Intro to Neurology

Question 1

What is the PNS divided into?

Answer 1

• Somatic PNS: controls motor and sensory function for the body wall e.g. skin (sensory neuron), skeletal muscles (motor neuron)
• Autonomic nervous system: has sympathetic and parasympathetic arms.

Question 2

what is the difference between afferent and efferent axons?

Answer 2

Afferent axons: arrives the CNS

Efferent axons: Exits the CNS

Question 3

what are interneurons?

Answer 3

CNS neurons that synapse with other neurons within the brain and spinal cord

Question 4

what are the dorsal and ventral roots that emerge from the spinal cord part of?

Answer 4

the PNS

Question 5

what are the afferent and efferent axons bundled into

Answer 5

They are bundled into fascicles surrounded by perineurium

Question 6

what is the whole nerve inside

Answer 6

the whole nerve is in a tough epineurium capsule.

Question 7

what is the blood brain barrier formed of

Answer 7

Astrocytes

Question 8

what is the function of microglia and oligodendrocytes

Answer 8

Microglia: act as immune cells
Oligodendrocytes: produce myelin sheath

Question 9

what is the way PNS regenerate?

Answer 9

Axons in PNS can regenerate after injury:

-injury leads to stimulation of phagocytes, which remove debris which would otherwise inhibit regrowth

Question 10

What causes neuropathic pain in the PNS?

Answer 10

May be compromised by aberrant axon sprouting and non-specific target reinnervation – can lead to neuropathic pain i.e. not very specific if you cut the nerve from your spinal cord to your toe, for the nerve to find its way back is quite hard, so you never get complete regeneration.

Question 11

Why do CNS have limited regenerative capacity?

Answer 11

• there are inhibitory molecules in the CNS but not in the PNS, Glia exert inhibitory influence on regeneration
• Glial scars form in place of injured brain tissue
• Absence of guidance cues that stimulate axon growth

Question 12

what are the 2 sensory pathways and what is a key difference?

Answer 12

Dorsal column-medial lemniscus pathway:
Conveys fine touch, vibration and two-point discrimination
Spinothalamic pathway:
Conveys pain and temperature sensation

the point at which they move from one side to another is the difference.
Dorsal column pathway- enters the spinal cord at the same side of the body and then goes to the brain-stem and then switches side.
BUT the spinothalamic pathway enters the spinal cord and immediately goes to the other side of the patient.

Question 13

what is the grey matter and white matter

Answer 13

grey matter- cell bodies of neurones
white matter- contains ascending sensory axon tracts from spinal cord to sensorimeter of the brain and descending motor axon tracts from the sensorimeter cortex of the brain to the spinal cord.

Question 14

what cells produce myelin sheath in the CNS and the PNS

Answer 14

Oligodendrocytes: CNS

Schwann cells : PNS

Question 15

what cells produce myelin sheath in the CNS and the PNS

Answer 15

Oligodendrocytes: CNS

Schwann cells : PNS

Question 16

What are the motor pathway types

Answer 16

Lateral corticospinal tract.
Motor pathways are an efferent pathway, so they come from the pregental gyrus (motor cortex) and then go down through the brainstem, which is where they jump to the other side of the nervous system and then go down the spinal cord. They send the signal down teh spinal cord on the (the same side the target cell is acting on), therefore if you injure that side of the system you will also injure that side of organs too.

Vestibulospinal tract:
receives input inside the ear. Creates microtwtiches to hold your balance.
-doesn’t cross sides, works on same side.

Question 17

what side does stroke effect?

Answer 17

Clinical syndrome.

Tends to cause problems on the other side of the brain (contralateral)

Question 18

What is upper motor neurone weakness and what is it caused by

Answer 18

Upper motor neurone and lower motor neurone.
Upper motor neurone:
Cerebral cortex to your spinal cord.
IF cord or brain is damaged you get upper motor neurone weakness.
Stroke, there flexing muscles in upper limb in stronger and it extenses a lot stronger in the leg which allows it to stay straight.

Question 19

What type of arteries can strokes affect and what does it cause?

Answer 19

Middle cerebral artery: most commonly affected-often results in weakness and loss of sensation on the other side (contralateral)
Posterior cerebral artery: strokes often affect occipital lobe-result in visual loss on the contralateral side
Anterior cerebral artery: strokes often cause contralateral leg weakness

Question 20

what does strokes in the brainstem affect?

Answer 20

-May cause problems with balance, eye movements, speech and swallowing, breathing.

Question 21

What is parkinsons disease and what are the main clinical features and what treatment is there

Answer 21

-slowly progressive degenerative disease affecting the basal ganglia.
-loss of neurones from the substantia nigra to the caudate and putamen ( basal ganglia)
Main clinical features:
-Rigidity ( stiffness)
- tremor ( shaking)
- bradykinesia ( reduced movement)

Neurotransmitter associated is dopamine
-treated with the precursor levodopa, which is used as dopamine does not cross the blood brain barrier but levodopa crosses the blood brain barrier and is converted to dopamine.

Question 22

Joe is a 72 year-old retired accountant. He has lost voluntary movement and sensation in his left arm, but the muscles still show reflex activity. His right arm and both legs function normally.

Answer 22

• Voluntary movement AND sensation lost but only LEFT arm. Legs fine.
• Injury must be to region(s) in RIGHT hemisphere containing both motor and sensory neurons/axons - but only from arm.
• Injury likely to be close to the sensorimotor cortex (in reality sensory and motor cortices, anatomically close but distinct) for the arm.
• Not peripheral nerve as reflex activity intact.
• Unlikely spinal cord as only ONE arm affected affected and legs fine.
• Cause - age 72- stroke?

Question 23

Sophie is a 19 year-old motorcyclist. She has lost voluntary movement and sensation in her left arm. The muscles do not show reflex activity. Her right arm and both legs function normally.

Answer 23

Voluntary movement AND sensation lost but only from one side - but NO reflex activity. (Legs fine)

• Likely to be a peripheral nerve injury to the left arm/shoulder since there is no reflex activity.
• Unlikely to be spinal cord as right arm fine
• Young motorcyclist - motorbike fall/accident?

Question 24

what is one spinal nerve surrounded by?

Answer 24

Epineurium