Motor

Question 1

reflex vs. voluntary movement

Spinal Reflex

Answer 1

• simple, unvarying, innate/unlearned responses
• do not require brain inputs to the spinal cord (nothing is actually coming down from the brain)

Question 2

reflex vs. voluntary movement

Voluntary movements

Answer 2

• require brain inputs (cognition/brain involvement) to the spinal cord
• motor plan/program: “How will this movement be orchestrated?” is established before an action occurs

Question 3

reflex vs. voluntar movement

proprioception

Answer 3

• knowing position and movement of body
• muscle length
• muscle tension/movement
• aka kinesthesia and is present in every muscle movement you have… it is the body’s awareness sense…innate

Question 4

Circuits that drive movement process

Answer 4

1. receptor
2. sensory neuron
3. integration center
4. motor neuron
5. effector
   -(sense input to integration to motor output)

Question 5

What do motor systems do?

Answer 5

• Sensing the outside world guides action selection (we have to know where things are around us). An action performed accurately approach reward and is reinforced, while an action performed poorly is not reinforced “withdraw from negative”
• CNS produces specific patterns of muscle contractions that lead to specific actions (motor outcome/behavior)

Question 6

Motor systems

Primary motor cortex

Answer 6

initiates main commands

Question 7

Motor systems

Non primary motor cortex

Answer 7

additional motor commands

Question 8

Motor systems

Brainstem

Answer 8

• integrates motor commands from higher brain regions and transmits them to the spinal cord
• responsible for muslces of face, head, and neck

Question 9

Motor systems

Cerebellum/basal ganglia

Answer 9

• modulates (modifies) motor control systems/fine tuning

Question 10

Motor systems

Spinal cord

Answer 10

• reflexes
• also immplements commands from the brain
• muscles of body

Question 11

Motor systems

Skeletal muscle system

Answer 11

determines possible movements

Question 12

Synergists

Answer 12

muscles can be synergists, which means they contract together

Question 13

antagonists

Answer 13

muscles can be antagonists and contract opposing each other

Question 14

“flex” of bicep

Answer 14

motor neurons to biceps are excited while motor neurons to triceps are inhibited

Question 15

How do muscles contract? - first three steps

Answer 15

• alpha motoneuron: sends an axon to a motor end plate that opposes a striated muscle (massive)
• Multiple axon terminals “contact” multiple muscle fibers
• synapses are called neuromuscular junctions

Question 16

What occurs at a neuromuscular junction?

Answer 16

• presynaptic motor neuron terminal
• synapse
• postsynaptic muscle fiber

Question 17

neuromuscular junction neurotransmission

Answer 17

• Alpha motoneuron releases ACh from the motor end plates
• ACh binds to nitoninc acetylcholine receptors (nAChR) to allow Na+ influx
• Creates EPP (end plate potential) which triggers muscle fiber contraction

Question 18

What are Betz cells?

Answer 18

• Pyramidal neurons that produce glutamate and form the homunculus
• found in the primary motor cortex (M1)

Question 19

Describe the structure of M1 pyramidal neurons

Answer 19

• M1 pyramidal neurons form axon bundles
• bundles cross (decussate) in the medulla
• then descend caudally in the spinal cord via corticospinal tract
• synapse onto ventral spinal cord alpha-motoneurons
• muscle fiber contracts

Question 20

Where do M1 pyramidal neurons cross?

Answer 20

in the medulla

Question 21

cross fancy word

Answer 21

decussate

Question 22

Where do M1 pyramidal neurons synapse?

Answer 22

onto ventral spinal cord alpha-motoneurons

Question 22

Where do M1 pyramidal neurons descend?

Answer 22

caudally in spinal cord via corticospinal tract

Question 23

What does the contraction of simple msucle units in M1 do?

Answer 23

lead to simple movements

Question 24

What do the Supplementary motor area (SMA) and premotor cortex do?

Answer 24

* control subsets of M1 neurons * helpful in coordinating activity of muscle units particularly for complex movements

Question 25

What does the SMA do?

Answer 25

* rehearses action before it occurs/plans * doesn't necessarily take the outside environment to account

Question 26

What does the premotor cortex do?

Answer 26

directs movement based on external stimuli

Question 27

Mirror neurons

Answer 27

* located in premotor cortex * neurons active when performing a task are also active when watching someone else perform the same/similary task * useful for learning or cooperation maybe

Question 28

# motor deficits Apraxia

Answer 28

* impairment in beginning/executing voluntary movements even though no muscle parlysis

Question 29

# motor deficits Ideomotor apraxia

Answer 29

* the inability to carry out a simple motor activity in response to verbal command, even though this ame activity is readily performed spontaneously

Question 30

# motor deficits ideational apraxia

Answer 30

the inability to carry out a sequence of actions, even though each element or step can be done correctly

Question 31

What is the EMS and what does it do?

Answer 31

* The Extrapyramidal Motor System * Contains the basal ganglia and cerebellum * Connects w motor cortices to form a closed loop (cortex to EMS to cortex)

Question 32

What is the basal ganglia a part of? What is the basal ganglia's function?

Answer 32

* the basal ganglia is part of the Extrapyramidal Motor System * involved in the initiation of motor action (related to motivational systems and cognition)

Question 33

What is the Cerebellum's function and what is it a part of?

Answer 33

coordination, precision, and accurate timing

Question 34

EMS activation timeline

Answer 34

* the cerebellum and non-primary motor cortices activate after the basal ganglia and primary motor cortex

Question 35

D1 and D2 dopamine receptors

Answer 35

* D1 and D2 are dopamine receptors * D1 receptors exictatory-activate neuron-GO/DIRECT pathway * D2 receptors inhibit neurons- STOP/INDIRECT pathway | in basal ganglia

Question 36

What does dopamine do to the GO and STOP pathways?

Answer 36

* dopamine turns on the GO pathway, which leads to reward-seeking * dopamine turns off the STOP pathway, wich leads to reward-seeking

Question 37

parkinson's disease

Answer 37

* resting tremor, impaired gair, difficult initiating movements * progressive: eventually affects all behavior, including swallowing * unknown etiology (partially genetic, partially environmental) * loss of substantia nigra dopamine neurons * pharmacological therapy involves dopamine replacement

Question 38

Huntington's disease

Answer 38

* chorea * genetic; caused by single allele * longer repeat sequences, earlier onset * eventual striatum cell death

Question 39

What gene causes HD?

Answer 39

trinucleotide expansion in huntingtin gene (>40 repeats) ## Footnote longer repeat sequences, earlier onset