Pharm Autonomics W Exp Part 2

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Pharm Autonomics W Exp Part 2 - Quiz

There are different types of receptors in the human body, which respond to chemicals, temperature, pressure and light. Take up the quiz on pham autonomics W exp part two and get to identify which receptors the drugs are more likely to activate when administered to the patient. All the best and look out for part 3.


Questions and Answers
  • 1. 

    A 14-year-old girl received an IM injection of ampicillin to treat an acute pharyngitis. Few minutes late she showed several signs of an anaphylactic reaction and the physician gave her an IM injection of epinephrine. Which of the following expected effects of the drug was most likely mediated by the activation of peripheral postsynaptic alpha-2 receptors?

    • A.

      Increased diameter of the pupil

    • B.

      Decreased secretion of insulin

    • C.

      Increased secretion of renin

    • D.

      Constriction of skin vessels

    • E.

      Increased heart rate

    • F.

      Dilation of skeletal muscle vessels

    Correct Answer
    B. Decreased secretion of insulin
    Explanation
    Answer: B
    Activation of alpha-2 receptors located on pancreatic beta cells inhibits insulin secretion. This is
    one of the actions that contribute to the final hyperglycemic effect of epinephrine.
    A, D) These effects are due to activation of alpha-1, not alpha-2, receptors.
    C, E) These effects is due to activation of beta-1 receptors
    F) This effect is due to activation of beta-2 receptors

    Rate this question:

  • 2. 

    A new autonomic drug was administered locally in the conjunctival sac of a healthy volunteer. Twenty minutes later, measurement of some eye parameters gave the following results: Which of the following pairs of receptors did the drug most likely activate?

    • A.

      Alpha-1 and alpha-2

    • B.

      Alpha-2 and beta-2

    • C.

      Nicotinic Nn and Nm

    • D.

      Muscarinic M2 and M3

    • E.

      Beta-1 and beta-2

    Correct Answer
    A. Alpha-1 and alpha-2
    Explanation
    Answer: A
    Pupillary diameter can be increased either by the activation of alpha-1 receptors (which
    contracts the radial muscle of iris) or by the blockade of M3 receptors (which relaxes the
    sphincter muscle of iris). The question asks for an activation of a receptor and therefore the
    alpha-1 receptor must be involved. Intraocular pressure can be decreased by a decreased
    production or by an increased outflow of the aqueous humor. A decreased production can
    follow either the activation of alpha-2 receptor or the blockade of beta-2 receptors. The question
    asks for an activation of a receptor and therefore the alpha-2 receptor must be involved.
    B) Beta-2 receptor activation would cause an increased production of aqueous humor and
    therefore would increase, not decrease, the intraocular pressure.
    C) Activation of Nn receptors would cause an increase in sympathetic as well as
    parasympathetic firing. Since in the eye the parasympathetic system is predominant this would
    lead to an activation of M3 receptors in the ciliary muscle which would increase the lens
    curvature and an activation of sphincter muscle of iris which would decrease, not increase, the
    pupillary diameter. Activation of Nm receptors causes the contraction of skeletal muscles only
    and therefore can affect the extrinsic, not the intrinsic eye muscles.
    D) (see answer to item C)
    E) (see answer to item B)

    Rate this question:

  • 3. 

    A new autonomic drug that does not cross the blood brain barrier was administered IV to an healthy volunteer. Ten minutes later the following data were recorded: ' Which of the following pairs of receptors were most likely activated by the drug?

    • A.

      Alpha-1 and beta-1

    • B.

      Alpha-2 and beta -2

    • C.

      M2 and Nm

    • D.

      M3 and Nm

    • E.

      Beta-1 and beta-2

    • F.

      M2 and M3

    Correct Answer
    E. Beta-1 and beta-2
    Explanation
    Answer: E
    Activation of beta-1 and beta-2 receptors increases cardiac contractility and rate. Activation of
    beta-2 receptors causes vasodilation which in turn causes reflex tachycardia. So the heart rate
    is increased because of both direct and reflex effects. The increase in heart rate and
    contractility in turn lead to an increase in cardiac output.
    A, B, C, D, F) Activation of these receptors does not cause all the effects listed in the table.

    Rate this question:

  • 4. 

    A 55 year-old male underwent four-vessel coronary artery bypass graft surgery and was then admitted to the Coronary Unit. One hour after the admission patient’s blood pressure fallen and the clinical picture indicated an impending cardiogenic shock. An appropriate therapy was started which included the IV infusion of an adrenergic drug able to activate beta receptors. The beneficial effect of the drug in this case was most likely mediated by which of the following postreceptor mechanisms?

    • A.

      Increased synthesis of IP3 and DAG

    • B.

      Increased synthesis of eicosanoids

    • C.

      Opening of ligand-gated K+ channels

    • D.

      Blockade of voltage-gated Ca++ channels

    • E.

      Increased synthesis of cAMP

    Correct Answer
    E. Increased synthesis of cAMP
    Explanation
    Answer: E
    The activation of all beta receptors increases the synthesis of cAMP by activating adenylyl
    cyclase.
    A, B, C, D) (see explanation above)

    Rate this question:

  • 5. 

    A 25-year-old man complained to his physician of impaired ejaculation during sex. The man, who was suffering from Raynaud’s disease, had started a drug therapy one week ago. The blockade of which of the following receptors most likely mediated the adverse effect of the drug in the patient?

    • A.

      NM

    • B.

      M2

    • C.

      M3

    • D.

      Alpha-2

    • E.

      Alpha-1

    Correct Answer
    E. Alpha-1
    Explanation
    Answer: E
    During the ejaculation the contraction of vas deferens and prostate capsule put the semen into
    the urethra. This contraction is mediated by an increased sympathetic firing which causes the
    activation of alpha-1 receptors located on the smooth muscle of those organs.
    A, B, C, D) These receptors are not involved in the ejaculation process.

    Rate this question:

  • 6. 

    A 21-year-old woman, who was 25 weeks pregnant, presented to the hospital with abdominal cramping and vaginal bleeding. An appropriate therapy was started which included an IV infusion of a drug aimed to reduce uterine contractions. Which of the following receptors were most likely activated by the drug?

    • A.

      Beta-2

    • B.

      Alpha-2

    • C.

      D1

    • D.

      Nn

    • E.

      Beta-1

    • F.

      M2

    Correct Answer
    A. Beta-2
    Explanation
    Answer: A
    Activation of beta-2 uterine receptors can relax both non pregnant and pregnant uterus and
    beta-2 agonists are sometimes used to prevent premature labor.
    B, C, D, E, F) These receptors either are not involved in or actually increase uterine
    contractions.

    Rate this question:

  • 7. 

    The metabolic effects of a new autonomic drug, were studied in voluntary subjects during a phase 1 clinical trial. The following results were obtained: Liver gluconeogenesis: increased Renin secretion: unaffected Plasma K: decreased Degranulation of mast cells: inhibited Lipolysis in fat cells: increased Which of the following pairs of receptors were most likely activated by the drug?

    • A.

      Alpha-1 and beta-1

    • B.

      Beta-2 and beta-3

    • C.

      Beta-1 and beta-2

    • D.

      M3 and beta-3

    • E.

      M2 and M3

    • F.

      Alpha-1 and M2

    Correct Answer
    B. Beta-2 and beta-3
    Explanation
    Answer: B
    Activation of beta-2 receptors increases liver gluconeogenesis, inhibits degranulation of mast
    cells and decrease plasma K (because of increased K uptake by skeletal muscle). Activation of
    beta-3 receptors in fat cells increases lipolysis with enhanced release of free fatty acid into the
    blood.
    C) Beta-1 receptor activation is not involved since the secretion of renin is unaffected.
    A, D, E, F) These pairs of receptors can mediate some, but not all the effects listed.

    Rate this question:

  • 8. 

    A 45-year-old man recently diagnosed with pheochromocytoma started a treatment with a drug that can cause a pronounced decrease of norepinephrine and epinephrine by blocking the first limiting step in catecholamine biosynthesis. Which of the following enzymes was most likely inhibited by the drug?

    • A.

      L-aromatic amino acid decarboxylase

    • B.

      Dopamine beta-hydroxylase

    • C.

      Tyrosine hydroxylase

    • D.

      Phenylethanolamine methyltransferase

    • E.

      Monoamine oxidase

    Correct Answer
    C. Tyrosine hydroxylase
    Explanation
    Answer: C
    The hydroxylation of tyrosine to DOPA is the rate limiting step in norepinephrine biosynthesis
    and is catalyzed by the enzyme tyrosine hydroxylase. The inhibition of this enzyme can
    therefore cause a big reduction of the biosynthesis of the final product.
    A) This enzyme transforms DOPA into dopamine.
    B) This enzyme transforms dopamine into norepinephrine.
    D) This enzyme transforms norepinephrine into epinephrine.
    E) This enzyme transforms norepinephrine and epinephrine into dihydroxymandelic acid and
    dopamine into dihydroxyphenylacetic acid.

    Rate this question:

  • 9. 

    A 45-year-old man was treated topically with eye drops during a routine ophthalmoscopic examination. Few hours later he noticed that he was blinded by bright light and was unable to focus on near objects. These symptoms most likely resulted from a blockade of M3 receptors located on which of the following pairs of eye structures?

    • A.

      Radial muscle of iris and Schlemm canal

    • B.

      Trabecular meshwork and radial muscle of iris

    • C.

      Retina and lens

    • D.

      Sphincter of iris and ciliary muscle

    • E.

      Ciliary epithelium and retina

    Correct Answer
    D. Sphincter of iris and ciliary muscle
    Explanation
    Answer: D
    Activation of M3 receptors located on the sphincter of iris causes contraction of the muscle so
    causing miosis. On the contrary blockade of these receptors causes mydriasis and impairment
    of the pupillary constriction in bright light (the light pupillary reflex) so leading to photophobia.
    Activation of M3 receptors located on the ciliary muscle causes contraction of the muscle,
    which in turn increases lens curvature. The process, called accommodation, allows the eye to
    focus on near objects. On the contrary blockade of these receptors relaxes the ciliary muscle
    (cycloplegia) and impairs the accommodation process.
    A, B, C, E) (see explanation above)

    Rate this question:

  • 10. 

    A 62-year-old man had been diagnosed with cerebellar astrocytoma. The increased cerebral pressure stimulated the vagal nuclei so causing bradycardia. Which of the following postreceptor mechanisms did most likely mediate this effect?

    • A.

      Increased synthesis of IP3 and DAG

    • B.

      Increased synthesis of eicosanoids

    • C.

      Opening of ligand-gated K+ channels

    • D.

      Blockade of voltage-gated Ca++ channels

    • E.

      Increased synthesis of cAMP

    Correct Answer
    C. Opening of ligand-gated K+ channels
    Explanation
    Answer: C
    The increased firing of the vagus nerve caused an increased release of acetylcholine in the
    heart. The neurotransmitter activated M2 receptors which in turn open ligand gate K+ channels.
    This slows SA node depolarization so decreasing the heart rate.
    A, B, D, E) (see explanation above)

    Rate this question:

  • 11. 

    A 54-year-old woman complained to her physician of palpitations, dry mouth, blurred vision and constipation The woman, recently diagnosed with endogenous depression, had started an antidepressive therapy 3 weeks previously. The symptoms of the patient most likely resulted from a blockade of which of the following pairs of receptors?

    • A.

      Alpha-1 and alpha-2

    • B.

      Alpha-1 and beta-1

    • C.

      M2 and M3

    • D.

      Beta-1 and beta-2

    • E.

      Nicotinic Nm and beta-2

    Correct Answer
    C. M2 and M3
    Explanation
    Answer: C
    The woman was most likely taking amitriptyline, an antidepressant medication with pronounced
    antimuscarinic effects. Palpitations is due to blockade of M2 receptors whereas dry mouth,
    blurred vision and constipation are due to blockade of M3 receptors.
    A, B, D, E) blockade These pairs of receptors do caused the symptoms reported by the patient.

    Rate this question:

  • 12. 

    A 2-year-old boy was rushed to the emergency room by his parents after they discovered he had swallowed a nicotine lozenge found in his father drawer. Which of the following expected symptoms of this patient are most likely due to an increased firing of ganglionic sympathetic neurons?

    • A.

      Nausea and Vomiting

    • B.

      Cold and wet skin

    • C.

      Abdominal pain and diarrhea

    • D.

      Salivation and lacrimation

    • E.

      Urinary incontinence

    Correct Answer
    B. Cold and wet skin
    Explanation
    Answer: B
    Activation of nicotinic receptors in sympathetic ganglia cause an increased sympathetic firing
    which in turn releases norepinephrine from adrenergic terminals. This activates alpha-1
    receptors so causing skin vasoconstriction. Therefore the skin becomes pale and cold. The
    increased sympathetic firing also release acetylcholine from terminal innervating sweat glands.
    Sweating is increased and the skin becomes wet.
    A, C, D, E) All these symptoms are due to activation of nicotinic receptors in parasympathetic
    ganglia

    Rate this question:

  • 13. 

    A 2000 gm baby was born at 34 week gestational age by vaginal delivery. One hour after birth the baby appeared hypothermic and lethargic. Apgar scores were low and blood pressure was 55/35 mm Hg. Lab tests revealed that the newborn had a genetic disorder, namely a dopamine beta-hydroxylase deficiency. Lab tests would have also shown which of the following results?

    • A.

      Very low plasma levels of norepinephrine

    • B.

      Very low plasma levels dopamine

    • C.

      High plasma level of epinephrine

    • D.

      High urinary level of normetanephrine

    • E.

      Low urinary levels of homovanillic acid

    Correct Answer
    A. Very low plasma levels of norepinephrine
    Explanation
    Answer: A
    Dopamine beta-hydroxylase is the enzyme that catalyzes the conversion of dopamine into
    norepinephrine. Since the enzyme is lacking plasma levels of norepinephrine will be very low.
    B) Plasma levels of dopamine would be high, not low.
    C) Epinephrine is synthesized from norepinephrine. Since plasma levels of norepinephrine are
    low, also plasma levels of epinephrine must be low, not high.
    D) Normetanephrine is a urinary metabolite of norepinephrine. Since plasma levels of
    norepinephrine are low, also normetanephrine must be low, not high.
    E) Homovanillic acid is the main urinary metabolite of dopamine. Since plasma levels of
    dopamine are high, also homovanillic acid must be high, not low.

    Rate this question:

  • 14. 

    A 61-year-old man suffering from postural hypotension started a therapy with a drug which selectively activates alpha-1 receptors. Which of the following postreceptor mechanisms most likely mediated the therapeutic effect of the drug in this patient?

    • A.

      Increased synthesis of IP3 and DAG

    • B.

      Closing of ligand-gate Ca++ channels

    • C.

      Opening of ligand-gated K+ channels

    • D.

      Opening of voltage-gate Na+ channels

    • E.

      Increased synthesis of cAMP

    Correct Answer
    A. Increased synthesis of IP3 and DAG
    Explanation
    Answer: A
    Activation of alpha-1 receptors constrict the vessels so counteracting the postural hypotension
    of the patient. The postreceptor mechanism which mediates the effect must be one that
    increases intracellular calcium, since calcium is needed for contraction. Alpha-1 receptor
    activation increases the This is achieved by activating phospholipase C which in turn in
    creased the synthesis of IP3 and DAG.
    B, C, D, E) (see explanation above)

    Rate this question:

  • 15. 

    A 84-year-old woman resident of a nursing facility complained of a need to strain to void the bladder, and a sense of incomplete voiding. Postvoiding bladder catheterization produced a residual urine volume of 120 mL. The patient was given a cholinesterase inhibitor that increased the amount of acetylcholine in the synaptic cleft and was able to improve voiding. This effect most likely resulted from the activation of which of the following pairs of receptors?

    • A.

      M2 and Alpha-1

    • B.

      Alpha-1 and beta-2

    • C.

      M3 and Nn

    • D.

      Beta-1 and beta2

    • E.

      M2 and Nm

    Correct Answer
    C. M3 and Nn
    Explanation
    Answer: C
    Drugs that inhibit cholinesterase are able to increase the amount of acetylcholine released by
    all cholinergic terminals, that is preganglionic terminals, postganglionic parasympathetic
    terminals and neuromuscular junction. In the parasympathetic ganglia located in the bladder
    acetylcholine activates Nn receptors so increasing postganglionic firing. Acetylcholine also
    activates M3 receptors located on the detrusor muscle. Both action contribute to the
    contraction of the detrusor muscle and therefore voiding was improved.
    A, B, D, E) The activation of these receptors does not elicit the contraction of the detrusor
    muscle of the bladder.

    Rate this question:

  • 16. 

    A 25-year-old man suffering from asthma has been prescribed a drug that selectively activates beta-2 receptors. Which of the following adverse effects is most likely to be expected in this patient?

    • A.

      Diarrhea

    • B.

      Urinary incontinence

    • C.

      Skin rash

    • D.

      Palpitations

    • E.

      Impairment of far vision

    Correct Answer
    D. Palpitations
    Explanation
    Answer: D
    Activation of beta-2 receptors often causes palpitations that most likely occur for the following
    reasons.
    1) The activation causes dilation of the skeletal muscle vessels which in turn may cause reflex
    tachycardia.
    2) The activation of beta-2 receptors in the heart may contribute to the increase in heart rate
    [direct cardiac effects are determined largely (60-80%) by activation of beta-1 receptors, but
    activation of beta-2 receptors is also involved (20-40%)]
    A, B) These adverse effects are mainly due to parasympathetic activation.
    C) A skin rash is due to an allergic reaction in most cases.
    E) Beta-2 receptor activation relaxes the ciliary muscle and therefore the far vision should be
    improved, not impaired. The effect however is weak and accommodation is not disturbed.

    Rate this question:

  • 17. 

    A 48-year-old woman, who has been suffering from type I diabetes for 15 years, has been recently diagnosed with diabetic autonomic neuropathy. Main symptoms of the disease include xerostomia, abdominal distension, constipation, anhydrosis, urinary retention and vaginal dryness. These symptoms most likely result from an impairment of autonomic transmission at which of the following receptors?

    • A.

      Alpha-1

    • B.

      Alpha-2

    • C.

      M2

    • D.

      M3

    • E.

      Nm

    Correct Answer
    D. M3
    Explanation
    Answer: D
    Symptoms like xerostomia, anhydrosis and vaginal dryness indicate an impairment of
    secretions from exocrine glands. Symptoms like abdominal distension, constipation and urinary
    retention indicate an impairment of contraction of nonvascular smooth muscles. Exocrine gland
    secretion and nonvascular smooth muscle contraction are elicited by the activation of M3
    receptors.
    A) Blockade of alpha-1 receptors would cause mainly vasodilation which in turn would
    decrease the blood pressure.
    B) Alpha-2 receptors are mainly presynaptic receptors. A blockade of these receptors would
    cause mainly an increase of norepinephrine release from adrenergic terminals.
    C) Blockade of M2 receptors would decrease the parasympathetic control of heart activity so
    leading to an increase in heart rate and contractility.
    E) Blockade of Nm receptors would cause a paralysis of skeletal muscles.

    Rate this question:

  • 18. 

    A 63-year-old man suffering from open angle glaucoma has been receiving an autonomic drug locally in the conjunctival sac. The drug causes a decreased of pupillary diameter and an increase of lens curvature. These actions are most likely mediated by which of the following postreceptor mechanisms?

    • A.

      Increased synthesis of IP3 and DAG

    • B.

      Increased synthesis of eicosanoids

    • C.

      Opening of ligand-gated K+ channels

    • D.

      Opening of ligand-gated Na+ channels

    • E.

      Increased synthesis of cAMP

    Correct Answer
    A. Increased synthesis of IP3 and DAG
    Explanation
    Answer: A
    A decrease in pupillary diameter (miosis) is due to the contraction of the sphincter muscle of
    iris, which is elicited by the activation of M3 receptors. An increase in lens curvature is due to
    the contraction of the ciliary muscle which is also elicited by the activation of M3 receptors. The
    main postreceptor mechanism of M3 receptors is the increased synthesis of IP3 and DAG
    which in turn increases intracellular CA++. Calcium is needed for several parasympathetic
    actions including smooth muscle contraction and exocrine gland secretion.
    B) This postreceptor mechanism is triggered by the activation of alpha-1 receptors.
    C) This postreceptor mechanism is triggered by the activation of M2 receptors.
    D) This postreceptor mechanism is triggered by the activation of Nm receptors.
    E) This postreceptor mechanism is triggered by the activation of beta receptors.

    Rate this question:

  • 19. 

    The cardiovascular effects of a new autonomic drug that does not cross the blood brain barrier are evaluated in a healthy volunteer. The drug was administered intravenously and the results are tabulated below. Which of the following receptors did the drug most likely activate?

    • A.

      Alpha-1

    • B.

      Beta-1

    • C.

      D-1

    • D.

      M2

    • E.

      M3

    Correct Answer
    D. M2
    Explanation
    Answer: D
    M2 receptors are mainly located on the heart and their activation decreases the heart rate and,
    to a lesser extent, heart contractility. Systolic blood pressure, which is also dependent on heart
    contractility, will be decreased slightly. Diastolic blood pressure depends on total peripheral
    resistance and therefore is not affected by the activation of M2 receptors that has nothing to do
    with the contractility of vascular smooth muscle.
    A) Activation of alpha-1 receptors would cause vasoconstriction and therefore an increase of
    systolic as well as diastolic blood pressure.
    B) Activation of beta-1 receptors would increase cardiac contractility and rate.
    C) Activation of D-1 receptors would cause dilation of mesenteric and renal vessels, so
    decreasing the diastolic blood pressure.
    E) Activation of M3 receptors would cause a release of nitric oxide from the vascular
    endothelium, so decreasing the diastolic blood pressure.

    Rate this question:

  • 20. 

    A 35-year-old farmer is brought to the emergency room with severe abdominal cramps and vomiting. He refers that he was working in the field with an organophosphate pesticide and presents with all typical symptoms of acetylcholine excess. Which of the following symptoms of the patient are most likely due to the activation of nicotinic Nm receptors only?

    • A.

      Salivation, decreased blood pressure

    • B.

      Difficulty in breathing, miosis

    • C.

      Diarrhea, sweating

    • D.

      Bradycardia, urinary urgency

    • E.

      Diplopia, difficulty in swallowing

    Correct Answer
    E. Diplopia, difficulty in swallowing
    Explanation
    Answer: E
    Nm receptors are found only in the motor endplate and therefore the symptoms must refer to
    skeletal muscles. When Nm receptor are activated by acetylcholine the ion channel opens so
    allowing Na+ to enter the cell. The endplate membrane become depolarized and this
    depolarization is called endplate potential. If its amplitude reaches the threshold for excitation
    voltage-gated Na+ channels open, so generating an action potential that propagates the
    depolarization and causes the contraction of the skeletal muscle. The endplate depolarization
    is short-lasting, since acetylcholine is rapidly metabolized. However when an excessive amount
    of acetylcholine causes a persistent activation of Nm receptors, a loss of electrical excitability
    of the muscle cell occurs. The main reason for this loss is that, even if the membrane is still
    depolarized because of the activation of Nm receptors, voltage-sensitive sodium channels
    become inactivated and therefore not able to open in response to a brief depolarizing stimulus.
    This loss of electrical excitability in the presence of a depolarized membrane is called
    “Depolarization blockade”. The main consequence of this block in skeletal muscle cells is the
    paralysis of the muscle. It should be noted that this paralysis is not due to the blockade of Nm
    receptors but to the persistent activation of those receptors. When the paralysis involves the
    extrinsic muscles of the eye, diplopia results. The paralysis of the striated muscles of the
    pharynx causes difficulty in swallowing.
    A, B, C, D) All these effects are due to the activation of muscarinic receptors.

    Rate this question:

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