Motor System

Question 1

Motor = ?

Answer 1

movement

Question 2

Involuntary movement?

Answer 2

triggered by stimulus and the brain isn’t involved (so it doesn’t require conscious effort)

Question 3

Voluntary movement?

Answer 3

Requires conscious effort and is all planned out before the action(s) are executed (think MASTERMIND)

Question 4

Ultimate target of all motor neurons?

Answer 4

The muscles.

Question 5

How does muscle contraction work?

Answer 5

lower motor neurons synapse directly onto the muscle releasing acetylcholine as their neurotransmitter in the space between the terminal and the muscle (called the neuromuscular junction)

when the signal is recieved the muscle cells are depolarized allowing the flow of calcium into the cell

the calcium starts a chain reaction in the myofibrils causing the thin and thick filaments to slide past each other this shortens the myofibril and causes contractions

this can also happen in reverse if there is an absence of acetylcholine in the lower motor neurons

Question 6

Where are the cell bodies of lower motor neurons located?

Answer 6

Spinal cord

Question 7

Where are the cell bodies of upper motor neurons located?

Answer 7

Brain and brainstem.

Question 8

Where do lower motor neurons mostly get their information from?

Answer 8

The upper motor neurons (likely cause their closer to the brain)

Question 9

How does the knee jerk (myotatic) reflex happen?

Answer 9

a rubber mallet is hit on the tendon which is connected to the quadriceps muscle. the tendon is pulled therefore pulling the muscle. this triggers action potential in the muscle spindle. the muscle spindle sends the info through its axon (afferent) to the lower motor neurons of the quadriceps muscle in the spinal cord via the dorsal. the lower motor neurons tell the knee to jerk. since the brain isn’t involved in the action, you can’t consciously respond.

Question 10

What is the primary motor cortex?

Answer 10

works and plans voluntary actions

Question 11

What is motor planning?

Answer 11

mapping out which muscles and limbs are needed to perform a behavioral goal

Question 12

What other parts of the brain does the primary motor cortex work with to plan voluntary actions?

Answer 12

Works with the supplementary cortex and the premotor cortex

Question 13

What do scientists use to predict an organism’s behavior before it occurs?

Answer 13

The cell bodies that are highly active before the act is initiated.

Question 14

What are the two Lateral Pathways?

Answer 14

Corticospinal tract and the Rubrospinal tract

Question 15

Describe the Corticospinal tract.

Answer 15

runs from the cerebral cortex to the spine starting in the primary motor cortex

axons from these organs run through the white matter of the brain and brainstem where they form a bump on each side of the medulla (this pathway is also referred to as the pyramidal tract?

at the bottom of the medulla, this pathway crosses to the other side to go down the spinal cord

these axons synapse on lower motor neurons in the central grey matter of the spinal cord

longest neurons in the body because they come from the brain to the targeted muscle

Question 16

Describe the Rubrospinal Tract.

Answer 16

not as crucial to the human body as it is to other animals

begins in a small region of the brainstem called the red nucleus

crosses over at the midbrain before descending

seems to be in control of muscle tone

Question 17

What both Lateral Pathways have in common?

Answer 17

most voluntary info is carried

these pathways are found in the white matter on the sides of the spinal cord

sometimes the corticobulbar system is included with the lateral pathways despite not being in the spinal cord. it controls the brainstem nuclei that innervate the cranial muscles that control voluntary facial movements.

Question 18

What are the three Ventromedial Pathways?

Answer 18

Vestibulospinal Tract, Tectospinal Tract, and Reticulospinal Tract

Question 19

Describe the Vestibulospinal Tract.

Answer 19

originates in the vestibular

organs of the inner ear

provides info about the direction of gravity, spin, and other forces

most of the axons project up to the brain to make the organism aware of the forces

some of the axons project down to compensate for the changes in force for the neck and head and leg muscles for balance

Question 20

Describe the Tectospinal Tract.

Answer 20

originates in the roof or tectum of the midbrain

controls the movement of the head in response to auditory and visual stimuli

Question 21

Describe the Reticulospinal Tract.

Answer 21

originates in the reticular formation found in the pons

targets the torso and legs to go against the forces of gravity and the keep balance

Question 22

What two regions affect the output of the descending motor pathways?

Answer 22

The Basal Ganglia and the Cerebellum.

Question 23

Where is the Basal Ganglia located?

Answer 23

it’s a group of structures located deep within the cerebrum

Question 24

What is the Basal Ganglia associated with?

Answer 24

initiating and executing movements

Question 25

What does the Basal Ganglia do?

Answer 25

prevent unwanted movements and promotes necessary ones to completing the certain action

Question 26

Where is the cerebellum located?

Answer 26

in the back of the brain beneath the occipital and temporal lobes

Question 27

What does the cerebellum do?

Answer 27

feedback control system; constantly adjusting and comparing desired output to the input to get the desired results

always improving

Question 28

What cool cell does the cerebellum have?

Answer 28

Purkinje cell: almost 2 dimensional with their coral array dendritic branches all the output comes from these cells