Cardiovascular System

PowerPoint Presentation to accompany Hole’s Human Anatomy and Physiology, 10th edition, edited by S.C. Wache for Biol2074.01

Chapter 15-Part 1

You are responsible for the following figures and topics: Part I. Structure and function of the heart. Fig. 15.1 – The cardiovascular system supplies lungs and body in separate pathways.Fig. 15.2 Anterior view of the human heart.Fig. 15.3 – Location of the heart in the mediastinum.Fig. 15.4 – It is enclosed by a double membrane pericardium.Fig. 15.5 - The heart wall.Fig. 15.10, 15.11 - Two circuits: pulmonary circuit; systemic or body circuit.Fig. 15.6, 15.9 - Name all the parts: 4 valves, 4 chambers, vessels going in and out of the heart.Fig. 15.4 , 15.13 - Anterior and posterior views of the heart.Fig. 15.15 - Coronary circuit. Pathway of blood flowFig. 15.17 - The figure is made up of 5 subsets. Recordings during a cardiac cycle.Fig. 15.18 – Heart valves can be listened to at 2nd/3rd ribs and 5th/6th ribs.Fig. 15.19 - Cardiac conduction system. Fig. 15.22 - Study the phases of a cardiac cycle.Fig. 15.24 - control of cardiac output - [see table in the attached lecture handout]Read Clin. Appl. 15.5, p. 578, regarding hypertension.Fig. 15.37 – Vasoconstriction v. vasodilation control BP.Fig. 15.39 - When cardiac output increases and BP is high… Fig. 15.40 - Vasodilation in response to high BP.

Fig. 15.1

Pulmonary Circuit

Systemic Circuit

Systemic Circuit

Heart Serous Membrane• Pericardium

– fibrous pericardium: tough, fibrous connective tissue sac

– visceral pericardium: epicardium, outer lining of the heart, serous membrane

– parietal pericardium: serous membrane, forms the inner lining of the fibrous pericardium

• Pericardial cavity: serous fluid filled space between the pericardia

Heart Wall

• Epicardium: visceral pericardium

• Myocardium: cardiac muscle

• Endocardium: epithelium and collagenous fibers that line the inner wall of the heart

Fig. 15.4

Heart Chambers• Four chambers

• 2 Atria, left and right

– thin walled, receive blood returning to the heart

– Auricles extend from the atria

• 2 Ventricles, left and right

– thick walled, pump blood out of the heart into arteries

• Interatrial and interventricular septa separate the chambers

Heart Valves• Atrioventricular valves: at the border between atria and ventricles

– tricuspid: between right atrium and ventricle

– bicuspid: between left atrium and ventricle

– chordae tendineae: fibrous strings that prevent valve cusps from swinging into the atria

• Semilunar valves: contain three cusps

– pulmonary valve: between right ventricle and pulmonary arteries

– aortic valve: between left ventricle and the aorta

Fig. 15.6

Fig. 15.7

1 cm

Fig. 15.8

Bicuspid valve

Aortic valve

Tricuspid valve

Pulmonary Circuit

Systemic Circuit

Fig. 15.10

Fig. 15.11

Fig. 15.13

Blood Supply to the Heart -Use the coronary arteries and the coronary sinus to locate the anterior and posterior positions of the heart.

• Coronary arteries supply blood to the heart– circumflex artery– anterior interventricular artery– posterior interventricular artery– marginal artery

• Cardiac veins drain blood from the myocardium and join at the coronary sinus

Fig. 15.12

Fig. 15.14

Cardiac Cycle

• Atrial diastole: Atria relax and fill, the AV valves open

• Atrial systole: atria contract and push blood into the ventricles

• Ventricular systole: ventricles fill and contract as AV valves close and semilunar valves open

• Ventricular diastole: ventricles relax and valves open

Fig. 15.16

Note that the R and L atria contract together followed by the R and L ventricles contracting together. This results in the typical lub-dup sound in a stethoscope.Note that it takes two such sounds, lub-dup lub-dup, for one complete passage of one volume of blood through the R and L sides of the heart.

Note: Following is a complex figure of the cardiac cycle !!!

Fig. 15.17

LUB DUP LUB DUP

P

ress

ure

(m

mH

g )

V

olu

me

(ml)

Heart SoundsHeart sounds are heard through a stethoscope at 2nd/3rd ribs and 5th/6th ribs andcan indicate the condition of the heart valves : First lub-dup goes with transportto lungs; second lub-dup goes with transport to the body.Follow one volume through the heart:• Lubb: aortic valve open, R and L AV-valves close = emptying of the

ventricles to the body and filling of the atria. Dupp: aortic valve close, R and L AV-valves open = filling of the R

ventricles; emptying of the atria• Lubb: pulmonary valve open, AV-valves closed = emptying of the

ventricles to the lungs and filling of the atria. Dupp: pulmonary valve close, AV-valves open = filling of the ventricles;

emptying of the atria

• Vibrations: due to blood flow and opening and closing of the heart valves• Murmur: abnormal heart sound

Cardiac Conduction System (CCS)

Specialized cardiac muscle cells in the SA node region initiate and send impulses through the myocardium:• Sinoatrial node (S-A node)

– located in the right atrium near the superior vena cava– rhythmic pacemaker

• From the S-A node impulses are conducted along the interatrial muscle throughout the atrial myocardium with the help of the intercalated disks that connect all cardiac muscle fibers.

• Atrioventricular Node (A-V nose)– located in the inferior interatrial septum– conducts impulses between the atria and ventricles

• A-V bundle (Bundle of His)– located in the interventricular septum– divide into left and right bundle branches– give rise to Purkinje fibers that carry impulses throughout the

ventricular myocardium

Fig. 15.19

Electrocardiogram (ECG or EKG) It is a recording of the myocardial electrical changes during the cardiac cycle. Electrical changes precedecardiac muscle contraction • P wave: corresponds to depolarization of the

muscle membrane in the atria prior to contraction• QRS complex: corresponds to ventricular

depolarization of the muscle membrane prior to contraction

• T wave: corresponds to ventricular repolarizationNote: Atrial repolarization is obscured by the QRScomplex

Fig. 15.22 - ECG

Cardiac Cycle and Heart Rate RegulationHeart rate is under control by the S-A node:• Vagus nerve: cholinergic parasympathetic fibers that decrease heart

rate; to keep the heart slowed.• Accelerator nerves: adrenergic sympathetic nerves increase heart

rate and strength of contraction.

• Medulla oblongata: cardiac control center– cardioinhibitory reflex center– cardioacceleratory reflex center

• Baroreceptors: in carotid and aortic bodies respond to blood pressure changes

• Stretch receptors in the vena cava control heart rate and force of contraction of the heart

Heart rate and stroke volume and thus cardiac output can be altered by a baroreceptor reflex. Baroreceptors located in the aortic arch and the carotid arteries detect changes in blood pressure. If blood pressure decreases, the baroreceptors inform the cardioregulatory center in the medulla oblongata. The medulla oblongata increases sympathetic stimulation to the SA node thus increasing stimulation to the myocardium, which increases calcium availability and thus increases heart rate (the rate at which the heart contracts) and stroke volume.

Fig. 15.23

Spinal Cord

Medulla

Cerebrum

Factors that Influence Arterial Blood Pressure (BP), TB, p.572