Physiology of muscle contraction

The motor unit consists of:

a motor neuron and muscle cells

Define the trigger zone of a motor neuron:

sensitive part of an axon (axonal hillock) where an action potential is generated

Define the middle portion of the axon of a motor neuron:

It is either an influx or efflux of ions

If the middle portion of the axon is an Influx:

sodium ions depolarize axons

If the middle portion of an axon is an Efflux:

potassium ions repolarizes the axon

Define the terminal axon of a motor neuron

contains synaptic knobs and is the site of release of vesicles into synaptic cleft (requiring calcium)

Sodium in;

energy on

Potassium out;

resetting/ repolarizing

Define sarcolemma receptors:

a neurotransmitter (ACh) binds to the (nicotinic) receptors (stimulatory)

The skeletal muscle nicotinic receptors do what:

bind neurotransmitter (ACh) and sends excitatory electrical impulse into the muscle cell

The cardiac muscle Beta 1 receptors do what:

Increase heart rate and bind epinephrine and norepinephrine

The smooth muscle Beta Receptors do what:

generally, dilate (relax) smooth muscle

The smooth muscle Alpha Receptors do what:

Generally, constrict smooth muscle

Alpha=

constrict

Beta=

dilate

Heart is #1=

Beta 1 receptor

What is the most common NT in the body and the most common NT in skeletal muscle actions?

Acetylcholine (ACh)

The neuromuscular junction=

NMJ

Define the neuromuscular junction:

gap between the nerve and muscle cell

What occurs at the neuromuscular junction

NTs are released (calcium is needed); broken down; and some may have reuptake

Define Synaptic vesicles:

they contain NTs and release NTs into the synaptic cleft

An influx of Na+ in the NMJ:

depolarizes the nerve and muscle cell

An influx of Ca++ in the NMJ:

will release NT from the nerve cell: calcium will close sodium channels in the nerve cell

Calcium is needed to turn off neuron

true

Adreniline:

fight or flight

Define the synaptic cleft:

area of NT release: decomposition; and reuptake