lecture 8 - brain and muscles

Question 1

cerebellum

Answer 1

interact w sensorimotor hierarchy. coordinate and modulate.
important for sequence motor learning.
compares M1, M2, motor signals from brain stem and somatosensory, vestibular systems
complex = 10% mass, 50% neurons.
also sensory, cognitive and emotional function.

Question 2

cerebellar damage

Answer 2

devestates motor function. no precise control of direction, force, velocity. no adaptation to changign conditions

Question 3

basal ganglia

Answer 3

interact with sensrimotor hierarchy
coordinate, modulate cortical activity. interconnect sensory and motor areas. role in high level cognition.

motor loop : cortical input -> BG -> thalamus -> motor cortex

cognitive - procedural/habit learning

Question 4

2 major dorsolateral tracts

Answer 4

dorsolateral corticospinal tract

dorsolateral corticorubrospinal tract

Question 5

dorsolateral corticospinal tract

Answer 5

direct
voluntary movement
m1 –> medulla (decussate) –> directly synapse on motor neurons of distal muscles.
only present in animals that can move digits independently
betz cells!

Question 6

betz cells

Answer 6

large pyramidal cells in M1. axon at base of neocortex. terminate in lower regions of spinal cord on leg motor neurons. involved in rapid and powerful voluntary leg movements.

Question 7

dorsolateral corticorubrospinal tract

Answer 7

indirect.
M1 –> red nucleus (decussate) –> medulla.
some terminate on trigeminal nerves, others to interneurons which innervate motor neurons of distal muscles.

Question 8

2 major ventromedial tracts

Answer 8

ventromedial corticospinal tract

ventromedial cortico-brainstem-spinal tract

Question 9

ventromedial corticospinal tract

Answer 9

direct
posture and locomotion - well learned task.
descend ipsilaterally, branches diffusely - no decussation. innervated both sides of spinal grey matter

Question 10

ventromedial cortico-brainstem-spinal tract

Answer 10

indirect
feed into complex network of brain stem structures
each side carries both hemispheres. synapse on several spinal cord segments - control proximal trunk and limbs

Question 11

brainstem structures in VM CBS tract

Answer 11

tectum - auditory (inferior colliuli - sound localization), and visual (superior colliculi - eye movement)
vestibular nucleus - balance, contributes to cerebellum
reticular formation - motor programs for complex species - specific movements.
well learned reflexes.
motor nuclei of cranial nerves - control facial muscles

Question 12

similarities in dorsal and ventral tracts

Answer 12

project from M1
mediate voluntary movement
each composed of 2 tracts.

Question 13

differences btw dorsal and ventral tracts

Answer 13

ventral more diffuse. activate proximal muscles. posture and whole body movement. species- specific activity.
doral - terminate contralateraly. activate distal muscles. limb movements. redundancy in tracts.

Question 14

define motor unit

Answer 14

single motor neuron -> all fibers innervated.
neuron fires ALL muscle fibers of motor unit.
different number of muscle fibers innervated by each motor neruon. fewer fibers = more selective motor control.

Question 15

skeletal muscles - direction of force, mtoor end plate

Answer 15

generate force in one direction only - contract muscle. * need opposing muscle group for opposite function
motor end plate = on each muscle fiber, activated by acetylcholine. activation contracts fiber

Question 16

2 muscle fiber tyeps

Answer 16

fast - white
not highly vascularized. contract and relax quickly. tire quickly

slow - dark
highly vascularized. weaker, slower. sustained contraction = maintain activity indefinitely

Question 17

2 categories of muscles required

Answer 17

flexor - bend/flex

extensor - straighten /extend

Question 18

synergistic vs antagonistic muscles

Answer 18

synergistic = contraction produce same movement (either side of joint)
antogonistic = contraction produce opposing movement (on same side of joint

Question 19

2 types of contraction

Answer 19

isometric contraction: increased tention on tendon. no shortening/contraction of muscle. jsut hold

dynamic contraction: contraction followed by lengthening. movement

Question 20

tension increased by

Answer 20

increse number of neurons firing

increasing firing rates of neurons.

Question 21

monitor muscle tension

Answer 21

golgi tendon organ.
embedded in tendon. more tension - more pull on tendon.
high tension = feedback to inhibitory interneuron in spinal cord causes muscle to relax. other muscles increase contraction to make up for that

Question 22

monitor muscle length

Answer 22

muscle spindle. embedded in intrafusal muscle in extrafusal muscle. extrafusal muscle contract, so do inrafusal - muscle spindle detect shortening.

Question 23

stretch reflex

Answer 23

monosynaptic.
hit = tug tendon = lengthen of muscle. in response contract = kick.
muscle spindle sensory afferent nerves fire - cause gentral horn motor neruons to fire = kick.

Question 24

withdrawal reflex

Answer 24

suddenly pull back when touch something painful
not monosynaptic. 1.6 msec to cross 2 synapses. one interneuron.
higher centres also turned on - multisynaptic - to deal with withdrawal.

Question 25

reciprocal innervation

Answer 25

antagonistic muscle pairs counter-contract. allow for smooth & quick movements

Question 26

recurrent collateral inhibition - renshaw cells

Answer 26

renshaw cell = small interneuron. motor neuron synapses on muscle AND renshaw. renshaw then inhibits motor neuron to silence it. = negative feedback loop to give itself rest.

Question 27

walking as a reflex

Answer 27

reflex must be plastic - adjust to output.

with severed spinal cord, idnividual can walk when they have sensory feedback.

Question 28

comple movements moved down to lower areas. so high areas?

Answer 28

high areas inform of goals and help with intentions but dont carry out reflex.

Question 29

motor equivalence

Answer 29

sensorimotor system is plastic.
motor equivalence - same baasic movement carried out in multiple ways with different muscles
writing with hand or toe = similar font bc of motor equivalence

Question 30

sensorimotor doesnt need conscious perception, just needs …

Answer 30

sensory feedback.

ebbinghaus illusion - consciously perceived differently, but sensorimotor preps finger gap to be same size.

Question 31

species specific behaviours without practice & without limbs

Answer 31

• so engrained that they do same behaviour in same sequence to a tee. use alternate sensory feedback when missing limb.

Question 32

central sensorimotor programs with practice

Answer 32

response chunking - learn sequence as a chunk

shift control lower levels- advantageous, frees up higher levels, greater speed at lower level, more parallel processing

Question 33

sensorimotor learning

Answer 33

well -practiced sequence - shift sequence knowledge down to lower areas. hgiher association areas freed up.