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Questions and Answers
Which division of the autonomic nervous system typically increases heart rate?
What type of receptors are primarily engaged by autonomic sensory neurons to monitor internal conditions?
Which part of the body regulates autonomic nervous system reflexes?
Which nervous system is NOT a division of the peripheral nervous system?
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What is the role of autonomic motor neurons in the autonomic nervous system?
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What is the role of the preganglionic neuron in the autonomic motor pathway?
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Which of the following statements best describes the difference between somatic and autonomic motor neurons?
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What structural feature differentiates postganglionic neurons from preganglionic neurons?
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Which type of muscle continues to contract rhythmically even if its nerve supply is damaged?
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In which situation do preganglionic neurons synapse with specialized cells rather than an autonomic ganglion?
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Study Notes
The Autonomic Nervous System and Homeostasis
- The autonomic nervous system (ANS) regulates involuntary functions like smooth muscle, cardiac muscle, and gland activity.
- The ANS operates via reflex arcs, with two divisions: sympathetic and parasympathetic.
- Most body organs have dual innervation, meaning they receive input from both the sympathetic and parasympathetic systems.
- Autonomic motor pathways have two neurons: preganglionic and postganglionic.
- Preganglionic neurons originate in the brain or spinal cord and synapse with postganglionic neurons in autonomic ganglia.
- Interoceptors: Sensory receptors in blood vessels, visceral organs, muscles, and the nervous system monitor internal conditions.
Anatomy of Autonomic Motor Pathways
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Sympathetic Division (Thoracolumbar Division):
- Preganglionic neurons originate in the spinal cord's thoracic and upper lumbar segments (T1-L2).
- Sympathetic ganglia are located along the spinal cord (sympathetic trunk ganglia) or near major abdominal arteries (prevertebral ganglia).
- Short preganglionic axons and long postganglionic axons.
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Parasympathetic Division (Craniosacral Division):
- Preganglionic neurons originate in the brainstem and sacral spinal cord segments (S2-S4).
- Parasympathetic ganglia are located near or within the target organs.
- Long preganglionic axons and short postganglionic axons.
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Neurotransmitters:
- Preganglionic neurons in both divisions release acetylcholine (ACh).
- Postganglionic neurons of the sympathetic division mostly release norepinephrine (NE).
- Postganglionic neurons of the parasympathetic division release acetylcholine (ACh).
Sympathetic Responses (Fight-or-Flight)
- General effects: Increased alertness, heart rate, blood pressure, breathing, and blood flow to skeletal muscles. Decreased blood flow to digestive organs, and urine production.
- Pupil dilation
- Bronchodilation (widening of airways)
- Increased heart rate and force of contraction
- Glycogenolysis (breakdown of glycogen into glucose)
- Lipolysis (breakdown of triglycerides into fatty acids)
- Increased blood glucose levels
- Inhibition of digestive activities
Parasympathetic Responses (Rest-and-Digest)
- General effects: Promotes relaxation, digestion, and energy conservation.
- Increased salivation, lacrimation, urination, digestion, and defecation (SLUDD)
- Pupil constriction
- Decreased heart rate
- Bronchoconstriction (narrowing of airways)
Additional Notes
- Dual Innervation: Most organs receive both sympathetic and parasympathetic input.
- Hypothalamus: Plays a major role in regulating the ANS.
- Adrenal Medulla: Secretes epinephrine and norepinephrine, enhancing and prolonging sympathetic responses.
- Somatic vs. Autonomic Nervous System: The somatic nervous system controls voluntary muscle movement, while the autonomic nervous system controls involuntary functions.
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Description
Explore the intricacies of the autonomic nervous system, including its structure, function, and role in homeostasis. Understand the sympathetic and parasympathetic divisions along with the pathways involved in autonomic motor function. This quiz will help reinforce your knowledge of the ANS and its impact on involuntary bodily functions.
