Physiology: muscles

Question 1

describe the physiological functions of skeletal muscles

Answer 1

maintain posture, respiratory movements, heat production, contribute to metabolism, voluntary movement

Question 2

what are the 3 types of muscle

Answer 2

smooth, cardiac and skeletal

Question 3

what muscle types are striated

Answer 3

cardiac and skeletal

Question 4

what muscle type is unstriated

Answer 4

smooth

Question 5

describe the structure of actin

Answer 5

thin filaments that appear as light bands

Question 6

describe the structure of myosin

Answer 6

thick filaments that appear as dark bands

Question 7

what are skeletal nerves innervated by

Answer 7

the somatic nervous system(voluntary)

Question 8

what are the smooth and cardiac nerves innervated by

Answer 8

the autonomic nervous system(involuntary)

Question 9

describe the initiation of contraction for skeletal and cardiac muscle

Answer 9

skeletal = neurogenic(motor units)
cardiac = myogenic

Question 10

what junction are involved in skeletal and cardiac muscles

Answer 10

skeletal = neuromuscular junctions
cardiac = gap junctions

Question 11

describe the excitation contraction coupling of skeletal muscle

Answer 11

Ca2+ entirely from sarcoplasmic reticulum

Question 12

describe the excitation contraction coupling of cardiac muscle

Answer 12

Ca2+ from ECF and sarcoplasmic reitculum

Question 13

what does the gradation of contraction of cardiac muscle depends on

Answer 13

extent of filling of the heart with blood(preload)- the Frank Starling mechanism

Question 14

what is the neurotransmitter involved in neuromuscular junctions

Answer 14

Acetylcholine

Question 15

what are skeletal muscle fibres(cells) organised into

Answer 15

motor units

Question 16

what is a motor unit

Answer 16

a single alpha motor neuron and all the skeletal muscle fibres it innervates
allow simultaneous contraction of a number of muscle cells

Question 17

describe how the number of muscle fibres per motor unit varies depending on function

Answer 17

fewer(~10) fibres = finer movements(eg eye)

hundreds to thousands fibres = power over precision(eg thigh)

Question 18

what is structure contained in a muscle fibre(cell)

Answer 18

myofibril(specialised intracellular structure)

Question 19

what is the functional unit of muscle cells(fibres)

Answer 19

sarcomeres

Question 20

what protein molecules are found in myofibril in muscle cells(fibres)

Answer 20

myosin and actin

Question 21

how long are skeletal muscle cells

Answer 21

usually extend the length of the muscle

Question 22

describe how muscles are usually attached to the skeleton

Answer 22

by tendons

Question 23

how are actin and myosin arranged in myofibril and what is this arrangement called

Answer 23

by alternating segments of thin(light) actin bands and dark(thick) myosin bands
called a sarcomere

Question 24

what is the functional unit of any organ

Answer 24

the smallest component capable of carrying out all the functions of that organ

Question 25

what are sarcomeres found between, and what separates them

Answer 25

Z-lines, which connect the 2 thin filaments(actin) of adjoining sarcomeres

Question 26

what are the 4 zones of the sarcomere

Answer 26

H-zone, A-band, I-band, M-line

Question 27

describe the structure of the A-band of a sarcomere

Answer 27

made up of thick filaments along with portions of thin filaments that overlap in both ends of thick filaments

Question 28

describe the structure of the H-zone of a sarcomere

Answer 28

lighter area within middle of A-band where thin filaments don't reach

Question 29

describe the structure of the M-line of a sarcomere

Answer 29

extends vertically down middle of A-band within the centre of H-zone

Question 30

describe the structure of I-band of a sarcomere

Answer 30

consists of remaining portion of thin filaments that do not project into A-band

Question 31

how is muscle tension produced

Answer 31

by actin(thin) molecules sliding on the thick(myosin) filaments

Question 32

what is force generation of a muscle dependant on

Answer 32

ATP-dependant interaction between the actin(thin) and myosin(thick) filaments

Question 33

what is ATP required for in muscles

Answer 33

contraction and relaxation

Question 34

what is CA2+ required for in muscles

Answer 34

to switch on cross bridge formation

Question 35

what is excitation contraction coupling

Answer 35

process by which surface action potential results in activation of contractile structures of muscle fibres

Question 36

when is Ca2+ released in skeletal muscle fibres

Answer 36

when the surface action potential travels spreads down the transverse (T)-tubules

Question 37

where is Ca2+ released from on skeletal muscles

Answer 37

lateral sacs of sarcoplasmic reticulum

Question 38

describe how Ca2+ allows for cross bridge formation

Answer 38

Ca2+ binds with troponin, which pulls the troponin-tropomyosin complex to the side exposing the cross bridge binding site

Question 39

what are the 2 primary factors in determining gradation of skeletal muscle tension

Answer 39

number of muscle fibres contracting within the muscle | and the tension developed by each contracting muscle fibre

Question 40

what is motor unit recruitment

Answer 40

when stronger contraction is achieved by simultaneous contraction of multiple motor units

Question 41

describe the process that helps to prevent muscle fatigue

Answer 41

asynchronous motor unit recruitment during submaximal contractions

Question 42

what does the tension developed by each contracting muscle fibre depend on

Answer 42

frequency of stimulation, summation of contractions, length of muscle fibres, thickness of muscle fibres

Question 43

describe the relative time of an action potential and a muscle twitch, and what this means

Answer 43

action potential much faster than a muscle twitch, therefore multiple action potentials can occur in one twitch

Question 44

describe what tetanus is

Answer 44

when a muscle fibre is stimulated so rapidly it doesn't have time to relax in between contractions, results in a sustained contraction

Question 45

what type of muscle can't be tetanised

Answer 45

cardiac muscle

Question 46

how does frequency of stimulation relate to strength of contraction

Answer 46

as frequency increases strength of contraction increase

Question 47

when is maximal tetanic contraction achieved

Answer 47

at optimal muscle length; at point of optimal overlap of thick filament and thin filament cross bridge binding sites

Question 48

how is muscle tension transmitted to the bone in skeletal muscle contraction

Answer 48

via stretching and tightening of connective tissue and tendons(elastic component)

Question 49

describe what an isotonic skeletal muscle contraction is and what its used for

Answer 49

muscle tension remains constant as muscle length changes | used for body movements and moving objects

Question 50

describe what an isometric skeletal muscle contraction is

Answer 50

when muscle tension develops at constant muscle length | used in supporting objects in fixed positions and maintaining postures

Question 51

what determines speed of contraction of skeletal muscles

Answer 51

activity of myosin ATPase

Question 52

what determines skeletal muscles resistance to fatigue

Answer 52

capacity to synthesise ATP | greater capacity = greater resistance to fatigue)

Question 53

how many types of skeletal muscle are usually found in each motor unit

Answer 53

one type

Question 54

what different metabolic pathways supply ATP in muscle fibres

Answer 54

oxidative phosphorylation, glycolysis, transfer of high energy phosphate from creatine phosphate to ADP

Question 55

what are the different types of skeletal muscle fibres

Answer 55

slow oxidative type I(slow twitch) fast oxidative type IIa(intermediate twitch) fast oxidative type IIx(fast twitch)

Question 56

describe function of slow twitch(slow oxidative type I) muscle fibres

Answer 56

used mainly for prolonged relatively low work aerobic activities

Question 57

describe function of intermediate twitch(fast oxidative type IIa) muscle fibres

Answer 57

use both aerobic and anaerobic metabolism and are useful in prolonged relatively moderate work activities

Question 58

describe the function of fast twitch(fast oxidative type IIx) muscle fibres

Answer 58

use anaerobic metabolism and are mainly used for short-term high intensity activities