P5: motor behavior

Question 1

Difference and examples for simple and complex reflexes:

Answer 1

simple: knee-jerk reflex: monosynaptic
complex: withdrawal reflex: polysynaptic: excitatory interneuron for agonist and inhibitory interneuron for antagonist.
walking: very complex

Question 2

afferent/efferent Neuron

Answer 2

afferent: from sensor to processing site: spinal cord/brain
efferent: motor neuron: from processing site to muscle

Question 3

positive Babinski sign

Answer 3

toes bend up because upper motor neurons are not inhibiting the plantar extensor muscles –> toes bend up

Question 4

Reciprocal innervation

Answer 4

Combination of excitation and inhibition of Neurons in reflexes. E.g.: withdrawal of hand from heat: excite biceps, inhibit triceps

Question 5

dorsolateral tracts: what do they do, how do they travel?

Answer 5

Dorsolateral: also limbs, redundancy with ventromedial, but only dorsolateral can mediate independent movements of the fingers, distal, fingers, go to contralateral side and sometimes directly to motor neurons
Cortico Rubrospinal: red nucleus: midbrain, also control of facial muscles. Not so important for humans.
Corticospinal: Direct though medullary pyramid with bulges (Wülste):

Question 6

ventromedial tracts: what do they do, how do they travel?

Answer 6

Ventromedial: proxal, posture, trunk, limbs, shoulder. travel downwards ipsilateral, innervate interneurons on both sides, posture and whole body movements: walking and climbing
Cortico-Brainstem-spinal: go first to brainstem, indirect
Corticospinal: direct

Question 7

closed vs. open loop

Answer 7

Closed loop: with feedback
Open loop: no feedback

Most movements consist of these two types of systems: open loop/preprogrammed sequences of movement are fine-tuned by closed-loop systems which fine tune by sensory feedback.

Question 8

Proprioception

Answer 8

Body sense; information about the position and movement of the body that is sent to the brain.
Two types of proprioceptive receptors are:
muscle spindles: monitor muscle length
Golgi tendon organs: monitor muscle tension

Question 9

What are the parts of the secondary motor cortex and what do they do?

Answer 9

Can contribute to behavior directly and indirectly through M1
Consists of two parts:
SMA: Supplementary Motor Area: planning movements that are internally generated  to plan moving sequences

Premotor Cortex: directs movements in response to external stimuli: defensive movements, feeding behavior. This cortex also contains the mirror neurons which fire when we do and observe the same type of behavior.

Question 10

What is the direct pathway? (basal ganglia)

Answer 10

It facilitates the initiation and execution of voluntary movement.
Basal ganglia lowers inhibition of Thalamus–>Thalamus excites Motor cortex –> more movement

Question 11

What is the indirect pathway? (basal ganglia)

Answer 11

Helps to prevent unwanted muscle contractions from competing with voluntary movements.
Basal ganglia increases inhibition of Thalamus –> Thalamus inhibits Motor cortex –> less movement