Question

Describe the anatomy and function of the ANS. Also, discuss one disorder of the ANS and possible treatments.

Answer 1

Antomy of Autonomic nervous system:-

It lies almost entirely outside of the central nervous system.

It consists of two main parts:

1) Craniosacral part (parasympathetic),

2) Thoracolumbar part (sympathetic).

These are sometimes thought of as being opposite to each other, ultimately striking a balance within the body.

✓The (Craniosacral part) parasympathetic :- It is associated with relaxation, digestion, and generally taking it easy.

✓ The (Thoracolumbar part) sympathetic:- It is responsible for the "fight or flight" response.

*In the autonomic nervous system, almost without exception, the nerves synapse in a clump of nerves called a ganglion before the message is transmitted to the target organ, such as a salivary gland. This will allows for another level of communication and control.

Functions:-

As the autonomic nervous system is divided into two parts, its function are depend upon which part of the system you are looking at.

1) Parasympathetic nervous system:-

Mostly the nerves of the parasympathetic nervous system begin in the nuclei in your brainstem. From there, they travel through cranial nerves (such as the vagus nerve), which slows the heart rate, or (the oculomotor nerve), which constricts the pupil of the eye. Parasympathetic are what causes your eyes to tear and your mouth to salivate. Other parasympathetic terminate in the walls of thoracic and abdominal organs like the esophagus, gastrointestinal tract, pharynx, heart, pancreas, gallbladder, kidney, and ureter.

The sacral parasympathetic synapse in ganglia in the walls of the colon, bladder, and other pelvic organs.

2) Sympathetic nervous system:-

The Sympathetic fibers of the autonomic nervous system exit the lateral part of spinal cord where they receive information from parts of the brain such as the brainstem and hypothalamus. Fibers run from synapses in ganglia just outside the spinal column to their targets, usually along blood vessels.

For example, the sympathetic nerves that dilate your eyes in response to darkness or a threat exit the spinal cord in your neck and synapse in the ganglion called the superior sympathetic ganglion, they then run along the carotid artery to the face and eye. These supply nerves to the abdominal and pelvic visceral organs, as well as the hair follicles, sweat glands etc.

Neurotransmitters of Autonomic nervous system:-

The neurotransmitters such as acetylcholine and norepinephrine are primarily responsible for communication in autonomic nervous system.

Acetylcholine is released at the level of the ganglia for both parasympathetic and sympathetic parts of the autonomic nervous system.

In the parasympathetic nervous system, postganglionic receptors in organs such as the gastrointestinal tract are called muscarinic and are susceptible to drugs such as atropine.

The post-ganglionic sympathetic neurons only release norepinephrine, with the exception of sweat glands and some smooth muscle on blood vessels, in which acetylcholine is used.

The norepinephrine released by the post-ganglionic neurons hit a group of receptors called the adrenergic family of receptors.

There are two main categories of adrenergic receptors:-

Alpha and Beta, each of which has subcategories with their own unique properties and can be manipulated by different types of medications.

The control of blood pressure:-

When sympathetic nervous system dominates, the heart pumps hard and quickly, the peripheral blood vessels are narrow and tight, and your blood pressure will be raised.

But, when the parasympathetic system dominates, it slows the heart and opens peripheral blood vessels, causing decrease in blood pressure.

The control of Autonomic nervous system:-

*Cortex of brain, normally associated with conscious thought.

*In cerebrum, the insula, anterior cingulate cortex, substantia innominata, amygdala and ventromedial prefrontal cortex communicate with the hypothalamus to impact your autonomic nervous system.

*In brainstem, the Nucleus tractus solitarius(NTS) is the main command center for the autonomic nervous system.

Disorder:-

Orthostatic hypotension:- It is a type of orthostatic intolerance.

It occurs when your blood pressure drops significantly as you stand up. This can result in lightheadedness, fainting, and heart palpitations. Injury to nerves from diabetes, Parkinson’s disease etc. can cause episodes of orthostatic hypotension due to autonomic dysfunction.

Treatment of Orthostatic hypotension:-

It can be helped by lifestyle changes and prescription medication.

The symptoms of orthostatic hypotension may be relieved by:-

✓Elevating the head of your bed.

✓Drinking plenty of fluids.

✓Adding salt to your diet.

✓Changing positions slowly.

✓Taking medications like midodrine.

✓Wearing compression stockings to prevent blood pooling in your legs