmented layer against the choroid function
prevent light scatter; help replace photoreceptors
region of the retina: fovea centralis
packed with cones
high visual acuity
point of focus
region of retina: blind spot AKA optic disc
point where optic nerve II leaves the eyeball
no photoreceptors
regions of the retina: periphery
sides of eyeball
many rods
very sensitive to light
low resolution
lens function
elastic
focuses the image
-changes the degree of light/bending refraction
posterior segment function
contains vitreous humor
retains shape of eye, holds lens and retina in place, transmits light
extrinsic eye muscle
originate within orbit and insert into sclera
types:
- recti(straight muscles)
- obliques(curved muscles)
superior rectus
moves eye up, CN III
inferior rectus
moves eye down, CN III
medial rectus
moves eye in or medially, CN III
lateral rectus
moves eye out or laterally, CN III
superior oblique
pulls front of eye downward and lateral
helps with rotation, CN IV
inferior oblique
pulls front of eye upward and lateral
helps with rotation, CN III
rods
function: light receptors for dim light and peripheral vision more sensitive to light than cones no color large receptive field low resolution more numerous than cones(~100 million)
cones
function: specialized to detect color
small receptive field, not as sensitive
~5 million in fovea centralis
difference between rods and cones are wired to bipolar and ganglion cells
can have up to 100 rods for each 1 ganglion cell. Usually 1 or 2 cones per ganglion cell
light for close object
lots of divergence
light for far objects
mostly parallel light waves that reach eye
near objects, pupil size and lens shape
pupil size small, lens is more convex
far object, pupil size and shape
pupil opens up to get more light, lens more concave
cilliary muscle
circle around lens
- contraction -> allows lens to become more convex
- -relaxation -> pulls lens out, less convex
suspensory ligaments
Connect lens to ciliary muscle
Contraction (of ciliary muscle) -> loose
Relaxation (of ciliary muscle) -> tight
lens
naturally more convex, but can be stretched
focusing: near vision
light rays are: divergent -> need much bending
lens: CN III -> contract ciliary muscles -> lens gets more convex
pupil: CN III -> contract pupillary sphincter muscle -> constrict pupil -> less light enters eye, more parallel beams
eyeball: contract medial rectus muscles for eye convergence
focusing: far vision
light rays are: parallel -> need little bending
lens: ciliary muscles relax -> lens flattens out
pupil: dilates via less CN III activation and/or sympathetic nervous system activation -> relax pupillary sphincter muscle and/or contract pupillary dilator muscle -> pupil dilates
eyeballs: divergence via lateral rectus
myopia
can’t see far
cause: long eyeball
correction: concave
Hyperopia
can’t see near
cause: short eyeball
correction: convex
astigmatism
multiple focal points
cause: irregular shaped lens or cornea
correction: cylindrically shaped lens
presbyopia
lens lose elasticity
doesn’t become convex
harder to see up close
external ear: auricle
collects sounds, helps determine direction of sound
external ear: Auditory Canal (external auditory meatus)
-Passageway to middle ear
– Contains ceruminous glands
middle ear: Tympanic membrane (eardrum)
transmit sound from external ear to middle ear
middle ear: Malleus (hammer), incus (anvil), and stapes (stirrup)
transmit sound from eardrum as vibrations to the inner ear
middle ear: pharyngotympanic membrane
Pressure regulation in middle ear. Pressure must be equal on either side of the ear drum or sound is distorted
internal ear: semicircular canals
awareness of rotational movement in space
internal ear: vestibule
awareness of position of head relative to gravity
awareness of linear movements of the head
internal ear: cochlea
hearing
internal ear innervated by?
CN VIII
vestibule
linear movement of head and position of head with respect to gravity
