KIN 358 - Exam 2

The major function of the Cardiovascular System (2)

Removal of carbon dioxide and other metabolic waste products

The major function of the Cardiovascular System (3)

Transport of hormones and other molecules

The major function of the Cardiovascular System (4)

Support of thermoregulation and control of body fluid balance

The major function of the Cardiovascular System (5)

Maintenance of acid-base balance

The major function of the Cardiovascular System (6)

Regulation of immune function

The major function of the Cardiovascular System (1)

Delivery of oxygen and other nutrients

Any system of circulation requires 3 components

1. A pump (the heart)

2. A system of channels or tubes (the blood vessels)

3. A fluid medium (the blood)

Primary goal of the cardiovascular system

To ensure that there is adequate blood flow throughout the circulation to meet the metabolic demands of the tissues

Heart Size

About the size of a fist

Heart Location

The center of the thoracic cavity

Heart Function

Pump that circulates blood through the entire cardiovascular system

Atria of the Heart

Act as receiving chambers

Ventricles of the Heart

Serve as pumping units

Pericardium

Tough membranous sac that encloses the heart

Right side of the heart pumps

Deoxygenated blood to the lungs through the pulmonary circulation

Left side of the heart pumps

Oxygenated blood to all other tissues in the body through the systemic circulation

Pulmonary Circulation (right heart)

Superior, Inferior vena cavae > right atrium > tricuspid valve > right ventricle > pulmonary valve > pulmonary arteries > lungs

Systemic Circulation (left heart)

Lungs > pulmonary veins > left atrium > mitral valve > left ventricle > aortic valve > aorta

Myocardium

Cardiac Muscle

Most powerful pump of the four heart chambers

Left Ventricle

Intercalated Disks

Interconnects individual cardiac muscle fibers end to end

Desmosomes

Structures that anchor the individual cells together so that they do not pull apart during contraction

Myocardium vs. Skeletal Muscle

1. Myocardium has to contract as if it were a single unit

2. Myocardial fibers are rather homogeneous in contrast to the mosaic of fiber types in skeletal muscle

3. The mechanisms of muscle contraction (cardiac muscle contraction occurs by calcium-induced calcium release

Coronary Arteries

The primary blood supply to the heart

Right Coronary Artery Divides Into

1. Marginal Artery

2. Posterior Interventricular Artery

Left (main) Coronary Divides Into

1. Circumflex Artery

2. Anterior descending artery

Atherosclerosis

Narrowing by the accumulation of plaque and inflammation

Spontaneous Rhythmicity

Cardiac muscles unique ability to generate its own electrical signal which allows it to contract without any external stimulation

Without neural or hormonal stimulation, the intrinsic heart rate (HR) averages

100 beats per minute

The four main components of the cardiac conduction system

1. Sinoatrial (SA) node

2. Atrioventricular (AV) node

3. AV bundle (bundle of His)

4. Purkinje fibers

The impulse for normal heart contraction is initiated by the

Sinoatrial (SA) node

Sinoatrial (SA) Node

A group of specialized cardiac muscle fibers located in the upper posterior wall of the right atrium

The SA Node cells spontaneously depolarize faster than any other myocardial cells because

They are especially leaky to sodium

SA Node Intrinsic Firing Rate

100 beats per minute

Sinus Rhythm

Rhythm established by the SA node

The electrical impulses generated by the SA node spread through to

Both atria and reaches the atrioventricular (AV) node

Atrioventricular (AV) Node

Conducts the electrical impulse from the atria into the ventricles, delays is about .13 seconds

Atrioventricular (AV) Node Location

Right atrial wall near the center of the heart

Reason for the delay from the atria into the ventricles

It allows blood from the atria to completely empty into the ventricles to maximize ventricular filling before the ventricles contract

Active Contraction of the atria is sometimes called the

"Atrial kick"

Right and Left Bundle Branches

Send the impulse towards the apex of the heart and then outward

Purkinje Fibers

They transmit the impulse through the ventricles approximately 6x faster than through the rest of the cardiac conduction system

Three Extrinsic Systems

1. The parasympathetic nervous system

2. The sympathetic nervous system

3. The endocrine system (hormones)

The Sympathetic Nervous System on Extrinsic Control

Sympathetic stimulation increases the rate of depolarization and conduction speed, and thus the heart rate

Maximal sympathetic stimulation can increase the heart rate to

250 beats per minute

The Endocrine System on Extrinsic Control

Exerts its effects by two hormones released by the adrenal medulla: norepinephrine and epinephrine.

Normal Resting Heart Rate

Between 60-100 beats per minute

Extended periods of endurance training (months to years) can cause the resting heart rate to decrease to

35 beats per minute or less

Lowest heart rate found in a world-class, long-distance runner

28 beats per minute

Electrocardiogram

Recording of the electrical activity or the heart to monitor cardiac changed or to diagnose potential cardiac problems

A standard ECG is recorded from how many electrodes?

10

Three basic components of the ECG

- The P wave

- The QRS complex

- The T wave

P wave

Represents atrial depolarization and occurs when the electrical impulse travels from the SA node through the atria to the AV node

The QRS Complex

Represents ventricular depolarization and occurs as the impulse spreads from the AV bundle to the purkinje fibers and through the ventricles

The T Wave

Represents ventricular depolarization

Cardiac Arrhythmias

An irregular heart rhythm that can occasionally occur due to disturbances in the normal sequence of cardiac events

Bradycardia

Resting heart rate lower than 60 beats per minute

Tachycardia

Resting heart rate greater than 100 beats per minute

Symptoms of both arrhythmias include

Fatigue, dizziness, light-headedness, and fainting

Premature ventricular contractions (PVCs)

Feeling of skipped or extra beats. Relatively common and result from impulses originating outside the SA node

Atrial Flutter

Atria depolarizes at rates of 200 to 400 beats per minute (a more serious arrhythmia)

Atrial Fibrillation

Atria depolarize in a rapid and uncoordinated manner (a more serious arrhythmia)

Ventricular Tachycardia

3 or more consecutive premature ventricular contraction. Compromises the pumping capacity of the heart and can lead to ventricular fibrillation

Ventricular Fibrillation

Depolarization of the ventricular tissue is random and uncoordinated. When this happens, little to no blood is pumped out of the heart

Cardiac Cycle

Includes all the electrical and mechanical events that occur during on heartbeat

Diastole

Relaxation phase - the chambers fill with blood. Approximately twice as long as the systole phase

Systole

Contraction phase - ventricles contract and expel blood into the aorta and pulmonary arteries

Diastole Occurs during the

T wave and continues until the next contractio

About _____ % of the blood filling the atria during diastole passively flows directly through the mitral and tricuspid valves into the ventricles. When the atria contract, the atria push the remaining _____ % of their volume into the ventricles.

70, 30

Lub (first sound)

The closing of the atrioventricular valves

Dub (second sound)

Closing of the pulmonary and aortic valves

Stroke Volume (SV)

The volume of blood pumped during one beat

SV= EDV - ESV

(Example: SV = 100 ml - 40 ml = 60 ml)

he SV at rest in the standing posture averages between

60 and 80 ml of blood

End-diastolic Volume (EDV)

The volume of blood in the ventricle at the end of diastole, just before contraction

Normal end-diastolic volume at rest

100 ml

End-systolic Volume (ESV)

The volume of blood remaining in the ventricle just after the contraction

Normal end-systolic volume at rest

40 ml

Ejection Fraction

The fraction of the blood pumped out of the left ventricle in relation to the amount of blood that was in the ventricle before contraction

Divide stroke volume by EDV

60 ml / 100 ml = 60%

The ejection fraction in healthy young adults usually average at about

60%

Cardiac Output (Q)

Total volume of blood pumped by the ventricle per minute

The average adult body contains about _____ of blood

5 L

Vascular System

Contains a aeries of vessels that transport blood from the heart to the tissues and back: the arteries, the arterioles, the capillaries, the venules, and the veins

Arteries

Large muscular, elastic, conduit vessels transporting blood away from the heart to the arterioles

Largest Artery

The aorta

Arterioles

Site of greatest control of the circulation by the sympathetic nervous system. Heavily innervated by the sympathetic nervous system and are the main site of control of blood flow to specific tissues

Capillaries

Narrowest and simplest vessels in terms of their structure, with walls only one cell thick. Virtually where all exchange between the blood and the tissues occurs

Venules

Where the blood goes after it leaves the capillaries to begin its return trip to the heart. Forms larger vessels called the veins

Veins

Blood vessels that transport blood back to the heart

Greatest vein transporting blood back to the right atrium from all regions of the body above and below the heart

The vena cava

Blood Pressure

The pressure exerted by the blood on the vessel walls (usually refers to arterial blood pressure)

Systolic Blood Pressure (SBP)

The higher number; represents the highest pressure in the artery that occurs during ventricular systole

Diastolic Blood Pressure (DBP)

The lower number; represents the lowest pressure in the artery corresponding to ventricular diastole when the ventricle is filling

Mean Arterial Pressure (MAP)

The average pressure exerted by the blood as it travels through the arteries

Estimating Mean Arterial Pressure (MAP)

MAP = 2/3 DBP + 1/3 SBR OR

MAP = DBP + [0.333 x (SBP - DBP)]

EXAMPLE

normal resting BP of 120 mmHg over 80mmHg

MAP = 80 + [0.333 x (120-80)] = 93 mmHg

Pulse Pressure

(SBP - DBP)

Blood flows from the region of the vessel with _____ pressure to the region of the vessel with _____ pressie

High, low

The resistance that the vessels provide is largely dictated by

The length and radius of the blood vessel and the viscosity or thickness of the blood flowing through the vessel

Resistance to flow calculation

Resistance = n x L / r^4

n = viscosity

L = length of the vessel

R ^4= radius of the vessel raised to the fourth power

Vasoconstriction

The constriction or narrowing of blood vessles

Vasodilation

The dilation or widening of blood vessels