Quiz 9 - ANS Flashcards
somatic nervous system
operates under voluntary (conscious) control; controls skeletal muslces
autonomic nervous system
operates under involuntary instruction; controls visceral organs
what systems does the ANS coordinate
cardiovascular, respiratory, digestive, urinary, reproductive
preganglionic neurons
axons of preganglionic neurons; leave CNS and synapse on ganglionic neurons
ganglionic neurons
in autonomic ganglia, innervate visceral organs (cardiac muscle, smooth muscle, glands and adipose tissue)
postganglionic fibers
axons of ganglionic neurons
divisions of the ANS
sympathetic and parasympathetic
sympathetic
fight or flight - response to emergency, high-stress, high-exertion situations (utilizes energy stores)
parasympathetic
rest and digest - maintains resting conditions, reduces metabolic rate and promotes digestion (conserves energy)
parts of sympathetic nervous system
- thoracolumbar
- preganglionic neurons
- ganglia
- ganglionic neurons
thoracolumbar
preganglionic neurons originate from the thoracic and lumbar segments (T1-L2) of spinal cord
preganglionic neurons in SNS
short preganglionic fibers, (most) ganglia close to spinal cord
three types of ganglia
sympathetic chain ganglia
collateral ganglia
adrenal medullae
sympathetic chain ganglia
(paravertebral) - on both sides of cerebral column
- control effecters: in body wall, thoracic cavity, head, neck, limbs
collateral ganglia
(prevertebral) - anterior to vertebral bodies
- contain ganglionic neurons that innervate tissues and organs in abdominopelvic cavity
adrenal medullae
very short postganglionic fibers
- when stimulated, release neurotransmitters (epinephrine and norepinephrine) into bloodstream which affect target cells throughout body
ganglionic neurons of SNS
long postganglionic fibers (except in adrenal medullae)
- extensive divergence: allows it to function as a unit (mass activation) and also more diffuse and widespread response
specific functions of SNS
- dilation of pupils
- increase in alertness, feelings of energy and euphoria
- increase in cardiovascular activity
- increase in respiratory activity
neurotransmitters released in SNS
- both systems release acetylcholine (ACh) at ganglion
- norepinephrine and epinephrine - released by postganglionic fibers to target tissues and bloodstream
parts of parasympathetic nervous system
craniosacral
preganglionic neurons
ganglionic neurons
postganglionic fibers
craniosacral
brain stem (cranial nerves III, VII, IX, X) and sacral segment (S1-S4) of spinal cord
preganglionic neurons in PNS
long
ganglionic neurons in PNS
near or at effector organs (short)
postganglionic fibers in PNS
short, innervates structures in head and organs in thoracic and abdominopelvic cavities (effects are usually more specific and localized
specific functions of PNS
- constriction of pupils
- decrease cardiovascular activity
- increase arousal and stimulation of sexual glands
- decrease digestive activity
neurotransmitters released on PNS
parasympathetic: acetylcholine released by postganglionic fibers
dual innervations of SNS and PNS
- most visceral organs receive dual innervation (both SNS/PNS)
- usually have opposing effects (antagonistic)
- most prominent in digestive tract, heart and lungs
