Autonomic System Flashcards
Autonomic nervous system
- a sensory and moto system, innervation visceral tissues and organs
- it is intimately connected to the idea of homeostasis,
Two major divisions
- Sympathetic
- Parasympathetic
* both inercate cardiac, smooth muscle, and gladular tissue
related to the enteric system as well (which controls the gut)
Sympathetic System
-governs flight-or-fight reactions
Parasympathetic System
-responsible for rest-and-digest processes
autonomic ganglia
-autonomic motor neurons(referred to as postganglionic neurons) are located outside of the spinal cord in cell groups
What do sympathetic preganglioinic neurons release?
acetylcholine, which activates postganglionic neurons through nicotinic acetylcholine receptors
What do sympathetic postganglionic neurons release?
norepinephrine, which modulates target tissues through interaction with alpha adrenergic and B adrenergic receptors.
What do parasympathetic preganglionic neurons release?
acetylcholine, activation postganglionic neurons through nicotinic acetlycholine receptors
What do parasympathetic postganglionic neurons fibers release?
acetylcholine, however ACh modulates the target tissue through activation of muscarinic acetylcholine receptors.
Where do parasympathetic preganglionic fibers emerge from?
- the brain stem (cranial nerves III, IX, and X)
- sacral spinal cord
Where do sympathetic preganglionic fibers emerge from?
- thoracic and lumbar chord
- sympathetic ganglia form interconnected chains on either side of the chord called sympathetic trunks.
Sensory inputs to the autonomic nervous system
- the ANS responds to a variety of sensory inputs (e.g. stimulation of pain-sensing neurons in the skin activates sympathetic neurons to regulate local vasoconstriction)
- Most sensory information from visceral organs reaches the brain by way of the vagus nerve (X). Visceral sensory information from the head and neck enter the brain through the glossopharyngeal (IX) and facial (VII) nerves. These inputs synapse in brainstem nuclei. The most important brainstem region is called the nucleus of the solitary tract.
-These brainstem regions mediate direct autonomic reflexes and projects to higher brain areas (e.g. the hypothalamus and cerebral cortex), which regulate more complex autonomic responses.
Baroreceptor Reflex
-sympathetic activation results in an increase in cardiac output and an increase in blood pressure. This results in activation of pressure-sensitive baroreceptor neurons in the aortic arch and the carotid sinus, signaling the increased blood pressure to the nucleus of the solidarity tract. This results in parasympathetic activation and a resulting fall in blood pressure and heart rate.
Enteric Nervous System
- controls the GIT, pancreas, and gallbladder
- controls smooth muscle in the gut, local blood vessels and secretion by the mucosa.
- contains cholinergic neurons, which tend to activate peristaltic contractions of the gut, and adrenergic neurons, which suppress gut peristalsis, as well as neurons that release neuropeptides, ATP and NO.
The enteric system consists of two networks of neuronal cell bodies and fibers
- cell bodies and fibers along the entire length of the gastrointestinal tract
1. Myenteric Plexus: principally controls gut motility
2. Submucosal plexus: controls secretory functions of the gut.
How does the hypothalamus play a critical role?
It integrates autonomic responses and endocrine function with behavior to maintain basic homeostatic requirements of everyday life.
