cardiac cycle

cardiac cycle- refers to a complete heartbeat from its generation to the beginning of the next beat

heart rate- frequency of the cardiac cycle (bpm)

systole- emptying phase of the cardiac cycle; contraction; increased pressure

diastole- filling phase of the cardiac cycle; relaxation; decreased pressure (lasts longer than systole)

The Role of the Medulla Oblongata and the Adrenal gland in regulating HR

  • Medulla Oblongata: Responsible for autonomic control of heart rate; increases heart rate through sympathetic stimulation and decreases through parasympathetic stimulation.

  • Adrenal Gland: This gland releases hormones such as adrenaline (epinephrine) and norepinephrine, which enhance heart rate and force of contraction during stress or physical activity.

    • Medulla: Vagus nerve (HR decreases), sympathetic nerve (HR increases)

    • Adrenal gland: epinephrine/adrenaline (HR increases)

cardiac cycle and blood pressure

  • ventricular systole- BP increases in major arteries

  • ventricular diastole- BP decreases in major arteries

    • This is responsible for the 2 numbers associated with BP (systolic pressure is the higher number/diastolic pressure is the lower number)

    • Normal blood pressure is 120 mm Hg over 80 mm Hg

cardiac conduction- rate at which the heart conducts electrical impulses

  1. sinoatrial (SA) node- pacemaker of the heart

    • coordinates contractions

    • located in the upper wall of the right atrium

    • generates a nerve impulse that travels throughout the heart wall causing both atria to contract

  2. Atrioventricular (AV) node

    • receives the electrical impulse from the SA node

    • slows impulses which allows atria to contract/empty

    • located near the bottom of the right atrium

  3. Sends the impulse down the left and right branches of the of the AV bundle to the apex of the heart

  4. Purkinje Fibers

    • receives the impulses from the AV bundle and triggers the contraction of the ventricles

heart-related diseases

(normal resting HR 60-100 bpm)

  • myocardial infarction (MI/heart attack)- heart begins to die because it isn’t getting enough blood flow

  • arrhythmias- any problem in the rate or rhythm of blood flow

    • tachycardia- HR above 100 pbm

    • bradycardia- HR below 60 bpm

    • supraventricular tachycardia (SVT)-HR is above 150 bpm

  • aortic stenosis- aortic valve narrows which prevents normal blood flow

  • coronary artery disease (CAD)- plaque (fat) build up which clogs arteries

  • cardiomyopathy- any disorder that affects the heart muscle

  • pericarditis- inflammation of the lining around the heart

  • valvular stenosis/insufficiencies- improper opening or closing

mitral valve prolapse- improper/flappy closure of the valve

-electrocardiogram (ECG or EKG)- medical test that traces the electrical activity of the heart by positioning leads on the body in standardized locations

  • used to detect underlying rate and rhythm mechanism of the heart

    • can measure: increased thickness of heart muscle, damage to heart muscle, impaired blood flow to heart muscle, abnormal electric activity (cardiac arrhythmias)

phases of the cardiac cycle

  1. P wave- atria contraction- atrial depolarization

  2. QRS wave- ventricle contraction- ventricular depolarization

  3. T wave- ventricle relaxation- repolarization

calculating HR

  • Normal HR- 300 divided by the number of large boxes between the QRS complexes

Irregular HR- count the number of R waves in a 6-second strip, and multiply by 10

the heart

a hollow muscular pump that supplies blood to all parts of the body

  • pericardium- a fluid-filled sac that surrounds the heart

  • epicardium- covers the outer surface of the heart

  • myocardium- muscular wall of the heart

  • endocardium- covers the inner surfaces of the heart (type of tissue that makes up the valves of the heart)

    -each side of the heart works as its own separate pump and has its own two chambers

  • right atrium- thin-walled area that receives the venous blood returning to the body by the veins

  • right ventricle- pump area of the heart’s right side. blood is pumped out of the pulmonary arteries and to the lungs

  • left atrium- thin-walled area that receives the oxygenated blood returning from the lungs by the pulmonary veins

left ventricle- pump area of the heart’s left side. Blood is pumped into the aorta and out to the rest of the body

heart valves

- since blood flow needs to be a one-way affair, there are valves at the entrances and exits of each ventricle

  • atrioventricular valves- entrance valves

  • semilunar valves- exit valves

  • tricuspid- entrance of the right ventricle, prevents backflow into the right atrium, 3 cusps/flaps make up the valve

  • pulmonary- entrance of the pulmonary artery, prevents backflow into the right ventricle

  • mital (bicuspid)- entrance of the left ventricle, prevents backflow to the left atrium, 2 cusps make up the valve

  • aortic- entrance of the aorta, prevents backflow into the left ventricle

steps of blood flow

  1. blood enters the right atrium from superior and inferior vena cava

  2. blood in the right atrium flows through tricuspid valve into right ventricle

  3. contraction of the right ventricle forces the pulmonary valve open

  4. blood flows through the pulmonary valve into the pulmonary trunk

  5. blood is distributed by the right and left pulmonary arteries to the lungs, where it unloads CO2 and loads O2

  6. blood returns from the lungs via the pulmonary veins to the left atrium

  7. blood in the left atrium flows through the bicuspid (mitral) valve into the left ventricle

  8. contraction of the left ventricle. forces the aortic valve open

  9. blood flows through the aortic valve into the ascending aorta

  10. blood in aorta is distributed to every organ in the body, where it unloads O2 and loads CO2

blood returns to the heart via venae cavae

functions of blood

  • transportation/distribution

    • respiratory gases, nutrients, waste products

    • regulatory molecules (hormones)

  • defense

    • clot formation (platelets)

    • protects against foreign substances (WBCs)

  • homeostasis

    • maintenance of body temp

    • regulation of pH and osmolarity (concentration) of the blood

composition of blood

type of connective tissue which consists of living cells suspended in a nonliving extracellular matrix (plasma)

  • formed elements (45%)

    • RBCs (erythrocytes)- transport oxygen gas from the lungs to tissues and carbon dioxide gas from tissues to the lungs

    • WBCs (leukocytes)- destruction of pathogens and production of an immune response

    • Platelets (thrombocytes)- preventing blood loss through platelet plugs and clotting (coagulation)

  • buffy coat (<1)

  • plasma (55%)

    • pale yellow fluid in which the formed elements of blood are suspended

    • 91% water and 9% dissolved solutes, proteins, nutrients, hormones

    • maintains osmotic pressure

  • maintains blood pH

production of blood

  • hematopoiesis- the process of blood cell production in red bone marrow

  • stem cells- all formed elements are derived from a single population of hematopoietic stem cells that undergo cell division followed by cell differentiation

  • erythropoiesis- production of RBCs in red bone marrow

blood types

  • determined by antigens on the surface of RBCs

  • antibodies in the blood plasma can bind to RBC antigens which can lead to clumping

  • agglutination- clumping

  • Rh factor- a protein that can be found on the surface of RBCs

    • if your blood cells have this protein, you are Rh+

    • if your blood cells do not have this protein, you are Rh-

  • type O is the universal donor because it does not contain type A or B antigens

  • type AB is the universal receiver because it does not contain A or B antibodies

blood vessels

  • arteries- carry blood AWAY from the heart, thick walls and high BP

  • arterioles- small arteries. precapillary sphincters that direct blood flow into capillaries

  • capillaries- carry blood from arterioles to venules; exchange of materials between blood and cells. very tiny, moves blood at the slowest rate. lack two outer layers

  • venules- small veins

  • veins- carry blood TO the heart; one-way valves; sinuses are large venous spaces. veins have a great ability to stretch and accommodate varying amounts of blood. they have valves to prevent backflow and rely on muscle contractions to squeeze blood in the right direction

    • structure of blood vessels (3 layers except for venules and capillaries)

      • outer layer- tunica adventitia (connective tissue)

      • middle layer- tunica media (smooth muscle and elastic tissue)

      • inner layer- tunica intima (endothelium)

circulation

  • capillary beds-

    • precapillary sphincters can close off capillaries in response to local signals

    • when precapillary sphincters are relaxed, blood flows through all capillaries in the bed

    • if precapilllary sphincters constrict, blood flow bypasses capillaries completely and flows through metarterioles

  • systemic circulation- blood flow from the left ventricle to all parts of the body and back to the right atrium

  • pulmonary circulation- blood flow from the right ventricle to the lungs and returning to the left atrium

control of blood flow

  • local control- blood flow is typically proportional to the metabolic needs of the tissues

  • nervous system- responsible for routing blood flow and maintaining BP

  • hormonal control- sympathetic action potentials stimulate epinephrine (increased HR) and norepinephrine (decreased HR)

blood pressure

  • BP is a measure of hw hard the blood pushes aginst the walls of the arteries as it moves through your body

  • BP INCREASES in the major arteries during ventricular systole (contraction) and decreases during ventricular diastole (relaxation)

  • various factors affect the average BP for an individual including:

    • age

    • weight

    • height

    • genetics

    • pregnancy

  • hypotension- low BP (below 90/60)

    • cause of hypotension:

      • dilation of arteries

      • dehydration

      • bloodloss

  • hypertension- high BP

    • cause of hpertension:

      • constriction of arterioles

      • too much salt in diet

      • obesity

      • smoking

blood disorders

  • anemia- low hemoglobin, iron deficiency » leads to hypoxia (decreased availability of oxygen to cells. causes paleness

  • sickle cell anemia- inherited blood disorder that is characterized by defective hemoglobin molecules

  • hemophilia- inherited bleeding disorder due to low levels or complete levels of clotting factors (platelets). bleeds and bruises very easily

  • leukemia- abnormally high WBC count

  • emboism- sudden obstruction of a blood vessel by an air bubble or blood clot circulating in the blood

  • deep vein thrombosis- formation or presence of a blood clot (thrombus) within a blood vessel, typically in the legs