Exercise Phys 1: Cardiovascular system and adaptations to exercise

Question 1

Nernst Equation? What does it calculate?

Answer 1

[Eion] = RT/zF x ln ([intracellular]/[extracellular])

calculates theoretical resting membrane potential for a specific ion with known intra and extracellular concentrations

Question 2

Increasing the following currents will have what effect on membrane potential? What effect on action potential?

Ca2+
K+
Na+

Answer 2

Ca2+ open -> increase in influx -> more positive membrane potential -> sustained depolarisation

K+ open -> increase in efflux -> more negative membrane potential -> hyperpolarise -> shorter AP duration

Na+ open -> increase in flux -> more positive membrane potential -> rapid but short depolarisation (Na+ channels inactivate)

Question 3

How long (on average) is the cardiac cycle at 60BPM

Answer 3

~ 1 second in duration

Question 4

What is stroke volume? If 100ml is in a ventricle and 40ml remains, what is the SV?

Answer 4

Volume of blood ejected from the heart during each cardiac cycle

100ml-40ml = 60ml = SV

Question 5

Difference between cardiac and skeletal activity

Answer 5

Cardiac - involuntary, continuous rhythmic contraction

Skeletal - voluntary, contracts when required for movement; excitation-contraction coupling

Question 6

Difference in appearance and structure between cardiac and skeletal muscle?

Answer 6

Cardiac - shorter, many branches. Intercalated discs between cells allow rapid spread of depolarisation

Skeletal - fibres long and cylindrical, u.branched. Z-fibres align (muscle is striated)

Question 7

DIfference in metabolism between cardiac and skeletal muscle?

Answer 7

Cardiac - mostly aerobic (Free Fatty Acids (FFA) primary fuel) will use anaerobic respiration preferentially during ischaemia

Skeletal - Anaerobic for short bursts of activity (Type II), aerobic for longer duration exercise (type I)

Question 8

What electrical event does each section of an electrocardiograph correspond to?

Answer 8

P wave = depolarisation of the atria + contraction (systole)

QRS complex = depolarisation of the ventricles + contraction (systole)

T Wave = repolarisation of the ventricles + relaxation

Question 9

Brief overview of pathway of cardiac cycle

Answer 9

SA node -> atrial AP -> AV node (delay) -> bundle of His (conducting system) -> ventricular AP

Question 10

What effects do parasympathetic and sympathetic activity have on the heart

Answer 10

At rest - parasympathetic activity via vagal nerve lowers heart rate (inhibited in early exercise)

With circulating NA/adrenaline - sympathetic activity via sympathetic nerve

Question 11

Equation for vascular resistance?

Answer 11

n x L/r^4

n = viscosity of blood
L = length of vessel
r = radius

Question 12

What controls vascular smooth muscle contraction/relaxtion and how?

Answer 12

Vascular smooth muscle rests at a higher resting potential (-40mv) meaning it is more depolarised and contracted than other muscle types at rest

This means they can contract/relax based on the demands of the tissue beyond