muscles

Question 1

functions of muscular system

Answer 1

-body movement
-maintenance of posture
-respiration
-production of body heat
-communication
-control of blood flow into vessels

Question 2

which filaments are thick and which are thin?

Answer 2

thin filaments = actin
thick filaments = myosin

Question 3

overview of muscle contraction

Answer 3

1. stimulus arrives to the muscle in the form of an action potential
2. excitation- action potential causes release of Ach into post synaptic cleft
3. calcium released from sarcoplasmic reticulum stores, trigger for contraction
4. contraction cycle begins, calcium binds
5. sarcomere shortening. heads bind to actin molecules. ATP required for shortening
6. generation of muscle tension

Question 4

the role of calcium in muscle contraction

Answer 4

calcium ions cause exposure of myosin binding sites on actin
they bind to the troponin complex, which activates myosin binding sites to open
calcium is a ‘switch’ for muscle contraction

Question 5

steps that end a muscle contraction

Answer 5

1. Ach is broken down by AchE, ending action potential generation
2. sarcoplasmic reticulum reabsorbs calcium ions
3. active sites are covered and cross bridge formation ends (since there is no calcium so tropomyosin returns to its normal position)
4. contraction ends
5. muscle relaxation occurs, returns passively to resting length

Question 6

isotonic contraction vs isometric contraction

Answer 6

isotonic -= muscle length SHORTENS
isometric = tension in muscle, NO change in length

Question 7

slow twitch vs fast twitch fibres

Answer 7

slow twitch = less powerful. fewer myofibrils, more mitochondria, and myoglobin
fast twitch = more powerful. more myofibrils, less mitochondria.

Question 8

what is a motor unit?

Answer 8

a somatic motor neuron + muscle fibres.
- one axon terminal on each fibre
- each motor unit has terminals on many fibres

Question 9

layers of smooth muscle

Answer 9

• submucosa
• mucosa
• longitudinal layer
• circular layer

Question 10

effects of exercise on muscle (2)

Answer 10

-increased endurance
-increased strength

Question 11

how does exercise increase muscle endurance?

Answer 11

• increased size and number of mitochondria
• increased number of blood capillaries supplying muscle (hence more oxygen and nutrients, more efficient waste removal)
• increased amount of myoglobin in muscle tissue

Question 12

how does exercise increased muscle strength?

Answer 12

• increased size of muscle fibers (more myofibrils but same amount of muscle fibres)
• increased neural excitation of muscle fibres

Question 13

what is the process of losing muscle?

Answer 13

sarcopenia

Question 14

effect of exercise on bone

Answer 14

improved bone mineral density

Question 15

how does exercise affect structure of bone?

Answer 15

WOLF’S LAW
-bone reacts to stresses put on it

Question 16

what is the process of losing bone?

Answer 16

osteosarcopenia

Question 17

how does exercise improve bone mineral density?

Answer 17

1. compression on the bone increases bone formation
2. osteocytes act as mechano-sensors by responding to compression
3. fluid that surrounds osteocytes and within canaliculi is compressed
4. nitric oxide is produced by osteocyte
5. stimulates the production of a factor that triggers osteoblasts to form collagen and bone mineral