A&P - Chapter 17: Heart & Functions

Heart

Muscular blood pump, located within the thoracic cavity between the lungs. Is shaped like a blunt cone and is roughly the size of a closed fist (larger in physically fit people).

Heart Functions

1. Generating blood pressure

2. Routing Blood

   sending blood to either the pulmonary or systemic circulation.

3. Regulating blood supply to rest of body

left

The _____ side of the heart is larger than the other, leading to the heart’s tilted placement.

Pericardium

(Pericardial sac) double tissue layer surrounding the heart, forms the pericardial cavity, outside layer is fibrous pericardium (tough CT).

Serous Pericardium Layers

1. Parietal pericardium (superficial)

2. Visceral pericardium (deep)

(separated by pericardial fluid)

Layers of Heart

<Superficial to Deep>

1. Epicardium (different name, same as visceral pericardium).

2. Myocardium = muscle layer

3. Endocardium = simple squamous + CT

trabeculae carneae

The inner surface of ventricles contain ridges and columns called ___________________.

Heart Chambers

A) 2 atria (singular = atrium)

B) 2 ventricles

One of each on left and right, can be seen internally and externally.

Sulcus

Groove on surface of the heart, location of fat and blood vessels.

1. Coronary Sulcus

2. Anterior Interventricular Sulcus

3. Posterior Interventricular Sulcus

right atrium

The Superior Vena Cava and Inferior Vena Cava are the two large veins that bring blood to the heart from the rest of the body. Both deposit blood into the ____________.

left atrium

Four pulmonary veins bring blood from lungs to _____________.

Arteries Leaving Heart

A) Pulmonary trunk takes blood from ventricle to lungs.

B) Aorta takes blood from left ventricle to the rest of body.

Interatrial Septum

Right and left atria are separated by _________________.

Fossa Ovalis

Slight depression on the right side of interatrial septum.

Foramen Ovale

Former hole in heart for embryo’s blood to skip lungs.

Interventricular Septum

Separates right and left ventricles.

Direction of Blood Flow

1. Right Atrium

2. Right Ventricle

3. Lungs

4. Left Atrium

5. Left Ventricle

6. Rest of Body

Heart Valves

Folds of endocardium that allow blood to flow into or out of the ventricles, but not in reverse direction.

Two Types:

1. Atrioventricular Valves

2. Semilunar Valves

Atrioventricular Valves

Type of heart valve, located between an atrium and a ventricle.

1. Tricuspid Valve

2. Bicuspid/Mitral Valve

Semilunar Valves

Type of heart valve, located between a ventricle and an artery, both have three pocket-like cusps.

1. Aortic Valve

2. Pulmonary Valve

Tricuspid Valve

Three cusps of flaps, between right atrium and right ventricle.

Bicuspid Valve

(Mitral Valve) Two cusps between the left atrium and left ventricle.

Papillary muscles

To open the atrioventricular valves, each ventricle has ___________________, which are cone shaped and each is attached to a strong CT string.

Chordae Tendineae

Strong CT string that each papillary muscle is attached to. Pulls open flaps of atrioventricular valves when the papillary muscles flex.

Coronary Circulation

Since the heart is very active muscle, it needs a good blood supply.

Coronary Arteries

A) Left coronary artery

Splits Into:

1. Anterior Interventricular Artery

2. Circumflex Artery

B) Right coronary artery

Splits Into:

1. Right Marginal Artery

2. Posterior Interventricular Artery

same

Most veins follow the _____ routes of the arteries (within the sulci).

Coronary Sinus

The blood from most cardiac veins drain into this one large vein, which dumps blood into right atrium.

Cardiac Muscle AP

Steps:

1. Resting Membrane Potential

2. Rising Phase - Na+ channels open = depolarization

3. Plateau - Ca+2 channels open = partially maintains depolarization.

4. Repolarization - K+ channels open

5. Resting Membrane Potential Again

False

T or F: Cardiac muscle APs are faster than skeletal muscle APs.

True

T or F: The cardiac muscle still has an absolute and relative refractory period, the absolute refractory period is considerably longer in cardiac muscle, but that is because the whole AP is much longer.

Autorhythmic

Able to stimulate itself to contract at regular intervals, the heart does not need the NS or any other body system to beat.

Sinoatrial Node

Cardiac fibers located at a spot in the right atrium can spontaneously generate an AP. The AP will spread, so whole heart will contract.

Slow Depolarization

Unlike other muscle fibers, cardiac cells at SA node after an AP immediately leak in Na+ followed by Ca+2.

Prepotential

Once threshold is readed, next AP is generated.

pacemaker

SA node is often referred to as the ______________.

conducting

The heart has a ____________ system to help AP spread throughout the heart.

first

After the SA node begins AP, it will spread throughout right and left atria, atria contract ______.

delayed

When AP reaches a spot in the right atrium known as the atrioventricular (AV) node, the AP is ___________.

Atrioventricular bundle

Eventually, the slowed AP follows the __________________, cardiac cells delivering AP to ventricles. The AV bundle splits into right and left bundles for each ventricle.

Purkinje Fibers

Many small branches off of right and left bundles.

Electrocardiogram

(ECG or EKG) Measures electrical activity of the heart, electrical ups and downs indicate what’s occuring within the heart.

Consists Of:

1. P wave

2. QRS complex

3. T wave

P wave

Depolarization of atria

QRS complex

Depolarization of ventricles and repolarization of atria.

T wave

Repolarization of ventricles

Pericarditis

Inflammation of the serous pericardium, quite painful (every heartbeat), often unknown cause but can be from inflation, CT diseases, or radiation damage.

Cardiac Tamponade

Fluid or blood accumulates in the pericardial sac, can quickly be fatal if fluid is not drained, pressures heart.

Causes Include: heart wall rupture, malignant tumor, radiation damage, or trauma from an accident.

Congenital Heart Disease

Abnormal heart development.

Ex.) Septal Defect

Septal Defect

Hole between right and left sides of heart.

Patent Ductus Arteriosus

A fetal blood vessel connecting pulmonary trunk to aorta never closes before birth, blood can skip lungs, good for fetus, bad after birth.

Coronary Thrombosis

(Heart Attack) Sudden blockage of a coronary blood vessel, cardiac tissue will die without oxygen.

Infarct

(Myocardial Infarction) Region of dead heart tissue

Aspirin

_______ is well known to discourage thrombus formation = discourages heart attacks.

Atherosclerotic Lesions

More gradual blockages of blood vessels, results from buildup of cholesterol.

less blood flow = reduced ability of heart to pump blood

patient feels fatigue, and often chest pain.

Angina Pectoris

Pain felt in the left arm and left side of chest, is often a sign of a current or impending heart attack.

Cardiac Arrhythmia

Abnormal (or loss of) heart rhythm.

Tachycardia

Heart rate >100 bpm.

Bradycardia

Heart rate <60bpm.

Ectopic Focus

Any location of heart other that SA node which generates an AP, disrupts heart beat.

Cardiac Cycle

Repetitive pumping process of heart.

1. AV valves open

2. Atrial systole

3. AV valves close and ventricular systole, atrial diastole

4. Semilunar valves open

5. Semilunar valves close and ventricular diastole.

True

T or F: The heart can be viewed as two pumps (right side for lungs, left side for rest of body). Each pump has an atrium and a ventricle.

Atrium

Pumps and fills ventricles with blood.

Ventricles

Pumps and pushes blood through either lungs or systemic circulation.

Atrial Systole

Contraction of atria.

Atrial Diastole

Relaxation of atria.

End-diastolic Volume

Volume of blood in ventricles at end of relaxation.

Systolic Pressure

Maximum pressure within aorta.

Dicrotic Notch

Slight dip in aortic pressure from recoil of blood into ventricles (as semilunar valves close).

Diastolic Pressure

Minimum aortic pressure.

First Heart Sound

“lubb” = closing of AV valves.

Second Heart Sound

“dupp” = closing of semilunar valves.

Third Heart Sound

(Often very quiet/cannot be heard) = splashing of blood inside ventricles.

Murmur

Abnormal heart sounds, normally from a faulty valve.

Incompetent

(Valve staying open) = gurgling or swishing noise.

Stenosed

(Valve opening too tight) = “rushing” noise.

movement

Blood pressure is important for ___________ of blood. Blood moves from areas of high pressure to low pressure.

Mean Arterial Pressure

(MAP) average pressure in the aorta. MAP = CO x PR

Cardiac Output

(CO) Amount of blood pumped by the heart per minute.

CO = HR x SV

Peripheral Resistance

(PR) Total resistance against pumping blood.

Heart Rate

(HR) beats per minute (bpm).

Stroke Volume

(SV) volume of blood pumped during each heartbeat. It is larger during exercise because end diastolic volume is larger because of more venous return.

SV = End-diastolic volume - End-systolic volume

Venous Return

Blood returning to heart.

Cardiac Reserve

(CR) Difference between maximum CO and resting Co, athletes have larger amounts, couch potatoes do not.

CR = CO (Exercise) - CO (Resting)

Intrinsic Heart Regulation

Means of heart regulating itself (does not need NS or hormones).

A) Starling Law of the Heart

B) Preload/Afterload

Starling Law of the Heart

Resting time between beats increases, cardiac fibers contract with more force, this only applies until a maximum length of time.

Preload

Amount ventricle walls are stretched at the end of diastole, increases result in increased contraction strength = greater cardiac output too.

Afterload

Pressure against the ventricle’s pumping of blood, increases result in more work for heart.

Extrinsic Heart Regulation

Modification of heart rate and stroke volume from NS and hormones.

A) Hormones: Epinephrine & Norepinephrine, stimulate the heart to beat faster and with more force, produced in adrenal glands.

B) Nerves: Vagus nerve and cardiac nerves

Vagus Nerve

Innervates (connects to and stimulates) SA node and AV node, slows heart rate.

Cardiac Nerves

Innervates SA node, AV node, and myocardium, increases heart rate and increases force of contraction.

Homeostasis

Process of maintaining desired internal conditions.

Heart Maintains & Adapt these Conditions:

1. Blood pressure

2. Oxygen levels

3. Ion levels

4. Body temperature

Baroreceptors

Stretch receptors in large arteries including aorta.

measure blood pressure by detecting stretching of artery walls.

The reflexes work to increase/decrease heart rate and force of contraction in response to pressure.

Cardioregulatory Center

Portion of medulla oblongata (of brain) which receives baroreceptor APs and regulates NS heart stimulation as well as epinephrine and norepinephrine release. Increased artery wall stretching = decreased heart rate & contraction force.

Adrenal Medullary Mechanism

Process of releasing epinephrine and norepinephrine in response to large loss of blood pressure.

Emotions

___________, such as anger, excitement, and anxiety can stimulate heart rate and increase force of contraction.

Depression

_____________ can lower the heart rate and force of contraction.

Chemoreceptors

Sensory receptors that respond to chemical changes, detect oxygen, carbon dioxide and H+ levels. In extreme cases, such as the heart being deprived of oxygen, will activate cardiovascular reflexes.

Lower

Changes in K+ and Ca+2 levels will change the heart rate and force of contraction.

Increased K+ = _______ heart rate & stroke volume

Increase Ca+2 = ________ heart rate by higher stroke volume.

Body temperature

As ________________ increases, heart rate increases.

Blood Pressure

Measure of the force blood exerts against blood vessel walls, it cycles with the rhythm of the heart.