Nerves and Muscles ( 5% ) Flashcards

Question 1

Q

With regard to the action potential in a neuron with an RMP of -70mV

The firing level is likely to be -30mV.
The overshoot will not extend much past 0mV.
The absolute refractory period occupies only 10% repolarisation.
Cl- influx will restore the membrane potential
Increase of the external [chloride] increases the resting membrane potential

Answer

A

Cl- influx will restore the membrane potential

The firing level is likely to be -55mV
The overshoot may reach +30mV
The absolute refractory period occupies about 40% repolarisation
Increase of the external [chloride] decreases the resting membrane potential (opposite of potassium)

Question 2

Q

In skeletal muscle

Tropomyosin is made up of 3 subunits.
The heads of actin contain ATP hydrolysis sites.
The myosin is contained entirely within the A band
Troponin T inhibits the interaction with myosin.
The immediate energy source for contracting is GTP.

Answer

A

The myosin is contained entirely within the A band

Troponin is made up of 3 subunits.
The heads of myosin contain ATP hydrolysis sites.
Troponin I inhibits the interaction with myosin.
The immediate energy source for contracting is ATP

Question 3

Q

In the action potential of cardiac muscle fibre

The resting membrane is -50mV.
Phase I is due in part to the rapid chloride influx.
Sodium channels are progressively inactivated during phase 1.
The repolarisation time increases as the heart rate increases.
Is usually 20ms duration.

Answer

A

Sodium channels are progressively inactivated during phase 1

Phase 0= rapid depol (open Na channels)

Phase 1 = rapid repol (close Na channels, open K channels)

Phase 2 = prolonged plateau (opening of Ca channels)

The resting membrane is -90mV
Phase I is due in part to the rapid sodium influx. (sodium influx depolarises the cell, which opens voltage-gated Ca channels in the T-membrane (DHPRs). The resulting Ca influx causes the SR to release calcium via RyRs)
The repolarisation time decreases as the heart rate increases (as re-stimulation may occur during the RRP)
Is usually 200ms duration.

Question 4

Q

The special feature of the contraction of smooth muscle is

Actin is not involved
Myosin is not involved
Calcium is not involved
ATP is not the energy source
The membrane potential is unstable

Answer

A

The membrane potential is unstable

and hence has a resting ‘tone’

It contains actin and myosin, but no troponin

and utilises calmodulin-dependent myosin light-chain kinase and myosin light chain phosphatase for contraction and relaxation.

Question 5

Q

Inhibitory neurotransmitters increase the post synaptic conductance to

Na
Cl
Mg
Na and Mg
All of the above

Question 6

Q

All of the following are neurotransmitters except

Serotonin
Glutamate
Adenosine
Insulin
Glucagons

Question 7

Q

True acetylcholinesterase

Forms acetylcholine from acetate
Is produced in the liver
Functions only at nerve endings.
Is involved in GABA metabolism
None of the above

Answer

A

Functions only at nerve endings.

As opposed to pseudo- or non-specific cholinesterases which function in plasma (ie metabolise suxamethonium and esmolol)

Metabolises ACh into acetate and choline
Is produced in the in the muscle of the NMJ

Question 8

Q

In the formation of adrenaline

COMT produces adrenaline from noradrenaline.
Phenylalanine is converted to tyrosine.
DOPA is formed by DOPA decarboxylase.
DA is 2 NA molecules side by side
Serotonin formation is a vital intermediate step

Answer

A

Phenylalanine is converted to tyrosine. (But most tyrosine comes direct from dietary sources)

COMTdegrades adrenaline
DOPA is metabolised by DOPA decarboxylase. (Tyrosine -> DOPA via tyrosine hydroxylase, then DOPA -> dopamine via DOPA carboxylase)

Question 9

Q

MAO breaks down

Serotonin
Tryptophan
GABA
Glutamate
Glycine

Answer

A

Serotonin

Question 10

Q

Sensation for cold

Is relayed via the thalamus
Is transmitted by the dorsal columns
Is an uncrossed sensory modality
Is mediated by substance P fluxes
Is mediated by A α fibres

Answer

A

Is relayed via the thalamus

Is transmitted by the dorsal columns (wrong - need to confirm answer)
Is an uncrossed sensory modality (wrong - need to confirm answer)
Is mediated by A gamma fibres

Question 11

Q

α1 stimulation will lead to

contraction of bladder trigone and sphincter
bronchial smooth muscle relaxation.
pupillary constriction.
increased AV conduction.
skeletal muscle vasodilation.

Answer

A

contraction of bladder trigone and sphincter

bronchial smooth muscle relaxation (B2)
pupillary constriction.
increased AV conduction. (B1)
skeletal muscle vasodilation. (B1)

Question 12

Q

cardiac muscle usually contracts more forcefully when

cell membrane Na/K ATPase activity is stimulated (eg digoxin)
ligand gated Ca channels are open for longer periods
it is titanic (individual responses fused before relaxation can occur)
the average sarcomeres length increases
adrenaline activates β1 receptors

Answer

A

adrenaline activates β1 receptors

cell membrane Na/K ATPase activity is inhibited (eg digoxin)
Voltage-gated Ca channels are open for longer periods
it is titanic (individual responses fused before relaxation can occur)
the average sarcomeres length increases (?? sounds right but clearly wrong)

Question 13

Q

Rhythmicity

Is a consequence of the plateau (phase 2; Ca influx) of depolarization at the SA node.
Is a major feature where myocardial muscle differs from skeletal and smooth muscle
At the SA node is a consequence of the prepotential
At the AV node is a consequence of Na leak into the cell during diastole
Is accelerated in the AV node by neuro-hormonal effects on K channels

Answer

A

At the SA node is a consequence of the prepotential

Question 14

Q

With respect to nerve fibre types

The speed of conduction is inversely proportional to the diameter of the fibre.
C fibres are more susceptible to the effects of local anaesthetics than A fibres
A γ fibres are concerned primarily with somatic motor function.
Pain may be relayed by all fibre types.
A α fibres are efferent only.

Answer

A

C fibres are more susceptible to the effects of local anaesthetics than A fibres

The speed of conduction is proportional to the diameter of the fibre. (Wider fibres conduct faster)
A γ fibres are concerned primarily with motor to muscle spindles
Pain may be relayed by C and A delta fibres
A α fibres are Proprioception and somatic motor

Question 15

Q

inhibitory post synaptic potentials involve

localized increase in membrane permeability to Na
localized decrease in membrane permeability to Cl
localized increase in membrane permeability to PO4
localized increase in membrane permeability to Cl
localized decrease in membrane permeability to K

Answer

A

localized increase in membrane permeability to Cl

Question 16

Q

Which is false

Ca ions bind troponin T.
Troponin-I/tropomyosin complexes constitute relaxing protein
Each attachment/detachment cycle shortens muscle length by approximately 1%
ATP is an immediate source of energy
The head of myosin II possesses an actin binding site

Answer

A

a)

Ca ions bind to Troponin C

Troponin I covers the myosin-binding site on actin

Troponin T binds to tropomyosin and helps hold the troponin complex in place.

Troponin is NOT found in smooth muscle

Question 17

Q

Which of the following nerve types are most sensitive to hypoxia
A α
A β
A delta
B
C

Answer

A

B are most sensitive to hypoxia

Type A are most sensitive to pressure

Type C most sensitve to local anaesthetics

Question 18

Q

Which is false regarding smooth muscle contractility

Increased by ACh
Decreased by activation of phospholipase C.
Increased by cold
Decreased by cAMP
Increased by stretch

Answer

A

Decreased by activation of phospholipase C

(is increased by PLC)

ACh mediates an effect through phospholipase C, which produces IP3 and allows Ca release through IP3 receptors

Adrenaline and noradrenaline cause a decrease in contractility of smooth muscle

Question 19

Q

A sarcomere

Contains 2 separate halves of an A and I band
Is the space between 2 A bands
Is the space between 2 Z lines
Has the T system at the sarcomeres junctions. Between A and I bands
Contracts when troponin bind to myosin

Answer

A

Is the space between 2 Z lines

T-system is between the A and I bands

Except in cardiac muscle is at the z-line

Question 20

Q

Which nerve fibre type is most sensitive to pressure

Aβ
Aγ
A delta
B
C

Answer

A

Aβ

Larger nerves are more sensitive to pressure

A fibres are alpha->delta in decreasing size

So alpha most susceptible, beta second, delta least.

A are all larger than B which are all larger than C

Question 21

Q

Which of the following are not energy sources of muscle

Phosphoryl creatine
Fatty acids
Glucose
Glycogen
Creatine

Answer

A

Creatine is a precurser to phosphorylcreatine (as ADP is to ATP)

Phosphorylcreatine is an energy store in muscle.

It is hydrolyzed between two myosin heads to form ATP from ADP and thus allows contraction to continue

At rest, some ATP transfers its phosphate to creatine, to build up a store of phosphorylcreatine.

FFAs are used at rest and light exercise (slower process)

In heavier exercise glucose is used, or glycogen

Question 22

Q

Regarding neurotransmitters, which is false

Glutamate is excitatory
GABA is inhibitory at presynaptic sites
Glycine is excitatory at postsynaptic neurons
Gamma hydroxybuterate is inhibitory
Aspartate is excitatory

Answer

A

Glycine is excitatory at postsynaptic neurons

Question 23

Q

Which of the following nerve fibre types has the fastest conduction.

B

A sigma

Aβ

Aγ

C

Answer

A

A alpha is the fastest, moving down to C fibres which are the slowest conductors

So in this list, A beta

Question 24

Q

A decrease in extracellular K

Makes the resting membrane potential more negative in the nerve cell
Has a similar effect in nerve cells as a decrease in extracellular Na
Has little effect on nerve cell membrane potentials
May decrease nerve cell action potential amplitude
Has a similar effect in nerve cells as an increase in extracellular Ca

Answer

A

Has a similar effect in nerve cells as an increase in extracellular Ca

Makes the resting membrane potential more negative in the nerve cell

(also seems to be correct - Hyperkalaemia moves the RMP closer to the threshold potential, and thus more excitable (ie closer to -55mV). Hypokalaemia, as in this question, lowers the RMP and makes it hyperpolarised)

Has a large effect on nerve cell membrane potentials (K is the primary determinant of RMP due to its relative ease of crossing the cell membrane)
May decrease nerve cell action potential amplitude (changes in [sodium] affect the AP amplitude, changes in [K] affect the RMP)

Question 25

Q

Muscle spindles

Lie in parallel with extrafusal muscle fibres
Are the only effector organs in the monosynaptic stretch reflex
Do not have a motor supply of their own
Consist of up to 100 muscle fibres
Can be divided into 5 types in mammalian muscle

Answer

A

Lie in parallel with extrafusal muscle fibres

Consist of 5-14 muscle fibres

Have afferent and efferent innervation (ie contain a motor supply)

Are 2-3 types (static, dynamic, nuclear chain)

Question 26

Q

Large density vesicles in the synaptic knob contain

ACh
Glycine
GABA
Glutamate
Neuropeptides

Answer

A

Neuropeptides

Question 27

Q

Nerve fibres

Have decreased conduction speeds with increasing diameters.
Type Aα are the smallest.
Type Aα conduct modalities of pain and temperature.
Have an increased refractory period with increasing diameter.
type C are unmyelinated

Answer

A

type C are unmyelinated

A+B are myelinated

Have increased conduction speeds with increasing diameters.
Type Aα are the biggest
Type Aα conduct LMNs and proprioception

Question 28

Q

Regarding the resting membrane potential

The inside of the cell is positive relative to the outside.
The Na/K ATPase is electrogenic because it moves 2 Na and 3K across the membrane.
The membrane is more permeable to K than to Na
In nerve cells is about -120mV.
K moves out of the cell down its electrical gradient.

Answer

A

The membrane is more permeable to K than to Na

The inside of the cell is negative relative to the outside.
The Na/K ATPase is electrogenic because it moves 3 Na out and 2K in across the membrane.
In nerve cells is about -70mV
K moves out of the cell down its chemical gradient, but against its electrical gradient (as the outside is more positive, like K)

Question 29

Q

Skeletal muscle

Function as a syncytium and contracts rhythmically in the presence of a pacemaker.
Contractile proteins include myosin II and tropomyosin.
Has a light I band, divided by a dark A band
Has 3 troponin units, I, T and M.
Myosin II is make up of 4 heavy chains and 2 light chains.

Answer

A

Has a light I band, divided by a dark A band

A - band is length of myosin unit

I band is actin that doesnt cross myosin

H-band is myosin without actin

Function as a syncytium and contracts rhythmically in the presence of a pacemaker. (Not a syncytium – cardiac and smooth muscle do though)
Contractile proteins include myosin II and actin. Tropomyosin is regulatory, not contractile.
Has 3 troponin units, I, T and C.
Myosin II is make up of 2 heavy chains and 2 light chains

Question 30

Q

Regarding the neuromuscular junction

The myelin sheath thickens at the terminal portion of the axon.
ACh vesicles are evenly distributed thoughout the endplate.
The impulse alters permeability to Ca and Na.
Myasthenia Gravis is a result of antibodies affecting Ca channels.
Each impulse releases about 60 ACh vesicles.

Answer

A

Each impulse releases about 60 ACh vesicles.

The myelin sheath thins at the terminal portion of the axon.
ACh vesicles are evenly distributed thoughout the endplate. (Endplate is the muscle end of the synapse so does not release ACh - ?does release AChE though)
The impulse alters permeability to Na and K
Myasthenia Gravis is a result of antibodies affecting Nicotinic receptors

Question 31

Q

A β nerve fibres

Conduct touch and pressure impulses
Are unmyelinated
Have the largest diameter of all nerves
Have a slow conduction velocity
Conduct preganglionic impulses

Answer

A

A beta conduct touch and pressure impulses

alpha conduct LMNs and proprioception

gamma - motor to muscle spindles

delta - pain, cold, touch

Are myelinated (C are unmyelinated)
Have the second largest diameter of all nerves (A alpha are larger)
Have a fast conduction velocity
B fibres conduct preganglionic impulses

Question 32

Q

when skeletal muscle contracts

calcium is released and this initiates contraction by binding troponin T.
there is always a decrease in the length of the muscle.
it does so at a mechanical efficiency of 80%.
if it is an isotonic contraction, work is done.
the initiating event is ACh binding to a G protein linked receptor.

Answer

A

if it is an isotonic contraction, work is done, because a force has been moved a certain distance.

Isometric does not move therefore no work is done

calcium is released and this initiates contraction by binding troponin C
there is not always a decrease in the length of the muscle, such as in Isometric contraction. Isotonic is shortening.
it does so at a mechanical efficiency of 0 to 50%
the initiating event is ACh binding to an ion channel

Question 33

Q

Smooth muscle contractions

Are dependent on an intact nerve supply.
Are a result of Ca influx into the sarcoplasmic reticulum.
Are smooth, discrete and fine in multi-unit smooth muscle
Are dependent on troponin.
Are exaggerated in vitro when bathed in ACh. Also true? Increase the number of contractions

Answer

A

Are smooth, discrete and fine in multi-unit smooth muscle

(I assume ‘graded and fine’ correlates with smooth and discrete)

Are exaggerated in vitro when bathed in ACh.

(Also true? Increase the number of contractions)

Are not dependent on an intact nerve supply. Contractions such as myogenic stretch or relaxation cos of NO released by endo in response to shear stress
Are a result of Ca influx out of the sarcoplasmic reticulum and other sources
Are dependent on myosin light chain kinase and phosphatase

Question 34

Q

Regarding synaptic transmission

Opening of Na channels excites the postsynaptic neuron
Voltage gated Na channels on the presynaptic neuron determine the quantity of neurotransmitter released
Neuropeptides are responsible for acute responses of the nervous system
Small molecule type transmitters do not stimulate the receptor activated enzymes
Cholinesterase is responsible for synthesis of Ach

Answer

A

Opening of Na channels excites the postsynaptic neuron

Each impulse releases about 60 Ach vesicles
Neurotransmitters are responsible for acute responses of the nervous system
Cholinesterase is responsible for metabolism of Ach

Question 35

Q

With respect to action potentials generated in nerves

Conduction from synaptic junctions to the termination of the axon is called salutatory conduction.
Relative refractory period is defined as the period from the end of the absolute refractory period to the start of after-hyperpolarisation.
Decrease in the external environment of Na decreases the size of the action potential.
Decrease in the external Ca level decreases the duration of the action potential.
Opening the ligand gated Na channels is responsible for the commencement of the spike potential

Answer

A

Decrease in the external environment of Na decreases the size of the action potential. Na affects the size of the AP

salutatory conduction is the process of AP propagation in myelinated cells from one Node of Ranvier to another
Relative refractory period is defined as the period when the cell can be depolarised by a greater-than-usual stimulus
Decrease in the external Ca level alters the excitability of a cell, but does not change the magnitude of the AP

Question 36

Q

With respect to troponin

Troponin C inhibits the interaction of actin and myosin.
Troponin T contains the binding sites for calcium.
Troponin I binds troponin components to tropomyosin.
Head of troponin I catalyses ATP to allow myosin to move on actin molecules.
None of the above

Answer

A

None of the above

Troponin I inhibits the interaction of actin and myosin.
Troponin C contains the binding sites for calcium.
Troponin T binds troponin components to tropomyosin.
Head of myosin II catalyses ATP to allow myosin to move on actin molecules.

Question 37

Q

The Ca/Na channel.

In the resting, fully polarized state the m gate is open and the h gate is open
In the resting, fully polarized state the m gate is open and the h gate is closed
In the activated state the m gate is open and the h gate is closed
In the inactivated state the m gate is open and the h gate is closed
In the inactivated state the m gate is closed and the h gate is open

Answer

A

M gate = activation gate, H gate = inactivation

In the inactivated state the m gate is open and the h gate is closed

Question 38

Q

With respect to synapse

Inhibitory postsynaptic potentials are due to localized increase in membrane permeability to Na
GABA is one of the neurotransmitters involved in presynaptic inhibition in the CNS
Metabolism of catecholamines at the synaptic cleft is the major method of terminating their action.
Adrenaline is the major neurotransmitter at postganglionic sympathetic endings.
Habituation is due to a gradual inactivation of Na channels on repeat stimulation

Answer

A

GABA is one of the neurotransmitters involved in presynaptic inhibition in the CNS

Inhibitory postsynaptic potentials are due to localized increase in membrane permeability to Cl or K
Metabolism of catecholamines at the synaptic cleft is the major method of terminating their action. (Mitochondria (ie within the cell, not the synapse))
Noradrenaline is the major neurotransmitter at postganglionic sympathetic endings.
Desensitisation is due to a gradual inactivation of Na channels on repeat stimulation.

Question 39

Q

excitatory amino acids in the brain are

glutamate and GABA
GABA and glycine
Glutamate and glycine.
Glycine and aspartate
Glutamate and glycine

Answer

A

Glutamate and glycine

Question 40

Q

The opioid delta receptor is involved in

Analgesia
Respiratory depression
Miosis
Dependence
All of the above

Answer

A

Analgesia

This is the answer given, but elsewhere stated that only the mu receptor is implicated in analgesia

Question 41

Q

In visceral smooth muscle

Ca for contraction is released from sarcoplasmic reticulum.
Membrane potential has a resting value of -90mV.
The excitation contraction coupling time is rapid ,10ms.
Muscle contracts when stretched in the absence of innervation
Binding of ACh to nicotinic receptors increases calcium influx.

Answer

A

Muscle contracts when stretched in the absence of innervation

Ca for contraction is released from sarcoplasmic reticulum, but primarily comes from other sources such as the plasma membrane
Membrane potential has a fluctuating resting value
The excitation contraction coupling time is slower than skeletal and cardiac muscle, as slow as 500ms
Binding of ACh to nicotinic receptors increases sodium influx.

Question 42

Q

In skeletal muscle relaxation

There is a spread of depolarization along T tubules
Calcium is released from troponin
There is increased Na/K conduction in the end plate membranes
A resting membrane potential of -65mV is finally reached
Mg has a crucial role

Answer

A

Calcium is released from troponin

Question 43

Q

Regarding synapses

The synaptic cleft is 30-50mm wide.
Transmitters are released from synaptic knobs secondary to Na trigger.
Amount of transmitter released is proportional to Ca efflux.
ACh is present in granulated vesicles in synaptic knob
The EPSP is caused by Na influx

Answer

A

The EPSP is caused by Na influx

IPSP by Cl influx

Transmitters are released from synaptic knobs secondary to Ca trigger.
Amount of transmitter released is not proportional to Ca efflux (about 60 vesicles each time), but is calcium dependent.
ACh is present in small clear vesicles in synaptic knob

Question 44

Q

The action potential of a neuron

Is initiated by efflux of Na.
Is terminated by efflux of Na.
Declines in amplitude as it moves along the axon.
Results in transient reversal of the concentration gradient of Na across the cell.
Is not associated with any net movement of Na or K across the cell membrane.

Answer

A

Is not associated with any net movement of Na or K across the cell membrane.

Cannot find this exact point in Ganongs, but the others are all definitely wrong, and I can see how ‘net’ movement could be a technicality or something.

Is initiated by influx of Na.
Is terminated by efflux of K+
Amplitude and velocity are constant as it moves along the axon
Results in transient reversal of the electrical gradient of Na across the cell.
- Concentration gradient is very large - is not overcome

Question 45

Q

The functions of tropomyosin in skeletal muscle include

Releasing Ca after an action potential.
Sliding on actin during contraction.
Binding to myosin during contraction
Acting as a relaxing protein at rest by covering up the sites where myosin binds to
Generating ATP which passes to the contractile mechanism.

Answer

A

Acting as a relaxing protein at rest by covering up the sites where myosin binds to

Troponin releases Ca after an action potential.
Myosin slides on actin during contraction.
ATP binds to myosin during contraction.
Mitochondria generates ATP which passes to the contractile mechanism.

Question 46

Q

with regard to contraction and relaxation of skeletal muscle, which is false

contraction involves the release of K from the terminal cisterns
relaxation involves the release of Ca from troponin.
prior to contraction, increased Na and K conduction occurs in the end plate
relaxation involves the cessation of the interaction between actin and myosin
contraction involves inward spread of depolarization along T tubule

Answer

A

contraction involves the release of Ca2+ from the terminal cisterns

relaxation involves the release of Ca from troponin.
prior to contraction, increased Na and K conduction occurs in the end plate
relaxation involves the cessation of the interaction between actin and myosin
contraction involves inward spread of depolarization along T tubule

Question 47

Q

Regarding nerve fibres

Type C myelinated fibres in the dorsal root conduct impulses concerning pain and temperature
Type A α unmyelinated fibres conduct impulses concerning proprioception
Type A β unmyelinated fibres conduct impulses concerning light touch
Type A γ unmyelinated fibres conduct impulses to the muscle spindles
Type B myelinated fibres are located in the preganglionic autonomic region

Answer

A

Type B myelinated fibres are located in the preganglionic autonomic region

Type C unmyelinated fibres in the dorsal root conduct impulses concerning pain and temperature
Type A α myelinated fibres conduct impulses concerning proprioception
Type A β myelinated fibres conduct impulses concerning light touch
Type A γ myelinated fibres conduct impulses to the muscle spindles

Question 48

Q

In contracting skeletal muscle

The H zone increases
The I zone decreases
The A zone decreases
The A and I zone increase
None of the above

Answer

A

The I zone decreases

Question 49

Q

calmodulin is involved in

smooth muscle contraction
smooth muscle relaxation
myocardial contractility
acts to curtail contraction
acts to limit relaxation

Answer

A

smooth muscle contraction

Question 50

Q

1 With reference to the action potential:

a) decreasing the external Na+ concentration increases the size of the action potential
b) decreasing the external K+ concentration decreases the resting membrane potential
c) increasing the external Na+ concentration decreases the resting membrane potential
d) decreasing the external K+ concentration has little effect on the resting membrane potential
e) none of the above are true

Answer

A

e) none of the above are true

Sodium is involved in the size of the AP - increase external Na will increase the AP magnitude

Potassium is involved in the RMP - increased external K will raise the RMP closer to the threshold potential and make the tissue more excitable

Question 51

Q

2 In the Erlanger and Gasser classification of nerve fibres:

a) C fibres have the fastest conduction velocity
b) Aγ fibres are responsible for touch and pressure
c) C fibres are most susceptible to local anaesthetics
d) Aα fibres have the fastest conduction velocity and the longest absolute refractory period
e) A fibres are most susceptible to hypoxia

Answer

A

c) C fibres are most susceptible to local anaesthetics

Question 52

Q

3 Regarding neurotrophins:

a) NGF and BDNF share the same receptor
b) the structure of the β subunit of NGF resembles that of insulin
c) CNTF is necessary for the growth and maintenance of sympathetic neurons
d) disruption of GDNF by gene knockout causes a marked loss of cutaneous mechanoreceptors
e) none of the above are true

Answer

A

b) the structure of the β subunit of NGF resembles that of insulin

Question 53

Q

4 Regarding cardiac muscle:

a) cardiac muscle has high ATPase activity
b) only the α MHC isoform is found in the atria
c) resting membrane potential is about -70mV
d) force of contraction is mediated by catecholamines acting via β -adrenergic receptors
e) mutations of the human ether-a-go-go gene causes minks to shake their legs uncontrollably

Answer

A

d) force of contraction is mediated by catecholamines acting via β -adrenergic receptors

RMP is about -80mV

Low ATPase activity, so reliant on a good O2 supply to maintain oxidative metablism

Contains both alpha and beta isoforms of Myosin Heavy Chains, alpha predominate in the atria, beta in the ventricles (alpha has a higher ATPase activity than beta)

Question 54

Q

5) Which of the following does not decrease smooth muscle membrane potential?

a) acetylcholine
b) stretch
c) cold
d) noradrenaline
e) parasympathetic stimulation

Answer

A

d) noradrenaline

ACh, cold, stretch, and parasympathetic stimulation all increase the RMP towards the threshold (ie more excitable)

Adrenaline and sympathetic stimulation make it less excitable

Question is worded funny but norad is the odd one out

Question 55

Q

6) In regard to plasma volume:

a) it contributes to 10% of body weight
b) can easily be measured by radio isotope chromium
c) if the plasma volume is known, the blood volume can be calculated by multiplying 100-HCT/100
d) measured by injecting Evans blue
e) the average plasma volume is 500ml

Answer

A

d) measured by injecting Evans blue

Contributes 5% of body weight, average volume 3.5L (blood volume 5L)

Question 56

Q

Which of the following is FALSE?

a) the ECF represents 20% of body weight
b) the blood volume represents 8% of the body weight
c) the 2/3 of the body water is in ICF
d) 18% of the body weight is protein
e) the transcellular fluids contribute to 5% of the body weight

Answer

A

e) the transcellular fluids contribute to 5% of the body weight

(actually contributes 15%, and plasma 5%, to make up the 20% of ECF)

Question 57

Q

Which of the following is FALSE?

a) diffusion depends on concentration gradient of the solutes
b) osmotic pressure of a solution is inversely related to the volume of the solution
c) when 5% dextrose is infused, it becomes hypotonic to the plasma in the body
d) osmolality is defined as osmotically active particles in 1L of solution
e) osmolality is defined as a number of osmotically active particles in 1kg of solvent

Answer

A

d) osmolality is defined as osmotically active particles in 1L of solution

Osmolality is particles in 1 kg of solvent.

OsmolaRity = LitRes of solution

Question 58

Q

Regarding cell membrane, which of the following is FALSE?

a) the diameter of the cell membrane is about 7.5nm
b) 50% of the cell membrane is made up of proteins
c) the main lipids of the cell membrane are phospholipids
d) the hydrophilic ends of the lipid molecules are faced towards the interior of the cell membrane
e) the proteins in the cell membrane function as carriers, ion channels, enzymes and receptors

Answer

A

d) the hydrophilic ends of the lipid molecules are faced towards the interior of the cell membrane

(hydrophilic face outside where the water is, hydrophobic chill together on the inside, protected from nasty H20)

Question 59

Q

10 Regarding mitochondria, which of the following is TRUE?

a) 99% of mitochondrial proteins are products of mitochondrial DNA
b) the outer membrane of the mitochondria is folded to form cristae
c) the space between the outer and inner mitochondrial space is called matrix space
d) it is the sperm which contributes to the formation of mitochondria in the zygote
e) the synthesis of ATP in the mitochondria is triggered by diffusion of H+ from matrix to intracristal space

Answer

A

e) the synthesis of ATP in the mitochondria is triggered by diffusion of H+ from matrix to intracristal space

Cristae are in the inner membrane

The matrix is inside the cristae (the cytoplasm, if you will)

The intermembrane space is between the outer and inner membranes

The egg provides the juice to form mitochondria, not the sperm

Question 60

Q

Which is FALSE?

a) fast fibres have small number of mitochondria
b) fast fibres are called white muscles
c) the glycolic processes are more important in energy supply in fast fibres
d) slow fibres are also called red fibres
e) fast fibres have more extensive blood supply than slow fibres

Answer

A

e) fast fibres have more extensive blood supply than slow fibres

Less blood supply because they do not utilise as much oxidative metabolism so need less oxygen, and have fewer mitochondria

White = fast (ironically)

Red = slow

Question 61

Q

12 Smooth muscles differ from skeletal muscle by:

a) not having actin/myosin
b) not having striated appearance
c) not using ATP for contraction
d) not using Ca2+ for contraction
e) not having sarcoplasmic reticulum

Answer

A

b) not having striated appearance

Question 62

Q

13 Which of the following is absent in smooth muscle?

a) tropomysin
b) actin
c) myosin
d) troponin
e) mitochondria

Answer

A

d) troponin

Question 63

Q

14 The highest number of voltage gated Na+ channels are found in:

a) initial segment of axon
b) nodes of Ranvier
c) cell body
d) terminal buttons
e) myelinesheath

Answer

A

b) nodes of Ranvier

Question 64

Q

Which of the following nerve fibres is most susceptible to hypoxia?

a) groupB
b) groupC
c) groupA–α
d) dorsal root
e) somaticmotor

Answer

A

a) groupB

Answer 63

A

a) groupA–motor

Answer 64

A

c) during depolarisation, Na+ permeality is greater than K+ permeality

RMP ~ -70mV

Initial rapid depol is due to Na+ influx

Hyperpolarisation is due to continuous opening of K+ channels

Plateau is formed by slow Ca2+ channels - IN CARDIAC MYOCYTES, not nerves. Read the question next time.

Answer 65

A

a) it always transports substances in one direction

Secondary active transport utilises diffusive transport (anti-or-sym port) using electrochemical gradients of Na set up by active transport via Na-K-ATPase

Antiport - Na-Ca, Na-H

Symport - Na-glucose, Na-amino acid

Answer 66

A

e) retinoic acid act via intracellular receptor → transcription of genes

Steroids and thyroid hormone act at a nuclear receptor

Insulin is tyrosine kinase

IP3 is activated by cleavage of PIP2 into IP3 and DAG by Phospholipase C

In general, quick actions (Ca channel blockers, opiates, neurotransmitters etc) act directly on ligand-or-voltage gated ion channels, or GPCR (which include IP3 and cAMP).

Slower actions like insulin, EGF, EPO (hours) act via ligand-regulated membrane enzymes (eg tyrosine kinase)

Very slow actions (steroids, thyroid hormone, Vit. D) act via nuclear receptors

Answer 67

A

d) it is the main factor which determine the resting membrane potential

(that would be K+ concentration gradient as the cell is relatively permeable to K+ anyway. NaKATPase main role is moving Na out of the cell to set up the Na gradient (for secondary active transport), and stop the cell from swelling and exploding)

Answer 68

A

d) some receptors are ion channels

COMT degrades catecholamines (dopamine, adrenaline, noradrenaline)

Serotonin is produced from tryptophan

Highest concentration of serotonin is the ‘enteric nervous system in the gut’, but dont quote me on that.

Answer 69

A

e) is involved in 20% of CNS synapses

Answer 70

A

c) neuropeptide vesicles

Neuropeptides are containes in dense-core vesicles, which are found throughout a nerve cell (axon, some, dendrite), not just the pre-synaptic bulb

Neurotransmitters are contained in small vesicles at the synapse itself.

Answer 71

A

e) 5-HT1 receptor

Bit of a BS question - 5-HT is serotonin. 5-HT3 is a ligand-gated ion channel, but all others in the family are GPCRs.

a) nicotinic receptor - ACh/Na
b) GABAA receptor - GABA/Cl
c) glycine receptor - Glycine/Cl
d) NMDA receptor - glutamate/Na

Answer 72

A

c) oestrogen

Cl- is involved in slowing transmission or something, so has an inhibitory effect. Benzos, barbituates, EtOH are all depressants so are obviously involved. Hopefully the answer will come with further study out of the other two.

Answer 73

A

e) white muscle has short twitch durations

White = fast glycolytic

a) isotonic = Same Tone. So same tone, different length, so work is done.
b) calcium is released from troponin during relaxation
c) the resting membrane potential is -90mV (-70mV in nerve cells, -80mV in cardiac muscle, variable in smooth muscle)
d) treppe occurs in skeletal muscle only - the graduated series of increasingly vigorous contractions that results when a corresponding series of identical stimuli is applied to a rested muscle.

Answer 74

A

e) ↑cAMP leads to ↑ force of contraction

beta 1 (and 2) adrenergic receptors act via cAMP GPCRs (and cause an increase in intracellular Ca2+)

a) gap junctions provide low resistance bridges
b) T system of tubules located at z-lines (but A-I junctions in skeletal muscle)
c) calcium binds to troponin
d) tetany is not possible due to ?slow Ca2+ channels mean that it cannot be restimulated until RMP is -50mV

Answer 75

A

e) dense bodies are attached to the cell membrane

(in lieu of striation)

a) troponin is absent
b) the resting membrane potential is variable
c) there is a poorly developed sarcoplasmic reticulum as Ca2+ influx comes from other sources
d) there are spike potentials

Answer 76

A

e) neurotransmitters migrate down the axon by fast axoplasmic transport
* a) large vesicles contain Neuropeptides

(Need to confirm correct answers to those below)

b) Na+ influx triggers fusion / exocytosis of vesicles
c) I PSP can be produced by closing K channels
d) the synaptic cleft is 100-150nm

Answer 77

A

c) It is the main excitatory transmitter in the spinal cord

Released by all neurons that exit the CNS

a) it is hydrolysed to choline and acetate by acetylcholinesterase
b) muscarinic receptors are blocked by atropine
d) adrenaline and noradrenaline is secreted by the adrenal medulla
e) Botulinum blocks its release at the NMJ (-> flaccid paraylysis)
- Tetanus blocks GABA release -> reduced inhibiton -> spastic paralysis

Answer 78

A

e) An IPSP can be produced by localised increase in membrane permeability to Cl-

eg via opening of ligand-gated ion channels (like GABA receptors - how benzos work)

Answer 79

A

b) glutamate is an inhibitory amino acid

Answer 80

A

d) the rate limiting step in synthesis of noradrenaline is conversion of tyrosine to dopa

Atropine blocks ACh at muscarinic receptors*
AChE breaks down ACh, it doesnt metabolise it*