Chapter 10 - Autonomic and Somatic Nervous Systems

Visceral effectors

smooth muscle, cardiac muscle, and glands. They are associated with the viscera (internal organs) of the body.

Dual innervation

organs will receive nerves from both the parasympathetic and sympathetic nervous system. One branch increases activity, the other decreases activity of the organ.

Preganglionic neuron

cell body is in the brain or spinal cord. Its axon exits the CNS via a cranial or spinal nerve and then extends to an autonomic ganglion.

Autonomic ganglion

synaptic site where preganglionic neuron synapses with the postganglionic neuron

Postganglionic neuron

second neuron, lies entirely in the PNS. Its cell body is located in the autonomic ganglion, and its axon extends from the ganglion to the visceral effector.

Terminal ganglia

where parasympathetic preganglionic axons extend to postganglionic neurons located close to or within the wall of the visceral effector.

Sympathetic trunk

chain of ganglia located on either side of the spinal cord

collateral ganglia

individual ganglia that are no associated with the sympathetic trunk.

Chromatin cells

they are modified sympathetic postganglionic neurons that lack dendrites and axons. specialized cells in the adrenal medulla that preganglionic axons extend to. They also realize hormones into the blood.

Neuroeffector junction (NEJ)

synapse between an autonomic postganglionic neuron and a visceral effector.

Varicosities

swollen regions at the terminals of postganglionic neurons which contain synaptic vesicles with neurotransmitters.

Cholinergic neuron

release neurotransmitter acetylcholine

Cholinergic receptors

Integral membrane proteins in the postsynaptic plasma membrane which ACh binds to.

Acetylcholinesterase (AChE)

enzyme that degrades acetylcholine

Monoamine oxidase (MAO)

enzyme that inactivates norepinephrine

Autonomic tone

balance between parasympathetic and sympathetic activity. regulated by the hypothalamus

Autonomic (visceral) reflexes

fast, involuntary responses that occur when action potentials pass through an autonomic reflex arc. They play a key role in homeostasis by regulating cardiovascular activities, digestion, defecation, and urination.

Neuromuscular junction (NMJ)

synapse formed between a somatic motor neuron and a skeletal muscle fibre

Motor end plate

region of the muscle fibre plasma membrane opposite the synaptic end bulbs

Junctional folds

deep grooves in the motor end plate that provide a large surface area for ACh.

End plate potential (EPP)

depolarization caused by the net influx of NA+ into the muscle fibre through the nicotinic ACh receptors. Type of graded potential which forms at synapses.

Muscle action potential

depolarization caused by inflow of Na+ into the muscle fibre through open voltage-gated Na+ channels