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Questions and Answers
What type of nerve fiber is responsible for skeletal muscle control?
What type of nerve fiber is responsible for skeletal muscle control?
Which fiber is associated with sending signals to sweat glands?
Which fiber is associated with sending signals to sweat glands?
What is the role of the white ramus in the sympathetic nerve system?
What is the role of the white ramus in the sympathetic nerve system?
Which of the following is directly involved in regulating blood vessel diameter?
Which of the following is directly involved in regulating blood vessel diameter?
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Which structure contains the soma of the somatic motor neuron?
Which structure contains the soma of the somatic motor neuron?
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Which cranial nerve is associated with the ciliary ganglion?
Which cranial nerve is associated with the ciliary ganglion?
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The lacrimal gland receives parasympathetic innervation from which cranial nerve?
The lacrimal gland receives parasympathetic innervation from which cranial nerve?
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Which cellular structure is involved in the control of the submandibular salivary gland?
Which cellular structure is involved in the control of the submandibular salivary gland?
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Which nerve is responsible for the parasympathetic supply to the parotid gland?
Which nerve is responsible for the parasympathetic supply to the parotid gland?
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Parasympathetic fibers that control various glands arise from which spinal levels?
Parasympathetic fibers that control various glands arise from which spinal levels?
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Which division of the autonomic nervous system reduces blood flow to the skin and digestive tract?
Which division of the autonomic nervous system reduces blood flow to the skin and digestive tract?
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What state is associated with the parasympathetic division?
What state is associated with the parasympathetic division?
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What maintains smooth muscle tone in the intestines?
What maintains smooth muscle tone in the intestines?
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What is the primary role of sympathetic tone in the autonomic nervous system?
What is the primary role of sympathetic tone in the autonomic nervous system?
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Which anatomical component is essential for the autonomic output pathways?
Which anatomical component is essential for the autonomic output pathways?
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What neurotransmitter is primarily involved in the somatic motor pathway?
What neurotransmitter is primarily involved in the somatic motor pathway?
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What occurs when the sympathetic division excites the heart?
What occurs when the sympathetic division excites the heart?
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Where are the control nuclei for the autonomic nervous system primarily located?
Where are the control nuclei for the autonomic nervous system primarily located?
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Which statement best describes the difference between the autonomic and somatic pathways?
Which statement best describes the difference between the autonomic and somatic pathways?
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What is an effect of parasympathetic activation on heart rate?
What is an effect of parasympathetic activation on heart rate?
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Which neurotransmitter is secreted by all preganglionic neurons in both divisions of the ANS?
Which neurotransmitter is secreted by all preganglionic neurons in both divisions of the ANS?
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What type of receptors are found on all cardiac muscle, smooth muscle, and gland cells?
What type of receptors are found on all cardiac muscle, smooth muscle, and gland cells?
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Norepinephrine primarily influences what type of receptors?
Norepinephrine primarily influences what type of receptors?
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Which type of adrenergic receptors are usually inhibitory?
Which type of adrenergic receptors are usually inhibitory?
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How do sympathetic effects on glandular secretion typically occur?
How do sympathetic effects on glandular secretion typically occur?
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In dual innervation, the parasympathetic and sympathetic divisions have what type of effects?
In dual innervation, the parasympathetic and sympathetic divisions have what type of effects?
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Which organ primarily receives only sympathetic fibers?
Which organ primarily receives only sympathetic fibers?
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What is the effect of increased firing frequency in sympathetic nerve fibers on blood vessels?
What is the effect of increased firing frequency in sympathetic nerve fibers on blood vessels?
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What type of neurotransmitter is released by sympathetic fibers that causes vasodilation?
What type of neurotransmitter is released by sympathetic fibers that causes vasodilation?
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Which part of the brain is the major control center for visceral motor functions?
Which part of the brain is the major control center for visceral motor functions?
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What characterizes cooperative effects between the sympathetic and parasympathetic systems?
What characterizes cooperative effects between the sympathetic and parasympathetic systems?
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Which reflexes are integrated in the spinal cord related to autnomic control?
Which reflexes are integrated in the spinal cord related to autnomic control?
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Which class of receptors responds to acetylcholine in an excitatory manner?
Which class of receptors responds to acetylcholine in an excitatory manner?
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What characterizes the preganglionic fibers of the sympathetic division?
What characterizes the preganglionic fibers of the sympathetic division?
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What type of neurons innervate smooth muscle and glands in the digestive tract?
What type of neurons innervate smooth muscle and glands in the digestive tract?
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What type of communication occurs between the sympathetic ganglia and spinal nerves?
What type of communication occurs between the sympathetic ganglia and spinal nerves?
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Which plexus is primarily responsible for innervation of the heart?
Which plexus is primarily responsible for innervation of the heart?
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Which of the following accurately describes the sympathetic chain ganglia?
Which of the following accurately describes the sympathetic chain ganglia?
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Hirschsprung disease is characterized by a lack of innervation in which part of the digestive tract?
Hirschsprung disease is characterized by a lack of innervation in which part of the digestive tract?
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Which neurotransmitter is released by postganglionic fibers of the sympathetic nervous system?
Which neurotransmitter is released by postganglionic fibers of the sympathetic nervous system?
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Where do the preganglionic neurosomas of the sympathetic division reside?
Where do the preganglionic neurosomas of the sympathetic division reside?
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What is megacolon often associated with?
What is megacolon often associated with?
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What structure forms pelvic nerves that target specific organs?
What structure forms pelvic nerves that target specific organs?
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Which type of adrenergic receptors are targeted by norepinephrine in the heart?
Which type of adrenergic receptors are targeted by norepinephrine in the heart?
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What role does the adrenal medulla play in the sympathetic nervous system?
What role does the adrenal medulla play in the sympathetic nervous system?
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What is a component of the enteric nervous system?
What is a component of the enteric nervous system?
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In which part of the body does the sympathetic division NOT supply nerve fibers?
In which part of the body does the sympathetic division NOT supply nerve fibers?
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Which factor does not play a role in the normal digestive function?
Which factor does not play a role in the normal digestive function?
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What condition is characterized by fecal impaction above constriction due to GI tract issues?
What condition is characterized by fecal impaction above constriction due to GI tract issues?
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Which of the following best describes the fibers that enter the sympathetic chain?
Which of the following best describes the fibers that enter the sympathetic chain?
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Which part of the spinal cord is typically involved in pelvic nerve formation?
Which part of the spinal cord is typically involved in pelvic nerve formation?
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What type of fibers leave the sympathetic ganglion by way of the gray communicating ramus?
What type of fibers leave the sympathetic ganglion by way of the gray communicating ramus?
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What is the primary function of the sympathetic division?
What is the primary function of the sympathetic division?
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What distinguishes the enteric nervous system from the central nervous system?
What distinguishes the enteric nervous system from the central nervous system?
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In Hirschsprung disease, which function is primarily affected?
In Hirschsprung disease, which function is primarily affected?
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How many paravertebral ganglia are typically present in the cervical region?
How many paravertebral ganglia are typically present in the cervical region?
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Which organ's motility is primarily regulated by the enteric nervous system?
Which organ's motility is primarily regulated by the enteric nervous system?
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Which of the following neurotransmitters is used by the preganglionic fibers in the sympathetic division?
Which of the following neurotransmitters is used by the preganglionic fibers in the sympathetic division?
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Which structure receives input primarily from the sympathetic nervous system?
Which structure receives input primarily from the sympathetic nervous system?
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What role do neurotransmitters play in autonomic neuron effects on organs?
What role do neurotransmitters play in autonomic neuron effects on organs?
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What can result from the absence of the enteric nervous system in the bowel?
What can result from the absence of the enteric nervous system in the bowel?
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Study Notes
Autonomic Nervous System
- The autonomic nervous system (ANS) controls glands, cardiac muscle, and smooth muscle.
- It is a motor system that functions involuntarily.
- It regulates fundamental states and life processes like heart rate, blood pressure, and body temperature. This contrasts with the somatic nervous system that controls skeletal muscles voluntarily.
- Walter Cannon coined the terms homeostasis and fight-or-flight, crucial in the ANS's function.
- Animals without the ANS would not be able to survive on their own.
Comparison of Somatic and Autonomic Systems
- Effectors: Skeletal muscle for somatic, glands, smooth muscle, and cardiac muscle for autonomic.
- Control: Generally voluntary for somatic, involuntary for autonomic.
- Distal Nerve Endings: Neuromuscular junctions (somatic), varicosities (autonomic).
- Efferent Pathways: One nerve fiber from CNS to effector; no ganglia (somatic), Two nerve fibers from CNS to effector; synapse at a ganglion (autonomic).
- Neurotransmitters: Acetylcholine (ACh) for somatic, Acetylcholine (ACh) and norepinephrine (NE) for autonomic.
- Effect on target cells: Always excitatory for somatic, excitatory or inhibitory for autonomic
- Denervation effect: Flaccid paralysis for somatic, Denervation hypersensitivity for autonomic.
General Properties of the Autonomic Nervous System
- The ANS is the involuntary motor system controlling viscera (thoracic and abdominal cavity organs) and some aspects of the body wall, such as cutaneous blood vessels, sweat glands, and piloerector muscles.
- The ANS works involuntarily, without conscious intent or awareness, and is essential for adjusting visceral activities.
- Denervation hypersensitivity means an exaggerated response in cardiac and smooth muscle should autonomic nerves be severed.
Comparison of Sympathetic and Parasympathetic Divisions
- Origin in CNS: Thoracolumbar (sympathetic) and craniosacral (parasympathetic).
- Location of ganglia: Paravertebral (sympathetic) or terminal ganglia near target organs (parasympathetic).
- Fiber lengths: Short preganglionic, long postganglionic in sympathetic, long preganglionic, short postganglionic in parasympathetic.
- Neural divergence: Extensive (sympathetic) and minimal (parasympathetic).
- Effects: Often widespread and general (sympathetic) and more specific and local (parasympathetic).
The Sympathetic Division
- The thoracolumbar division arises from the thoracic and lumbar regions of the spinal cord.
- Fibers exit the spinal cord and extend to the nearby sympathetic chain ganglia.
- Preganglionic fibers synapse in paravertebral ganglia or prevertebral ganglia which form the sympathetic chain.
- The chain extends the length of the spinal cord.
- Postganglionic fibers either return to the spinal nerve or leave the chain via the sympathetic trunk.
- Divergence is extensive, meaning one preganglionic neuron influences multiple postganglionic neurons.
- Collateral ganglia contribute to networks like the abdominal aortic plexus, which contains the celiac, superior mesenteric, and inferior mesenteric ganglia. These networks transmit signals to target organs.
The Parasympathetic Division
- Also called the craniosacral division.
- Preganglionic neurons originate in the brainstem (cranial nerves) and sacral spinal cord segments.
- Fibers synapse in terminal ganglia located close to or within target visceral organs or in the enteric nervous system.
- Divergence is restricted, affecting a more specific set of organs.
- The parasympathetic division controls cranial nerves and pelvic nerves innervating pelvic organs and lower colon.
Visceral Reflexes
- Visceral reflexes are unconscious and automatic responses to internal stimuli.
- These events involve receptors, afferent neurons, an integrating center (interneurons) in the CNS, efferent neurons and effectors (glands, smooth or cardiac muscle).
- The ANS serves as the efferent pathway. Examples include baroreflex and micturition reflex.
Divisions of the ANS
- Two divisions often innervate the same organ (dual innervation).
- Sympathetic division prepares the body for activity (fight or flight), increasing heart rate, blood pressure, blood glucose and airflow.
- Parasympathetic division calms the body (rest or digest), promoting digestion and eliminating waste products.
Autonomic Tone
- The normal background activity of the ANS.
- The tone of each division is regulated to meet the body's current needs.
- Parasympathetic tone maintains smooth muscle tone and low basal heart rate.
- Sympathetic tone keeps most blood vessels partially constricted, maintaining normal blood pressure.
Autonomic Output Pathways
- The ANS has components within the central nervous system (CNS) and peripheral nervous system (PNS)
- Control centers are present within nuclei in the brainstem and hypothalamus.
- Motor neurons extend to target tissues (glands, smooth or cardiac muscle).
- Two neurons in autonomic signalling, contrasting somatic pathways which use only one.
Neurotransmitters and Their Receptors
- Acetylcholine (ACh) is a neurotransmitter used by all preganglionic neurons and postganglionic parasympathetic neurons.
- Cholinergic receptors bind ACh.
- Norepinephrine (NE) is employed by most sympathetic postganglionic neurons.
- Adrenergic receptors bind NE.
Dual Innervation
- Most viscera receive nerve fibers from both the sympathetic and parasympathetic divisions.
- Antagonistic effects occur when two divisions have opposite actions on the same effector, while cooperative effects involve both divisions influencing different effectors to coordinate a unified response.
- Some organs, like blood vessels and adrenal medulla, receive only sympathetic innervation.
Central Control of Autonomic Function
- ANS is controlled by different parts of the CNS, including the cerebral cortex, hypothalamus and brainstem nuclei (midbrain, pons, medulla oblongata).
- Emotions and experiences can affect the ANS via limbic system connections to the hypothalamus.
Drugs and the Nervous System
- Neuropharmacology involves the study of drugs' effects on the nervous system.
- Sympathomimetics enhance sympathetic activity while symphatolytics suppress it.
- Parasympathomimetics enhance parasympathetic activity while parasympatholytics suppress it.
The Enteric Nervous System
- The ENS is a network of neurons within the digestive tract walls.
- It controls digestive functions autonomously.
- It regulates motility and secretion.
- It acts independently but is also influenced by the sympathetic and parasympathetic branches of the ANS
Megacolon
- Megacolon is a condition characterized by massive dilation of the bowel and is often associated with severe constipation.
- It can result from specific defects such as in Hirschsprung Disease.
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Description
Test your knowledge on the types of nerve fibers and their functions in the human body. This quiz covers key concepts related to skeletal muscle control, sweat glands, and the role of the sympathetic nervous system. Ideal for students studying human anatomy or physiology.
