Muscles Flashcards

Question

connection between T-tubules and sarcoplasmic reticulum

Answer 1

junctions comprised of two integral membrane proteins (one in each of the membranes) the protein in the T-tubule membrane is a modified voltage-sensitive Ca2+ channel (DHP receptor). detects depolarisation and triggers protein in SR to release Ca2+

Answer 2

AT propagated into T-tubules Ca2+ released from lateral sac of SR Ca2+ binding to troponin removes blocking action of tropomyosin cross bridges form between actin and myosin and generate force by moving through power strokes ATP causes release of myosin head and its return to original state if Ca2+ and ATP still present, myosin head will attach to another binding site AT complete, Ca2+ taken back into sarcoplasmic reticulum binding sites blocked

Answer 3

ATP binds to myosin head=conformation change=reduced affinity for actin=detachment from binding site ATP hydrolysed to ADP and Pi by myosin ATPase, providing the energy to reposition the myosin head back to its high-energy state

Answer 4

innervate skeletal muscle cell bodies located in brainstem or spinal cord myelinated axons terminal branches create junctions with thousands of muscle fibres

Answer 5

motor neurone and the skeletal muscle fibres it innervates many motor units within a muscle activate different number of motor units to control level of force if the threshold of a motor unit is reached all of the fibres in that motor unit will generate their maximal force (for their length and velocity). each motor unit has an all or nothing response

Answer 6

junction of an axon terminal of motor neurone with motor end plate (region of muscle fibre plasma membrane directly under the neurone)

Answer 7

AT through motor neurone=Ca2+ enters via voltage gated channels acetylcholine released and binds to nicotinic receptors on muscle fibre opens ion channels in motor end plate. more Na+ in than K+ out Na2+ entry depolarises motor end plate spreads to adjacent sarcolemma AT propagates along sarcolemma

Answer 8

time for excitation-contraction coupling

Answer 9

brief, single contraction of a muscle fibre in response to a single action potential from a motor neuron

Answer 10

latent period contraction phase (takes a while to build up as more cross bridges form with more Ca2+) relaxation phase (due to how long it takes to take up all Ca2+, longer than contraction period)

Answer 11

when the frequency of stimulation is high enough for force to remain constant for the period of activation sustained contraction-Ca2+ doesnt return to SR

Answer 12

multiple action potentials to a muscle fibre before it relaxes causes summation in tension

Answer 13

fluctuation in force generated as muscle stimulated repeatedly at high frequency

Answer 14

in reality, muscle fibres are stimulated by multiple action potentials by stimulating a fibre repeatedly before its gone through relaxation, more force is generated that becomes sustained

Answer 15

number of cross bridges formed which is influenced by the length of the muscle fibres/sarcomeres and the contraction velocity level of activation (number of motor units stimulated) and time since onset of activation also have influence

Answer 16

actin and myosin cant overlap if actin is overlapping with other actin (very short) optimum overlap=maximum number of binding sites=maximum force decrease in force as length increases past optimum as overlap decreases

Answer 17

muscles fibres are connected via collagen tendons and themselves contain collagen which is stretchy/elastic. when you stretch a muscle beyond its resting length while the tension produced by the sarcomeres is decreasing, the amount of force produced by the elastic tissues increases

Answer 18

just below and above optimum length

Answer 19

quicker cross bridges have to form=fewer crossbridges bonded at any given time=less force

Answer 20

lengthen=more force from elastic tissue whether done slow or fast fast eccentric contraction dangerous

Answer 21

how many motor units activated different motor units are activated at different times so the time since inset of activation also influences force

Answer 22

slow/fast/very fast (maximal velocities of shortening) oxidative or glycolytic (major pathway used to form ATP)

Answer 23

contain different isomers of myosin that attach and detach from actin at different speeds. differ in maximal rate at which ATP is used heavy chain responsible for this determines maximal rate of crossbridge cycling and maximal shortening velocity

Answer 24

Phosphorylation of ADP by creatine phosphate- when muscle first activated Oxidation phosphorylation of ADP in mitochondria (Aerobic) Glycolytic phosphorylation of ADP in the absence of oxygen (Anaerobic)

Answer 25

high number of mitochondria so high capacity for oxidative phosphorylation dependent on blood flow to deliver oxygen

Answer 26

fewer mitochondria high concentration of glycolytic enzymes and a large store of glycogen can produce a lot of force quickly muscle fatigue once glycogen runs out

Answer 27

Slow-oxidative fibres (Type I) combine low myosin-ATPase activity with high oxidative capacity. Fast-oxidative-glycolytic fibres (Type IIa) combine high myosin-ATPase activity with high oxidative capacity and intermediate glycolytic capacity. Fast-glycolytic fibres (Type IIx) combine high myosin-ATPase activity with high glycolytic capacity.

Answer 28

constant force 50ms contraction phase (long time) 10mN (low) fatigue resistant

Answer 29

greater force and a bit quicker than slow oxidative fibres over time produces less force as glycolytic pathway out of fuel

Answer 30

lots of force generated and quick contraction period force drops off quickly, cannot sustain

Answer 31

Each muscle has a combination of all of the fibre types. Proportion of the types vary. Fibre types differ in threshold of activation, lower in small/slower muscle fibres (time since onset of activation)

Answer 32

if not all motor units within a muscle are activated = submaximum contraction activate all units=maximum force there is a period of ramping up to that activation as more motor units are recruited

Answer 33

measures action potentials in muscle fibres

Answer 34

The co-ordinated activation of muscles to produce controlled movement involves neurones organised into hierarchal levels

Answer 35

Voluntary movement is initiated by the higher centres in the brain These signals are then relayed to the middle areas of brain which co-ordinate the movement And onto the MOTOR NEURONS which activate the MUSCLES (efferent signals) SENSORY FEEDBACK comes back from SENSORY RECEPTORS in the muscles and joints (afferent signals) to modulate the movements

Answer 36

sensory receptors within muscles and joints tell CNS what is happening in muscles responsible for reflex actions

Answer 37

proprioceptors that provide feedback on muscle length wrap around fibres

Answer 38

proprioceptors that provide feedback on muscle force found where muscles join to tendon, stimulated when tendon stretches

Answer 39

When muscle is stretched afferent signal from muscle spindle to spinal cord Synapes with motor neuron of stretched muscle which causes it to contract to resist the stretch (monosynaptic) Also synapses with inhibitory interneuron which inhibits motor neurons to the flexor muscle Afferent signal from muscle spindle also goes to higher centres (brain) so movement becomes ‘conscious’ PROTECTS MUSCLE FROM TOO MUCH STRETCH

Answer 40

Painful stimulus Pain detected by nociceptor and signal sent to spinal cord Synapses with motor neuron of flexor muscle to flex knee and withdraw foot Inhibitory interneuron results in inhibition of ipsilateral extensor muscle to facilitate this movement Reflex also crosses to contralateral side to increase weight support on that side Excitatory interneuron to contralateral extensor Inhibitory interneuron to contralateral flexor Afferent signal from nociceptor also goes to higher centres (brain) and pain becomes conscious

Answer 41

responsible for reflexes regulation

Answer 42

Painful, spasmodic and involuntary contraction of skeletal muscle that occurs during or immediately after exercise Occurs in activated muscle groups Can be relieved by passive stretching and massage. Resets inhibitory pathways

Answer 43

Electrolyte depletion and dehydration Change in sodium potassium, magnesium or calcium concentration in plasma, disrupted ion balance in muscles, affecting ability to turn on/off No prospective studies to support this theory Altered neuromuscular control Altered reflex control due to fatigue Excitatory input overwhelms inhibitory input

Answer 44

Microdamage to muscle which results in minor inflammation and pain, but is normal and important for muscle adaptation Occurs as a result of overload of muscle Particularly due to eccentric exercise Results in up regulation of protein synthesis and adaptation of muscle to new load

Answer 45

weakening and breakdown of muscle over time

Answer 46

Genetic condition caused by mutation in the gene for the protein dystrophin on X chromosome Dystrophin important in linking myofibrils to sarcolemma Lack of dystrophin results in muscle fibre disorganisation and death Affects muscles of pelvis and lower limb first progressing to the upper limbs and respiratory muscles Results in premature death

Answer 47

Toxins Autoimmune conditions (attack motor neurones) Multiple sclerosis (reduction in insulation) Cerebral palsy (damage to brain affects sensory feedback) Motor neuron disease

Muscles Flashcards

(71 cards)