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Physiology > Nerves and Muscles ( 5% ) > Flashcards

Nerves and Muscles ( 5% ) Flashcards

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
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)
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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.
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
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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.
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.
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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
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.

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5
Q

Inhibitory neurotransmitters increase the post synaptic conductance to

  • Na
  • Cl
  • Mg
  • Na and Mg
  • All of the above
A

Chloride

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6
Q

All of the following are neurotransmitters except

  • Serotonin
  • Glutamate
  • Adenosine
  • Insulin
  • Glucagons
A

Insulin

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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
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
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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
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)
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9
Q

MAO breaks down

  • Serotonin
  • Tryptophan
  • GABA
  • Glutamate
  • Glycine
A

Serotonin

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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
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
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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.
A

contraction of bladder trigone and sphincter

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

At the SA node is a consequence of the prepotential

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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.
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
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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
A

localized increase in membrane permeability to Cl

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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
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

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17
Q
  • Which of the following nerve types are most sensitive to hypoxia
  • A α
  • A β
  • A delta
  • B
  • C
A

B are most sensitive to hypoxia

Type A are most sensitive to pressure

Type C most sensitve to local anaesthetics

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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
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

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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
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

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20
Q

Which nerve fibre type is most sensitive to pressure

  • Aβ
  • Aγ
  • A delta
  • B
  • C
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

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21
Q

Which of the following are not energy sources of muscle

  • Phosphoryl creatine
  • Fatty acids
  • Glucose
  • Glycogen
  • Creatine
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

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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
A

Glycine is excitatory at postsynaptic neurons

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23
Q

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

B

A sigma

Aβ

Aγ

C

A

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

So in this list, A beta

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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
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)
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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
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)

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26
Q

Large density vesicles in the synaptic knob contain

  • ACh
  • Glycine
  • GABA
  • Glutamate
  • Neuropeptides
A

Neuropeptides

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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
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
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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.
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)
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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.
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
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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.
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
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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
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
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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.
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
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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
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
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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
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
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
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
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
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.
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
A

M gate = activation gate, H gate = inactivation

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

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
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.
39
Q

excitatory amino acids in the brain are

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

Glutamate and glycine

40
Q

The opioid delta receptor is involved in

  • Analgesia
  • Respiratory depression
  • Miosis
  • Dependence
  • All of the above
A

Analgesia

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

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.
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.
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
A

Calcium is released from troponin

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
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
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.
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
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.
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.
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
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
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
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
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
A

The I zone decreases

49
Q

calmodulin is involved in

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

smooth muscle contraction

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
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

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
A

c) C fibres are most susceptible to local anaesthetics

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
A

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

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
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)

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
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

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
A

d) measured by injecting Evans blue

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

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
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)

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
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

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
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)

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
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

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
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

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
A

b) not having striated appearance

62
Q

13 Which of the following is absent in smooth muscle?

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

d) troponin

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
A

b) nodes of Ranvier

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
A

a) groupB

65
Q

16 Which of the following is most susceptible to pressure?

  • a) groupA–motor
  • b) groupC
  • c) group B
  • d) preganglionic-autonomic
  • e) muscle spindle fibres
A

a) groupA–motor

66
Q

17 Regarding nerve action potential, which is TRUE?

  • a) normal resting membrane potential is -40mV
  • b) initial rapid depolarisation is due to rapid influx of Ca2+ via fast channels
  • c) during depolarisation, Na+ permeality is greater than K+ permeality
  • d) hyperpolarisation is due to continuous opening of Na+ channels
  • e) plateau is formed by slow Ca2+ channels
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.

67
Q

18 Which is FALSE regarding secondary active transport?

  • a) it always transports substances in one direction
  • b) energy required is obtained by Na+/K+ ATPase pump
  • c) a good example is Na+ / glucose co-transport
  • d) Na+ / Ca2+ antiport is an example of secondary active transport
  • e) secondary active transport occurs in renal tubules
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

68
Q

19 Which is TRUE?

  • a) steroids act via cAMP
  • b) insulin acts via IP3
  • c) EGF + erythropoietin act via cAMP
  • d) thyroid hormones act via G proteins
  • e) retinoic acid act via intracellular receptor → transcription of genes
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

69
Q

20 Na+ / K+ ATPase pump – which is FALSE?

  • a) it is electrogenic in nature
  • b) it is important in maintaining cell volume
  • c) plays a major role in secondary active transport
  • d) it is the main factor which determine the resting membrane potential
  • e) it is an example of primary active transport
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)

70
Q

21 Regarding serotonin:

  • a) the highest concentration is in the brain
  • b) formed by hydroxylation and decarboxylation of tyrosine
  • c) catabolised by COMT
  • d) some receptors are ion channels
  • e) mediates smooth muscle relaxation
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.

71
Q

22 GABA:

  • a) decreases Cl- conductance
  • b) is broken down by glutamate decarboxylase (GA????)
  • c) there are five receptor subtypes
  • d) benzodiazepines bind to the β subunit of the GABA receptor
  • e) is involved in 20% of CNS synapses
A

e) is involved in 20% of CNS synapses

72
Q

23 Which is NOT present in high concentrations, at the active zone of synapses?

  • a) syntaxin
  • b) catecholamine vesicles
  • c) neuropeptide vesicles
  • d) synaptobrevin
  • e) calcium channels
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.

73
Q

24 Which is not a ligand-gated ion channel?

  • a) nicotinic receptor
  • b) GABAA receptor
  • c) glycine receptor
  • d) NMDA receptor
  • e) 5-HT1 receptor
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
74
Q

25 Which drug is NOT involved in facilitating Cl- conductance?

  • a) benzodiazepines
  • b) progesterone
  • c) oestrogen
  • d) barbiturates
  • e) alcohol
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.

75
Q

26 Regarding skeletal muscle:

  • a) isotonic contraction does no work
  • b) calcium is released from troponin during contraction
  • c) the resting membrane potential is -70mV
  • d) treppe occurs in skeletal muscle only
  • e) white muscle has short twitch durations
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.
76
Q

27 Regarding cardiac muscle:

  • a) gap junctions provide high resistance bridges
  • b) T system of tubules located at A-I junctions
  • c) calcium binds to calmodulin
  • d) tetany is not possible due to the latch bridge mechanism
  • e) ↑cAMP leads to ↑ force of contraction
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
77
Q

28 Regarding smooth muscle:

  • a) tropomyosin is absent
  • b) the resting membrane potential is -90mV
  • c) there is a highly developed sarcoplasmic reticulum
  • d) there are no spike potentials
  • e) dense bodies are attached to the cell membrane
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
78
Q

29 Regarding synapses:

  • a) large vesicles contain ACh
  • 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
  • e) neurotransmitters migrate down the axon by fast axoplasmic transport
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
79
Q

30 Regarding acetylcholine:

  • a) it is oxidised to choline and acetate by acetylcholinesterase
  • b) nicotinic receptors are blocked by atropine
  • c) it is the main excitatory transmitter in the spinal cord
  • d) it is secreted by the adrenal medulla
  • e) tetanus blocks its release at the NMJ
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
80
Q

31 Regarding synaptic structure / function:

  • a) small clear vesicles in the presynaptic tunnel contain catecholamines
  • b) tetanus toxin causes spastic paralysis by blocking release of ACh at NMJ
  • c) chemical mediators located in ???? of presynaptic fibres contain one-way conduction of impulses
  • d) the EPSP is an all-or-none response
  • e) An IPSP can be produced by localised increase in membrane permeability to Cl-
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)

81
Q

32 Transmitters – all are true EXCEPT:

  • a) angiotensin II is a neurotransmitter of the polypeptidillars
  • b) glutamate is an inhibitory amino acid
  • c) glucagons is found in hypothalamus and retina
  • d) vasopressin is found in posterior pituitary, medulla, spinal cord
  • e) serotonin is an amine
  • f) NO and CO may be transmitters – CNS
A

b) glutamate is an inhibitory amino acid

82
Q

33 Neurotransmitters:

  • a) atropine blocks effect of acetylcholine at nicotinic receptors
  • b) reaction between active acetate and choline is catalysed by acetylcholinesterase
  • c) nicotinic cholinergic receptors are serpentine receptors
  • d) the rate limiting step in synthesis of noradrenaline is conversion of tyrosine to dopa
  • e) MAOA is found in nerve endings and platelets
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*
83
Q
A

Physiology (9 decks)

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