Lecture 11 - PNS Flashcards
Divisions of PNS
- SNS
- PNS
- ENS
SNS
- -consciously controlled
- -voluntary
- -sensory receptors + motor neurons to skeletal muscles
Somatic nervous system
ANS
-involuntary
-sensory from visceral organs
-motor to smooth mm,
cardiac mm & glands
Autonomic nervous system
ENS
- -involuntary
- -sensory from chemical changes in GI tract and stretching it
- -motor to GI smooth muscle
Enteric nervous system
Divisions of ANS
- sympathetic
“fight or flight” - parasympathetic
“rest and digest”
sympathetic nervous system
- increased alertness and metabolic activities in
order to prepare the body for an emergency situation
parasympathetic nervous system
- activities conserve and restore body energy
- most output is to GI tract and respiratory tract
Autonomic Tone
- most organs receive innervation from both divisions of the ANS, which typically work in opposition to one another
- autonomic tone is the balance between sympathetic and parasympathetic activity
What regulates autonomic tone?
Hypothalamus
structures only receive sympathetic innervation:
- sweat glands
- arrector pili muscles
- kidneys
- spleen
- most blood vessels
- adrenal medullae
-although they don’t have opposition from the parasymp nervous system, they still exhibit a range in responses: an increase in sympathetic tone has one effect and a decrease in sympathetic tone has the opposite effect
Sympathetic responses
- during physical or emotional stress, the sympathetic division dominates the parasympathetic system
- high sympathetic tone favors body functions that can support vigorous physical activity and rapid production of ATP
- and reduces body functions that favor storage of energy
- emotions can stimulate sympathetic division
(fear, embarrassment, rage)
Sympathetic responses
Fight or flight:
- pupils dilate
- heart rate, force of heart contraction and BP increases
- airways dilate (faster movement of air into and out of lungs)
- BV to skeletal muscles dilate
- BV to cardiac muscles dilate
- BV to GI tract constrict
- BV to kidneys constrict
- BV to liver dilate
- BV to adipose tissue dilate
Parasympathetic responses
- rest and digest
- parasympathetic responses support body functions that conserve and restore body energy during times of rest and recovery
- Salivation
- Lacrimation
- Urination
- Digestion
- Defecation
- decreased heart rate
- decreased diameter of airways
- decreased diameter of pupils
Somatic Nervous System
Sensory Input
- from receptors for somatic senses (tactile, thermal,
pain, proprioceptive sensations) and from
receptors for special senses (sight, hearing, taste, smell, equilibrium) - these are consciously perceived
Autonomic Nervous System
Sensory input
- from interoreceptors (sensory receptors located in BVs, visceral organs, mm and nn that monitor conditions in the internal environment)
- not usually consciously perceived
Somatic Nervous System
Control of motor output
-Primary motor area of cerebral cortex
-voluntary (with contributions from basal nuclei, cerebellum, brainstem and SC)
Autonomic Nervous System
Control of motor output
- involuntary control from hypothalamus
Somatic Nervous System
Motor neuron pathway
- one neuron pathway
- somatic motor neuron goes from CNS to skeletal muscle
Autonomic Nervous System
Motor neuron pathway
- Two neuron pathway
- to chromaffin cells in adrenal medulla
Somatic Nervous System
Neurotransmitters
-somatic motor neurons only release ACh
Autonomic Nervous System
Neurotransmitters
- autonomic motor neurons release ACh or NE
- hormones: NE (norepinephrine) & Epinephrine
Somatic Nervous System
Effectors
- skeletal muscle
Autonomic Nervous System
Effectors
- smooth muscle, cardiac muscle or glands
Somatic Nervous System
Responses
- contraction of skeletal muscle
Autonomic Nervous System
Responses
- contraction or relaxation of smooth muscle
- increase or decreased rate & force of contraction of cardiac muscle
- increased or decreased secretion of glands
Anatomy of autonomic motor pathways
The main parts:
- Preganglionic neuron
- Postganglionic neuron
- Autonomic ganglion
Preganglionic neuron
two divisions
- the first neuron in an autonomic motor pathway
- cell body is in CNS
- axon is a type B fiber
- usually goes to an autonomic ganglion and synapses with a postganglionic neuron
Thoracolumbar division/sympathetic
Craniosacral division/parasympathetic
Thoracolumbar division/sympathetic
- in the sympathetic division, preganglionic neurons have their cell bodies in the lateral horns of gray matter in T1 to L2 (sometimes L3)
Craniosacral division/parasympathetic
- in the parasympathetic division, cell bodies of
preganglionic neurons are in the nuclei of 4 cranial nerves (10, 9, 7, 3) and in the lateral gray matter of S2 to S4
In the sympathetic system, the preganglionic axons
travel out from the SC with
spinal nerves T1-L2 (L3)
In the parasympathetic, preganglionic axons travel out with
4 cranial nn
CNIII
CNVII
CN IX
CN X
&
Sacrum
S2
S3
S4
Postganglionic neuron
- the second neuron in an autonomic motor pathway
- in the PNS
- cell body is in an autonomic ganglion
- type C fiber
- terminates in a visceral effector
Autonomic Ganglia
- Where the preganglionic and post ganglionic neurons synapse
Sympathetic division
- the sympathetic division has 2 different groups of ganglia:
- Sympathetic trunk ganglia
- Prevertebral ganglia
- Sympathetic trunk ganglia
- aka vertebral chain ganglia
- aka paravertebral ganglia
- lie in a vertical row on either side of vertebral column
- the post ganglionic axons from here innervate organs above the diaphragm
- the ones in the neck have specific names:
1. superior cervical ganglia
2. middle cervical ganglia
3. inferior cervical ganglia
- Prevertebral ganglia
- aka collateral ganglia
- they lie anterior to the vertebral column
- their post ganglionic axons innervate organs below the diaphragm
5 major Prevertebral ganglia
- Celiac ganglion
- Superior mesenteric ganglion
- Inferior mesenteric ganglion
- Aorticorenal ganglion
- Renal ganglion
Autonomic Ganglia
Where the preganglionic and post ganglionic neuron synapse
