Question

As detailed as it can be describe what happened when the sympathetic or parasympathetic nervous systems are activated. Describe what happens to the body systems in each type of reaction.

Answer 1

Autonomic nervous system:

It consists of two antagonistic components- sympathetic and parasympathetic.

Sympathetic nervous system:

It is represented by the chain of 21 sympathetic ganglia on either side of the cord. It receives preganglionic sympathetic fibers from the spinal cord which makes it exit along with thoracic and lumbar nerves and constitute thoracolumbar outflow.

From the sympathetic ganglia arise postganglionic fibres which terminate on the viscera. Each sympathetic ganglion is connected to the spinal cord by white communicans and the spinal nerve by grey communicans.

Some preganglionic fibres pass through the sympathetic chain without synapsing and join to form splanchnic nerves emitting in some collateral ganglia. Postganglionic fibres are from the collateral ganglia supply digestive system and urogenital system.

Parasympathetic nervous system:

It consists of preganglionic parasympathetic fibres, parasympathetic ganglia and postganglionic parasympathetic fibres.

Preganglionic fibers make their exit along with the 3, 7, 9, 10 cranial nerves and 2, 3, 4 sacral nerves. Together they form the craniosacral outflow. The postganglionic fibres arise from these ganglions supply the viscera.

Neurotransmitter:

The neurotransmitter within the ganglion is acetylcholine for both sympathetic and parasympathetic nerves.

In the sympathetic system, the neurotransmitter at the terminal synapse is there adrenaline and noradrenaline, both of which have an effect opposite to that of acetylcholine. If the sympathetic nerve ending excites a particular organ, the parasympathetic inhibit it.

Antagonistic role of sympathetic and parasympathetic nervous system:

Organs	sympathetic stimulation	parasympathetic stimulation
Sweat glands	stimulates perspiration	-
Iris muscles	dilates pupil	constructs pupil
Digestive tract	slows down peristalsis	accelerates peristalsis
Heart	increased heart rate and contractility	decrease in heart rate and contractility
Bronchial muscles	widens air passage to facilitate breathing	narrows air passages, hindering brazing
Intestinal glands	decreases secretion of intestinal juice	promotes secretion of intestinal juice
Arrector pili	causes erection of hair	-
Gastric glands	inhibit secretion of gastric juice	stimulates the secretion of gastric juice
Pancreas	inhibits the secretion of pancreatic juice	stimulates the secretion of gastric juice
Salivary glands	inhibits the of saliva	stimulates the secretion of saliva
Liver	inhibits bile secretion, release of glucose	Promotes bile secretion, glycogen storage
Arteries	constricts arteries, raises blood pressure	dilates arteries, lowers blood pressure
Urinary bladder	relaxes urinary bladder	contracts urinary bladder, promotes urination