Case 4 Sem 2

Question 1

Right heart pumps blood into

Answer 1

Lungs

Question 2

Left heart pumps blood into

Answer 2

Peripheral organs

Question 3

Atrium

Answer 3

Weak primer pump for ventricle (moves blood into ventricle)

Question 4

Ventricles

Answer 4

Main pumping force propelling blood

Question 5

Right ventricle

Answer 5

Pulmonary circulation

Question 6

Left ventricle

Answer 6

Peripheral circulation

Question 7

Atrial muscle

Answer 7

Contracts strongly like skeletal
Longer contraction than skeletal

Question 8

Ventricular muscle

Answer 8

Contacts strongly like skeletal
Longer contraction than skeletal

Question 9

Specialised excitatory and conductive muscle fibres

Answer 9

Contract weakly because few contractile fibrils
Exhibit autonomic rhythmical electrical discharge in form of action potentials or conduction of action potentials through the heart
(Excitatory system that controls rhythmical beating of the heart)

Question 10

Syncytium

Answer 10

Single cell/cytoplasmic mass containing several nuclei formed by fusion of cells/division of nuclei

Question 11

Intercalated discs

Answer 11

Cell membranes that separate individual cardiac muscle cells (cardiomyocytes)

Question 12

Cardiac muscle fibres

Answer 12

Many individual cells connected in series, parallel to each other

Question 13

Gap junctions

Answer 13

At each intercalated disc
Permeable communicating junctions that form where cell membranes of different cardiomyocytes fuse

Question 14

Gap junctions and free diffusion of ions

Answer 14

Gap junctions allow total free diffusion of ions therefore ions move with ease in intercellular fluid along longitudinal axis of cardiac muscle fibres, so action potential can travel from one cardiac muscle cell to the next past the intercalated disc
So when one of the cardiac cells are excited, action potential spreads to all of them, spreading from cell to cell through latticework interconnections

Question 15

Sodium potassium pump

Answer 15

Pumps out 3 sodium ions for ever 2 potassium ions it pumps in with aid of ATP

Question 16

sodium ions diffuse in through membrane

Answer 16

And potassium ions diffuse out of the neuron (potassium ions diffuse more rapidly than sodium ions going in - electrochemical gradient)

Question 17

M gate

Answer 17

Positive voltage sensor detects voltage of positive ions on outside of neuron membrane
As potassium ions diffuse out, Increase in positive voltage (presence of K and Na) on outside of neuron detected by m gate
Once reached a certain voltage, m gate rapidly opens, allowing for influx of positive ions for generation of action potential
When m gate open, channel is activated

Question 18

Depolarisation

Answer 18

Ion selectivity filter selects sodium ions, leading to influx of sodium ions
Depolarisation causes slow closing of h gate and channel becomes inactivated

Question 19

Repolaristaion

Answer 19

M gate detects decrease in positive voltage on outside of membrane (decreased sodium ions)
M gate opens again, this time potassium ions selected by ion selectivity filter, so outflow of potassium ions from inside the neuron
ATP driven sodium potassium pump brings about resting potential, h gate ions and channel reactivated

Question 20

Voltage gated ion channels

Answer 20

6 alpha helical transmembrane proteins

Question 21

S4

Answer 21

Positive voltage sensor (m gate)

Question 22

S5-S6 loop

Answer 22

Pore forming loop allows for selectivity of specific ions

Question 23

Action potential

Answer 23

The change in electrical potential associated with passage of an impulse along membrane of a muscle /nerve cell

Question 24

Action potential in ventricular muscle cell fibre

Answer 24

105 millivolts
Intracellular potential rises from negative value (-85 millivolts) between beets to slightly positive value (+20 millivolts) during each beat
After initial spike, membrane remains depolarised for 0.2-0.3 seconds (plateau)
At end of plateau, membrane depolarises abruptlly
Presence of plateau in action potential causes ventricular contraction to last longer in cardiac muscle than skeletal

Question 25

Phases of cardiac muscle action potential

Answer 25

Phase 0: rapid depolarisation
Phase 1: initial rapid depolarisation
Phase 2: a plateau (normal refractory period)
Phase 3: slow depolarisation process
Phase 4: return to resting membrane potential