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Questions and Answers
What is the primary role of the autonomic nervous system (ANS)?
What is the primary role of the autonomic nervous system (ANS)?
- Regulates many physiological functions largely outside voluntary control (correct)
- Manages only the gastrointestinal system
- Controls sensory perception
- Regulates voluntary muscle movement
Which of the following is a primary division of the autonomic nervous system?
Which of the following is a primary division of the autonomic nervous system?
- Central nervous system
- Motor nervous system
- Somatic nervous system
- Sympathetic nervous system (correct)
Where do the preganglionic neurons of the sympathetic division originate?
Where do the preganglionic neurons of the sympathetic division originate?
- Thoracic and lumbar segments T1 to L2 (or L3) (correct)
- Sacral segments S2-S4
- Cervical spinal segments
- Cranial nerves III, VII, IX, and X
What neurotransmitter is released by preganglionic neurons in both the sympathetic and parasympathetic divisions?
What neurotransmitter is released by preganglionic neurons in both the sympathetic and parasympathetic divisions?
The enteric nervous system is primarily controlled by which two divisions of the autonomic nervous system?
The enteric nervous system is primarily controlled by which two divisions of the autonomic nervous system?
Where do preganglionic fibers of the parasympathetic division synapse?
Where do preganglionic fibers of the parasympathetic division synapse?
Which of the following statements about the arrangement of neurons in the ANS is correct?
Which of the following statements about the arrangement of neurons in the ANS is correct?
What type of transmitter do postganglionic sympathetic neurons primarily use?
What type of transmitter do postganglionic sympathetic neurons primarily use?
What type of receptors do preganglionic acetylcholine act upon in the postganglionic cells?
What type of receptors do preganglionic acetylcholine act upon in the postganglionic cells?
Which type of receptor is found on postganglionic parasympathetic neurons?
Which type of receptor is found on postganglionic parasympathetic neurons?
Which cells release adrenaline and are similar to postganglionic sympathetic neurons?
Which cells release adrenaline and are similar to postganglionic sympathetic neurons?
What neurotransmitter is primarily used by postganglionic parasympathetic neurons?
What neurotransmitter is primarily used by postganglionic parasympathetic neurons?
Which of the following are types of adrenoreceptors?
Which of the following are types of adrenoreceptors?
What is the primary effect of sympathetic activity on heart rate?
What is the primary effect of sympathetic activity on heart rate?
Which receptors mediate the parasympathetic effect on the heart's pacemaker potential?
Which receptors mediate the parasympathetic effect on the heart's pacemaker potential?
Which statement is true regarding the actions of acetylcholine (ACh) in the autonomic nervous system?
Which statement is true regarding the actions of acetylcholine (ACh) in the autonomic nervous system?
Which of the following is NOT an exception of sympathetic innervation?
Which of the following is NOT an exception of sympathetic innervation?
What is the role of noradrenaline in the cardiac contractility?
What is the role of noradrenaline in the cardiac contractility?
How does sympathetic activity affect the slope of the pacemaker potential?
How does sympathetic activity affect the slope of the pacemaker potential?
What type of receptors do adrenergic neurotransmitters interact with?
What type of receptors do adrenergic neurotransmitters interact with?
Under which condition is sympathetic activity typically higher?
Under which condition is sympathetic activity typically higher?
What type of neuronal fibers are responsible for parasympathetic input to the heart?
What type of neuronal fibers are responsible for parasympathetic input to the heart?
What is the primary neurotransmitter associated with sympathetic input to the heart?
What is the primary neurotransmitter associated with sympathetic input to the heart?
Which cardiovascular parameter does the autonomic nervous system NOT directly control?
Which cardiovascular parameter does the autonomic nervous system NOT directly control?
Flashcards
What does the ANS do?
What does the ANS do?
The Autonomic Nervous System (ANS) controls many physiological functions. It works largely outside conscious control and affects smooth muscle (like blood vessels and organs) and glands.
What is the sympathetic nervous system?
What is the sympathetic nervous system?
The Sympathetic Nervous System is part of the ANS. It's like the 'fight or flight' response, preparing your body for action.
What is the parasympathetic nervous system?
What is the parasympathetic nervous system?
The Parasympathetic Nervous System is part of the ANS. It's like the 'rest and digest' response, calming your body down.
What is the enteric nervous system?
What is the enteric nervous system?
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How do sympathetic and parasympathetic systems communicate?
How do sympathetic and parasympathetic systems communicate?
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Where is the sympathetic division located?
Where is the sympathetic division located?
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Where is the parasympathetic division located?
Where is the parasympathetic division located?
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What chemical do preganglionic neurons release?
What chemical do preganglionic neurons release?
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Noradrenaline (NA)
Noradrenaline (NA)
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Acetylcholine (ACh)
Acetylcholine (ACh)
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Nicotinic ACh receptors
Nicotinic ACh receptors
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Muscarinic ACh receptors
Muscarinic ACh receptors
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Chromaffin Cells
Chromaffin Cells
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Adrenoreceptors
Adrenoreceptors
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α-Adrenoreceptors
α-Adrenoreceptors
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β-Adrenoreceptors
β-Adrenoreceptors
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What is the role of the sympathetic and parasympathetic divisions in the ANS?
What is the role of the sympathetic and parasympathetic divisions in the ANS?
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How do the sympathetic and parasympathetic nervous systems influence heart function?
How do the sympathetic and parasympathetic nervous systems influence heart function?
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What is the function of the sinoatrial (SA) node?
What is the function of the sinoatrial (SA) node?
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How do the sympathetic and parasympathetic nervous systems affect the pacemaker potential?
How do the sympathetic and parasympathetic nervous systems affect the pacemaker potential?
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How does norepinephrine increase the force of contraction in the heart muscle?
How does norepinephrine increase the force of contraction in the heart muscle?
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Study Notes
Curriculum Information
- Curriculum: Phase 1/ Semester 3/ CVS/ Session 4
- Lecturer: Dr. Shahlaa Khazaal Chabuk
- Lecturer's Degrees: MSc/Ph.D. Physiology
Autonomic Nervous System (ANS)
- Important for regulating many physiological functions
- Largely outside voluntary control
- Controls smooth muscle (vascular and visceral) and exocrine secretion
Divisions of the ANS
- Parasympathetic nervous system
- Sympathetic nervous system
- Enteric nervous system (included in some textbooks as a third division)
- Network of neurons surrounding the GI tract
- Controlled by sympathetic and parasympathetic fibers
Organization of ANS Divisions
- Sympathetic:
- Thoracolumbar origin (segments T1 to L2/L3)
- Preganglionic neurons arise from these segments
- Most synapse with postganglionic neurons in the paravertebral chain of ganglia
- Some synapse in prevertebral ganglia
- Preganglionic neurons release acetylcholine (ACh)
- Postganglionic neurons usually release noradrenaline (NA)
- Parasympathetic:
- Craniosacral origin
- Preganglionic fibers travel in cranial nerves (III, VII, IX, X) or sacral outflow (S2-S4)
- Synapse with neurons in ganglia close to the target tissue
- Preganglionic neurons release ACh
- Postganglionic neurons release ACh
Arrangement of Neurons
- Pre- and postganglionic neurons are arranged in series
- Sympathetic and parasympathetic have different arrangements
Neurotransmitters
- Preganglionic neurons (both divisions): release ACh
- ACh acts on nicotinic ACh receptors on the postganglionic cell
- Postganglionic sympathetic neurons: usually release noradrenaline (NA)
- NA acts on adrenergic receptors
- Postganglionic parasympathetic neurons: usually release ACh
- ACh acts on muscarinic ACh receptors
Adrenal Medulla
- Chromaffin cells in the adrenal medulla are like specialized postganglionic sympathetic neurons
- Release adrenaline (epinephrine), which circulates in the blood
Adrenergic Receptors
- Receptors for noradrenaline and adrenaline
- G protein-coupled receptors (no integral ion channel)
- Types/Subtypes: α1-adrenoreceptors, α2-adrenoreceptors, β1-adrenoreceptors, β2-adrenoreceptors
Parasympathetic Neurotransmitters
- Parasympathetic postganglionic neurons use ACh as a neurotransmitter
- ACh acts on muscarinic receptors (M1, M2, and M3) on effector cells
- G protein-coupled receptors
ANS Functions
- Regulates physiological functions
- Often has opposite effects on tissues innervated by both parasympathetic and sympathetic divisions
- Sympathetic activity is more prominent under stress
- Parasympathetic activity is more prominent under basal conditions
- Work together to maintain balance
Independent Regulation of Tissues
- Sympathetic drive to different tissues is regulated independently
- E.g., sympathetic activity to the heart can increase without increasing activity to the GI tract.
- Co-ordinated sympathetic responses can occur in some situations (e.g., fight or flight).
Cardiovascular Control
- ANS controls:
- Heart rate
- Force of contraction of the heart
- Peripheral resistance of blood vessels
Parasympathetic Input to the Heart
- Preganglionic fibers: Cranial nerve X (Vagus)
- Synapse with postganglionic cells on the epicardial surface or within the walls at SA and AV nodes
- Release ACh, which acts on M2 receptors
- Decreases heart rate (-ve chronotropic effect)
- Decreases AV node conduction velocity
Sympathetic Input to the Heart
- Postganglionic fibers: from the sympathetic trunk
- Innervate the SA node, AV node, and myocardium
- Release noradrenaline, which acts on β1 adrenoreceptors
- Increases heart rate (+ve chronotropic effect)
- Increases force of contraction (+ve inotropic effect)
Pacemaker Cells
- Sinoatrial (SA) node cells steadily depolarise towards threshold
- Slow depolarising pacemaker potential
- Turning on a slow Na+ conductance
- Opening of Ca2+ channels
- AP firing in the SA node sets the rhythm of the heart
ANS Effect on Pacemaker Potentials
- Sympathetic: increases the slope of pacemaker potentials
- Parasympathetic: decreases the slope of pacemaker potentials
Noradrenaline and Contraction Force
- NA acting on β1 receptors in the myocardium increases cAMP
- Phosphorylation of Ca2+ channels
- Increased Ca2+ entry during AP
- Increased force of contraction
- Increased uptake of Ca2+ in the sarcoplasmic reticulum
ANS Effects on Vasculature
- Most vessels receive sympathetic innervation, exceptions include specialised tissue (e.g., erectile tissue) that have parasympathetic innervation
- Most arteries and veins have α1-adrenoreceptors, coronary and skeletal muscles also have β2-receptors
Effects of β2- and α1-Adrenoreceptors
- Activating β2-adrenoreceptors causes vasodilation (increase cAMP open potassium channels, smooth muscle relaxation)
- Activating α1-adrenoreceptors causes vasoconstriction (increase in intracellular Ca2+)
Local Metabolites
- Active tissue produces more metabolites (e.g., adenosine, K+, H+, increased CO2)
- Local increases in metabolites have a strong vasodialator effect
- More significant for ensuring adequate perfusion of skeletal and coronary muscle than activating β2-receptors
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