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What is the main source of content (including visual images) for this presentation?
What is the main source of content (including visual images) for this presentation?
Human Anatomy 9th Ed.
Besides the required textbook, where can you find additional resources for the content?
Besides the required textbook, where can you find additional resources for the content?
Online materials that come with the textbook.
What is the primary function of the somatic motor system?
What is the primary function of the somatic motor system?
The autonomic nervous system uses a single motor neuron to reach its target structure.
The autonomic nervous system uses a single motor neuron to reach its target structure.
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Which of the following is NOT a target of the autonomic nervous system?
Which of the following is NOT a target of the autonomic nervous system?
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Where is the cell body of the somatic motor neuron located?
Where is the cell body of the somatic motor neuron located?
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What neurotransmitter does the somatic motor neuron use at its synapse with skeletal muscle?
What neurotransmitter does the somatic motor neuron use at its synapse with skeletal muscle?
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Which of the following is NOT a characteristic of the sympathetic nervous system?
Which of the following is NOT a characteristic of the sympathetic nervous system?
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Where are the cell bodies of preganglionic sympathetic neurons located?
Where are the cell bodies of preganglionic sympathetic neurons located?
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What neurotransmitter does the postganglionic sympathetic neuron typically use at its synapse with the target organ?
What neurotransmitter does the postganglionic sympathetic neuron typically use at its synapse with the target organ?
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Which of these are directly innervated by preganglionic sympathetic axons?
Which of these are directly innervated by preganglionic sympathetic axons?
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What is the primary function of the parasympathetic nervous system?
What is the primary function of the parasympathetic nervous system?
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What type of neurotransmitter is generally associated with the parasympathetic nervous system?
What type of neurotransmitter is generally associated with the parasympathetic nervous system?
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Parasympathetic neurons typically have short postganglionic neurons.
Parasympathetic neurons typically have short postganglionic neurons.
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Where do the preganglionic fibers of the parasympathetic nervous system run via?
Where do the preganglionic fibers of the parasympathetic nervous system run via?
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What is the general name given to the parasympathetic outflow originating from the brain?
What is the general name given to the parasympathetic outflow originating from the brain?
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What is the other major outflow of the parasympathetic nervous system, originating from the sacral region?
What is the other major outflow of the parasympathetic nervous system, originating from the sacral region?
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The sympathetic outflow is only responsible for innervation of the internal organs.
The sympathetic outflow is only responsible for innervation of the internal organs.
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What is the primary effect of the sympathetic nervous system on heart rate?
What is the primary effect of the sympathetic nervous system on heart rate?
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What effect does the sympathetic nervous system have on pupil size?
What effect does the sympathetic nervous system have on pupil size?
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How does the sympathetic nervous system influence the digestive and urinary tracts?
How does the sympathetic nervous system influence the digestive and urinary tracts?
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What is the general effect of the parasympathetic nervous system on heart rate?
What is the general effect of the parasympathetic nervous system on heart rate?
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What is the primary effect of the parasympathetic nervous system on pupil size?
What is the primary effect of the parasympathetic nervous system on pupil size?
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What is the primary function of autonomic plexuses?
What is the primary function of autonomic plexuses?
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All autonomic plexuses contain both sympathetic and parasympathetic fibers.
All autonomic plexuses contain both sympathetic and parasympathetic fibers.
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Where are "chain" and "paravertebral" ganglia located?
Where are "chain" and "paravertebral" ganglia located?
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White rami communicantes contain postganglionic fibers traveling to peripheral structures.
White rami communicantes contain postganglionic fibers traveling to peripheral structures.
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Gray rami communicantes contain preganglionic fibers traveling to sympathetic trunk ganglia.
Gray rami communicantes contain preganglionic fibers traveling to sympathetic trunk ganglia.
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What are the three pathways that preganglionic sympathetic axons can follow?
What are the three pathways that preganglionic sympathetic axons can follow?
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What does the term "visceral reflex" refer to?
What does the term "visceral reflex" refer to?
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Both the sympathetic and parasympathetic nervous systems can influence the same target organ.
Both the sympathetic and parasympathetic nervous systems can influence the same target organ.
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What is the main function of the sympathetic nervous system on blood vessels?
What is the main function of the sympathetic nervous system on blood vessels?
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The sympathetic nervous system does not innervate the sweat glands.
The sympathetic nervous system does not innervate the sweat glands.
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The parasympathetic nervous system does not innervate the arrector pili muscles.
The parasympathetic nervous system does not innervate the arrector pili muscles.
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Study Notes
Autonomics - Visceral Motor System
- The autonomic nervous system (ANS) controls visceral functions, including smooth muscle, cardiac muscle, and glands
- The ANS is a two-neuron system:
- Preganglionic neurons (preganglionic axons) originate in the CNS, extend to autonomic ganglia, and release acetylcholine
- Postganglionic neurons (postganglionic axons) extend from the autonomic ganglia to the target, and release neurotransmitters.
- The ANS has two primary divisions:
- Sympathetic division
- Parasympathetic division
Somatic vs. Autonomic Systems
- The somatic motor system uses a single neuron to extend from the Central Nervous System (CNS) to the skeletal muscle
- The autonomic system uses a chain of two neurons to extend from the CNS to the target (smooth muscle or gland)
- a presynaptic (preganglionic) neuron
- a postsynaptic (postganglionic) neuron
Somatic Motor
- The brachial plexus is a network of nerves.
- Major nerves in the upper limb include the axillary, radial, musculocutaneous, ulnar, and median nerves.
Visceral Motor
- Cranial nerves (III, VII, IX, X) are part of the parasympathetic system.
- Sacral outflow (S2-S4) involves the parasympathetic system.
Visceral Motor Pathways
- Parasympathetic pathways often use cranial nerve pathways.
- The preganglionic fibers, which originate in the cranial nucleus, synapse with postganglionic neurons in ganglia located near the target organ.
- The preganglionic fibers of the parasympathetic nervous system are long, myelinated axons.
- The postganglionic fibers are short, unmyelinated axons.
- The neurotransmitter in both divisions is acetylcholine
Introduction to the Autonomic Nervous System (ANS)
- The ANS is a component of the peripheral nervous system (PNS).
- It regulates visceral functions like heart rate, blood pressure, digestion, and urination.
- The ANS consists of sensory and motor components.
- Sensory (afferent) : carries information to the CNS from visceral organs.
- Motor (efferent) : controls visceral organs.
- Somatic: controls skeletal muscles.
- Visceral: controls smooth muscle, cardiac muscle, and glands.
Two Divisions of the ANS
-
Sympathetic Division: "Fight, flight, or fright" response
- Originates in the thoracic and lumbar regions of the spinal cord.
- Has a chain of ganglia along the spinal cord
- Long postganglionic fibers.
- Typically has norepinephrine as the neurotransmitter, with some acetylcholine release at some synapses.
-
Parasympathetic: "Rest and digest."
- Originates in the brain stem and sacral spinal cord
- Short postganglionic fibers.
- Typically uses acetylcholine as the neurotransmitter
Sympathetic Division
- Increases heart rate, breathing rate and blood flow to skeletal muscles.
- Dilates pupils and airways
- Inhibits motility of the digestive and urinary tracts.
Parasympathetic Division
- Heart rate and breathing are at low-normal levels.
- Gastrointestinal tract digests food.
- Pupils are constricted.
Parasympathetic Pathways
- Craniosacral outflow, meaning nerves originate in the brain stem and the sacral area of the spinal cord.
- The postganglionic neurons are located in or near the target organ, and the neurotransmitter is acetylcholine.
- The parasympathetic system does not contain nerves that innervate the body wall or limbs.
Cranial Outflow
- Originates in the brain, and innervates organs of the head, neck, thorax, and abdomen.
- Pre-ganglionic fibers run via cranial nerves III, VII, IX, and X.
- Synapse with second motor neurons in head ganglia or in ganglia in the walls of target organs.
- Pre-ganglionic fibers travel with cranial nerve X and pass through several autonomic plexuses.
Sacral Outflow
- Originates in the sacral spinal cord and innervates the lower abdominal and pelvic organs.
- Preganglionic fibers exit the spinal cord (S2-S4) and form pelvic splanchnic nerves.
Distribution of Parasympathetic Nerve Fibers
- Most of the innervation occurs through cranial nerves
- Acetylcholine is the main neurotransmitter
- Innervates many organs in the body
Autonomic Plexuses
- Networks of parasympathetic and sympathetic fibers
- All autonomic plexuses contain both sympathetic and parasympathetic fibers
- Ganglia in these networks are almost exclusively sympathetic
Sympathetic Pathways
- Three main pathways:
- Pathway 1: Synapses on the same level in that sympathetic trunk
- Pathway 2: Synapse at a higher or lower level in the sympathetic trunk
- Pathway 3: Passes through the sympathetic trunk and synapses in a collateral ganglion.
- The pathways involve white rami communicantes, spinal nerves (ventral rami), and gray rami communicantes.
Collateral (Prevertebral) Ganglia
- Unpaired ganglia arranged anterior to the vertebral column.
- Located mainly in the abdomen and pelvis (on or near the surface of the aorta)
White and Gray Rami Communicantes
- White rami are preganglionic fibers
- Connect spinal nerves to the sympathetic trunk
- Gray rami are postganglionic fibers
- Return to spinal nerves to innervate peripheral tissues.
Visceral Reflexes
- Are involuntary reactions to changes in internal organs.
- Involve the CNS and sensory impulses carried on visceral fibers.
- Baroreceptors are sensory receptors that detect pressure changes
- The glossopharyngeal nerve (CN IX) carries information about changes in blood pressure.
Comparison of Sympathetic and Parasympathetic Divisions Effects on Organs
- Various organs have distinct responses based on sympathetic and parasympathetic inputs.
Important Considerations
- The sympathetic branch of the ANS innervates superficial and deep structures of the body.
- Sympathetic innervation leads to nervous system responses such as sweating, pupil dilation, goosebumps, etc.
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Description
Test your understanding of the autonomic and somatic motor systems, including their structures and functions. This quiz covers key concepts such as the two-neuron system of the autonomic nervous system and the differences between somatic and autonomic pathways.
