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Flashcards in Cells and Tissues Deck (88)
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1

What does the force of muscle contraction depend on?

The number of cross bridges- compositions of motor unit, frequency of potentials, length tension relationship

2

What does and isometric contraction and isotonic contraction mean?

Isometric- same length of sarcomere so elastic elements extend, Isotonic- sarcomere shortens

3

How are graded muscle contractions achieved?

Changing the number and type of motor units that are activated

4

What is tetanus?

Sustained contraction with no relaxation due to large number of potentials

5

Why does length tension affect the force of contraction?

If the sarcomere is too short there is little shortening, if too long there is minimal cross bridge formation

6

What is energy stored in during rest?

High energy bonds in phosphocreatine- converted to creatine to release ATP

7

Where does ATP come from during exercise?

Initially the cytoplasm, then creatine, followed by glycolysis then oxidative phosphorylation,

8

What causes fatigue?

A reduction in sources of ATP

9

What sort of movement is Glycolytic (white) suited for?

Relies on anaerobic glycolysis so performs fast with high power contractions

10

What are some features of white muscle fibres?

Colour- little myoglobin, contain few mitochondria, contain glycogen

11

What exercise is oxidative (red) muscle fibres suited for?

Slow sustained activity

12

What are some features of red muscle fibres?

High myoglobin, surrounded by capillaries, lots of mitochondria

13

What is the function of myoglobin and how does it achieve this?

Myoglobin assists aerobic metabolism, by having a greater affinity for oxygen than haemoglobin for the muscle.

14

Where is smooth muscle found in the body?

GI tract, Uterus, Bladder, Eye, Blood vessels

15

How is the structure in smooth muscle different to skeletal muscle?

In smooth muscle there is less myosin, and there are no sarcomeres

16

What are key features of smooth muscle?

Small non-striated, spindle-shaper cells with single nucleus

17

Why can smooth muscles contract when stretched?

The myosin filaments are longer and covered in heads so can maintain enough overlap for optimal tension

18

Why are smooth muscles resistant to fatigue?

ATP mostly from oxidative phosphorylation and uses less energy then skeletal

19

What ion causes contraction in smooth muscle?

Calcium rise

20

How does calcium cause contraction in smooth muscle cells?

Calcium enters the muscle cell and binds to calmodulin activating myosin light chain kinase, which phosphorylates myosin which controls contraction

21

What causes Ca2+ to rise in smooth muscle?

External entry by voltage and ligand gated ion channels and some from the SR

22

What does myogenic mean?

No external stimuli needed for contraction, spontaneous

23

What are the two ways myogenic smooth muscle reaches threshold?

Pacemakers potentials oscillating membrane potentials that regularly reach threshold, or slow cyclic waves which gradually rise until threshold

24

How do multiunit smooth muscle cells differ?

Multiunit cells each have a terminal ending on every cell for fine control e.g iris

25

How do single unit cells spread excitation?

Gap junctions between cells

26

What neurotransmitter do sympathetic nerves release?

Noradrenaline

27

How can noradrenaline cause inhibition or excitation in smooth muscle?

Different receptors, alpha receptors cause excitation beta receptors cause inhibition

28

What causes smooth muscle relaxation?

Decrease in sarcoplasmic calcium using pumps and exchangers

29

What ions is intracellular high and low in?

High K+, low Na+, v low Ca2-,

30

What ions is extracellular fluid? high and low in

low Ca2+, low K+, high Na+