Heart Cycle, Pressure And Regulation

Question 1

Exercise capacity

Answer 1

Highest amount of oxygen a person can consume during maximal exercise of several minutes’ duration. Exercise capacity is the maximum amount of physical exertion (use of energy) that a patient can sustain.

Question 2

Ultrasound scan

Answer 2

Sonogram/echocardiogram
High frequency sound waves to create an image of a part inside the body. It can show the shape and movement of the heart valves, the size of the heart chambers and how they are working

Question 3

Wiggers Diagram

Answer 3

Cardiac cycle, change in left side of the heart (right side same but with lower pressure). Shows the cardiac events with aortic,ventricular, atrial pressure and ventricular volume.

• Volume decrease during ejection then stays at lowest point during isovolumic relaxation. Then it increase again during rapid inflow, slows during diastasis and increase again with atrial systole. It then stagnates at the highest point with isovolumic contraction.
• atrial pressure peak with a c v waves then slowly goes down. 0-8mmHg
• aortic pressure rise with ventricular contraction and ejection then decrease with ventricular relax and refill. Small peak with passive ventricular filling. 80-120mmHg
• ventricular pressure: rise with ventricular contraction and ejection, falls with relaxation and passive inflow then constant at low point during diastasis and atrial systole. 0-120mmHg

Question 4

Systole

Answer 4

Ventricular systole: period of contraction of the ventricles of the heart that occurs between the first and second heart sounds of the cardiac cycle. Systole causes the ejection of blood into the aorta and pulmonary trunk. Consists of isovolumetric contraction and ventricular ejection. It’s the : pumping.
Atrial systole: last event of ventricular diastole. represents the contraction of myocardium of the left and right atria. The atrioventricular valves (mitral and tricuspid valves) open and causes the contents of the atria to empty into the ventricles. The atrioventricular valves remain open while the aortic and pulmonary valves remain closed.

Question 5

Diastole

Answer 5

Ventricular diastole is the period during which the two ventricles are relaxing from the contortions/wringing of contraction, then dilating and filling; atrial diastole is the period during which the two atria likewise are relaxing under suction, dilating, and filling.
Ventricular diastole is isovolumetric relaxation, ventricular filling, diastasis, atrial contraction
Atrial diastole is all the time beside atrial systole

Question 6

Atrioventricular valves (AV valves)

Answer 6

Mitral valve : from left ventricle to left atria
Tricuspid valve : from right ventricle to right atria
Open during ventricular filling, diastasis and atrial contraction.

Question 7

Semilunar valves

Answer 7

Pulmonary valve: from right atria to pulmonary artery
Aortic valve : from left atria to aorta
Open during ventricular ejection (2nd phase systole)

Question 8

Cardiac events

Answer 8

Systole:

• Isovolumetric contraction early systole. AV valves close from rise in pressure: S1. The ventricles contract with no corresponding volume change (isovolumetrically). This short-lasting portion of the cardiac cycle takes place while all heart valves are closed. Max pressure reached
• ventricular ejection (ventricular systole); blood flows from the heart—to the lungs and to rest of body during ventricular ejection. Semilunar valves open ( pulmonary + aortic valves )

Diastole:

• Isovolumetric relaxation: the ventricles relax, ready to re-fill with blood in the next filling phase. Semilunar valves close at end of ejection stage: S2; blood flow stops. Blood flows from the vena cava and pulmonary veins into the right and left atria respectively. Volumes left in ventricles is end systolic volume (esv)
• Ventricular filling: Blood flows from the vena cava and pulmonary veins directly into the ventricles. The ventricles fill with blood at a steadily decreasing rate, until the pressure in the ventricles is equal to that in the veins.
• diastasis is the middle stage of diastole during the cycle of a heartbeat, where the initial passive filling of the heart’s ventricles has slowed, but before the atria contract to complete the active filling.
• Atrial contraction: atrial systole. Atria contract and with atrioventricular valves open, empty in ventricles: S4.
Blood moves across the Av valves into the ventricles. Ventricular filling mostly passive: before contraction, venous return. If diastolic filling reduced then atrial systole contribute more with sympathetic contraction ( exercise).
Ventricules now have their end diastolic volume (edv): 120ml. End diastolic pressure 8mmHg

Question 9

ACV waves

Answer 9

Seen on atrial pressure
a wave : end diastole, atrial contraction
c wave : early systole, tricuspid bulging
V wave : late systole, systolic filing of the atrium

Question 10

Pressure

Answer 10

P = R x CO

Question 11

Flow

Answer 11

F = Pressure diff / R

Question 12

Compliance

Answer 12

Difference in volume / difference in pressure
Relates to stiffness.

Indicated on pressure volume loop. Steep: low compliance

how easily a chamber of the heart or the lumen of a blood vessel expands when it is filled with a volume of blood

Question 13

Preload

Answer 13

The stretching of cardiac myocytes, sarcomere length, at the end of diastole
It is affected by venous return and pressure
Sarcomere length is approximated with ventricular volume and pressure
HR & Inotropy (contractibily myocardium) goes up -> preload goes down

Question 14

Afterload

Answer 14

Load against which the heart must contract to eject blood

Proportional to arterial pressure

Question 15

SAN

Answer 15

Sinotrial node

produce resting heartbeat. It does the firing. Can be stimulated by sympathetic and reduced by parasympathetic.

Question 16

AVN

Answer 16

Atrioventricular node
Does the conduction of SA node firing to bundle of HIS
Conduction can be slowed by parasympathetic

Question 17

Exercising

Answer 17

Muscle require and more metabolic by products need to be removed. By products : lactic acid from muscle fermentation (anaerobic respiration) and CO2 ( muscle respiration is oxydative)
For muscle to contract, need ATP (Adenosine Triphosphate.. ATP comes from phosphocreatine, glycolysis
& cellular respiration. Aerobic respiration is more efficient for ATP delivery but if respiratory / circulatory cant keep up then anaerobic respiration starts. Glycolysis when no oxygen
Glycolysis : glucose into ATP, glucose usually taken from muscle glycogen in muscle fibers
Glucose -> pyruvate, water, NADH
Pyruvate goes in Krebs cycle to be transformed in ATP if there is oxygen
If no oxygen pyruvate accumulates and become lactic acid -> pH drops -> muscle tissue more acidic -> anaerobic respiration : glucose break without oxygen -> lactic acid and ATP increase
Vasodilation in contracted muscle for increased blood flow. Vascular resistance drops. Cardiac output increase -> pressure increase
(Sympathetic) Vasoconstriction in other parts -> maintain pressure and blood flow
-> maintain resistance
-> shift blood to active muscles
-> venous return increase ( higher pressure helps blood return to heart) -> preload maintained -> cardiac output increase
Heart rate increase -> diastolic filling decrease -> sympathetic contraction increase -> atrial systole increase

Question 18

Heart sounds

Answer 18

S1: closing AV valves start of systole. Mitral then tricuspid
S2 : closing semilunar valves start of diastole. Aortic then pulmonary
S1 & S2 sudden block of flow
S3: diastole filling, heard in some people but abnormal if new
S4: sound of blood forced in ventricle atrial contraction

Question 19

Sympathetic

Answer 19

cardiac stimulation and vasoconstriction

Question 20

Parasympathetic

Answer 20

reduce SA nodal firing, slows AV nodal conduction

Question 21

Resting heart beat

Answer 21

about 90-100bpm

Question 22

Sarcomere

Answer 22

Basic contractile unit of muscle fiber

filaments: actin and myosin -> responsible for contraction

Question 23

Frank Starling Mechanism

Answer 23

relationship between stroke volume and end diastolic volume
The law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction, when all other factors remain constant.

Question 24

Tunica intima

Answer 24

innermost layer of vessels
artery: wavy, vein: smooth
endothelium: lining of lumen
basal lamina: collagen & elastic fiber to contract, connect to tunica media, permeable: exchange
LARGE arteries: internal elastic membrane in basal lamina

Question 25

Tunica media

Answer 25

middle layer of vessels smooth muscle, connective tissue: elastic fiber and collagen LARGE arteries: external elastic membrane separate tunica media and externa

Question 26

Vein >< Artery structure

Answer 26

veins can have valves -> act against gravity, no back flow in eg legs veins have a larger lumen compared to membrane or thinner membrane compared to artery tunica intima (innermost layer) of arteries are wavy tunica media of arteries is larger arteries tend to be more circular

Question 27

Tunica externa

Answer 27

connective tissue: elastic & collagen fibers | nervi vasorum: regulate vasodilation/ vasoconstriction

Question 28

Types of arteries

Answer 28

Elastic Largest, aorta and large branches Large tunica media with many elastic membrane/fibers with smooth muscles. Have lamina elastica interna (but not visible) and externa. Tunica externa thin compared to the rest Muscular multiple mm lamina elastica interna. Have vasa vasorum(small blood vessels that supply the walls of large blood vessels) Arteriole smallest there can be just 1 smooth muscle

Question 29

Types of capillaries

Answer 29

continuous endothelium (inner layer) and lamina basalis (outer layer) fenestrated: fenestrae on endothelial cells sinusoid: fenestrated without lamina basalis continous less easy to pass and sinusoid most easy

Question 30

Metarteriole

Answer 30

terminal arteriole in capillary network, it connect the network to the arteriole

Question 31

Muscle pump

Answer 31

help blood move to heart with pressure difference

Question 32

Capillaries

Answer 32

connect arteries and veins -> oxygen, nutrients and waste exchange

Question 33

Vein >< Artery function

Answer 33

Arteries: blood away from the heart, higher pressure compared to veins -> thicker walls oxygenated blood to rest of the body pulmonary artery brings deoxygenated blood to lungs veins: blood to heart, de-oxygenated blood pulmonary veins are the veins that transfer oxygenated blood from the lungs to the heart

Question 34

Chordae tendinae and papillary muscle

Answer 34

Chordae tendinae connects the tricuspid and mitral valve to the papillary muscle that are on the ventricular walls ventricles contract -> papillary muscle contract -> chordae tendinae pulled -> valves close -> no blood back to atria

Question 35

Blood pressure

Answer 35

120/80 mmHg systolic/diastolic highest is systolic, lowest is diastolic if a lot higher heart is pumping too hard age makes vessel less compliant so it goes up

Question 36

Pressure volume loop

Answer 36

x axis: volume in ml, loop from 50 to 120 y axis: pressure in mmHG, from 5 to 120 Mitral valves open: 5mmHg, 50ml end of isovolumetric relaxation, start of distolic filling Distolic filling: pressure does not increase but volume does until 120ml (slight slope up in pressure towards the end) Mitral valves close -> EDV: isovolumetric contraction volume does not change but pressure increase from 10 to 80mmHg Aortic valves open Systolic ejection: curve make pressure increase to 120mmHg and volume decrease back to 50ml Aortic valves close -> ESV: isovolumetric relaxation pressure goes down from 100mmHg back to 5

Question 37

EDV | ESV

Answer 37

End diastolic volume ventricles volume after diastole End systolic volume ventricles volume after systole

Question 38

Venous Return

Answer 38

VR | flow back to the heart, should equal the cardiac output

Question 39

Stroke volume

Answer 39

amount of blood pumped by the ventricles | EDV - ESV

Question 40

Perfusion

Answer 40

passage of blood in circulatory system, arterial pressure controls it

Question 41

Regulation pressure

Answer 41

baroreceptors: pressure sensors in veins and arteries -> send to CNS -> baroreceptor reflex-> pressure goes down -> CO goes up and vasoconstriction hormones: angiotensin II, aldosterone, vasopressin blood volume goes up -> CO, pressure goes up

Question 42

Exercise red face

Answer 42

Exercise -> heat goes up -> thermoreceptors (hypothalamus) -> sympathetic goes down -> vasodilation -> blood flow goes up -> heat goes down