Muscles 1

Question 1

Muscles

Answer 1

Are tissues that transform chemical energy(ATP) into mechanical energy that produces force

Question 2

Functions

Answer 2

• produce movement
• maintains posture and body position
• stabilizes joints
• generates heat as they contract

Question 3

The 3 types of muscle tissues

Answer 3

Skeletal, cardiac and smooth muscle
- all differ in location, structure, function and type of control

Question 4

Skeletal Muscle

Answer 4

• attached. To bones and the skin
• they are voluntary: controlled consciously and we are aware of these moving
• the skeletal muscle cells are multinucleate and has a striated patterm

Question 5

Cardiac Muscle

Answer 5

• only in the heart
• they are involuntary, we don’t control them
• the cardiac muscle cells are branched and stratified with 1 centrally located nucleus
• neighbouring cells are connected by gap junctions called intercalated discs

Question 6

Smooth Muscle

Answer 6

Forms the walls of hollow organs like the stomach, urinary bladder and airways
- they are involuntary
- the smooth muscle cells are non striated and have only 1 centrally located nucleus to conform to a spindle cell shape

Question 7

All muscles tissues share 4 main characteristics

Answer 7

• Excitability: ability to receive and respond to stimuli
• Contractility: ability to shorten forcibly when stimulated
• Extensibility: being able to get stretched
• Elasticity: being able to get recoiled to its resting length

Question 8

Muscles are both

Answer 8

An organ and a tissue type

Question 9

The skeletal muscle is organized by connective tissue

Answer 9

Epimysium: covers the outer skeletal muscle
Perimysium: surround a bundle of muscle fibres called a fascicle
Endomysium: surround a single muscles fibre( the cells of muscles)
- look at diagrams

Question 10

Muscle fibres contain

Answer 10

Sarcolemma: muscle fibre plasma membrane
Sarcoplasm: muscle fibre cytoplasm

Question 11

Sacroplasmic reticulum(SR)

Answer 11

• a specialized smooth ER
  -surrounds contractile organelles called myofibrils
• stores and releases calcium ions
• termiap cisternae are attached to T tubules

Question 12

Transverse(T) tubules

Answer 12

Invitations of the sacrilege rich in ion channels that runs transversely through a muscle fibre

Question 13

A Triad

Answer 13

Is the terminal cisternae of neighbouring SR and 1 T tubule

Question 14

Myofibrils

Answer 14

• specialized organelles that account for around 80% of muscle fibre volume
• consists of contractile units called sarcomeres that are aligned end to end

Question 15

Sacromere

Answer 15

• has bundles of thick and thin filaments
• the different regions form dark and light bands called striations

Question 16

What does each region contain?

Answer 16

I band: thin filament only(light region)
A band: overlapping thick and thin filaments(Dark region)
H zone: thick filaments only

Question 17

During contraction , what occurs to each region?

Answer 17

I band: shortens
A band: doesn’t change in length
H zone: shortens and can disappear

Question 18

Myofilaments

Answer 18

Consists of both thick and thin filamebts

Question 19

Thin filaments

Answer 19

• are made up of actin
• each actin has a myosin binding site
  Topomysin and troponin are regulatory protein complexes bound to this
• troponin binds calcium

Question 20

Thick filaments

Answer 20

are made of bundles of myosin.
Each myosin has a head and a tail region
• heads are staggered and have actin-binding sites and ATP-binding site

Question 21

Neuromuscular Juction(NMJ)

Answer 21

• also known as the motor end plate or motor synase
• where signals from the nervous system reach the skeletal muscle fibres

Question 22

The order of which happens at the NMJ

Answer 22

1. An electrical impulse called action potential arrive at the axon terminal of the NMJ
2. Calcium enters the neuron’s terminal.
3. Neurotransmitter called acetylcholine (ACh) stored in vesicles are released into the synaptic cleft.
4. (ACh) binds receptors on the muscle fibre membrane
5. Ligand-gated sodium channels lead to depolarization known as end-plate potential.

Question 23

Excitation-Contraction(E-C) Coupling

Answer 23

A co fraction is the result of the excitation of skeletal muscle cells by the nervous system
- it’s in the form of action potential that travels down the sarcolemma to the triad
- the T tubules trigger Ca from the SR

Question 24

What role does calcium pay in the sarcomere to initiate contraction?

Answer 24

• Ca+ binds to troponin, which moves tropomyosin away and exposes myosin-binding sites on actin
• Enables binding between thin and thick filaments to form a structure called a cross bridge
- required for it to take place

Question 25

The cross bridge cycle

Answer 25

• also know as the sliding filament model
• is the molecular mechanism of muscle contraction:
• thin filaments constantly slide over thick filaments and generate muscle tension

Question 26

Has 4 steps

Answer 26

1. Reactivation if myosin head
2. Cross-bridge formation
3. Power-stroke
4. Cross-bridge detachment
   Look at diagram

Question 27

What role does ATP play in the cycle

Answer 27

ATP binding is needed to break the cross-bridge (detachment stage)
• ATP hydrolysis is needed to “cock” the myosin head into place (reactivation stage)

Question 28

Rigor mortis is a post-mortem process where chemical changes in the myofibrils lead to stiffening of body muscles. What is the cause of this?
A) the cells are dead
B) sodium ions leak into the muscle causing continued contractions
C) no ATP is available to release attached actin and myosin molecules
D) proteins are beginning to break down, thus preventing a flow of calcium ions

Answer 28

C