cardiovascular system

Question 1

what and where is the heart?

Answer 1

• large organ in the centre of thoracic cavity

Question 2

what kind of structure does the heart have?

Answer 2

• upside down structure as the base is at the top and the apex is at the bottom

Question 3

what is the heart surrounded by? why is this important?

Answer 3

• fibrous sac called pericardium which has fluid that provides lubrication
• also anchors heart against diaphragm and spine

Question 4

what are the atriums?

Answer 4

• top receiving chambers

Question 5

what are the ventricles?

Answer 5

• bottom part that contracts with force to pump blood around

Question 6

what is the biggest vein in the body?

Answer 6

• vena cava

Question 7

what happens when blood arrives via vena cava?

Answer 7

• reaches right atrium which contracts slightly to push blood
• via tricuspid valve to right ventricle

Question 8

what does the right ventricle do after it receives blood?

Answer 8

• pushes blood through pulmonary valve into pulmonary arteries

Question 9

what happens after the blood has exited via pulmonary arteries and gone round the lungs?

Answer 9

• comes back via pulmonary veins into left atrium which contracts to push blood through mitral valve to left ventricle

Question 10

what does the left ventricle do with the blood?

Answer 10

• pushes the blood through aortic valve into aorta

Question 11

what are the atrioventricular valves?

Answer 11

• separate atrium and ventricle; mitral and tricuspid valves are thick to allow blood to passively pass through

Question 12

what are the semi- lunar valves?

Answer 12

• pulmonary and aortic valve
• control release of blood as open to allow blood through and close to ensure no backflow

Question 13

what is cardiac muscle?

Answer 13

• similar to skeletal muscle in terms of its structure but it operates similarly to smooth muscle as act involuntary

Question 14

what are cardiac muscles controlled by?

Answer 14

• autonomic nervous system

Question 15

what are the properties of cardiac muscle?

Answer 15

• contains striated muscle fibres
• less and smaller sarcoplasmic reticulum
• highly oxidative

Question 16

what is the gap junction?

Answer 16

• electrical and chemical connection between fibres; allows an electrical signal to originate from specialised part of the heart and propagate from fibre in organised pattern

Question 17

what does contraction depend on?

Answer 17

• depolarisation
• extracellular calcium ions to activate the receptors to allow more calcium ions in

Question 18

can tetanic contraction occur in cardiac muscles?

Answer 18

• no because action potentials is almost as long as contraction period
• muscle fibres in refractory period
• always relaxes before another action potential

Question 19

what is the sinoatrial node?

Answer 19

• can initiate cardiac contraction in absence of any external control as it is myogenic

Question 20

why do SA node cells initiate the action potential?

Answer 20

• due to unstable membrane potential that is continuously drifting towards threshold

Question 21

what does sympathetic stimulation to SA node cause?

Answer 21

• increase in slope of drift due to increase of permeability of Na+ current

Question 22

what does parasympathetic stimulation to SA node cause?

Answer 22

• decrease in slope of drift due to overall decrease of inward current
• and hyperpolarisation of membrane due to increased K+ permeability

Question 23

what does firing rate depend on?

Answer 23

• initial value of membrane potential
• on the slope of drift towards threshold

Question 24

how does stimulation spread in atria?

Answer 24

• from fibre to fibre via gap junctions

Question 25

what network allows ventricular stimulation to spread?

Answer 25

- network of conduits - begins at atrioventricular node and terminates at cardiac muscle fibres via purknje fibres

Question 26

what is the first step of propagation of electrical signal?

Answer 26

- stimulus spreads through muscle fibres and stimulate both atria almost simultaneously

Question 27

what happens after atria contract?

Answer 27

- AV node delays the electrical signal to allow atria to empty before contraction

Question 28

where does signal travel down?

Answer 28

- interventricular septum via two bundle branches

Question 29

what happens after the impulse travels down septum?

Answer 29

- ventricles begin to contract as stimulus spreads upwards - depolarising muscle fibres via purknje fibres

Question 30

what is the tricuspid valve?

Answer 30

- separates right atrium and right ventricle

Question 31

when does tricuspid valve open?

Answer 31

- opens when right atrial pressure is higher than ventricular pressure

Question 32

when does tricuspid valve close?

Answer 32

- when right ventricular pressure is higher than right atrial pressure

Question 33

what is the mitral valve?

Answer 33

- separates the left atrium and left ventricle

Question 34

when does mitral valve open?

Answer 34

- when left atrial pressure is higher than left ventricular pressure

Question 35

when does mitral valve close?

Answer 35

- when left ventricular pressure is greater than left atrial

Question 36

what is the pulmonary valve?

Answer 36

- separates right ventricle and pulmonary artery

Question 37

when does pulmonary valve open?

Answer 37

- when right ventricular pressure is greater than pulmonary artery pressure

Question 38

when does pulmonary valve close?

Answer 38

- when pulmonary artery pressure is greater than right ventricular pressure

Question 39

what is the aortic valve?

Answer 39

- separates left ventricle and aorta

Question 40

when does aortic valve open?

Answer 40

- when left ventricular pressure is greater than aortic pressure

Question 41

when does aortic valve close?

Answer 41

- when aortic pressure is larger than left ventricular pressure

Question 42

what happens to the valves during systole?

Answer 42

- aortic and pulmonary valves open meanwhile AV valves stay closed

Question 43

what is the electrocardiogram?

Answer 43

- graphical representation of the electrical activity across heart

Question 44

what do waves and troughs represent?

Answer 44

- waves= depolarization - troughs= repolarization

Question 45

is there a lag in the cardiac cycle?

Answer 45

- lag between depolarization of myocardiocytes and actual contraction of muscles

Question 46

what does P wave represent?

Answer 46

- atria depolarization

Question 47

what is the QRS complex?

Answer 47

- represents ventricular depolarization which causes ventricles to contract

Question 48

what does T wave represent?

Answer 48

- time of ventricular repolarization and subsequent relaxation

Question 49

what is the Frank- starling mechanism?

Answer 49

- heart will pump all the blood that returns to it by way of the veins