a+p 2nd midterm

special senses

vision smell taste hearing and equilibrium

somatic general senses

light touch, pressure, temperature, pain

mediated by sensory receptors all over body

vision

dominant sense

30-50% of cerebral area processes vision

eye accessory structures

eyebrows, eyelids, conjunctiva, lacrimal apparatus, extrinsic eye muscle, eyeball

conjunctiva

transparent membrane that produces lubricating mucous to prevent eye from dying

covers white part of eye

lacrimal apparatus

makes tears - made of lacrimal glands and small ducts that drain excess fluid into nasolacrimal duct

lacrimal fluids consists of

mucous, antibodies, and lysozyme

cleans moistens and protect eye

6 extrinsic eye muscles

movement of each eyeball innervated by abducens and trochlear cranial nerve

eyeball tunics

fibrous layer - cornea and sclera

vascular layer - choroid and ciliary body

retina - neural layer: rods and cones

sclera

opaque white part of eye

cornea

transparent and allows light to enter eye

anterior cavity filled with

aqueous humour that provides nutrients and oxygen to lens and cornea

posterior cavity filled with

vitreous humor that supports the lens and holds retina in place and maintains pressure within the eye

choroid

vascular middle layer that nourishes eye layers

ciliary body

controls the shape of lens to control amount of light entering eye

stretch large lens

relax lens thin

iris

controls pupil size and the amount of light that enters eyee

optic disc

blind spot as there is no photoreceptor cells

fovea centralis

highest density of cones producing most detailed vision

rods

good for night vision and is highly sensitive to light

found more in peripheral vision and more than cones

cones

high resolution colour vision

fovea centralis

only contains cones - highest visual acuity

trichromat

humans - red blue and green cones

glaucoma

drainage of aqueous humour blocked leading to increased pressure in the eye which compresses the retina and optic nerve - leads to blindness

cataracts

clouding of the lens which causes dim vision and faded colours

light path to the retina

cornea → aqueous humour → vitreous humour → retina → photoreceptors

distant vision

ciliary muscles relaxed

lens thin as possible

close vision

ciliary muscle contract

lens thick and buldge out

causes eye strain

myopia

near sightedness

eyeball too long or lens too thick

seeing close but trouble seeing far

hyperopia

far sightedness

eyeball too short or lens too thin

distant object clear close object blurred

astigmatism

uneven curvature of cornea/lens which produces blurred images

diverging concave lens

fixes myopia nearsightedness

decreases how fast light converges

converging concave lens

fixes hyperopia farsightedness

increases how fast light converges

colours are different

reflections of wavelengths off objects

how we perceive colour

object absorbs all wavelengths of light except for the wavelength of said colour we see - then our cone cells of said colour absorb it

blue cones

short wavelength

green cones

medium wavelength

red cones

long wavelengths

phototransduction

light energy producing graded receptor potentials

light activating neurons

rods and cones send signal to

colour info to bipolar neurons

bipolar sends signals to

colour info from R and C to ganglion cells

ganglion cell axons form

form optic nerve sends colour info to brain

brain processes colour and we perceive it

opsin proteins

determine what colours of light is absorbed by retinal pigment

changes in membrane potential from sensory neurotransmitters can produce

graded potentials

if graded potential depolarizes cell enough

it crosses AP threshold and produces an action potential along neuronal axon

depolarization

inside of membrane is less negatively charged

easier to produce an AP

hyperpolarization

inside of membrane more negatively charged

harder to produce an AP - farther from AP threshold

graded potentials

magnitude of stimulus corresponds to the magnitude of change in membrane potential

threshold

amount of depolarization required to activate voltage gated ion channels to allow Na in

all-or-none phenomena

action potentials happen completely when reaching threshold or not at all when not hitting it

photoreceptor cells in dark

are depolarized and release inhibitory neurotransmitter to bipolar cell

cannot stimulate ganglion cell

photoreceptor cells in light

are hyperpolarized and stops releasing inhibitory neurotransmitter to bipolar cell

allows for bipolar cell to depolarize and release neurotransmitter to ganglion and an AP to optic nerve

light adaptation

when we move from darkness to bright light

pupil constrict to reduce amount of light to retina

dark adaptation

bright area to dark one

pupils dilate to maximize light to retina

optic chiasma

Enables binocular vision and depth perception by ensuring that the left half of the brain processes the right visual field and vice-versa

lateral geniculate nucleus of thalamus

integrates visual info to emphasize cone vision and process depth perception

primary visual cortex

maps retinal info onto occipital lobe for further processing for colour shape and movement

visual processing ventral what stream

temporal lobe for memory and limbic system for emotions

have we seen this before and how does it make us feel

visual processing where/how stream

occipital and parietal lobes

recognize what we are looking at and how we can use it

chemoreceptors

receptors for taste and smell

responds to chemicals in a solution

olfactory epithelium

organ of smell located in roof of nasal cavity

olfactory cilia

long cilia covered in mucous - solvent for odorants

makes graded response to make an AP

in order to smell something

it must be in a volatile gaseous state

odorant must mix w/ mucous in nose for us to smell it

anosmia

temporary or permanent loss of sense of smell

caused by head injuries, local inflammation or neurological disorder

1 smell =

100s of odorant molecules

humans have 400 genes that encode

for specific receptors in nose

a receptor can bind one or more odorants

each odorant can bind to multiple receptors

same odorant molecule

can smell different depending on context and dose

olfactory transduction

odorant binds to receptor and activates G protein cascade that releases cAMP to depolarize cell and cause an AP

tufted bulb

detect if there is a smell

mitral cells

signals the brain to identify what smell it is

olfactory bulb has

2nd-order neutrons: mitral and tufted cells

mitral cells and tufted cells send signal down

the olfactory tracts straight to olfactory cortex without passing through thalamus

taste buds

sensory receptor organs for taste

located in papillae of tongue

gustatory epithelial cells

taste receptor cells that have gustatory hairs that project into taste pores

in order to taste

must dissolve in saliva and into taste pore then contact a receptor on a epithelial gustatory cell releases neurotransmitter and AP

5 basic tastes

sweet: sugars

sour: hydrogen ions

salty: inorganic salts

bitter: alkaloids quinone

umami: amino acid glutamate and aspartate

taste triggers

increased saliva secretion, increased gastric juice into stomach

cranial nerves for taste

facial nerve VII

vagus nerve X

glossopharyngeal nerve IX

5 food apetites

protein, carbs, fat, sodium, calcium

and thirst for water

satiety

feeling of fullness

taste is influenced by

smell and stimulation of thermoreceptors, mechanoreceptors, nociceptors,

vestibulocochlear nerve

vestibular branch: responsible for balance & equilibrium

cochlear branch: responsible for hearing

external ear consists of

auricle, external auditory canal

has ceruminous glands for earwax production

tympanic membrane

ear drum - transfers sound energy to auditory ossicles

separates outer and middle ear

pharyngotympanic tube

links middle ear to nasopharynx allowing air pressure to equalize

semicircular canals

evaluate position of head in response to rotational movements of head - dynamic moving

conducts: dynamic equilibrium

saccule and utricle

evaluate position of head in space respect to gravity

conducts: static equilibrium

bony labyrinth

filled with perilymph

membranous labyrinth

filled with endolymph

bony cochlea parts

scala vestibuli (next to oval window)

scala media (near cochlear duct)

scala tympani (ends at round window)

basilar membrane

floor of cochlear duct - important for sound reception

hair cells detect

vibrations between basilar membrane and tectorial membrane

frequency

number of waves that pass a given point in time Hz

pitch of sound

amplitude

height of a wave

reveals a sound’s volumedB

resonance

basilar membrane

high frequency sound waves at base short waves

low frequency at apex long waves

depolarized hair cell

sound waves bend hair cell stereocilium and cation channel open for neurotransmitters

hyperpolarized hair cell

hair cell stereocilium slack and cation channel closed

crista ampullaris of semicircular canals

detect angular or rotational acceleration

dynamic equilibrium

macula of saccule

detects up and down movements

macula of utricle

detects forward/backward movements

acceleration or deceleration causes

change in amount of neurotransmitter released in hair cells

changes in AP frequency