Animal Circulatory and Respiratory Systems

Chapter 42

Internal Transport• Gastrovascular cavity makes circulatory

system unnecessary

• Open and closed circulatory systems

• What are the limits an open circulatory system places on an organism?

• What is the difference between an artery and a vein?

• Arteries carry blood away from the heart

• Veins bring blood back to the heart

• Why do veins have valves and arteries do not?

• Veins move blood against gravity without benefit of the heart contraction

• Blood flow:– Heart arteries arterioles

capillaries venules veins heart

• Which chamber of the heart receives the blood?

• Which chamber pumps the blood?

Vertebrate Circulatory Evolution• Fish have 2 chambered heart, one beat circuit:

– 1 atrium– 1 ventricle

• Amphibians have 3 chambered heart:– 2 atria– 1 ventricle

• Reptiles have 3 – 4 chambered heart:– Septum keeps 2 parts of ventricles separate

• Mammals and birds have 4 chambered heart!

The Heart• Cardiac muscle• Atria have thin walls• Ventricles have thick and powerful walls• Systole = ventricular contraction blood is

pumped• Diastole = ventricular filling• Lub dub = heart sounds opening and closing

of the valves– Lub = contraction of ventricles (AV closing)– Dub = blood recoiling against SL valves

• Heart murmur = valve defect

• CO = cardiac output ; – Volume of blood pumped/ minute

• (avg: 75ml x 70 bpm = 5.25 L/min)

• SV = stroke volume:– Amount of blood pumped by L

ventricle/contraction

• CO is effected by heart rate and SV– During exercise CO ↑ 5X

• Myogenic heart can generate its own electrical stimulus

• SA node is the pacemaker of the heart– Influenced by antagonistic nerves and

hormones

Arteries and Veins• How do differences between arteries and

veins reflect their different functions?

• Artery wall is very thick to absorb pulsation from heart

• Veins are wider in diameter and are not as muscular

• Veins have valves

• Capillaries have only single layer of endothelium

Blood Pressure• The force that blood exerts against vessel

walls– Determined by cardiac output, blood volume, and

resistance

• BP is greater in arteries than veins• Pulse is measure of BP• Exact BP is measured as systolic/diastolic

pressures• Constricted blood vessels have higher BP

than dilated vessels • In veins heart has little effect on BP• How, then does blood move in veins?

Blood Flow

Velocity

Internal Control of Blood Pressure1. Baroreceptors in wall of blood vessels

detect changes and notify the brain (medulla)

2. If high, cardiac center stimulates parasympathetic nerves (causes ↓HR) and vasomotor center inhibits sympathetic nerves controlling smooth muscle vasodilation

3. Also, hormones – angiotensin (vasoconstrictor), aldosterone (Na+ retention in kidneys)

1. Angiotensin blockers and ACE (angiotensin converting enzyme) inhibitors are high blood pressure meds

Blood Flow Through Capillary

BedsTypically only 5-10% capillary beds are open at a time.

“At rest 15-20% of circulating blood supplies skeletal muscle. During vigorous exercise this increases to 80-85% of cardiac output. Blood is shunted away from major organs such as the kidneys, liver, stomach and intestines. It is then redirected to

the skin to promote heat loss” Wilmore JH and Costill DL. (2005) Physiology of Sport and Exercise: 3rd

Edition. Champaign, IL: Human Kinetics

Capillary Movement of Fluids

Lymphatic System

• Lymphatic system returns lost blood to circulatory system– 4 L/day– Returns near jxn vena cava/rt atrium

• Lymph and plasma similar, except lymph has little protein

• Lymph nodes filter the lymph• Help fight infection• Edema = swelling (may be due to obstruction of

lymph vessels) -due to inflammation, injury, parasitic infection OR due to protein deficiency

Lymphatic Filariasis – caused by parasitic worm that imbeds in lymphatic vessels

Blood Cells

• RBC = erythrocytes– 25 trillion, 3 to 4 month lifespan– Biconcave disk

• ↑gas exchange due to ↑ surface area• Lack nucleus, more hemoglobin space• Lack mitochondria, don’t use O2 that they carry

Blood Cells

• WBC = leukocytes– Monocytes and neutrophils are phagocytic– Lymphocytes = B and T cells– Spend most of time out of circ. system

Blood Cells• Platelets

– Cellular fragments– Clotting

• Fibrinogen fibrin

• Production (all types)– In marrow pluripotent stem cells– Erythropoietin (hormone) stimulates

production when O2 levels low • banned performance enhancing drug EPO

How can 1 heartbeat circulate

blood through 2 capillary

beds?

What are the advantages and disadvantages of the amphibian circulatory system?

Why do endotherms have the greatest need for a 4 chambered heart?

Birds and mammals show convergent evolution of 4 chambered heart!