Excitable Cells and muscles

Question 1

Typical concentrations of Na, k and Cl inside the cell

Answer 1

Na = 15mM
K = 150mM
Cl = 5mM

Question 2

Typical concentrations of Na, K and Cl outside the cell

Answer 2

Na = 145 mM
K = 5mM
Cl = 100mM

Question 3

Kinetics of voltage gated sodium channels

Answer 3

Rapid opening triggered at threshold

Slow closing triggered at threshold

Question 4

Kinetics of voltage gated potassium channels

Answer 4

Delayed opening triggered at threshold

Question 5

Movement of ions at resting state

Answer 5

2 K+ in
3 Na+ out
Via sodium-potassium exchange pump
ATP used to do so

Question 6

Describe ligand gated ion channels

Answer 6

Neurotransmitters bind
Channel opens
Ions flow in

Question 7

Describe G protein coupled receptors

Answer 7

Neurotransmitter binds
G protein activated
G protein subunits or intracellular messengers modulate ion channels
ion channel opens ions flow across membrane

Protein acts as a regulator

Question 8

Sources of ATP in muscle

Answer 8

1. Dephosphorylation of phosphocreatine
2. Glycolysis
3. Oxidation of glucose/glycogen
4. Oxidation of free fatty acids

Question 9

Titanic fusion frequency

Answer 9

Frequency of action potential delivery to enable smooth muscle contraction

Question 10

What does RT stand for in a length tension curve

Answer 10

Resting tension

Question 11

What does TT stand for in a length tension curve

Answer 11

Total tension

Question 12

What does AT stand for in a length tension curve

Answer 12

Active tension

Question 13

Describe cardiac muscle stretch resistance

Answer 13

• Has higher resistance to stretch then skeletal muscle

- High abundance of connective tissue prevents muscle rupture and over stretching

Question 14

Frank-Starling law

Answer 14

• Stretching occurs at times of increased venous return
• force of contraction is increased by stretch and by sympathetic contraction
• helps heart pump whatever volume of blood it receives

Important mechanism

Question 15

Chronotropy

Answer 15

Rate of contraction

Question 16

Inotropy

Answer 16

Force of contraction

Question 17

Luistropy

Answer 17

Ability to relax

Question 18

Affect of epinerphrine and norepinephrine on cardiac excitation contraction

Answer 18

Bind to andonergic receptors that set of signalling pathways in the cell that allow calcium to be pumped back into the cell and stimulate Ryr

Question 19

What are important proteins in the myofilaments of cardiac muscle

Answer 19

Scaffolding proteins
Elastic protein Titin: prevents overstretching and may also serve as signalling role as a stretch sensor. When calcium levels go down you get passive relaxation that titin aids with

Question 20

Where is smooth muscle located

Answer 20

Internal organs
Walls of blood vessels
Around hollow organs
Layers around respiratory, circulatory, digestive and reproductive tracts

Question 21

What are the functions of smooth muscle

Answer 21

Move food, urine and reproductive tract secretions
Control diameter of respiratory pathways
Regulate diameter of blood vessels

Question 22

What is the structure of smooth muscle

Answer 22

Spindle Shaped 
Single nucleus 
Not strained 
Smooth muscle fibres often embedded in matrix of connective tissue and arranged in parallel with one another 
100-300 um long 
2.5 um wide

Question 23

What is multi unit smooth muscle

Answer 23

Each individual cell responds on its own. Needs to receive neurotransmitter

Question 24

What is single unit smooth muscle

Answer 24

Gaps junctions = propagation.

Question 25

What is phasic contraction

Answer 25

Sometimes contracted sometimes relaxes

Question 26

What is tonic contraction

Answer 26

Always partially contracted