A & P - Muscles

Question 1

describe the structure of a cardiac muscle cell

Answer 1

small, branched cells
interconnected by selectively porous jucnctions (intercalated discs)
central nucleus
straited

Question 2

how are cardiac muscles innervated?

Answer 2

cardiac self-contractile pacemaker cells

Question 3

how are cardiac muscles regulated?

Answer 3

autonomic/involuntary nerves

Question 4

what is the function of cardiac muscle?

Answer 4

blood circulation

hydrostatic blood pressure

Question 5

describe the structure of smooth muscles

Answer 5

small, spindle shaped
single centre nucleus
non-striated

Question 6

where would smooth muscle be found in the body?

Answer 6

blood vessel walls
hollow organs
respiratory, digestive, cardiovascular and repro. tracts

Question 7

how is smooth muscle innervated?

Answer 7

self-contractile (dig. tract)

autonomic/involuntary nerves

Question 8

what is the function of smooth muscle?

Answer 8

move food, urine and repro secretions

regulation of airway and blood vessel diameter

Question 9

describe the structure of skeletal muscle

Answer 9

very long
striated
multinucleus

Question 10

where in the body would skeletal muscle be found?

Answer 10

throughout

Question 11

how is skeletal muscle innervated?

Answer 11

somatic/voluntary motornerves

Question 12

what is the function of skeletal muscle?

Answer 12

movement/stabilisation of skeleton
guards entrance/exit of dig, resp, urinary tracts
generates heat
protects organs
stores nutrients

Question 13

where would the origin of a skeletal muscle be?

Answer 13

where fixed end of muscle meets bone

Question 14

where would the insertion of a skeletal muscle be?

Answer 14

where moveable end of muscle meets bone

Question 15

if skeletal muscle was described as synergist what would this mean?

Answer 15

muscles work together in same direction

Question 16

if skeletal muscle was described as antagonist what would this mean?

Answer 16

muscle works in opposite direction to given muscle (eg. tricep/bicep)

Question 17

if a particular skeletal muscle was described as the prime mover (agonist) what would this mean?

Answer 17

that muscle is responsible for a particular movement

Question 18

if skeletal muscle was described as the fixator muscle what would this mean?

Answer 18

the muscle stabilises the origin of an agonist muscle (eg. scapula)

Question 19

name the three layers of skeletal muscle, inner to outer

Answer 19

endomysium
perimysium
epimysium

Question 20

describe the structure of epimysium in skeletal muscle

Answer 20

surrounding muscle
dense collagen layer
separates from nearby tissue

Question 21

describe the structure of perimysium in skeletal muscle

Answer 21

divides muscle into fascicles

contains collagen, elastic fibres, nerves, blood vessels

Question 22

describe the structure of endomysium in skeletal muscle

Answer 22

flexible layer inside fascicle

contains fine capillaries and nerves

Question 23

name the three types of skeletal muscle and describe them in terms of metabolism, endurance and contractility

Answer 23

type I - slow contraction, low force, high endurance, aerobic metabolism
type IIa - fast contraction, medium force/endurance, mixed metabolism
type IIb - fast contraction, high force, low endurance, anaerobic metabolism

Question 24

what does muscle size depend on? what alters this?

Answer 24

abundance of type I vs. II muscle fibres

altered by : genes, sex, age, training

Question 25

describe the size of the muscle produced by type I and II fibres

Answer 25

type I : smaller muscles | type II : bigger muscles

Question 26

what is myopathy?

Answer 26

heterogeneous group of disease with various causes (when muscle go wrong)

Question 27

name some causes of myopathy

Answer 27

``` gene mutation metabolic origin inflammation autoimmune drugs infection ```

Question 28

what is affected in myopathy?

Answer 28

just the muscle - not the neuromuscular junction or nerve

Question 29

what innervates muscle fibres?

Answer 29

motorneurones (MN)

Question 30

how do motorneurones and muscle fibres communicate?

Answer 30

in close proximity at neuromuscular junction (NMJ) | chemical signals used

Question 31

describe the innervation of muscle at the NMJ

Answer 31

1. electrical signal in MN axon 2. Ca2 channels open in pre-synaptic MN 3. Ca2 enters - fusion of vesicles containing ACh with membrane 4. ACh released into synaptic cleft - binds with ACh receptors on muscle cell 5. ACH degraded in synaptic cleft by ACh esterases 6. opening of ACh gated ion channels on muscle cell allows Na+ and K+ to flood muscle cell - electrical signal 7. muscle contracts

Question 32

what is myasthenia gravis?

Answer 32

severe muscle weakness - NMJ affected

Question 33

what are the causes of myasthenia gravis?

Answer 33

auto immune - antibodies attack ACh receptors congenital - transfer of antibodies to baby from mum (reversible) genetic - mutation affecting ACh production or signalling

Question 34

what are the symptoms of myasthenia gravis?

Answer 34

abnormal muscle fatigue - in prolonged/repetitive contraction variation in severity - daily basis/overtime

Question 35

what are the treatments for myasthenia gravis?

Answer 35

prevention ACh degradation needed (ACh esterase inhibitor, steroids, immune suppress) thymectomy - removal of thymus (antibodies made here) plasmapheresis and immunoglobulin therapy

Question 36

what is the term used for the cell membrane of a muscle cell?

Answer 36

sarcolemma

Question 37

what does the term sarcoplasm mean?

Answer 37

cytoplasm relating to a muscle cell

Question 38

what does sarcoplasm contain?

Answer 38

long, protein rich fibres called myofibrils

Question 39

what does a myofibril consist of?

Answer 39

many parallel protein strands: thin - actin thick - myosin

Question 40

what is a sarcomere?

Answer 40

arrangement of thin and thick strands making up the basic contractile unit

Question 41

how many sarcomeres are in one myofibril?

Answer 41

10,000

Question 42

describe the sliding filament mechanism

Answer 42

1. ATP turns into ADP releasing energy -converts myosin head to 'cocked' state (potential energy) 2. calcium binds to troponin - exposes sites on actin so myosin can grab actin (cross bridges formed) 3. myosin pushes on actin - actin moves (power stroke complete) 4. ATP binds to myosin making it release actin

Question 43

which two elements are needed for the sliding filament mechanism to work?

Answer 43

ATP | Ca2+

Question 44

where is the ATP needed for the sliding filament mechanism obtained from?

Answer 44

creatine phosphate aerobic metabolism anaerobic metabolism

Question 45

what is ATP needed for in the sliding filament mechanism, what happens without it?

Answer 45

ATP needed to release myosin from actin binding site | without ATP strands are permanently cross linked (rigor mortis)

Question 46

where is the Ca2+ needed for the sliding filament mechanism obtained from?

Answer 46

at rest Ca2+ is stored in the sarcoplasmic reticulum (SR) | AP triggers release of Ca2+ - this binds to actin causing a structural change making binding site available

Question 47

what can affect the active reuptake of Ca2+ by the sarcoplasmic reticulum?

Answer 47

myopathies and myotoxicity (induced by statins) affect the reuptake of Ca2+ affecting the sliding filment mechanism

Question 48

what is excitation-contraction coupling?

Answer 48

mechanism whereby excitation of muscle cell causes contraction nearly simultanously

Question 49

what would happen if the sarcomere where too stretched or too contracted?

Answer 49

reduced number of cross bridges = reduced tension

Question 50

what is an isometric contraction?

Answer 50

muscle develops tension but does not shorten (during no movement of object)

Question 51

what is an isotonic, concentric contraction?

Answer 51

muscle shortens, tension remains constant (during upward movement)

Question 52

what is an isotonic, eccentric contraction?

Answer 52

muscle lengthens while maintaining tension (during downward movement)