On route towards the muscles

Question 1

Function of medial and lateral vestibular spinal tracts:

Answer 1

• Medial: head position by reflex actions of neck muscles
• Lateral: anti-gravity muscle activation at proximal muscles of the limbs

Question 2

What is the reticulospinal tract involved in?

Answer 2

• Cardiovascular & respiratory control
• Sensorimotor reflexes
• Coordination of eyemovement
• Regulation of sleep and wakefulness
• Temporal & spatial coordinations of limb and trunk muscles in rhythmic stereotypical behaviours such as locomotion

Question 3

What do the lateral,medial vestibular spinal tract and reticulospinal tract have in common?

Answer 3

• Both get feedback from vestibular systems
• Both stabilize posture by feedforward adjustments

Question 4

Name the spinal parts by name from top to bottom:

Answer 4

Cervical - thoraric - lumbar - sacral

Question 5

Where in the spinal cord are motor neurons located?

Answer 5

Ventral horn

Question 6

What is the difference in postural control of the lower motor neurons between the upper motor neurons in the cerebral cortex and in the brainstem?

Answer 6

• Upper motor neurons in the cerebral cortex signals to the lower motor neurons in the lateral ventral horn via the lateral white matter of the spinal cord to control distal muscles for skilled movement
• Those from the brainstem signal to lower motor neurons in the medial ventral horn to control proximal and axial limb muscles for posture, balance and locomotion

Question 7

What are the characteristics of medial local circuit neurons?

Answer 7

• long distance
• Project to many spinal cord segments
• Bilateral
• Postural control
• Rhythemic movements upper and lower limbs
• Maintenance of balance

Question 8

What are the characteristics of lateral local circuit neurons?

Answer 8

• Short distance
• Project to a few spinal cord segments
• Ipsilateral
• Execution of skilled behaviour

Question 9

What does novichok do?

Answer 9

• Blocks acetylcholine esterase with organophosphates –> aCh can not be broken down

Question 10

What is Myasthenia Gravis?

Answer 10

Autoimmune disease where nACh receptors on the muscle are attacked –> causes less APs

Question 11

What kind of motor units are there and what kind of action matches with it?

Answer 11

• Slow motor units, e.g. Standing
• Fast fatigable resistant motor units, e.g. run & walk
• Fast fatigable motor units, e.g. jumping

Question 12

Name the 2 types of motorneurons and their characteristics:

Answer 12

• Alpha motor neurons: for extrafusal and striated muscle fibers, generates forces needed for posture and movement
• Gamma motor neurons: for intrafusal muscle fibers, combined with sensory input that send information about the length of the muscle

Question 13

What do muscle spindles do?

Answer 13

Feedback system for reflex adjustment:
- Has sensory receptor output and gamma motor neuron input
- monitors and maintains muscle length
Via
- Group Ia afferent: phasic respons to small stretches
- Group II afferent: sustained fiber stretch

Question 14

What is a golgi tendon organ?

Answer 14

Its a negative feedback system that regulates muscle tension via Ib to inhibitory interneurons to protect the muscles

• Monitors and maintains muscle force

Question 15

What is the activity status of the Golgi tendon and spindles when contraction takes place?

Answer 15

Strong activity in golgi tendon, not that much in spindle

Question 16

What is the activity status of the Golgi tendon and spindles when stretch takes place?

Answer 16

Strong activity in spindle, not that much in golgi tendon

Question 17

How does feedback go from the spinal cord to the brain?

Answer 17

Via Clarke’s nucleus (lumbar) –> dorsal spinocerebellar tract (thoracic) –> cerebellum and dorsal column nuclei (cervical)

Question 18

How does feedback conveys itself through the brain?

Answer 18

Via the thalamus: feedback will reach the ventral posterior lateral and medial nucleus.
Then it can be processed in the somatic sensory cortex via postcentral sulcus

Question 19

What are central pattern generators?

Answer 19

Neural networks that produce rhythmic motor patterns without requiring sensory feedback or conscious control.
- Important for coordinating repetitive autonomic movements

(breathing, walking, chewing)