Anatomy Chapter 14- The Autonomic Nervous System Flashcards
Somatic Nervous System
system responsible for voluntary muscle movements and somatic reflex arcs
Mostly voluntary / Only involuntary is if there’s damage somewhere in the spinal reflex
The autonomic Nervous System
Almost all effectors are visceral
involuntary control
homeostasis is maintained - stable internal environment
regulation of heart rate, blood vessel diameter, pupil size, body temperature, increases/decreases stomach secretions
ANS vs SNS
- Effector organs
- Efferent pathways
- Neurotransmitter effects
Effector organs
SNS- skeletal muscle tissue
ANs- cardiac muscle, smooth muscle, and glands (visceral organs)
Efferent pathways and ganglia
SNS- single neuron extends from CNS to effector
ANS- Consists of a two-neuron chain to reach the effector
Preganglionic neuron
Cell body in the CNS, axon synapses with second motor neuron
Always ends motor output that sends visceral activity
Postganglionic neuron
cell body is outside the CNS, axon extends to effector organ
Ganglia
Site of synapse between the pregangionic neuron and postganglionic neuron
Neurotransmitter effects
SNS- all release acetylcholine (excitatory)
ANS- Release norepinephrine or acetylcholine (excitatory or inhibitory)
ANS Parts
- Parasympathetic
- Sympathetic
Parasympathetic Division Known as…
“Rest and Digest”
Function of Parasympathetic
Directs “housekeeping” activities concerning digestion & waste elimination
heart rate & blood pressure (low bp and heart rate)
airway diameter (bronchi leading into lungs - not a large volume of air needed and airways will be smaller)
pupil diameter (smaller)
reproduction (gamete production increases)
Origin of Fibers of Parasympathetic
the brain and the sacral spinal cord
Preganglionic fibers are long
postganglionic fibers are short
Location of ganglia in parasympathetic
In or near the effector organ
Cranial Portion of Parasympathetic
Supplies fibers to head, neck, thoracic and abdominal regions
Fibers run in oculomotor, facial, glossopharyngeal, and vagus cranial nerves
Oculomotor nerve
Innervates smooth muscle in eyes and muscles associated with lens
Controls 4/6 of the extrinsic eye muscles
Facial nerve
Stimulates large glands of the head
keeps nasal passages more fluid
Glossopharyngeal nerve
Activates carotid salivary gland
Produces more salvia and fluids to keep nasal passages more fluid
vagus Nerve
provide fibers to the neck and almost every organ in thoracic & abdominal cavities
parasympathetic division
Cardiac plexus
Supplies fibers to the heart
resting- 72 bpm
Pulmonary plexus
Supplies preganglionic fibers to lung
12 breaths per minute
Esophageal plexus
Serves esophagus
Fibers extend into the abdominal cavity from this plexus that innervates the liver, gallbladder, stomach, etc.
Sacral Portion of the parasympathetic
From pelvic splanchnic nerves
serves pelvic organs and distal portion half of large intestine
will be stimulatory and waste remove
ovaries and testes more active
Sympathetic Division
Fight or Flight
Function of Sympathetic division
Mobilizes the body for action by affecting heart rate and blood pressure, airway diameter, pupil diameter, digestion & waste elimination, reproduction, etc. - slows these things down
Fibers of the sympathetic division
thoracolumbar region of the spinal cord
Location of ganglia of sympathetic division
close to the spinal cord
Sympathetic is more complex. why?
Innervates smooth muscle, cardiac muscle and glands
Anatomy of the sympathetic division
Preganglionic fibers leave the spinal cord and form the sympathetic trunk
Sympathetic trunk
allows pre-ganglionic axons to travel to spinal nerves that are higher or lower than where they originate
Pathway to the sympathetic trunk
- Preganglionic fiber exits spinal cord
- fibers bass through white ramus communicans
- fibers enter the sympathetic trunk ganglion
White ramus communicans
guides the preganglionic fiber to the sympathetic trunk
Ways fibers form synapses. 3:
- Preganglionic neuron and postganglionic neuron synapse at the same level
(straight to the side at the sympathetic trunk) - Preganglionic neuron and postganglionic neuron synapse at higher or lower level (Travels out to the effector organ - go up or down)
3) Preganglionic neuron and postganglionic neuron synapse at distant collateral ganglion in abdomen and pelvis (no synapse)
Collateral ganglion
Sits next to the sympathetic trunk where it synapses with the postganglionic fiber
Grat rami communicans
Carry postganglionic fibers from sympathetic trunk ganglion to periphery
Pathways to the Head from trunk ganglia
Preganglionic fibers emerge from T1-T4, synapse with postganglionic fibers at superior cervical ganglion of the sympathetic trunk
serves skin and blood vessels of head, stimulate dilator muscles of eyes, inhibits nasal and salivary glands, innervates muscle to upper eyelid, sends branches to heart (increases heart rate)
Pathways to the thorax from trunk ganglia
Preganglionic fibers emerge from T1-T6
Most postganglionic axons pass through cardiac, pulmonary, & esophageal plexuses to effector organ
Travel with parasympathetic postganglionic neurons but they still have opposite effects on the effector organs
Causes airways to dilate and bring in oxygen so that you could supply it to the muscle tissue
Any neurons that synapse in collateral ganglia
Pathways with Synapses in Collateral Ganglia
Form Splanchnic nerves
Greater splanchnic nerve, lesser splanchnic nerve, least splanchnic nerves
Lumbar splanchnic nerves and sacral splanchnic nerves
Pathways to the abdomen
serve the stomach, most of intestines, liver, spleen, and kidneys
Slows them down
pathway to the pelvis
serves the bladder, reproductive organs, distal half of large intestine
What is the general effect of the sympathetic division on abdominopelvic viscera?
Inhibitory effect, slows it down
Visceral reflex arc components
- receptor in viscera
- sensory neurons
- integration center
- motor neurons
- visceral effector
Acetylcholine
The effect is not entirely excitatory or inhibitory → depends on receptor it binds
Released by cholinergic fibers
Receptors that bind…
Nicotinic receptor
muscarinic receptor
Cholinergic fibers
1) All ANS preganglionic axons
2) All parasympathetic postganglionic axons at synapse with effector
Nicotinic receptors
Found on: all postganglionic neurons (sympathetic & parasympathetic), hormone-producing cells of the adrenal medulla, sarcolemma of skeletal muscle cells
Also on the adrenal medulla - produces and releases norepinephrine and epinephrine
Effect: Binding of ACh here is always stimulatory
Depolarization of post ganglionic fibers
Muscarinic Receptors
Found on: all parasympathetic effectors and some sympathetic effectors
Effect: Binding of ACh here is stimulatory or inhibitory
Rest and digest is increased in general
Norepinephrine
Effect is not entirely inhibitory or excitatory → depends on receptor it binds
Released by adrenergic fibers at sympathetic postganglionic axons
Adrenergic Receptors that bind NE
1) Alpha receptors
2) Beta receptors
Norepinephrine
Effect is not entirely inhibitory or excitatory → depends on receptor it binds
Released by adrenergic fibers at sympathetic postganglionic axons
Adrenergic Receptors that bind NE
1) Alpha receptors
2) Beta receptor
Alpha receptors
All sympathetic target organs
Beta receptors
heart, adipose tissue, kidneys, lungs, blood vessels
Can be stimulatory and inhibitory
Dual Innervation
Sympathetic and parasympathetic divisions innervate organs → both send impulses to organ simultaneously
Opposite effects
Whichever is sending more impulses in the same period of time will have a higher influence on the organ
Vasomotor (Sympathetic) Tone:
continuous partial constriction of blood vessels (vaso- blood vessel)
Why is partial constriction (i.e., muscle “tone”) important in muscle tissue?
When you are at rest, including skeletal muscle tissue, it will allow muscle to be responsive to neurotransmitters no matter how much you want it to
If blood pressure is low
Vasomotor fibers will fire more rapidly
muscle contracts → blood vessels constrict
If blood pressure is high
Vasomotor fibers fire less rapidly
muscle relaxes → blood vessels dilate
Parasympathetic Tone:
Present mostly in cardiac muscle tissue, smooth muscle tissue of digestive and urinary organs
Effect: slows heart rate, maintains normal activity of digestive & urinary organs
Unique roles of the sympathetic division
- thermoregulatory response to heat (blood vessels dilate, sweat glands activate)
- Renin released from kidneys (increase blood pressure)
- Metabolic changes (increase metabolic rates in cells, higher blood glucose level, mobilize fats)
parasympathetic division exterts…
highly localized, short-lived control by…
(1) One preganglionic neuron synapses with one or a few postganglionic neurons
(2) All parasympathetic fibers release ACh → quickly broken down by acetylcholinesterase
Sympathetic division exerts…
diffuse (spread out), long-lasting control by…
(1) Preganglionic neurons synapse with multiple postganglionic neurons
(2) NE and epinephrine prolong effects of sympathetic division activation
Anterior hypothalamic areas…
oversee parasympathetic division
Posterior hypothalamic areas
oversee sympathetic division
Hypertension
High blood pressure
overactive sympathetic vasoconstrictor response
heart must work harder to circulate blood through narrow blood vessels
heart disease, enlarged arteries, kidney failure
Adrenergic-receptor blocking drugs
Raynaud’s Disease
exaggerated vasoconstriction response due to cold or emotional stress
skin of fingers and toes becomes pale, temporarily decreased blood flow
Skin can eventually become cyanotic (blue), painful
Tissue not dead, but veryyyy oxygen deprived
When blood returns, it is normal and will also stimulate nociceptors and you will feel pain
Could be gangrene - black tissue; no saving it
Autonomic dysreflexia
Affects individuals who are quadriplegic or have spinal cord injuries above T6
Usually triggered by some type of pain stimulus to skin or overfilled visceral organ
More than 80% of cases are because of an overfilled bladder of autonomic neurons
Effect: arterial blood pressure skyrockets
Can rupture blood vessels in brain causing stroke
Symptoms: headache, flushed face, sweating above injury, cold/clammy skin below injury
