Autonomic Nervous System Flashcards
What does the somatic component of the nervous system do?
collects:
- sensory information including tactile, pain, and thermal sensation
- proprioception from external environment
propagates motor impulses to skeletal muscles
What does the visceral (autonomic) component of the nervous system do?
- gathers sensory info such as pressure and stretch from internal milieu
- distributes motor impulses to glands, smooth muscles, and cardiac muscles
What is the motor part of the somatic nervous system composed of?
a single neuron that connects CNS (either the motor nuclei of cranial nerves or the anterior horns of the spinal cord) to the skeletal muscles
What is the motor part of the autonomic nervous system composed of?
2 neurons that synapse at autonomic ganglia, and connect the CNS (either parasympathetic nuclei of cranial nerves III, VII, IX and X - or lateral horns of spinal cord) to target organs
What are the 2 divisions of the motor component of the autonomic nervous system?
sympathetic division
parasympathetic division
What does the sympathetic division of the autonomic nervous system do?
- prepares body for emergencies (flight or flight), increasing heart beat and respiratory rate, constricting peripheral blood vessels, and increasing blood pressure
- changes distribution pattern of blood in body (ie. blood will be rerouted from skin and intestine to skeletal muscles)
- suppresses peristaltic movements of gastrointestinal tract, and constricts sphincters
What does the parasympathetic division of the autonomic nervous system do?
- stores energy (rest and response)
- usually activated after meal and reduces heart beat, increases gastrointestinal tract and endocrine gaand secretion, and dilates sphincters of gastrointestinal tract and urinary system
- causes sleepiness
Sympathetic Nervous System
What is the sympathetic division composed of?
- centers
- ganglia
- efferent fibers
Sympathetic Nervous System
What do efferent fibers do?
connect centers and ganglia to target organs
Sympathetic Nervous System
What are the preganglionic (motor) neurons of this system?
- reside in lateral horn of spinal cord segemnts T1-L2
- axons of these neurons form efferent (motor) fibers that travel along with the ventral root of the corresponding spinal nerve
Sympathetic Nervous System
What are white ramus communicans?
efferent (motor) fibers after emerging through the intervertebral foramen, and entering the sympathetic trunk
Sympathetic Nervous System
4 routes that preganglionic fibers may take.
- They may synapse with the postganglionic neurons in the sympathetic trunk ganglia at the same level. The axons of postganglionic neurons either return to the corresponding spinal nerve as gray ramus communicans to be distributed to the body wall or directly target the thoracic viscera. Those postganglionic fibers traveling with the spinal nerve target the smooth muscles and glands of the body wall skin. Those postganglionic fibers targeting the thoracic viscera arise from Tl to T4 ganglia and are usually named after their primary targets such as cardiac and esophageal nerves.
- They may ascend to higher levels or descend to lower levels along with the sympathetic trunk and synapse with the postganglionic neurons at that level. The postganglionic fibers then either enter the spinal nerve as gray ramus communicans to be distributed to the upper and lower limbs or directly target the head and neck viscera.
- Some of these preganglionic fibers bypass the sympathetic
trunk ganglia without synapsing and form splanchnic nerves including greater, lesser, least, and lumbar splanchnic nerves. The splanchnic nerves enter the abdomen and synapse with the postganglionic neurons in prevertebral ganglia
such as celiac, superior mesenteric and inferior mesenteric ganglia. The postganglionic fibers then target the abdominal or pelvic viscera. It’s worth mentioning that the sacral splanchnic nerves are exceptionally postganglionic fibers and directly target some of the pelvic viscera. - There are also some preganglionic fibers that bypass the sympathetic trunk ganglia without synapsing and supply the suprarenal (adrenal) medulla, thus the suprarenal medulla cells act as the postganglionic neurons.
Sympathetic Nervous System
What are gray ramus communicans?
axons of postganglionic neurons may return to the corresponding spinal nerve as gray ramus communicans (otherwise they are distributed to the body wall or directly target the thoracic viscera)
Sympathetic Nervous System
What are the 4 types of splanchnic nerves?
- greater
- lesser
- least
- lumbar
Sympathetic Nervous System
What are splanchnic formed by?
formed by preganglionic fibers, if these fibers bypass sympathetic trunk ganglia without synapsing
Sympathetic Nervous System
What are the 3 types of prevertebral ganglia?
- celiac
- superior mesenteric
- inferior mesenteric
Sympathetic Nervous System
What are sacral splanchnic nerves?
exceptionally postganglionic fibers that directly target some of the pelvic viscera
Sympathetic Nervous System
What is the sympathetic trunk (chain) formed by?
ascending and descending sympathetic fibers and the associated ganglia (paraverterbal ganglia)