Autonomic Nervous System Overview
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Questions and Answers

What happens to cAMP levels when adenylyl cyclase is inhibited?

  • cAMP levels decrease (correct)
  • cAMP levels fluctuate randomly
  • cAMP levels remain unchanged
  • cAMP levels increase

What is a direct consequence of reduced cAMP levels in a cell?

  • Increased PKA activity
  • Increased cell proliferation
  • Decreased ion channel activity (correct)
  • Elevated ATP production

What is the role of cAMP in the activation of Protein Kinase A (PKA)?

  • cAMP binds to and activates PKA (correct)
  • cAMP converts PKA into active form
  • cAMP inhibits PKA
  • cAMP has no effect on PKA

Which of the following is NOT a cellular response triggered by decreased PKA activity?

<p>Increased secretion (C)</p> Signup and view all the answers

Which adrenergic receptor type primarily increases contractility in cardiac muscle cells?

<p>β1-adrenergic receptor (B)</p> Signup and view all the answers

How does PKA affect Ca2+ influx through L-type calcium channels in cardiac muscle cells?

<p>Increases Ca2+ influx (A)</p> Signup and view all the answers

What effect does PKA activation have on smooth muscle cells?

<p>Decreases Ca2+ influx through L-type calcium channels (C)</p> Signup and view all the answers

What is the effect of PKA on the β1-adrenergic receptor itself?

<p>Desensitization (B)</p> Signup and view all the answers

What is the role of DAG in cellular signaling?

<p>Activates protein kinase C (PKC) (A)</p> Signup and view all the answers

Which statement best describes the function of adenylyl cyclase?

<p>Converts ATP into cyclic AMP (cAMP) (C)</p> Signup and view all the answers

Which ion's influx is decreased in smooth muscle cells upon activation of PKA?

<p>Calcium (Ca2+) (A)</p> Signup and view all the answers

What do α1-adrenergic receptors primarily regulate?

<p>Blood vessel constriction (A)</p> Signup and view all the answers

Which enzyme is stimulated by the activated Gq protein associated with α1-adrenergic receptors?

<p>Phospholipase C (D)</p> Signup and view all the answers

What are the second messengers produced when phospholipase C cleaves PIP2?

<p>DAG and IP3 (A)</p> Signup and view all the answers

What physiological effect occurs due to increased intracellular calcium (Ca2+) following IP3 signaling?

<p>Muscle contraction (D)</p> Signup and view all the answers

Which type of adrenergic receptor is primarily involved in heart rate modulation?

<p>β1 receptors (A)</p> Signup and view all the answers

What is the primary effect of α1-adrenergic receptor antagonists like prazosin?

<p>Block NE effects on α1-adrenergic receptors (A)</p> Signup and view all the answers

Which receptor type operates through a Gq protein to initiate a signaling cascade?

<p>α1-adrenergic receptors (B)</p> Signup and view all the answers

How does the activated Gi/Go protein affect adenylyl cyclase?

<p>It inhibits its activity (A)</p> Signup and view all the answers

What is a common physiological role of β2-adrenergic receptors?

<p>Airway dilation (C)</p> Signup and view all the answers

What is the primary neurotransmitter used by postganglionic sympathetic fibers?

<p>Norepinephrine (NE) (B)</p> Signup and view all the answers

Where do the preganglionic sympathetic neurons originate?

<p>Thoracic to lumbar spinal cord (A)</p> Signup and view all the answers

Which receptors are primarily targeted by norepinephrine in the sympathetic division?

<p>Adrenergic receptors (D)</p> Signup and view all the answers

What role does the adrenal medulla play in the sympathetic nervous system?

<p>Functioning like a postganglionic neuron (D)</p> Signup and view all the answers

Which of the following nuclei is NOT associated with the parasympathetic division?

<p>Parabrachial nucleus (C)</p> Signup and view all the answers

What is the mechanism of action of adrenergic receptors when activated by norepinephrine?

<p>Activation of adenylate cyclase (A)</p> Signup and view all the answers

What type of outflow do the preganglionic neurons of the parasympathetic division utilize?

<p>Craniosacral outflow (B)</p> Signup and view all the answers

Which structure plays a critical role in coordinating the autonomic nervous system with the endocrine system?

<p>Hypothalamus (A)</p> Signup and view all the answers

What is the effect of sympathetic activation on the body?

<p>Preparation for fight or flight (A)</p> Signup and view all the answers

In terms of neuron structure, what characterizes postganglionic fibers in the sympathetic division?

<p>They are long and unmyelinated (C)</p> Signup and view all the answers

What is the primary neurotransmitter used by both pre- and postganglionic neurons in the ANS?

<p>Acetylcholine (A)</p> Signup and view all the answers

Which type of cholinergic receptor initiates rapid responses in the ganglia?

<p>Nicotinic receptors (B)</p> Signup and view all the answers

What is the effect of sympathetic activation on heart rate?

<p>Increases heart rate (C)</p> Signup and view all the answers

What do muscarinic receptors primarily mediate in target organs?

<p>Slower, complex responses (D)</p> Signup and view all the answers

What is the result of phospholipase C activation after receptor binding?

<p>Release of calcium ions into the cytosol (B)</p> Signup and view all the answers

Which second messenger is produced alongside inositol trisphosphate (IP3) during phospholipase C activation?

<p>Diacylglycerol (D)</p> Signup and view all the answers

What physiological response can elevated intracellular calcium levels lead to?

<p>Muscle contraction (B)</p> Signup and view all the answers

What is the role of cholinergic receptors in the autonomic nervous system?

<p>They mediate responses to acetylcholine (C)</p> Signup and view all the answers

What characteristic describes the balance of sympathetic and parasympathetic activity at rest?

<p>Both divisions maintain a tone that can shift (A)</p> Signup and view all the answers

What physiological action can occur when transitioning from a supine to an upright position?

<p>Orthostatic hypotension (A)</p> Signup and view all the answers

What is the primary role of the cerebellum in motor control?

<p>Integrate sensory information to fine-tune motor commands (A)</p> Signup and view all the answers

What condition is primarily characterized by uncoordinated movement resulting from cerebellar dysfunction?

<p>Ataxia (D)</p> Signup and view all the answers

Which type of cerebellar input provides the strongest excitatory signal directly to Purkinje cells?

<p>Climbing fibers (A)</p> Signup and view all the answers

Which of the following signals is primarily communicated by Purkinje cells?

<p>Inhibitory GABAergic signals to deep cerebellar nuclei (C)</p> Signup and view all the answers

What happens to a person's posture when there is cerebellar dysfunction?

<p>Face may turn contralaterally (D)</p> Signup and view all the answers

Which deep nuclei are largely responsible for output from the cerebellum?

<p>All four deep nuclei (D)</p> Signup and view all the answers

In mild cerebellar dysfunction, which of the following is essential for maintaining smooth movement?

<p>Visual cues (C)</p> Signup and view all the answers

Which of the following best describes the output signal from the deep cerebellar nuclei?

<p>Excitatory output modulating motor control (B)</p> Signup and view all the answers

What is a common speech-related symptom of cerebellar dysfunction?

<p>Slurred speech and dysarthria (D)</p> Signup and view all the answers

What is the role of mossy fibers in the cerebellum?

<p>Deliver weak excitatory input to granule cells (C)</p> Signup and view all the answers

What is the main effect of lesions in the basal ganglia?

<p>They can cause either excessive or reduced movement. (B)</p> Signup and view all the answers

What role do the direct and indirect pathways of the basal ganglia play?

<p>One facilitates movement while the other inhibits unnecessary movement. (C)</p> Signup and view all the answers

Which symptom is typically associated with Parkinson's disease?

<p>Tremors and stiffness (A)</p> Signup and view all the answers

How do basal ganglia differ from the cerebellum in movement control?

<p>Basal ganglia initiate and select movement patterns. (D)</p> Signup and view all the answers

What is a consequence of the overactivity in inhibitory pathways in Parkinson's disease?

<p>Reduced motor coordination (C)</p> Signup and view all the answers

Which disorder is characterized by hyperkinetic movements?

<p>Huntington's Disease (D)</p> Signup and view all the answers

Which nuclei are part of the basal ganglia?

<p>Caudate, putamen, and substantia nigra (D)</p> Signup and view all the answers

What primary neurotransmitter is affected in Parkinson's disease?

<p>Dopamine (A)</p> Signup and view all the answers

Which structure is primarily responsible for output from the basal ganglia to the thalamus?

<p>Substantia nigra and globus pallidus (A)</p> Signup and view all the answers

What effect does the basal ganglia output have on thalamic activity?

<p>It inhibits thalamic activity. (A)</p> Signup and view all the answers

What is the primary clinical consequence of upper motor neuron lesions?

<p>Spasticity and exaggerated reflexes (D)</p> Signup and view all the answers

Which statement best describes the role of the cerebellum in movement?

<p>It processes sensory information to modify muscle actions. (B)</p> Signup and view all the answers

What distinguishes the lateral pathways from the ventromedial pathways in the motor system?

<p>Lateral pathways control fine voluntary movements, while ventromedial pathways influence posture and reflexive movements. (A)</p> Signup and view all the answers

What would most likely occur with lower motor neuron lesions?

<p>Flaccid paralysis and muscle atrophy (A)</p> Signup and view all the answers

How does the negative feedback mechanism in the motor system operate?

<p>By adjusting movements in real-time based on discrepancies between intended and actual movements (D)</p> Signup and view all the answers

What is a key function of the premotor and supplementary motor areas in the brain?

<p>Formulate and organize the motor program for intended movement (D)</p> Signup and view all the answers

Which of the following describes the outcome of disinhibition in the direct pathway of motor control?

<p>It enhances movement by reducing inhibitory output to the thalamus (B)</p> Signup and view all the answers

What provides the motivation for movement in the motor system?

<p>Subcortical structures such as limbic areas and basal ganglia (D)</p> Signup and view all the answers

The primary role of lower motor neurons is to:

<p>Connect the central nervous system to muscle fibers for movement (D)</p> Signup and view all the answers

Which brain regions are primarily involved in the loop for motor control that contributes to movement facilitation?

<p>Cortex, basal ganglia, thalamus, and back to cortex (A)</p> Signup and view all the answers

Flashcards

cAMP

Cyclic AMP is a second messenger molecule that activates protein kinase A (PKA).

PKA

Protein Kinase A (PKA) is an enzyme that phosphorylates other proteins, leading to changes in cellular activity.

Adrenaline receptor

A protein that receives signals from adrenaline (epinephrine) and triggers a cascade of events, affecting cell functions.

β1-adrenergic receptor

A type of receptor that triggers increased heart muscle contraction via PKA activation.

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β2-adrenergic receptor

A type of receptor involved in smooth muscle relaxation via PKA.

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Adenylyl Cyclase

An enzyme that converts ATP into cAMP

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Gs protein

A protein that activates adenylyl cyclase.

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Decreased cAMP

Reduced levels of cAMP, decreasing PKA activity, impacting cell functions.

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Cellular Responses

The various effects of PKA activation or inhibition, depending on cell type and target proteins.

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Second Messenger

A molecule that relays signals from a receptor to target molecules inside the cell.

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α1-adrenergic receptors

G protein-coupled receptors (GPCRs) that bind norepinephrine (NE), triggering cellular responses via a signaling cascade.

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Gq protein

A G protein that activates phospholipase C (PLC) upon activation by an activated α1-adrenergic receptor.

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Phospholipase C (PLC)

An enzyme activated by the Gq protein that breaks down PIP2 into IP3 and DAG.

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Inositol trisphosphate (IP3)

A second messenger produced by PLC, triggering calcium release from the endoplasmic reticulum.

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Diacylglycerol (DAG)

A second messenger produced by PLC, activating protein kinase C (PKC).

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Protein Kinase C (PKC)

An enzyme activated by DAG, phosphorylating proteins to initiate various cellular responses.

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Norepinephrine (NE)

A neurotransmitter stimulating α1-adrenergic receptors, initiating signaling cascades that modify cellular activities.

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Second Messengers

Small molecules produced within cells in response to signaling pathways to trigger specific changes within the cells.

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Calcium Ions (Ca2+)

Ions released from the endoplasmic reticulum in response to IP3 that trigger various cellular responses, including muscle contractions and secretion.

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Adrenergic Receptors

A broad category of receptors for norepinephrine and epinephrine.

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Postganglionic neurons

Neurons in the autonomic nervous system that directly innervate target organs, causing localized and specific responses.

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Neurotransmitters (ANS)

Chemical messengers like acetylcholine (ACh) that transmit signals between neurons or from neurons to target organs within the autonomic nervous system.

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Nicotinic receptors

Receptors that respond to acetylcholine and are found in the autonomic ganglia, initiating rapid responses.

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Muscarinic receptors

Receptors that respond to acetylcholine and are located on target organs, mediating slower, more complex responses.

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Cholinergic Receptors

A group of receptors that bind acetylcholine involved in both fast and slow responses in the ANS

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SNS and PNS balance

Both sympathetic and parasympathetic divisions are active at rest, maintaining a functional equilibrium in the body.

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Orthostatic Hypotension

A temporary drop in blood pressure that occurs when suddenly changing from a lying to a standing position.

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Phospholipase C (PLC)

An enzyme that is activated by a G-protein and cleaves PIP2 into second messengers.

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Second Messengers (IP3 & DAG)

Molecules produced by PLC that relay signals from the outside of a cell to the inside, leading to various cellular effects.

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Calcium Ions (Ca2+)

Ions released by IP3 into the cytosol, causing various cellular responses.

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Autonomic Nervous System (ANS)

Part of the peripheral nervous system that controls involuntary bodily functions, working automatically without conscious effort to maintain homeostasis.

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Sympathetic Division (SNS)

Part of the ANS that activates 'fight or flight' responses in the body during stress or danger.

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Parasympathetic Division

Part of the ANS that manages "rest and digest" activities, promoting relaxation and maintaining normal body functions.

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Preganglionic Neurons

Neurons in the ANS that transmit signals from the central nervous system to a ganglion.

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Postganglionic Neurons

Neurons in the ANS that transmit signals from a ganglion to the target organ.

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Sympathetic Ganglia Origin

Preganglionic neurons of the sympathetic division originate from spinal cord segments T1-L3.

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Neurotransmitters in Sympathetic Division

The primary neurotransmitter in the postganglionic fibers is norepinephrine, affecting adrenergic receptors.

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Parasympathetic Nuclei locations

Parasympathetic nuclei are located in the brainstem (four nuclei) and sacral spinal cord.

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Parasympathetic Output Cranial Nerves

Cranial nerves 3, 7, 9, and 10 carry parasympathetic output from the brainstem.

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Parasympathetic Output Sacral Nerves

Parasympathetic nerves originate from spinal cord segments S2-S4 and target organs directly.

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Motor System

A system that enables voluntary, complex, carefully timed and coordinated movements.

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Hierarchical Organization

The motor system's organization where information travels through multiple control centers.

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Negative Feedback

A mechanism that adjusts movements by comparing intended and actual movement.

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Feed Forward

Anticipating and adjusting movements using memory; predicting outcome and adjusting in advance.

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Upper Motor Neuron (UMN)

Neuron in brain cortex that initiates movement.

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Lower Motor Neuron (LMN)

Neuron connecting to muscles to enable movement.

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UMN Lesion

Damage to an upper motor neuron leading to spasticity and exaggerated reflexes.

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LMN Lesion

Damage to a lower motor neuron causing flaccid paralysis and muscle atrophy.

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Extrapyramidal Disorders

Disorders affecting the motor system's organization, occurring in psychiatric patients and mimicking medication side effects.

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Motor Pathways

Two main pathways (lateral and ventromedial) for controlling fine voluntary movement and influencing posture and reflexive movements, respectively.

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Basal Ganglia Function

Initiates and regulates movement, receiving input from the cerebral cortex and sending output via the thalamus back to the cortex.

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Basal Ganglia Components

Consists of caudate, putamen, globus pallidus, subthalamic nucleus, and substantia nigra.

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Parkinson's Disease Cause

Damage to dopamine-producing neurons in the substantia nigra, leading to overactive inhibitory pathways.

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Parkinson's Disease Symptoms

Tremors, stiffness, slow movement, and expressionless face.

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Basal Ganglia Direct Pathway

Facilitates movement by reducing inhibition on motor activity.

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Basal Ganglia Indirect Pathway

Suppresses unnecessary movement by increasing inhibition.

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Basal Ganglia vs. Cerebellum

Basal ganglia control movement initiation, while the cerebellum refines ongoing movement.

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Basal Ganglia Dysfunction

Lesions can lead to hyperkinetic (excessive movement—Huntington's) or hypokinetic (reduced movement—Parkinson's) disorders.

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Basal Ganglia Output

Output (GPi/SNr) is inhibitory to thalamus, involved with movement control.

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Basal Ganglia Input

Primary input from cerebral cortex and output via thalamus back to cortex (NB ∆ cerebellum!)

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Deep Cerebellar Nuclei (DCN)

Nuclei within the cerebellum that receive input from Purkinje cells and project output to various brain regions, modulating motor control.

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Purkinje Cells

Neurons in the cerebellar cortex that provide inhibitory GABAergic output to the deep cerebellar nuclei.

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Climbing Fibers

Large fibers originating from the inferior olivary nucleus, providing strong excitatory input to Purkinje cells, causing complex spikes.

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Mossy Fibers

Fibers originating from diverse sources, providing weak excitatory input to granule cells in the cerebellar cortex.

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Cerebellar Ataxia

Movement disorder characterized by uncoordinated movements, tremors, and slurred speech resulting from cerebellar damage.

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Cerebellar Dysfunction

Impairment of cerebellar function, leading to various motor control problems, including ataxia, tremors, and dysarthria.

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4 Deep Nuclei

Dentate, Globose, Emboliform, and Fastigial (interpositus)

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Cerebellum Organization

Divided into midline (trunk control), paravermal (limbs), and lateral (digits) zones.

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Cerebellar Function

Coordination of movement, preventing overcorrections, and adjusting learned motor skills.

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Cerebellar Motor Learning

The cerebellum's role in acquiring and refining new motor skills, such as adjusting movements and coordination

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Study Notes

Autonomic Nervous System (ANS)

  • The ANS is part of the peripheral nervous system (PNS)
  • It includes sympathetic and parasympathetic divisions
  • It works automatically without conscious effort
  • It coordinates with the endocrine system to maintain homeostasis

Sympathetic Division (SNS)

  • Prepares the body for "fight or flight"
  • Preganglionic neurons originate in the spinal cord (T1-L3)
  • Travel to sympathetic ganglia
  • Preganglionic fibers emerge as spinal nerves T1-L3
  • Project via white rami (type B, myelinated) to paravertebral ganglia
  • Neurotransmitter: Acetylcholine (ACh) at the junction/synapse
  • Exceptions:
    • Fibers between T12-L1 project to superior/inferior mesenteric ganglia
    • Fibers L1-L3 project to inferior mesenteric ganglion
  • Postganglionic fibers are type C and unmyelinated, long axons
  • Postganglionic neurons send signals to organs and tissues, often causing widespread responses

Parasympathetic Division (PNS)

  • Manages "rest and digest" activities
  • Preganglionic neurons start in the brainstem and sacral spinal cord
  • Postganglionic neurons are shorter and innervate target organs directly
  • Neurotransmitter: Acetylcholine (ACh) used by both pre- and postganglionic neurons.

Neurotransmitters

  • Norepinephrine (NE) is the primary transmitter in postganglionic sympathetic fibers, acting on adrenergic receptors (α and β).
  • Acetylcholine (ACh) is used by both pre- and postganglionic parasympathetic neurons, acting on cholinergic receptors (muscarinic and nicotinic).
  • Adrenal Medulla releases NE and epinephrine into the bloodstream for a powerful sustained response

Receptors

  • Cholinergic receptors (respond to ACh):
    • Nicotinic receptors (N1, N2): Found in ganglia, initiate rapid responses
    • Muscarinic receptors (M1-M5): Located on target organs, mediate slower complex responses.
  • Adrenergic receptors (respond to NE and epinephrine):
    • Alpha receptors (α1, α2): Regulate functions like blood vessel constriction.
    • Beta receptors (β1, β2, β3): Involved in heart rate modulation, airway dilation, and energy mobilization.

ANS Action

  • Balance of SNS and PNS maintains a "tone"
  • Responses often occur in anticipation
  • ANS activity is linked to somatic NS activity

Specific examples/Organ Systems

  • Heart: Sympathetic activation increases heart rate, blood pressure; parasympathetic activation lowers heart rate.
  • Digestion: Parasympathetic activation enhances digestion and supports energy storage; sympathetic activation is less related.

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Description

Explore the intricacies of the Autonomic Nervous System (ANS) in this quiz. Learn about its two main divisions, the sympathetic and parasympathetic systems, and how they function in maintaining homeostasis without conscious effort. Test your knowledge on key concepts and details specific to each division.

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