Sympathetic vs parasympathetic System Differences

The nervous system is a complex body system with many functions.

It is the one that regulates the whole of human anatomy and physiology.

In this article, we will discuss only the divisions in the autonomic nervous system with brief functions. 

But we will see a few details leading to the sympathetic vs. parasympathetic System

The nervous system can be broadly divided as the

1. The Central Nervous System {has the brain and spinal cord}
2. The Peripheral Nervous System {has nerves from the brain and spinal cord)

This peripheral nervous system is again categorized as the

• The visceral nervous system (somatic and sensory nervous system)
• The autonomic nervous system 

This autonomic nervous system is divided as 

• Sympathetic nervous system
• Parasympathetic nervous system.

The Autonomic Nervous System is so-called because it is not under our ‘voluntary control.’

It is always active in regulating the body’s physiology. It controls the action of the organs at the subconscious level.

Autonomic Nervous System shares a relationship with the somatic nervous system and has functional links with it.

It also has a great relationship with the Endocrine System.

The examples are.
a) Cortisol is a catecholamine hormone secreted from Adrenal Cortex and from sympathetic nerve endings.
b) The adrenal Medulla is itself a modified sympathetic ganglion. Hormones secreted from Adrenal Medulla are actually secreted from sympathetic nerve endings.
c) Thyroxine, or the T4 hormone, secreted from the Thyroid gland, increases the number of beta-adrenergic receptors in the heart.

Sympathetic Vs. Parasympathetic Nervous System

Feature	Sympathetic Nervous System	Parasympathetic Nervous System
Also called as	Thoraco-lumbar outflow as its nerves emerges from the thoracic and lumbar regions of the vertebral column.	Cranio-sacral outflow as its nerves emerges from the cranium and sacral vertebrae.
The nerves origin	Nerves emerge from a level of T1 to 3rd or 4th lumber, i.e., L3 or L4.	The preganglionic nerve Efferents come out through the efferent root of the spinal segment. It then passes through the white rami, and it communicates the white rami, which connects the ventral root to the paravertebral sympathetic chain. In this point or region, most of the neural ends of preganglionic fiber send and relay with postganglionic neurons.
Preganglionic nerve fiber	The preganglionic nerve efferents come out through the lateral horn of the spinal cord, the preganglionic nerve fiber arises, traveling long up to the target organ where there is a ganglion, where they terminate.	Two or more types of neurotransmitters are seen in the Sympathetic Nervous System. Acetylcholine: The preganglionic nerve fibers that originate from the spinal cord and end up in the sympathetic ganglion secrete acetylcholine inside the ganglion. This acetylcholine acts on nicotinic receptors. Noradrenaline: The postganglionic nerve fibers originate from the sympathetic ganglion and end up in the viscera secrets noradrenaline inside the viscera. This secreted noradrenaline acts on adrenergic receptors,
Neurotransmitters	Two or more types of neurotransmitters are seen in the Sympathetic Nervous System. Acetylcholine: The preganglionic nerve fibers that originate from the spinal cord and end up in the sympathetic ganglion secrete acetylcholine inside the ganglion. This acetylcholine acts on nicotinic receptors. Noradrenaline: The postganglionic nerve fibers originate from the sympathetic ganglion and end up in the viscera secrets noradrenaline inside the viscera. This secreted noradrenaline acts on adrenergic receptors,	The neurotransmitter of the parasympathetic nervous system is only acetylcholine.
Receptor types	Receptors in the Sympathetic nervous system include adrenergic receptors, which are 5 in numbers- α1, α2, β1, β2, and β3.	Muscarinic receptors or simply M receptors are of 5 types as M1 – present in the brain M2 – present in the heart M3 – present in the stomach M4 – present in the pancreas M5 – located in smooth muscles.
Postganglionic nerve fiber	Postganglionic fiber is the supplier of the sympathetic system. It is the fiber which connects the sympathetic ganglion with different visceral organs. There are two other possibilities – either they may return to the spinal cord through gray rami communicantes, or they may spread along spinal nerves to supply to autonomic effectors like sweat glands or vascular smooth muscles.	The preganglionic nerve fibers originate from inside the brain and the spinal cord, and here, they are longer unlike that of sympathetic nervous a system where the postganglionic nerve fiber was longer. The postganglionic nerve fibers are very short; originate from the Parasympathetic ganglia situated very close to the target organ.
Through α receptors, they constrict the soft tissue dilator- pupillae, which results in the dilation of pupils of the eye.	Effect on the gut of the digestive system	They tend to constrict the pupil, stimulating the tissue constrictor- papillae.
Effect on salivary glands	Saliva secretion is minimized	Saliva secretion is profuse and enhanced
Through α receptors, they decrease peristaltic movements by decreasing motility and tone of the stomach and intestine.	Effects on the heart include all opposite to that of the sympathetic nervous system. It has negative ionotropic, chronotropic, and bathmotropic effects. The vagus nerve carries all these effects.	They increase the peristalsis of the gut as well as increase gastric emptying.
Effect on skin	Through α receptors, facilitates adrenergic sweating, by contraction of pilomotor muscles, which causes sweating in the hands and palms.	No effect
On heart	Β1 receptors are exclusively present in the heart and kidneys. So stimulating them to increase heart rate. Through β1 receptors, It exerts positive chronotropic, dromotropic, ionotropic and bathmotropic effects on the heart.	Through β3 receptors, being exclusively present in adipose tissue, initiate lipolysis.
Effect on fats and lipids in the body	It causes vasodilation of skeletal muscles and the liver. It causes dilation of bronchial smooth muscles. This property is used in inhalers, giving β2 agonists.	Parasympathetic nervous the system has no such effects.
On sex organs	Male: Ejaculation and vasoconstriction	Male: Erection
Effects on muscles and glands	Protection Response	They increase gland secretion, e.g., of gastric, pancreatic, etc.
Protection response	The sympathetic nervous system is the actual seat of the triple F response. The 3 Fs stand for Fright Fight Flight. It prepares the body to tackle dangerous situations.	The parasympathetic nervous system has no such effects.