mamm. phys. exam 2!!

sensory cells: relationship between stimulus intensity and receptor response….

• semi-logarithmic

• threshold sensitivity

• maximum cell receptor response

modality

= sensory quality! (type of receptor)

• anatomically specific

• connected to CNS!!

*NOT coded for by AP’s

range fractionation

different cells have overlapping sensitivities… which extends dynamic range!

tonic vs phasic receptors

tonic: slow adapting

• constant firing rate as long as stimulus is applied

phasic: fast adapting

• firing rate (# of AP’s) decreases w/ constant stimulus

5 basic tastes

salty, sour, sweet, bitter, umami

sensory transduction by taste receptor!

• closes K channel… Na+ and Ca²⁺ enter the cell!

• more depolarization… more APs!

• more NT release

sweet & umami:

bitter:

salty:

sour:

sweet & umami: binds to membrane receptor, close K+ channel!!

bitter: binds to membrane receptor, Ca²⁺ released from ER!

salty: Na+ thru ion channel, opens Ca²⁺ channels!

sour: H+ thru ion channel, opens Ca²⁺ channels!

chemosensory coding: 2 types!

1. labeled-line coding = limited range of stimuli & direct neural line …. receptors are specialists!

2. across-fiber pattern = wider range of stimuli & contributes to perception …. receptors are generalists!

olfactory!!

• receptor cells= bipolar neurons w/ cilia

• bowman’s gland = odorant-binding proteins

• project from nose directly to cortex!

• 25,000 receptor cell axons synapse on 25 mitral cells… large conversion of signals!

• 350 functional genes coding for different receptors… each gene for one receptor!

equilibrium pathways

directly to cerebellum ; indirectly to cortex (via thalamus)

all other pathways?

must pass thru thalamus before projecting to their relevant area

Somatotopic order…

more brain area = more info processing = more important!

visible light range?

400 - 700 nm

fovea

eye! highest density of photoreceptor cells

rhodopsine=

rod cells:

cone cells:

opsin + retinal

rod cells: black/white, 1 type of opsin

cone cells: red/ blue/ green, 3 types of opsin

which retina form binds opsin

kinked (cis) retina form binds opsin … purple

straight (trans) retina form detaches from opsin …. clear

Which best describes lateral inhibition in the somatic sensory system?

The precision of locating a stimulus is increased by inhibiting signaling along nearby, parallel pathways

…. this sharpens the signal by inhibiting neighbors!

special vs somatic sense

Special senses are localized to specific organs (the ears, in the case of sound) and are mediated by specialized cranial nerves. Somatic sensations (also called "general senses") are processed by the somatosensory system and are distributed throughout the body rather than being confined to a single specialized organ

anterolateral vs dorsal column

Accommodation for near vision requires

Multiple Choice

• flattening of the lens.

• contraction of the ciliary muscles.

• activation of the sympathetic nervous system.

• increased rounding of the cornea.

• dilation of the pupil.

• contraction of the ciliary muscles.

rods vs cones location

cones = fovea

rods = spread around retina

combinational code for odor:

analogous to english alphabet

• odorants are coded for by a combination of activated receptor cells!!

order that light passes thru

light → optic nerve fibers → neurons → photoreceptors (rods and cones)!

90% of retinal projections go to ____, the other target is ____

LGN - lateral geniculate nucleus

other target = superior colliculus

photoreceptors in vertebrae retina

outer segment= pigment in membrane disks

inner segment= organelles, ATP production (rods/ cones)

synaptic terminal= synapses w/ bipolar cells

light starts HERE!!!! ^

rod’s signal transduction pathway

Na+ channel opened by cGMP increase… depolarization! (which releases inhibitory NT glutamate) = NO graded potential of bipolar cell = NO ATP in ganglion cell!!

however….

if cGMP decreases …. Na+ channel closes (hyperpolarization!!) = NO inhibitory NT release, instead releases excitatory NT! which stimulates ATP in ganglion!

photoreceptor cell in light vs dark

light= no IPSP, bipolar cell depolarizes, AP!

dark = IPSP in bipolar cell, no AP!

IPSP vs EPSP

IPSP= hyperpolarization of a neuron's membrane potential caused by the flow of negatively charged ions into the postsynaptic cell. It decreases the likelihood of a neuron firing an action potential, acting as a "brake" on neural activity to regulate nervous system function.

EPSP= a temporary, graded depolarization of a postsynaptic neuron membrane caused by the inflow of positive ions (usually or ) when excitatory neurotransmitters, such as glutamate, bind to receptors. This shift makes the neuron more positive and likely to fire an action potential

direct (vertical) vs indirect (lateral) neural pathways!

direct (vertical): receptor, bipolar, ganglion cell

indirect (lateral): receptor, horizontal, bipolar, amacrine, ganglion cell

lateral inhibition?

lateral inhibition = inhibiting neighbors to create contrast enhancement of stimulus!

when is ganglion cell active vs inactive?

active = light shines on center

inactive = light shines also on surround area

size of cone/ magnitude of receptor response for red, blue, green… also which colors are s3x linked?

red= long

green= medium

blue= short

red and green = s3x linked

rods vs cones…. slow vs. fast, pigments, day vs. night vision

rods= fast! rhodopsin! night vision!

cones= slow! green/red/blue! daylight!

pitch vs intensity

pitch= frequency

intensity= amplitude

hair cell transduction (force away vs towards, shear, and tip links!)

force towards kinocilium → more NT release

force away from kinocilium → less NT release

*movement of basilar membrane relative to tectorial membrane = shear on the cilia of hair cells!

tip links= connects transduction channels (cation channels on hairs)

do you get hyperpolarization or depolarization when K+ flows thru the tip links?

depolarization! (role reversal of Na and K compared to AP; b/c endolymph outside cilium has higher K+ than inside cilium)

sound waves on basilar membrane (high vs low frequency)

high frequency/ pitch = move membrane closer to stapes (base; near round window) .. stiff

lower frequency/ pitch = sounds closer to distal end (apex) … flexible

what is sound loudness determined by??

• degree of displacement

• AP frequency

muscle types= (striated vs non-striated and voluntary vs involuntary)

skeletal

smooth

cardiaac

skeletal: striated and voluntary

smooth: non-striated and involuntary

cardiac: striated and involuntary

functions of muscle (5)

voluntary movement

control of body openings

maintain posture

communication

maintain body temperature

Sliding filament theory

myosin slides along actin; Z-lines move closer together and sarcomeres shorten

where is the actin-binding site on myosin?

on the heads / cross bridge!