Physiology special senses

withdrawal reflex

-spinal -somatic(bc skeletal m is effector) -polysynaptic(more than 1 synapse) -innate(born w it)

draining of aqueous humor

caused by parasympathetic nervous system activation bc muscarinic cholinergic (ACh) receptors cause contraction of the ciliary mm that move structures out of the way to expose canal where the aqueous humor can leave the anterior chamber -prostaglandins also cause relaxation of the ciliary mm causing reabsorption of the aqueous humor

In the absence of light, Glutamate, an amino acid neurotransmitter is released from the rod. Thus, the voltage gated calcium channels on the rod must be:

open

The cation channel on the bipolar cell is ____ in the absence of glutamate.

open

pupil function

open hole that allows light to pass through

the axons in the ganglion cells form what nerve?

optic N cranial nerve 2

neural layer is further divided into:

outer, middle, and inner layer

Where are photoreceptors located?

outermost layer of the neural layer

Nociceptors

pain receptors sensitive to tissue damage

antagonists m example

biceps contract when triceps relax(not 100% relaxed bc we need some to contract to stabilize the joint)

optic disc

bind spot/ where optic N leave the eye

corneal reflex

blinking response

once an action potential has been generated on the ganglion cells the action potential must travel to the ______

brain so that it can interpret the sensory info

cyclic nucleotide gated (CNG) sodium channel function

cGMP messenger binds to Na+ channel causing it to influx

Transduction

the process of changing an environmental stimulus into the electrochemical signals of the nervous system

Phototransduction

the process of converting light waves into an electrical signal -occurs in neural layer of the retina

two-point threshold

the smallest distance between 2 points that can be sensed as separate stimuli, instead of a single point

what if there was a decreased affinity for the cis-retinal and opsin in the rods?

they would be more sensitive to light bc they are now their rhodopsin is more likely to dissociate (bleach) in the presence of light -it's easier to trigger this pathway

A lack of perilymph would cause

sensorineural deafness

Glaucoma treatment

-beta 2 antagonist- will block cAMP -alpha 2 agonist- will also block cAMP production -pilocarpine -parasympathomimetic

near by object accommodation

-ciliary m contracts -suspensory lig slackened -lens allowed to bulge -decrease focal length

distant object accommodation

-ciliary m relax -suspensory lig tightens -lens pulled in thin/flat -increase focal length

on bipolar cell membrane

-metabotropic glutamate ligand gated receptor(slow involving G protein) -cation channel -K+ leak channel

sneeze reflex

-particles in nostrils stimulate receptor -receptor is triggered on sensory neuron generating AP -integration center is brain stem so brain reflex -efferent neuron is motor neuron AP effector Is diaphragm m -somatic bc skeletal m -brain, innate, somatic

vitreous humor function

-provides nutrients to lens -coordinating eye growth -supports retina

players in phototransduction:

-rhodopsin -transducin-G protein -cGMP- 2nd messenger -phosphodigesterase (PDE) -cyclic nucleotide gated (CNG) sodium channel -K+ leak channel -glutamate

When a rod is hyperpolarized:

-voltage gated Ca channels remain closed so no Ca influx -no exocytosis of glutamate to bipolar cell -G protein wont be activated on bipolar cell -cation channel remains open on bipolar cell so Na+ influx occurs (bc greater electrochemical driving force bc cell is already neg) -this will generate a EPSP on the bipolar cell -becomes action potential on ganglion cell -axons of ganglion form the optic nerve and it crosses over at optic chiasm -then goes to thalamus -then goes to visual cortex

Bitter taste

1. Alkaloids (bitter molecule) binds to a receptor on the taste bud 2. this activates IP3 2nd messenger system 3. this causes an influx of calcium ions from the endoplasmic reticulum 4. this calcium influx depolarizes the cell and causes NT to be released from taste bud 5. NT binds to ligand gated receptors on afferent neurons

umami taste

1. glutamate binds to metabotropic receptor 2. g protein is activated and IP3 2nd messenger system is activated

phototransduction in the light

1. light stimulates rhodopsin(bleaching occurs) and activates G-protein transducin 2. Activated transducin will stimulate cGMP phosphodiesterase 3. phosphodiesterase will break down cGMP (low levels of cGMP inside cell) 4. less cGMP is binding to sodium channels so they close (less sodium influx) 5. K+ will still be leaking out of the cell more K+ eflux than Na+ influx so rod is hyperpolarized

retina layers

1. retinal pigmented epithelium (outermost) 2. neural layer (innermost)

phototransduction in absence of light

1. rhodopsin isn't dissociated so transducin isn't activated 2. therefore, phosphodiesterase isn't activated so we aren't breaking down cGMP 3. high levels of cGMP 4. cGMP binds to cyclic nucleotide gated (CNG) sodium channels opening the channel 5. Na+ influx into the rod and K+ eflux (but greater driving force for Na+) 6. Na+ infux is depolarizing the rod 7. on axon terminal of the rod the voltage gated calcium channels will open so Ca influx 8. this triggers release of NT glutamate 9. glutamate binds to metabotropic glutamate ligand gated receptor on bipolar cell activating G protein 10. alpha slides over via direct coupling and closes cation channel 11. K+ leak channel is still open so K+ eflux but NO cation influx (net pos. leaving the cell) resulting in an IPSP on bipolar cell 12. this prohibits axon potential from being generated on ganglion cell and therefore no message/signal is transported to the brain (makes sense bc we are doing this with no light so no signal should be reaching the brain)

reflex arc components

1. stimulus 2. receptor 3. sensory N 4. CNS 5. relay neuron 6. motor N 7. effector 8. response

sweet taste

1. sugar molecule (like sucrose) binds to a receptor on taste bud 2. this activates cAMP 2nd messenger system 3. protein kinase A closes potassium channels to depolarize the cell

where does the spinothalamic tract decussate?

2nd order neuron crosses over as soon as it enters the spinal cord

Where does the dorsal column decussate?

2nd order neuron crosses over in medulla

What happens when the stereocilia bend away the kinocilium?

Potassium channels close

What type of receptors detects where the body is in 3-D space?

Proprioceptors

opsin

The protein part of the rhodopsin that determines the wavelength of light that will be absorbed -contains retinal

The activation of a G-protein linked receptor from L-glutamate binding to it will cause what taste?

Umami/savory

how can we explain an increased perception of light?

a neurotoxin that prevented the voltage gated calcium channels on the photoreceptor from opening -this would mean less glutamate exocytosed and therefore more cation channels can stay open on the bipolar cell which will cause an EPSP

chemoreceptor

a sensory receptor that responds to specific chemicals

retinal pigmented epithelium function

absorbs extra light which prevents light from scattering and reduces glare; provides nutrients and oxygen to the retina

retinal

absorbs photon of light 2 forms: -cis -trans a chemical synthesized from vitamin A

alzheimers disease causes the gradual death of cholinergic neurons how can we help?

administer an acetylcholinesterase inhibitor -bc we have less acetylcholine overall so we need to inhibit acetylcholinesterase the enzyme that breaks down acetylcholine this will increase ACh levels

cornea function

allows light to enter the eye

ossicles

amplification of sound

Where is the aqueous humor located?

anterior chamber

light passes through the cornea and into the __________ humor and through the _______ and the _______ and the __________ humor and to the ________ layer of the retina

aqueous, pupil, lens, vitreous, outer neural

What is a receptive field?

area on surface of skin that is monitored/innervated by a single receptor cell

What type of reflex goes to smooth muscle (involuntary muscle)?

autonomic

refraction

bending of the light as it enters the eye -light ray enters eye and bends as it passes through cornea goal: light rays to converge onto fovea centralis making SHARP image

interneuron

between afferent and efferent neurons -association neuron

synthesis of aqueous humor

caused by sympathetic nervous system activation bc beta 2 adrenergic receptors (NE/E) on the ciliary epithelium and activated cAMP system. -this opens chloride channels allowing chloride ions to leak into the anterior chamber which creates an osmotic gradient for water to follow in order to stop synthesis we need to block beta 2

cataracts

clouding of the lens

2 types of photoreceptors

cones and rods

Glaucoma

constantly making aqueous humor but not draining it

vitreous humor is not:

constantly synthesized and drained -born with set amount

iris function

constricts pupil in response to bright light dilates pupil in response to dim light

Organ of Corti

contains receptors for hearing

convex lens

converge, decrease focal length

phototransduction is ____________________ bc light hitting the photoreceptor causes a ____________ in the graded potential traveling to the ________ cell

counterintuitive, decrease, bipolar

presbyopia

decreased ability to accommodate due to lack of nutrients reaching inner fibers of the lens

hyperopia(far sighted)

decreased ability to accommodate due to weak lens

When the rod is ____ the bipolar cell creates a IPSP.

depolarized

corticobulbar tract

descending tract that controls voluntary motor movement of skeletal m -ipsilateral- stimulus on right side of body move right effector -brain stem

corticospinal tract

descending tract that controls voluntary skeletal m movements -spinal cord -contralateral- stimulus on right side of body move left effector -crosses over at pyramids

exteroreceptors

detects sensory info from outside of body -sight -smell -balance -hearing -taste -touch ex: somatosensory receptor in skin

interoreceptors

detects sensory info within the body -stretch in internal organs -pain in internal organs -proprioception ex: receptors that sense the increase in blood pressure in the aorta or carotid sinus

focal length

distance from lens to fovea centralis -can be altered by altering the shape of lens

concave lens

divergence, increase focal length

afferent neurons enter the spinal cord through what structure?

dorsal ganglion-> dorsal root-> dorsal horn

tectorial membrane

embeds stereocilia

Glutamate

excitatory neurotransmitter

Each gustatory taste receptor senses every type of taste sensation (e.g. salty, sweet, etc).

false, each TASTE BUD had taste receptors for every taste

when retinal absorbs light:

it changes from cis to trans retinal

lens function

focuses light on retina

basilar membrane

foundation upon which the Organ of Corti sits

aqueous humor function

gives nutrients to lens and maintains pressure

PTSD

high dopamine- pacing back and forth

sour taste

hydrogen ions flow into the cell through ion channel and block potassium ion channels -block K+ channels depol cell

In a hair cell, potassium is at a lower concentration in the ____

icf

scotopic sensitivity syndrome

interference of light wavelengths

astigmatism

irregularities of the cornea

The lesser the intensity of the sound, the ____ the deflection of the basilar membrane and the __ bending of the kinocilium.

less, less

What strikes the fovea centralis?

light

conductive deafness

loss of hearing due to a decrease in the effectiveness of the components of the external and middle portions of the ear that cause the fluid motion in the inner ear

sensorineural deafness

loss of hearing due to defects in the nervous transmission of the auditory signals

Parkinson's disease

low dopamine- can't control motor voluntary motor movements

accomidation

maintaining focus on an object as it approaches the eye -allows us to decrease focal length to see objects nearby adjusting strength of the lens by changing the shape of the lens -under autonomic control

sclera function

maintains the shape of the eye/ projections -outermost

why are some areas of the body more sensitive to touch than others?

more sensory neurons/ larger brain area devoted to it

Frequencies associated with higher pitches terminate where on the basilar membrane?

near the oval window

once light ray enters the neural layer it strikes the ________ in the outermost layer. This is where phototransduction occurs. A graded potential can be generated on the bipolar cells(middle layer) which can turn into action potentials on the ganglion cells (inner layer). The axons of these ganglion cells form the optic nerve and the point at which the optic nerve exits the eye is the optic disc (blind spot). The action potential then travel to the visual cortex of the brain, which is located on the _________ lobe.

photoreceptors, occipital

retina function

phototransduction -innermost

Where is vitreous humor located?

posterior chamber of the eye

Low levels of cGMP are bound to CNG channels in the ___ of light causing the CNG channel to __.

presence, close

what cortex of the brain is visual info processed?

primary visual cortex in occipital lobe

expulsion reflex

protect body from foreign things entering the body

rhodopsin

protein visual pigment in rods that is found in the plasma membrane of the optic disks within the rod -sensitive to light -gets bleached -made up of retinal and opsin components

choroid function

provides blood to eyeball (bc highly vascularized) -contains ciliary m, zonular fibers, lens, and iris

osmoreceptors

receptors that are sensitive to changes in the concentration of solutes or osmotic activity

thermoreceptor

receptors that are sensitive to heat or cold

when light stimulus goes away we:

reset rhodopsin -enzyme will convert trans retinal back to cis - a diff enzyme responsible for re-associating/re-setting opsin and cis retinal (full rhodopsin)

dorsal column system

sends fine touch and proprioception sensations to brain

spinothalamic tract

sends pain and temperature sensations to brain

Mechanoreceptors

sensory receptors that are sensitive to physical forces such as stretching, bending, or pressure

Photoreceptors

sensory receptors that respond to visible wavelengths of light

what type of tissue makes up the iris?

smooth m -pigmentation determines what colors of light are absorbed/reflected

salty taste

sodium ions flow through ion channel and into cell causing salty taste -sodium influx causes depol

proprioreceptors

specialized mechanoreceptors found in muscles and connective tissue that give the brain info on the position of the body in 3D spaces

fovea centralis

specialized region of the visual field that has the highest concentration of cones and highest visual acuity -sharpest vison

stretch reflex/knee jerk

spinal, somatic, innate 1st efferent neuron to quadriceps femoris is MONOsynaptic(excitatory contract) 2nd motor neuron to hamstrings is POLYsynaptic bc interneuron(inhibitory relax)

The __________________________ crosses-over (decussation) at the spot where it enters the spinal column.

spinothalamic tract

Contralateral reflex

stimulus and response are on opposite sides of the body

ipsilateral reflex

stimulus and response are on the same side of the body

baby reflexes are there for a few months and then they are gone therefore they are for _________ purposes

survival

The saying goes that your pupils expand by as much as 45% when looking at someone you love. Hence, the __ division of the ANS would be dominating.

sympathetic

aqueous humor is constantly

synthesized and drained

what structure in the brain is involved in ALL sensory pathways (except smell)

thalamus

why is stretch reflex spinal?

the brain isn't in the reflex arc but it can dictate the speed of it and it can interfere w stretch reflex

why can't glaucoma patients see?

the increase in intraocular pressure damages the optic N and therefore vision will decline bc optic N is the visual sensation main player -decreased blood supply bc pressure-> less O2-> cells die-> no ATP to the brain traveling along optic N to the visual cortex

In a patient with Presbyopia, their focal length is too ____ due to __ refraction

too long, less

myopia(near sighted)

too much refraction causing short focal length due to abnormally strong lens

Tympanic membrane

triggers malleus to vibrate

when the membrane potential for a neuron reaches -55mV, the voltage gated sodium activation gate opens and sodium influx occurs triggering a positive feedback loop for adjacent sodium activation gates to open. when activation gates ope this triggers the slow closing of the sodium voltage gated inactivation gates and the slow opening of the potassium voltage gated channels

true

where do upper and lower somatic motor (efferent) neurons synapse?

ventral horn in spinal cord

stapes

vibrates oval window

what MUST you have to reset rhodopsin?

vitamin A -temporarily stored in the retinal pigment layer of the retina -long term stored in the liver

frontal lobe:

voluntary motor activity

what happens when we lack vitamin A?

we're going to be less likely to re-associate opsin and cis retinal THEREFORE less likely to perceive a new stimulus

bleaching/dissociated

when opsin and trans retinal are separated -caused when retinal absorbs photon of light and goes under configurational change and turns to trans

if we cannot reset rhodopsin:

you wont be able to see another thing bc rhodopsin is busy responding so it won't be able to detect any new stimuli coming into the eye