Sympathetic (adrenergic) innervation modulates but does not generate basal tone in the internal anal sphincter smooth...

The parasympathetic division of the autonomic nervous system (ANS) regulates rest and digestion functions in the body. It works in opposition to the sympathetic division, promoting relaxation, conservation of energy, and digestion. The parasympathetic division consists of preganglionic fibers originating from specific cranial nerves (III, VII, IX, X) and the sacral spinal nerves (S2-S4). These fibers synapse with postganglionic neurons in the terminal ganglia, innervating various organs and...

Sympathetic signaling, a vital part of the autonomic nervous system, plays a crucial role in mobilizing the body's resources in response to stress or emergencies. It involves the transmission of nerve impulses from sympathetic preganglionic fibers to postganglionic fibers. This results in the release of specific neurotransmitters and activation of adrenergic receptors.
Sympathetic preganglionic fibers release the neurotransmitter acetylcholine (ACh) onto the ganglionic neurons in the...

The neuronal supply to the gastrointestinal (GI) tract is essential for regulating various functions, including digestion, absorption, and movement of food. This intricate network of nerves is known as the enteric nervous system (ENS), often referred to as the "second brain" of the body.
The enteric nervous system consists of two major plexuses: the myenteric plexus (Auerbach's plexus) and the submucosal plexus (Meissner's plexus). These plexuses are located within the layers of the GI tract...

The sympathetic division of the autonomic nervous system (ANS) plays a crucial role in preparing the body for stress, physical activity, and increased energy demands. This division activates the "fight-or-flight" response, enabling individuals to respond effectively to challenging situations.
Originating in the thoracic and lumbar spinal cord segments, the preganglionic fibers of the sympathetic division exit the spinal cord through the white ramus communicans. They then enter the sympathetic...

The sympathetic pathways of the collateral ganglia and adrenal medulla serve unique but interconnected roles in the sympathetic response.
Collateral Ganglia
Sympathetic preganglionic axons reach the collateral ganglia along the route of splanchnic nerves. These nerves bypass the sympathetic trunk and communicate with sympathetic postganglionic neurons housed in the prevertebral ganglia. These ganglia supply the organs of the abdominopelvic cavity.
The greater splanchnic nerve, formed by the...

Parasympathetic signaling plays a crucial role in regulating various physiological processes. It involves the release of acetylcholine (ACh) by parasympathetic neurons, which can have localized and short-lived effects. The majority of ACh released is rapidly inactivated at the synapse by the enzyme acetylcholinesterase (AChE), which hydrolyzes Ach into choline and acetate. Additionally, the tissue cholinesterase deactivates any ACh diffusing into the surrounding tissues.
The effects of...