Human Physiology Chapter 12

Parasympathetic Division of the Nervous System

It is both dominant during “resting and digesting”, and its ganglia are on or near their target organs. The neurotransmitter is Acetylcholine (ACh)

Sympathetic System

Fight or flight:

• Increased heart rate

• Dilates pupils

• Dilates bronchi

• Decreases digestion

• Increases sweating

What is the Adrenal Medulla’s role to the Sympathetic branch of the Autonomic Nervous System?

It is a source of catecholamines, is considered a modified sympathetic ganglion, and releases epinephrine and norepinephrine directly into the blood. Epinephrine stimulates B2 adrenergic receptors in lungs.

Parasympathetic System

Rest and Digest:

• Slows heart

• Stimulates digestion

• Constricts pupils.

• Promotes urination.

• Increases secretions.

• Constricts bronchi.

Cholinergic Receptor (parasympathetic)

Receptor for parasympathetic neurotransmitters. Nicotinic and Muscaranic

Acetylcholine (ACh) (parasympathetic)

All autonomic preganglionic neurons (sympathetic and parasympathetic) release ACh.

The neural pathway from the spinal cord to the target tissue has two neurons: the preganglionic neuron and the postganglionic neuron.

This is true for both the sympathetic division and parasympathetic division.

Preganglionic Neuron

Starts in the brainstem or spinal cord and releases ACh in an autonomic ganglion.

• Sympathetic: Originates in the Thoracic and lumbar spinal cord

• Parasympathetic: Originate in the brainstem and sacral spinal cord.

Postganglionic Neuron

Stars in the autonomic ganglion and travels to the target organ, releasing a neurotransmitter.

Ganglia

Neuron cell bodies located outside the brain and spinal cord. They relay communication between the preganglionic neurons and the postganglionic neurons.

• Sympathetic: Ganglia stay close to the spine

• Parasympathetic: Ganglia stay close to the organs.

If the results of an experimental drug treatment included pupil dilation, high blood pressure, and high blood glucose, which conclusion would be indicated?

It acts on the alpha adrenergic receptors.

A patient was exposed to a nerve gas during a chemical warfare attack. The nerve gas inhibited the enzyme acetylcholinesterase. What will happen to the amount of acetylcholine in the synaptic cleft, and how can this be treated?

The amount of acetylcholine will decrease; treat with a cholinergic receptor antagonist.

Acetylcholinesterase (AChE)

Enzyme that breaks down acetylcholine (ACh)

Acetylcholine (ACh)

Neurotransmitter that neurons use to communicate with other neurons, muscles, or glands.

Synaptic Cleft

Gap between two communicating cells.

Adrenal Medulla