Chapter 20

Question 1

the functions of cardiovascular system

Answer 1

1. transport gas, nutrients, hormones, & metabolic wastes
2. regulation of pH and ion composition of interstitial fluid
   (neutralizes lactic acid, controls Ca++ and K+ concentrations)
3. restriction of fluid loss at injury sites
4. defence against toxins & pathogens
5. stablization of body temperature

components of cardiovascular system
- blood: transport medium
- heart: muscular pump that moves blood around the body
- system of tubes/ vessles: arteries, veins, capillaries

Question 2

two types of blood vessles arragned in two circuits:

Answer 2

1. pulmonary: to & from the lungs
2. systemic: to & from the rest of the body

Question 3

where is the heart located in?

Answer 3

the heart is located in the mediastrium in the thoracic cavity, within the pericardial cavity surrounded by pericardial fluid

Question 4

what is pericardium

Answer 4

the pericardium is composed of 2 parts. a tough outer fibrous layer lined by a delicate serous membrane (visceral & parietal)
- the fibrous pericardium is a very dense and non-flexible connective tissue that helps protect and anchor the heart

Question 5

what are the 2 layers of serous pericardium

Answer 5

1. visceral pericardium - also called epixardium
2. parietal pericardium - lines the inner surface of the pericadial sac

• location and function of pericardial fluid: 15-50mL provides lubrication between parietal pericardium & visceral pericardium
• the epicardium (visceral pericardium) = visceral mesothelium (simple, squamous epithelium) + areolar tissue

the parietal mesothelium (epithelial part of the parietal pericardium)

Question 6

The layers of cardiac tissue

Answer 6

1 pericardium: a loosely fitting connective tissue sac that surrounds the heart. the pericardial cavity contains a small amount of lubricating serous fluid, that allows the heart glide smoothly against the pericardium
- areolar tissue
- mesothelium

2 myocardium: the heart’s muscular layer
- cardiac muscle

3 endocardium: a layer of imple squamous epithelial tissue that intimately covers the inner chambers of hte heart (atrium and ventricles)
- areolar tissue
- endothelium

Question 7

Cardiac Muscle Tissue

Answer 7

cardiac muscle, lke skeletal muscle, is striated. Unlike skeletal muscle, its fibers are shorter, they branch and they have only on e(usually centrally located) nuleus.
- mitochondria account of r25 % of cellular volume
- cardiac muscle cells connect to & communicate with neighboring cells forming 2 funtional synctiums (atrial & ventricular) through gap junctions in intercollated discs
- all or nothing principles

Question 8

chambers of the heart: the atria

Answer 8

right and left atria
1) right atrium reived blood from:
- superior vena cava: draws from head & upper limbs
- inferior vena cava: draws from trunk & lower limbs
- coronary sinus: from cardiac veins

2) left atrium receives blood from left & right pulmonary veins - draw from the lungs

Question 9

the chambers of the heart: ventricles

Answer 9

right and left ventricles:
1) right ventricle pumps blood into: the lungs via the right & elft pulmonary arteries
2) left ventricle pumps blood into: the body via the aorta

Question 10

do the left & right ventricles hold the same volume?

Answer 10

left

Question 11

how much more presusre can the left ventricle produce compared to the right?

Answer 11

left has way more pressure tho the same amount of blood it has

Question 12

what are the heart valves made of

Answer 12

= flaps of dense connective tissue that act as one way valves
i.e. blood can only flow in one direction

two atrioventricular valves:
tricuspid - right AV valve
biscuspid (mitral) - left AV valve

two semilunar valve
between left ventricle and aorta
between right ventricle and pulmonary arteries

Question 13

what determines the flow of blood in the heart?

Answer 13

changed in pressure detmine the flow of blood in the heart and cause the valves to open and close. blood moves along a pressure gradient (high to low).

Question 14

what happens when opening/ clowing the AV valves

Answer 14

opening the AV valves:
1) blood returning to the heart travels through the atria and force the AV valves open
2) the atria contact forcing addition blood into the ventricles

closing the AV valves
1) the ventricles contract forcing blood against the AV valves
2) AV valves close (first heart sound)
3) papillary muscle contract to stabilize the valves

Question 15

Opening the Semilunar valves

Answer 15

as ventricle conttract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open

Question 16

closing the semilunar valves (second heart sound)

Answer 16

as ventricles relax and intraventricular pressure falls, blood flows back from arterises, filling the cusps of semilunar vavles and forcing them to close

Question 17

types of AV and SL

Answer 17

1. left AV valve (biscuspid, mitrall) - between left atrium and left ventricle)
2. right AV valve 9tricuspid) - between right atrium and right ventricle
3. aortic semilunar valve - at exit of left ventricle
4. pulmonary semilunar valve - at exit of right ventricle

Question 18

how the stenotic and insufficient valves are different from normal valves

Answer 18

normal valves result in: normal flow, no regurgitation

stenoitc valves result in: reduced blood flow
insufficient valves (fairly common) result in: reduced blood output due to regurgitation. If it folds backward it is called “prolapsed”

Question 19

what is the cardiac cycle

Answer 19

like neurons and skeletal muscle fibers, ardiac cells are capable of generating electrical signals (i.e. excitable tissue)

these electrical signals, called Actional Potentials, lead to the event of contraction in a similar manner as skeletal muscle fibers (i.e. release of calcium into the cytosol causing the interaction of actin and myosin)

the cardiac cycle refers to the repetitive contraction and relaxation of the heart

Question 20

what are the systole and distole

Answer 20

systole: a term used to describe the contraction phase of the cardiac cycle
diastole: a term used to describe the relaxation phase of the cardiac cycle

Question 21

why the proper timing is essential for the cardiac cycle

Answer 21

in order for the cardiac cycle to be effective, proper timing is essential. time must be permitted for the ventricles to fill, the atria must contrac tprior to the ventricles, and both ventricles must pump the same amount of blood at the same time.

the initiation of the cardiac cycle and the coordination of the complex timing of events is achieved by the Cardiac Conduction system.

Question 22

what initiated Cardiac contraction?

Answer 22

cardiac contraction is initiated by a group a specialized cells called a sinoartrial node (SA node). these myocytes have the ability to spontaneously depolarize.

the electrical signal then travels through the interconnected atrial cells and reaches the Atrioventricular node (AV node), where the signal is slightly delayed.

the signal is tehn delivered to the ventricles by the bundle of his and the purkinje fibers

Question 23

what are Bundle of His and Purkinje Fibers

Answer 23

Bundle of HIs: collection of muscle cells specialized for electrical conduction from the AV node to the point of the apex of fascicular branches.

the fascicular branches lead to the purkinje fibers which excite the ventricles causing the ventricle muslce to contract at a paced interval

Question 24

the steps of the cardiac conduction system

Answer 24

1 sinoatrial node reaches hreshold and generateds an action potential
2 depolarization is spread to all the cells of the atria via gap junctions and internodal pathways
- a wave of contraction follows the wave of depolarization

3 depolarization reaches the AV node, which conducts the electrical impulse more slowly: 100 msec delay
- this gives atria time to empty into ventricles

4 the action potential is conducted from the AV node through the AV bundle and down the left and right bundle branches

5 the action potential reaches the Purkinje fibers which conduct the impulse through thte ventricles where it passes from cell to cell in the contractile fibers via gap junctions

Question 25

what happens in ECG tracing

Answer 25

SA node activity and atrial activation begin (60-100 action potentials per minute at rest)

Question 26

what happens in P wave

Answer 26

P wave: atrial depolarization stimulus spreads across the atrial surfaces and reaches the AV node

Question 27

what happens in P-R interval

Answer 27

P-R interval: conduction through AV node and AV bundle there is a 100-msec delay at the AV node. Atrial contraction begins

Question 28

what happens in Q wave

Answer 28

Q wave: beginning of ventricular depolarization the iimpulse travels along the interventricular septum, whithin the AV bundle and the bundle branches to the Purkinje fibers and, by the moderator band, to the papillary muscles of the right ventricle

Question 29

what happens in QRS complex

Answer 29

QRS complex: completion of ventricular depolarization the impulse is distributed by Purkinje fibers and relayed through out the ventriculra myocardium. Atrial contraction is completed, and ventriculra contraction begins

Question 30

what the SA node and the action potential are responsible for cardiac contraction

Answer 30

the cells of the SA node are responsible for **initiating** cardiac contraction. they achieve this by 'spontaneously' depolarizing. the plasma membrane of these cells is **'leaky' to 'Na+** this prevents the cells of teh SA node from ever achieving a true resting state (i.e. as soon as they repolarize, they start depolarizing again) the ANS controls th**e heart rate **by influencing the rate of spontaneous depolarization in the SA node. ## Footnote the SA node naturally discharges 100 times per minute; therefore, at rest we have a predominate PSNS tone to keep the restin gheart rate at 60-80 bpm

Question 31

what is Cardiac Action Potential

Answer 31

the action potential in cardiac cell sis very similar to that observed in neurons and skeletal muscle, with one exception. cardiac cell membranes contain Ca++ channels, therefore, Ca++ moves into the cells during depolarization, and creates a **'plateu' phase** this influx of Ca++ causes teh release of more Ca++ from the Sarcoplasmic Reticulum, also called the 'Calcium induced calcium release'

Question 31

pacemaker cells & contractile cells

Question 32

what is electrocardiogram (ECG)

Answer 32

when electrodes are placed on the skin, an electrical signal of the entire heart can be observed. = electrocardiogram (ECG) the ECG is an important diagnostic tool as it can detect abnormalitities in cardiac conduction

Question 33

what are the characteristic of an action potential and a twitch of contraction in skeletal muscle

Answer 33

in a skeletal muscle fiber, the action potential is relatively brief and ends as the related twitch contraction begins. the twitch contraction is short and because the refractory period ends before peak tension develops, twitches can summate and tetanus can occur

Question 33

what are the characteristic of an action potential and a twitch of contraction in cardiac muscle

Answer 33

in a cardiac muslce cell, the AP is prolonged, & thus the period of active muscle contraction is also extended because the refractory period continues until relaxation is well under way, summation cannot occur, and tetanic contractions do not occur in normal cardiac muscle tissue. this feature is vital: a heart in tetany could not pump blood.

Question 34

three stages of an action potential in a cardiac muscle cell

Answer 34

1. rapid depolarization 2. plateeu 3. repolarization

Question 35

rapid depolarization

Answer 35

voltage-gated sodium channels open, & an influx of sodium ions creates rapid depolarization. the channels involved are called fast sodium cahnnels, because they open quickly & remain open for only a few milliseconds

Question 36

plateeu

Answer 36

during plateeu, the membrane potential remains near 0 mV. As potential nears +30 mV, voltage-gated sodium channels close & cell begins actively pumping Na+ out. however, slow voltage-gated Ca+ cahnnels are opening & remain open for a relatively long period- roughly 175 msec. while Ca+ channels are open, the entry of Ca++ balances the loss of Na+, and the membrane potential hovers near 0 mV.

Question 37

repolarization

Answer 37

After 175 msec, slow Ca+ channles begin closing & slow potassium channels open. as the channels open, K+ rush out, & repolariztion restores the resting potention.

Question 38

The three phase of cardiac cycle

Answer 38

phase 1: ventricular filling phase 2: ventricular systole phase 3: early diastole

Question 39

phase 1: ventricular filling

Answer 39

the volume of blood in the ventricles increases passively due to the low pressure in the heart. the SA node depolarizes leading to atrial depolarization (P-wave) and contract.

Question 40

phase 2: ventricular systole

Answer 40

the depolarization wave reaches the ventricles and they begin to contract (QRS-waves). When the ventricular pressure exceeds the atrial pressure, the AV valve closes (1st sound). Blood propelled through the aorta.

Question 41

phase 3: early diastole

Answer 41

as the pressure in the ventricle begins to decline, it is exceeded by the pressure in the aorta, causing the aortic valve to close (2nd sound)

Question 42

what is the cardiac reserve?

Answer 42

the cardiac reserve is the difference between the CO at rest and the maximum CO the heart can generate Average cardiac reserve is 4-5 times resting value - exercise draws upon the cardiac reserve to meet the body's increased physiological demands and maintain homeostasis **starling's law**: the more the heart is stretched (filled) before contraction, the more forcefullly the herat will contract... equalizes output of right & left ventricles.

Question 43

what is cardiac output

Answer 43

any factor effecting theheart rate or stroke volume will affect cardiac output stressor - any body movement when uses energey affect cardiac output

Question 44

when does coronary circulation occur

Answer 44

only during the **relaxation** pharse of ventricular diastole, will blood actually flow through the coronary coronary coronary arteries supply the myocardium with O2 and nutrients during ventricular contraction the coronary arteries that enter the myocardium are compressed due to high intraventricular pressure temporarily stopping blood flow blockage of these arteries with plaques, leads to failure to deliver O2 and resutls in tissue ischemia (lack of O2) angina = due to brief ischemia Mi = due to severe ischemia (cuases death of cardiomyocytes) - myocardial infarction/ heart attack

Question 45

where the coronary veins collect into

Answer 45

coronary veins all collect into the coronary sinus on the back part of the heart: The coronary sinus empties into the right atrium where the deosygenated coronary blood joins with oxygen-depleted blood from the rest of the body

Question 46

what is atherosclerosis

Answer 46

the buildup of fats, cholesterol and other substances in and on the artery walls - build up of atherosclerotic plaques

Question 47

what regulate blood flow to the heart

Answer 47

blood flow to the heart: - local meabolism also regulates blood flow to the heart - the heart only receives blood during **diastole** (high pressures during systole prevent blood flow). this is achieved in part by the 'aortic recoil' which aids **cardiac** **perfusion** through the coronary arteries Cardiopulmonary bypass (CPB) is a technique that uses a heart-lung machine to support the heart and lungs during surgery.