Chapter 14- The autonomic nervous system Flashcards
Somatic nervous system
Branch of the PNS, it’s a system responsible for voluntary muscle movements and reflex arcs. Mostly efferent.
Somatic refers to
Skeletal muscle tissue
Which neurotransmitter is released by the SNS?
Acetylcholine, it has an excitatory effect at is released at all synapses in the SNS
Autonomic nervous system
A branch of the PNS, almost all effectors are visceral (involuntary). Branches into the sympathetic and parasympathetic divisions
Autonomic nervous system function
Helps maintain a stable internal environment. Regulation of heart rate, blood vessel diameter, pupil size, body temperature, increases/decreases stomach secretions
Effector organs of the SNS
Skeletal muscle tissue
Effector organs of the ANS
Cardiac muscle, smooth muscle, and glands
SNS efferent pathways
A single neuron extends from CNS to effector. Motor neuron cell bodies are located in the CNS, axons in PNS extend to skeletal muscle. Thick and heavily myelinated fibers.
ANS efferent pathways
The ANS has a two neuron chain to reach effector, consists of preganglionic and postganglionic neurons.
Preganglionic neuron (ANS)
Cell body is located in the CNS, preganglionic axon synapses with second motor neuron. Thin, lightly myelinated fibers
Postganglionic neuron (ANS)
Cell body is located outside the CNS, postganglionic axon extends to effector organ. Thin, nonmyelinated fibers
ANS ganglia
Ganglia in the ANS are sites of synapse between the preganglionic neuron and the postganglionic neuron. Entirely motor ganglia.
Which neurotransmitters are released by the ANS?
Releases norepinephrine or acetylcholine- effect can be excitatory or inhibitory depending on receptors on the effector organ in ANS.
Parasympathetic division function
“Rest and digest”- keeps body energy use as low as possible when we are relaxed. Directs “housekeeping” activities- digestion, elimination of waste, low blood pressure and heart rate, constricted pupils.
Where do the fibers of the parasympathetic nervous system originate?
The brain and sacral spinal cord. Preganglionic fibers are long, postganglionic fibers are short. The ganglia will always be closer to the effector organ than they are to the nervous system
Cauda equina
Sacral spinal cord
Cranial portion of the parasympathetic nervous system
Will serve the head, neck, thorax, and abdomen. Preganglionic fibers run in oculomotor, facial, glossopharyngeal, and vagus cranial nerves
Oculomotor nerve
Innervates smooth muscle in the eyes and muscle associated with the lens. Effect- lens is stimulated to become thicker
Facial nerve
Stimulates large glands of the head (salivary glands, nasal glands, lacrimal glands)
Glossopharyngeal nerve
Activates parotid salivary gland. The parotid salivary gland is the largest one
Vagus nerve
Provide fibers to neck and almost every organ in the thoracic and abdominal cavities. The vagus nerve is large and complex, so we see plexus formation
Cardiac plexus
supplies fibers to the heart, division of the vagus nerve
Pulmonary plexus
supplies fibers to the lung, division of the vagus nerve
Esophageal plexus
Serves the esophagus. The fibers from the esophageal plexus also extend into the abdominal cavity- innervates liver, gallbladder, stomach, small intestine, pancreas, and proximal half of large intestine