Part As - 2007-2011 Flashcards by Ursula B

Is the resting membrane of an excitable cell many times MORE/LESS permeable to sodium compared to potassium?

Less

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Is the Na+/K+ ATPase pump necessary to restore the membrane potential to its resting value at the end of an action potential?

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Increasing the external potassium concentration HYPERPOLARISES/DEPOLARISES the resting membrane potential of an excitable cell

Depolarises

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Will the resting membrane potential of this excitable cell be the same as the potassium equilibrium potential (Ek)?

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Cardiac dysrhythmia drug

beta-adrenoceptor antagonist

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Nasal decongestant

alpha1-adrenoceptor agonist

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Suppression of contractions during pregnancy

beta2-adrenoceptor agonist

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Myasthenia gravis drug

cholinesterase inhibitor

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Ophthalmic inspection

muscarinic receptor antagonist

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A patient who has ingested an unknown drug presents with the following symptoms:
 increased salivation
 difficulty with breathing
 decreased heart rate
 hypotension
 abdominal colic
 pupillary constriction
From the list provided select: The class of drug that probably caused these effects

inhibitor of cholinesterase

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muscarinic receptors

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A patient who has ingested an unknown drug presents with the following symptoms:
 increased salivation
 difficulty with breathing
 decreased heart rate
 hypotension
 abdominal colic
 pupillary constriction
From the list provided select: A drug class that might worsen the difficulty with breathing

beta2-adrenoceptor antagonist

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alpha1-adrenoceptor antagonist

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muscarinic receptor antagonist

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The main neurotransmitter released from preganglionic parasympathetic neurones is

acetylcholine

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The main action of this neurotransmitter on the postganglionic parasympathetic neurones is

excitation

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Excitation is mediated by

nicotinic cholinergic receptors

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The main neurotransmitter released from postganglionic parasympathetic neurones is

acetylcholine

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Parasympathetic ACh acts on

muscarinic cholinergic receptors

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Lidocaine

Na+ channel blocker

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Propranolol

beta-adrenoceptor antagonist

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Amiodarone

K+ channel blocker

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Verapamil

Ca2+ channel blocker

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Adenosine

Purinergic receptor agonist

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From the following list select four factors that increase the velocity of conduction of an action potential in nerve fibres

decrease in external resistance
decrease in internal resistance
decrease in membrane capacitance
increase in membrane resistance

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What is the velocity of conduction in A alpha nerve fibres?

100 m/sec

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Select the membrane channel responsible for the inward current during the depolarising phase of the action potential in nerve fibres

voltage-gated Na+ channel

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Name one drug that blocks Na+ channels

tetrodotoxin - TTX

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Select which membrane channels are responsible for the repolarising phase of the action potential in nerve fibres

delayed rectifier K+

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Name a drug that blocks K+ channels

tetraethylammonium - TEA

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What accounts for the absolute refractory period that follows an action potential

voltage-gated Na+ channel

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Ouabain acts on

Na+/K+ ATPase

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Tetrodotoxin acts on

Voltage gated sodium channels

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Tetraethyl ammonium ion acts on

Voltage gated potassium channels

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cAMP acts on

Protein kinase A

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Neostigmine acts on

Acetylcholinesterase

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Therapeutic use of Beta 2 adrenoceptor agonist

Asthma

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Therapeutic use of Cholinesterase inhibitors

Myasthenia gravis

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Therapeutic use of inhibitor of angiotensin converting enzyme

Hypertension

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Therapeutic use of Na+ channel blocker

Cardiac dysrhythmia

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Therapeutic use of Inhibitor of H+/K+ ATPase

Peptic ulcer

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Example of a non-depolarizing blocking agent at the neuromuscular junction

Tubocurarine

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Example of an irreversible antagonist of a metabolic enzyme

Aspirin

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Example of a stimulant at the autonomic ganglia

Nicotine

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Example of a blocker of vesicular transport

Reserpine

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Example of a a reversible competitive antagonist on gastro-intestinal smooth muscle

Atropine

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Match from the drop-down list below the following receptors or enzymes to the principal second messenger response which they elicit: Muscarinic M2 receptor

cAMP fall

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Match from the drop-down list below the following receptors or enzymes to the principal second messenger response which they elicit: Oxytocin receptor

IP3 rise

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Match from the drop-down list below the following receptors or enzymes to the principal second messenger response which they elicit: β2-adrenoceptor

cAMP rise

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Match from the drop-down list below the following receptors or enzymes to the principal second messenger response which they elicit: α1-adrenoceptor

IP3 rise

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Match from the drop-down list below the following receptors or enzymes to the principal second messenger response which they elicit: Nitric oxide synthase

cGMP rise

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Noradrenaline in peripheral sympathetic nerves is released from preganglionic sympathetic nerves

False

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Noradrenaline in peripheral sympathetic nerves is synthesised from dopamine

True

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noradrenaline in peripheral sympathetic nerve transport into presynaptic vesicles is proton-dependent

True

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noradrenaline in peripheral sympathetic nerve action is terminated by transporters located both pre- and postsynaptically

True

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noradrenaline in peripheral sympathetic nerves once released - its action is blocked by an inhibitor of tyrosine hydroxylase

False

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Example of an acetylcholinesterase inhibitor

physostigmine

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Does Cl- contribute to the downstroke of the action potential?

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Which ion makes the greatest contribution to the resting membrane potential?

K+

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Rigor Mortis is due to myoplasmic ATP depletion. This results in rigor because

myosin head remains attached to actin

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Acts on a Nicotinic receptor

Alpha-bungarotoxin

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Acts on an Epithelial sodium channel

Amiloride

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Acts on Voltage-gated calcium channel

Nifedipine

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What is a clinical use for an inhibitor of voltage gates Na+ channels?

local anaesthetic

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Which type of ion channel underlies the upstroke of the action potential in smooth muscle?

Ca2+

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State a molecule that can inhibit Ca2+ channels

verapamil

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Example of an Alpha 1 receptor agonist

phenylephrine

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Example of an Alpha 1 receptor antagonist

prazosin

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Example of an Inhibitor of noradrenaline release

guanethidine

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Example of an Uptake 1 inhibitor

Cocaine

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Example of a Beta receptor agonist

isoprenaline

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The mechanism of action of depolarizing blockers at the vertebrate neuromuscular junction involves competitive antagonism of Nicotinic receptors

False

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The mechanism of action of depolarizing blockers at the vertebrate neuromuscular
junction involves inactivation of voltage gated sodium channels in muscle fibres

True

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The mechanism of action of depolarizing blockers at the vertebrate neuromuscular junction involves stimulation of nicotinic receptors

True

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The mechanism of action of depolarizing blockers at the vertebrate neuromuscular junction involves blockade of voltage gated calcium channels

False

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The mechanism of action of depolarizing blockers at the vertebrate neuromuscular junction involves inhibition of acetylcholine release from motoneurones

False

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What is the typical concentration of intracellular K+?

140 mM

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What is the typical concentration of intracellular Na+?

15 mM

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At rest, is the normal cell membrane more permeable to Na+ or K+?

more permeable to K+

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What is the stoichiometry and direction of Na+ and K+ movements powered by the Na+/K+ ATPase in a resting cell?

3Na+ out and 2K+ in

Myelination increases conduction velocity because it

Decreases membrane capacitance

One mechanism that releases the ion from the endoplasmic (or sarcoplasmic) reticulum

IP3

A calcium binding protein that mediates the effects of calcium

Calmodulin

A calcium-activated enzyme that stimulates smooth muscle contraction

myosin light chain kinase (MLCK)

Example of a ganglion blocker

trimetaphan

Action potential conduction velocity in the largest myelinated nerve fibre is

120 m/s

Myelination increases conduction velocity because it

permits saltatory conduction

The sequence of nerve block by local anaesthetics is

pain first, then general sensory, then motor last

A clinical use of a voltage-gated K+ channel blocker is

antidysrhythmic

A depolarising blocker at the skeletal neuromuscular junction

suxamethonium

A blocker of autonomic ganglia receptors

hexamethonium

Sympathetic nerves innervate the motor endplate in skeletal muscle

False

Parasympathetic nerves innervate the motor endplate in smooth muscle

False

Smooth muscle of the gastrointestinal tract is directly innervated mainly by
sympathetic nerves

False

Parasympathetic nerves contract bladder smooth muscle

True

Insulin is a

tyrosine kinase receptor

Noradrenaline in peripheral sympathetic nerves is released from preganglionic sympathetic nerves.

False

Noradrenaline is synthesised outside the vesicle in nerve terminals and then transported into the vesicle

False

Released NA acts on muscarinic M3 receptors in bladder smooth muscle

False

Once released the action of NA is terminated by tyrosine hydroxylase

False

NA, by action at beta1-adrenoceptors, increases cAMP levels in the heart

True

Nicotinic ACh receptors are found in

parasympathetic ganglia

Muscarinic ACh receptors are found in

endothelial cells

Bradycardia is produced by acetylcholine action on

M2 muscarinic cardiac receptors

The TWO main mechanisms underlying bradycardia are

a decrease in cAMP and potassium channel activation

The upstroke of the action potential in cardiac pacemaker cells is due to

L type voltage-gated Ca2+ channels

Hyperpolarisation is due to

voltage-gated K+ channels

Regarding the rate of rise of the cardiac action potential, local anaesthetics will

decrease it

Cortisol is produced in the

adrenal cortex

The upstroke of the action potential in skeletal muscle is usually blocked by calcium channel blockers

False

Skeletal muscle fibres have a well-defined t-tubule system

True

Sarcomeres are poorly developed in skeletal muscle

False

Troponin C binds calcium and initiates cross bridge cycling

True

The endplate potential is initiated by the actions of acetylcholine released from somatic motor nerves acting at muscarinic M3 receptors

False

An example of a primary active ion-transporter is

SERCA (sarcoplasmic endoplasmic reticular Ca2+- ATPase)

An example of a secondary active ion transporter is

Na+ -glucose symporter

The Na+ /K+ ATPase is directly inhibited by the drug

cardiac glycoside

and (v) Na+ /K+ ATPase inhibition causes the following two effects

Fall of intracellular K+ and rise of intracellular Na+

The typical equilibrium potential for K+ ions (EK) across the plasmalemma of a resting nerve cell (measured inside relative to outside; in mV) is

-90

The typical equilibrium potential for Na+ ions (ENa) across the plasmalemma of a resting nerve cell (measured inside relative to outside; in mV) is

Raising the extracellular K+ concentration bathing a nerve cell would

make Ek less negative (more positive)

Reducing the extracellular concentration of Na+ ions would

Make ENa more negative (less positive)

Noradrenaline released at a noradrenergic synapse is removed from the cleft by

Both presynaptic and postsynaptic reuptake

Acetylcholine applied to the heart

Decreases atrial contractility

Which of the following drugs is a Ca2+ channel antagonist that may be used for treatment of cardiac arrhythmias?

verapamil

The major excitatory receptor on skeletal muscle

Nicotinic acetylcholine receptor

The major mammalian presynaptic channel controlling transmitter release

Neuronal calcium channel

Enzyme for breaking down acetylcholine

AChE

Depolarizing NMJ blocker

Suxamethonium

Non-depolarizing NMJ blocker

Tubocurarine

Action potentials occur in most smooth muscles

True

Intracellular cAMP generally contracts smooth muscle cells

False

Smooth muscle contraction is generally faster than cardiac muscle

False

Troponin C is the major calcium regulated protein in the control of smooth muscle contractility

False

Neurotransmitters often evoke smooth muscle contraction by stimulating a rise in inositol trisphosphate (IP3)

True

Catecholamine neurotransmitter example

Noradrenaline

Thin filaments

Actin

thick filaments

Myosin

Where are calcium release channels located in skeletal muscle

Sarcoplasmic reticulum (SR)

Where are nicotinic receptors on skeletal muscle located

Sarcolemma

During contraction, which of the following remains constant in length?

I band

The major adrenoceptor in ventricular muscle whose activation increases cardiac contractility

β1

The adrenoceptor in liver cells whose activation leads to glycogenolysis

α1 and β2

An adrenoceptor whose activation leads to vascular smooth muscle contraction

α1

an adrenoceptor whose activation leads to vascular smooth muscle relaxation

β2

a presynaptic adrenoceptor whose activation leads to decreased neurotransmitter release

α2

A doubling of the intracellular Na+
ion concentration will … membrane
ion transport by Na+ /K+ ATPase proteins.

Stimulate

A change of extracellular K+ ion concentration to 2.0 mM will … membrane ion transport by Na+ /K+ ATPase proteins.

Decrease

A selective inhibitor of Na+ /K+ ATPase proteins is

Digoxin

The Na+/K+ ATPase protein is

primary active ion transporter

The depolarization phase (from point A-C) of an action potential is mediated by ionic current flow through

voltage-gated Na+ channels

The initial (local) depolarization (immediately after point A) is mediated by

ligand-gated ion channels

From region C to D the process primarily responsible is ionic current flow through

voltage-gated K+ channels

Membrane potential at point E is more negative than point A due to

open K+ channels

Local anaesthetics act directly on

voltage-gated Na+ channels

Ionotropic receptors

are ligand gated ion channels

Metabotropic receptors

are coupled downstream to G proteins

Sympathetic nerves constrict blood vessels

by releasing noradrenaline that binds to α1 receptors

Synaptic transmission at sympathetic autonomic ganglia is blocked by

a nicotinic antagonist

Electrical coupling between adjacent cardiac myocytes is blocked by

a rise of intracellular [H+]

Contraction in fast twitch skeletal muscle is caused by

an action potential propagating in the transverse tubules

Skeletal muscle relaxation is mediated by

pumping of Ca2+ into the sarcoplasmic reticulum

Myocardial contraction is

reduced by verapamil

Contraction of vascular smooth muscle can typically be caused by

IP3 dependent release of sarcoplasmic reticular Ca2+

Contraction of skeletal muscle fibres is triggered by activation of sarcolemmal

nicotinic receptors

Beta adrenergic receptors are coupled to the G-protein

Beta adrenergic receptors modulate the concentration of the second messenger

cyclic AMP

Cyclic AMP levels can be decreased by the enzyme

phosphodiesterase

Cyclic AMP activates

Protein kinase A

Methylxanthines inhibit

phosphodiesterase

The extracellular free concentration of Ca2+

1 mM

The extracellular concentration of Na+

140 mM

The intracellular concentration of Na+

15 mM

The intracellular free concentration of Ca2+ is lower than extracellular free Ca2+ concentration by approximately

10,000 fold

The intracellular concentration of K+ is

140 mM

The primary barrier to ion diffusion across membranes is

the hydrophobic core

The resting membrane potential is due to a flow of ions mainly through

K+ channels

The Na+/K+ pump obtains energy from

ATP

Acetylcholine is removed from the neuromuscular junction mainly by

hydrolysis

At the nicotinic acetylcholine receptor, depolarizing neuromuscular blocking drugs are

agonists

At the nicotinic acetylcholine receptor, common non-depolarizing neuromuscular blocking drugs are

competitive antagonists

Non-depolarizing neuromuscular block can be reversed by

neostigmine

The catecholamine neurotransmitters are synthesized from the amino acid

Tyrosine

Activation of alpha1 adrenergic receptors would acutely

Increase blood pressure

Airway smooth muscle can be relaxed by inhalation of a (an)

beta agonist

Catecholamine neurotransmitters are removed from the synapse by

Reuptake

Amphetamines act by

displacing catecholamines from secretory vesicles

In cardiac muscle during a ventricular action potential the rapid depolarization is mediated by

Na+ influx

In cardiac muscle during a ventricular action potential the plateau phase is mediated mainly by

Ca2+ influx

During excitation-contraction coupling in cardiac cells, membrane depolarization is transduced into Ca2+ release from the sarcoplasmic reticulum by

Ca2+ induced Ca2+ release

A stimulant at the autonomic ganglia

Nicotine

A blocker of acetycholine uptake into vesicles

vesamicol

A competitive antagonist of alpha1 adrenoceptors

prazosin

Smooth muscle cells are electrically connected by gap junctions

True

Smooth muscle cells have a well-defined t-tubule system

False

Sarcomeres are poorly developed in smooth muscles

True

Troponin C binds calcium and initiates cross bridge cycling

False

Smooth muscle cells in blood vessels are usually innervated by the sympathetic and parasympathetic nervous systems

False

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Part As - 2007-2011 Flashcards

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