20-1 The Cardiovascular System: The Heart Beats approximately 100,000 x/ day Beating 3 billion x/ 70 yr life Over 100,000 km of blood vessels Total blood.

20-1

The Cardiovascular System: The Heart

• Beats approximately 100,000 x/ day

• Beating 3 billion x/ 70 yr life • Over 100,000 km of

blood vessels• Total blood volume in

an average adult is 5L

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Functions of the Cardiorespiratory System

• Protection

• Transportation

• Regulation

• Gas exchange

• Air purifier

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General Characteristics of the Heart

• Size of a closed fist• located in thoracic cavity

between lungs - mediastiniun

• 2 upper chambers - atrium

• 2 lower chambers - ventricles

• each set separated by a septum

• Right side deals with deoxygenated blood

• Left side deals with oxygenated blood

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The Heart’s Linings

• Pericardial sac filled with fluid to reduce friction(dense irregular CT)

• Epicardium - outer lining of heart

• Myocardium is the heart muscle

• Endocardium - lines the inside of the heart

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Chambers of the Heart

• Two Atria– Right atrium gets deoxygenated blood from the superior

and inferior vena cava– Left atrium gets oxygenated blood from pulmonary veins

• Two Ventricles– Left has thicker wall and pumps to the body– Right pumps blood to lungs to get oxygenated– Separated by interventricular septum

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The Four Valves of the Heart

• Atrioventricular valves (gateway to ventricles)– Right = tricuspid; – Left = bicuspid/mitral– Cusps attached to papillary muscles by chordae tendinae– Leaks = murmurs

• Semilunar valves - gateway to lungs (puulmonary) - and aorta (aortic)

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A-V Valves

Atria contract, blood fills ventricles through A-V valves

SL Valves

Ventricles contract, blood pumped into aorta and pulmonary trunk through SL valves

Valve Function

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Internal Structures of the Heart

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Blood Circulation

• Blood flow– blue = deoxygenated (R)– red = oxygenated (L)

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Path of Blood through the Heart

• Superior and inferior vena cava

• Right atrium• Tricuspid valve• Right ventricle• Pulmonary valve• Pulmonary trunk• Gas exchange in

lungs

• Pulmonary veins

• Left atrium

• Mitral valve

• Left ventricle

• Aortic valve

• Aorta

• Gas exchange with working cells

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The Vascular System

Venules and Veins– Carries blood towards

the heart

– Usually carries deoxygenated blood except for the pulmonary vein

– Major properties

• limited contractibility and elasticity

• One-way valves (varicose veins)

Arteries and Arterioles– Carries blood away from

the heart– Usually carries

oxygenated blood except for the pulmonary artery

– Thick smooth muscle wall

– Major properties• Contractibility• Elasticity

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The Vascular System

Capillaries– Permit exchange of nutrients and gases; walls are one cell thick– Capillaries connect arterioles and venules

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Skeletal Muscle Pump

Bringing Blood Back to the Heart

• Three main ways:– Thoracic pump– Venoconstriction– Skeletal muscle

pump•muscle

contraction•one-way valves

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Coronary Circulation• Right and left coronary arteries nourish the myocardium (heart muscle)• Left and right cardiac veins remove waste from the myocardium

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Conduction System of HeartCoordinates contraction of heart muscle

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• SA node (90-100 x/ minute)– cluster of cells in wall of Rt. Atria that fire an electrical pulse– begins heart activity that spreads to both atria– excitation spreads to AV node

• AV node (40-50 times x/ minute)– in atrial septum (dividing both atria) – transmits signal to bundle of His– delays the impulse to allow atria to fully contract

• Bundle of His & Purkinje Fibers– the connection between atria and ventricles (via septum) – divides into bundle branches & purkinje fibers, large diameter fibers that conduct signals quickly

Electrical Conduction of Heart

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Rhythm of Conduction System

• SA node fires spontaneously 90-100 times per minute• SA node setting pace since is the fastest• AV node fires at 40-50 times per minute• If both nodes are suppressed fibers in ventricles by

themselves fire only 20-40 times per minute• Artificial pacemaker needed if pace is too slow• Note:

– caffeine & nicotine increase activity

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Electrocardiogram---ECG or EKG• EKG

– Action potentials of all active cells can be detected and recorded

• P wave = Atrial Depolarization– spreads from the SA node through

the atria– 0.1s after the P wave begins, atria

contracts

– repolarization of atria not evident because it is buried in the QRS complex

• P to Q interval– conduction time from atrial to

ventricular excitation

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Electrocardiogram---ECG or EKG

• QRS complex = Ventricular Depolarization - shortly after QRS wave begins, the ventricles contract

• T wave = Ventricular Repolarization– ventricular repolarization

– occurs before the ventricles start to relax

– smaller & more spread out because repolarization takes longer

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Abnormal ECG/ EKG

• Large P Wave = Enlarged Atria- problems with the bi or tricuspid valves causes a backup of blood in the atria

resulting in the expansion of the atrial walls • Enlarged Q Wave = Myocardial Infarction (HEART ATACK!!) • Enlarged R wave = Enlarged Ventricles  • Flatter T Wave = The Heart receiving insufficient Oxygen 

• Tachycardia = a fast resting heart beat greater than 100bpm in adults  • Bradycardia=an abnormally slow/unsteady resting heart rate < 50bpm

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Heart SoundsWhere to listen on chest wall for heart sounds.

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Systole and Diastole

• Cardiac cycle– Systole when ventricles contract

(heart empties)– Diastole when ventricles relax

(heart fills)

• Heart sounds heard through a stethoscopeLub - a “long/low” sound- closing of the a-v valves (tri/bi)Dub - A “sort/sharp” soundclosing of the s-v (aorta/ pulmonary)

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Cardiac Cycle

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Cardiac Output

• Amount of blood pushed into aorta or pulmonary trunk by ventricle

• Determined by stroke volume and heart rate• CO = SV x HR

– at 70ml stroke volume & 75 beat/min----5.25 L/min

– entire blood supply passes through circulatory system every minute

• Cardiac reserve is maximum output/output at rest– average is 4-5 L/ min while athlete is 7-8 L/ min

Cardiac Output Calulations

Example: HR = 70 bpm SV = 70 mL

(Q) CO = HR x SV

= 70 beats/ min x 70 mL of blood/ beat

= 5040 mL/ min

= 5.04 L/ min

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Factors Affecting Heart Rate

1) Age – child’s HR much faster than adult

2) Emotional State of the Individual

- Parasympathetic Nervous System HR

- Sympathetic Nervous System HR

3) The physical state & efficiency of the heart

- Athletic heart has larger SV & lower RHR

- Couch Potato has a faster RHR

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Regulation of Heart Rate

• Nervous control from the cardiovascular center in the medulla– Sympathetic impulses ↑ heart rate &

contraction– parasympathetic impulses ↓ heart rate. – Baroreceptors (pressure receptors) detect

change in BP and send info to the cardiovascular center

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Regulation of Heart Rate

• Heart rate is also affected by hormones– epinephrine, norepinephrine, thyroid

hormones– ions (Na+, K+, Ca2+)– age, gender, physical fitness, and

temperature

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Influences on Stroke Volume• Preload (affect of stretching)

– Frank-Starling Law of Heart– more muscle is stretched,greater contraction force – more blood more force of contraction results

• Contractility– autonomic nerves (stress), hormonesa) Contractility = Parasympathetic Stimulation

• b) Contractility = Sympathetic Stimulation • Afterload

– amount of pressure created by the blood in the way– high blood pressure creates high afterload

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CV Systems’ Adaptation to Exercise

• With improved CV fitness- SV will increase (increased mass & contractibility)- therefore, RHR will decrease- Also the Max CO will increase

(VO2 Max will also increase due to this)- RBP will become more constant (120/80)- Rick of CV diseases will decrease- Increased # of capillaries around the heart

CV Systems’ Adaptation to Exercise

1) Increased Myoglobin (02 binding pigment)- acts as an 02 store aiding in the diffusion of 02

2) Increased oxidation of carbohydrates- training increases the muscles capacity to break

down glycogen in the presence of 02

3) Increased oxidation of fats- training increases the muscles capacity to break

down fatty acids in the presence of 02

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VO2 Max

VO2 Max

Definition: the max amount of O2 that can be consumed per minute during max exercise

(measured in mL/ kg)

- also known as aerobic power

- this is an individuals max aerobic capacity, or ability to consume O2 at the cellular level

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VO2 Max

• 93% of VO2 Max is under genetic influence, although it can be improved through training, there is a genetic ceiling

• Max VO2 doesn’t differ between boys & girls before puberty, after puberty females are 25 – 230% less than values

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VO2 Max

- Capacity depends on the amount of O2 that can be delivered to the muscles compared to the amount of O2 used by the muscle

- O2 consumption is important to prolonged exercise. (Endurance activities such as marathons, triathletes)

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Blood Pressure

 Blood pressure refers to the force exerted bycirculating blood on the walls of blood vessels  • Systolic - The force your blood exerts

when the heart is contracting

• Diastolic - The force your blood exerts when the heat is relaxing

 • Measured using a sphygmanometer

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Blood Pressure• Factors affecting blood pressure

– Cardiac output– Peripheral resistance– Blood volume

• Blood pressure– Normal = 120/80mmHg– Hypertensive = 140/90mmHg

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Hypertension

-  persistently elevated blood pressure- a major cause of heart failure, kidney failure, & stroke

Risk Factors:- 1)      Sex – male- 2)    Race – Black- 3)    Lifestyle – smoker, diet, drinker

4) Genetics – hypercholesterolemia, glucose intolerance (diabetic)

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Hypertension (mm Hg)

Normal Mild HT Moderate HT

Severe HT

Very Severe

HT

Systolic 120 140-160 160-180 180-200 200+

Diastolic 80 90-100 100-110 120-130 130+

Myocardial Infarctions/ Attacks

• Blockage of a coronary artery (due to plaque & fat) depriving the heart of O2

• Tissue in the affected area suffers permanent injury & signals its distress by a very sharp pain (angina)

• If the damage to the heart muscle is too extensive, the individual will not survive

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Myocardial Infarctions/ Attacks

• Signs: pressure in the chest that lasts more than a few minutes, or goes away comes back

• Spreading pain – shoulders, neck, left arm

• Lightheaded, sweating, nausea

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Angina Pectoris1. Chest pain due to CHD

2. Ischemia (insufficient blood supply)

3. Occurs when blood flow to the heart doesn’t meet increased demands

Rx: take nitroglyerin

- relaxes the veins ( amount of venous return, work of the heart)

- relaxes the coronary arteries

( the amount of blood supplied to the heart)

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