Autonomic Nervous System Overview

Autonomic Nervous System

• The autonomic nervous system (ANS) regulates involuntary functions like heart rate, blood pressure, and digestion. It works unconsciously, affecting many body systems.
• Objectives for studying the ANS include understanding the ANS itself, the division of the ANS (sympathetic, parasympathetic, and enteric nervous systems).

System Overview

• The ANS regulates involuntary functions, including heart rate, blood pressure, and digestion.

Main Components

• Sympathetic Nervous System: Prepares the body for stressful situations (“fight or flight”). Increases heart rate and diverts blood flow to essential organs.
• Parasympathetic Nervous System: Promotes “rest and digest” activities. Decreases heart rate and enhances digestion and relaxation after stress.

Differences between Sympathetic and Parasympathetic NS

• Preganglionic fibers in the parasympathetic division are long; postganglionic fibers are short. Conversely, in the sympathetic system, preganglionic fibers are short and postganglionic fibers are long.
• The parasympathetic system innervates significant areas of tissues and organs, while the sympathetic system innervates limited areas of the body.
• The mediator for both divisions (sympathetic and parasympathetic) in preganglionic nerve fibers is acetylcholine or similar compounds (cholinergic substances). Parasympathetic postganglionic fibers also contain acetylcholine or similar compounds. The sympathetic system's postganglionic fibers contain adrenaline or norepinephrine, or substances similar in action (adrenergic).

Autonomic Innervation of Lacrimal Gland, Submandibular and Sublingual Salivary Glands

• The facial nerve (VII) carries a parasympathetic component that innervates the submandibular and sublingual salivary glands via the submandibular ganglion.

Age Features of the Parasympathetic Nervous System

• In children, the autonomic nodes and nerves are smaller than in adults.
• Parasympathetic nodes have small cells that increase in size by age 3.
• Between ages 3 and 16, there's rapid growth in parasympathetic cell dendrites, leading to more synapses.

Sympathetic Nervous System

• Preganglionic fibers of the sympathetic nervous system originate from nerve cell bodies in the lateral horn of spinal cord levels T1 to L2,3.

Innervation of the Heart

• The superficial cardiac plexus is located on the anterior surface of the pulmonary trunk.
• The deep cardiac plexus is behind the aortic arch and in front of the tracheal bifurcation.

Sympathetic part

• Includes the celiac ganglia, superior and inferior mesenteric ganglia, and the inferior hypogastric plexus.

Ramus communicantes albi

• Bundles of preganglionic sympathetic fibers emerging from the spinal nerve and entering the sympathetic trunk.
• Myelinated.
• Located only in the thoracic and lumbar regions of the sympathetic trunk.

Branches outgoing from the sympathetic trunk

• Ramus communicantes grisei connect to nearby spinal or cranial nerves (starting with the 9th cranial nerve); these contain postganglionic sympathetic fibers.
• Visceral nerves (nn. viscerales) carrying postganglionic fibers innervate internal organs of the head, neck, and thorax.
• Internal nerves (nn. splanchnici) lead to plexuses in abdominal and pelvic cavities.
• Branches extend from the sympathetic trunk to nearby blood vessels.

Nerve Supply of the Nasal Cavity

• Parasympathetic fibers reach nasal glands via the facial nerve (and the greater petrosal nerve)
• Sympathetic fibers originating in the superior cervical ganglion reach the nasal cavity via blood vessels.

Autonomic Innervation of Mucosa of Nasal Cavity and Palate

• The pterygopalatine ganglion, innervated by the pterygopalatine nerve, provides autonomic innervation to the nasal mucosa and palate.
• Several nerves (e.g., greater and deep petrosal, branches of cranial nerve V2) are involved.

Salivary Glands

• The parotid gland develops during weeks 4-6, with blood supply from the external carotid artery and parasympathetic innervation from the 9th cranial nerve.
• The submandibular gland develops during week 6 and receives blood supply from the facial and lingual arteries, with parasympathetic innervation from the facial nerve.
• The sublingual gland develops during weeks 8-12 and receives blood supply from the sublingual and submental arteries, with facial nerve parasympathetic innervation.

This quiz covers the autonomic nervous system (ANS), focusing on its role in regulating involuntary bodily functions such as heart rate and digestion. You'll explore the distinctions between the sympathetic and parasympathetic divisions, including their functions and impacts on the body. Test your knowledge on the complexities of the ANS and its significance in maintaining homeostasis.