pbsi 235 exam 2

3 different categories of muscles

skeletal muscles, muscle synergists, and muscle antagonists

skeletal muscles

used to produce bodily motion by contracting and pulling on the sekelton. tendons connect the muscles to the bones

muscle synergists

work together in order to execute motion

muscle antagonists

work in opposition to one another. when one contracts the other stretches

striate muscle

overlapping layers of myosin and actin, which make up the myofilaments that control muscle contraction, give these muscles a striped appearance

muscle fibers

result of multiple cells fusing during development, and have multiple nuclei

2 types of muscle fibers

fast twitch fibers and slow twitch fibers

fast twitch fibers

contract quickly and fatigue easily

slow twitch fibers

contract slowly and with less intensity, but fatigue more slowly

motor neurons

have cell bodies in the CNS, axons that form the efferent portion of the peripheral nerves, and axon terminals that synapse on muscle fibers

neuromuscular junction

synapse that motor neurons form on muscle fibers. the terminals of motor neurons release acetylcholine onto the post synaptic membranem

motor unit

a motor neurons and all of the muscle fibers it contacts. one motor neuron contacts multiple muscle fibers

pyramidal motor system

pathway involving cell bodies in primary motor cortex with axons that for synapses on motor neurons in spinal cord

primary motor cortex

also called m1, located on the precentral gyrus of the frontal lobe. contains a motor map of the body arranged topographically

axons in primary motor cortex

heads off in an inferior direction, crossing the midline at the medulla, thus cell bodies in the primary motor cortex synapse on motor neurons on the contralateral side of the body

non primary motor cortex

includes supplementary motor area and premotor cortex. both are anterior to the primary motor cortex in the frontal lobe

neurons in primary motor cortex

when a given neuron fires more AP’s, the limb will move in a particular direction. opposite direction, neuron will fire fewer AP’s

motor planning

these regions prepare specific sequences of voluntary motion that are executed by the primary motor cortex

supplemental motor area

generates motor programs for pre planned movement

premotor cortex

generate motor programs in reaction to external events

extrapyramidal motor system

regulates the pyramidal motor system, in part via specific thalamic nuclei that project to primary and non primary motor cortex

basal ganglia

area of forebrain that receives heavy dopamine input from the midbrain. has “go” and “stop” pathways that when activated, initiate or halt behavior

cerebellum

hindbrain region with more neurons than the cortex, semi mysterious in function but known to contribute to precision motor control

parallel pathways within motor cortices through the nuclei

ventral anterior and ventral lateral nuclei (VA/VL complex) of the thalamus

nigrostriatal pathway

cell bodies in the substantia nigra (midbrain) send axons to the dorsal striatum (in the basal ganglia)

D1-like neurons

“Go”

D2-Like neurons

“Stop”

parkinsons disease

death of neurons that comprimise the nigrostriatal pathway, strongly reduces basal ganglia dopamine

akinesia

inability to initiate voluntary motion, sometimes may occur because of an imbalance between D1 and D2 like neurons

bradykinesia

abnormallly slow motion, sometimes may occur because of an imbalance between D1 and D2 like neurons

paradoxical kinesia

sudden ability to execute smooth normal motion by a parkinsons patient

cerebellar agenesis

very rare condition in which the cerebellum never forms, woman who had this could not speak intelligible way until she was 6

sensory processing systems

works with nervous system, detects and analyzes environmental stimuli, detects specific forms of energy, particular chemicals

receptor cells

inside sensory organs of animals, specialized for the detection of specific energies and chemicals in their environment

idiopathic

we dont know why it happens

sensory transduction

receptor cell converts this sensory input into an electrical signal that can be processed and interpreted by the nervous system

classifications of sensory systems

touch, hearing, electroreception, and magnetoreception

qualitative differences 

having different receptors in your skin for pressure and vibration as well as different receptors in your eye for different colors

quantitative differences

having different receptors in your eye that are sensitive to different light levels

receptive field

area within which a receptor cell can ditect a stimulus

sensory adaptation

progressive decrease in a receptors response to a sustained stimulus

sensory cortex

regions that receive sensory info from the thalamus; follows distinct path

topographic map

highly organized part of sensory cortex, takes in information from the environment

somatosensory cortex

processes touch information and has a map of the skin surface. for a given region of the body, receptive fields in neighboring areas of skin are processed by neighboring areas of the brain (somatotopic)

auditory cortex

processes sound information, arranged so that similar sound frequencies are processed by the neighboring area (tonotopic map)

non primary/association cortices

receives information from primary sensory cortex and integrates inputs from multiple senses; plays a role in creating an integrated sensory world and in storing remembered information

polymodal neurons

responds to multiple different forms of sensory information

synesthesia

a condition in which a stimulus in one sense modality also causes a sensation in another (hearing colors in songs)

plasticity

change as a result of experience. extensive or highly skilled use of a body part can expand its representation in the somatosensory cortex (playing the violin)

what senses are missing from the 5 traditional senses?

balance (vestibular sense), some forms of perception

primary somatosensory cortex

located on the post central gyrus (hills) in the parietal lobe. has a topohraphical map of the skin. 

proprioception

perception of the position of the limbs and body in space; uses specialized receptors that detect stretch in tendons, contraction of muscles and joint angle

pacinian corpuscles

receptor specialized for sensing pressure and texture. they are phasic receptors - they adapt quickly to a constant stimulus

mechanically gated sodium channels

open when pressure causes the membrane to stretch.

generator potential

similar to an excitatory postsynaptic potential caused by a specific sensory input (instead of a neurotransmitter release)

dorsal root ganglia (DRG) neurons

cluster of neurons located near the spinal cord; somatosensory receptors like the pacinian corpuscle surround the nerve endings of neurons with cell bodies in the DRG

dermatome

each of the 31 pairs of spinal nerves is associated with a strip of skin that it collects information from; roughly organized from superior to inferior so that heigh regions of the spinal cord are collecting info from the higher up in the body

drg neurons travel

axons of DRG neurons travel up the spinal cord to the medulla. from there, DRG neurons form synapses on the medulla neurons. medulla neurons send axons across the midline forming synapses on neurons in the contralateral VPN of the thalamus. as a result, stimuli on the left side of the body are processed on the right side of the brain and vice versa

ventral posterior nucleus (VPN)

send axons to the primary somatosensory cortex

amplitude 

what determines the volume, loudness, or intensity of a sound (height of wave)

frequency

what determines the pitch of a sound, measured in hertz (hz) (length of wave)

sound

pressure waves in the air that are detectable by the ear

pinna

(outer) the fleshy exterior part of the ear

ear canal/auditory canal

(outer) passage connecting the pinna to ear drum

tympanic membrane

(middle) otherwise known as the ear drum, when sound strikes it is translated into vibrations that pass through the three bones of the middle ear, called ossicles

ossicles

(middle) 3 bones of the middle ear, connects the tympanic membrane to the oval window

oval window

(middle) the membrane through which sound enters the inner ear

cochlea

(inner) shaped like a snail shell, contains a spiral shaped, fluid filled space. vibrations from the ossicles enter the cochlea via the oval window, where they become pressure waves in the fluid that fills the cochlea

organ of corti

a spiral shaped, multi layered strip of tissue in the cochlea that detects the waves created by the ossicles; contains the basilar membrane

basilar membrane

ripples and flexes in response to waves traveling through the fluid of the cochlea. each region of the basilar membrane responds to a specific sound frequency, arranged along its length from highest to lowest. the area of the basilar membrane near the base (closest to the oval window) of the cochlea responds to the highest frequencies, and the area nearest to the apex responds to the lowest

hair cells

receptors that transduce sound into electrical activity; they have stereocilia, hair like structures embedded in the tectorial membrane

tectorial membrane

runs parallel to the basilar membrane and does not flex in response to sound

stereocilia

hair like structures, enables the sensation of hearing and balance

spiral ganglion

neurons that make up the cochlear part of the vestibulocohlear nerve (one of the 12 cranial nerves); cluster of cell bodies that follows the spiral shape of the cochlea

cochlear nucleus

part of the auditory pathways, its axons cross the midline and synapse on the neurons of the superior olivary nucleus in the pons

sound localization

the source of a sound is determined by comparing differences between how it strikes your ears. slight differences in volume at each ear, as well as slight differences in when the sound is first detected by each ear, are compared and used to localize the origin of the sound. 

medial geniculate nucleus

part of the auditory thalamus, relays inputs for auditory information, transmitting it from the brainstem to the auditory cortex

primary auditory cortex

located in the temporal lobe, contains a topographic map of sensory inputs; organized to reflect the way the basilar membrane responds to increasing frequencies along its length

tinnitus

ringing in the ears that can be permanent

hearing loss

if a noise is loud enough, it can damage the hair cells. if deprived of input, spiral ganglion cells may die

semicircular canals

fluid filled tubes oriented to the three directions in which the head can rotate: pitch (head up and down), yaw (shaking head back and forth), and roll (moving your head side to side)

head rotation

accelerates fluid in the semicircular canals, which is detected by specialized receptors within the ampulla at the base of the canal

ampulla

bulbous expansion that detects rotational head movements. contains cupula.

vupula

the stereocilia of vestibular hair cells are embedded in the cupula. when the cupula defects, the stereocilia are displaced, opened mechanically gated ion channels

vestibular ocular reflex

sensation of movement in one direction causes the eye to move in the opposite direction to stabilize visual images

vestibular ganglion

neurons form synapses on nuclei in the pons, medulla, and cerebellum on the ipsilateral side of the brain

flavor

combination of inputs from multiple different senses; taste, smell, somatosensory

taste

gustatory, chemicals in food

smell

olfactory, air born chemicals (food tastes worse when your nose is stuffed)

somatosensory (in taste)

texture (mouthfeel), pain (spiciness), temperature

papillae

bumps on the surface of the tongue in which taste buds and other sensory receptors are embedded

5 basic tastes

salty, sour, sweet, bitter, or umami/savory

taste buds

a collection of 50-100 taste receptor cells that all respond to one of the 5 basic tastes

microvilli

hair like extensions covered with taste receptor proteinst

taste pore

an opening that connects the taste bud to the surface of the tongue

salt

NaCL, dissolves into Na+ and Cl- in the saliva; contributes to a generator potential, causes ATP release

sour

acidic, determined by the concentration of hydrogen, causes ATP release

sweet

sucrose and fructose, T!R receptors bind to sugars and other sweet tasting chemicals., causes ATP release

dimer

formed when T1R binds to sugars, is a compound molecule made of two similar or identical subunits

umami & bitter

caused by glutamate and other amino acids. binds to T2R, causes ATP release