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What is the primary function of the sympathetic nervous system?
What is the primary function of the sympathetic nervous system?
How do the functions of the sympathetic and parasympathetic nervous systems relate?
How do the functions of the sympathetic and parasympathetic nervous systems relate?
What analogy is used to describe the functions of the sympathetic and parasympathetic divisions?
What analogy is used to describe the functions of the sympathetic and parasympathetic divisions?
What does the parasympathetic nervous system primarily control?
What does the parasympathetic nervous system primarily control?
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Which scenario exemplifies the need for both sympathetic and parasympathetic activity?
Which scenario exemplifies the need for both sympathetic and parasympathetic activity?
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What happens to heart rate during respiratory cycles?
What happens to heart rate during respiratory cycles?
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In what way is the enteric nervous system viewed in relation to the autonomic nervous system?
In what way is the enteric nervous system viewed in relation to the autonomic nervous system?
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Which of the following correctly identifies a function of the autonomic nervous system?
Which of the following correctly identifies a function of the autonomic nervous system?
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What function does the sympathetic nervous system (SNS) perform regarding blood flow?
What function does the sympathetic nervous system (SNS) perform regarding blood flow?
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Which neurotransmitter is used by all preganglionic fibers in the autonomic nervous system?
Which neurotransmitter is used by all preganglionic fibers in the autonomic nervous system?
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Where are autonomic ganglia located?
Where are autonomic ganglia located?
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Which statement accurately describes the difference in lengths of preganglionic fibers in the SNS and PSNS?
Which statement accurately describes the difference in lengths of preganglionic fibers in the SNS and PSNS?
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What are the two main categories of autonomic ganglia?
What are the two main categories of autonomic ganglia?
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What is a primary characteristic of sensory ganglia?
What is a primary characteristic of sensory ganglia?
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Which ganglion is involved in pupil constriction and accommodation?
Which ganglion is involved in pupil constriction and accommodation?
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What happens to blood vessels leading to the gastrointestinal tract during activation of the SNS?
What happens to blood vessels leading to the gastrointestinal tract during activation of the SNS?
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What type of neurons are primarily found in dorsal root ganglia?
What type of neurons are primarily found in dorsal root ganglia?
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Which of the following best describes the pathway of the autonomic nervous system?
Which of the following best describes the pathway of the autonomic nervous system?
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Where may an action potential in a dorsal root ganglion neuron initiate?
Where may an action potential in a dorsal root ganglion neuron initiate?
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Which function is primarily associated with the parasympathetic nervous system (PSNS)?
Which function is primarily associated with the parasympathetic nervous system (PSNS)?
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What type of nerves carry signals towards the brain in the peripheral nervous system?
What type of nerves carry signals towards the brain in the peripheral nervous system?
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What part of the spinal cord do dorsal root ganglia extend from?
What part of the spinal cord do dorsal root ganglia extend from?
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What is a feature of the axons of dorsal root ganglion neurons?
What is a feature of the axons of dorsal root ganglion neurons?
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What developmental origin do dorsal root ganglia share with autonomic ganglia?
What developmental origin do dorsal root ganglia share with autonomic ganglia?
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What type of stimuli activate the sensory receptors of dorsal root ganglion neurons?
What type of stimuli activate the sensory receptors of dorsal root ganglion neurons?
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Which ion channels in sensory neurons are thought to be responsible for somatosensory transduction?
Which ion channels in sensory neurons are thought to be responsible for somatosensory transduction?
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What is the primary role of sympathetic ganglia in the nervous system?
What is the primary role of sympathetic ganglia in the nervous system?
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What neurotransmitter is secreted by pre-ganglionic sympathetic fibers?
What neurotransmitter is secreted by pre-ganglionic sympathetic fibers?
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How many pairs of sympathetic ganglia are typically found in the thoracic region?
How many pairs of sympathetic ganglia are typically found in the thoracic region?
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What is the location of the ganglion impar?
What is the location of the ganglion impar?
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Which of the following ganglia innervate organs of the abdominal and pelvic regions?
Which of the following ganglia innervate organs of the abdominal and pelvic regions?
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What type of response is the fight-or-flight response also known as?
What type of response is the fight-or-flight response also known as?
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What is the primary function of the sympathetic nervous system?
What is the primary function of the sympathetic nervous system?
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Which part of the brain contains the major functions of the autonomic nervous system?
Which part of the brain contains the major functions of the autonomic nervous system?
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How does the sympathetic nervous system affect pupil diameter?
How does the sympathetic nervous system affect pupil diameter?
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What neurotransmitter is primarily secreted by the adrenal medulla during the fight-or-flight response?
What neurotransmitter is primarily secreted by the adrenal medulla during the fight-or-flight response?
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In which situation would both the sympathetic and parasympathetic systems be activated?
In which situation would both the sympathetic and parasympathetic systems be activated?
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Which physiological responses are influenced by the sympathetic nervous system?
Which physiological responses are influenced by the sympathetic nervous system?
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What is the role of acetylcholine in the stress response of the sympathetic nervous system?
What is the role of acetylcholine in the stress response of the sympathetic nervous system?
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What type of pain is often associated with autonomic reflexes?
What type of pain is often associated with autonomic reflexes?
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Study Notes
Autonomic Nervous System (ANS)
- ANS is often divided into two subsystems: sympathetic nervous system (SNS) and parasympathetic nervous system (PSNS).
- SNS and PSNS often function in opposition to each other, but are complementary rather than antagonistic.
- SNS is often described as the "accelerator" and PSNS as the "brake" in the body.
- SNS is typically responsible for quick responses, while PSNS is for actions requiring no immediate reaction.
- SNS is often associated with "fight or flight" response, while PSNS is associated with "rest and digest" or "feed and breed."
- There are many instances of sympathetic and parasympathetic activity that cannot be attributed to fight or rest situations.
Sympathetic Nervous System (SNS)
- SNS functions to divert blood flow away from the gastrointestinal (GI) tract and skin by vasoconstriction.
- SNS enhances blood flow to skeletal muscles and the lungs.
- SNS dilates the bronchioles of the lung to allow for greater oxygen exchange.
- SNS increases heart rate.
Parasympathetic Nervous System (PSNS)
- PSNS dilates the blood vessels leading to the GI tract.
- PSNS constricts the pupil and contracts the ciliary muscle to the lens to enable closer vision.
- PSNS stimulates salivary gland secretion.
Preganglionic Neurons
- In the ANS, fibers connecting the central nervous system to ganglia are referred to as preganglionic fibers.
- Ganglia are collections of neuron cell bodies in the peripheral nervous system.
- Autonomic ganglia are the location of synapses between preganglionic and postganglionic neurons.
- All preganglionic fibers, regardless of whether they are in the SNS or PSNS, are cholinergic—they use acetylcholine as their neurotransmitter—and are myelinated.
- ANS requires a sequential two-neuron efferent pathway: preganglionic neuron synapses onto a postganglionic neuron before innervating the target organ.
- Sympathetic preganglionic fibers are shorter than parasympathetic preganglionic fibers because sympathetic ganglia are closer to the spinal cord.
- Parasympathetic preganglionic fibers project to and synapse with the postganglionic fiber close to the target organ, making them longer.
Ganglia Types
- Ganglia are essentially junctions between autonomic nerves from the central nervous system and autonomic nerves innervating their target organs.
- Two main categories of ganglia are sympathetic ganglia and parasympathetic ganglia
- Ciliary ganglion is an example of parasympathetic ganglion involved in pupil constriction and accommodation.
- Dorsal root ganglia are sensory and carry signals from organs, glands and smooth muscle, making them part of the autonomic nervous system.
- Dorsal root ganglia and autonomic ganglia develop from neural crest, which separates from the neural tube to form the spinal cord.
Dorsal Root Ganglia (DRG)
- DRG is a swelling on a dorsal root containing neuron cell bodies that carry signals from sensory organs to the central nervous system.
- Nerves that carry signals towards the brain are known as afferent nerves.
- Axons of DRG neurons are known as afferents, which relay sensory information to the central nervous system.
- DRG neurons are pseudo-unipolar, having an axon with two branches acting as a single axon.
- An action potential in a DRG neuron can initiate in the distal process, bypass the cell body, and propagate along the proximal process to the spinal cord.
- The distal section of the axon can be a bare nerve ending or encapsulated by a structure for specific sensory information.
Sympathetic Ganglia
- Sympathetic ganglia deliver information about stress and impending danger, initiating fight-or-flight response.
- Fight-or-flight response is also known as the sympathetico-adrenal response because pre-ganglionic sympathetic fibers secreting acetylcholine activate adrenaline and noradrenaline secretion from the adrenal medulla.
- This response is mediated directly via impulses through the sympathetic nervous system, and indirectly via catecholamines from the adrenal medulla.
- Sympathetic ganglia have 20,000–30,000 nerve cell bodies and are located close to the spinal cord.
- Sympathetic chain ganglia (paravertebral ganglia) are bilaterally symmetric and located ventral and lateral to the spinal cord.
- Chain extends from the upper neck down to the coccyx.
- Preganglionic nerves from the spinal cord synapse at chain ganglia, with postganglionic fibers extending to visceral organs in the thoracic cavity.
- Usually, 21 or 23 pairs of these ganglia exist.
- Neurons of collateral ganglia (prevertebral ganglia) receive input from splanchnic nerves and innervate organs of the abdominal and pelvic region.
Autonomic Reflexes
- Autonomic reflexes are unconscious motor reflexes relayed from organs and glands to the CNS via visceral afferent signaling.
- These reflex arcs may trigger pain, often referred to as referred pain.
- The sympathetic nervous system is a quick-response system while the parasympathetic system is more slowly activated but dampens response.
- Within the brain, the ANS is located in the medulla oblongata, which regulates respiration, cardiac activity, vasomotor activity and certain reflex actions.
Sympathetic Responses
- Sympathetic division of the ANS maintains internal organ homeostasis and initiates the stress response.
- The sympathetic nervous system helps control most of the body's internal organs.
- Sympathetic nervous system regulates many homeostatic mechanisms.
- SNS mediates the neuronal and hormonal stress response, also known as the fight-or-flight response.
- This response is mediated directly through impulses transmitted through the sympathetic nervous system, and indirectly via catecholamines secreted from the adrenal medulla.
- Messages travel through the SNS bidirectionally, triggering changes in various parts of the body.
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Description
This quiz explores the Autonomic Nervous System, focusing on its two key components: the sympathetic nervous system and the parasympathetic nervous system. Learn how these systems operate in balance and their roles in the body's responses to various situations, from 'fight or flight' to 'rest and digest.'
