Depolarization causes:
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)
Vasogenic edema
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
Cytotoxic edema
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
Treatment If swelling is due to cytotoxicity
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!!
Clinical hallmarks of Increased ICP:
Headache
Vomiting
Papilledema – swelling of the optic discs
Neo-spinothalamic tract
Fast sharp pain fibers
Paleo-spinothalamic tract
slow, chronic pain fibers… dull ache
Signs of lower motor neuron lesions
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
Signs of Upper Motor Neuron Lesions (UMNL)
- Paralysis or weakness of movements of the affected side
- Babinski sign is present: The great toe becomes dorsiflexed and the other toes fan outward
- Loss of fine-skilled voluntary movements especially at the distal end of the
limbs. - Superficial abdominal reflexes and cremasteric reflex are absent.
- Spasticity or hypertonicity of the muscles.
- Clasp-knife reaction: initial higher resistance to movement is followed by a lesser resistance
- Exaggerated deep tendon reflexes and clonus may be present.
