Brain systems (wk3)

Question 1

Subcortical control of movement
-Describe the basic layout of the subcortical motor system

Answer 1

-Copy diagram (10/10)

Question 2

Subcortical control of movement
-Spinal cord reflex e.g. stretch reflex

Answer 2

-Stretching a muscle is detected in the muscle and leads to increased activity in sensory neurones that in turn leads to an increase in activity of motor neurones that innervate the same muscles, while inhibiting the motor neurones that innervate antagonists

Question 3

Subcortical control of movement
-Reflexes

Answer 3

-Rapid automatic control of movement, little or no voluntary movement. -Complex -> swallowing, breathing
-Simple -> stretch reflex
-These happen in the spinal cord and lower brain stem

Question 4

Subcortical control of movement
-Name and describe the 2 brainstem nuclei groups

Answer 4

-Reticular formation -> Set of interconnected nuclei that are located throughout the brainstem
-Vestibular nuclei (VN) -> The nuclei are for the vestibular system and are located in the brainstem. They monitor motions and receive info from external stimuli

Question 5

Subcortical control of movement
-Vestibulospinal tract

Answer 5

-Sensory system that provides the sense of balance and spatial orientation for the purpose of coordinating movement with balance
-Combination of vestibular and visual information to be accurate in movements

Question 6

Subcortical control of movements
-Reticulospinal tract

Answer 6

-Set of interconnected nuclei that are located throughout the brainstem
-The tract originates in reticular formation. The tracts function in maintaining tone, balance and posture
-Before we lift a weight with our arm, muscles of the leg are excited to support our body posture. The postural control is via the fast-acting excitatory action of the reticulospinal tract
-The brain predicts postural consequences of planned movements and acts to prevent loss of balance
-Activity is happening through the nervous system predicting that a movement will happen to prepare the body appropriately – this is through forces to maintain stability -> causes rapid muscle contractions to maintain balance

Question 7

Subcortical control of movements
-Cerebellum

Answer 7

-Very conserved, highly folded structure in all animals. 10% volume of the brain
-More than neurones than cortex – 69 billion cells v 16 billion cells
-Input: output ratio 40:1. Information is sent to the pons via the cerebellum
-Receives and filters lots of information.

Question 8

Subcortical control of movements
-Input: Output of 40:1

Answer 8

-3 major pathways out of the cerebellum ->
1) Superior cerebella peduncle (efferent pathways to the red nucleus and the cortex via the superior colliculus)
2) Middle cerebella peduncle (input from sensory, visual, vestibular and motor systems)
3) Inferior cerebella peduncle (carries info to and from the spinal cord and vestibular nuclei)
-Middle -> where the largest input goes for most of the body. The red nucleus is where the information is filtered out.

Question 9

Subcortical control of movement
-Rubrospinal tract

Answer 9

-The red nucleus is a spherical collection of cell bodies in the midbrain
-The red nucleus receives a very large input from the cerebellum and from the primary motor cortex. Works in the lateral part of the body
-Rubrospinal fibres terminate primarily in the cervical and lumbar enlargements of the cord, which contain motor neurones for muscles in the fore- and hindlimbs, respectively
-Recording data indicate that the rubrospinal tract controls the shaping of the hand during reach-to-grasp movements.

Question 10

Subcortical control of movement
-Basal ganglia

Answer 10

-Movement regulation, reward system, skill learning, selection of appropriate behaviours
-It controls movement via the cortex
-There are 2 pathways: the direct and the indirect pathway. Direct (go) -> runs through basal ganglia / Indirect (no-go)-> Longer loops through the basal ganglia. Direct -> has excitatory effect on cortex and net-effect is pro-movement/kinetic
-Indirect -> Stimulation has inhibitory effect on cortex and net-effect is anti-movement
-Reduced excitation = less movement.

Question 11

Subcortical control of movement
-Basal ganglia and cerebellum

Answer 11

-Damage to the BG produces states where there is too much or too little movement (seen in Parkinson’s disease)
-Damage to the cerebellum produces states where movements can still be made, but they are uncoordinated.

Question 12

Cortical control of movement
-Cerebral cortex

Answer 12

-Main focus on sections 4,6 and 8 for motor function

Question 13

Cortical control of movement
-Description of the motor areas in the cortex

Answer 13

-The three main cortical motor regions can be identified because:
1) Neurones increase their firing rates before movements and specific features of this activity are often closely related to specific movement features
2) Neurones send their axons to terminate in motor centres in the brainstem and spinal cord
3) Electrical stimulation in these areas elicits movements
4) Neurones send their axons to connect most densely with other motor areas

Question 14

Cortical control of movement
-Primary motor cortex

Answer 14

-Basic parameters of movements e.g. force, direction, extent, speed
-Neurones fire around 5 to 100ms before movement onset and can code for the basic parameters of movement.

Question 15

Cortical control of movement
-Frontal cortex (non-primary motor cortex)

Answer 15

-Neurones in the non-primary motor cortex have a more complex relationship to movement
-They code for the more complex aspects of movement.

Question 16

Cortical control of movement
-Pre-motor cortex (orange area 6)

Answer 16

-They code for the more complex aspects of movement, for example; planning movement, spatial guidance of movement and sensory guidance of movement

Question 17

Cortical control of movement
-Supplementary motor cortex (SMA; purple 6)

Answer 17

-They code for more complex aspects of movement e.g. coordinating temporal sequences of actions, bimanual coordination and initiation of internally generate (as opposed to stimulus driven) movement

Question 18

Cortical control of movement
-Supplementary motor area (SMA): Bimanual coordination monkey task

Answer 18

-A monkey is trained to perform a complex bimanual task that involves the animal pushing a peanut through a hole to collect the peanut
-After a lesion of the SMA, the animal cannot perform the task and will never recover the function.

Question 19

Areas closely associated with movement
-Identify the areas needed for complex movements and are highly interconnected with the motor areas:

Answer 19

-Primary sensory cortex (areas 1,2, and 3)
-Posterior parietal cortex (areas 5 and 7)
-Corticospinal tract

Question 20

Areas closely associated with movement
-Primary sensory cortex (areas 1,2 and 3)

Answer 20

-Touch; vibration, heat, pain and pressure
-Proprioception; afferent info, including joint position sense (the ability to recognise joint position in space), kinaesthesia (the ability to appreciate/recognize joint movement or motion) and sensation of resistance (the ability to appreciate and recognize force generated within a joint)

Question 21

Areas closely associated with movement
-Posterior parietal cortex (areas 5 and 7)

Answer 21

-Integration of sensory and visual information to execute complex movement in the environment, representations for different motor effects and a command apparatus for operation of the limbs, hands and eyes within immediate extra personal space

Question 22

Areas closely associated with movement
-Corticospinal tract

Answer 22

-The most important tract in the human for precise control of the limbs
-Origin: Primary motor cortex (30%), premotor, supplementary (30%) and somatosensory, parietal, cingulate (40%)
-There are around 1 million fibres in humans, 90% cross at lower medulla and are all excitatory.

Question 23

Areas closely associated with movement
-Describe what ‘increasing complexity’ refers too:

Answer 23

-The complexity of the movements in the nervous system, controls increase as your move towards the brain
-A ‘hierarchy’ of function regarding movements and reflexes;
* Spinal cord – simple reflexes
* Medulla – complex reflexes
* Cerebellum – coordinated movement
* Basal ganglia – programmed movements
* Cortex – complex conscious movements