Control of movement

Question 1

what is a neuromuscular junction?

Answer 1

A synapse between a motor neuron and a msucle fibre

Question 2

what ar ethe 5 steps of a nuromuscular junction?

Answer 2

1. AP in motor neuron
2. resease of Ach
3. EPSP in muscle fibre (endplate potential)
4. AP in muscle fibre
5. Contraction (twitch) occurs

Question 3

what are muscle spindals?

Answer 3

• Fibrous capsules containing specialised muscle fibres
  
  • Detects change in muscle length
    ○ Contracts of spindles to keep axons within their working range
    ○ How quickly it is happening (is detected)
    ○ Keeps length under control
  • Contracts of spindle poles to keep 1a axons within working range
  • Fire rapid impulses to protect you
  • E.g.: rolling ankle- requires quick impulses to protect the ankle from over stretching
    → muscle contraction

Question 4

what are golgitendon organs?

Answer 4

• Located at the junction of muscle and tendon
  
  • Tendon= when the muscle joins the bone.
  • Innervated 1b sensory axons
  • Monitors muscle tension (tendon stretch)
    ○ How much tension is the muscle under
    →muscle inhibition- protective mechanism to avoid the use of the injured joint

Question 5

what are monosynaptic reflexes?

Answer 5

• Only uses one synapse
  
  • Uses reflex arc
  • Patellar tendon= most common (stretch reflex)
    
    1. Activation of a receptor (in quads)
    2. Activation of a sensory afferent neuron
    3. Integrating centre and information processing (only in the cell body of the post synaptic cell- motor neuron)
    4. Activation of a motor or efferent neuron
       Response by the effector neuron (causes kicking neuron)

Question 6

what is a polysynaptic reflex?

Answer 6

• Uses 2 or more synapses
  
  • Withdrawal reflex (touching something hot with hand)
    ○ At spinal cord (so it is quick)
    ○ Signal is sent to brain to prevent pain and aid correctly
  • Uses reflex arc (has modifications)
    
    1. Receptor
    2. Afferent neuron (synapses with the interneuron)
    3. Interneuron (sends impulse to the bicep to contract and move the hand away)
    4. Efferent neuron
    5. Effector
       Inhibitory neuron (sends impulse to triceps to ensure it doesn’t contract to lengthen arm)

Question 7

what are reflexes and why are they important?

Answer 7

• muscular movements
• they control human breathing, movements and other functions vital to life

Question 8

what are the cortical movements involved in the control of movement?

Answer 8

• The primary motor cortex (M1)
• Parts of Frontal association cortex:
  ○ Supplementary motor area (SMA)
  Premotor cortex (PMA)

Question 9

what is the primary motor cortex?

Answer 9

primary commander for movement

Question 10

why is the primory motor cortex important?

Answer 10

involved in the execution of movement

Question 11

how is the primary motor cortex organised?

Answer 11

• somatotopically: motor homunculus
  ○ Disproportional amount of cortical area needed for our hands and mouths as they do more complex movements.
• Each part of the body is located with a specific region of the primary motor cortex.

Question 12

where is the primary motor cortex located?

Answer 12

at the back of the frontal lobe

Question 13

what are the inputs for the primary motor cortex?

Answer 13

• Frontal association cortex
• Primary somatosensory cortex (S1)
  ○ S1 neurons in particular location send info to primary motor cortex area responsible for muscles in that body part
  ○ Rapid feedback to the motor system.

Question 14

what is the function of the primary motor cortex?

Answer 14

to generate signals to execute movement in a specific region of the body

Question 15

what is the supplementary motor area?

Answer 15

• Learning and planning of behaviours consisting of sequences of movements
  ○ E.g.: dancing
• Damage disrupts ability to execute well-learned sequences of responses
• Pre-SMA is associated with the (perception of) control of spontaneous movement
• Stimulation of SMA and Pre-SMA provokes the urge to make a movement or the anticipation that a movement will occur

Question 16

what is the premotor cortex involved in?

Answer 16

• learnign and executing of complex movements
• guided by sensory information
• contains mirror neurons

Question 17

what are mirror neurons?

Answer 17

• Motor command neurons: In front of brain (frontal lobe)
  ○ Neurons fire if someone preforms a specific action
  ○ Fire when someone does something Infront of us
• Imitation of an act (requires brain to adopt other person’s point of view)
• Depends on culture and civilisation
  ○ Sudden emergence of evolutionary brain system
  § Spread vertically and horizontally across people and generations.
• Mirror neurons of touch: empathises if someone else is being touched (and if we are being touched)
  ○ Don’t feel touch sensation due to touch and pain receptors relaying to brain to tell us we aren’t being touched.
• If arm is numbed and has no feeling- others touch is in your consciousness (joined by neurons)- believe you are being touched.
• Imitations and immolations.

Question 18

what is the basal ganglia?

Answer 18

• part of the tenecephalon
• important for the control of voluntary movement

Question 19

whci part of the basal ganglia recieves the input?

Answer 19

the striatal nuclei

Question 20

what does the striatal nuclei recieve input about?

Answer 20

• primary motor cortex
• primary somatosensory cortex
• substantia nigra
• • other cortices

Question 21

where is the output information from the basal ganglia recieved?

Answer 21

• primary motor cortex
• supplementary motor cortex
• premotor cortex
• motor nuclei of the brainstem

Question 22

what is huntington’s disease?

Answer 22

• Hereditary (passed on) disease caused by degeneration of the striatal neurons
  ○ Loss of inhibition exerted on globus pallidus (middle of the lentiform nucleus in the brain)
  ○ A cluster of neurons in the basal ganglia

Question 23

what are the symptoms of huntington’s disease?

Answer 23

• Uncontrollable jerky limb movements
• Impaired ability to cease movements
• Cognitive and emotional change
  Slow processing
  Difficulty in learning new information
  Hard to pick up on others’ emotions
  Depression/lack of emotion

Question 24

between what ages are people ususally diagnosed with huntingtons disease?

Answer 24

30-50 years old

Question 25

what is mutant huntington protein?

Answer 25

causes neurons to die prematurely- causing huntingtons.

Question 26

what is the cerebellum?

Answer 26

part of the metencephalon
“little brain”

Question 27

how many hemispheres does the cerebellum control?

Answer 27

2

Question 28

how does the cerebellum function?

Answer 28

ipsilaterally- affects the same side of the body

Question 29

how is the cerebellum connexted to the brainstem?

Answer 29

via the cerebellar peduncles

Question 30

what percentage of brain neurons does the cerebellum accunt for?

Answer 30

50%

Question 31

what is the function of the cerebellum?

Answer 31

• Involved in motor control functions
• Smooths and integrates ongoing movement
• Important for independent rapid skilled limb movements
• Important for postural reflexes
• Integrates movement sequences
• Partly responsible for motor learning

Question 32

what inputs information to the cerebllum?

Answer 32

• vestibular, auditory and visual systems
• motor and somatpsensory cortices

Question 33

where does the cerebellum output its information to?

Answer 33

every major motor brain structure

Question 34

what happens to an individual if they have a dmagaed cerebellum?

Answer 34

• Cerebellar Ataxia = lack of coordination of movements
  ○ Can manifest as difficulty walking, particularly with narrow base (one foot in front of the other)

Question 35

what are the possible causes of a damaged cerebllum?

Answer 35

stroke, haemorrhage, alcoholism, tumour, physical trauma, chronic degenerative conditions

Question 36

what is an intention tremor?

Answer 36

• involuntary, rhythmic muscle contractions (oscillations) that occur during a purposeful, voluntary movement.
  ○ slow tremor of the extremities that occurs at the end of a purposeful movement (e.g., touching a finger to the tip of nose)
  ○ Jerky, poorly coordinated, exaggerated movements

Question 37

what is reticulr formation?

Answer 37

includes a large number of nuclei in the brainstem (midbrain, pons and medulla oblongata)

Question 38

what is reticular formation importnat for?

Answer 38

• a variety of motor functions:
  ○ Regulates muscle tone (via gamma motor neurons)
  ○ Controls (semi)automatic responses (e.g. respiration, coughing, vomiting)
  ○ Controls posture
  ○ Plays a role in locomotion- ability to move from one place to another

Question 39

what are the two major descending motor pathways/ tracts?

Answer 39

• lateranl pathways
• ventromedial pathways

Question 40

what do lateral pathways control?

Answer 40

voluntary independent movement of distal muscles
(e.g.: forearm, hand, finger)

Question 41

where do lateral pathways originate?

Answer 41

in the cortex

Question 42

how many tracts are lateral pathways composed of and what do they control?

Answer 42

3 tracts:
1. Lateral corticospinal
lower leg and foot
2. Corticobulbar
Face, neck, eye, tongue
3. Rubrospinal
Fore arm, hands (independent from trunk movement)

Question 43

where do ventromedial pathways originate?

Answer 43

in the brain stem

Question 44

what does the ventromedial pathathways control?

Answer 44

automatic movements of proximal and axial muscles (e.g. movements related to posture and locomotion)

Question 45

how many tracts is the ventromedial pathway composed of?

Answer 45

4

Question 46

what are the 4 tracts of the ventromedial pathway?

Answer 46

1. Ventral corticospinal tract- involved in controlling proximal muscles, like those of the trunk
2. Vestibulospinal tract- maintain equilibratory reflexes from the input of the vestibular apparatus
3. Tectospinal tract- involved in orienting the eyes and the head towards sounds as part of the auditory and visual reflex
4. Reticulospinal tract- descending tract present in the white matter of the spinal cord, originating in the reticular formation

Question 47

What structures send sensory feedback to motor neurons?

Answer 47

muscle spindles

Question 48

Give an example of a monosynaptic reflex:

Answer 48

patella tendon reflex

Question 49

What body parts havs a larger area dictated to it as part of somatotopic organisation?

Answer 49

lips, hands (fingers) and feet (toes)

Question 50

What are mirror neurons are thought to be involved it?

Answer 50

contagious yawning

Question 51

What connects the cerebellum to the brainstem?

Answer 51

cerebellar peduncles

Question 52

A man attends a clinic with a series of symptoms. Which of his symptoms cannot be explained by damage to his cerebellum?

Answer 52

difficulty yawning