Unit 2.5 - Autonomic Nervous System

Autonomic Nervous System

Usually involuntary.

Controls smooth and cardiac muscle, secretory cells, glands, and some adipose tissue.

Ganglia

Synaptic junction between preganglionic and postganglionic neurons.

More than a collection of axon terminals and cell bodies.

Modulate autonomic signals to effectors.

Sympathetic Ganglia

2 major types: trunk and prevertebral ganglia.

Usually has short preganglionic neurons and long postganglionic neurons.

Parasympathetic Ganglia

Preganglionic axons synapse with poCstganglionic neurons in intramural ganglia.

Cholinergic Neurons

Neurons that release the acetylcholine (ACh).

Includes: all preganglionic neurons, all parasympathetic postganglionic neurons, and sympathetic postganglionic neurons that affect sweat glands

Cholinergic Receptors

Two main types which bind ACh: nicotinic and muscarinic receptors.

Nicotinic Receptors

Present in the plasma membranes of dendrites and cell bodies of postganglionic neurons.

Muscarinic Receptors

Present in the plasma membranes of effectors controled by parasympathetic postganglionic axons.

Adrenergic Receptors

Most sympathetic postganglionic neurons are adrenergic neurons.

Release norepinephrine (NE) as the neurotransmitter.

Can cause either excitation or inhibition.

Both epinephrine (hormone) and norepinephrine (hormone or neurotransmitter) can bind to andrenergic receptors.

α1 and β1 receptors provoke excitation response.

α2 and β2 receptors produce inhibition response.

β3 receptors produce thermogenesis respones.

Neuroeffector Junction

The area where between a postganglionic autonomic neuron and its target cell.

Autonomic Tone

Regulated by the hypothalamus that turns up the sympathetic tone while turning down the parasympathetic tone and vice versa.