Pt 5: Nerves and Muscles at Work

Motor unit

one a-motor neuron plus all of the skeletal muscle fibers it innervates

How are neurotransmitters removes from the synaptic cleft

enzymatic degradation (acetylcholinesterase for acetylcholine, MAO and COMT for norepi/epi/dopamine/serotonin) or reuptake

Alpha 1 receptors

Gq, vasoconstriction, vascular smooth muscle

Alpha 2 receptors

Gi, inhibits norepinephrine, sedation, vascular smooth muscle

B1 receptors

Gs, increase heart rate and contractility, increase renin

Beta 2 receptors

Gs proteins, vasodilation in skeletal muscle

Voltage-dependent gating of two ion channels that make action potential in neurons

Voltage-gated Na channels open fast to make the graph go up, K channels slowly return it to normal

Axon diameter and myelination

Large diameter and more myelination increase the action potential speed

What activates adrenergic receptors

epinephrine and norepinephrine are catecholamines made from tyrosine