Sensation-Neuro!!

what is the purpose of somatosenation?

take outside info and bring into the brain-transduction

What are receptor cells?

cells that respond to outside stimuli

What are mechanoreceptors?

receptors sensitive to physical distortions

What are merkel’s disks and meissner’s corpuscles?

light touch mechanorecptors-they are smaller and surface level. Less info but more detailed.

What are ruffini’s endings and pacinian corpuscles?

they are responsible for harder touch, bigger and deeper

What do mechanoreceptors respond to?

change- when corpuscle is disturbed

When pacinian corpuscles initiate a receptor potential?

when stimulated (physically indented)

How do mechanosensitive ion channels work?

physical disruption opens channel pores to allow ions to flow in/out of cell

What are the 2 was physical disruption can open these channels?

directly (pressure opens it), or indirect (pressure moves protein which then opens channel)

What is an afferent axon?

nerve fibers that enter through dorsal root and carry mechanoinformation to spinal cord.

what are dorsal root ganglion cells?

pseudo uni polar cells that send one long neurite into skin and other to spinal cord

How many spinal segments are there?

30, they are organized into 4 groups (cervical, thoracic, lumbar and sacral)

What is a dermatome?

strip of skin that sends info to one spinal segment (30 of them)

What type of virus is shingles?

a virus that can infect a single dorsal root ganglion producing a rash on a single dermatome

Where does somatosensation info from the spinal cord go?

it goes to the somatosensory cortex (its like a head band)

How is the somatosensory cortex organized?

in a somatotropic map (each part receives specific info) -not all parts are equal

When does phantom limb syndrome happen?

when you use a different part-this happens because that spot grew into the space the old body part took up was taken over

Where does information from somatosensory cortex go?

to the parietal cortex-which is in charge of touch and sensation

What is asterognosia?

can’t recognize by touch-damage to parietal cortex

What is neglect syndrome?

part of visual field is ignored/suppressed because of damage to parietal cortex

What is a nociceptor?

receptor in skin that transduces into brain pain signals

What type of axons are nociceptors connected to?

Abeta fibers and C fibers

Are mechanoreceptor axons myelinated or unmyelinated?

heavily myelinated (faster transmission)

What is the difference between Abeta and C fibers?

Abeta is more myelinated and C fibers are less

Where do signals go?

to axons which enter spinal cord through dorsal root ganglia

How do pain signals travel?

pain immediately crosses over to other side of the body. Then it goes to zone of lissaver after it goes to substantia gelatinosa

What is visceral pain?

pain in the organs in your body

What is cutaneous pain?

poin on skin

What is cross talk?

the mix up of visceral and cutaneous pain because they take the same path

What is referred pain?

when you feel pain in other places than where they’re actually coming from

Why does rubbing the site of pain work

because the activation of mechanoreceptors inhibits nociceptor signals in the spinal cord

What is periaqueductal gray matter (PAG)?

part of the brain that inhibits nociceptor signals in the spinal cord

How does the PAG inhibit nociceptor signals?

it sends axons into the synapses in the raphe nuclei of the medulla (which is responsible for serotonin synthesis). Theses raphe neurons then suppress pain signals in the spinal cord

How do opioids work?

They bind to opioid receptors in the PAG and dorsal spinal cord to inhibit these pain signal

What are the receptors that respond to temperature changes?

thermoreceptors

What are the hot receptors called?

TRPV1

What are the cold receptors called?

TRPM8

What are some endogenous chemicals that activate thermoreceptors?

capsaicin (heat in spicy foods) and menthol (cold in mint)

What is the difference between the dorsal root and the dorsal column?

root=everything and column=pressure and vibration

What is the dorsal column medial lemniscal pathway?

it is the way that pressure and vibration information goes

Dorsal vs Ventral

dorsal=back and ventral=front (closer to stomach)

Which way does pain travel?

up the ventral part of the spinal cord

When does pressure and vibration information decussate?

this info stays on the same side and decussates (crosses over) in the brain stem, then it is relayed to thalamus and then to somatosensory cortex

If the life side is severed in the spinal cord, what side will pain not be felt on?

the right side

Contralateral vs ipsilateral?

opposite side and same side

For pressure and vibration signals coming from the neck down what path do they take?

the dorsal column medial lemniscal pathway

For pressure and vibration signals coming from above the neck what path do they take?

the trigeminal touch pathway

How does the trigeminal touch pathway work?

the trigeminal nerve carries sensory info to trigeminal nucleu in pons. Then the info decussates and ascends to the thalamus and the somatosensory cortex

What is sound?

vibration that causes molecules in the air to compress and decompress

What is pitch?

the speed of compression

What are hertz?

the # of times molcecules compress per second

What is the human range of pitch?

20-20,000 hz

What are high frequency sounds?

high pitch (flute)

What are low frequency sounds?

low pitch (tuba)

How can low-frequency sounds be perceived as vibrations?

when processed through the dorsal column pathway-our bodies make sounds like this

How does sound travel through the ear?

compressed air enters the pinna which vibrates the tympanic membrane which vibrates the ossicles which then move the oval window which disturbs fluid in the ear and moves hair cells.

What are the names of the ossicles?

hammer, anvil and stirrup

How is sound amplified in the ear?

through the activation of these ossicles which act like levers

Why do we need to amplify vibrations?

because the fluid in the ear is hard to move

How does air from the nasal cavities reach the inner ear?

through eustachian tubes-which are usually closed

Why do your ears pop with increased elevation?

the air pressure changes but the tubes are closed so ears pop (opening the eustachian tubes) to release the pressure of having differing pressures

What 2 things does the inner ear control?

balance and hearing

What is the cochlea?

spiral orage, there are 2 holes oval window and round window

What is the basilar membrane?

membrane that hair cells are on, it is thin and stiff at the front and gets wider and floppier as it goes back. This is way the basilar membrane is tonotropic. Low sounds move the back easier.

What are hair cells?

special sound receptors that reside in the organ of Corti on top of the basilar membrane. They hyperpolarize/depolarize when they are physically moved.

How is the signal from the hair cells sent to the brain?

When the hair cells bend, tip-links physically open ion channels, and since potassium is concentrated outside of the cell in these cells they bring in K+ which depolarizes the cell which then causes an influx of calcium which cuses glutamate to be released into synapses between hair cells and neurites which connect to the cranial nerve which brings the signal to the brain

What kills hair cells?

loud noise, heavy metals, acidity and they do not regenerate

What happens once the sound signal reaches the brain?

it goes to the thalamus, the goes to the auditory cortex. The auditory cortex also has a tonotopic map. The auditory cortex sends sound localization info to parietal cortex-this then guides behavior.

What is the visual field?

the amount of space that can be viewed by retina

How do images in the retina look?

flipped and warped

What is the macula?

area at the center of the retina for high-res color vision-fovea=highest quality part (this has lots of cones)

What is macular degeneration?

age-related medical condition from destruction of the macula, it causes blurry vision, decreased visual accuracy, and visual hallucinations

Why do visual hallucinations happen with macular degeneration?

because the brain makes things up because it thinks something should be there (you see with your brain)

What does the lens do?

refracts light

What causes nearsightedness and farsightedness?

near=too long eye and far=too short eye

What are the 2 photoreceptors?

rods and cones

What do rods do?

light sensitive, night vision, one color vision, they are responsible for luminance (brightness)

What do cones do?

red, green, and blue light, less sensitive to light, more detail, responsible for chrominance

What type of chromats are most people

trichromats, though some people are dichromats (color blind), and some are tetrachromats (mostly only women)

What are hemifields?

sides of vision (left and right)

How does info from visual field go to brain?

through optic nerve

Nasal vs temporal?

close to nose and close to head

What is the optic chiasm?

where optic nerves meet-when they cross sides and become responsible for one hemifield of information

If the right optic nerve is severed what would happen?

no vision from the right eye

If the left optic tract is severed what would happen?

no info from right hemifield

What causes the blind spot?

optic nerve leaving the eye

How does the optic tract carry visual information to the thalamus?

it goes to the lateral geniculate nucleus (LGN) which is a clump of neurons in the thalamus that is segregated into distinct layer

What retinal ganglion cell do layers 1 and 2 connect to?

M-type ganglion cells, which give info about contrast (movement) to the magnocellular neurons

What retinal ganglion cells do layers 1 and 2 connect to?

P-type ganglion cells, which give info about color to parvocellular cells in layers 3-6

How do images from the left and right hemifields move from the optic nerve to the optic tract?

The eyes get both visual info, then it travels that way to the optic chiasm, from then on it is only info from the left hemifield that travels on the right and vice versa.