【Neuro & Pharmacology】Autonomic Division

 Autonomic Division

Autonomic (autonomous: self-governing) or called visceral nervous system (it control over internal organs)

Subdivided into: 

-sympathetic system: stressful situations, fight-or-flight response

-parasympathetic systems (para-, beside or alongside): resting, digestion

Autonomic Pathways have two Efferent Neurons in Series

Content:

1. The anatomical differences of two autonomic branches

2. Function of Sympathetic and Parasympathetic nervous system

3. The anatomy and chemical communication of the sympathetic and parasympathetic systems

4. The synthesis and breakdown of autonomic neurotransmitters

5. Adrenal medulla

6. Primary Disorders of the Autonomic Nervous System

1. The anatomical differences of two autonomic branches

• The pathways’ point of origin in the CNS 
• The location of the autonomic ganglia.

Characteristic	Sympathetic	Parasympathetic
Origin in the CNS	Thoracic and lumbar segments	Brain stem and sacral segments
Ganglion Location	Close to spinal cord	On or close to targets
Pathways	Short preganglionic. Long postganglionic neurons	Long preganglionic, Short postganglionic neurons

2. Function of Sympathetic and Parasympathetic nervous system

3. The anatomy and chemical communication of the sympathetic and parasympathetic systems

Both sympathetic and parasympathetic preganglionic neurons release acetylcholine (Ach) onto nicotinic cholinergic receptors (nAChR) on the postganglionic cell.

Most postganglionic sympathetic neurons secrets norepinephrine (NE) onto adrenergic receptors on the target cell.

Most postganglionic parasympathetic neurons secrete acetylcholine onto muscarinic cholinergic receptors (mAChR) on the target cell.

Some exceptions:

Sympathetic cholinergic neurons

• Sympathetic postganglionic neurons that secrete Ach rather than norepinephrine. 
• eg, Sympathetic postganglionic neurons that terminate on sweat glands

Noradrenergic, noncholinergic neurons

• Autonomic neurons secrete neither norepinephrine neurons or acetylcholine
• eg, Substance P, somatostatin, vasoactive intestinal peptide (VIP), adenosine, nitric oxide, and ATP.

4. The synthesis and breakdown of autonomic neurotransmitters

i. Autonomic Receptors have multiple subtypes

a. Adrenergic Receptors

*NE = norepinephrine, E = epinephrine; IP3 = inositol triphosphate, cAMP = Cyclic adenosine monophosphate, cAMP is a derivative of adenosine triphosphate (ATP) and used for intracellular signal transduction

b. Cholinergic Receptors

**M2 and M3 are the primary muscarinic receptors on parasympathetic targets;

PKC = protein kinase C

c. ACh muscarinic receptors

5. Adrenal medulla

The adrenal medulla is a specialized neuroendocrine tissue associated with the sympathetic nervous system.

• Adrenal medulla: secretes epinephrine
• Sympathetic branch of nervous system: secretes norepinephrine

6. Primary Disorders of the Autonomic Nervous System

Direct damage (trauma) to hypothalamic control centers 👉 Disrupt the body’s ability to regulate water balance or temperature

Systemic diseases such as cancer and diabetes mellitus 👉 Generalized sympathetic dysfunction, or dysautonomia

CNS control centers for autonomic functions degenerate 👉 Multiple system atrophy

Diminished sympathetic input to blood vessels 👉 abnormally low blood pressure

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