spinal and motor control

Question 1

motor unit control system

Answer 1

-controlling levels of force

Question 2

sensory control system

Answer 2

-feedback of angle/movement/force generated

Question 3

Alpha motor units

Answer 3

• class of neurones that control muscle
• Cell bodies found in VENTRAL HORN OF SPINAL CORD (brain stem for eye muscles)*
  -Axons form peripheral nerves going out to muscles
  -controls every movement in the body

Question 4

anatomy of the spinal cord

Answer 4

3 components:
-Roots – dorsal = sensory=info coming into spinal cord , ventral = motor=info coming out the spinal cord, – origin of peripheral nerves
-White Matter – ascending and descending neuronal pathways (up to and down from the brain)
-Grey Matter – neuronal cell bodies (including α-motorneurons)
-does not recover after injury

Question 5

-motor neuron disease

Answer 5

-affects a-motor neurons in the spinal cord= loss of body movement, meant except from eye movements

Question 6

explanation of the motor unit in general

Answer 6

• the smallest unit in controlling movement
  -one motor neurone a single axon and every muscle fibre it connects to
• when the alpha motor neuron fires the whole motor unit fires along with muscle fibres connected

Question 7

size of motor units

Answer 7

• the larger the motor unit the more fibres it is connected to this is dependent on its location in the body

Question 8

types of motor units within a muscle

Answer 8

-S (slow) - slow contracting, v. resistant to fatigue,v. small force, aerobic
- FR (fast fatigue resistant) - faster contracting,fatigue resistant, low force, mainly aerobic*
-FF (fast fatigable) - fast contracting, fast fatigue,high force, anaerobic
from small to large

Question 9

limitation of motor units

Answer 9

• Fixed pool of motor units that we can activate(the smallest units of control)
  -Can only send a binary signal (1 or 0) to a motor unit

Question 10

the rate coding method of how the brain increases force in the muscle

Answer 10

When the brain wants to increase the force generated by a muscle, it increases the rate at which these action potentials are fired. This higher frequency of firing leads to a stronger contraction of the muscle fibers.
-mechanism is used both in motor signals to control muscle movement and in sensory signals to convey the intensity of stimuli.

Question 11

recruitment of additional motor units of how the brain increases force of contraction

Answer 11

When the brain wants to increase muscle force, it activates more motor units to join in the contraction.
-Initially, only a small number of motor units may be recruited, resulting in low muscle tension. As the demand for force increases, the brain recruits more motor units, leading to higher muscle tension.

Question 12

recruitment of motor units method

Answer 12

-first start of with recruiting mainly slow units when there is low activity and then with increasing activity and more powerful motor units are added(FRs and FF)

Question 13

vision

Answer 13

-via the eyes on the head
-info comes in from the dorsal pathway to tells us where we are
-info goes through the ventral stream to tell us what we are looking at

Question 14

vestibular system

Answer 14

-inner ears in head
-vestibules-detect balance and cochlea detects hearing
-semi-circular canals detect the rotations and translations of the head

Question 15

role of the semi-circular canals in the vestibular system

Answer 15

-Three on each side of the head which are arranged at right angles to each other.
which allows them to detect movement in three dimensions

-When you move your head, the fluid inside your inner ear withinthe semi circular canals (called endolymph) doesn’t move right away because of its inertia
-This delay in fluid movement makes a jelly-like structure in your inner ear, called the cupula, bend or distort. This bending is detected by tiny hair cells in your inner ear.
-Continuous rotation of the head, such as when spinning on a roundabout or riding a rollercoaster, can cause prolonged stimulation of the vestibular system, leading to dizziness or vertigo. evn when you have stopped moving

Question 16

otiliths

Answer 16

• inthe inner ear and part of the vestibular system
• calcium carbonate structures found in two places within the inner ear:
• utricle=sense acceletrations in the horiontal plane
• saccule= sense accelrations in the verticle plane
• Provides inertia – embedded hair cells detect relative movement of the otiliths and dtect movement in an array of directions

Question 17

proprioception

Answer 17

-the body’s ability to sense its own position, movement, and spatial orientation without relying on vision
-two important structures involved
-muscle spindles= muscle length and stretch sensors
-golgi tendons organs= muscle tension sensors

Question 18

muscle spindals in proprioception

Answer 18

• sensory fibres wrapped around muscle fibres(intrafusal fibres) arranged parallel with muscle
  -two types of sensory fibres:
  -II afferents= =detects joint angle
  -Ia afferents= detect joint movement

Question 19

golgi tendons organs

Answer 19

-sensory fibres embedded in tendons of muscles
-arranged in series with muscle = detect muscle tension and forces applied to joints

Question 20

efference copy

Answer 20

-the brain makes an internal copy of the outflowing (efferent)informatio, motor signals
-not a feedback system so is immediate so we get a predicted outcome t
-explains why we cant tickle ourselves

Question 21

advantages of the efference copy system

Answer 21

• Good for controlling fast movements – don’t need to wait for sensory feedback to arrive
  -Good for movements which are not usually affected by external forces don’t – e.g. eye movements

Question 22

disadvantages of the efferent copy system

Answer 22

-Doesn’t allow for unexpected changes (e.g. externally applied forces)
-No absolute reference – needs updating using sensory feedback
-Less accurate for slower movements

Question 23

knee jerk reflec(strech reflex)

Answer 23

-. Muscle spindle is stretched causing afferent neuron to fire
-. Monosynaptic connection in spinal cord leads to contraction of agonist muscle
- Inhibition of antagonist muscle through inhibitory interneuron

Question 24

what do EMG recordings of motor units look like?

Answer 24

measures action potentials of all muscle fibres in motor units
-larger spike=action potential of larger motor units = lots of muscle fibres firing at once
-smaller spike=action potential of smaller motor unit= smaller number of muscles fibres firing at once