EXCITABLE TISSUES
1. In neurons, the resting membrane potential is usually about
a. –50mV
b. –60mV
c. –70mV
d. –80mV
e. –90mV
2. Regarding muscle fibres, which of the following is true?
a. The thick filaments are made up of actin, tropomyosin and troponin
b. The thick filaments form the A bands - true
c. Z lines connect to the thick filaments
d. The sarcomere is the area between 2 adjacent M lines – Z lines
e. Z lines move apart during contraction - together
3. Regarding cholinergic transmission, which of the following is true?
a. Only muscarinic receptors are found in the brain – no, many nicotinic are presynaptic and
important in facilitating the release of GABA (there are post and peri synaptic also). The nicotinic are
made from 5 subunits from a possible 16, varying in age and location
b. Synthesis of acetylcholine occurs in synaptic vesicles – no synthesis occurs, then the transmitter is
taken up into the small clear vesicles
c. Removal of acetylcholine from the synapse is mainly by reuptake – mainly by hydrolysis via postsynaptic acetyecholinesterase
d. Pseudocholinesterase is mainly responsible for hydrolysis of acetylcholine – no, as above, but the
acetylcholine that enters the circulation is hydrolysed by this enzyme
e. Synthesis of acetylcholine involves the reaction of choline with acetate <- true
4. Nicotinic receptors are:
a. Transmembrane cell surface receptors coupled to G proteins
b. Found as post-synaptic receptors on sweat glands
c. Post synaptic receptors on parasympathetic effector organs (except sweat glands)
d. Activated by neuropeptide Y
e. Transmembrane ion channels
5. With respect to gamma-aminobutyric acid (GABA):
a. GABA exerts neuroinhibition by decreasing plasma Na+ conductance – GABA-A increases Cl-,
GABA-B increases K+, decreases Ca2+ conductance and inhibit adenylcyclase, GABA-C in retina
b. After release into the synapse, there is active presynaptic uptake of GABA - ?
c. “stiff man syndrome” is due to increased activity at GABA centrally - ?
d. GABA is synthesized in the presynaptic neuron by GABA transaminase (GABA-T) <- true
e. GABA is the primary neurotransmitter in approximately 40% of CNS synapses – main inhibitory
neurotransmitter, but glutamate is main excitatory (75% of excitation)
6. With regard to the neuromuscular junction:
a. There is convergence of inputs to the motor endplates
b. The junctional folds of the terminal buttons of the motor neuron allow greater surface area for the
increased release of acetylcholine
c. Binding of acetylcholine to the motor end plate increases the conductance of Na+ and K+
d. Random release of acetylcholine is proportional to the local concentrations of Ca2+ and Mg2+
e. Myasthenia gravis results from a genetically determined defect in the nicotinic acetylcholine
receptor at the neuromuscular junction
7. The action potential of a neuron:
a. Is initiated by efflux of Na+
b. Is terminated by efflux of K+ <- repolarization is due to closure/inactivation of the Na+ channels
and opening of the K+ channels
c. Declines in amplitude as it moves along the axon
d. Results in transient reversal of the concentration gradient of Na+ across the cell membrane –
transient reversal of the electrical gradient of Na+
e. Is not associated with any net movement of Na+ or K+ across the cell membrane
8. The functions of tropomyosin in skeletal muscle include:
a. Releasing Ca2+ after an action potential
b. Sliding on actin to produce shortening
c. Binding to myosin during contraction
d. Acting as a “relaxing protein” at rest by covering up the sites where myosin binds to actin
e. Generating ATP which passes to the contractile mechanism
9. Which of the following is NOT synthesized in post-ganglionic sympathetic neurons?
a. L-dopa
b. Dopamine
c. Noradrenaline
d. Adrenaline <- it is in the adrenal medulla
e. Acetylcholine <- it is for the innervation of sweat glands
“At the synapses within the ganglia, preganglionic neurons release acetylcholine, a neurotransmitter
that activates nicotinic acetylcholine receptors on postganglionic neurons. In response to this
stimulus postganglionic neurons - with two important exceptions - release norepinephrine, which
activates adrenergic receptors on the peripheral target tissues. The activation of target tissue
receptors causes the effects associated with the sympathetic system.
The two exceptions mentioned above are postganglionic neurons innervating sweat glands—which
release acetylcholine for the activation of muscarinic receptors - and the adrenal medulla. The
adrenal medulla develops in tandem with the sympathetic nervous system, and acts as a modified
sympathetic ganglion: synapses occur between pre- and post- ganglionic neurons within it, but the
post ganglionic neurons do not leave the medulla; instead they directly release norepinephrine and
epinephrine into the blood”
10. During skeletal muscle contraction:
a. Calcium binds to troponin I
b. The length of the A band decreases
c. Energy is mainly derived from glucose at rest
d. Calcium is released from intracellular stores
e. More work is done in isometric than isovolumetric contraction
11. Regarding neuromuscular junction
a. Dopamine is the neurotransmitter
b. Acetylcholine is the neurotransmitter
c. Binding of the neurotransmitter to the muscle causes influx of Ca2+
d. Binding of the neurotransmitter to the muscle decreases the conductance of Na+ and K+ through
the membrane
e. Neurotransmitter is removed from the synaptic cleft by re-uptake
12. The actions of B1 receptors include:
a. Vasodilation in skeletal muscle
b. Renin secretion from juxtaglomerular cells
c. Decreased insulin and glucagons secretion from pancreatic islet cells
d. Pilomotor muscle contraction in the skin
e. Gall bladder contraction
13. In mammalian mixed nerves:
a. Type A beta fibres conduct motor impulses to muscle spindles – A gamma
b. Type B fibres are preganglionic autonomic nerve fibres <- true
c. Type C fibres have a diameter of 12-20 micrometres – 0.4-1.2
d. Type A fibres have a slower conduction velocity than type C fibres - faster
e. Type A alpha fibres are concerned with touch and pressure – A beta
14. Regarding resting membrane potentials:
a. Changes in the external Na+ concentration affects the magnitude of the cardiac action potential
b. Changes in the external K+ concentration affects the magnitude of the action potential
c. The slow Ca2+ channel is activated at the membrane potential of 0mV in cardiac cells
d. The resting membrane potential of skeletal muscle is about 50mV
e. There are two types of K+ channels that produce repolarisation in cardiac cells
15. Regarding the action potential:
a. The outside of the membrane becomes positive during an action potential when depolarized negative
b. The speed of conduction is decreased in myelinated cells
c. The speed of conduction is increased in antidromic conduction
d. The speed of conduction is greater in A fibre types, compared with C fibre types <-true
e. Phase I in cardiac muscle cells is caused by an influx of Na+ - phase 0
16. Contraction of skeletal muscle involves:
a. Uncovering of myosin binding sites on tropomyosin – on actin
b. Pumping of Ca2+ into sarcoplasmic reticulum - from
c. Binding of Ca2+ to troponin I – troponin c
d. Spread of depolarization along T tubules
e. Binding of acetylcholine to muscarinic acetylcholine receptors – nicotinic for skeletal
17. Acetylcholine:
a. Is formed by the action of acetylcholinesterase
b. Only binds to muscarinic receptors
c. Has a receptor that consists of 2 alpha and 2 beta subunits
d. Is synthesized in neurons
e. Is held in granulated vesicles by an active transport system
18. Skeletal muscle
a. Has a muscle twitch starting 7.5ms after depolarisation
b. Myosin I has two globular heads and a long tail
c. Thick filaments contain 300-400 actin molecules
d. Troponin is made up of three subunits <- correct, I (inhibits myosin-actin binding site), T
(tropomyosin binding site), and C (Ca2+ binding site)
e. None of the above are true
19. Nerve fibres
a. Of type B are unmyelinated
b. Of type C transmit pain and cold sensations <- also true, pain and temperature, although pain, cold
and touch also by A delta or type III
c. To skeletal muscle conduct impulses at 15-30 m/sec
d. To muscle spindles are type B
e. Involved in proprioception are type A-alpha fibres <- true (or Ia), A-alpha also in somatic motor
20. Regarding the stretch reflex
a. It is a monosynaptic reflex
b. Impulses are conducted in the CNS by slow sensory fibres
c. The neurostransmitter at the neuromuscular junction is glutamate
d. The flower spray endings are the primary sensory endings of the muscle spindle
e. Each muscle spindle contains 40 muscle fibres in a capsule
21. Regarding the stretch reflex:
a. The harder a muscle is stretched the stronger the reflex contraction – more rapid, hard stretch can
lead to inverse stretch reflex
b. Relaxation in response to stretch is the inverse stretch reflex <- true, via golgi tendon organ
c. The tendon stretch afferent pathway is via C fibres - Ia i.e A-alpha
d. Golgi tendon organs are stimulated mainly by passive stretch of the muscle
e. Muscle spindles fire more rapidly in sustained stretch – dynamic change (i.e. in length)
22. Muscle spindles
a. Receive efferent input from alpha and beta nerve fibres – efferent input is from gamma, but
afferent output is via A alpha (Ia) and A beta (II) (the golgi tendon afferent is A alpha but Ib)
b. Produce only dynamic sensory nerve patterns – dynamic and static
c. Have intrafusal fibres running perpendicular with extrafusal fibres – in parallel
d. Have “flower spray” sensory endings
e. Are desensitized by anxiety <- correct answer?
23. regarding smooth muscle
a. it has striations
b. it depends on troponin for contraction
c. hypertrophy contributes to the pathogenesis of hypertension and atherosclerosis
d. its growth is stimulated by glucocorticoids
e. none of the above are true
24. What does presynaptic inhibition require?
a. Contact of an inhibitory neuron
b. ?
c. ?
d. ?
e. ?
25. Calmodulin is involved in
a. Smooth muscle contraction
b. Smooth muscle relaxation
c. Myocardial contractility
d. ?
e. ?
26. Which of the following is true?
a. Contraction of cadiac muscle is about as long as its action potential
b. ?
c. ?
d. ?
e. ?
27. In contracting skeletal muscle
a. The H zone increases
b. The I zone decreases
c. The A zone increases
d. ?
e. ?
28. With regards to the action potential in a neuron with a RMP of –70mV
a. The firing level is likely to be –30mV
b. The overshoot will not extend much past 0mV
c. The absolute refractory period occupies only 10% of repolarisation
d. Chloride influx will restore the membrane potential
e. Increase of the external [chloride] increases the resting membrane potential
29. In skeletal muscle
a. Tropomyosin is made up of 3 subunits
b. The heads of actin contain an ATP hydrolysis site
c. The myosin is contained entirely within the A band
d. Troponin T inhibits the interaction with myosin
e. The immediate energy source for contraction is GTP
30. The action potential of a cardiac muscle fibre
a. The resting membrane is –50mV
b. Phase 1 is due in part to rapid chloride influx
c. Sodium channels are progressively inactivated during phase 2
d. The repolarisation time increases as heart rate increases
e. Is usually of 20ms duration
31. The special feature of the contraction of smooth muscle is that:
a. Actin is not involved
b. Myosin is not involved
c. Calcium is not involved
d. ATP is not the energy source
e. The membrane potential is unstable
32. Inhibitory neurotransmitters increase the post synaptic conductance to
a. Sodium
b. Chloride
c. Magnesium
d. Sodium and magnesium
e. All of the above
33. All of the following are neurotransmitters EXCEPT:
a. Serotonin
b. Glutamate
c. Adenosine
d. Insulin
e. Glucagon
34. (true) acetylcholinesterase
a. forms acetylcholine from acetate
b. is produced by the liver
c. functions only in nerve endings
d. is involved in GABA metabolism
e. none of the above
35. in the formation of adrenaline
a. COMT produces adrenaline from noradrenaline
b. Phenylalanine is converted to tyrosine
c. Dopa is formed by dopa decarboxylase
d. Dopamine is two noradrenaline molecules bound side by side
e. Serotonin formation is a vital intermediate step
36. MAO breaks down
a. Serotonin
b. Tryptophan
c. GABA
d. Glutamate
e. Glycine
37. In smooth muscle the alternating sinusoidal RMP is due to
a. Calcium influx
b. Sodium influx
c. Potassium influx
d. Chloride influx
e. Potassium efflux
38. With respect to the cardiac action potential
a. Unlike nerve ation potential there is no overshoot
b. Plateau and repolarisation may be 200 times larger than depolarization phase
c. The resting membrane potential is –90mV
d. Sodium channels are progressively inactivated in phase 2
e. It is usually 20ms in duration
39. upon stretching intestinal smooth muscle
a. it hyperpolarizes
b. the tension is due to elastic forces only
c. it depolarizes
d. relaxation occurs
e. it is an example of a multi-unit smooth muscle
40. Upon skeletal muscle contraction
a. The H zone increases
b. The I zone decreases
c. The A zone decreases
d. The A and I zones increase
e. None of the above
41. All of the following are true of skeletal and cardiac muscle EXCEPT:
a. They both have striations
b. They have high resistance gap junctions
c. ?
d. ?
e. ?
42. With respect to smooth muscle, calmodulin
a. Acts to curtail contraction
b. Acts to stimulate contraction
c. Acts to limit relaxation
d. Acts to stimulate relaxation
e. ?
43. Regarding synaptic transmission:
a. A synaptic cleft is 1000nm wide
b. Synapses allow retrograde transmission of action potentials
c. Presynaptic fibres end only on dendritic spines
d. The average neuron divides to over 2000 synaptic endings
e. Presynaptic knobs contribute only a small portion of the dendritic membrane area
44. The knee jerk:
a. Utilises glutamate as the central synapse neurotransmitter
b. Is mediated by gamma afferents
c. Is a good example of a polysynaptic reflex arc
d. Involves relaxation of the antagonistic muscle due to the Golgi tendon organ
e. Is initiated by stimulation of the sensory extrafusal fibres
45. The kappa receptor
a. Is involved in spinal analgesia
b. Is respondible for dysphoric reactions and hallucinations
c. Is responsible for euphoria, dependence and analgesia
d. ?
e. ?
46. The main inhibitory neurotransmitter of the spinal cord is
a. Glycine
b. GABA
c. Ach
d. Dopamine
e. Substance P