Neuromuscular/CNS

Question 1

19767 – In skeletal muscle
A. phosphocreatine is the initial energy source for contraction
B. Ca\p2\p+ initiates contraction by binding to tropomyosin
C. transverse tubules (T tubules) release Ca\p2\p+ in the vicinity of the myofibrils in contraction
D. the Z lines move closer together in contraction
E. Ca\p2\p+ passively diffuses back into the sarcoplasmic reticulum in relaxation

Answer 1

D
Guyton CHAPTER: 11 PAGE: 122 & 129
C - binding of Ca to troponin
E - Ca actively pumped back to sarcoplasmic reticulum in relaxation

Question 2

23669 – In smooth muscle
1: calmodulin is the regulatory calcium binding protein
2: the T tubules transmit the action potentials
3: the calcium pump is slow-acting in comparison with the calcium pump in skeletal muscle
4: both sarcoplasmic reticulum and the T tubules release Ca\p2+ to initiate contraction

Answer 2

TFTF
Ganong CHAPTER: 3 PAGE: 58

Question 3

27065 – S: Muscular arteries adapt to changing requirements for blood flow in the distal tissues because R: muscular arteries sense and adapt to the flow and pressure in their lumen.

Answer 3

S is true, R is true and a valid explanation of S
The formation of a collateral circulation around occlusions of the femoropopliteal and iliac systems is well known. Sudden occlusions cause dramatic symptoms and signs because the collaterals cannot adapt instantaneously: however, slowly developing occlusions may be tolerated because of the development of a rich collateral supply. The mechanisms by which arteries (and indeed veins) respond to such demands are not fully understood; however, it is clear that they respond to flow velocity. The shear stress in the flowing blood is sensed by endothelial cells, which release vasodilators including nitric oxide. Thus, a high flow demand will in the longer term, cause vessel dilatation. The role of transmural pressure is less clear, but it has been long known that muscular arteries and arterioles constrict in response to increased pressure and dilate in response to diminished pressure. This mechanism, known as myogenic pressure autoregulation, might contribute to dilatation in a collateral vessel when the pressure in its distal segment decreases as the main vessel occludes. Thus, the assertion is true, and the reason given is a justifiable causal explanation

Question 4

22574 – With respect to the metabolism of cardiac muscle
1: normally less than 1% of its total energy liberated is provided by anaerobic metabolism
2: 60% of the energy is provided by carbohydrates
3: less than 5% of the energy is provided by amino acids
4: approximately 35% of the energy is provided by fat

Answer 4

TFTF

Question 5

21863 – Events in contraction of skeletal muscle include
1: release of acetylcholine at motor end plate
2: binding of acetylcholine to muscarinic receptors
3: binding of Ca2+ to troponin C thus uncovering myosin binding sites on actin
4: inward spread of depolarization along sarcoplasmic reticulum

Answer 5

TFTF
Ganong 15th ed. Chapter: 3 Page: 62
2: binding of Ach to nicotinic receptors
4: inward spread of depolarization along T tubules

Question 6

10099 – During muscle contraction
1: the immediate source of energy is NADP
2: the width of the A bands remains constant
3: the electrical and mechanical responses in a single maximal stimulus occur simultaneously
4: Ca++ initiates contraction by binding to troponin C

Answer 6

FTFT
Ganong, 19th ed, Ch 3

Question 7

23914 – During vigorous exercise
1: the efficiency of conversion of nutrient energy into muscle work is of the order of 20% - 25%
2: the efficiency of conversion of nutrient energy into heat is of the order of 20% - 25%
3: oxygen consumption may increase 20-fold in the trained athlete
4: heatstroke is likely to develop when the body temperature passes 41oC

Answer 7

TFTT
Guyton 9th ed. Page: 1068

Question 8

20085 – S . All the energy of an isometric muscle contraction is dissipated as heat BECAUSE R. no external work is done in an isometric contraction

Answer 8

S is true, R is true and a valid explanation of S
Ganong 13th ed. CHAPTER: 3 PAGE: 55-56

Question 9

21263 – Steps in the sequence of events involved in contraction but not relaxation of skeletal muscle include
1: movement of Ca++ toward the lateral sacs of the sarcoplasmic reticulum
2: formation of cross-linkages between actin and the tails of myosin
3: release of Ca++ from troponin
4: lateral movement of tropomyosin

Answer 9

FFFT
Ganong 13th Edition CHAPTER: 1 PAGE: 50 - 52 Table 3-2
1: movement of Ca from terminal cisterns of SR
2: binding of actin to actin-binding site at HEAD of myosin
3: binding of Ca to troponin

Question 10

21468 – The firing of motoneurons
1: can be inhibited by nerve terminals which release glycine
2: can be inhibited by nerve terminals which release gamma-aminobutyric acid
3: is subject to supraspinal control
4: is subject to negative feed-back control by means of Renshaw cells

Answer 10

TTTT
Ganong 13th ed./Guyton 7th ed. CHAPTER: 4/51 PAGE: 74,82-83/ 607

Question 11

19539 – During the relatively refractory period following the action spike in a single squid axon, the intensity of stimulus required to elicit another spike is
A. unchanged
B. reduced
C. unchanged, but produces a smaller spike
D. increased
E. unchanged, but produces a larger spike

Answer 11

D

Question 12

21473 – The sensation of painful stimuli
1: is perceived by specific receptors dedicated to its detection
2: is transmitted by two different nerve fibre systems
3: travel via descending pathways in the dorsal column of the spinal cord
4: is associated with significant levels of substance P in the substantia gelatinosa

Answer 12

FTFT
Ganong 13th Ed. CHAPTER: 7 PAGE: 110-111
2: nociception system + unmyelinated C fibres
3: via ascending pathways in dorsal column –> lateral spinothalamic tract

Question 13

21478 – Nerve growth factor
1: is a polysaccharide with separate subunits and a total molecular weight of approximately 30,000
2: is transported from the neurone cell body to the growing process
3: stimulates the growth of myelinated motor neurons
4: beta subunit has all the nerve growth promoting activity

Answer 13

FFFT
Ganong 11th ed. CHAPTER: 2 PAGE: 44
19078 – Which of the following is NOT
1: protein with 2 alpha, 2 beta, 2 gamma subunits
2: transported from muscles to receptors at nerve ending –> transported retrograde to neuronal cell body
3. does not

Question 14

19078 – Which of the following is NOT a known or suspected neurotransmitter or neural hormone in mammals
A. gastrin-releasing peptide
B. phlorhizin
C. serotonin
D. cholecystokinin octapeptide
E. substance P

Answer 14

B
Ganong 13th Ed. CHAPTER: 4/38 PAGE: 74/591

Question 15

20193 – S. In skin where complete nerve degeneration has occured the triple response to stroking is absent BECAUSE R. the flare of the triple response is mediated by an axon reflex

Answer 15

S is true, R is true and a valid explanation of S
Ganong 13th Ed. Chapter: 32 Page: 518-519

Question 16

20931 – S. During accommodation the curvature of the eye lens decreases BECAUSE R. when viewing a near object the lens ligaments are relaxed by contraction of the ciliary muscle

Answer 16

S is false and R is true
Ganong 13th ed. Chapter: 8 Page: 122

Question 17

20661 – S. Stimulation of sympathetic fibres to human sweat glands causes secretion of sweat BECAUSE R. all sweat glands are activated by noradrenergic nerve fibres

Answer 17

S is true and R is false
Guyton 7th Ed. CHAPTER: 72 PAGE: 852

Question 18

20601 – S. Sympathetic postganglionic terminals release mainly noradrenaline rather than adrenaline BECAUSE R. prior to release, phenylethanolamine-N-methyl-transferase converts adrenaline to noradrenaline

Answer 18

S is true and R is false
Ganong 13th Ed. Ch. 4 P. 77

Question 19

24364 – Features of Parkinsonism include
1: akinesia
2: rigidity
3: hypersalivation
4: athetosis

Answer 19

TTFF
Guyton 9th Ed. Ch: 56 page 728-729 Robbins 6th Ed Ch:30 page 1333.
3: hyposalivation - dry mouth in serotonin syndrome

Question 20

20403 – S. atropine abolishes normal reflex salivary secretion BECAUSE R. Parasympathetic innervation is probably most important for salivary secretion

Answer 20

S is true, R is true and a valid explanation of S
Ganong, 19th Ed Ch 26, Pages: 467-469. Question updated 2 Dec 2002.

Question 21

S: Destruction of the conus medullaris may almost completely paralyse defaecation because R: spinal cord mediated defaecation reflex is integrated in the conus medullaris

Answer 21

S is true, R is true and a valid explanation of S
Guyton, 9th ed, Ch 66

Question 22

22954 – Spontaneous electrical activity is seen in
1: cardiac muscle
2: multi-unit type smooth muscle
3: visceral type smooth muscle
4: skeletal muscle

Answer 22

TFTF
Guyton CHAPTER: 12 PAGE: 141

Question 23

14691 – The vagus nerve supplies
1: sensation to skin of part of the external auditory canal
2: preganglionic cholinergic axons to the cardiac ganglia
3: parasympathetic outflow to the distal two thirds of the colon
4: cholinergic motor fibres to sweat glands

Answer 23

TTFF
Refer to Ganong, 19th Ed, Ch 13, page 216 and following

Question 24

21458 – Which of the following statements are correct?
1: the axons of postganglionic parasympathetic neurones are typically short
2: transmission at parasympathetic ganglia differs pharmacologically from that at sympathetic ganglia
3: the adrenal medulla is functionally a sympathetic ganglion
4: the effectors which receive postganglionic sympathetic nerve supply always contain alpha-adrenoceptors

Answer 24

TFTF
Ganong 13th Ed. CHAPTER: 13 PAGE: 183-185

Question 25

24124 – Sympathetic vasodilator fibres are characterized by the fact that the
1: liberate noradrenaline at postganglionic endings
2: liberate acetylcholine at preganglionic endings
3: relay through the medullary vasomotor centre
4: cannot sustain vasodilatation for more than 30 seconds

Answer 25

FTFT
Ganong 13th ed. Chapter: 14 & 31 Pages: 192-193 495-497

Question 26

22964 – Alpha-adrenergic receptors at sympathetic postganglionic nerve endings
1: are blocked by phenoxybenzamine (dibenzyline)
2: are present in the presynaptic location on the nerve endings
3: are blocked by phentolamine (regitine)
4: mediate their effect by activation of adenylate cyclase

Answer 26

TTTF
Ganong 13th ed. CHAPTER: 4:13 PAGE: 80:188

Question 27

15518 – In relation to the Weber and Rinne tests of hearing using a tuning fork
1: in the Rinne test normal hearing is diagnosed when the sound from the fork is heard equally in both ears
2: in the Rinne test, conduction deafness is diagnosed when the patient cannot hear the vibrations via bone conduction after the sensations have dissipated from air conduction
3: in the Weber test, conduction deafness is diagnosed when the vibration is heard in air after vibrations heard via bone conduction have ceased
4: in the Weber test, nerve conduction deafness is diagnosed in the ‘affected’ ear when the sound is heard louder in the ‘normal’ ear

Answer 27

FFFT
Refer to Ganong, 19th Ed, Ch 9, page 174, Table 9-1

Question 28

14686 – An experimental drug which proves to be a selective beta-2 adrenergic receptor antagonist would be predicted to cause
1: bronchodilation
2: coronary vasodilation
3: peripheral vasodilation
4: tachycardia

Answer 28

FFFF
Refer to Ganong, 19th Ed, Ch 4, page 89 and following

Question 29

15468 – Micturition is a function of
1: a nervous reflex triggered by intravesical pressure
2: voluntary neurological control of the internal sphincter
3: post-ganglionic parasympathetic nerve fibre stimulation
4: sympathetic nerve stimulation of the body of the bladder

Answer 29

TFTF
Refer to Guyton, 9th Ed, Ch 31, page 407; Ganong, 19th Ed, Ch 38, page 693 and following

Question 30

21848 – In the brain
1: little glycogen is stored in neurons
2: the main energy supply is glucose
3: metabolic rate is much higher than the body average
4: neuronal uptake of glucose is insulin-independent

Answer 30

TTTT
Guyton Page: 684

Question 31

22344 – In the mammalian brain
1: a lesion of the post-central gyrus abolishes the perception of sensation
2: representation of lower limb sensation is expected in the midline
3: cortical sensory representation of the trunk occupies a large part of the post-central gyrus
4: projections of afferents on the post-central gyrus are not innate and immutable but may be changed by experience

Answer 31

FTFT
Ganong 13th Ed. CHAPTER: 7 PAGE: 108

Question 32

18910 – Disorders of the cerebellum are associated with all of the following EXCEPT
A. ballism
B. dysmetria
C. dysdiadochokinesia
D. intention tremor
E. hypotonia

Answer 32

A
Ganong 11th Edition CHAPTER: 14 PAGE: 166, 172

Question 33

24119 – Anterolateral cordotomy
1: produces contralateral analgesia
2: leaves discriminative touch sensation intact
3: produces contralateral thermal anaesthesia
4: leaves proprioceptive sensation intact

Answer 33

TTTT
Damage of lateral spinothalamic tract

Question 34

21463 – With respect to autonomic nerve distribution
1: most blood vessels have a parasympathetic nerve supply
2: salivary glands receive both sympathetic and parasympathetic supply
3: sweat glands are supplied by sympathetic neurones releasing noradrenaline
4: most blood vessels have a sympathetic nerve supply

Answer 34

FTFT
Ganong 11th ed. CHAPTER: 13 PAGE: 176
3: sweat glands supplied by post-ganglionic CHOLINERGIC neurons

Question 35

13415 – S: Dopamine and L-dopa cross the blood-brain barrier and are therefore useful in the management of Parkinson’s disease because R: dopamine is the transmitter in elements of the nigrostriatal system damaged in Parkinson’s disease

Answer 35

S is false and R is true
Like other catecholamines, dopamine does not cross the blood-brain barrier. However, the dopamine precursor, L-dopa, does, where it is metabolised to dopamine in cases of Parkinson’s disease (S false). It is known that dopamine is one of the key transmitters released from the relevant negrostriatal pathways for co-ordinated extrapyramidal function (R true).

Question 36

27979 – S: Parasympathetic innervation is probably most important for salivary secretion because R: atropine abolishes normal reflex salivary secretion.

Answer 36

S is true, R is true and a valid explanation of S
Salivary secretion, amounting to around 1500 ml of saliva per day, is under neural control. Parasympathetic innervation stimulation causes profuse secretion of watery saliva with a low content of organic material associated with vasodilatation due to the local release of VIP which co-transmits with acetyl choline. Atropine and other cholinergic blocking agents reduce salivary secretion, blocking the normal reflex secretion of saliva (thus both S & R are correct and R validly explains S). Sympathetic nerve stimulation of the salivary glands causes vasoconstriction; and secretion of small amounts of saliva with a high organic content.

Question 37

25861 – The following are true of acute confusional states
1: treatment should not commence until a cause for the confusion has been found
2: they may form part of the systemic inflammatory response syndrome
3: the side-effects of drugs used to treat confusion are minor
4: reasoning with the patient is of considerable benefit
5: sedative drugs should form the first line of treatment

Answer 37

FTFFF
Answer to come.

Question 38

21908 – Below a hemisection of the spinal cord
1: paralysis is ipsilateral
2: loss of proprioception and vibration sense is ipsilateral
3: analgesia is contralateral
4: thermal anaesthesia is ipsilateral

Answer 38

TTTF
- ipsilateral loss of proprioception, touch, and vibration sense below the lesion due to damage to the ascending dorsal columns
- ipsilateral upper motor neurone spastic paralysis below the lesion due to damage to the descending lateral corticospinal tracts
- contralateral loss of pain and temperature sensation 2 to 3 levels below the level of the lesion due to damage to the ascending lateral spinothalamic tract which cross 2 to 3 levels above the level of their respective dorsal root
- ipsilateral loss of motor and sensory function just at the level of the injured segments due to direct damage to ventral and dorsal grey matter

Question 39

9745 – Likely sequelae within the first week of complete transection of the
lower cervical spinal cord include
1: bradycardia
2: a negative nitrogen balance
3: hypothermia
4: flexor spasms of the leg

Answer 39

TTTF
Ganong, 19th ed, Ch 12

Question 40

13655, 21723 – Spinal shock following transection of the cord in man
1: profoundly depresses spinal tendon reflexes
2: renders the patient poikilothermic
3: usually lasts longer than 1-2 weeks
4: is associated with the disappearance of arterial baroreceptor responses

Answer 40

TTTT
Ganong 13th Ed. Ch. 12 P. 171 Guyton 7th Ed. Chapter: 51 Page: 617, 618.
Immediately following cord transection the resting membrane potential of distal nerves is up 6mV greater than the normal,
resulting in depression of spinal reflex responses (A true). The depression lasts at least one week, and usually beyond two weeks, at which time distal neuronal excitability slowly returns (C true). The lack of functioning autonomic efferent pathways regulating skin blood flow blunts thermoregulation and the patient’s body temperature tends to follow ambient temperature swings (B true). While resting blood pressure may be almost normal. Because autonomic function is, lost, compensation for evoked changes in arterial presssure through the arterial baroreceptor reflexes is not evident (D true).

Question 41

15290 – S: Reflex evacuation of the rectum rarely occurs following chronic transection of the spinal cord because R: the sympathetic division of the autonomic nervous supply to the internal anal sphincter is excitatory

Answer 41

S is false and R is true
Refer to Ganong, 19th Ed, Ch 12, page 201
R - sympathetic excitatory to internal anal sphincter - causing it to constrict aka not pooping