Chapter 16: The Autonomic Nervous System Flashcards
Causes contraction of skeletal muscle
Controls voluntary responses
Somatic Nervous System
Controls cardiac and smooth muscle and glands
Controls involuntary responses
Helps maintain homeostasis in the body
Autonomic Nervous System
Associated with “fight-or-flight” responses
Sympathetic Nervous System
Associated with “rest and digest” responses
Parasympathetic Nervous System
Responds to a threat to our homeostasis (stress) or enables survival
Increases oxygen delivered to skeletal muscle
Increases sweating
Blood is shifted away from the digestive system and toward skeletal muscle
Pupils dilate
Brain becomes alert
Sympathetic Division of the Autonomic Nervous System
Preganglionic cell bodies in thoracic and lumbar regions of spinal cord
thoracolumbar system
Preganglionic cell bodies in thoracic and lumbar regions of spinal cord
23 ganglia located next to vertebral column
Some preganglionic neurons synapse outside of sympathetic chain
Sympathetic Pathways
project through white rami communicantes and can synapse:
At the ganglion at the same level
At a more superior or inferior ganglion
At prevertebral ganglia or the adrenal medulla
Short preganglionic axons
project to target effector through gray rami communicantes
Long postganglionic axons
Includes the celiac ganglion, superior mesenteric ganglion, and inferior mesenteric ganglion
Collateral Ganglia
Located anterior to vertebral column
Also known as prevertebral ganglia
Collateral Ganglia
Help regulate activities of abdominal organs
Considered part of enteric nervous system
Receive input from splanchnic nerves and central sympathetic neurons
Collateral Ganglia
is in lateral horn of the thoracic or lumbar region of the spinal cord
Cell body of the preganglionic neuron
synapses with postganglionic neuron close to spinal cord
Preganglionic axon
synapses within target organ
Long postganglionic axon
Used at the synapse of the sympathetic preganglionic and postganglionic neurons
Acetylcholine (ACh)
Released by postganglionic neurons onto target cells
Norepinephrine
Activation of the sympathetic NS can cause hormone release in the adrenal medulla
Epinephrine (adrenaline) and norepinephrine (noradrenaline)
Preganglionic axons terminate in adrenal medulla
No ganglion involved
Active when body is not stressed or under a threat
Controls “rest and digest” activities
Salivation
Lacrimation (the flow of tears)
Urination
Digestion
Defecation
Sexual arousal
Parasympathetic Division of the Autonomic Nervous System
Cell bodies of preganglionic neurons located in brain stem and sacral spinal cord
craniosacral system
project to ciliary ganglion; postganglionic neurons then control iris
Preganglionic axons in oculomotor nerve (CN III)
project to pterygopalatine and submandibular ganglia to control production of saliva, mucus, and tears
Innervates two of the three salivary gland pairs
Preganglionic axons in facial nerve (CN VII)
project to otic nucleus to control saliva production
Innervates only one pair of salivary glands
Preganglionic axons of glossopharyngeal nerve (CN IX)
to innervate organs in thoracic, abdominal, and pelvic cavities
Preganglionic axons mix with sympathetic postganglionic axons in plexuses
Preganglionic axons project through vagus nerves (CN X)
Travel through hypogastric plexus and synapse in terminal or intramural ganglia
Postganglionic axons project into pelvic cavity
Preganglionic axons from sacral region form pelvic splanchnic nerves
Acetylcholine (ACh) is neurotransmitter released
Cholinergic synapses
Norepinephrine is neurotransmitter released
Adrenergic synapses
Endogenous ligand—acetylcholine
Exogenous ligand—nicotine
Chemically-gated ion channel
Nicotinic receptors
Endogenous ligand—acetylcholine
Exogenous ligand—muscarine
Trigger changes in cell without allowing ions to pass through membrane
Muscarinic receptors
—located in skin, GI and pelvic organs, and blood vessels
Cause contraction of smooth muscle
α1
—found in pancreas, platelets, brain, and spinal cord
Inhibit insulin release
Promote blood clotting
α2
—found in heart and kidney
Increase heart rate, force of contraction, and secretion of renin
β1
—found in blood vessels, lungs, uterus, stomach, and small intestines
Cause relaxation of smooth muscle
β2
—found in adipose tissue
Stimulate breakdown of lipids
β3
Help maintain internal homeostasis
Blood pressure
Heart rate
Airway diameter
Digestive activity
Autonomic Reflexes
single neuron, Sensory info comes from somatic and special senses and viscera
Afferent branch
two neuron, Preganglionic neuron synapses with postganglionic neuron in a ganglion
Efferent branch
regulates heart rate and strength of contractility
Cardiac plexus
regulates size of airways in lungs
Pulmonary plexus
regulates movement of food through esophagus
Esophageal plexus
regulates abdominal organs and pelvic tissues
Abdominal aortic plexus
Both divisions of the autonomic nervous system innervate most organs
dual innervation
effects of parasympathetic nervous system are seen
Parasympathetic dominance
effects of sympathetic nervous system are seen
Opposite of parasympathetic effects
Sympathetic dominance
Balance between parasympathetic and sympathetic dominance when an organ is at rest
Autonomic Tone
dominates the heart at rest
Lowers heart rate to normal range
Parasympathetic tone
dominates blood vessels at rest
Adjusts constriction of vessels to maintain blood pressure
Sympathetic tone
Autonomic nervous system helps body respond to stress
Aim is to increase nutrients in blood and deliver more blood to head and muscles
Stress
