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Questions and Answers
What is the primary function of the autonomic nervous system (ANS)?
Regulation of the cardiovascular, respiratory, digestive, urinary, and reproductive organs.
Which types of fibers are commonly associated with the ANS?
The sympathetic chain of ganglia extends only from the thoracic region to the lumbar region of the spinal cord.
False
What response is activated under extreme threats involving the sympathetic nervous system?
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Where do preganglionic axons in a splanchnic nerve often travel?
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The axons in the paravertebral sympathetic chain of ganglia may travel __________ or __________ to a nearby or distant ganglion.
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What is the role of baroreceptors in the ANS?
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Match the ganglia with their associated cervical levels:
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Study Notes
Autonomic Nervous System (ANS)
- The ANS regulates vital functions like cardiovascular, respiratory, digestive, urinary, and reproductive systems.
- It helps maintain internal balance (homeostasis) by adjusting to external and internal disturbances.
- The ANS innervates:
- Smooth muscle
- Cardiac muscle
- Glandular epithelium
- Examples of ANS regulation:
- Blood pressure: Baroreceptors detect pressure changes and trigger ANS adjustments to restore normal levels.
- Pupil size: ANS controls pupil diameter in response to light intensity.
- "Fight or Flight": Sympathetic nervous system activation triggers a heightened response to threats.
General Organization
- The ANS consists of a two-neuron motor pathway:
- Preganglionic neuron: Originates in the central nervous system.
- Postganglionic neuron: Synapses with the preganglionic neuron and innervates the target organ.
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Sympathetic Nervous System (SNS):
- Pre-ganglionic neurons originate in the spinal cord segments T1-L2.
- Preganglionic axons: Short, myelinated (B fibers), travel through white rami communicantes.
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Postganglionic axons: Long, unmyelinated (C fibers), travel through gray rami communicantes.
- Most postganglionic fibers innervate skin, muscles, and joints.
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Parasympathetic Nervous System (PNS):
- Pre-ganglionic neurons originate in the brainstem and sacral spinal cord.
- Preganglionic axons: Long, myelinated.
- Postganglionic axons: Short, unmyelinated.
Sympathetic Nervous System (SNS)
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Sympathetic Chains:
- Chains of ganglia extend along the spinal cord from cervical to coccygeal levels.
- This arrangement allows preganglionic neurons in the thoracic and upper lumbar segments to innervate all body segments.
- Fusion during development creates larger ganglia:
- Superior Cervical ganglia: C1-C4
- Middle Cervical ganglia: C5-C6
- Inferior Cervical ganglia: C7-C8
- Stellate ganglion: Fusion of Inferior Cervical ganglia and T1.
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Splanchnic Nerves:
- Preganglionic axons in the splanchnic nerves may synapse in prevertebral ganglia or travel through autonomic plexuses to end in more distant ganglia.
Sensory Receptors
- Sensory fibers: Carry signals from receptors in the viscera, often triggered by changes in internal environments.
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Sensory functions:
- Trigger reflexes, like changes in heart rate due to blood pressure.
- Evoke sensory experiences: Pain, hunger, thirst, nausea, organ distension.
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Description
Explore the Autonomic Nervous System (ANS) and its crucial role in regulating vital functions such as cardiovascular and respiratory systems. This quiz delves into the organization of the ANS, its components, and examples of its regulation mechanisms like blood pressure and pupil size. Test your understanding of how the ANS maintains homeostasis and responds to threats.
