CNS Physiology

Question 1

Depolarization causes:

Answer 1

Na channels to activate (open), but it also causes inactivation in others
inactivated channels do not pass any ions (non-conducting state)
By contrast, K channels show activation but not inactivation
The fall in current at the end is deactivation (opposite of activation)

Question 2

Vasogenic edema

Answer 2

Occurs when the blood-brain barrier is upset:
Inflammation due to infection
Toxic agents that damage capillary endothelium
Abnormal capillaries associated with malignant neoplasm
Leakage of protein into interstitium

Question 3

Cytotoxic edema

Answer 3

Intracellular phenomenon
Hypoxia (Cardiac arrest, Near drowning, Strangulation)
Focal edema due to blockage of an end artery
Toxic substances that:
Impair sodium/potassium pump
Impair production of ATP

Question 4

Treatment If swelling is due to cytotoxicity

Answer 4

give I.V. bolus of a hypertonic solution such as mannitol to draw water into the vasculature and out of the brain
If vasogenic don’t do!!! would draw fluid into interstitial space and increase swelling!!

Question 5

Clinical hallmarks of Increased ICP:

Answer 5

Headache
Vomiting
Papilledema – swelling of the optic discs

Question 6

Neo-spinothalamic tract

Answer 6

Fast sharp pain fibers

Question 7

Paleo-spinothalamic tract

Answer 7

slow, chronic pain fibers… dull ache

Question 8

Signs of lower motor neuron lesions

Answer 8

Flaccid paralysis of muscles supplied
Atrophy of muscles supplied
Loss of reflexes of muscles supplied
Muscle fasciculations
Muscle fibrillation
Muscle contracture
Presence of muscle wasting
Reaction of degeneration to response to electrical stimulus

Question 9

Signs of Upper Motor Neuron Lesions (UMNL)

Answer 9

1. Paralysis or weakness of movements of the affected side
2. Babinski sign is present: The great toe becomes dorsiflexed and the other toes fan outward
3. Loss of fine-skilled voluntary movements especially at the distal end of the
   limbs.
4. Superficial abdominal reflexes and cremasteric reflex are absent.
5. Spasticity or hypertonicity of the muscles.
6. Clasp-knife reaction: initial higher resistance to movement is followed by a lesser resistance
7. Exaggerated deep tendon reflexes and clonus may be present.