movement

Question 1

function of muscles

Answer 1

• movement
• thermoregulation
• energy metabolism + storage
• appetite regulation
• drug storage
• endocrine functions

Question 2

skeletal muscles

Answer 2

Attached to skeleton
Contract - pull on bones and cause them to move
Most common type
We control consciously

Question 3

Cardiac muscles (Myocardium)

Answer 3

• Forms the heart
• Responsible for pumping blood
• Involuntary movement

Question 4

Smooth muscle

Answer 4

• Located in tissues
• Responsible for controlling the diameter of certain structures and peristalsis
• Involuntary movement

Question 5

muscles in general are…

Answer 5

• Electrically excitable
• Contracts actively - requires energy
• Relaxes passively
• Elastic
• Extensible

Question 6

Characteristics of muscles

Answer 6

75% water
20% protein - contract
5% carbohydrate and fat - energy stores, active process of muscle contraction

Question 7

Men have more skeletal muscle than women?

Answer 7

true
Gender differences are greater in the upper body than in the lower body

Question 8

muscle loss due to age

Answer 8

Skeletal muscle starts to decrease in the third decade but a noticeable change does not occur until the end of thefifth decade
Most loss is in the lower body

Question 9

Contractions (general)

Answer 9

Chemical energy is transformed into mechanical energy
ATP is converted

Question 10

muscle fibres contain…

Answer 10

myosin (thick) - has heads that project towards actin, cause it to move

actin (thin) - binding sites for myosin heads

Question 11

filament arrangement in skeletal and cardiac muscle

Answer 11

regular, parallel pattern

Question 12

filament arrangement in smooth muscle

Answer 12

random

Question 13

sacromeres

Answer 13

myosin and actin are organsied into sacromeres

Question 14

muscle contraction

Answer 14

1. myosin heads link to actin to form cross-bridges
2. The myosin heads cycle (rotate) towards the centre of the sarcomere (connection to actin is broken)
3. Muscle contracts

Question 15

muscle relaxation in skeletal muscle

Answer 15

1. Tropomyosin blocks the binding sites on actin and prevents cross-bridge formation
2. Electrical excitation of the muscle cell releases calcium from calcium stores in SR
3. Calcium binds to troponin and moves the tropomyosin out of the way to allow cross-bridge formation
4. When electrical excitation finishes, calcium pumped back into the SR and tropomyosin once again blocking the binding sites

Question 16

T-tubules

Answer 16

brings action potentials into interior of muscle fibre

Question 17

process of contraction is the same in skeletal and cardiac muscle?

Answer 17

true

Question 18

Cross-striations in cardiac muscles

Answer 18

• less distinct because there are many mitochondria and many lipid and glycogen droplets around the cells
• muscles cells often branch at acute angles and are electrically connected to each other

Question 19

skeletal muscle cells

Answer 19

individual cells are electrically isolated, therefore we have more control as to which cells contract and which don’t

Question 20

ATP in cycle

Answer 20

used twice
1. when the cross bridge rotates
2. when the myosin head returns to its resting point (i.e. breaking the cross bridge)

Question 21

ATP can be produced in…

Answer 21

cytoplasm - anaerobic met (fast/inefficient)
mitochondria - aerobic met (slower/more efficient)

Question 22

smooth muscles are found in…

Answer 22

The walls of hollow organs
The walls of blood vessel
In airways
The eye
Skin

Question 23

smooth muscles can be controlled by…

Answer 23

• Hormones
• Neural stimulation from the ANS
• Change in pH in muscle - change in diameter
• Lack of oxygen - diameter or blood vessel
• Stretching the muscles

Question 24

Ca2+ role in smooth muscles

Answer 24

Uses calcium from both inside and outside the cell
Calcium binds to calmodulin (protein) that initiates contraction

Question 25

speed of ATP use and replacement determines...

Answer 25

how quickly muscle cells contract

Question 26

Type 1/slow twitch/red

Answer 26

* Contract **slowly** but fatigue slowly * Can't generate that much power * Supplied by nerves that activate them **first** during muscle contraction * Use **aerobic** metabolism * Lots of capacity to deliver oxygen to cells * Contain **myoglobin** that transport oxygen to mitochondria

Question 27

Type 2/fast twitch/white

Answer 27

* Much **quicker** but fatigue quickly * Generate lots of **power** * Use **anaerobic** metabolism * **No myoglobin**

Question 28

We increase the force of a muscle by...

Answer 28

activating more motor units simultaneously

Question 29

power of contraction

Answer 29

Change power of contraction by changing the number of motor unit used - control tension

Question 30

Small motor units

Answer 30

Few fibres innervated by a single nerve * Generate little tension * Enable fine control * Are fatigue resistant

Question 31

Large motor units

Answer 31

* Generate much more tension but figure quickly * Less fine control

Question 32

Twitch

Answer 32

One action potential in a motor neuron produce one contraction

Question 33

Summation

Answer 33

1. Latent period - action potential is being propagated along the membrane and Ca2+ ions released from SR 2. Contraction phase - period of cross bridge formation 3. Relaxation phase - Ca is pumped back into the SR, and cross bridge cycling stops

Question 34

If a muscle cell is stimulated while a previous twitch is occurring...

Answer 34

the second twitch will be stronger

Question 35

The tension produced in skeletal muscle is a function of

Answer 35

* The frequency of neural stimulation and * The number of motor neurons (i.e. number of motor units) involved

Question 36

Fast twitch fibres

Answer 36

possess **smaller neuromuscular junctions** (NMJs), which may facilitate efficiency and speed of neurotransmission.

Question 37

Slow twitch fibres

Answer 37

possess NMJs with larger surface area which may facilitate sustained stimulation