Autonomic Nervous System Overview

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Questions and Answers

What type of ganglia is located adjacent to the prevertebral ganglia in the sympathetic chain?

Collateral ganglia

Prevertebral ganglia

Dorsal root ganglia

Paravertebral ganglia (correct)

Which of the following accurately describes the axons of preganglionic neurons in the sympathetic system?

They are long and myelinated.

They are short and myelinated. (correct)

They are long and unmyelinated.

They are short and unmyelinated.

What is the primary reason for the divergence of sympathetic efferent neurons?

To achieve simultaneous activation of various effector organs. (correct)

To limit the distribution of nerve signals.

To delay the fight or flight response.

To activate digestive organs.

Which structure provides inputs to collateral (prevertebral) ganglia?

Splanchnic and sympathetic neurons Signup and view all the answers

Which of the following accurately illustrates the pathway of a preganglionic sympathetic neuron at the level of T1?

Ascends to the superior cervical ganglion to innervate the eye. Signup and view all the answers

What is the primary function of the sensory (afferent) pathway?

Detects stimuli and sends signals to the CNS Signup and view all the answers

What distinguishes somatic reflexes from visceral reflexes in terms of the motor (efferent) pathway?

Somatic reflexes involve a single neuron projecting to skeletal muscles Signup and view all the answers

Which type of reflex involves communication with the central nervous system?

Long reflexes Signup and view all the answers

Where are the cell bodies of preganglionic neurons located in the long reflex arc?

Brainstem nuclei or lateral horn of spinal cord Signup and view all the answers

What role does the myenteric plexus play in the digestive system?

Coordinates smooth muscle contraction and relaxation Signup and view all the answers

In which part of the nervous system are short reflexes entirely located?

Peripheral nervous system Signup and view all the answers

What is a characteristic of autonomic neurons in the reflex arc?

They typically consist of two neurons projecting to target organs Signup and view all the answers

Which of the following correctly identifies a function of the submucosal plexus?

Regulates glandular secretion Signup and view all the answers

Which neurotransmitter is released by presynaptic adrenergic neurons?

Norepinephrine Signup and view all the answers

What type of receptor do cholinergic neurons bind to?

Cholinergic receptors Signup and view all the answers

What is the duration of action for acetylcholine (ACh) in the synaptic cleft?

Short-lived due to rapid breakdown Signup and view all the answers

What type of neuron releases ACh as its neurotransmitter?

Postganglionic neuron Signup and view all the answers

Which type of cholinergic receptor is located on postganglionic neurons?

Nicotinic receptors Signup and view all the answers

What is the impact of ACh binding to its receptor?

Can be either excitatory or inhibitory Signup and view all the answers

What are the main subtype receptors for adrenergic pathways?

Alpha and beta Signup and view all the answers

Where are the cell bodies of preganglionic sympathetic neurons located?

Lateral horn of thoraco-lumbar spinal nerves Signup and view all the answers

What is the primary function of cholinergic receptors?

To bind to acetylcholine on postsynaptic cells Signup and view all the answers

How many pairs of sympathetic chain ganglia are present along the vertebral column?

23 pairs Signup and view all the answers

What is the typical range of ACh molecules released during an action potential?

30,000-3 million ACh molecules Signup and view all the answers

What characterizes the divergence of the sympathetic division?

Single preganglionic neuron may have multiple targets Signup and view all the answers

In which division of the autonomic nervous system are adrenergic neurons exclusively found?

Sympathetic division Signup and view all the answers

What type of receptors does ACh bind to on the target effector?

Muscarinic receptors Signup and view all the answers

Which of the following divisions emerges from the thoracic and upper lumbar spinal cord?

Sympathetic division Signup and view all the answers

Which neurotransmitter's release is not affected by ACh binding?

Epinephrine Signup and view all the answers

What is the primary role of the sympathetic nervous system during emergency situations?

Increasing heart rate and blood pressure Signup and view all the answers

How does the parasympathetic nervous system affect the urinary system?

Inhibits activity of the urinary system Signup and view all the answers

During rest, which response is NOT typical of the parasympathetic nervous system?

Wider airways for airflow Signup and view all the answers

What effect does the sympathetic nervous system have on the cardiovascular system?

Increases heart rate Signup and view all the answers

Which statement is accurate regarding the effect of the parasympathetic nervous system on the respiratory system?

Narrowing of bronchioles occurs Signup and view all the answers

What is the impact of the sympathetic nervous system on sweat glands?

Activates sweat secretion Signup and view all the answers

Which neurotransmitter is primarily involved in the effects of the sympathetic nervous system?

Norepinephrine Signup and view all the answers

How does the parasympathetic nervous system affect the digestive system compared to the sympathetic nervous system?

Promotes digestion vs. inhibits digestion Signup and view all the answers

What response does low light levels trigger in the sympathetic division?

Pupil dilation Signup and view all the answers

Which cranial nerves transmit afferent input on blood pressure and cardiac function to the nucleus of the solitary tract?

Glossopharyngeal and vagus nerves Signup and view all the answers

What effect does the sympathetic division have on blood vessels?

Constriction of blood vessels Signup and view all the answers

Which portion of the nervous system is primarily involved in controlling pupillary size in bright light conditions?

Parasympathetic nervous system Signup and view all the answers

What phenomenon explains the occurrence of referred pain during a heart attack?

Convergence of sensory nerve impulses Signup and view all the answers

Which areas of the body might experience referred pain during a heart attack?

Left shoulder and inner surface of the left arm Signup and view all the answers

What functional role does the cardiovascular center in the medulla have?

Adjusts heart rate and blood pressure Signup and view all the answers

What type of nerve activity primarily leads to an increase in heart rate?

Sympathetic activity Signup and view all the answers

Study Notes

Autonomic Nervous System (ANS)

The ANS controls involuntary functions like cardiac, respiratory, digestive, and urinary systems.
Two main divisions:
- "Rest and digest" (Parasympathetic): Dominant controller of most autonomic effectors most of the time.
- "Fight or flight" (Sympathetic): Active during exercise, emergency, and excitement.
Enteric NS (ENS): Contained entirely within the gut; regulates digestive functions involuntarily.
Sensory (afferent): Monitors internal and external environment and sends it to the CNS.
Motor (efferent): Response to environmental changes to maintain homeostasis.
Most organs receive input from both divisions.
Homeostasis is the balance between the parasympathetic and sympathetic systems.

ANS Overview

Components: Overview, Neurotransmitters, Parasympathetic Division, Sympathetic Division, Dual Innervation, Referred Pain, Reflexes, Long Reflex Arc, Acetylcholine (ACh), Norepinephrine (NE).
Includes diagram of autonomic efferent pathway and diagrams of reflexes.
Details about neurons and pathways in long reflex arcs.
Notes on components of a reflex arc: Sensory (afferent) pathway, Interneuron (not always present), Motor (efferent) pathway.

Reflexes and Homeostasis

Reflex arc: A sensory-integrative-motor pathway that bypasses conscious perception to produce automatic responses.
Components of a reflex arc: Sensory (afferent) pathway, Interneuron (not always present), Motor (efferent) pathway.
Somatic reflexes: involve one neuron, projecting to skeletal muscles.
Visceral reflexes: typically involve two neurons, projecting to cardiac and smooth muscle and glands.

Reflexes & the 3rd Division of the ANS

Long reflexes: Involve the CNS, communicate with the ENS, and have a two-neuron efferent pathway.
Preganglionic neurons have cell bodies in brainstem nuclei or lateral horns of the spinal cord.
Postganglionic neurons have cell bodies in peripheral ganglia.
Short reflexes: Do not involve the CNS; located entirely within the peripheral NS.
Enteric nervous system; plexuses in digestive tract, involved in muscle contraction, relaxation, and gland secretion; organized into Myenteric and Submucosal plexuses.

Components of Long Reflex Arc of ANS

Nuclei/nucleus: group of neuronal cell bodies in the central NS.
Ganglia/ganglion: group of neuronal cell bodies in the peripheral NS.
Afferent neuron: Conducts sensory impulses from the peripheral sensory receptor, to the CNS.
Preganglionic neuron: Conducts impulses from CNS to an autonomic ganglion.
Autonomic ganglion: Location of postganglionic neuron cell bodies and their synapse with the preganglionic neuron.
Postganglionic neuron: Conducts the impulse from the autonomic ganglion to the effector tissue in the periphery.

ANS Divisions

Sympathetic nervous system: preganglionic neurons are located in the lateral horns of the thoracic and lumbar spinal nerves. Postganglionic neurons in paravertebral ganglia.
Parasympathetic nervous system: preganglionic neurons in brainstem nuclei or lateral horns of the sacral spinal nerves. Postganglionic neurons in terminal ganglia.
Location of pre and postganglionic cell bodies.
Length of pre and postganglionic axons.
Degree of nerve divergence, explaining sympathetic and parasympathetic divergence.

Receptors & Neurotransmitters of the ANS

Two primary neurotransmitters: acetylcholine (ACh) and norepinephrine (NE).
Cholinergic neurons release ACh, found in both parasympathetic and sympathetic divisions.
- Nicotinic receptors are on postganglionic neurons.
- Muscarinic receptors are on effector cells.
Adrenergic neurons release NE, found only in sympathetic division.
- Alpha (α) and beta (β) adrenergic receptors are on postsynaptic cells in sympathetic targets.

Duration of Action and Termination of ACh and NE

ACh: Action duration 1-2msec, terminated by enzymatic degradation by acetylcholinesterase (AChE).
NE: Action duration is longer, terminated by reuptake by presynaptic neuron, and in some cases, enzymatic degradation.

What is the difference between NE and Epi?

NE is a neurotransmitter AND a hormone.
Epi is a hormone released by the adrenal medulla.
Released in response to sympathetic NS stimulation.

Referred Pain

Referred pain: stimulation of pain receptors or a different location, as perceived by the body.
Pain receptors in deep structures may be felt as pain in the skin overlying the affected organ, convergence of sensory nerve impulses, misinterpreted brain activity.
Important in diagnosis.

Parasympathetic NS

The preganglionic neuron releases acetylcholine (ACh) binding to nicotinic receptors.
Postganglionic neuron releases ACh binding to muscarinic receptors.
The effect of ACh binding to its receptor will either cause excitation or inhibition of the effector tissue, depending on the receptor and tissue.

Sympathetic NS

Preganglionic neuron release acetylcholine (ACh), binding to nicotinic receptors located on the dendrites of the postganglionic neuron.
Postganglionic neuron release norepinephrine (NE) which binds to adrenergic (alpha or beta) receptors on the target effector.

Concept of Dual Innervation

Most organs receive input from both the parasympathetic and sympathetic divisions.
One division stimulates (accelerator), and the other inhibits (brake) effector organs.
These actions allow for precise control of effector tissues.

Balance in Competing Autonomic Reflex Arcs: Dual Innervation

The balance of parasympathetic and sympathetic activity determines the outcome of a specific effect.
Effect of parasympathetic activity is "rest and digest"
Effect of sympathetic activity is related to "fight or flight"

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Description

This quiz explores the fundamental aspects of the Autonomic Nervous System (ANS), including its divisions, functions, and components. You'll learn about the Parasympathetic and Sympathetic systems, their roles in homeostasis, and the Enteric Nervous System's influence on digestion. Test your knowledge of how the ANS regulates involuntary body functions.