9: Muscle

Question 1

What is the primary function of muscle tissue?

Answer 1

To generate force for contraction = movement

Question 2

What are the 3 types of muscle cells?

Answer 2

Cardiac, skeletal, & smooth muscle

Question 3

Describe smooth muscle cells

Answer 3

• fusiform cells (long, individual cells)
• one nucleus per cell
• non-striated (cells arranged closely to form sheets)
• involuntary
• slow, wave-like contractions
• function : to propel substances or objects (e.g. food in small intestine; urine; a baby) along internal passageways; involuntary control

Question 4

Describe cardiac muscle cells

Answer 4

• branching cells
• 1-2 nuclei per cell
• striated (& branching)
• involuntary
• medium speed contractions
• function : as it contracts it propels blood into the circulation ;involuntary control

Question 5

Describe skeletal muscle cells

Answer 5

• long cylindrical cells
• many nuclei per cell (due to cells being so long)
• striated
• voluntary
• rapid contractions e.g. during exercise
  Function : voluntary movement; manipulation of the environment; facial movement; voluntary control

Question 6

What are the names for the following, when describing muscle tissue?
1. muscle cell
2. cytoplasm
3. cell membrane

Answer 6

1. fibres
2. sarcoplasm
3. sarcolemma

Question 7

What are the different types of skeletal muscle fibres?

Answer 7

Type I
* slow twitch; slow oxidative e.g. marathon runners
* slow conversion of ATP to ADP
* main storage fuel = IMTG (intramuscular triglycerides) : more ATP from fat cells than carbs but takes longer

Type II (IIa)
* fast twitch; fast oxidative glycolytic
* fast conversion of ATP to ADP
* storage fuel: creatine phosphate, glycogen

Type IIx (IIb)
* fast twitch x ; fast glycolytic e.g. when sprinting
* ^ quick conversion of ATP to ADP
* main storage fuel: creatine phosphate, glycogen

Question 8

What are the functions of the muscles?

Answer 8

• movement
• maintenance of posture and muscle tone
• heat production
• protects bones and internal organs
• movement of substances in the body (e.g. by smooth muscle cells)

Question 9

What is the sarcomere?

Answer 9

(a contractile units)
- consists of basic repeating units between two Z lines; comprises the functional unit of a muscle fibre
- they lie in series and their filaments have a parallel configuration within a given fibre
- sarcomere length determines the muscles functional properties

Question 10

Explain the sliding filament theory of muscle contraction (in skeletal muscle)

Answer 10

1. Active site exposure (of actin)
2. Cross bridges are formed (as myosin head binds to troponin)
3. Pivoting of myosin head
4. Cross bridge detachment (myosin head is released)
5. Reactivation of myosin

Question 11

Describe the process of smooth muscle contraction

Answer 11

1. actin & myosin are loosely arranged around the periphery of the cell, held in place by protein dense bodies
2. the arrangement of the fibres causes the cell to become globular when it contracts
3. myosin can slide along actin for long distances without encountering the end of a sarcomere
4. smooth muscle myosin has hinged heads all along its length