Autonomic Nervous System Flashcards
Autonomic Nervous System Overview
- visceral motor division of PNS
innervates:
- smooth muscle
- cardiac muscle
- glands
regulates
- heart rate
- blood pressure
- digestion
- urination
Autonomic Motor Systems
- a chain of two motor neurons: postganglionic and preganglionic
- connected by autonomic ganglion
- differs from somatic motor system having only 1 neuron
Autonomic vs. Somatic Motor Systems
Autonomic: involuntary control of glands, cardiac and smooth muscle via two nerve fibers from CNS using acetylcholine or norepinephrine for excitatory or inhibitory effect
Somatic: voluntary control of skeletal muscle via one nerve fiber from the CNS using acetylcholine only for excitatory effect
Divisions of Autonomic Nervous System
Sympathetic - “fight or flight”
Parasympathetic - “rest and digest”
- innervate mostly same structures but cause oppostie effects
Sympathetic Nervous System
- “fight or flight” response
- activated when extra metabolic effort is necessary
Effects:
- increased heart rate
- fast, deep breathing
- dilated pupils
- increased skeletal muscle blood supply
- digestion inhibited
- thoracolumbar origin (T1-L2)
Parasympathetic Nervous System
- “rest and digest”
- relaxes the body and controls routine maintenance functions
- concerned with conserving energy
- craniosacral origin
Location of Autonomic Ganglia
sympathetic - close to CNS
parasympathetic - close to or within effector organ
Length of Preganglionic Autonomic Nerve Fibers
Sympathetic - short
Parasympathetic - long
Length of Postganglionic Autonomic Nerve FIbers
sympathetic - long
parasympathetic - short
Origins of Autonomic Nerves
Sympathetic - thoracolumbar ( T1-L2)
Parasympathetic - craniosacral
Branching of Autonomic Nerve Axons
Sympathetic - highly branched to influence many organs
Parasympathetic - few branches for localized effect
Neurotransmitter used by ALL preganglionic autonomic axons.
Acetylcholine
(both para- and sympathetic)
Neurotransmitter in most postganglionic sympathetic nerve fibers
Norepinephrine
- known as adrenergic synapses
Neurotransmitter in all postganglionic parasympathetic nerve fibers
Acetylcholine
- known as Cholinergic synapses
location of sympathetic chain ganglia
Paravertebral - on either side of vertebrae
name for the columns of ganglia on either side of the spine/spinal cord
Sympathetic Trunks
- ganglia are fused so fewer ganglia than spinal nerves
- originate from T1 to L2
- 3 cervical, 11 thoracic, 4 lumbar, 4 sacral, 1 coccygeal
the ganglia shown here AND the term for their location
Collateral Ganglia
Prevertebral Location (AKA prevertebtral ganglia)
- lie anterior to the aorta in the abdomen and pelvis
- not paired or segmentally arranged like sympathetic trunks
two divisions of parasympathetic outflow
Cranial - originates from brain
Sacral - originates from sacral region of spinal cord
Cranial Outflow (of parasympathetic NS)
- originates from brain via cranial nerves
Innervates: organs of head, neck, thorax, abdomen
Sacral Outflow (of parasympathetic NS)
- originates from sacral spinal cord
innervates: remaining abdominal and pelvic organs
Cranial Nerves Containing Preganglionic Parasympathetic Fibers
III Oculomotor
VII Facial
IX Glossopharyngeal
X Vagus
Dual Innervation
- innervation of same organ by both para- and sympathetic NSs
Can have two different effects:
Antagonistic Effect: each division innervates different cells to create opposing effects
ex: pupillary dilator muscle (sympathetic) vs. constrictor pupillae (parasympathetic)
Cooperative Effect: both divisions cause same effect
ex: parasympathetic increases salivary serous cell secretion, sympathetic increases salivary mucous secretion
Single Innervation
- some effectors receive only sympathetic:
- adrenal medulla
- arrector pili
- sweat glands
- many blood vessels
