Motor Control

Question 1

Reflex movements

Answer 1

• rapid reproducible, automatic motor response to external stimulus
• employs simple neural circuit involving peripheral nerves and spinal cord
• does not require involvement of higher Brian centres

Question 2

Voluntary movements

Answer 2

• wide variety of movements of varying speed, duration, and complexity
• typically involves complex patterns of sensory and motor processing
• initiated on demand (voluntarily) in brain and many higher centres involved in control

Question 3

Reflex movements

Answer 3

• doesn’t require involvement of higher Brian centres
• employs simple neuronal circuit involving peripheral nerve + spinal cord
• rapid reproducible, automatic motor response to external stimuli

Question 4

Voluntary movements

Answer 4

• wide variety of movements of varying speed, duration and complexion
• typically involves complex patterns of sensory motor processing
• initiated on demand (voluntary) in brain and many higher control centres involved in control

Question 5

STRETCH REFLEX - INVOLUNTARY

Answer 5

• monosynapitc
• stretch of muscle, lengthens stretch receptors in muscle spindles
• length change initiated a response in the sensory nerve fibre (sesnsory nerve fibre has its cell body in the dorsal root ganglion - somatic sessory neurons are uni polar that send one process out in one direction and another out in the opposite direction)
• stretch initiates the opening of mechanically gated ion channels on nerve endings allowing an influx of sodium ions
• this initiates a receptor potential (type of local potential) which if big enough brings sensory never fibre to threshold
• an AP is generated and conducted up the sensory nerves, into the spinal cord (via dorsal root ganglion)
• this makes an excitory synapse on motor neuron cell body in ventral horn
• causes neurotransmitter release which brings cell to threshold (if signal strong enough)
• this motor neuron then fires an action potential which will go out to periphery to NMJ on muscle fibres causing them to contract

Question 6

Mechanical ion gating

Answer 6

• muscle stretch receptors (proprioceptors) have mechanically gated ion channels
• when stretched, the channels open allowing entry of positive charge and local depolarisation occurs, called a receptor potential
• if the receptor potential is big enough, an action potential will be triggered in the sensory nerve and information will flow into CNS from site of stimulation

Question 7

Withdrawal reflex

Answer 7

• involuantary
• polysynaptic reflex - multiple synapses
• potentially harmful stimulus interacts with sensory receptors on skin - (nociceptors - a subsets of free nerve endings in skin)

Question 8

Thermal stimulius come back to this after tutorial

Answer 8

Interneuron synapses w/ not only the neuron which is providing withdrawal but also interacting with an inhibitoy neuron, provides inhibitory signal to motor neurons which are connected to extensors
- this inhibits neuron that would excite the muscle - internearuon releases a strong inhibitory signal to generate a large IPSP at the cell body if inhibitory neuron to prevent it extending

Question 9

Voluntary movement

Answer 9

• requires motivation and planning
• staring point must be known
• uses information form sensory receptors such as muscle spindles - these photoreceptors are sending information to the brain about the length of muscles
• prooteoreceptors are active all the time - to understand where in space parts of your body are

Question 10

Pre frontal cortex

Answer 10

• organises thoughts and actions
• intimately involved with ‘executive funcitons”
• cognitive function - acquiring knoledge through thought experiences
• social behaviour - planning - language - predicting consequences
• used to recall and consider information not currently availdible from enviriontment
• recall past events to plan future events
• behaviours displayed in our actions require decision ,asking that’s based on info about where the body is now as well and into from other sensors and previous knowledge
• prefrontal cortex colabs (sends/shares info) with other brain parts (basal ganglia) and premotor cortex to decide activities - plan at specific frequencies and order
• desire to initiate a movement arises here
• sensory information about the environment and state of body is used to plan movements, neural commands are sent to muscles to generate forces to exicute movements

Question 11

Size of repression of the body area in primary cortex

Answer 11

• size of the representation of the body area in primary motor cortex doesn’t relate to size of the muscle or area or volume of the body that it occupies - a lot to do with the complexity of the movements that the organ can exicute
• complex movements require large amounts of neurons to execute them

Question 12

Left side of the brain controls right side of body

Answer 12

Question 13

Two ways that the basal nuclei adjust patterns of movement

Answer 13

1. They alter the sensitivity of the pyramidal cells to adjust the output along the corticospinal tract
2. They change the excitatory or inhibitory output of the medial and lateral pathways

Question 14

The cerebellum ________ and ______ and _______

Answer 14

The cerebellum monitors balance and equillibrium and adjusts upper motor neurons activity

Question 15

Decision in frontal lobes ——> pre motor cortex ——> basal nuclei , cerebellum

Answer 15

Neurons in pre motor cortex activate neurons in primary motor cortex - there output goes to lower motor neurons in spinal cord (via ventral horn) - their axons activate muscle in periphery
Information comes back from the muscle fibres via cerebellum and basal nuclei to inform cortex how that information is going on

Question 16

Cerebellum

Answer 16

• helps plan, execute and learn motor programmes
• integrates sensory on for w/ planned events
• organises timing of muscle contractions, compares result of planned movement with actual result
• modifies ongoing activity to make movements smooth + accurate

Question 17

Disorders of the cerebellum: results in ataxia

Answer 17

• drunken gait
• tremor
• dysarthria - speech
• dysmetria - judge of distance

Question 18

Proteoreceptive output changes when u initiate movement

Answer 18

N

Question 19

How can the pathway of output be modified

Answer 19

Cerebellum can modify pathway of output through primary motor cortex, so the output of those neurons can be modified progressively to ensure that the movement occurs in a progressive expected way

Question 20

Voluntary motor control loop

Answer 20

• desire to exicute a movement arises in brain - is informed by memory and environment and sensory input in the PREFRONTAL CORTEX
  -information passes in the form of APS to pre motor cortex, basal nuclei and cerebellum - these then sense where the correct muscles are in relation to where they need to be
• basal nuclei and cerebellum help pick out which neurons in primary motor cortex need to be activated to activate required muscles of planned movement
• when motor neurons in primary motor cortex are activated, information comes down the corticospinal pathway, crosses the pyrimisds (medulla oblingata ??) and descends the spinal cord, these neurons then make direct connections onto the cell bodies of lower motor neuromas o the ventral horns of the spinal cord
• these motor neurons when brought to threshold, fire AP, their nerves are carried into the PNS through the ventral roots to skeletal muscle fibres, where the muscle fibres are bought to threshold every time, moves skeleton.
• this changes the output from the sensory apatruts in the muscle spindles which gets fed back into the brain, specifically the cerebellum, this informaition is then used back to primary motor cortex and basal ganglia to adjust the patterns of action of the neurons in the primary motor cortex so that the on going movement is smooth

Question 21

How sensory info and neural commands work together to create movement

Answer 21

Sensory information about the environment and the state of the of the body is used to plan movements, neural commands are sent to muscles to generate forces to execute movements

Question 22

Voluntary movements overview

Answer 22

• sensory info about the environs ent and the state of the body is used to plan movements, neural commands and sent to muscles to generate forces to execute movements
• desire to initiate a movements aisles in the pre frontal cortex
• descending pathways to brain stem and spinal cord are activated
• sensory info is fed back into system, and the activitivity of motor neurons is modulated to modift and control the movement

Question 23

Answer 23