Muscle Physiology

Question 1

are made up of several hundred to several thousand of parallely arranged myofibrils having the special function of contraction.

Answer 1

Muscle fibres

Question 2

Each _____ posses the contractile proteins myosin (thick) and actin (thin) myofilaments results in regular repetition of dark and light bands in the skeletal and cardiac muscles.

Answer 2

myofibril

Question 3

• is a large protein molecule composed of 6 polypeptide chains 2 of which are 100% α – helically exist.
• has enzymatic ability to split ATP and release energy.
  Enzyme is ____ ATPase.

Answer 3

Myosin

Question 4

are required for activating these enzymes.

Answer 4

Actin and Mg2+

Question 5

much smaller molecule than myosin and contains only one polypeptide chain per molecule.

Answer 5

Actin

Question 6

molecules are rod shaped they lie in the 2 grooves of the double stranded actin filament and aggregate end to end to produce two strands of tropomyosin running enter length of this filament.

Answer 6

Tropomyosin

Question 7

More ellipsoidal or globular molecule, binds to a particular site on the tropomyosin molecule.

Answer 7

Troponin

Question 8

This chain has site for attachment with tropomyosin

Answer 8

Troponin – T

Question 9

Inhibits the actin activated myosin ATP ase. attach not only with troponin C and T and but also with actin in the absence of Ca2+.

Answer 9

Troponin – I

Question 10

binding sites (4 numbers) for Ca2+

Answer 10

Troponin – C

Question 10

The electron microscopic view of light bands indicates actin filaments represented as “I” bands because they are isotropic to polarised light. The dark bands of myosin is represented by “A” Band, which are anisotropic to polarised light.

Answer 10

I and A Band

Question 10

represents partial overlapping the myosin filaments with actin filament.

Answer 10

“H” zone

Question 10

Small projections of myosin filaments called _____protrude out of the myosin filaments along the entire length except the very centre of the myosin filament.

The protruding arms and heads together are called.

Answer 10

cross-bridges

Question 11

The centre of I bands contain a dark line called the “____” or “z disc” where the ends of the actin filaments are attached. The z-discs are filamentous proteins, located in a vertical position in the myofibril.

Answer 11

Z line

Question 12

The _____ is the physiological contractile unit of muscle.

Answer 12

sarcomere

Question 13

of the myofibril, is a dark line seen at the centre of “A” band, is rarely seen in normally functioning muscle.

Answer 13

“H” Band

Question 14

Cross striated and attached to skeleton, 40% of the total body weight, Voluntary neural control.

Answer 14

Skeletal muscles

Question 15

Cross striated in structure, Involuntary in function, Under autonomic nervous system control.

Answer 15

Cardiac muscle

Question 16

are simple due to ill developed sarco plasmic reticulum. cardiac muscles have rich mitochondrial supply and many Ca-Na exchangers.

Answer 16

Triads

Question 17

They contain contractile proteins which are activated by action potential.

Answer 17

Sarcolemma.

Question 17

like neurons can be excited chemically, electrically and mechanically to produce an action potential that is transmitted along their cell membrane

Answer 17

Muscles cells,

Question 17

No cross striations found, poorly organized Actin and Myosin filaments.Ratio of Actin and Myosin is 15:1, Absence of Troponin complex.

Answer 17

Smooth muscle

Question 18

Muscles are surrounded by a sheet of connective tissue called _________ (site for fat deposition).

Answer 18

epimysium

Question 19

From epimysium smaller sheets of connective tissue called _____ arise and divide muscle into several small bundles.

Answer 19

perimysium

Question 20

Each muscle fiber is enclosed by _____ which is a fine sheet of connective tissue arising from perimysium.

Answer 20

endomycium

Question 21

In a muscle, the muscle fibers are arranged as number of muscle bundles known as _____

Answer 21

“fasciculus”

Question 22

is the fluid present inside each fiber in which the organelles like sarcosomes(mitochondria), sarcoplasmic reticulum and myofibrilare suspended.

Answer 22

Sarcoplasm

Question 22

Muscle cell contains organelles like sarcolemma, nucleus, Golgi apparatus, lysosomes, mitochondria or _____, endoplasmic or sarcoplasmic reticulum, peroxisomes and ribosomes and myofibrils.

Answer 22

sarcosomes

Question 23

Because skeletal muscle cell in a mature muscle originates form fusion of 100 – 200 different embryonic muscle cells called , with each _____contributing one nucleus.

Answer 23

myoblasts

Question 24

At one end of these chains get folded into a globular structure called

Answer 24

myosin head

Question 24

The elongated coiled portion of the myosin molecule is called __ formed by HMM – S2 molecule has no ATPase activity and binding property with “G” actin.

Answer 24

tail

Question 25

Cytoplasm of the muscle cell is called sarcoplasm which contains ______.

Answer 25

myoglobin

Question 26

is present which is a transverse structure connecting thick filaments at their centre is made up of M protein and creatine kinase.

Answer 26

‘M’ line

Question 27

Along with the head, __ extends outward from the body of the myosin filament.

Answer 27

“arm”

Question 28

It is composed of three proteins; actin, tropomyosin and troponin

Answer 28

Actin Filament

Question 28

The __ are located at the junction of “A” and “I” bands which pass through the fibres, open into the inter-fibre space, permits the flow of extracellular fluid.

Answer 28

“T”’ tubules

Question 28

The flexible points of the arm are __ which allow the head to be extended outward or brought closer to the body of myosin filament.

Answer 28

hinges

Question 28

Muscle cells also contain a special structure called __ which has two sets of tubules.

Answer 28

sarcotubular system

Question 29

In smooth muscle instead of troponin another regulatory protein ___ reacts with four Ca++ ions.

Answer 29

“calmodulin”

Question 29

The presence of ___ in actin filament inhibits the binding reaction of actin with myosin.

Answer 29

troponin and tropomyosin (tt-complex)

Question 29

The __ possess ATPase enzyme, which helps to cleave the ATP to release energy for the contraction process.

Answer 29

myosin head

Question 29

The T system consist of set of tubules formed by the invaginations of the.

Answer 29

plasmalemma

Question 30

Present parallel to myofibrils. At both the ends of the tubule, bulbous structures known as terminal cisternae function as a storage place for the Ca++ ions and play a key role in muscle contraction.

Answer 30

`L’ Tubule system

Question 31

It is a paired cisternae and a “T” tubule in between the cisternae.

Answer 31

Triad

Question 32

This cycle is known as ___

Answer 32

Excitation Contraction Coupling.

Question 33

is the resting cell membrane with a normal negative resting membrane potential.

Answer 33

Polarised membrane

Question 33

The ___ is caused by a sequence of changes or events occurring in the membrane permeability to Na+ and K+ ions.

Answer 33

action potential

Question 34

is the first event of action potential is characterised by rapid increase in the permeability to Na+ ions (5000 folds) to interior of the cell generating more positive electrical potential inside of the cell.

Answer 34

Depolarization stage

Question 35

It is associated with gradual opening of ___ channels to allow K+ ions outflow to the exterior of the cell membrane.

Answer 35

voltage gated K+

Question 36

This stage is called as the

Answer 36

repolarisationstage.

Question 37

Higher concentration of K+ ions in the exterior of the cell towards the end of the action potential continues for a short period creates more negativity inside referred to as

Answer 37

hyper-polarised state.

Question 38

The final event is characterised by ___ which aids in the transport of three Na+ ions to the exterior for every two K+ ions to interior of the cell and create the normal resting potential (- 75 mV) on the inside of the cell membrane.

Answer 38

electrogenic pump mechanism,

Question 39

The ___ have two gates, the external gate or activation gate which opens to outside of the cell.

Answer 39

voltage gated Na+ channels

Question 40

Electro-chemical changes during action potential Spike potential

Answer 40

(over shoot)

Question 40

During __, these series elastic components develop greater tension that opposes the contraction of the myofibrils.

Answer 40

isometric contraction

Question 40

This electrical potential difference across the cell membrane is called as

Answer 40

“membrane potential”.

Question 41

This channel has only one gate at the interior of the membrane.

Answer 41

Voltage – gated potassium channel

Question 42

In __, the contractile elements shorten and stretch the series elastic components.

Answer 42

isotonic contractions

Question 42

The motor neuron branches at its end and each branch comes into a close opposition with the skeletal muscle at a specialized area called the __ or motor end plate.

Answer 42

neuromuscular junction

Question 43

- This synapse has a presynaptic membrane, a narrow space between the nerve and muscle, called __ and a post synaptic membrane sarcolemma. - is a narrow space of 20 to 30nm wide separates the presynaptic membrane and postsynaptic sarcolemma membranes.

Answer 43

synaptic cleft

Question 44

The __ is the terminal portion of the axon of the motor neuron; the extends from the CNS to the muscle cell.

Answer 44

presynaptic knob

Question 45

The axoplasm contains a large number of vesicles called synaptic vesicles; contain the excitatory neurotransmitter substance __.

Answer 45

acetylcholine

Question 45

The __ contains a large number of vesicles called synaptic vesicles; contain the excitatory neurotransmitter substance acetylcholine.

Answer 45

axoplasm

Question 46

The synaptic cleft contains an enzyme, ___, to hydrolyze acetylcholine.

Answer 46

acetylcholinesterase

Question 47

The postsynaptic cell membrane has a series of invaginations called __ that increase the surface area of the postsynaptic membrane.

Answer 47

junctional folds

Question 48

is a neuromuscular disorder in which autoantibodies are produced against acetylcholine receptors.

Answer 48

Myasthenia gravis