Lecture 18 - Motor Systems

Question 1

Sensorimotor System Definition

Answer 1

• A subcomponent of the comprehensive motor control system of the body.
• Encompasses all of the sensory, motor, and central integration and processing components involved with maintaining joint homeostasis during bodily movements.

Question 2

Proprioception

Answer 2

• The sense through which we perceive the position and movement of our body.
• Includes our sense of equilibrium and balance; senses that depend on the notion of force.
• Used for the regulation of total posture (postural equilibrium) and segmental posture (joint stability).

Also initiates several conscious peripheral sensations; muscle senses.

Question 3

Foursubmodalitiesof muscle sense:

Answer 3

(1) Posture.
(2) Passive movement.
(3) Active movement.
(4) Resistance to movement.

Question 4

Somatosensation definition

Answer 4

• More global and encompasses all of the mechanoreceptive, thermoreceptive, and pain information arising from the periphery.
• Somatosensory information leads to the sensations of pain, temperature, tactile (ie. touch, pressure, etc).

Question 5

Primary Somatosensory Cortex

Answer 5

• Located at front of the parietal lobe.
• Receives information about what the body is touching and feeling.
• Sensory information is received from tracts of neurons that. extend up through spinal cord and through the hindbrain and midbrain
• Area of cortex relates to sensitivity of body part.

Question 6

Where does somatosensory information come from?

Grouped into three functions:

Answer 6

• Nociception: sensations of pain and temperature.
• Hapsis: sensations of fine touch and pressure.
• Proprioception: awareness of the body and its position in space.
• Mechanoreceptors: Often wrapped around hairs, react to distortion like bending and stretching. On afferent axons

Question 7

Motor programs also use proprioception to adapt in two ways:

Answer 7

1) Through using proprioceptory information with respect to the external environment; adjusting to accommodate unexpected perturbations or changes in the external environment.

• 2) Through the planning and modification of internally generated motor commands.
• Must consider the current and changing positions of the joints involved to account for the complex mechanical interactions within the components of the musculoskeletal system. (adjust behaviour, planning and frontal lobe) (muscle tension, force to use,
• How we manage our slip sense,

Question 8

Principal cortical domains of the motor system:

Answer 8

• The primary motor cortex (M1) lies along the precentral gyrus, and generates the signals that control the execution of movement.
• Secondary motor areas are involved in motor planning.

Question 9

Motor Neuron Tracts

Answer 9

Corticospinal tract:

The corticospinal tract is the main pathway for control of voluntary movement in humans.

Only direct pathway directly from cortex to spine

Other motor pathways:

• Control posture and balance, coarse movements of the proximal muscles, and coordinate head, neck and eye movements in response to visual targets.
• Subcortical pathways can modify voluntary movement through interneuronal circuits in the spine and through projections to cortical motor regions.

Question 10

Two types of motor neurons in the spine:

Answer 10

• Alpha motor neurons: innervate muscle fibres that contribute to force production.
• Gamma motor neurons innervate fibres within the muscle spindle.
• (not identical twins)

Question 11

motor pathway in the spinal cord

Answer 11

• Fibers in the corticospinal tract synapse onto motor neurons and interneurons in the ventral horn of the spine.
• (thousands of signals, many things happening, look at pic
• These interneurons receive input from the same regions and allow complex circuits to develop.

Question 12

Spinal cord organization

Answer 12

• Spinal cord is organized into dorsal root ganglia (somatosensory) and ventral root ganglia (motor).
• There are 30 pairs of spinal nerves, each of which is made up of dorsal and ventral roots and they exit the spinal cord through a notch in the vertebrae of the spine.
• Each of the 30 dorsal roots innervate different areas of the skin referred to as dermatomes.
• Would have to cut all 3? Dermatomes to have no sensation/movement?

Question 13

Brain regions/motor control

Answer 13

• Information from muscle spindles, Golgi tendon organs and other sensory organs are directed to the cerebellum.
• The actual motor programs are generated in the basal ganglia which send output to other subcortical brain regions and the cortex.
• Will first go through basal ganglia, then up through other brain areas

Question 14

Basal Ganglia

Answer 14

• Composed of three structures; caudate nucleus, putamen, and globus pallidus.
• Critically important for initiating movements and maintaining muscle tone.
• The striatum receives most of the motor input for the basal ganglia and the globus pallidus serves as the primary output.
• Basal ganglia in constant communication with the thalamus
• Striatum: a centre for neurogenesis

Question 15

Cerebellum in motor control

Answer 15

• Very important in terms of the modulation of motor movements and the acquisition of motor skill.
• signature

Three zones:

• Lateral zone (coordinating multi-joint movements, also has a role in the acquisition of motor skills).
• Intermediate zone (specialized for guiding skilled limb movement e.g. reaching, grasping).
• Vermis (involved with posture and coordinating whole-body movements).

Question 16

Secondary Motor Cortices

Answer 16

What are they?

• Other regions of the cortex involved in motor function.
• Involved in motor planning.

They include:

• The posterior parietal cortex: involved in transforming visual info into motor commands.
• The premotor cortex: involved in the sensory guidance of movement, and controls the more proximal muscles and trunk muscles of the body.
• Supplementary motor area: involved in the planning of complex movements and in coordinating two-handed movements.
• The supp and pre both send to M1

Question 17

Association Cortex for movement

Answer 17

What is it for?

• Control of voluntary behaviour.
• The frontal lobe or prefrontal association complex is involved in planning actions and movement.

Question 18

Posterior Parietal Association Cortex

Answer 18

• Involved in the processing of spatial information.
• Receives input from a number of systems including proprioception, hapsis, and vision.
• Generates a mental image of the body and judges the relative position of the body with respect to external objects.
• Has a critical role in producing accurate movements.
• Communicates with the dorsolateral prefrontal cortex to guide movements.

Question 19

Dorsolateral Prefrontal Cortex

Answer 19

•Involved in the decision to execute voluntary movements.

•

• Actively directs lower areas in the motor hierarchy such as the secondary and primary motor cortex.
• Thought to also be involved in assessing the likely outcome of planned movements.
• “bossy part of brain”
• Some involvement of past experience/
• Activates when movement is imagined. As opposed to execution areas like M1

Question 20

what are Motor Skills

Answer 20

• A motor skill is a learned ability to cause a predetermined movement outcome with maximum certainty.
• Motor learning is relatively permanent. Not going to forget how to ride a bike. Music: muscle memory
• Performance is an act of executing a motor skill.
• Goal of motor skills: to reduce energy output and

Question 21

Exercise

Answer 21

Forced exercise: (out of comfort zone)

This is the most neuroprotective

• A mode of aerobic exercise in which exercise rate is augmented mechanically to assist the subject in achieving and maintaining an exercise rate that is greater than their preferred voluntary rate of exercise.
• Recent studies show forced exercise in particular to have neuroprotective properties and improve motor function.
• Neuroprotection includes lessened neurologic deficit, increased neurogenesis, and increased cerebral metabolism.
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4061835/

Question 22

Skilled performance

Answer 22

New dancers:

• Learning a new motor skill involving the performance of complex sequenced movements like dancing: involves primary motor cortex, primary sensory cortex (in order to monitor how your muscles are moving) and caudate nucleus and thalamus.
• Caudate and thalamus help coordinate, speed up and smooth out the movements in response to how the movements feel to you.
• Skilled performance = increased automacity:
• Controlled processes: attention demanding, conscious and inefficient.
• Why it’s hard to stop a signature mid-way
• Automatic processes are rapid, smooth, effortless, demand little attentional capacity and are difficult to consciously disrupt.
• The cerebellum retrieves the memory of how to move our muscles quickly, efficiently and without thinking.
• http://neuroarts.org/pdf/SciAm_Dance.pdf
• https://mimm.mcmaster.ca/publications/pdfs/dance.pdf

Question 23

Brains moving parts

Answer 23

Question 24

Stress and sensory/motor cortices

Answer 24

• Complex networks throughout the primary sensory and motor cortices are tied directly to our stress responses.
• Elaborate connections between the motor areas in the brain connect to the adrenal glands.
• Whole lot of neurons from primary motor cortex work to control the adrenal medulla.