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Questions and Answers
The parasympathetic nervous system is active during emergency situations.
The parasympathetic nervous system is active during emergency situations.
False
The sympathetic nervous system is associated with 'rest and digest' functions.
The sympathetic nervous system is associated with 'rest and digest' functions.
False
Both the sympathetic and parasympathetic nervous systems innervate most visceral organs.
Both the sympathetic and parasympathetic nervous systems innervate most visceral organs.
True
Sympathetic stimulation decreases heart rate.
Sympathetic stimulation decreases heart rate.
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The entire sympathetic nervous system tends to activate simultaneously.
The entire sympathetic nervous system tends to activate simultaneously.
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The parasympathetic nervous system is generally involved in promoting secretions and mobility in the digestive tract.
The parasympathetic nervous system is generally involved in promoting secretions and mobility in the digestive tract.
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Dual innervation allows for precise control over an organ's functions.
Dual innervation allows for precise control over an organ's functions.
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Increased activity in one branch of the autonomic nervous system does not affect the other branch.
Increased activity in one branch of the autonomic nervous system does not affect the other branch.
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The autonomic nervous system (ANS) is considered voluntary.
The autonomic nervous system (ANS) is considered voluntary.
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The ANS has three divisions: sympathetic, parasympathetic, and enteric.
The ANS has three divisions: sympathetic, parasympathetic, and enteric.
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Most visceral organs are innervated by only one division of the autonomic nervous system.
Most visceral organs are innervated by only one division of the autonomic nervous system.
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The medulla and pons are involved in the central control of the ANS output.
The medulla and pons are involved in the central control of the ANS output.
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Cutting the autonomic nerve fibers to an effector organ will completely stop its function.
Cutting the autonomic nerve fibers to an effector organ will completely stop its function.
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The hypothalamus has no significant role in the control of the ANS.
The hypothalamus has no significant role in the control of the ANS.
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Tonic activity refers to the complete shutdown of the ANS.
Tonic activity refers to the complete shutdown of the ANS.
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An effector organ can be a muscle or a gland innervated by autonomic fibers.
An effector organ can be a muscle or a gland innervated by autonomic fibers.
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The Vagus nerve carries nearly 80% of the total craniosacral flow.
The Vagus nerve carries nearly 80% of the total craniosacral flow.
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Sympathetic preganglionic nerves are long and unmyelinated.
Sympathetic preganglionic nerves are long and unmyelinated.
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Postganglionic sympathetic neurons primarily release noradrenaline.
Postganglionic sympathetic neurons primarily release noradrenaline.
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Both sympathetic and parasympathetic preganglionic neurons release norepinephrine.
Both sympathetic and parasympathetic preganglionic neurons release norepinephrine.
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Blood vessels are innervated by both sympathetic and parasympathetic nervous systems.
Blood vessels are innervated by both sympathetic and parasympathetic nervous systems.
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Salivary gland secretion is increased by both sympathetic and parasympathetic input.
Salivary gland secretion is increased by both sympathetic and parasympathetic input.
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Cholinergic receptors respond to adrenaline.
Cholinergic receptors respond to adrenaline.
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Sweat glands are mainly innervated by the sympathetic nervous system.
Sweat glands are mainly innervated by the sympathetic nervous system.
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Nicotinic receptors are ionotropic in nature and elicit a fast response.
Nicotinic receptors are ionotropic in nature and elicit a fast response.
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Muscarinic receptors are found on all postganglionic ANS cell bodies.
Muscarinic receptors are found on all postganglionic ANS cell bodies.
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Metabotropic receptors directly modulate ionic activity without the involvement of G proteins.
Metabotropic receptors directly modulate ionic activity without the involvement of G proteins.
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Tissue/organ targets can possess more than one type of receptor for neurotransmitters.
Tissue/organ targets can possess more than one type of receptor for neurotransmitters.
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Acetylcholine (ACh) can activate both nicotinic and muscarinic receptors.
Acetylcholine (ACh) can activate both nicotinic and muscarinic receptors.
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All receptors on effector cell membranes are ionotropic receptors.
All receptors on effector cell membranes are ionotropic receptors.
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Nicotinic receptors are activated by tobacco derivatives like nicotine.
Nicotinic receptors are activated by tobacco derivatives like nicotine.
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The cyclic AMP system is part of the ionotropic receptor signaling pathway.
The cyclic AMP system is part of the ionotropic receptor signaling pathway.
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A1 adrenergic receptors lead to an excitatory response and increase blood pressure.
A1 adrenergic receptors lead to an excitatory response and increase blood pressure.
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A2 adrenergic receptors are associated with excitatory responses in the digestive system.
A2 adrenergic receptors are associated with excitatory responses in the digestive system.
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B1 adrenergic receptors when activated cause a decrease in the rate and force of cardiac muscle contraction.
B1 adrenergic receptors when activated cause a decrease in the rate and force of cardiac muscle contraction.
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B2 adrenergic receptors are primarily inhibitory and are located in skeletal muscle vascular beds.
B2 adrenergic receptors are primarily inhibitory and are located in skeletal muscle vascular beds.
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Both a and b adrenergic receptors bind to noradrenaline and adrenaline.
Both a and b adrenergic receptors bind to noradrenaline and adrenaline.
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Muscarinic ACh receptors are ionotropic receptors.
Muscarinic ACh receptors are ionotropic receptors.
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The M2 type muscarinic receptor increases heart contraction.
The M2 type muscarinic receptor increases heart contraction.
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Nicotinic receptors open intrinsic Na+/K+ channels when activated.
Nicotinic receptors open intrinsic Na+/K+ channels when activated.
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All muscarinic receptors are G protein-coupled receptors.
All muscarinic receptors are G protein-coupled receptors.
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The response time for nicotinic receptors is rapid.
The response time for nicotinic receptors is rapid.
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M3 muscarinic receptors are located in cardiac tissue.
M3 muscarinic receptors are located in cardiac tissue.
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Muscarinic receptors can activate second-messenger systems.
Muscarinic receptors can activate second-messenger systems.
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Parasympathetic ganglion fibers do not contain nicotinic receptors.
Parasympathetic ganglion fibers do not contain nicotinic receptors.
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Study Notes
Autonomic Nervous System Biology
- Course: The Body: Movement and Function (BMF)
- Class: DEM Year 1
- Lecturer: Dr. Ebrahim Rajab ([email protected])
- Date: 10/11/2024
Learning Objectives
- Recall the divisions of the nervous system
- Contrast the anatomical features of sympathetic and parasympathetic systems
- Identify the functions of the sympathetic and parasympathetic nervous systems
- Describe the neurotransmitters and receptors located in the ANS
Divisions of Nervous System
- Nervous system is divided into:
- Central nervous system (CNS): brain and spinal cord
- Peripheral nervous system (PNS):
- Autonomic nervous system (ANS): regulates internal organs (heart, circulation, digestive and respiratory systems)
- Sympathetic division (arousing)
- Parasympathetic division (calming)
- Somatic nervous system: regulates voluntary muscles and sensory input from sense organs
- Autonomic nervous system (ANS): regulates internal organs (heart, circulation, digestive and respiratory systems)
Divisions of Peripheral Nervous System
- Sensory (afferent) division:
- General: touch, pain, pressure, vibration, temperature, and proprioception (skin, body wall, limbs)
- Special: hearing, equilibrium, vision, taste, smell
- Motor (efferent) division:
- Somatic nervous system: innervation of all skeletal muscles
- Autonomic nervous system (ANS): innervation of smooth muscle, cardiac muscle, and glands
Divisions of Autonomic Nervous System
- Involuntary system maintaining homeostasis
- Regulates internal organ functions (coordinate manner)
- Two divisions (sympathetic & parasympathetic) that innervate most visceral organs (dual innervation)
- Mostly opposing effects, but partially active ("tonic" activity) under most circumstances
Internal Organs/Viscera Controlled by ANS
- Heart
- Lungs
- Stomach & GI tract, spleen, pancreas
- Bladder & rectum
- Kidneys & liver
- Eye (pupil)
Control of the ANS
- CNS has central control over ANS output
- Medulla and Pons in brain stem regulate cardiovascular, respiratory and digestive systems
- Hypothalamus plays a major role in regulating heart rate, blood pressure, and respiration, often through the hypothalamus-pituitary-adrenal (HPA) axis
- Spinal cord integrates autonomic reflexes not subject to higher control (e.g., urination, defecation)
Overview of Sympathetic and Parasympathetic NS
- Parasympathetic: activated in non-emergencies, promotes restorative functions ("Rest & Digest"), conserving energy, digestion and maintenance of the body
- Sympathetic: activated in emergency situations or stress ("Fight or Flight"), increases energy expenditure, routes blood to muscles, and raises blood glucose
Advantages of Dual ANS Innervation
- Most visceral organs are innervated by both sympathetic and parasympathetic nerves (dual innervation)
- Dual innervation gives the ability for fine-tuned control over organ/tissue function (as opposed to just on or off)
- Sympathetic stimulation generally elevates activity while parasympathetic stimulation decreases activity
Exceptions to Dual Innervation
- Some organs (e.g., arterioles and veins) are innervated by only the sympathetic division.
- Blood vessels, sweat glands, etc. show exceptions to the rule of dual innervation.
Arrangement of SNS & PSNS Pathways
-
Pathway from CNS to organ/effector is a two-neuron chain (preganglionic neuron synapse/ganglion → postganglionic neuron → organ) for both divisions (sympathetic & parasympathetic)
-
Sympathetic nerves are short & myelinated preganglionic fiber, and long & unmyelinated postganglionic fiber
-
Parasympathetic nerves are long & myelinated preganglionic fiber, and short & unmyelinated postganglionic fiber
Modified Sympathetic Nervous System - Adrenal Medulla
- Two adrenal glands, each containing outer cortex and inner medulla, extend sympathetic nervous system
- Adrenal medulla is considered a modified sympathetic ganglion
- Cells of the medulla don't have axons, but release adrenaline (epinephrine) and noradrenaline (norepinephrine) directly into blood
Origins of the Parasympathetic
- Preganglionic neurons originate in cranial nerves (III, VII, IX, X) and sacral spinal nerves (S2-S4)
- Vagus nerve (X) is a primary part of the craniosacral outflow, responsible for nearly 80% of this flow
- Ganglion is typically located closer to the target organ
- Postganglionic neuron is short & unmyelinated
Sympathetic Nervous System
- Thoracolumbar outflow from thoracic and lumbar regions for preganglionic fibers
- Preganglionic fibers are short and myelinated
- Sympathetic ganglia lie in sympathetic trunk/chain along either side of spinal cord
- Postganglionic fibers are long and unmyelinated
ANS Neurotransmitters and Receptors
-
Sympathetic & parasympathetic preganglionic neurons release acetylcholine (ACh)
-
Most postganglionic sympathetic neurons release noradrenaline (norepinephrine)
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Most postganglionic parasympathetic neurons release acetylcholine (ACh)
-
Receptors activated by NTs can be ionotropic or metabotropic
-
Ionotropic receptors are typically ligand-gated ion channels
-
Metabotropic receptors typically involve second messengers and require G proteins
Additional Complexity and Exceptions
- Several exceptions to general rules about dual innervation
- Some organs are solely or predominantly innervated by one division (e.g., salivary and sweat glands, blood vessels) and may have both
Cholinergic Receptors
- Nicotinic receptors: found on all postganglionic autonomic nerve cell bodies and are ionotropic (fast response)
- Muscarinic receptors: found on smooth muscle, glands, and cardiac muscle, are metabotropic (slower) and have 5 subtypes
Nicotinic Receptors
- ACh binding opens intrinsic Na+/K+ channels
- Ionotropic
- Leads to depolarization of the postsynaptic cell
Muscarinic Receptors
- Metabotropic
- M2: inhibitory, found on cardiac tissue, increases K+ conductance, inhibits calcium channels (decreases heart contraction)
- M3: excitatory, found in digestive system, increases glandular secretions and smooth muscle contraction
NT receptors & Parasympathetic division
- Preganglionic fibers release acetylcholine (ACh) which activates nicotinic receptors
- Postganglionic fibers release acetylcholine (ACh) which activates muscarinic receptors
Adrenergic Receptors
- Only found at effector organ synapses
- After postganglionic sympathetic nerve activation
- Two major classes (α and β) are coupled to G proteins.
• α1: excitatory, located on most sympathetic target cells, increases contraction of arterioles raising blood pressure • α2: inhibitory, located in digestive system, decreases smooth muscle contraction, reducing GIT motility • β1: excitatory, located in the heart causing contraction of cardiac muscle increasing heart rate and force • β2: inhibitory, located on skeletal muscle, vessels and organs, causing relaxation of smooth muscle in bronchioles, increasing dilation.
Termination of NT Effects
- Acetylcholine: destroyed by acetylcholinesterase at synapses
- Noradrenaline: re-uptake by pre- and postsynaptic cells, then metabolized/recycled
STEPS OF NEUROCHEMICAL TRANSMISSION
- Nerve Terminal: Neurotransmitter release,
- Post Synaptic Membrane: neurotransmitter-receptor interaction,
- Neurotransmitter Effect Termination: Neurotransmitter degradation
ANS Drugs
- Drugs can mimic or inhibit the effects of ANS neurotransmitter/receptor interactions
- Muscarinic antagonists (e.g., atropine) reduce parasympathetic activity
- Adrenergic agonists (e.g., salbutamol) stimulate sympathetic activity on certain organs (only effects certain organs e.g. bronchioles but not other sites)
- Adrenergic antagonists (e.g., atenolol) inhibit sympathetic activity (lowers blood pressure)
Autonomic Dysfunction
- Many forms (e.g., orthostatic hypotension, neurocardiogenic syncope, chronic stress disorders)
- Often caused by issues with the hypothalamus-pituitary-adrenal axis (HPA)
Comparison of Autonomic and Somatic NS
- Autonomic (involuntary, branched): uses two neuron-chains (pre/post ganglionic fibers), and regulates smooth, cardiac and glandular tissues, may be acetylcholine or norepinephrine at effector organs and exhibit either stimulatory or inhibitory effects
- Somatic (voluntary, single-neuron): innervates skeletal muscles, only releases acetylcholine and has solely stimulatory effect
Books for further study
- Neuroscience: exploring the brain, 3rd ed. by Bear, Connors, Paradiso
- Boron, Boulpaep, Medical Physiology, by Boron and Boulpaep
- Rhoades, Medical Physiology, Principles for Clinical Medicine
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Description
This quiz focuses on the autonomic nervous system as part of the Body: Movement and Function course for Year 1 students. It covers the divisions, functions, and anatomical features of the sympathetic and parasympathetic systems, along with neurotransmitters involved. Test your understanding of these essential biological concepts.
