What is the Types or Divisions of Autonomic Nerves

Autonomic nerves are divided into 2, namely sympathetic and parasympathetic nerves that act on the visceral organs with opposite effects. Sympathetic and parasympathetic nerves work on the same organ but provide inhibition or exhibition. This trait is referred to as dual innervation , which is a way of working that is intended to achieve a balance (homeostasis).

1. Parasympathetic nerves

also called the “resting and digesting system” which functions to ensure the body uses a minimum of body energy. At the time of eating, the parasympathetic nerves will cause the process of digestion and cause relaxation of the body marked by a decrease in blood pressure and a slowing pulse. As previously described, the location of the parasympathetic nerves is of craniosacral origin. The following are the pathways of the parasympathetic cranial nerves:

a. Oculomotor (III) nerve;

Preganglionic neurons originate from the mesencephalon and go to the ciliary ganglion and preganglionic neurons will innervate smooth muscle in the pupil which causes constriction of the sphincter pupillary muscle and stimulates the ciliary muscle for accommodation.

b. Facial Nerve (VII);

Preganglionic neurons originate from the pons (superior salivarius nucleus) to the pterygopalatine ganglion and submandibular ganglion which stimulate the nasal, lacrimal, submandibular and sublingual glands.

c. Glossopharyngeal nerve (IX);

Preganglionic neurons originate from the medulla oblongata (inferior salivarius nucleus) to the otic ganglion to activate the parotid gland.

d. Vagus Nerve (X);

The vagus nerve has a parasympathetic role in the human body about 90%. The vagus nerve will innervate the organs in the thorax and abdomen. Preganglionic neurons originating from the medulla oblongata (dorsal motor nucleus) will form a plexus first before going to the ganglion organs, namely:

1. cardiac plexus, goes to the heart to slow down the heart rate
2. pulmonary plexus, to the lungs
3. the esophageal plexus, leading to the esophagus, will then issue the anterior and posterior vagal trunks and the aortic plexus which is formed by smaller plexuses such as the celiac, mesenteric and hypogastric plexuses which will supply abdominal organs such as the small intestine, stomach, liver, gallbladder, kidneys, pancreas, kidney and part of the proximal large intestine as shown below.

The sacral parasympathetic nerves originate from the gray matter of the spinal cord segments S2-S4 whose preganglionic neurons will form the pelvic splanchnic nerves and pass through the pelvic hypogastric plexus which will innervate the organs: distal large intestine, urinary bladder, ureters, and reproductive organs.

The parasympathetic postganglionic will release the neurotransmitter ACh and will be captured by organs that have cholinergic receptors. There are two types of cholinergic receptors:

1. Nicotinic, this receptor is found in skeletal muscle and postganglionic dendrites and preganglionic sympathetic and parasympathetic nerves. The nature of this receptor always excites the target organ, namely skeletal muscle.
2. Muscarinic, these receptors are found on the target organs of the parasympathetic nerves. The properties of the receptor can be either inhibitory or excitatory. In the heart, the parasympathetic will be inhibited, but in the intestine, the parasympathetic nerves will excite to start the process of digestion.

2. Sympathetic nerves

also called “ the fight-or-flight system ” which functions to excite during emergencies and emergencies. As a result of sympathetic nerve stimulation is an increase in heart rate and contractility, breathing becomes fast and deep, hands become cold and sweaty, and pupils become dilated. This causes the body to become resistant to threats and stress.

As previously explained, the sympathetic nerves originate from the thoracolumbar nerve, where the preganglionic neurons originate from the gray matter. Then the preganglionic neurons go to the sympathetic trunk in the paravertebral column. The sympathetic pathways are as follows:

a. On the way to the head,

preganglionic neurons from T1-T4 will ascend to the superior cervical ganglion and will affect: the skin and blood vessels of the head region, activate the pupillary sphincter dilator muscle, block the sublingual nasal gland, causing dry mouth and some to the heart.

b. Pathway to the thorax,

preganglionic neurons originate from T1-T6 to the medial and inferior cervical ganglion and will supply the heart via the cardiac, pulmonary, aortic, oesophageal, thyroid plexus.

c. On the way to the abdomen,

preganglionic neurons originate from T5-L2 to the splanchnic nerves and will synapse in the celiac and mesenteric ganglia and will innervate: stomach, intestines, liver, spleen, and kidneys.

d. The pathways to the pelvic preganglionic neurons

originate from T10-L2 to the inferior hypogastric and mesenteric trunk ganglion and supply: distal large intestine, bladder, reproductive organs.

e. On the way to the adrenal medulla,

some nerves from the splanchnic junction pass through the celiac ganglion and synapse in the adrenal medulla, also known as the modified sympathetic ganglion. This is because the adrenal medulla is considered a postganglionic which will release 80% of catecholamines into the blood.

The postsynaptic postganglionic neuron will release the neurotransmitter norepinephrine which will be captured by the adrenoreceptors. Adrenergic receptors have 2 types of receptors namely alpha and beta (a and b). The a and b receptors are further divided into a 1, a 2 and b 1, b 2. The following describes adrenergic receptors:

Receptors are found in smooth muscle in the body (eyes, lungs, blood vessels, uterus, intestines, and genitourinary system). Activation of these receptors will cause an increase in the concentration of calcium ions, causing muscle contraction. The following happens when the receptor is activated:

1. Vasoconstriction
2. Increased peripheral vascular resistance
3. Mydriasis due to contraction of the radial pupillary muscle
4. Konstriksi spingter internal vesika urinaria

The receptors are found primarily in presynaptic nerve terminals. Activation of this receptor will cause inhibition of adenylate cyclase activation thereby reducing norepinephrine exocytosis. The following happens when the receptor is activated:

1. Norepinephrine release inhibition
2. insulin inhibition
3. Sedation and decreased blood pressure due to decreased sympathetic tone resulting in peripheral vasodilation caused by activation of postsynaptic receptors.

The receptors are located on the postsynaptic membrane in the heart. Here’s what happens during activation, namely

1. Tachycardia, because it causes positive chronotropic.
2. Enhanced lipolysis
3. Increased contractility of the myocardium

The receptors are found on postsynaptic smooth muscle and gland cells, where their activation causes smooth muscle relaxation. Here’s what happens during activation, namely

1. Vasodilation
2. Slight decrease in peripheral resistance
3. Increased muscle and liver glycogenolysis
4. Increased glucagon release
5. Uterine smooth muscle relaxation

Natural catecholamines in the body are epinephrine, norepinephrine, dopamine, and dobutamine. These catecholamines have specific adrenoreceptor activation, namely:

1. Epinephrine; activates a 1 , a 2 , b 1 , and b 2 /++,++,+++,++.
2. norepinephrine; activates a 1 , a 2 , and b 1 /++,++,++,-.
3. dobutamine; activates a 1 , a 2 , b 1 , and b 2 /++,++,++,+.
4. Dopamine; activates a 1 , a 2 , b 1 , and b 2 /-, -, +++,+.

Autonomic Nervous System Disorders

Disorders of this nervous system have varied symptoms, including impaired regulation of heart rate, blood pressure, body temperature, sweating, gastrointestinal and bladder function. Other symptoms that can be found include weakness, headache, syncope, and cognitive impairment.

Autonomic nervous system disorders are caused by another condition or disease, such as diabetes, or as a primary disorder the nervous system is the only system affected. Primary autonomic nervous system disorders, including:

1. Orthostatic hypotension
2. Orthostatic intolerance
3. Sindrom tatikardi ortostatik
4. Syncope
5. Neurogenic gastrointestinal tract (bowel movement disorders, constipation)
6. Erectile dysfunction and neurogenic bladder disorders.

Functions of the Autonomic Nervous System

The work of the autonomic nervous system, it is more or less influenced by the hypothalamus in the brain. If the hypothalamus is stimulated, it will affect autonomic movements such as accelerating the heart rate, inhibiting the work of the digestive tract and dilating the pupil of the eye. The autonomic nervous system consists of a combination of sensory nerves and motor nerves. The autonomic nervous system is divided into two types, as follows:

Sympathetic Nervous System

The sympathetic nervous system is a nerve located in front of the spinal segment that is based on the spinal cord (medulla spinalis) found in the chest and lumbar region. The sympathetic nervous system is also called the thoracolumbar nervous system, because the preganglionic nerve exits from the thoracic spine 1 to 12. The sympathetic nervous system consists of 25 pairs of ganglion or nerve nodes in the spinal cord. The main function of the sympathetic nervous system is to drive the work of body organs, although there are also some that inhibit the work of body organs.

1. Sympathetic Nervous System Function
2. Enlarge the pupil of the eye
3. Speed ​​up the heart rate
4. Enlarge the bronchi
5. Slows down the digestive system
6. Inhibits art sac contraction
7. Inhibits erection
8. Lowering blood pressure
9. Inhibits bile secretion
10. Increases adrenaline secretion

Parasympathetic Nervous System

The parasympathetic nervous system is a nervous system that originates in the spinal cord (medulla oblongata). The parasympathetic nervous system is also called the craniosacral nervous system because the preganglionic nerves exit the brain and sacral areas. Sympathetic nerves are interconnected networks with ganglia that are scattered throughout the body.

The parasympathetic nervous system has the opposite function of the sympathetic nervous system. While the main function of the sympathetic nervous system is to speed up the work of the body’s organs, the main function of the sympathetic nervous system is to slow down the work of the body’s organs. The work of the two opposing nervous systems produces a normal state.

1. Parasympathetic Nervous System Function
2. Minimize bronchi
3. Inhibits heart rate
4. Minimize the pupil of the eye
5. Accelerate the contraction of the art sac
6. Stimulate an erection
7. Speed ​​up the digestive system
8. Increase blood pressure
9. Increase bile secretion
10. Inhibits adrenaline secretion