exam 2 Flashcards
what do tendons connect?
connect muscles to bone
what are skeletal muscles made up of?
striate muscle (overlapping layers of myosin and actin)
muscle fiber:
1) fast twitch fibers- contract quickly and fatigue easily
2) slow-twitch fibers- contract slowly and with less intensity, but fatigue more slowly
muscle synergistis vs antagonists
syn: work together to execute motion
ant: work in opposite to one another
where can motor neurons be found?
1) cell bodies in CNS
2) efferent axons in PNS
3) axon terminals on muscle fibers
neuromuscular junction
- synapse that motor neurons form on muscle fibers
- terminals of motor neurons release actetylcholine and binds to muscle receptors
what makes up a motor unit?
- motor neurons and all of the fibers it contacts
- 1 motor neuron: many muscle fibers
pyramidal motor system
- contacts motor neurons directly
- pathway involving cell bodies in M1 and axons that form syapses on motor neurons in spinal cord
M1
- primary motor cortex
- on precentral gyrus of frontal lobe
- has topography motor of map of the body
- motor planning for voluntary motion
- activity of neurons here associated with direction of a movement (certain neurons like certain sides. when a limb moves in the direction that particular neuron likes, it will fire more A.P. and the other side is inactivated)
complex movement requires ____ to contract multiple ____ to __
primary motor cortex
muscle synergists
different degrees
non-primary motor cortex
1) supplementary motor area- generates motor programs for preplanned movement
2) premotor cortex- generates motor programs in reaction to external events
Extrapyramidal Motor System
modulates pyramidal system and is involved in:
1.) initiation and cessation of motion
2.) precision of motor control
includes basal ganglia and cerebellum
how do basal ganglia and cerebellum influence motor cortices?
via parallel pathways through nuclei of
VA + VL complex of thalamus
basal ganglia
receives dopamine input from midbrain
has D1 and D2pathways for voluntary motions
D1like: “go”, dopamine increases
D2 like: “stop”, inhibited under domapine
increase in dopamine= increase in movement
cerebellum in extrapyramidal motor system
contributes to precision of motor control
what occurs in Parkinson’s
less D1 signals in basal ganglia
more D2 signals
cerebellar agenesis
cerebellum never forms
(walk and speech require precision control)
what is sensory transduction?
convert stimulus into stream of action potential
what do receptor cells do?
detect specific energies and chemicals in environment
if 2 species both posses a given sense, will they receive the same stimuli?
no, energy can be tuned differently
different types of receptor cells to distinguish inputs that are qualitavely and quantitvely different (different kind and amount)
ex: elephants and cats can hear sounds humans cant
receptive fields
where receptor cell detects stimulus
ex: frequency range in auditory system
sensory adaptation
- a progressive decrease in a receptor’s response to a sustained stimulus
- (if change doesn’t have a consequence, body will ignore it)
1) phasic receptors- display adaptation
2) tonic receptors- responds if stimulus is there (remind brain stimulus is still present, even if it’s not worth much attention)
sensory cortex
- each system has a primary sensory cortex that receives sensory info from thalamus
- sensory info detected by receptor cells
- perception occurs in the brain
somatosensory cortex
- processes touch info and has map of skin surface
- located in central gyrus on parietal lobe
- somatotopic map: receptive fields in neighboring areas of sin are processed by neighboring area in brain
non-primary/ association cortices
receive info from primary sensory cortex and integrate inputs from multiple senses
* can be polymodal neurons (respond to multiple different forms of sensory info)
primary somatosensory cortex
- where conscious perception of touch beings
- detects energy or chemical
- on post-central gyrus in parietal lobe
- has topographical map of skin surface
proprioception
perception of the position of the limbs and body in space (ex: detect stretch in tendons, contraction of muslces)
pacinian corpuscles
- receptor cell for sensing pressure and texture
- phasic
dorsal root ganglia (DRG) neurons
nerve endings in skin –(spinal cord)–> axon terminals in CNS
action potential activated by pressure in nerve endings on skin
dermatome
- strip of skin that collects info for the 31 spinal nerves
- organized from superior to inferior
papillae
- bumps on surface of the tongue with taste buds and other sensory receptors
- increase SA = increase # of sensory receptors
- filiform papillae: no taste buds; only somatosensory receptors
taste buds
- receptor cells for taste
- have microvilli: connect taste buds to surface of the tongue
- release ATP around env. and then nerve ending picks it up. Not as targetted
sour taste
- acidic (large H proton concentration)
- taste receptors have hydrogen channels
salt taste
NaCl dissolves into Na+ and Cl- in saliva
receptor cells have Na+ channels
T1R vs T2R receptors
T1R: for sweet taste
T2R: for bitter taste
umami taste
- bitter taste
- caused by glutamate
what is different about gustatory pathway from other sensory pathways?
ipsilateral- never crosses midline
olfactory receptor cells
- located in olfactory epithelium
- will do the action potential themselves. Not communicate with other cell that does
what is different about the olfactory sense from other senses?
pathway does not stop at thalamus
(info goes from olfactory bulb to cortex)
glomeruli
synapse where receptor and mitral cells connect
olfactory bulb
where olfactory info gets processed
what does the vomeronasal organ do?
detects pheromones (to communicate within species)
what is sound and its components?
pressure waves in the air detectable by the ear
amplitude= volume/ intensity
frequency = pitch
(high pitch = high frequency)
what does the outer ear do and what are its components?
collects sound and funnels it to the middle ear
1) pinna- fleshy exterioir to amplify sound (in some animals)
2) ear/ auditory canal- connects pinna to eardum
middle ear
- connects outer and inner ear
- has eardrum, ossicles, and oval window
what happens if eardrum is struck too loud?
oval window vibrates less, which increases adaptation to loud sound
2 main components of the inner ear
1) cochlea
2) semicircular canals
cochlea components
1) organ of corti: spiral-shaped, fluid-filled space that detect waves created by ossicles
2) basilar membrane: movies in response to waves on cochlea fluid
3) hair cells: receptors that transduce sound into electrical activity
ossicles
the 3 bones in middle ear
sound localization
- how your brain determines location of sound in space relative to you
- determined by comparing differences between how sound strikes your ears
A1
- primary auditory cortex
- has tonotopic map (represnts frequencies)
- organization of A1 reflects how basilar membrane responds to increasing frequencies
what is hearing loss?
damaged hair cells
tinnitus
ringing in the ears that can be permanent
what could happen if deprived of auditory input?
spiral ganglion cells may die
semicircular canals
- fluid-filled tubes oriented to 3 directions in which head can rotate (pitch, yaw, roll)
- respond to movements of the head
cupula
- found in ampulla
- hair cells here transduce head motion into electrical signal for CNS
- opens ion channels when deflected
what detects fluid acceleration by head rotation?
ampulla
what detects fluid movement by linear motion?
utricle and saccule
vestibular-ocular reflex
sensation of movement in one direction causes the eyes to move in opposite direction to stabilize visual images
(this is how it constantly monitors balance)
visible light definition and how it is determined
- electromagnetic waves between 400 and 700 nm
- brightness/luminosity- determined by wave amplitude
retina
- thin layer of tissue in back of eye that transduces light into neural signal
- optic disc = blind splot: no photoreceptors
- divided in half: nasal and temporal
cornea
fixed transparent tissue that refracts light
(focuses light)
lens
flexible to further refract light as needed to zoom in or out
(blurring of vision)
3 main components of retinal cells
1) photoreceptors
2) bipolar cells
3) Ganglion cells
photoreceptors
- sensory cells in back of retina that detect light
- transduction
- 2 types: rods and cones
what happens when photoreceptor cells are depolarized & hyperpolarized?
depolarized: release glutamate onto bipolar cells
hyperpolarized: releases less glutamate
release more glutamate in the dark or when there is less light
bipolar cells
- receive info from photoreceptors and pass it on to ganglion cells (form middle layer of retina)
- on-center: inhibited (hyperpolarized) by glutamate
- off-center: excited (depolarize) by glutamate
dont have action potential but (like photoreceptors) release glutamate when depolarized
what happens if there is a patch of darkness on retina?
photoreceptors release more glutamate on to ganglion cell –> inhibits on-center cells and excites off-center cells
ganglion cells
- the output of neurons (form inner layer of retina)
- their axons form optic nerve
- receive glutamate from bipolar cells
- the on/off-center arrangement provides constant input to brain about whether a given photoreceptor is in light or darkness
visual acuity
- ability to see detail
- highest at fovea (because retina is far thinner here-> less tissue for light to pass through before hitting the cones)
visual sensitivity
periphery more sensitive to low levels of light because more rods
tapetum lucidium
structure in many animals that reflects light back through retina, giving rods another chance to detect it
adaptation
- change in sensitvity to the brightness of intensity of light
- ex: changes in pupil size: can expand/contract allowing more/less light
range fractionation
- rods and cones are sensitive to different levels of light
- the minimum light necessary to stimulate cones is approximately the max amount that rods can detect
photoreceptor adaptations
rods and cones can adjust their level of sensitivity
3 types of cones and where they are the most sensitive to light
short (S): ~420 nm (blueish)
medium (M): ~530 nm (greenish)
long (L): ~560 nm (redish)
what determines what wavelength of light cones are sensitive to?
opsin molecules in the cones
-opsins in M and L cones are in X chromosome (defects here = red-green colorblindness
color blindness
inability to differentiate between light of different wavelengths
visual field
- the area visible to you without having to adjust your gaze
- both retinas receive input from left and right side of visual field
- light from right visual field strikes left half of both retinas (and vice versa)
optic chiasm
where axons from both nasal retinas cross midline
what is optic nerve made up of
axons of ganglion cells
suprachiasmatic nucleus
- circadian rhythm
- retinal input allows brain to sync the rhythm with light levels
V1
- primary visual cortex
- highly dense region of cortex in occipital lobe
- more space is given to center of visual field = allows more neurons to process high acuity info coming from fovea
- 2 types of cells: simple (detect edges of things) and complex
dont actually need to know difference between the 2 cells
hierarchial model of visual processing
combining inputs from the level before it to create increasingly complex representations
fragmented visual processing
distinct regions are specialized for specific aspects of vision
ex: blindsight
agnosia
acquired deficit in perception (destruction of V1)
blindsight
blindness but retain ability to do certian things like catch a ball
*visually guided behavior can happen without conscious experience
V2
- non-primary visual cortex
- streams of visual processing split off
1) Dorsal: V2–> V5 –> posterior parietal love (where)
2) Ventral: V2–> V4–> inferior temporal lobe (what)
V5
- visual motion
- neurons respond to stimuli moving in a particular direction
- damage here causes akinetopsia (motion blindness discontinuous freeze frame images)
posterior parietal lobe
- where vision gets integrated into control of motion
- damage here: hemineglect (patient unaware of 1/2 of their visual field)
V4
- integrates info from earlier stages of visual stimuli (ex: color and brightness)
- damage here: achromatopia (permanent color blindness)
inferior temporal lobe
recognition of specific stimulus
* parahippocampal place area (PPA)- responds more strongly to images of scenes and places
* fusiform face are (FFA)- facial recognition
* prosopagnosia- damage to FFA (cant recognize faces)
capgrass syndrome
- delusional belief that significant figures in your life have been replaced with imposters
- caused by injury to ventral stream or dementia
law of specific nerve energies
exact parts of NS determine how you perceive stimulus
perception is highly interpretive
visual stimuli don’t produce ____ patterns of activity in the optic nerve
consistent patterns
perception is inferencial
in
thalamus –> cortex –> thalamus
where is projection the strongest?
cortex —> thalamus
bottom-up and top-bottom processes
in visual perception
bottom-up: receptor –> cortex
top-down: cortex –> thalamus
Synesthesia
Condition where a stimulus in one sense modality also causes a sensation in another
what controls muscles in distinct parts of the body?
M1
where do earliest stages of perception occur?
primary sensory cortex
where do association cortices receive info from?
primary sensory cortex
how do areas of basilar membrane differ?
each region corresponds to specific frequency
why is visual activity highest in fovea?
1) thinner
2) more cones
what happens before retinal ganglion cells form synapses on neurons in LGN?
optic nerve turns into optic tract
