Biol 373 Unit 3b

Olfaction (smell)

Most primal sense. 1 of 2 chemoreception senses

Olfactory Neurons

Only detector cells to be neurons. By passing thalamus and going straight to brain.

Olfactory Neurons cross the midline

False. They go directly to brain

olfactory bulb

Where the olfactory nerve synapses.

olfactory cortex

most posterior in animal's brain

what are the shape of olfactory neurons?

they are true bipolar

what kind of cilia is found in the olfactory pathway?

Non motile cilia

How many times are olfactory receptor neurons replaced?

every 60 days

what type of receptors are odorant proteins?

GPCRs one of the largest families in vertebrates

There are 100s of different types of receptors.

False. There are 1000s.

How many types of odorant receptor protein does each olfactory neuron express?

1

how many odorant can each receptor recognize?

1+

How many receptor can each odorant stimulate?

more than 1.

gustation (taste)

1 of two chemoreceptor senses. Second most primal sense.

What are the five basic tastes?

sweet, sour, salty, bitter, umami

taste receptor cells are neurons

False. They are non-neural epithelial cells

how often is the turn over rate of taste receptor cells?

10 days

Where are taste receptors located?

taste buds

why is it difficult to say that taste receptor cells synapse

The direction is backwards

what is the signal molecule produced in gustation?

ATP

what kind of junction joins taste receptor cells

tight junction

what kind of receptors do sweet, umami, and bitter ligands bind to?

GPCRs

Transduction of sour taste is similar to sweet.

False. Not as simple. calcium is present

Science knows little on how sodium is detected.

true

tympanic membrane

The eardrum. A structure that separates the outer ear from the middle ear and vibrates in response to sound waves.

bony ossicles

malleus, incus, stapes; deliver sound waves and controls movement of eardrum

oval window

membrane at the enterance to the cochlea through which the ossicles transmit vibrations

What is the relative amplitude of the sound pain threshold?

10 000 000 (140 decibels)

choclea

a coiled bony fluid-filled tube in the inner ear thru which sound waves trigger nerve impulses

what is the fluid found in both the vestibular and tympanic duct?

perilymph

cochlear duct

in between vestibular and tympanic duct filled with endolymph

Where are sensory receptors located?

inside cochlear duct

What is the job of the round window

to release pressure

Organ of Corti

Center part of the cochlea, containing hair cells, canals, and membranes

what is perilymph?

fluid similar to plasma (high sodium, low potassium)

what is endolymph?

found in cochlear duct is similar to intracellular fluid has low sodium and high potassium

What do hair cells synapse with?

primary afferent neurons

tectorial membrane

A membrane located above the basilar membrane; serves as a shelf against which the cilia of the auditory hair cells move

kinocilium

This is a large hair cell important in the detection of the head's position. Whether the displacement of the stereocilia is towards or away from this determines whether it is excitatory or inhibitory.

stereocilia

(modified microvilli) small hair like projections on the tops of inner and outer hair cells

what kind of channels are found in hair cells?

K+ channels

Which way do stereocilia move in order to inhibit action potentials

to the left

How is pitch determined?

By which area of the basilar membrane vibrates

place code hypothesis

the accepted theory that pitch is determined by which part of the tonotopic map is stimulated

temporal code hypothesis

the theory that fequency of sound wave determines fequency of action potentials perceived as pitch

in the temporal code hypothesis what is low frequency sound associated with?

slow waves along basilar membrane = low pitch

what is the problem with the temporal code hypothesis

we can hear sounds up to 20000 Hz however no neuron can transmit at this rate

what is the maximum rate of action potentials in mammals

1000 AP/sec

the cerebellum does not get auditory information

false. after synapse some info goes to cerebellum

all auditory signals synapse and cross over

false some do not!

three ways that contribute to hearing loss

conductive, central, sensorineural

Conductive hearing loss

no transmission thru either external or mid ear (repairable)

central hearing loss

damage to neural pathway between ear and cerebral cortex or damage to cortex itself (stroke and rare)

sensorineural hearing loss

the most common form of hearing loss, also called nerve deafness; caused by damage to the cochlea's receptor cells or to the auditory nerves

mammalian hair cells are replaceable

no only vertebrates that do not regenerate lost hair cells

Equilibrium is managed by which part of ear?

vestibular apparatus

what are two components of equilibrium?

dynamic- movement thru space

static- position of head

otolith organs

utricle and saccule

semicircular canals

three canals within the inner ear that contain specialized receptor cells that generate nerve impulses with body movement

How many semicircular canals are there?

3 (anterior, posterior, lateral)

ampulla

dilated portion of a canal or duct holds sensory cells

cupula

A gelatin-like structure containing a tuft of hairlike sensory receptor cells in the semicircular canals.

utricle

forward/backward acceleration, head tilt

saccule

vertical acceleration

otoliths

small crystals in the fluid-filled vestibular sacs of the inner ear that, when shifted by gravity, stimulate nerve cells that inform the brain of the position of the head

Canal of Schlemm

duct in the anterior chamber that carries filtered aqueous humor to the veins and bloodstream

optic nerve

the nerve that carries neural impulses from the eye to the brain

optic chiasm

point at which optic nerve fibers cross in the brain

optic tract

leads from optic chiasma to terminate in lateral geniculate body

integrating centre for pupillary light reflex

thalamus/brainstem (midbrain)

efferent neurons for pupillary light reflex

motor neurons travelling in oculomotor nerve

effectors for pupillary light reflex

smooth muscles regulating pupil diameter

pupil constriction

parasympathetic

pupil dilation

sympathetic

does visual info cross the midline

yes and no

consensual light reflex

simultaneous constriction of the other pupil

Phototransduction

conversion of light energy into neural impulses that the brain can understand

Photoreceptors

rods and cones, modified ganglion cells

macula

= stain

special area of retina where we try to focus light by head tilts for fine vision

optic disc

Region at the back of the eye where the optic nerve meets the retina. It is the blind spot of the eye because it contains only nerve fibers, no rods or cones, and is thus insensitive to light.

humans are the only ones with inverted vision

no all vertebrates do

which cells go to the optic nerve

ganglion cells

horizontal and amacrine cells

Facilitate or inhibit communication between photoreceptors and ganglion cells

Alter sensitivity of retina

Ganglion cells in the retina

-connect with bipolar cells

-axons project to the brain via optic nerve

-only cells to produce action potentials

All retinal cells generate action potentials.

a. true

b. false

false. only ganglions. all others are non-spiking cells

graded potentials are used in short distances

true hence why long ganglions use action potentials

fovea

the central focal point in the retina, around which the eye's cones cluster used in fine vision

only part of eye with direct access to photoreceptor cells, only cones present, in macula

fovea

level of convergence in fovea

1:1 ratio

fovea resolution

high resolution small receptive field, high intensity signal

resolution of rods

poor resolution (low acuity) high sensitivity, low light

what photoreceptors detect color?

cones

ends of rods

modified cillia

first GPCR discovered from bovine eyes

rhodopsin= protein expressed by rod cells

retinal in the dark

11-cis-retinal is bent due to orientation of 11=12 double bond

retinal in the light

retinal is converted to an all-trans form which CLOSES sodium channels and is hyperpolarized

prevents the release of glutamate which originally inhibits bipolar cells

in the dark rhodopsin is... cGMP is... CNG and K+ channels are...

inactive, high, and open, depolarized

in the light rhodopsin is... cGMP is... CNG channels are... Cell is...

opsin is activated, cGMP is low, CNG is closed, hyperpolarized

dark current

the inward positive sodium current that occurs in photoreceptors in the dark

opsin bleaching

loss of retinal on opsin