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