Controlling movements and autonomic outputs-contributions of the brain

Question 1

Why do the cervical and lumbar regions of the spinal cord have larger ventral horns?

Answer 1

packed with mainly motor neurones innervating muscle
whereas the thoracic spinal cord has a smaller ventral horn because it only controls muscles of the trunk which are involved in less fine control

Question 2

What is the intermediate horn also called?

Answer 2

laminae 7- intermediolateral cell column

Question 3

What is the ventral horn also called?

Answer 3

laminae 9- motor nucleus

Question 4

What inputs do alpha motor neurones receive?

Answer 4

it is complex as they receive triple influences

• sensory inputs
• spinal interneurones
• descending tracts

Question 5

Why are interneurones so important ?

Answer 5

They are important for integrating information

Question 6

What is the high level of motor control hierarchy?

Answer 6

its function is strategy and the structures involved are association areas of neocortex and basal ganglia

Question 7

What is the middle level of motor control hierarchy?

Answer 7

its function is tactics and the structures involved are the motor cortex and cerebellum

Question 8

What is the low level of motor control hierarchy?

Answer 8

its function is execution and the structures involved are the brainstem and spinal cord

Question 9

What are the 2 major groups of descending pathways that enable communication between the brain and motoneurons in the spinal cord?

Answer 9

1) LATERAL PATHWAYS

2) VENTROMEDIAL PATHWAYS

Question 10

What are the lateral pathways like?

Answer 10

involved in voluntary movements of distal musculature
direct cortical control
fine control of distal musculature

Question 11

What are the ventromedial pathways like?

Answer 11

posture and locomotion
brainstem control
posture and balance

Question 12

What is meant by species differences in pathways ?

Answer 12

the location of pathways is different in different species, therefore it is important to consider this when using animal models
- in humans the corticospinal tract (important for dexterity) is present laterally whereas in rats/mice it is present in the dorsal column

Question 13

What are the impairments induced by corticospinal tract injuries?

Answer 13

the deterioration of motor impairments are dependent upon the extent of CST damage

Question 14

What occurred in a complete unilateral hemisection of the CST?

Answer 14

eliminated grip causing sever impairments in food retrieval by the forepaw ipsilateral to the lesion

Question 15

What does a hemisection mean ?

Answer 15

if the damage crosses onto the other side, damage will occur on both sides whereas hemisection is only on one side

Question 16

What can happen if not all pathways are damaged?

Answer 16

the pathways that remain may undergo plasticity and therefore slight recovery may occur

Question 17

How was it tested to see if the rubrospinal tract could compensate for CST loss?

Answer 17

they lesioned the pyramidal tract and then the dorsalateral funicular and compared motor function to animals that has lesions to both tracts simultaneously

Question 18

Can the rubrospinal tract compensate for CST loss?

Answer 18

it can only compensate for skilled reaching and there was only a degree of compensation

Question 19

How can recovery occur in incomplete injuries?

Answer 19

due to sprouting of undamaged fibres
- in mice there is little ipsilateral labeling initially however after 4 weeks the ipsilateral side started to be labelled
sprouting is important for recovering function

Question 20

How can forelimb and hindlimb movements be improved after CST damage?

Answer 20

stimualtion of spared CST fibres improves locomotor function- it suggested pathways are crossing and sending new pathways across to the impaired side to try and recover some function

Question 21

What is the link between the ventromedial (MLF) and corticospinal tracts onto single interneurones thought to be ?

Answer 21

thought there may be plasticity within the system because when recording from single interneurones in monkeys when they were reaching to grasp food
they expected CST simulation to cause the interneurone to fire but they were surprised that it also occurred when the ventromedial pathway was stimulated

Question 22

What happens to dextrous movements in macaque monkeys overtime?

Answer 22

1 day after the CST lesion there is a loss of ability to grasp a sugar cube= loss of dextrous activity
7 days after the CST lesion, there are improvements in grasping suggesting compensation has occurred

Question 23

What was determined about the reticulospinal pathway in terms of compensation?

Answer 23

7 days after a lesion, grasping was a struggle
whereas 4 weeks after the injury recovery of grasping action had occurred - this and the previous experiment indicate that the ventromedial pathways can compensate for the loss and therefore we should exploit this

Question 24

Why is the RVLM so important?

Answer 24

it has a major role in sympathetic control

• important for controlling BP
• injecting glutamate cases increases in bp, hr and sympathetic activity

also important in temperature regulation

Question 25

What is the role of the raphe nuclei?

Answer 25

if you inject NMDA or KA into it then it increases HR, BAT activity and expiration of carbon dioxide

Question 26

What are organs that are also very important for sympathetic control, particularly for SCI patients?

Answer 26

bladder, bowel and sex organs - there receive complex autonomic and motor control
- the bladder receives somatic, parasympathetic and sympathetic inputs

Question 27

What is the barrington’s nuclues?

Answer 27

it provides inputs to autonomic neurones innervating both bladder and colon
- injecting psuedorabies virus into bladder or colon and it goes back into spinal cord labelling SPNS into BN and LC

Question 28

What is important about the development of the descending pathways involved in bladder and bowel control?

Answer 28

when you are young you have no supra spinal control- sometimes in males this doesn’t develop until 7/8 years old

Question 29

What are the symptoms of autonomic dysfunction?

Answer 29

severe postural hypotension- loss of consciousness
incontinence
impotence