Motor Cog lecture 3

What is a muscle spindle?

Dendrites of sensory neurons that detect change in muscle length

What do 1A afferent neurons do?

Tell spinal cord to send contraction

What is a motor unit?

Group of muscle fibers innervated by alpha motor neuron

Where is the cell body of a motor unit?

In the spine

What is a neuromuscular junction?

Where an alpha motor neuron synapses with muscle fibers

What is the golgi tendon organ?

Dendrites of sensory neurons that sense muscle tension

What does the golgi tendon organ do?

Inhibits contraction preventing muscle tear from the bone

What is innervation ratio?

The amount of neurons per motor unit

What are the perks of a low innervation ratio?

Increased control and decreased force

What would an example of a low innervation ratio?

Intrinsic hand, face muscles

What are the perks of a high innervation ratio?

Decreased control and increased force

What would an example of a high innervation ration?

Tricep, gastroc

What is the motor unit recruitment/size principle?

A group of muscle fibers innervated by one motor neuron that are recruited from lowest innervation to highest innervation

What does motor unit recruitment allow for?

It scales force production so you can output as much or as little force as you would like

What is rate coding?

Firing rate of individual motor units

What is rapid summation?

The interval between motor units firing decreases in time allowing for the impulses to summate raster and increase force output

What are the two anatomic limb properties that contribute to force production?

Resting length and slower movement

How does slow movement help force production?

It increases power produced

What are the three mechanical properties that contribute to force production?

Degrees of freedom, segmental linkages, and spring like muscles

How do segmental linkages increase force production?

The segments connect at joints and allow energy to flow from proximal to distal

What is an example of segmental linkages?

A baseball player using their arm and legs to fully extend and move energy into the ball on release

What are two short loop reflexes?

Spindle and interneurons

What does a spindle reflex do?

Muscle length changes and sends a signal to the spinal cord through 1a afferent neruons

Does the spindle reflex have its own alpha motor neuron it synapses with?

yes

What do interneurons do?

Excite or inhibit neurons of the CNS

What occurs during reciprocal inhibition?

Spindle is stretched sending 1a afferent to spinal cord, it sends an excitatory signal to an agonist and an inhibitory signal to an antagonist

What are long loop reflexes?

Multiple levels of the nervous system are involved

What is an example of a long loop reflex?

Someone getting tickled in the stomach but flexing at the hip and knee

What are the two main spinal pathways?

Spinothalamic and dorsal columns

How does sensory information get to the parietal lobe?

Spinal pathways

Where does the spinothalamic pathway relay to?

thalamus

Where does information have to synapse before the rest of the brain is made aware of a sensation?

Thalamus

What information is relayed by the spinothalamic pathway?

Pain and temperature

What kind of information do the dorsal columns relay?

Light touch and proprioception

If one part of the spinal cord is bruised can you still have some sensation?

Yes

What relays motor information from the brain to the muscles?

Corticospinal tract

What part of the brain sends motor neurons and decides what movements to make?

Frontal

Does the corticospinal tract innervate one specific muscles or a large group of muscles?

A specific muscle

What are the two steps of motor information?

Frontal lobe to spinal cord

Spinal cord to muscles

What allows for fast conduction in the corticospinal tract?

Large diameter axons with limited synapses

How does the corticospinal tract help with precise movement in the extremities?

Timing of muscles activation patterns

What is a synergy?

A group of muscles that act as one unit

What is an upper extremity example of a synergy?

Bringing your hand to your mouth to eat food

What is an lower extremity example of a synergy?

Kicking a ball

What is a central pattern generator?

A neural circuit with little influence from brain

How is a central pattern generated?

Continuous action that then become second nature

What are examples of central pattern generators?

Legs while running, arms while swimming

When the ____ activates the primary motor strip it triggers _____

frontal lobe, a specific muscle or central pattern generator making a movement occur

What are other pathways and structures that aid in fine motor and movement modifying?

Basal ganglia, thalamus, brain stem, cerebellum

Why are pathways and structures for fine tuning more spread out with a lot of synapses?

You have to think more about what you do

What is reaction time?

Time between stimulus and first movement NOT GOAL COMPLETION

What makes up reaction time?

Premotor and motor time

What is premotor time?

Time for brain to process stimulus, decide what to do, and send a signal down corticospinal track to muscle

What would be used to track premotor time?

EMG

What is motor time?

Time from when signal reaches muscle to when it moves

What is movement time?

Time from start of movement to end of movement

What is response time?

Time from stimulus to goal achievement

What makes up response time?

Reaction time and movement time

If I drop a ball and my partner leans to grab it but doesn’t get to it yet, what is this called?

Reaction time

If I drop a ball and my partner grabs the ball what is this called?

Response time

What is simple reaction time?

A preset response with go signal, no decision necessary

If I am racing and I see a green light and immediately go what kind of reaction is that?

Simple

What is choice reaction time?

Needs to evaluate different options, need for processing demand increases decreasing reaction time

If you are playing whack a mole what kind of reaction time would you have if you are waiting to see which one arises?

Choice

What is discrimination reaction time?

Go/ No go

Multiple stimuli with multiple responses

If you are playing a shooting game and there are both hostages and enemies popping up, what kind of reaction time would you have to hesitate hitting hostages?

Discrimination

What is the speed accuracy trade off?

People tend to sacrifice one for the other

Younger people tend to choose _____ over ______

Speed over accuracy

Older people tend to choose ____ over _____

Accuracy over speed