the sensorimotor system

Question 1

what is motor control?

Answer 1

regulation of movement. conscious and unconscious regulation of muscle force. complex sensory feedback system involved.

Question 2

what are the different types of motor control?

Answer 2

• voluntary: running/walking/talking
• goal directed: conscious, explicit, controlled
• habit: unconscious, implicit, automatic
• involuntary (no control): eye movements, facial expressions, diaphragm, cardiac

Question 3

what is the vestibular system?

Answer 3

a sensory system that is responsible for providing our brain with information about motion, head position, and spatial orientation
-helps us keep balance

Question 4

description of sensorimotor system

Answer 4

• hierarchial
• motor control by lower (cell body that projects from brainstem/spinal cord to muscle) and upper motor neurons (higher centres e.g. brain and project to meet lower at spine)
• descending control system with ascending feedback from sensory systems, basal ganglia and cerebellum

Question 5

muscles

Answer 5

• contract/relax
• cardiac, smooth and skeletal
• activation of muscle fibres is all or none
• antagonistic arrangement

Question 6

how do muscles contract?

Answer 6

when muscle contracts, myosin heads move across actin and form myosin cross-bridges
-atp (produced by oxidative metabolism) provides energy for bond to be broken

Question 7

purpose of ATP and rigor mortis

Answer 7

without ATP due to no oxygen (death), myosin molecules stay bound to actin filaments and the muscles become rigid (stay contracted)
-calcium released from packets inside of muscle cells causes rigor mortis

Question 8

slow twitch muscle fibres

Answer 8

can combine lots of force and sustain over a long period of time e.g. posture

Question 9

fast fatigue resistant muscle fibres

Answer 9

cannot sustain force for long period of time - will tire e.g. jogging, running

Question 10

fast fatigable muscle fibres

Answer 10

sustain force for very short period of time e.g. jumping, fast movements

Question 11

the motor unit

Answer 11

a motor unit = single alpha motor neuron + muscle fibres that it innervates

• fewer fibres means greater movement resolution e.g. finger tips/tongue
• more motor neurons –> more fibres contract –> greater power

Question 12

what is a motor pool?

Answer 12

• all the lower alpha motor neurons that activate a muscle

- different number of motor pools for different muscle fibres

Question 13

what senses tension/force?

Answer 13

golgi tendon organs

• where the muscle joins the bone
• sends ascending sensory info to brain via spinal cord about how much force there is in the muscle
• under extreme tension–>they inhibit muscle fibres to prevent damage

Question 14

what senses length (amount of stretch on the muscle)?

Answer 14

muscle spindles

Question 15

reflex circuit

Answer 15

• extrafusal muscle fibres give force
• intrafusal muscle fibres (have muscle spindles wrapped around them) sense stretch - innovated by separate motor neuron –> gamma motor neurons

Question 16

what is reciprocal innervation?

Answer 16

• antagonistic muscles, contraction of one and relaxation of another
• allows smooth movements

Question 17

why do cats always land on their feet?

Answer 17

• righting reflex/vestibular system detects body isn’t upright and gravity
• info integrated from visual, somatosensory and proprioceptive sensory input
• cerebellum important

Question 18

what are brainstem structures?

Answer 18

• pathways and nuclei within brainstem connect sensory input to motor output in direct ways
• old (cortex is new bit)

Question 19

primary motor cortex

Answer 19

exerts direct top down control over muscular activity with as few as one synapse in spine between cortical neuron and innervation of muscle cells
-has direct affect on lower motor neurons

Question 20

basal ganglia and cerebellum role in motor control

Answer 20

• basal ganglia sends inhibitory signals to motor cortex

- cerebellum sends excitatory signals to motor cortex

Question 21

what is the homunculus?

Answer 21

representation of body parts in relation to sensory/motor function
-it is an oversimplification because if you damage part of finger it doesn’t mean you lose control over all of it

Question 22

dorsolateral tracts

Answer 22

• innervate contralateral side of one segment of spinal cord
• sometimes project directly to alpha motor neuron
• project to distal muscles e.g. fingers

Question 23

ventromedial tracts

Answer 23

• diffuse innervation projecting to both sides and multiple segments of spinal cord
• project to proximal muscles of trunk and limbs