Cardiovascular System

Intrinsic conduction system

group of cardiac cells that generate and distribute action potentials to myocardium

components of intrinsic conduction system

1. sinoatrial nerve (SA) node: “pacemaker”

2. atrioventricular (AV) node: “back-up pacemaker”

3. bundle of His (atrioventricular bundle)

4. bundle branches

5. purkinje fibers

heart contraction

first the atria contracts then the ventricles contract. ventricles begin at the apex and proceeds superior forcing the blood towards the sumilunar valves

cardiac cycle

systole = contraction of heart
diastole = relation of heart

normal cardiac values

1. HR = 60-100 BPM

2. tachycardia = HR > 100 BPM

3. brachycardia = HR < 60 BPM

4. BP = 90/60 mmHg - 140/90 mmHg

5. stroke volume (amt. blood pumped w 1 contraction) = 70ml

6. cardiac output (volume of blood pumped in a minute) = 5L (HR X SV)

7. Blood volume = 4-6L

types of blood vessels

1. arteries (branch) = carry blood away from heart

2. capillaries (microscopic) = gas exchange and nutrient/waste exchanges

3. veins (merge) = carry blood to the heart

structure of tissue layers

1. tunica interna (intima) = lining of blood vessels - simple squamous epithelium + basement membrane

2. tunica media = controls vessel diameter - smooth muscle and elastic fibers

3. tunica externa (adventitia) structural support - collagen fibers

arteries vs. veins

arteries have more smooth muscle and elastic tissue than veins

types of arteries

1. elastic (conducting) arteries

2. muscular (distributing) arteries

3. arterioles

elastic arteries

aorta + major branches, thick walls of large lumen, low resistance to blood flow

muscular (distributing) arteries

medium sized arteries that distribute blood to individual organs

arterioles

smallest arteries that control blood flow into capillary beds

capillaries

tunica intima only: single layer of endothelial cells + basement membrane

types of veins

1. venules (smallest)

2. veins (thin walls w large lumens) = limb veins have valves

3. sinuses (specialized - endothelium only) =

   1. coronary sinus = drains myocardium

   2. dural sinus = drain brain tissue

venous return

1. vascular valves = prevent backflow of blood

2. skeletal muscle contraction = “pump”

3. negative intrathoracic pressure = inhalation creates pressure gradient between thorax and inferior regions

   • blood flows against gravity = moves from high pressure in abdomen + lower limbs to low pressure in thorax

pulse points

where arteries are close to surface (pulse can be palpated)

• common carotid artery = up neck/head into brain

• brachial artery = draws arterial blood

• radial artery = most common

• femoral artery = groin region

• dorsalis pedis artery = can feel pulse, there is adequate blood flow to lower limbs

circulatory shock

blood vessels are inadequately filled

BP drops = poor perfusion (blood flow)

blood characteristics

• connective tissue (only fluid tissue), 45% formed elements (cells), 55% plasma (fluid)

• pH = 7.35-7.45 (arterial blood)

• volume = 4-6L

blood plasma

• nonliving,

• 90% H20

• 8% proteins (albumin, fibrinogen, prothrombin) - clotting proteins

• 2% nutrients, respiratory gases, electrolytes, and wastes

• serum is plasma w clotting proteins removed

formed elements

1. erythrocytes (RBC’s) = transport O2/CO2, buffer H+

2. leukocytes (WBC’s) = fight infection

3. thrombocytes (platelets) = hemostasis

hematocrit

• % RBC’s in blood sample

• normal adult values:

  • males = 47 ± 5%

  • females 42 ± 5%

• males have more because testosterone causes more erythropoietin secretion by kidney

erythrocyte structure

• flexible, biconcave disc

• lack nucleus and organelles

• plasma membrane filled w hemoglobin

hemoglobin structure

heme = iron ion where O2 attaches

globin = 4 proteins chains that bind CO2

erythropoiesis

• production of RBC’s and produced by red bone marrow

• stimulus = hypoxia (low O2)

• kidneys stimulated by hypoxia produce hormone called erythropoietin (EPO)

• EPO stimulates red bone marrow to produce more RBC’s

RBC development

• reticulocyte (young RBC): accumulates hemoglobin

• late: ejects nucleus and organelles (amitotic) - anaerobic respiration only

• life span = 100-120 days

breakdown old RBC

globin: amino acids recycled

heme: only Fe+ recycled; rest is degraded to bilirubin by liver and excreted in feces

Leukocytes

1. neutrophils = bacteria

2. eosinophils = parasitic worms; allergic reactions

3. basophils = inflammatory response

4. lymphocytes = virus infected cells + tumor cells

5. monocytes = become macrophages; chronic infections (TB)

thrombocytes

platelets involved in homeostasis = mechanism for preventing blood loss when a vessel is injured

hemostasis

mechanism for preventing blood loss (3-6 min) highly regulated

1. vascular spasms

2. platelet plug formation

3. coagulation (blood clotting)

vascular spasms

vasoconstriction = immediately blood loss

triggered by chemical released from injured cells and platelets

platelet plug formation

1. platelets cling to collagen fibers

2. initiate chemotaxis (release of stored chemical messengers): positive feedback mechanism

3. more platelets brought to injury site

coagulation

• requires clotting factors and Ca+

• forms fibrin “net” that holds platelets together and traps other substances (RBC’s)

last 2 chemical reactions to coagulation

1. prothrombin (plasma protein) = thrombin enzyme. prothrombin activator catalyzes

2. fibrinogen (plasma protein) = fibrin (polymer of fibrinogen). “sticky net”. thrombin catalyzes

chambers and septum

1. Right and Left Atria: receiving chambers.

2. Right and Left Ventricles: pumping chambers.

3. The septum divides heart into right and left sides. Displays a remnant of fetal circulation: fossa ovalis

atrioventricular valves

tricuspid and bicuspid (mitral) valves

semilunar valves

pulmonary and aortic valves

endocardium

the smooth, slick inner lining of the heart; made of simple squamous epithelium

myocardium

made of cardiac muscle tissue; where contraction occurs

intercalated discs

interlocking surfaces on adjacent cardiac muscle cells that increase the surface area for contact

origin and insertion of cardiac muscle tissue

fibrous skeleton