Phys 1 Flashcards
The ANS consists of motor neurons that:
- Innervate smooth and cardiac muscle and glands
- Make adjustments to ensure homeostatic environment
- Operate via involuntary control
- Have viscera as most of their effectors
Role of the Parasympathetic Division
“rest and digest”
- keeping body energy use low
- the D activities: digestion, defecation, diuresis
- BP, HR, and RR are low
- GI activity is high
- skin is warm and pupils are constricted
Parasympathetic Division is illustrated by…
a person who reads after a meal
Role of the Sympathetic Division
“fight or flight”
- the E activities: exercise, excitement, emergency, and embarrassment
- blood flow to organs is reduced, flow to muscles is increased
- HR increases, breathing is rapid and deep
- skin is cold and sweaty, pupils dilated
Sympathetic Division is illustrated by…
a person who is threatened
Somatic effectors
skeletal muscle
ANS effectors
- cardiac muscle
- smooth muscle
- glands
Characteristics of somatic nervous system neurons
- Thick, heavily myelinated
- One neuron leaves CNS, reaches effector
- Without ganglia
Characteristics of autonomic nervous system neurons
- Preganglionic thinly myelinated
- Two neuron systems
- Ganglion
- Postganglionic neuron usually unmyelinated
All somatic motor neurons release…
Acetylcholine (ACh), which has an excitatory effect
In the ANS, what do the fibers release (preganglionic vs. postganglionic)?
- Preganglionic fibers release ACh
- Postganglionic fibers release norepinephrine or ACh and effect is either stimulatory or inhibitory
Comparison of Somatic and ANS
- Higher CNS centers regulate and coordinate both somatic and visceral activities
- There is overlap and integration of both systems
Parasympathetic Outflow
- Cranial outflow via cranial nerves
- Sacral outflow forming splanchnic nerves
Parasympathetic cranial outflow - oculomotor (CN III)
- Synapse in ciliary ganglion
- Sphincter of iris: contraction or miosis
- Ciliary muscles: contract- accommodation
Parasympathetic cranial outflow - facial (CN VII)
- Pterygopalatine: lacrimal glands-contraction
- Sphenopalatine ganglia: nasal glands, nasal mucosa- contraction
- Submandibular ganglia: salivary glands (submandibular and sublingual)- contraction
Parasympathetic cranial outflow - glossopharyngeal (CN IX)
Otic ganglia: parotid salivary glands- contraction
Parasympathetic cranial outflow -vagus (CN X)
- 90% of preganglionic PSNS fibers
- serve neck and organs of thoracic and abdominal cavities
- via nerve plexuses
*when in doubt, choose vagus.
What organs does the parasympathetic cranial outflow go to?
- heart
- lung
- gallbladder
- stomach
- pancreas
- SI and proximal colon
Parasympathetic cranial outflow: heart
- locations
- effects
- SA node, A and V, SA node and Purkinje fibers
- to reduce HR, contractility and conduction velocity
Parasympathetic cranial outflow: lung
-effects
bronchial smooth muscle contraction
Parasympathetic cranial outflow: gallbladder
-effect
Contraction
Parasympathetic cranial outflow: stomach
-effects
- increase gastric secretions & motility
- relax sphincters
Parasympathetic cranial outflow: pancreas
-effects
increase secretions
Parasympathetic cranial outflow: SI and proximal colon
-effects
increase secretions & motility
relax sphincters
ParasympatheticOutflow: Sacral
- origin
- exit
- branch
- synapse
- Originate in lateral gray matter of spinal cord
- Exit via ventral root
- Branch to form pelvic splanchnic nerves (which pass thru inferior hypogastric plexus)
- Synapse in intramural ganglia of organ
Parasympathetic sacral outflow: distal colon
-effects
- increase secretions & motility
- relax sphincters
Parasympathetic sacral outflow: ureter
-effects
Contractions
Parasympathetic sacral outflow: urinary bladder
-effects
- detrusor muscle contraction
- relax sphincter
Parasympathetic sacral outflow: reproductive organs
-effects
clitoris and penis vasodilation
Sympathetic outflow - preganglionic fibers arise from…
- All SNS preganglionic fibers arise from preganglionic cell bodies in spinal cord segments T1 – L2 (AKA thoracolumbar outflow)
- Sympathetic neurons form the lateral horns of gray matter
Sympathetic outflow - preganglionic fibers exit…
- SNS preganglionic fibers exit spinal cord via ventral root
- Pass thru white rami communicans
- Enter paravertebral ganglia of sympathetic trunk
Three possible sympathetic preganglionic pathways
- Synapse in adjacent ganglion
- Ascend or descend to synapse in different ganglion
- Exit without synapsing to form splanchnic nerves then synapse in prevertebral ganglia
If the SNS preganglionic pathway exits via grey communicans…
- Synapse at local, adjacent ganglion
- Postganglionic nerve exits with adjacent SN via ramus
- Distributed to sweat glands, arrector pili MM, and smooth muscle of blood vessels
Pathway of sympathetic preganglionic fibers of T1 –T5
- Exit via white communicans
- Ascend or descend chain to synapse in different ganglion
- Postganglionic nerve exits with adjacent SN via ramus
- Serve head, neck, heart, and lungs
Pathway of sympathetic preganglionic fibers of T5-L2
-Exit via white communicans without synapsing
-These fibers form splanchnic nerves (greater, lesser, and
lumbar)
- Synapse in a collateral or prevertebral ganglion
- -Celiac ganglion
- -Superior mesenteric ganglion
- -Inferior mesenteric ganglion
- Postganglionic fiber serves target
- -Liver, GI tract, kidney, reproductive organs
