20-21 Motor

Who is Paulina Seminova

ballerina

Who is Josh Blue

comedian, cerebral palsy

simple reflexes with brief muscle activation (eyeblink, hiccup, finger twitch)

movements

complex, sequential movements (a bunch of movvements strung together)

(honking car horn, writing name, playing lead guitar)

Acts/action patterns

set of muscle commands establish before the action occurs (brain plans how to carry out acts

motor plan/motor program

most of the brain’s activity is ultimately ___

motoric - preparing to move, moving, correcting ongoing movement

What is the only reason we need a brain at all?

to move - the rest is just fluff

what is the whole point of the brain?

guide movement

Two control mechanisms optimize ____ and _____

accuracy

speed

Which control mechanism maximizes speed?

open-loop control

Does open-loop control have any guiding external feedback?

no

What are the characteristics of open-loop ballistic movement?

• rapid (like a boxer)

• completed regardless of sensory feedback (like a cough)

Which control mechanism favors accuracy?

Closed loop control

Does close-loop control have any guiding external feedback?

yes - external feeback influences how movement occurs

What are the characteristics of closed-loop ramp movement?

• slow, smoother movments

• movments are sustained and guided by sensory feedback

____ power movement

skeletal muscles

_____ controls skeletal muscles

spinal cord

______ integrates motor commands

brainstem

initiates commands for action

primary motor cortex

initiates cortical processing

nonprimary motor cortex

____ and _____ tweak motor control systems

cerebellum

basal ganglia

heirarchy of our motor systems diagram

at rest, flexor and extensor muscles are ____

balanced

alternation of flexor-extensor (antagonist) contraction

tremor

What can happen if tremors are poorly regulated?

they can become debilitating

Biceps and triceps are ______

agonists

muscles that contract when another muscle extends

antagonists

muscles that act together (ex: flexing hip joint)

synergist

true or false: tremors are always abnormal

false - everyone has tremors, but can become debilitating if poorly regulated

action potentials travel along the _____ from _______ to ______.

moterneuron

spinal cord

muscle

What do motor neurons do

send their axons to innervate muscles

what is a neuromuscular junction

motor neuron terminal and muscle fiber meet

what is released at the neuromuscular junction

Acetylcholine (ACh) (muscle neurotransmitter)

What is a motor unit

one motorneuron’s axon and all its target fibers

Muscles that make fine precise movements have [many/a few] muscle fibers per axon

a few

what is an innervation ratio

The number of fibers innervated by a motor unit

Muscles involved in fine, presice movements have a [large/small] innervation ratio

small

what are the action of muscles guided by

sensory feedback

collection of information about body movements and position

proprioception

how does tiger know when to start his downswing

proprioception

what are the two kinds of muscle proprioceptive receptors, and what are they responsive to

muscle spindles - responsive to muscle stretch

golgi tendon organs - respond to muscle contraction, less to stretch

what is the muscle contraction pathway

muscle stretched → muscle spindle stretched → afferent impulses sent to spinal cord to stretch → muscles contract

what does stimulation of the golgi tendon do, and why

inhibits motor neurons - prevents tension and extreme muscle contraction

muscle spindle diagram

What is the stretch reflex circuit

1. muscle is stretched

2. muscle afferents are excited

3. motor neurons are excited

4. agonist muscle stimulated to oppose the stretch

5. antagonist muscle is inhibited

How do you win every arm wrestle?

Touch the back of the hand - resets the muscle spindles for a few milliseconds

stretch reflex is flawed or impaired

Spasticity

what does the motor cortex do to reflex behavior, and why?

inhibits reflext behavior, so they don’t interfere with voluntary movements

what happens if the normal motor cortex input is cut off?

spinal cord is released from inhibition (becomes hyperreflexic), and normal reflexes are exaggerated.

pull feet back, they spasm uncontrollably for a few seconds

clonus

hit the knee and the leg goes way up

hyperreflexia

pyramidal vs extrapyramidal motor systems diagram

what is another name for the pyramidal system pathway

a two-neuron chain

What is the pathway of Neuron 1, the Upper MN?

primary motor cortex → medullary pyramid (crosses over) → down spinal cord → anterior horn cell (lower motor neuron)

What is the scope of Neuron 2, the Lower MN?

spinal cord/motor neurons → muscle

upper and lower motorneuron pathway diagram

What are the two neurons of the pyramidal system pathway

upper MN, lower MN

How does the primary motor cortex change

change via learning

How does early music training affect the cortex

results in expansion of motor cortex

The primary motor cortex controls movement— what does the nonprimary motor cortex do?

learns and plans movement

Function of the supplementary motor area (SMA)

encodes movement during acquisition

Function of the premotor cortex

neurons fire just before an activity

Where are mirror neurons located, and what do they do?

located in premotor cortex (neurons fire here before performing activity), and they fire when observing someone doing the same task as you

motor cortex diagram

What system are the basal ganglia and cerebellum a part of?

Extrapyramidal system

What does the cerebellum do?

guides movement via inhibition

Where are Purkinje cells located, and what is their function

located in the cerebellum

function - inhibition

____ and ____ modulate movement

cerebellum

basal ganglia

____ and ____ are more involved in early phase of a movement than ____ and ____

primary motor cortex

basal ganglia

supplementary motor area

cerebellum

Which areas are more involved in the early phases of a movement

Primary motor cortex, basal ganglia

Which areas are more involved in the later phases of a movement

Supplementary motor area, cerebellum

Voluntary movements need

adjustment of posture

What does the extrapyramidal system do to prevent loss of balance

predicts postural consequences of planned (pyramidal) movement, and acts to prevent loss of balance

planned movement: [pyramidal/nonpyramidal]

pyramidal

compensatory movement [pyramidal/nonpyramidal]

non-pyramidal

Bell sounds to initiate the lift, gastrocnemius is activated [before/after] biceps

before

what are rhythmic behaviors generated by

neural circuits

Rhythmic activities such as walking are generated in ___

spinal cord

What is the pathway to push a button

retina → LGN → V1 → V2 → V4 → inferior temporal lobe → prefrontal cortex → premotor cortex → primary motor cortex → spinal cord → finger muscle

movement control cascade

What is the current state of the body?

Should I move?

Select, load, and execute plan

Feedback on how the plan is going. Change it?

movement control cascade matching:

1. What is the current state of the body?

2. Should I move?

3. Select the motor plan

4. Load the motor plan

5. Execute the plan

6. Feedback on how the plan is going. Change it?

ataxia

poor muscle control

strength is a ____ function

pyramidal, power

tone is an ____ function

extrapyramidal, posture

True or false: pyramidal and extrapyramidal functions (strength/tone) are independent

false

What does pyramidal damage cause

weakness

What does extrapyramidal damage cause

impaired motor control

What are pyramidal functions

strength

planning of movement

what are extrapyramidal functions

posture

predicts consequences of planned movemets and acts in response to maintain balance

myopathy

a primary disorder of the muscle

(a disorder of the muscle itself, rather than the nerves)

a primary disorder of the muscle

myopathy

muscular dystrophy

progressive degeneration of muscle

what is muscular dystrophy caused by

patients make insufficient/no/deformed dystrophin

what is dystrophin, and how is it produced?

protein needed for normal muscle function - produced by x chromosome

what is wrong with josh

muscular dystrophy

myasthenia gravis - cause and symptoms

autoimmune disorder - patients develop antibodies to their own ACh receptors

symptoms: weakness of skeletal muscles that develops over the day, but resolves with rest/sleep

how is myasthenia gravis disagnosed

tension (ACh agonist) test

What is this disease

myasthenia gravis

polio

poliovirus destroys spinal motorneurons and sometimes cranial motorneurons

causes irreversible paralysis

Amyotrophic lateral sclerosis

aka Lou Gehrig disease

degeneration of motorneurons and consequent loss of their target muscles