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Unformatted text preview: in myelin as in unmyelin. the V-GATED sodium channels are concentrated in node of ranvier. the Vgated potassium channel are in paranodal region (next to the node). in internode there's no ion
channel. when you depolarize, sodium open, AP move down. current don't leak out because multiple layers of myelin sheath increase resistance of axon and lower capacitance (can't store charge
because 2 conducting element (ecf and icf) are very far as oppose to close together (very little charge is store in that area). Internodal concentrate the current to nodal area, generate a new AP (jumps
node to node).
-in myelinated axon, especially big one, big axon+thick myelin sheath, can conduct much more efficiently than biggest of unmyelinated axon. Myelinated Axons: Saltatory Conduction Node of Ranvier Internode Channelopathies Incomplete inactivation of
Na+ channel Na+ Channels
• Hyperkalemic periodic paralysis
• Forms of epilepsy Ca2+ Channels muscle weakness Autoimmune destruction
of presynaptic Ca+2 channels
kidney disease. hypokalemic (normally high potassium will depolarize,
raising extracellular potassium depolarize (make Ek positive, see nerst
equation) the heart and kill people with the lethal injection) depolarization
should lead to activation and inactivation. inactivation part is deficient,
prolong activation of muscle cell lead to paralysis • Lambert-Eaton myasthenic syndrome
• Hypokalemic periodic paralysis
• Malignant hyperthermia K+ Channels receptor (Ca+2 release
channel in SR) nurse:
calcium is release from ER. these ER muscle cell called SR. v-gated calcium
channel stimulate muscle contraction. here, excess calcium ion b/c channel
open but don't close. muscle contracts too long, body temperature go up. • Long Q-T syndrome (most types) Cl- Channels
• Myotonia congenita
• Cystic fibrosis
Defective CFTR skeletal muscle have high resting cloride potential.
but here the refractory period is too much (Cl- channel)...
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This document was uploaded on 03/09/2014 for the course EXSC 301 at USC.
- Spring '09