Chapter 11

The Cardiovascular System

Heart(Cardiac Muscle)

• General– continuous, rhythmic beating– delivers: to cells thru blood• oxygen• nutrients• hormones• electrolytes

– pump to lungs • exchange CO2 for O2

Heart• Anatomy of the Heart– lies in the mediastinum

• medial cavity of the chest• big as fist 2nd rib and 5th rib

– pericardium• sac around heart• film of serous fluid friction free • Pericarditis - inflammation

– heart wall• epicardium - visceral pericardium• myocardium - thick cardiac muscle and

connective tissue• endocardium

– endothelial lining of heart chambers

• Chambers of the Heart– right atrium

• recieves blood “deoxygenated”• superior & inferior vena cava• tricuspid valve

– right ventricle• pumps blood to lungs• pulmonary artery• semilunar valve “pulmonary”

– left atrium• recieves blood “oxygenated”• pulmonary veins bicupsid(mitral) valve

– left ventricle• pumps blood to body• aorta• semilunar valve “aortic”

• Septum– divides chambers (wall)

• Auricles– wrinkled flap like appendages on atria– musculi pectinati

• muscle bundles in atria

• Valves– prevent backflow– atrioventricular valves

• tricupsid valve• mitral valve “bicuspid”• chordae tendinae

– white cords anchor flaps of valves attached to papillary muscles

– semilunar valves• pulmonary• aortic

• Cardiac Circulation–coronary arteries - O2 and nutrients–arise from aorta–coronary veins take CO2 & wastes–coronary sinus ---> right atrium

Cardiac Function• General– 70 beats/min– its own conduction system– contracts independently

• Conduction– sinoatrial (SA) node “pacemaker”• in right atrium ---> depolarization• atrical contract

– internodal fiber bundles• depolarization node to node

– atrioventricular (AV) node• junction of atria & ventricle• ventricular contraction

• Atrioventricular Bundle– purkinje fibers– rapid impulses

• failed pacemakers– slow h.r. – bradycardia < 60 beats/min– rapid h.r. -tachycardia > 100

beats/min– fibrillation

• rapid uncoordinated heart beat

• Cardiac Cycle– initiated by the SA node– Cycle• Systole -contraction ventricles• Diastole -relaxed atria fill

• Heart Sounds– auscultation– ‘lubb dubb’• Lubb AV valves close• Dubb semilunar valves close

– murmurs• abnormal heart sound• incompetent valve swishing sound• Stenosed- narrow valves

• Cardiac Output– stroke volume• volume of blood pumped w/ each beat

– cardiac output• 4900 ml/min ---> 4.9 l/min• SV x VR 70 ml/ beat x 70 beats/ min

– exercise• increase SV increase venous return

– cardiac reserve• ability of heart to increase cardiac output

• Stroke Volume Regulation– healthy heart increase SV– Starling’s Law of the Heart• more cardiac muscle stretches greater

stroke volume

• Regulation of Heart Rate– autonomic nervous system• parasympathetic innervation–vagus nerve ---> ACH–slows h.r.

• sympathetic innervation–speeds h.r. stimulate SA node–norepinephrine–AV cardiac muscle

– hormones and ions• epinephrine speeds up h.r. • Ca++ levels down - h.r. down• thyroxine levels up -h.r. up• K + levels drop causes abnormal heart

rate

– temperature, gender, exercise, & age• fetus 140 - 160• heat h.r. goes up

–congestive heart failure• hypertension•worn out and weak• age & coronary atherosclerosis

• Electrocardiogram– three basic features of ECG• atria–P wave- depolarization of atria-

atria contract• ventricle–QRS complex depolarization of

ventricles–T wave repolarization of

ventricles– shapes of the waves and the time

intervals

• Disturbances in Heart Rate & Rhythm–myocardial infarction- heart

attack– Ischemia- lack of oxygen–Fibrillation- irregular heart beat–Atherosclerosis- narrowing of

arteries–Artherosclerosis- scar tissue Ca

build up

Systemic & PulmonaryCirculation

• Capillaries ----> cells ----> capillaries ---->venuoles ---> veins ---> superior or inferior vena cava ---> right atrium ---> tricuspid valve --> right ventricle ---> pulmonary valve ---> pulmonary artery ---> lungs ---> pulmonary veins ---> left atrium ---> bicuspid valve --> left ventricle ---> aortic valve ---> aorta --->arteries ---> arterioles ----

Blood Vessels• General– closed system

• blood in vessels

– principal types of blood vessels– arteries

• blood away from heart• arterioles

– capillaries• exchange materials w/ cells• capillary beds

– veins• venuoles• blood toward heart

• Blood Vessel Wall– tunica interna ~ simple squamos– tunica media ~ smooth muscle– tunica adventitia ( externa) ~

connective• Major Arteries– aorta ~ largest artery• head and neck

– carotid, brachiocephalic, subclavian

• upper limbs and thorax– brachial, radial, ulnar

• abdomen– hepatic

• pelvis and lower limbs– renal - kidneys

• Major Veins– superior vena cava

• head and neck• jugular & subclavian• upper limbs and thorax• brachial & radial

– inferior vena cava• abdomen• hepatic and mesentaric• pelvis and lower limbs• renal and femoral

• saphenous (LONGEST VEIN)

• Capillaries– wall only one layer thick– exchange between blood & tissues

• nutrients, oxygen, CO2, & wastes

• Special Circulation– brain• Circle of Willis• brain blood barrier

– hepatic• digestive organs• liver

– mesenteric• intestine

Physiology of Circulation• Pulse– expansion and recoiling of artery– carotid, brachial, and radial

• Blood Pressure– general• systolic / diastolic• pressure against walls of artery

– Gradient auscultatory method• 120 mm Hg / 80 mm Hg brachial artery

–Measuring Ventricular pressure• Systolic- contraction• Diastolic- relaxation

• Factors Effecting Blood Pressure– resistance• directly related to cardiac output• vasoconstriction ~ sympathetic• chemicals , temperature, diet• Kidneys- blood volume• autonomic nervous system• Blood viscosity- > resistance

– variations in pressure• hypotension

– systolic < 100 mm Hg– diet

• hypertension– > 140 / 90 sustained– myocardium enlarged

Cardiovascular Disease• Developmental– con genital– heart defects

• Aging– atherosclerosis ~ narrowing of veins– cholesterol “LDL’s” ~ form plaque– ischemic heart disease ~ lack of oxygen– angina pectoris ~ heart pains–myocardinal infarction ~ heart attack– varicose veins ~ venous valves weakenthrombophlebitis