Lecture 15 - Control of movement

Question 1

Voluntary muscle control originates

Answer 1

Voluntary muscle control originates in the brain and must come down the spinal cord in order to activate motor neurons, for the most part the output from the motor cortex is activating interneurons which is the circuitry inside the spinal cord that is designed to remove the level of control down the spinal cord to free up the brain for other purpose

Question 2

Basal ganglia

Answer 2

Basal ganglia = allows planning and intentional movement

Question 3

Cerebellum

Answer 3

Cerebellum - monitor movement and ensures that it is the movement we desired

Question 4

Spinal cord involved in

Answer 4

Processing commands from brain

Reflexes
Stretch reflex (muscle spindle) Lab. 4

Rhythmic motor patterns, from ‘central pattern generators’:

Question 5

Spinal cord & brainstem circuits generate basic patterns of rhythmic muscle activity for:

Answer 5

e.g. such as a snake moving where it undulates its whole body which originates from the spinal cord or a horse changing speed they might think about getting faster but not the movement actually required to do this i.e. they do not consciously change from all fours on the ground to two feet on the ground when going from walking to cantering

Locomotion (walking, running)
Breathing
Chewing

Swallowing
Do not have o think about each motion in these activities, they occur as a sequence of events that flow as a result of the rhythmic activity of the neural circuits

Question 6

Voluntary commands and brains role

Answer 6

Commands from brain start/stop, and regulate speed, force, direction (this is the regulation that occurs for these activities)

Question 7

Primary motor cortex

Answer 7

Ordered map of body (somatotopy)
Regulates spinal cord motor systems
Via Corticospinal (pyramidal) tract - Output from the primary motor cortex foes down the corticospinal tract

Question 8

Somatotopy in primary motor cortex

Answer 8

Body parts represented roughly sequentially across cortex

Area devoted to each part is:

Dependent on level of fine control

Dependent on extent of use
i.e. representation is “plastic”

Damage causes problems with movement, particularly with fine voluntary control in specific parts of the body

Stimulation activates movements in specific parts of the body

Question 9

Corticospinal pathway

Answer 9

Output from motor cortex controls spinal neurons, for fine, isolated movements (crosses to opposite side). [Note: most input is to interneurons]
Major one especially for direct control and more dextrous movements
Crosses over
Goes to larger groups of muscle that control the limbs

Question 10

Brainstem pathway

Answer 10

Coordinated activity in large muscle groups, for posture, locomotion, routine activities (crossed and uncrossed)
Parts crossed and other parts are not crossed

Question 11

Special roles of the primary motor cortex

Answer 11

Special role in controlling force of muscle contractions
Greater rate of neuronal activity, more input to motor units, greater force

Special role in controlling direction of movements
Relative activity of many cortical neurons, controlling muscles each side of a joint, control the direction of movement.

Most axons from motor cortex synapse on interneurons, not α-motor neurons

Special role of motor cortex neurons which synapse directly on α-motor neurons
Exception for higher primates
Have a particularly direct, fast and powerful effect
Mostly for control of distal limb (hand & fingers)
Most developed in higher primates

Question 12

Claudia example

Answer 12

Think is not a good word as thinking about a movement does not necessarily cause movement
EMG activity in the muscle that is being used to operate the computerised motors in her arm
Brain is able to control what it thinks is the arm which is actually the chest muscle which is used to control the arm

(look at image in notes as well)

Question 13

neural systems controlling movement - hierachal organisation

Answer 13

Highest level = higher centers like association cortex and prefrontal cortex

middle level = sensorimotor cortex, thalamus, basal nuclei, brainstem, cerebellum

Local level = brainstem and spinal cord

Question 14

Flow chart of neural systems controlling movement

Answer 14

look at image in notes

Question 15

Sensorimotor cortex

Answer 15

Sensorimotor cortex = primary sensory and primary motor cortex are mixed together here

Question 16

Prefrontal cortex

Answer 16

Prefrontal cortex - form our intentions, make plans of what we want to achieve in the environment

Question 17

Loop where the motor programming occurs

Answer 17

Basal nuclei to thalamus to sensorimotor cortex loop is the loop where the motor programming is occurring

Keeps going around until this release a dose of dopamine to the system and the dopamine release at the substantia nigra confirms that the proposed way of moving the body is actually going to be successful and at this point the inhibition is removed from the motor cortex and the motor neurons can then send output down the corticospinal pathway down to inter neurons and motor neurons directly to control muscle. So we have this planning stage where the information is going around and around a loop from the level of our intention down into deeper regions that are for programming and established programmes of muscle and the motor cortex then thinks it is an okay signal for the motor cortex to send out as an output to actually carry out that activity

Question 18

Roles of the basal ganglia

Answer 18

Basal ganglia monitors and helps plan cortical activity involved in movement
Helps cortex select combinations/sequences of muscle activation
Cycle through loop (cortex – basal ganglia – cortex) occurs several times during preparation for movement

Positive feedback (withdrawal of inhibition) to cortex for selected motor output pathways
Positive feedback in the form of dopamine released from the substantial nigra and once this occurs and the motor cortex is no longer prevented from giving output down the spinal cord and into the muscles then we need this in order to start doing things 

Needed for initiation of movements

Dopamine input [from substantia nigra] vital to allow proper functioning
Death of dopamine neurons produces Parkinson’s disease

Question 19

Death of dopamine neurons produces

Answer 19

parkinsons disease

Question 20

parkinsons disease

Answer 20

Difficulty beginning movements, slowed movements, tremor
Cause uncertain, genetic + environmental, trauma

Treatments:
Dopamine replacing drugs (precursors for dopamine, taken up and released by surviving substantia nigra cells),
Deep Brain Stimulation
and (possibly) transplantation of dopamine cells

Question 21

Cerebellum flow chart

Answer 21

look at notes

Question 22

Loop of the cerebellum

Answer 22

Feedback loop where information is going back and forward and round and round, when we are forming a motor programme to design some muscle action which eventually gets given the ok signal from the substantial nigra in the basal ganglia through dopamine release to come out from the spinal cord and motor cortex we have to incorporate that into the motor programming where the body is to start with

Question 23

Cerebellum circuitry

Answer 23

Basic circuit repeated millions of times
Resembles a massive “parallel processor”
Job is to compare one thing to another, compares what is actually happening to what the plans were

Question 24

Roles of the cerebellum

Answer 24

Cerebellum helps plan, execute, and learn motor programs
Integrates sensory information with planned motor programs
Organizes timing of individual muscle contractions around joints
Compares the intended result of a planned movement with the actual result, and modifies ongoing activity, for smooth and accurate motor control

May also be used by other brain systems
[cognition, episodic memory, reading, emotion, dyslexia, schizophrenia, autism]

Question 25

Cerebellar injury

Answer 25

= DRUNKEN GAIT
Cerebellar injury results in movements that are slow and uncoordinated. Individuals with cerebellar lesions tend to sway and stagger when walking (‘drunken gait’).

Damage to the cerebellum can lead to:

1) loss of coordination of motor movement (asynergia),
2) the inability to judge distance and when to stop (dysmetria),
3) the inability to perform rapid alternating movement (adiadochokinesia),
4) movement tremors (intention tremor),
5) staggering, wide based walking (ataxic gait),
6) tendency toward falling,
7) weak muscles (hypotonia),
8) slurred speech (ataxic dysarthria), and
9) abnormal eye movements (nystagmus).

Question 26

Alcohol and cerebellum

Answer 26

Alcohol affects the cerebellum so drunk people often have problems with motor control
Chronic alcoholism will lead to degeneration of the cerebellum because of the long term messing with the GABA receptors