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Questions and Answers
What triggers sympathetic reactions in the body?
What triggers sympathetic reactions in the body?
Which of the following is a primary function of the parasympathetic nervous system?
Which of the following is a primary function of the parasympathetic nervous system?
What does the somatic nervous system primarily control?
What does the somatic nervous system primarily control?
How does the parasympathetic nervous system typically act compared to the sympathetic system?
How does the parasympathetic nervous system typically act compared to the sympathetic system?
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Which physiological response is NOT associated with parasympathetic activity?
Which physiological response is NOT associated with parasympathetic activity?
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What is the role of afferent impulses in the autonomic nervous system?
What is the role of afferent impulses in the autonomic nervous system?
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What characterizes the enteric nervous system?
What characterizes the enteric nervous system?
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What triggers the increase in blood pressure according to the reflex arc of the autonomic nervous system?
What triggers the increase in blood pressure according to the reflex arc of the autonomic nervous system?
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Which neurotransmission process is demonstrated in the autonomic nervous system?
Which neurotransmission process is demonstrated in the autonomic nervous system?
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What comprises the reflex arcs of the autonomic nervous system?
What comprises the reflex arcs of the autonomic nervous system?
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Study Notes
Autonomic Nervous System
- The nervous system is divided into two main divisions: central nervous system (CNS) and peripheral nervous system (PNS).
- The CNS includes the brain and spinal cord.
- The PNS encompasses nerves located outside the brain and spinal cord.
- The autonomic nervous system (ANS) is largely independent (autonomous) in its functions, not under direct conscious control.
- The ANS primarily handles visceral functions such as heart rate, blood flow, and digestion.
ANS Structure
- The ANS carries nerve impulses from the CNS to effector organs via preganglionic and postganglionic neurons.
- Ganglia act as relay stations, transmitting impulses between preganglionic and postganglionic neurons.
- The sympathetic nervous system has short preganglionic and long postganglionic fibers.
- The parasympathetic nervous system has long preganglionic and short postganglionic fibers.
Functions of the Sympathetic Nervous System
- Increases heart rate and contractility, thus elevating blood pressure.
- Constricts blood vessels in skin, mucous membranes, and splanchnic area, while dilating skeletal muscle vessels.
- Dilates pupils.
- Bronchodilation (widening of the bronchial tubes).
- Inhibits salivation.
- Decreases gastrointestinal (GI) motility.
- Stimulates ejaculation.
- Inhibits bladder contraction.
- Stimulates glucose production and release.
- Contributes to the "fight-or-flight" response during emergencies.
Functions of the Parasympathetic Nervous System
- Maintains homeostasis within the body.
- Primarily involved in functions such as digestion and waste elimination.
- Generally opposes the actions of the sympathetic system in "rest-and-digest" situations.
- Pupil contraction (miosis).
- Bronchoconstriction (narrowing of bronchial tubes).
- Stimulating digestion.
- Stimulating the gallbladder and bladder.
- Relaxing the rectum.
- Causing vaginal lubrication and facilitating erection.
Enteric Nervous System (ENS)
- ENS is a portion of the peripheral nervous system in the gastrointestinal tract.
- The ENS is responsible for motility, exocrine and endocrine secretions, and microcirculation in the gastrointestinal tract.
Somatic Nervous System
- The somatic nervous system carries motor and sensory information.
- The system mediates voluntary muscle movements.
- It also receives sensory information from the skin, sensory organs, and skeletal muscles.
Reflex Arc
- The ANS and the somatic nervous system work together in reflex arcs.
- Sensory input from the body travels to integrating centers in the CNS, triggering a response by the CNS.
Neurotransmitters
- The primary chemical signals in the ANS are acetylcholine and norepinephrine, involved in various functions.
- The ANS has cholinergic and adrenergic neurons based on neurotransmitter release (ACh or norepinephrine, respectively).
- Acetylcholine mediates transmission across autonomic ganglia in both sympathetic and parasympathetic systems.
- Neurotransmission involves synthesis, storage, release, receptor binding, degradation, and recycling of neurotransmitters.
Cholinergic Receptors
- Cholinergic receptors are categorized as muscarinic and nicotinic.
- Muscarinic receptors have high affinity for muscarine, while low for nicotine.
- Nicotinic receptors have high affinity for nicotine, and low affinity for muscarine.
- Cholinergic receptors are located in sympathetic and parasympathetic nervous systems.
Cholinergic Agonists
- Cholinergic agonists mimic the action of acetylcholine.
- Examples include acetylcholine, carbachol, and bethanechol.
Cholinergic Antagonists
- Cholinergic antagonists block the action of acetylcholine.
- Examples include atropine.
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Description
Explore the essential elements of the autonomic nervous system (ANS), focusing on its structure and functions. Understand the differences between the sympathetic and parasympathetic systems and their roles in managing involuntary bodily functions such as heart rate and digestion.