Hard terms

spinal cord external anatomy

sensory information carried by afferent axons of spinal nerves enter via dorsal roots

motor commands carried by efferent axons leave spinal cord via ventral roots

spinal cord internal anatomy

interior cord formed by gray matter and surrounded by white matter

white matter divided into dorsal, lateral, and ventral

dorsal columns

carry ascending sensory information from somatic mechanoreceptors

lateral columns

include axons that travel from cerebral cortex to interneurons and motor neurons in ventral horns

ventral columns

carry ascending information about pain & temperature and descending motor information form brainstem & motor cortex

dorsal horn

neurons receive sensory information that enters via dorsal roots of spinal nerves

ventral horn

contain cell bodies of motor neurons that send axons via ventral roots of spinal nerves to striated muscles

lateral fissure

separates temporal lobe from frontal & parietal lobes

central sulcus

separates frontal and parietal lobes

pre central gyrus

locates motor cortex

postcentral gyrus

locates somatic sensory cortex

calcimine sulcus

locates primary visual cortex

internal capsule

major pathway linking cerebral cortex to Brian & spinal cord

lymphatic system

CSF passes from arterial perivascular space

waste-carrying CSF passes out of brain via perivascular space

pseudounipolar

no synapse before entering spinal cord

neurons of dorsal root ganglia

receptive field

branching: smaller arborization→ smaller receptive field

density: more afferents→ smaller receptive field

rapidly adapting afferents

fire upon initiation of stimulation

become quiescent if stimulation maintained

important for conveying info about changes in ongoing stimulation

slow adapting afferents

continue to fire with sustained stimulation

may convey information about spatial attributes of stimulus

Merkel cell-neurite complex

slow adapting

highest spatial resolution

express piezo 2

sensitive to edges, points, & curvature

messier corpuscle

rapidly adapting

high spatial resolution

removal of stimulus releaxes to resting position

detect slippage between skin and object in hand

Ruffini endings

large receptive fields

detect vibrations transmitted through objects in touch with hand

pacinian corpuscle

rapidly adapting

deep in dermis

filters out all but high frequencies

muscle spindles

innervated by primary and secondary

sensory afferents:

when stretched, tension of intrafusal fibers activate mechanically gated ion channels

primary endings

group 1a ffernts

rapidly adapting responses to changes in muscle length

transmit info about limb dynamics

secondary endings

group II afferents

sustained responses to constant muscle length

info about static limb position

gamma motor neuron

change intrafusal fiber tension and increase sensitivity of afferents to change in muscle length

Golgi tendon organs

low threshold

sense change in muscle tension

innervated by group 1b afferents

spinocerebellar tract

first order neuron collaterals form lower body synapse in Clarke’s nucleus

neurons in Clarke’s nucleus send axons via dorsal spinocerebellar tract to cerebellum

neurons in 2

respond to tactile and proprioceptive stimuli

neurons in 3a

respond to proprioceptive stimulation

neurons 3b & 1

respond to cutaneous stimulation

3b

receives largest input form VP thalamus

dorsal column medial lemniscal pathway

carries mechanosensory info from body

trigeminal portion of mechanosensory system

carries info from face

3b lesions

deficits in forms tactile sensations mediated by cutaneous mechanoreceptors

lesions 1 or 2

deficits to discriminate texture of objects or size and shaped of objects

external ear

pinna: filter sound frequencies

concha: cues about elevation of sound source

auditory meatus: boost sound pressure

middle ear

large tympanic membrane to small diameter oval window

level action of ossicles

bell’s palsy

flaccid paralysis lead to hyperacusis

painful sensitivity moderate to even low intensity sound

tontopy

decompose acoustical waveforms into elements

transduction auditory

tip links move and translate hair bundle movement into receptor. potential

movement towards tallest stereo cilia open channels

K+ enter cell

depolarization

Ca channels open

NT release on audiotry nerve

divisons auditory nerve

anteroventral

posteroventral

dorsal

ITD

difference time takes sounds reach ear based location

computed by binaural inputs to medial superior olive from bilateral anterovetnral cochlear nuclei

IID

use lateral superior olive and medial nucleus of trapezoid body

compute sound source position

LSO receive direct excitatory input form ipsilateral cochlear ncuelus

contralterla inputs arrive via inhibitory interneurons in MNTB

LSO inhibited by MNTB interneruon

LSO fire most strongly in response o sounds arising directly lateral to listen, ipsilateral to lSO

Monaural pathway

cochlear nucleus bypass superior olive and terminate in lateral lemnisucs on contralateral side of brainstem

MGC

medial geniculate complex of thalamus

all ascending information must pass throough

Dorsal MGC to belt and parable regions

ventral MGC to primary auditory cortex

auditory pathway

project to inferior colliculus

utricle

oriented horizontal translation movement of sideway head tilts

saccule

oriented vertically

repsond translational movement up/down

semicircular canal

respond rotation of head

vestibulocular

coordinate head and eye movement to keep gaze fixed on objects of interest during movement

excitatory input from horizontal canal on one side produces eye movement on other side

vestibulocervical reflex

axons from medial vestibular nucleus go in medial longitudinal fascicules to reach upper cervical levels of spinal cord

regulate head position by reflex of neck when semicircular canal activated

vestublospinal reflex

inputs from otolith organs to lateral vestibular nucelus to lateral vestibulospinal tract to ipsilateral ventral horn of spinal cord taht activate extensor/inhibit flexor motor neurons

flocculus and paraflocculus

purkinje cells transmit inhibitory signals to vestibular nucleus and cells change its firing properties

nodulus and uvula

integrates signals from semicircular canals and otolith organs to distinguish between head tilts or translational movements

rostral fastigial nucleus

neurons do not respond to self generated movement

predictive signals cancel proprioceptive and vestibular signal form self generated movement

active vs passive

parietoinsular vestibular cortex

PICV stimulation: strong vestibular sensations

lesions: altered perception of personal and extra personal space

vestibular to cortex

superior and lateral vestibular nuclei→ ventral posterior nuclear complex of thalamus

cortical areas: brodmann’s area 2v, 2 regions of 3a, PICV

retinoid cycle

all trans retinal to outer segment

all trans retinal to all trans retinol

all trans retinol to retinal pigment epithelium by IRBP

all trans retinol to 11-cis retinal

stopping phototarnsduciton

activated rhodopsin phosphorylated by rhodopsin kinase allows arresting to bind to rhodopsin and stop from activating transducin

phototransduction cascade

retinal absorb photon and convert to 11-cis to all-trans configuration

activated transducin activates PDE that hydrolyses cGMP

cGMP dark and light

in dark: Na+ and Ca2+ flow into outer segment and K+ flow out (depolarize)

in light: cGMP decrease and membrane hyperpolarize

optokinetic reflex

require direction selective ganglion cell

project ot nucleus of optic tract which leads to activation of cranial nerves controlling eye muscles

direction selective ganglion cell

receive inhibitory input from starburst amacrine cells

starburst amacrine cells

* light stimuli = preferred direction and ganglion cell excited before stimuli reach SAC
* light stimuli= null direction and SAC activated before ganglion cell receives excitatory input from bipolar cells and amacrine cells block excitation signaled to ganglion cell from bipolar

OFF bipolar cell

ionotorpic glutamate recepotr

dark: release glutamate and active

ON bipolar cell

metabotropic glutamate recepotr

close when glutamate bound and hyperpolarize in dark and active in light

inner plexiform layer

bipolar cell axon

off: stratify in upper

on: stratify in deeper layers

inner nuclear layer

bipolar cell bodies

horizontal cell

hyper polarizing effect

release less glutamate, horizontal cells hyperpolarize and cause photoreceptors to slightly depolarize

pyramidal cell project

project to other cortical areas (superficially)

deeper cortical: project to subcortical targets including LGN and superior colliculus

magnocellular layers

receive input form ganglion cells with larger receptive and more transient and motion sensitive responses

project to layer 4Calpha in V1

paravocellular layers

receive input form small receptive field retinal ganglion cells and have more sustained responses and can signal color information

project to layer 4Cbeta in V1

koniocellular layers

between paravocellular and magnocellular

project to layers 2/3 of V1

visual reflex

tons to pretectum that project to dinger-westphal nucleus and send axons via oculomotor nerve to cilia ganglion

cause pupil to decrease

red nucleus

projections limited to cervical level of cord

control arm/hand movements

reticular formation

mediates feedforward adjustments to stabilize posture during movement

compensatory movements to counter predicted destabilization of primary movement

upper motor system

brainstem and cerebral cortex

synapse mainly with local circuit neurnos

initiation of complex voluntary movements

primary motor cortex and premotor cortex essential for proper sequential movement

alpha motor neurons

large motor neurons that innervate striated muscle fibers

gamma motor units

small diameter

innervate specialized muscle fibers

embedded within connective tissue

send sensory information to spinal cord and brainstem about length of muscle

slow motor

resistant to fatigue

intermediate

fast and fagtigue resistant

fast

fast and fatigable

direct pathway

release upper motoneurons from tonic inhibitor

facilities movement

indirect pathway

increase tonic level of inhibition

inhibits movement

projections

striatum: input

pallidum: output

superior cerebellar peduncle

almost entirely efferent pathway that projects from deep cerebellar nuclei to premotor and primary motor cortices

superior colliculus to control orienting movements

middle cerebellar peduncle

afferent pathway to cerebellum

cell bodies located in contralateral pontine nuclei

inferior cerebellar nuclei

multiple afferetns & efferent pathway

afferents from vestibular nuclei, spinal cord, and tegmentum

efferents to vestibular nuclei & ersticular formation

cerebrocerebellum

deficits coordination and visuomotor integration

vestibulocerebellum

impairs ability to stand upright and maintain direction of gaze

spinocerebellum

difficulty walking

mossy fiber

arise from many areas in cortex & brainstem

synapse onto granule cells

climbing fiber

1 per purkinje cells

directly contact these cells