brainstem + somatosensory system

what does the brainstem connect

cerebrum - cerebellum - spinal cord

the brainstem contains what major components

cranial nerve nuclei + tracts + reticular formation

what is the reticular formation

complex network of nuclei throughout brainstem

what does the sulcus limitans separate

motor nuclei (medial) vs sensory nuclei (lateral)

are motor nuclei medial or lateral to sulcus limitans

medial to the sulcus limitans.

as the medial lemniscus ascends, does it move medial or lateral

moves more lateral

where is the spinothalamic tract located in the brainstem

lateral edge of reticular formation

CN III, IV, and VI function together to do what

control eye movements

CN III innervates which muscles

all eye muscles EXCEPT superior oblique and lateral rectus

CN IV innervates what muscle

superior oblique

which cranial nerve is crossed

CN IV

CN VI innervates what

lateral rectus

what muscle opens the eyelid and what nerve controls it

levator palpebrae - CN III

what muscle closes the eyelid and what nerve controls it

orbicularis oculi - CN VII

CN XI innervates which muscles

sternocleidomastoid + trapezius

damage to CN XI causes inability to

rotate head (opposite side) + shrug shoulder

know

brainstem blood supply comes from what system

vertebrobasilar system

paramedian arteries supply which region

medial brainstem

circumferential arteries supply which region

lateral brainstem

what is the main function of the thalamus

relay sensory and motor signals to cortex

thalamus is composed mostly of what

gray matter

what structure connects the two thalami

interthalamic adhesion

dorsal horn function

sensory input

ventral horn function

motor output

dorsal columns carry what?

ascending sensory info (touch, proprioception)

afferent fibers carry information in which direction?

periphery → CNS

What type of neurons are in DRGs

pseudounipolar

where do afferent axons begin and end

begin in periphery → end in CNS

somatosensory system includes which 3 subsystems

touch, proprioception, pain

what is sensory transduction

stimulus → electric signal

what type of potential is first generate for sensory transduction

receptor (generator) potential

When are action potentials generated?

When threshold is reached

AP firing rate is proportional to what?

Stimulus intensity

What do mechanosensitive channels respond to?

mechanical distortion

piezo channels detect what?

membrane tensionw

what is a receptive field

are where stimulus changes firing rate

small receptive fields → what?

high spatial accuracy

where is somatic acuity highest

fingertips

slowly adapting afferents detects what

static features (size, shape)

rapidly adapting afferents detect what

changes (movement, vibration)

merkel cells are what type of adaptation

slowly adapting

merkel cells detect what

shape, texture, edges

merkel cells have what type of receptive field

small (high resolution)

Meissner afferents are what type?

rapidly adapting mechanoreceptors

Meissner detects what

Low-frequency vibration + grip

Meissner receptive field size:

Larger than Merkel

pacinian afferents detect what

High-frequency vibration and pressure

pacinian receptors are located where

deep in dermis

pacinian adaptation

rapidly adapting

why do pacinian respond only to rapid stimuli

lamellar capsule filters slow pressure

ruffini afferents detect what

skin stretch

ruffini adaption

slowly adapting

ruffini function relates to

finger / limb position

which receptor is MOST important for reading BRAILLE

merkel cells

why not pacinian for braille

detect vibration, not detail

proprioceptors detect what

body position and movement

Main proprioceptors:

muscle spindles and Golgi tendon organs

Muscle spindles detect what?

Muscle length

Group Ia fibers detect what?

dynamic movement

group II fibers detect what

static position

Golgi Tendon Organs (GTO) detect what

muscle tension and force.

GTOS are arranged how

in series with muscle

Proprioception from lower body synapses where first?

clarke’s nucleus

Pathway: Clarke’s nucleus → ___

Dorsal spinocerebellar tract

Final pathway to cortex:

Medial lemniscus → VPL → cortex

Which nerve carries somatosensory info from face?

trigeminal nerve (CN V)

pain / temp from face goes to

spinal trigeminal nucleus

touch from face goes to

principal nucleus

principal nucleus

VPM → cortex

What is somatotopy?

body mapped onto cortex

which areas process touch

3b and 1

Area 3a processes:

Proprioception

Area 2 processes:

Touch + proprioception

What happens after cortical injury?

Functional remapping

Example of plasticity:

Adjacent regions take over