• Arteries carry blood away from the heart• Veins carry blood back to the heart• Arterioles = small arteries• Venules = small veins• Capillaries: smallest vessels where nutrient,

waste and gas exchange take place. So narrow that blood cells proceed through single file. Walls are a single layer of epithelium.

Basic Definitions

Summary Concepts• The human heart has four chambers

left and right atria, left and right ventricles• The human heart has four valves

two atrioventricular valves (tricuspid and mitral) two semilunar valves (aortic semilunar and pulmonary semilunar)

• Pulmonary circulation: starts as blood leaves the right ventricle and enters the pulmonary trunk -> lungs -> pulmonary veins -> left atrium

• Systemic circulation: starts as blood leaves the left ventricles -> aorta -> head, arms, legs, body -> vena cava -> right atrium

Coronary circulation: provides blood to the heart muscle (myocardium). Aorta -> coronary arteries -> heart muscle -> cardiac veins -> vena cava.

The Heart and the Pulmonary Circulation

Superior vena cava

Inferior vena cava

Right Atrium

Right ventricle

Pulmonary trunk

Aortic arch Pulmonary arteries

Pulmonary veins

left atrium

Left Ventricle

Brachiocephalic artery

Left carotid artery

Subclavian artery

Coronary arteries

Cardiac veins

Valves and Conduction Fibersof the Heart

Atria: receive blood from principleveins and assist in filling the ventricles

Ventricles: pump blood under high pressure into pulmonary trunk andthe aorta.

Right Atrium

Right Ventricle

Left Atrium

Left VentricleTricuspid

PulmonarySemilunar Bicuspid

(mitral)

AorticSemilunar

Tissues of the Heart

• Pericardium: serous membrane sack surrounding the heart• Epicardium: serous membrane on outer surface of the heart• Myocardium: muscle of the heart• Endocardium: membrane lining the interior of the heart• Chordae tendonae: “heart strings” that guide the

atrioventricular valves.• Papillary muscle: small muscles that anchor the chordae

tendonae to the ventricular walls.

Heart Valves are passive and moveAccording to pressure gradients(like a loose screen door in a breeze)

AtrioventricularSemilunar

SuperiorVena Cava

InferiorVena Cava

Aorta

Pulmonarytrunk

PulmonaryVein

video

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The Cardiac CycleDiastole: period of relaxationAnd ventricular filling

Atrial Systole: atria contract force additional blood intothe ventricles.

Ventricular Systole: ventriclescontract and force blood intopulmonary trunk and aorta.

Conduction System Video

Purkinje Fibers

P

Q

R

S

T

Electrocardiogram

Electrical Recovery of Myocardium

Cardiac OutputStroke Volume (mL/beat) X Heart Rate (beats/min) = Cardiac Output (mL/min)

75 mL/beat X 72 beats/min. = 5400 mL/min.

Affects of Athletic Training

95 mL/beat X 60 beats/min. = 5700 mL/min.

- Stroke volume increases, heart rate decreases

Even though the athlete has a lower resting heart rate, s/he has a greaterCardiac Output than the untrained person.

Questions1.Do athletes have greater or lesser demands for oxygen than non-athletes?2.Do athletes have greater or lesser resting heart rates than non-athletes?3.How do you reconcile this observation?

Cardiac Center in the Medulla

Controls two nerves that lead to the heart1. accelerator nerve (sympathetic) *acts on the sinoatrial node and ventricles *increases heart rate using norepinephrine2. vagus nerve (parasympathetic) *acts on the sinoatrial node *decreases heart rate using acetylcholine

Sensory Inputs1.Proprioceptors(Am I moving more?)2.Baroreceptors(Is my blood pressure low?)3.Chemoreceptors(Is my CO2 high or O2 low?)

Cardiac Center(medulla)

Proprioceptors

Baroreceptors and Chemoreceptors in the carotid and aortic arteries

Sensorynerves

Motor Output1.Accelerator nerve(sympathetic)(releases norpepinephrine)increase rate and force2.Vagus nerve(parasympathetic)decrease rate

Vagus nerve

Acceleratornerve

Regulation of Heart Rate

Arteries = elastic elements Veins = capacitance elementscompliantvalvesskeletal muscles

= Resistance Vessels

Large arteries are elasticabsorb kinetic energystore potential energy

Arterioles and pre-capillarySphincters are muscular constrict add resistance dilate reduce resistance

Each organ has its own set ofArterioles, and capillary bedsWhich may be dilated or constricted

The microcirculation

O2

nutrients

1. Capillary exchange by diffusion

Vitamins

wastesCO2

2. Capillary exchange by bulk flow Starling hypothesis

- capillaries have low permeability to protein (osmotic effect)- hydrostatic pressure decreases as blood passes through

Net outward pressure = 11 mmHg Net inward pressure = -9 mmHg

Formation of Lymph

• Edema• Alcoholism• Elephantiasis