Autonomic vs Somatic Nervous System Quiz

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Questions and Answers

What is a common CNS effect of amphetamines?

Increased heart rate

Reduced blood pressure

Increased sedation

Heightened awareness (correct)

Which characteristic differentiates ephedrine from other drugs in its category?

It has a longer duration of action (correct)

It is purely sympathomimetic

It only acts on alpha receptors

It does not affect biogenic amines

What potential psychological effect can occur with high doses of amphetamines?

Development of anxiety disorders

Psychotic behavior disturbances (correct)

Enhanced social interactions

Increased memory retention

What major cardiovascular effect can tricyclic antidepressants cause?

Tachycardia Signup and view all the answers

What is a primary therapeutic use of beta blockers during an acute myocardial infarction?

Decrease mortality rate Signup and view all the answers

How does cocaine primarily enhance sympathetic transmission?

By blocking norepinephrine reuptake Signup and view all the answers

Which drug may decrease the absorption of beta blockers?

Aluminum salts Signup and view all the answers

Which of the following is NOT a benefit of using beta blockers in patients with congestive heart failure?

Complete reversal of the disease Signup and view all the answers

In the treatment of chronic open-angle glaucoma, which of the following beta blockers is used?

Timolol Signup and view all the answers

Which statement is TRUE regarding the effects of beta blockers on pupil size when treating glaucoma?

They have little or no effect on pupil size Signup and view all the answers

What types of effector cells are innervated by the autonomic nervous system?

Smooth muscle, cardiac muscle, and exocrine glands Signup and view all the answers

Which of the following correctly describes the function of the sympathetic nervous system?

Increases heart rate during stress Signup and view all the answers

How many neurons are typically involved in the autonomic nervous system pathway from the CNS to effector organs?

Two neurons Signup and view all the answers

Which statement is true about the synaptic junctions in the autonomic nervous system?

They occur in ganglia outside the cerebrospinal axis Signup and view all the answers

What is the primary function of the parasympathetic nervous system?

Facilitating 'rest and digest' processes Signup and view all the answers

What is the primary role of vesicular storage of norepinephrine (NE)?

Ensures regulated release of transmitters Signup and view all the answers

Which process contributes the most to the removal of norepinephrine from the synapse?

Transport back into the noradrenergic neuron Signup and view all the answers

What is the mechanism of β1-adrenoceptors primarily associated with?

Positive inotropic and chronotropic effects on the heart Signup and view all the answers

Which of the following accurately describes the comparative potency of a-AR and b-AR?

b-AR: EPI ≥ NE >> isoproterenol Signup and view all the answers

Which subtype of adrenergic receptors is associated with bronchodilation?

β2 receptors Signup and view all the answers

Which of the following describes a common effect of beta-adrenergic receptor antagonists on the cardiovascular system?

Decreased heart rate Signup and view all the answers

Which medication is primarily used for the treatment of benign prostatic hyperplasia (BPH)?

Tamsulosin Signup and view all the answers

What is a notable side effect associated with the first doses of quinazolines?

Marked postural hypotension Signup and view all the answers

Which beta-adrenergic receptor antagonist is considered the prototype drug in its class?

Propranolol Signup and view all the answers

What characterizes b1-selective antagonists compared to non-selective antagonists?

They have differing relative affinities for b1 and b2 receptors. Signup and view all the answers

Which of the following effects occurs shortly after administering beta-adrenergic antagonists?

Decrease in blood pressure Signup and view all the answers

What is the mechanism of action of Yohimbine?

Competitive antagonist of a2-AR Signup and view all the answers

Which statement is true regarding intrinsic sympathomimetic activity (ISA) of certain beta-antagonists?

They activate b-AR partially in the absence of catecholamines. Signup and view all the answers

Study Notes

Autonomic Nervous System

Operates involuntarily on reflex control
Maintains body's internal environment (homeostasis)
Innervates smooth muscle, cardiac muscle, and exocrine glands

Somatic Nervous System

Innervates skeletal muscle
Voluntary control of skeletal muscle

Anatomical Differences: ANS vs SNS

Two neurons in ANS, one neuron in somatic NS
Synaptic junctions in ANS occur in ganglia, which lie outside the central nervous system. There are no such structures in the somatic NS.
Efferent neurons in somatic NS are myelinated, while postsynaptic autonomic neurons are generally nonmyelinated.

Autonomic Nervous System Divisions

Sympathetic nervous system (thoracolumbar)
Parasympathetic nervous system (craniosacral)
Enteric nervous system

Physiology of the ANS

Controls smooth muscle, exocrine secretions, and heart rate and force
Sympathetic and parasympathetic systems have opposing actions in some situations (e.g., heart rate control) but not in others (e.g., salivary gland function)
Sympathetic activity increases in stress ('fight or flight'), while PNS activity predominates 'rest & digest'
Both systems exert a continuous physiological control of specific organs under normal conditions

Vesicular Storage of NE

Ensures regulated release of neurotransmitters
Decreases intraneuronal metabolism
Decreases leakage of NE to the extracellular sites

Release of NE

Action potential triggers the exocytosis of NE-containing vesicles
Similar process as release of Ach
Neuropeptide Y and ATP are also released along with NE

Removal of NE From the Synapse

Three processes contribute to termination of its transmitter role:
- Transport back into noradrenergic neuron (reuptake, uptake 1)
- Dilution by diffusion out of the junctional cleft and uptake into extraneuronal sites
- Metabolic transformation by MAO and COMT (catechol O-methyl transferase)

Adrenoceptors

Can be broadly divided into two classes: α-AR and β-AR
Comparative potency: - α-AR: EPI ≥ NE >>isoproterenol - β-AR: isoproterenol > EPI ≥ NE
Α-AR: α1 and α2 subtypes
- α1A, α 1B, and α 1D
- α 2A, α 2B, and α 2C
β-AR: β1 , β2 & β3 subtypes
All are GPCR

β-AR

Couple to Gs and activate adenylyl cyclase ( cAMP  activation PKA  activation of target proteins).
β1 receptors are mainly found in the heart and have positive inotropic and chronotropic effects.
β2 receptors mediate bronchodilatation, vasodilatation, and relaxation of visceral smooth muscle.
Selective β2 agonists relax smooth muscle with minimal effect on the heart.
Selective β1 antagonists have a useful blocking effect on the heart with minimal effect on bronchial smooth muscle.
β3 receptors are involved in lipolysis.

Amphetamine: CNS Effects

CNS effects are mediated by the release of biogenic amines from their storage sites in nerve terminals.
Effects include alertness, anorexia, and locomotor stimulation.
With higher doses, disturbances of perception and overt psychotic behavior occur.

Ephedrine

Mixed-acting (causes release of biogenic amines from nerve terminals and also acts on both α- and β-AR)
Has a longer duration of action (resistant to metabolism by MAO and COMT)

Other Drugs in This Category

Methamphetamine
Methylphenidate
Pemoline

Drugs That Affect NE Uptake

Tricyclic antidepressants (e.g., desipramine):
- Major effect is on the CNS but also cause tachycardia and cardiac dysrhythmias.
Cocaine:
- Enhances sympathetic transmission, causing tachycardia and increased arterial pressure.
- Its central effects of euphoria and excitement are probably a manifestation of the same mechanism acting in the brain.

α1-AR Antagonists

Efficacious in the treatment of BPH (benign prostatic hyperplasia) with little effect on blood pressure.

Adverse Effects

First-dose effect: marked postural hypotension (quinazolines)
Impaired ejaculation (tamsulosine)

Therapeutic Uses

Treatment of hypertension (prazosin and congeners)
Congestive heart failure
Benign prostatic hyperplasia (especially tamsulosine)

Yohimbine

Indolealkylamine alkaloid which is a selective competitive antagonist of α2-AR
Readily enters the CNS and acts to increase BP and heart rate; it also enhances motor activity and produces tremors.

β-AR Antagonists

Most are competitive antagonists of β-AR
Useful in the treatment of hypertension, ischemic heart disease, CHF, and certain arrhythmias
Propranolol: prototype drug in this group

β-AR Antagonist Subtypes

Relative affinity for β1 and β2 receptors:
- Non-selective antagonists (propranolol, nadolol, timolol)
- β1-selective antagonists (metoprolol, atenolol, acebutolol, bisoprolol, and esmolol): selectivity is not absolute and is dose dependent.
Intrinsic sympathomimetic activity (ISA):
- Pindolol and acebutolol: activate β-AR partially in the absence of catecholamines
- May be counterproductive to the response desired from a β-antagonist
- Prevent profound bradycardia or negative inotropy in a resting heart
Differences in lipid solubility
Pharmacokinetic properties

Pharmacological Effects

CVS:
- Slow HR and decrease myocardial contractility
-  cardiac output
- TPR
  - Initial increase (blockade of vascular β2-AR and reflex stimulation of sympathetic activity)
  - Returns to initial state or decreases with prolonged use
-  in BP

CVS (cont’d)

Reduce sinus rate, decrease the spontaneous rate of depolarization of ectopic pacemakers, slow conduction in the atria and in the AV node, and increase functional refractory period of the AV node.

Hypoglycemia and Bronchospasm

Hypoglycemia is rare, and bronchospasm is uncommon in the absence of pulmonary disease.

Drug Interactions

Aluminum salts, cholestyramine, and colestipol may decrease the absorption of β blockers.
Phenytoin, rifampin, and phenobarbital, as well as smoking (inducers), may decrease plasma concentrations of β blockers.

Therapeutic Uses: Cardiovascular Diseases

Myocardial infarction:
- Administered during the early phases of acute myocardial infarction and continued long-term may decrease mortality by about 25%.
- Precise mechanism is not known but may involve decreased myocardial oxygen demand, redistribution of myocardial blood flow, and antiarrhythmic actions.

Therapeutic Uses: Congestive Heart Failure

Improve myocardial function, improve life quality, and prolong life.
Reduce the mortality rate and reduce the hospitalization of patients.

Therapeutic Uses: Glaucoma

Treatment of chronic open-angle glaucoma
Carteolol, betaxolol, levobunolol, metipranolol, timolol, and levobetaxolol
Have little or no effect on pupil size or accommodation and are devoid of blurred vision and night blindness.

Other Drugs That Block Adrenergic Transmission

Guanethidine, guanadrel, bethanidine, debrisoquine
Reserpine
Ganglion blockers

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Description

Test your knowledge on the autonomic and somatic nervous systems with this quiz. Explore their functions, anatomical differences, and physiological roles in the human body. Perfect for students studying anatomy and physiology.