lecture 6 - skeletal muscle

Question 1

epimysium

Answer 1

connective sheath that surrounds the entire muscle and blends into intramuscular sheaths to form tendons

Question 2

perimysium

Answer 2

surround fasicles

Question 3

endomysium

Answer 3

wrap each muscle fibre and separate it from neighbouring fibres

Question 4

sarcolemma

Answer 4

surround each muscle fibre and enclose fibre’s cellular contents

Question 5

sarcoplasmic reticulum

Answer 5

connective tissue that provides structural integrity

Question 6

origin location

Answer 6

closer to spinal cord

Question 7

insertion location

Answer 7

further from spinal cord

Question 8

what happens to the muscle composition during exercise

Answer 8

the vascular bed delivers lots of blood to active tissues to accomodate for increased oxygen need

Question 9

what happens to muscle capillarisation during increased shear stress

Answer 9

increase pressure on the capillary walls which increase the number of capillaries

Question 10

fusiform muscle pennation

Answer 10

fibres run the full length of the muscle

Question 11

pennate muscle pennation

Answer 11

fibres run over a portion of the muscle

Question 12

describe the mechanical actions of myofilbril crossbridges

Answer 12

muscle resting length produces greatest force due to increased fibre crossover

Question 13

what is the dissociation of actomyosin equation

Answer 13

actomyosin + ATP –> Actin + Myosin-ATP

Question 14

Excitation-contraction coupling definition

Answer 14

physiological mechanism whereby an electrical discharge at muscle initiates chemical events at cell surface to release intracellular Ca+2 and produce muscle action

Question 15

what occurs during muscle relaxation

Answer 15

when muscle stimulation ceases, calcium activity stops and troponin frees up to inhibit actin-myosin interaction

Question 16

What does deactivation do in muscle relaxation

Answer 16

1. prevents any mechanical link between myosin crossbridges and actin filaments
2. inhibit myosin ATPase activity to curtail ATP splitting

Question 17

characteristic of type 2 muscle fibres

Answer 17

1. high myosin ATPase activity
2. high rate of crossbridge turnover
3. rapid calcium release and uptake by sarcoplasmic reticulum
4. rely on well-developed, short term glycolytic system for energy transfer

Question 18

Characteristics of type 1 muscle fibres

Answer 18

1. low myosin ATPase activity
2. slow calcium handling ability and shortened speed
3. less well-developed glycolytic capacity tham fast twitch fibres
4. large and numerous mitochondria
5. highly fatigue resistance

Question 19

what type of muscle fibres do endurance athletes have

Answer 19

slow twitch fibres

Question 20

what muscle fibre types do elite sprint athletes have

Answer 20

fast twitch fibres

Question 21

genetics

Answer 21

set of genes you have

Question 22

epigenetics

Answer 22

expression of genes

Question 23

what occurs to muscle memory during exercise

Answer 23

increased myonuclei on muscle cells, change in genetic receptors

Question 24

what does the CNS consist of

Answer 24

brain and spinal cord

Question 25

what does the PNS consist of

Answer 25

nerves transmitting information to and from CNS

Question 26

what is the function of the spinal cord

Answer 26

communication throughout the body via spinal nerves of the PNS

Question 27

what are the 3 types of neurons

Answer 27

motor neurons, sensory neurons, interneurons

Question 28

what are the pathways in the descending nerve tracts

Answer 28

pyramidal tract and extrapyramidal tract

Question 29

afferent neurons

Answer 29

enter spinal cord through dorsal root and transmit sensory input from peripheral receptors

Question 30

describe the path of a reflex arc

Answer 30

1. afferent neurons enter spinal cord through dorsal root and transmit sensory input from peripheral receptors 2. neuron synapse in spinal cord relay information to different cord levels 3. impulse then passes over motor root pathway via the anterior motor neurons to effector

Question 31

motor unit

Answer 31

anterior motor neuron and specific muscle fibre it innervates

Question 32

neuromuscular junction

Answer 32

end of a myelinated motor neuron and muscle fibre

Question 33

describe the process of excitation at the neuromuscular junction

Answer 33

1. when an impulse arrives at the neuromuscular junction, ACH released from vesicles into the terminal axon, then into the synaptic cleft 2. ACH then combines with transmitter-receptor complex in postsynaptic membrane 3. change in electrical properties which causes the endplate potential to spread 4. action potential travels the muscle fibre length, enter T tubule system that spreads to the inner structures of muscle fibre to prime contractile machine for excitation

Question 34

describe the facilitation process at the neuromuscular junction

Answer 34

1. ACH release excites postsynaptic membrane of its connecting neuron 2. enhanced facilitation results in full muscle activation during all out efforts

Question 35

what are 3 factors that produce neuronal facilitation

Answer 35

1. decreased sensitivity of the motor neuron to inhibitory neurotransmitters 2. reduced quantity of inhibitory neurotransmitter substance transported to the motor neuron 3. combined effect of both mechanism

Question 36

describe the twitch characteristics of type 1 fibres

Answer 36

slow twitch, low force, fatigue resistant

Question 37

describe the twitch characteristics of type 2a fibres

Answer 37

fast twitch, moderate force, fatigue resistant

Question 38

describe the twitch characteristics of type 2x fibres

Answer 38

fast twitch, high force, fast fatigue

Question 39

all or nothing principle

Answer 39

stimulus is either strong enough to trigger an action potential or not

Question 40

how can force of muscle action vary

Answer 40

increased number of motor units recruited, increased frequency of motor unit discharge

Question 41

motor unit recruitment

Answer 41

adding motor units to increase muscle force

Question 42

size principle

Answer 42

orderly recruitment of specific motor units to produce a smooth muscle action, allow CNS to fine tune skeletal muscle activity to meet motor task demands

Question 43

fatigue

Answer 43

decline in force capacity with repeated stimulation or during a given time period

Question 44

components that impact voluntary muscle action

Answer 44

CNS, PNS, neuromuscular junction, muscle fibre

Question 45

what is the function of sensory receptors

Answer 45

relay information about muscle dynamics and limb movements to CNS conscious and subconscious areas

Question 46

what is the function of muscle spindles

Answer 46

provide mechano-sensory information about changes in muscle fibre length and tension

Question 47

describe the 3 compartments of the stretch reflex

Answer 47

1. muscle spindle - responds to stretch 2. afferent nerve fibre - carry sensory impulse from spindle to spinal cord 3. efferent spinal cord motor neuron - activate stretched muscle fibre

Question 48

what is the function of golgi tendon organs

Answer 48

detect changes in tension by muscle; protect muscle and surrounding connective tissue

Question 49

what impulses does the golgi tendon organ respond to

Answer 49

1. tension created in muscle when it is shortened 2. tension when muscle stretches passively 3. transmit signals to spinal cord to elicit muscle reflex inhibition