Wk 5

Question 1

What are muscle tissues?

Answer 1

Contractile cells that are able to adapt in shape to generate movement.

Question 2

What are the three types of muscle tissue?

Answer 2

1. Cardiac muscle (heart)
2. Skeletal muscle (bones)
3. Smooth muscle (organs)

Question 3

What is skeletal muscle tissue?

Answer 3

Structure:
- striated (stripy)
- multiple nuclei (really big)
- voluntary movements

Location:
- attached to bones (skeleton, diaphragm)

Function:
- movement
- heat production
- protection
- posture

Question 4

What is cardiac muscle tissue?

Answer 4

Structure:
- branched straited cell
- striated (stripy)
- involuntary movements
- single nucleus
- intercalated discs (gap junctions, desmosomes)

Location:
- only in heart

Function:
- heart pumps blood around body

Question 5

What is smooth muscle tissue?

Answer 5

Structure:
- spindle shaped
- non-striated
- involuntary
- single nucleus

Location:
- walls of hollow organs, conducting airways, intestines, stomach, urinary bladder etc.

Function:
- movement

Question 6

What are the two layers of smooth muscle?

Answer 6

1. Outer longitudinal layer
2. Inner circular layer

Question 7

What are the properties of skeletal muscle fibres?

Answer 7

• thick (myosin) and thin (actin) filaments; striated appearance
• multinucleated
• can hypertrophy (get bigger)
• fusion of hundreds of myoblasts
• has sarcomeres

Question 8

What are the connective tissues of skeletal muscle?

Answer 8

• Epimysium (covers entire muscle)
• Perimysium (covers fascicles)
• Endomysium (covers muscle fibre)
  *Form tendon and anchor muscle to bone

Question 9

What are the properties of cardiac muscle fibres?

Answer 9

• connect to each other with intercalated discs (gap junctions and desmosomes)
• fibres contract as single unit
• thick (myosin) and thin (actin) filaments (striated appearance)
• can hypertrophy (get bigger)
• has sarcomeres
• single nucleus

Question 10

What are the connective tissues of cardiac muscle?

Answer 10

• Perimysium (covers fascicles)
• Endomysium (covers muscle fibre)

Question 11

What are the properties of smooth muscle fibres?

Answer 11

• connect with gap junctions
• contract as single unit
• thick (myosin) and thin (actin) filaments
• thin filaments attached to dense bodies (like Z discs)
• not stripy
• does not contain sarcomeres

Question 12

What are the connective tissues of smooth muscle?

Answer 12

• Endomysium (covers muscle fibre)

Question 13

What is each muscle fibre enclosed with?

Answer 13

Sarcolemma (plasma membrane)

Question 14

What is the contractile unit inside muscle fibre?

Answer 14

Myofibril

Question 15

What is the structure of a myofibril?

Answer 15

• Inside myofibrils are myofilaments
• Myofilaments (actin; thin), (myosin; thick)
• Arranged into compartments (sarcomere)
• Z discs separate sarcomere and anchor thin filaments (boundaries)

Question 16

What is the structure of a sarcomere?

Answer 16

Z discs = separate sarcomeres
I band = thin filaments (actin)
A band = thick filaments (myosin + overlap of actin)
H zone = just myosin
M = anchors thick filaments (middle)

*I and H band move when muscle contracts (shortens)

Question 17

What are the components of a thin filament?

Answer 17

1. Actin
2. Tropomyosin - blocks active binding sites
3. Troponin - binds Ca2+ (changes shape to pull tropomyosin out the way to bind)

Question 18

What is the name for the process of muscle contraction?

Answer 18

Sliding Filament Theory

Question 19

What is the sliding filament theory?

Answer 19

1. Myosin head requires bound ATP to detach from actin
2. Hydrolysis of ATP to ADP + P, resets myosin head allowing it to bind to actin
3. Myosin head binds to actin and performs a power stroke
4. ADP + P are released from myosin head, myosin cannot detach until ATP attaches onto it
5. With ATP bound to myosin head it can detach from actin

Question 20

What does a muscle contraction require?

Answer 20

1. Acetylcholine (released from motor neuron)
2. Calcium (released from sarcoplasmic reticulum)
3. ATP (energy)
4. Action and myosin

Question 21

What are the components of a neuromuscular junction?

Answer 21

1. Synaptic bulb end
2. Synaptic vesicles
3. Motor end plate
4. Synaptic cleft
5. ACh receptors
6. Acetylcholinesterase (AChE)

Question 22

What is a synaptic bulb end?

Answer 22

Expanded end of the neuron.

Question 23

What are the synaptic vesicles?

Answer 23

Membrane-bound sacs filled with acetylcholine (ACh).

Question 24

What is the motor end plate?

Answer 24

Region of sarcolemma across synaptic knob that has fold and indentations to increases surface area.

Question 25

What is the synaptic cleft?

Answer 25

Narrow space separating the synaptic knob and motor end plate.

Question 26

What is the ACh receptors?

Answer 26

In the motor end plate that bind to ACh.

Question 27

What is Acetylcholinesterase (AChE)?

Answer 27

An enzyme in synaptic cleft that rapidly breaks down ACh.

Question 28

What is the process of a neuromuscular junction in regards to muscle contractions?

Answer 28

1. Nerve impulses cause increase in calcium
2. ACh is released from synaptic vesicle via synaptic cleft
3. ACh binds to ACh receptors (motor end plate)
4. Muscle action potential is produced
5. ACh is broken down

Question 29

What are the components of the triad?

Answer 29

Terminal cisterns on either side of a tubule.

• Tubule (brings action potential into interior muscle fibre)
• Terminal cisterns (release calcium from sarcoplasmic reticulum and trigger muscle contraction)

*Calcium is stored in sarcoplasmic reticulum