chapter 13: lower motor neurons

voluntary movement

is controlled from the top down

anterior frontal lobe

makes a decision. 1st in control of voluntary movement

motor planning area

acrtivited second for voluntary movement

cerebellum, basal ganglia

control circuits consist of these

control circuits

activated third; regulates activity in in motor tracts

tracts

in spinal cord; takes info to the muscles

motor tract neuron

delivers signals to spinal interneurons and motor neurons

lower motor neurons (LMN)

innervates skeletal muscles

lower motor neurons (LMN)

last, lowest neuron

upper motor neurons (UMN)

neurons of the CNS

upper motor neurons (UMN)

any neurons above lower motor neurons

sarcomere

functional unit of a muscle

titin

prevents sarcomere from being pulled apart

tropomyosin

uncovers actin site so myosin can attach

acetylcoline

triggers calcium stores to bind to troponin

troponin

induces movement of tropomyosin

hypocalcemia

pt.s with this will be slower and weaker

increased tone

will happen if there is too much calcium

muscle length

resistance to stretch depends on ths

shortened muscle

has less resistance to stretch

lengtened muscle

has more resistance to stretch

muscle tone

measured through PROM

muscle tone

resistance to stretch on a resting muscle

minimal

resistance to PROM in normal resting muscle tone

sarcomere

will disappear if in a shortened state for prolonged time

contracture

happens when sarcomeres disappear

dynamic bracing/ serial casting

helps redevelop sarcomeres after a contracture

cocontraction

simultaneous contraction of agonist and antagonist muscles

stabilization

cocontraction is important for this

stability

in upper limbs, this provides fine motor control

mobility

based on the ability to stabilize

lower motor neurons

consist of alpha and gamma types

alpha motor neurons

larger: extrafusal

gamma motor neurons

medium sized; intrafusal

intrafusal

inside muscle spindle

extrafusal

outside of muscle fiber

extrafusal

fast twitch fibers are

extrafusal

slow twitch fibers are

ventral horn spinal cord

where lower motor neurons have cell bodies

motor pools

different groupings of neurons within dorsal horn

anterior motor polls

innervate extensor muscles

posterior motor pools

innervate flexor muscles

myotome

group of muscles innervated by a single spinal nerve

C5

elbow flexion

C6

wrist extension

C7

elbow extension

C8

flexion of tip of middle finger

T1

finger abduction

L2

hip flexion

L3

knee extension

L4

ankle dorsiflexion

L5

great toes extension

S1

ankle plantarflexion

alpha motor neurons

large; high myelinated: fast speed;

alpha motor neurons

go to extrafusal fibers

gamma motor neurons

go to intrafusal muscle fibers

coordination

alpha and gamma motor neurons fire same time for this

reciprocal inhibition

inhibition of antagonist muscles during agonist contraction

interneurons

largest class of neurons; in spinal cord

interneurons

link that allows reciprocal inhibition

synergies

coordinated muscle actions

synergy

activity of muscles activated together in a normal nervous system

lesion

causes abnormal activation of synergies

fractionate

when body works out of synergistic movement

stroke

cannot fractionate movements; move in synergistic patterns

golgi tendon organs

allows us to know where body is in space

golgi tendon organs

sensitive to tension

spinal reflexes

can operate without brain input

yes

will a brain dead person withdraw if you prick their finger?

phasic reflex

quick; caused by golgi tendon organs

cerebral cortex

can inhibit reflexes if intact

muscle cramps

severe, painful muscle contractions lasting seconds to minutes

muscle cramps

caused by sensory input OR electrolyte imbalance

fasciculations

quick twitches of all muscle fibers in single motor unity

fasciculations

visible on the surface of the skin

fasciculations

example: eyelid twitching when anxious

fasciculations

often accompanies anxiety

myoclonus

brief, involuntary contraction of a muscle

myoclonus

example: the hiccups and feeling like you’re falling in your sleep

hiccups

myoclonus of the diaphragm

fibrilations

random spontanrous brief contractions of single muscles not visable on the skin

fibrilations

pathological: caused by lesion or disorder

tremors

involuntary rhythmic movements of a body part

tremors

triggered by anxiety, caffeine or withdrawl

resting tremor

most visible when a person is not moving

pill rolling tremor

a type of resting tremo

resting tremor

will go away when actively using body part

intention tremor

happens when voluntarily moving

intention tremor

ex: tremors happen when you try to write your name

postural tremor

occurs when body part maintained against gravity

parkinson’s disease

will have resting tremor affecting hands and lower limbs

cerebellar tremor

are intention tremors

psycogenic tremor

sudden onset and remission

psycogenic tremor

sign of lower motor neuron lesion

upper motor neuron issue

happens in brain or spinal cord

spactisity

caused by upper motor neuron lesions

neurogenic atrophy

muscle atrophy caused by impairment of nervous system: CANNOT contract

hypotonia, flaccidity

abnormal muscle tone types caused by LMN lesions

hypotonia

decreased tone