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94 Cards in this Set

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  • Back
does a large diameter increase or decrease conduction speed compared with small diameter axons?
increase
t/f... each receptor is capable of responding to only one form of energy
false, each receptor is capable of responding to a range of stimuli but its threshold is lowest for one form of energy
what is the name of the region within which receptors respond to stimuli?
receptive field
what is required of the receptive field to da receptor to distinguish fine features and to localise a stimulus accurately?
small receptive field
are pacinian corpuscles associated with rapidly conducting axons?
yes
name the spindle-shaped receptor that responds to stretch of skin
rufini organ
do meissner's corpuscles have a large or small receptive field?
small
which mechanoreceptor responds to pressure?
merkel-cell-neurite complex
what do pacinian corpuscles uniquely respond to?
vibration (at least 500 Hz)
which mechanoreceptor responds both when a stimulus is applied and removed?
pacinian corpuscle
which mechanoreceptor responds to vibrations less than 500 Hz?
meissner's corpuscles
t/f... merkel-cell-neurite complexes only respond when a stimulus is applied
false, respond throughout duration of stimulus
when do meissner's corpuscles respond to a stimulus?
only when it is applied
when do pacinian corpuscles respond to a stimulus?
briefly when it is applied and when it is removed
what in muscles responds to the sense of position and movement?
muscle spindle
what in tendons contributes to the sense of position and movement?
Golgi tendon organ
do muscle spindles and Golgi tendon organ conduct rapidly?
yes
t/f... thermoceptors are very sensitive to small changes in temperature
true
where are the cell bodies of bipolar nerve fibres?
dorsal root ganglion
which signals are conveyed to the thalamus and cerebral cortex?
perception and sensation
where do the fibres which contribute to unconscious reflexes synapse?
spinal cord and brainstem
is a merkel-cell neurite complex associated with an unmyelinated axon?
no, it is associated with a medium sized, myelinated axon and conducts relatively fast
what type of axons is the sense of proprioception associated with?
large, myelinated axons (rapid conduction)
where do the fibres which contribute to unconscious reflexes synapse?
spinal cord and brainstem
is a merkel-cell neurite complex associated with an unmyelinated axon?
no, it is associated with a medium sized, myelinated axon and conducts relatively fast
what type of axons is the sense of proprioception associated with?
large, myelinated axons (rapid conduction)
t/f... a muscle spindle lies perpendicular to the muscle fibres
false, it lies parallel to the muscle fibres
what are muscle spindles sensitive to?
stretch
what do thick filaments contain?
myosin
what do thin filaments contain?
actin
what produces an increase in force output from a muscle?
recruiting motor units
what are thin filaments of adjacent sarcomeres held together by?
Z disc
what component of the thick filaments interact with actin during muscle contraction?
cross-bridges (myosin projections)
what conducts the muscle action potential to to sarcoplasmic reticulum?
T-tubules
where is calcium stored in muscle?
sarcoplasmic reticulum
what initiates muscle contraction?
calcium binding to troponin
what are troponin and tropomyosin?
regulatory proteins on thin filaments which inhibit myosin-actin interaction
what occurs upon resequestration of calcium into the SR?
muscle relaxation
what are troponin and tropomyosin?
regulatory proteins on thin filaments which inhibit myosin-actin interaction
what occurs upon resequestration of calcium into the SR?
muscle relaxation
how big is a sarcomere?
2-3 microns
how is intracellular calcium level maintained in the resting muscle?
active pumping by the CaATPase pump of calcium from cytosol to SR
how is calcium stored in the SR?
by binding to calsequestrin
t/f... calsequestrin has a low capacity but a high affinity for binding calcium
false, calsequestrin has a high capacity but a low affinity for binding calcium
what are the voltage sensing molecules at the points of contact between T-tubules and the SR?
dihydropyridine receptors (DHP-receptors)
what induces the opening of calcium-release channels on the SR membrane?
conformational change in DHP-receptors
what is the peak concentration of calcium after diffusion from the SR?
10^-5 M
where is tropomyosin located?
along the groove of the actin helix
how many actin monomers does one tropomyosin cover?
7
what causes the tropomyosin to roll away from the myosin-binding sites of actin?
binding of calcium to troponin
t/f... troponin is in contact with tropomyosin
true
t/f... heat is produced during hydrolysis of MgATP
true
what happens in the attachment step of the cross-bridge cycle?
myosin binds actin
what follows the attachment step in the cross-bridge cycle?
myosin spontaneously undergoes a bending movement (power stroke), releasing MgADP and Pi, pulling the thin filament towards the centre of the thin filament
what occurs in the dissociation step?
the cross-bridge is displaced from actin as MgATP binds to the cross-bridge
when are the free-energy and products of hydrolysis following the dissociation step released?
power-stroke of next cycle
how is the intracellular calcium level elevated in skeletal muscle fibre?
by release of calcium from the SR
at what frequency of stimuli does tetanus occur?
100 Hz
when will muscle undergo isometric contraction?
when the load is too high for muscle to move
what is ATP converted to during an isometric contraction?
heat
what type of contraction occurs when the muscle develops a force matching the load and shortens while developing the force, doing work?
isotonic
describe the force-velocity relation
velocity of shortening is inversely related to force against which muscle shortens
at what load is maximal muscle power developed?
at a load equivalent to 1/3 maximal force of the muscle
why is a greater force produced with greater overlap between thick and thin filaments?
this increases the number of interactions between cross-bridges and thin filaments
are type I muscle fibres slow or fast-contracting?
slow
how do type I muscle fibres generate ATP?
oxidative metabolism
which is faster, IIA muscle fibres or IIX fibres?
IIX
how do IIX fibres generate ATP?
anaerobic respiration via the breakdown of glycogen to lactic acid (incurring an oxygen debt)
in motor unit recruitment for increasing demand, which motor units are recruited first?
small motor units
how is muscle hypertrophy stimulated by intense regular exercise?
replication of satellite cells (myoblasts) and incorporation into paretn fibres, increase in protein synthesis and decreased breakdown
what occurs in muscle atrophy?
increased protein degradation, loss of myofibrils, reduced fibre cross-sectional area, fibre type changes
where are the satellite cells found?
between the basal lamina and the sarcolemma of each fibre
how is necrotic tissue removed following injury to muscle?
macrophages
what do injured tissues release to stimulate replication of satellite cells?
growth factors
how do satellite cells initiate regenerative myogenesis?
satellite cells undergo fusion to form myotubes within the basal lamina which then mature into new muscle fibres
what is the longest branch of the brachial plexus?
radial nerve
which cord does the radial nerve come from?
posterior cord
where does the radial nerve travel in the forearm relative to the radial aretery?
lateral to the radial artery
where does the palmar branch of the median nerve travel?
anterior to the carpal tunnel
which flexor is supplied by the radial nerve?
brachioradialis
where are voltage gated sodium channels concentrated in myelinated nerve fibres?
axon hillock and nodes of ranvier
which pump maintains the resting membrane potential?
Na+/K+ pump (Na+/K+-ATPase)
what are the three axes in the limb bud?
proximodistal
anteroposterior
dorsoventral
when do the cells in the limb bud become "determined" to form a particular part of the adult limb?
from about day 26 to day 33
where does the signal for proximodistal development come from?
apical ectodermal ridge
which axis of development is associated with FGF-8?
proximodistal
which axis of development is associated with a signal from zone of polarising activity and involves sonic hedgehog?
anteroposterior
where does the signal for development of the dorsoventral axis originate?
dorsal ectoderm and ventral ectoderm
what is the incidence of congenital hip dysplasia?
3-4 per 1000 live births
what is muscle force controlled by?
number of motor units recruited and frequency at which motor unit firesqq
what is myotonia?
failure to relax at the end of a voluntary contraction
what does muscle consume ATP for?
cross-bridge cycling
SR Ca pump
Na pump
t/f... skeletal muscle is quite resistant to ischaemia
true
what type of training will cause fast fibres to convert to slow fibres?
endurance training