Autonomic Nervous system Flashcards
What does the autonomic nervous system control, and what is its primary concern?
The autonomic nervous system controls visceral organs and is concerned with homeostasis—the maintenance of a stable internal environment in the face of changing external conditions.
What are the three major divisions of the autonomic nervous system, and what tissues do they innervate?
The three major divisions are the sympathetic system, the parasympathetic system, and the enteric system. The sympathetic and parasympathetic divisions innervate cardiac and smooth muscle as well as glandular tissue, while the enteric system controls the digestive tract.
What are the typical effects of the sympathetic and parasympathetic systems on target tissues?
The sympathetic system is especially activated in emergency fight-or-flight reactions, while the parasympathetic system is involved in rest-and-digest processes.
Where do the axons of sympathetic preganglionic neurons emerge from, and what is their role?
The axons emerge from the ventral roots of the thoracic and lumbar regions of the spinal cord, along with the axons of motor neurons. Postganglionic neurons project to the target organs.
Where are the synapses between preganglionic and postganglionic SYMPATHETIC neurons located, and what neurotransmitters are involved?
The synapses are clustered in a chain of sympathetic ganglia running along either side of the spinal cord. They synapse as soon as they leave the spinal cord (short). Sympathetic preganglionic neurons release acetylcholine, activating nicotinic acetylcholine receptors on postganglionic neurons (long). Postganglionic neurons release norepinephrine, which activates α and β adrenergic receptors on the target organs.
Where do the axons of PARASYMPATHETIC preganglionic neurons emerge from, and what neurotransmitters are involved?
The axons emerge from the brainstem (cranial nerves III, VII, IX, and X) and the sacral spinal cord. Preganglionic neurons extend almost all the way to their peripheral targets, with parasympathetic postganglionic neurons covering the remaining short distance.
Preganglionic parasympathetic neurons release acetylcholine, activating postsynaptic nicotinic acetylcholine receptors. Postganglionic neurons also release acetylcholine, activating muscarinic acetylcholine receptors on the target organ.
Which nerve provides parasympathetic input to visceral organs such as the heart and lungs?
The vagus nerve
Which nerves innervate the salivary glands?
The facial and glossopharyngeal nerves
What function does the oculomotor nerve serve in the parasympathetic system?
The oculomotor nerve innervates the smooth muscle responsible for the contraction and relaxation of the pupils of the eye.
What organs do parasympathetic projections from the sacral spinal cord innervate?
the bladder, large intestine, and reproductive organs.
How do sympathetic and parasympathetic systems generally affect heart rate and contraction strength vs affect respiratory system?
Sympathetic stimulation increases heart rate and the strength of heart contraction, while parasympathetic stimulation decreases heart rate and contraction.
Sympathetic stimulation causes bronchial tubes muscles to relax, while parasympathetic stimulation causes bronchial tubes muscles to constrict .
What does the enteric nervous system control?
The enteric nervous system controls the gastrointestinal tract, pancreas, and gallbladder
How autonomous is the enteric nervous system, and from where does it receive input?
The enteric nervous system is highly autonomous and can function normally without external neuronal input. It receives input from the sympathetic and parasympathetic systems.
What is the function of cholinergic neurons in the enteric system?
Cholinergic neurons in the enteric system tend to activate peristaltic contractions of the gut and adrenergic neurons, which supress gut peristalsis, as well as neurons that release neuropeptides, ATP and Nitrous Oxide.
What are the two layers of smooth muscle in the intestine, and what are the functions of the myenteric plexus and submucous plexus?
The intestine comprises longitudinal and circular layers of smooth muscle. The myenteric plexus controls smooth muscle contractions, while the submucous plexus controls intestinal secretions.
