Sympathetic Nervous System
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Questions and Answers

Where do the nerves of the sympathetic nervous system primarily originate?

  • Thoracic and lumbar spinal cord (correct)
  • Cranial and thoracic spinal cord
  • Lumbar and cervical spinal cord
  • Cervical and sacral spinal cord

What is the primary action of the preganglionic neurons in the sympathetic nervous system?

  • Release of serotonin
  • Release of acetylcholine (correct)
  • Release of dopamine
  • Release of norepinephrine

Which ganglion is responsible for innervating the stomach and small intestine?

  • Superior mesenteric ganglion
  • Inferior mesenteric ganglion
  • Celiac ganglion (correct)
  • Superior cervical ganglion

Which neurotransmitter is primarily released by chromaffin cells in the adrenal medulla during sympathetic activation?

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

What is the action of α1 adrenoreceptors in vascular smooth muscle?

<p>Increase of intracellular calcium levels (B)</p> Signup and view all the answers

Which of the following best describes the function of the hypothalamus in the autonomic nervous system?

<p>Regulates body temperature and thirst (B)</p> Signup and view all the answers

Which ganglion is NOT part of the sympathetic ganglia associated with the autonomic nervous system?

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

What role does Neuropeptide Y (NPY) play in the sympathetic postganglionic adrenergic nerves?

<p>It increases the intensity of neurotransmission (A)</p> Signup and view all the answers

Which medication is primarily used to treat chronic asthma when combined with steroids?

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

In which condition is terbutaline primarily indicated for use?

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

What is the primary clinical use of methylphenidate?

<p>Management of ADHD (D)</p> Signup and view all the answers

Which α1 antagonist is primarily used to manage pheochromocytoma?

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

What is the effect of propranolol in treating hyperthyroidism symptoms?

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

What initiates the activation of α1 adrenoreceptors?

<p>Binding of noradrenaline to the receptor (A)</p> Signup and view all the answers

What is the primary effect after the activation of α1 adrenoreceptors?

<p>Contraction of vascular smooth muscle (C)</p> Signup and view all the answers

How does the α2 adrenoreceptor affect adenylyl cyclase activity?

<p>It inhibits adenylyl cyclase which decreases cAMP. (C)</p> Signup and view all the answers

Which of these correctly describes the activation mechanism of α1 adrenoreceptors?

<p>Migration of α-GTP complex to activate phospholipase C (B)</p> Signup and view all the answers

What are the primary locations of β1 receptors in the body?

<p>Heart and salivary glands (A)</p> Signup and view all the answers

What is the effect of noradrenaline binding to α2 adrenoreceptors?

<p>Inhibition in the gastrointestinal tract (C)</p> Signup and view all the answers

Where are α1 adrenoreceptors primarily located?

<p>In vascular smooth muscle and sphincters (B)</p> Signup and view all the answers

What molecule is produced by activated phospholipase C after α1 receptor activation?

<p>Diacylglycerol and IP3 (C)</p> Signup and view all the answers

Which subunit of the G protein is involved in the activation of adenylyl cyclase by α2 adrenoreceptors?

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

What is the role of calcium ions in the signaling mechanism of α1 adrenoreceptors?

<p>Activating protein kinase C (C)</p> Signup and view all the answers

Which type of receptor is responsible for the stimulation of adenylyl cyclase and the increase of cAMP in the heart?

<p>β1 adrenoreceptor (B)</p> Signup and view all the answers

What physiological mechanism is associated with β2 adrenoreceptors in vascular smooth muscle?

<p>Stimulation of adenylyl cyclase and increase of cAMP (A)</p> Signup and view all the answers

Which neurotransmitter primarily interacts with adrenoreceptors?

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

What is the mechanism of action for the α1 adrenoreceptor in vascular smooth muscle?

<p>Inactive α subunit bound to GDP (D)</p> Signup and view all the answers

How do muscarinic receptors affect cAMP levels?

<p>Decrease cAMP levels (D)</p> Signup and view all the answers

What is the primary physiological response mediated by β2 adrenoreceptors?

<p>Relaxation of vascular smooth muscle (B)</p> Signup and view all the answers

Which enzyme is likely affected by β adrenergic stimulation leading to increased second messenger levels?

<p>Adenylyl cyclase (C)</p> Signup and view all the answers

Which of the following is a function of nicotinic receptors?

<p>Opening Na and K channels (B)</p> Signup and view all the answers

What roles do adrenergic receptors play in pharmacological contexts?

<p>Both agonists and antagonists can affect various adrenergic receptor subtypes (B)</p> Signup and view all the answers

In which tissue would you find α2 adrenergic receptors predominantly?

<p>Central nervous system (D)</p> Signup and view all the answers

What occurs first after acetylcholine binds to nicotinic receptors?

<p>Activation occurs leading to receptor binding (C)</p> Signup and view all the answers

What is the primary effect of activated phospholipase C in muscarinic receptors?

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

Which type of receptors are located in the sweat glands?

<p>Muscarinic receptors (C)</p> Signup and view all the answers

In the activation of β2 receptors, what is the first step that occurs?

<p>GTP binding to the α subunit (B)</p> Signup and view all the answers

Which of the following describes the mechanism of action of indirect-acting adrenoceptor agonists like amphetamine?

<p>Inhibits the reuptake of neurotransmitters (D)</p> Signup and view all the answers

What is a key clinical application of epinephrine?

<p>Inducing local vasoconstriction (D)</p> Signup and view all the answers

How do muscarinic receptors activate protein kinase C?

<p>By generating diacylglycerol from phosphatidylinositol (B)</p> Signup and view all the answers

Which receptor type binds to acetylcholine in chromaffin cells?

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

What characterizes the action of cocaine in the nervous system?

<p>Blocks dopamine transporters (A)</p> Signup and view all the answers

Which agonist is used in cases of acute hypotension to provide cardiovascular support?

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

Flashcards

Sympathetic Nervous System (SNS)

Part of the autonomic nervous system responsible for the 'fight-or-flight' response.

Autonomic Nervous System

Part of the nervous system that controls involuntary body functions, like heart rate and digestion.

Fight-or-Flight response

Physiological reaction to perceived threat, involving increased heart rate, breathing, and alertness.

Sympathetic Ganglia

Clusters of nerve cells that relay signals from the spinal cord to organs in the SNS.

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Preganglionic neuron

Neurons that transmit signals from the spinal cord to the ganglia in the SNS.

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Adrenergic nerves

Nerves that release neurotransmitters such as norepinephrine and epinephrine.

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Adrenal Medulla

Inner part of the adrenal gland that releases adrenaline and noradrenaline into the bloodstream in response to stress.

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Neurotransmitters (e.g., NA, ATP, NPY)

Chemical messengers that transmit signals between neurons and target tissues in the Sympathetic Nervous System.

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Intracellular domain

Part of a receptor protein that is inside the cell, transmitting signals to the cell's interior.

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G-protein

A protein that assists in signal transduction across cell membranes.

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β1 adrenoreceptor

A type of adrenergic receptor found mostly in the heart and other tissues like salivary glands and adipose tissue.

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β2 adrenoreceptor

A type of adrenergic receptor primarily located in the smooth muscles, and lungs. It affects the airway, blood vessels, and gastrointestinal tract.

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Nicotinic receptors

A type of cholinergic receptor that activates by binding of acetylcholine leading to depolarization and opening of ion channels.

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Muscarinic receptors

A type of cholinergic receptor found on various effector organs, mediating a variety of effects.

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α1 adrenoreceptor

A type of adrenergic receptor, commonly found in vascular smooth muscle triggering vasoconstriction.

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cAMP

Cyclic Adenosine Monophosphate- a second messenger involved in intracellular signal transduction.

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IP3

Inositol triphosphate- a second messenger involved in intracellular calcium release.

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Adrenergic receptors

A family of cell surface receptors that bind to both norepinephrine and epinephrine (adrenaline) to trigger specific cellular responses .

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Noradrenaline binding to α1 receptor

Triggers a signaling cascade leading to smooth muscle contraction in various tissues like blood vessels, gastrointestinal tract, and iris.

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α1 Adrenoreceptor location

Found in vascular smooth muscle, skeletal muscle, sphincters of the gastrointestinal tract, and radial muscle of the iris.

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α2 Adrenoreceptor location

Located on neurons, both pre- and post-synaptically, and within the gastrointestinal tract.

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α2 Receptor effect

Activation leads to inhibitory actions, impacting neurotransmitter release and other physiological processes.

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Hetero/Autoreceptors

Specialized receptors that regulate the activity of a cell based on its own release versus that of another cell.

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β1 Receptor location

Found primarily in the heart (affecting heart rate and contractility), salivary glands, adipose tissue, and kidney (affecting renin secretion).

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G-protein coupled receptors (GPCR)

A large family of receptors that induce cellular responses after binding of a signal (e.g., noradrenaline).

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Adrenergic receptors

A group of GPCRs that respond to noradrenaline or adrenaline.

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IP3

A second messenger generated from a signalling pathway related to noradrenaline.

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Protein Kinase C (PKC)

An enzyme activated by noradrenaline to trigger various cellular responses after it binds to its various receptors.

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Beta2 agonist asthma treatment

Long-lasting beta2 agonists (Indacaterol, olodaterol, vilanterol) are used in combination with steroids for chronic asthma.

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Epinephrine use in anaphylaxis

Used to treat the life-threatening allergic reaction called anaphylaxis, which involves bronchospasm, swelling, and low blood pressure.

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Pheochromocytoma cause

A tumor of the adrenal medulla or sympathetic ganglion, causing excess catecholamines, often leading to high blood pressure, headaches, and other symptoms.

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Beta-blocker use in glaucoma

Beta-blocking agents (e.g., timolol) reduce intraocular pressure, which is essential for glaucoma treatment.

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Propranolol's use in hyperthyroidism

Reduces palpitations, rapid heart rate, tremors, and anxiety in hyperthyroidism; non-selective beta blocker.

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G protein activation

G protein activation involves a receptor binding to a ligand, causing a change in the G protein's structure. This activates the G protein, causing dissociation of the alpha subunit from the beta and gamma subunits.

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Adenylyl Cyclase activation

Activated alpha-GTP binds to and activates adenylyl cyclase, converting ATP to cAMP, a key second messenger.

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β2 receptors location

β2 receptors are found in vascular smooth muscle (skeletal muscles), gastrointestinal tract, bladder, and bronchioles.

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Nicotinic receptors

Nicotinic receptors are ion channels located on postganglionic neurons and chromaffin cells, activated by acetylcholine.

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Muscarinic M3 receptors

Muscarinic M3 receptors are located in sweat glands and activated by acetylcholine leading to the production and release of cellular calcium.

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Indirect-acting agonists

Indirect-acting agonists like amphetamine and cocaine affect neurotransmitter actions by inhibiting their reuptake, leading to increased synaptic activity.

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Amphetamine mechanism

Amphetamine causes the release of dopamine and norepinephrine, enhancing mood, alertness, and influencing appetite.

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Cocaine mechanism

Cocaine blocks the dopamine transporter (DAT), preventing the reuptake of dopamine.

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Acute hypotension treatment

Treatment for acute hypotension involves using agonists with both α and β activity to provide sustained blood pressure and address tissue hypoperfusion.

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Chronic Orthostatic Hypotension treatment

Midodrine is an α1 agonist used to treat chronic orthostatic hypotension, a condition affecting blood pressure regulation.

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Study Notes

Sympathetic Nervous System

  • The sympathetic nervous system (SNS) originates in the thoracic and lumbar spinal cord (T1 to T12 and L1 to L3)
  • SNS nerves do not travel directly to the target organs.
  • Instead, they synapse with neurons in ganglia located near the spinal cord.
  • Two main categories of ganglia:
    • Paravertebral ganglia (sympathetic chain)
    • Prevertebral ganglia (celia, superior mesenteric and inferior mesenteric)
  • Ganglia relay signals to effector organs.

Autonomic Nervous System

  • The autonomic nervous system has both sympathetic (fight or flight) and parasympathetic (rest and digest) branches.
  • This system controls involuntary bodily functions like heart rate, digestion, and pupil dilation.

Fight or Flight Response

  • The fight or flight response is a physiological response to stress or perceived threat.
  • The sympathetic nervous system is activated, leading to increased heart rate, blood pressure, and breathing rate; pupils dilate, slowing digestion.
  • This response prepares the body for action.

Structure of the sympathetic nervous system

  • SNS nerves originate in the thoracic and lumbar spinal cord (T1 to T12 and L1 to L3)
  • SNS nerves do not travel directly to the organs. There are intermediary ganglia.
  • Two main types of ganglia are involved:
    • Para-ventral ganglia (sympathetic chain ganglia)
    • Prevertebral ganglia (celia, superior mesenteric and inferior mesenteric ganglia)

Sympathetic ganglia

  • Located near the spinal cord (paravertebral ganglia and the prevertebral ganglia)
  • Ganglia are connected to specific target organs:
    • Superior cervical ganglion → eyes and salivary glands
    • Celiac ganglion → stomach and small intestine
    • Superior mesenteric ganglion → small and large intestine
    • Inferior mesenteric ganglion → lower large intestine, anus, bladder, and genitalia.

Receptors and Neurotransmitters of SNS

  • Preganglionic neurons release acetylcholine (ACh). ACh binds to nicotinic receptors.
  • Postganglionic neurons release either noradrenaline or adrenaline.
  • Adrenaline is released from the adrenal medulla.

Co-transmitters in the SNS

  • Sympathetic postganglionic adrenergic nerves release:
    • Norepinephrine (NA)
    • ATP
    • Neuropeptide Y (NPY)
  • These substances together affect the intensity of the response.

Brain control of ANS

  • Important areas of the brain that regulate the ANS include:
    • Hypothalamus
    • Midbrain
    • Pons
    • Medulla

Classification of Receptors (Mechanism of Action)

  • Adrenoreceptors and cholinergic receptors have different effects on various tissues. This is due to their mechanism of action.

A bit of Pharma...

  • Drugs can have physiological and pharmacological effects on the body.
    • Physiologic response: effect of the drug on the target organ/tissue.
    • Pharmacological effect: effect of the neurotransmitters or drugs on the receptors, often based on the drug being antagonist or agonist.

Adrenoreceptors

  • Noradrenaline and adrenaline act on adrenergic receptors in target organs.
  • Two types:
    • Alpha receptors (α1, α2)
    • Beta receptors (β1, β2, β3)

α1 Adrenoreceptors

  • Location: vascular smooth muscle of the skin, skeletal muscle, sphincters of the GI tract, radial muscle of the iris.
  • Mechanism: activate a different G-protein, that leads to contraction of smooth muscle
  • Effect after activation: contraction (vasoconstriction)

α2 Adrenoreceptors

  • Location: presynaptically and postsynaptically in neurons, gastrointestinal tract.
  • Effect after activation: inhibitory.
  • Mechanisms: involve G protein, leading to inhibition of adenylyl cyclase.

β1 Adrenoreceptors

  • Location: heart, salivary glands, adipose tissue, kidney.
  • Mechanism: activation of adenylyl cyclase. This enzyme converts ATP to cAMP which leads to increased activity in the target tissue.

β2 Adrenoreceptors

  • Location: vascular smooth muscle of skeletal muscle, walls of GI tract, bladder, and bronchioles.
  • Mechanism: Same as beta 1

Cholinoreceptors

  • Acetylcholine acts on the cholinergic receptors in the SNS.
  • Two types:
    • Nicotinic receptors
    • Muscarinic receptors

Nicotinic Receptors

  • Location: postganglionic neurons, chromaffin cells of the adrenal medulla.
  • Mechanism: Ion channel that leads to depolarisation.

Muscarinic Receptors

  • Location: sweat glands (in the sympathetic system)
  • Mechanism: G-protein coupled receptor.

Indirect-Acting Adrenoceptor Agonists

  • Amphetamine-like drugs
  • Cocaine: blocks the DAT, inhibiting reuptake of DA.
  • Mechanism: inhibit reuptake of released neurotransmitters

Clinical applications of adrenoreceptor agonists

  • Used for conditions like acute hypotension, cardiac arrest or inducing local vasoconstriction, as well as pulmonary applications and ophthalmic conditions.

Clinical applications of alpha-receptor antagonists

Conditions like pheochromocytoma, hypertensive emergencies.

Beta-receptor antagonists drugs

  • Propranolol and Metoprolol are nonselective and ẞ1-selective, respectively.

Clinical Applications (Various Conditions)

  • These drugs can be used in treating hypertension, ischemic heart disease, glaucoma, hyperthyroidism, and several neurological conditions.

CNS control of the ANS

  • The CNS, and certain structures in it, regulate the activities of the ANS

Reflex Mechanisms (e.g., blood pressure, micturition)

  • Explain the importance of sympathetic and parasympathetic systems in responding to certain stimuli.
  • For instance blood pressure regulation or micturition (urination)

Reflex Mechanisms (Pupil diameter)

  • The pupil size is controlled by two muscles, the pupillary dilator and constrictor.
  • These muscles are controlled by sympathetic and parasympathetic nervous system branches, which regulates their contraction and relaxation.

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Sympathetic Nervous System PDF

Description

This quiz explores the sympathetic nervous system and its role within the autonomic nervous system. You will learn about the origins of the SNS, the types of ganglia involved, and how it contributes to the fight or flight response. Test your understanding of these essential physiological processes.

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