Circulation

Biology 11

S. MacInnes

• A heart beats about 100,000 times a day and 35 million times a year. • In one day, the heart pumps nearly 7200 litres of blood. In a 70-year

lifetime, it pumps about 185 million gallons. • An aorta is almost the diameter of a garden hose, but it takes ten

capillaries to equal the diameter of a strand of human hair.• There are 100,000 km of blood vessels in each human! • In ancient times, the heart was given special importance. The

Chinese considered that happiness originated in the heart, and the Egyptians considered the heart to be the source of intelligence and emotion.

• Heart cells can beat on their own without intervention from the brain.• No cell in your body is further away than 2 cells from a blood vessel• You have 96,000 km of blood vessels to sustain your 100 trillion cells• Your heart is no larger than the size of your fist with a mass of about

300 g• Your heart beats about 70 times a min from the day you are born

until you die…• If you could stretch out all your blood vessels there is enough to go

around the world twice.

…Interesting Facts

THINK!

• Small unicellular organisms do not need a circulatory system. Why do larger organisms need one?

• HINT: Think surface : volume ratio.

The Importance of Circulation

• Unicellular organisms do not need any specialized system to transport nutrients, wastes and gases.

• The cells of unicellular and simple multicellular organisms are never far away from the organism’s surroundings (from where nutrients, gases, etc. come from)

• The cells of larger organisms are too far away for such substances to diffuse to/from all cells. Therefore, a specialized transport system is required.

Transport in Animals:Open vs. Closed Systems

• Most animals have evolved specialized systems to transport gases, nutrients and metabolic wastes.

These systems in animals have two essential parts:

1. circulatory fluid (blood)

2. a pump (heart or other muscular structure)

• Some animals have blood vessels (optional)– if vessels are present… closed transport system.

– if absent ………… an open transport system

Transport in Animals- Open Systems

• Open System Ex: grasshopper• not true circulatory systems

• from the action of muscular movements, the blood circulates into open spaces and surrounding organs. Blood bathes cells directly in order for transport of nutrients etc.

• openings in the heart allow blood to enter.• the blood carries mainly food nutrients and metabolic wastes. • not very efficient: movement of blood is slow and under low pressure.• in insects, the blood does not carry oxygen. There is a separate tubular

system for this. • wing movement (muscles) of flying insects speeds up blood flow.

Transport in Animals- Closed Systems• only closed transport systems true circulatory systems.

Blood is contained within blood vessels.• closed systems can be simple or complex.• efficient.• ex. An earthworm’s transport system represents the most

basic of true circulatory systems• muscle movement from locomotion (movement) helps to keep

blood flowing.• earthworms have five pairs of pumps, “aortic arches” (simple

hearts)• flow of blood in earthworm:• pump contracts blood pumped into a ventral (‘belly’ side)

blood vessel blood flows into dorsal (‘back’ side) blood vessel blood returns to heart

• blood can only move in one direction.

Closed system Open system

Earthworm’s Five “Hearts”

The Human Circulatory

System

Purpose of the Circulatory system:

• Transport!– To bring oxygen and nutrients to the cells

– To take away wastes (For ex: CO2) from the cells

– To facilitate the immune system

Components of The Human Circulatory System

• Heart, blood vessels, blood

...Components of The Human Circulatory System

Blood Vessels

arteries– take blood from heart.

– not always rich in O2.

– size: 25 mm (aorta) to 0.5 mm.– branch into smaller arteries called

arterioles (< 0.5 mm). arterioles contain ‘smooth’ muscle that regulates blood pressure.

– ‘elastic’ in nature. they stretch and ‘bulge’ when heart pumps blood through feel your pulse!

…Blood Vessels

veins – take blood to heart– not always low in O2

– branch into smaller veins called venules

– the lumens (openings) are larger than that of arteries but walls are thinner.

– depend on contraction of surrounding muscle to move blood.

– contain valves prevent backflow of blood.

Look at the veins on this guy!

Valves in veins prevent backflow...

When the valves of the veins are leaky… varicose veins!

…Blood Vessels

Capillaries

– tiny blood vessels. about 0.008 mm in diameter. just wide enough for one red blood cell to pass through.

– one cell thick; makes exchange of materials between blood and body cells easy.

– connect arterioles and venuoles

– the total length of all the capillaries in your body is 1000’s of kilometres. total surface area is nearly 6000 m2. why?

– penetrate almost every tissue in the body.

Comparison of Blood Vessels

Blood Vessels of a Fetal Pig

Components of The Human Circulatory System

• The Heart– two atria (right and left) (singular = atrium)– two ventricles (right and left)– Has valves to prevent backflow

Label your diagram!

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• very cool heart videos

Circulatory Routes of the Human Cardiovascular System

• The CV system is a closed, one-way system (blood only flows in one direction)

• Blood flows in two distinct circuits

• pulmonary circuit • path of blood:• right side the heart lungs (blood picks up O2 and gets rid of CO2)

left side of heart.

• systemic circuit • path of blood:• left side of the heart tissues in the body to deliver O2, nutrients, get

pick up wastes right side of heart.

Valves of the HeartTWO kinds: Atrio-ventricular and Semilunar…

Atrio-Ventricular (AV) Valves

• each is located between an atrium and a ventricle

• when the ventricles contract, these valves prevent blood from flowing from the ventricles back into the atria

tricuspid valve

– has three ‘cusps’ or flaps that open and close.

– between right atria and right ventricle

bicuspid (mitral) valve

– has two ‘cusps’ or flaps that

open and close.

– (AKA mitral valve)

– between left atria and left

ventricle

...Valves of the HeartSemilunar Valves• located in the two major arteries as they leave the heart• prevent blood flow back into the ventricles• each have a crescent or half-moon shape

pulmonary valve– leads to the pulmonary artery– between right ventricle and pulmonary arteryaortic valve– leads to the aorta– between left ventricle and aorta

• Cool fact: Ever listen to your heart beat? It makes a “lub-dub” sound. As your ventricles contract, your AV valves close preventing backflow into atria “lub”. When your ventricles relax, the semilunar valves close preventing backflow “dub”

• animation: valves in action

Heart Valve Pics

CV Word Scramble• Several structures of the circulatory system are listed below. Unscramble the terms to

describe the flow of blood through the body. Start with "blood from the body". Present your answer as a flow chart-style graphic organizer.

• Blood from the body• bicuspid valve• Superior vena cava • carbon dioxide • right ventricle• Inferior vena cava• pulmonary valve• Left ventricle • oxygen • body• Left atrium• Pulmonary artery• Tricuspid valve• Pulmonary veins• lungs• Aortic valve• carbon dioxide • Aorta• Right atrium• oxygen

CV Word Scramble Answers!• Blood from the body• Superior vena cava & Inferior vena cava• Right atrium• Tricuspid valve• right ventricle• pulmonary valve• Pulmonary artery• lungs • Dump carbon dioxide • Pick up oxygen • Pulmonary veins• Left atrium• Bicuspid valve• Left ventricle • Aortic valve • Aorta • body• Pick up carbon dioxide • Dump oxygen

Locating Heart Sounds with a Stethoscope

Conduction System of the Heart• cardiac muscle can contract without

external nerve stimulation (i.e. messages from the brain). The heart can continue to beat for a short time once removed from the body

• the heart’s tempo is set by the sinoatrial node (SA node); a bundle of specialized nerves. It is often referred to as the pacemaker. Its tempo is set to about 70 bpm (beats per minute).

• the autonomic (automatic) nervous system regulates heart rate but does not initiate contraction (the SA node does). It speeds up/slows down the SA node as needed.

…Conduction System of the Heart• Electrical Impulse in Heart: • SA node initiates cardiac cycle. It sends out an

electrical impulse.

• electrical impulse spreads over both atria causing them to contract

• At the same time, it sends an impulse to the AV node

• impulse is slowly spread through AV node and then to the Bundle of His (atrioventricular bundle)

impulse spreads through both sides of the septum

impulse goes to Purkinje Fibres which stimulate contraction of ventricles!

ECG (Electrocardiogram)• An ECG can be used to measure the electrical fields

produced within the heart. Doctors can analyze such a ECG to diagnose heart problems.

P-wave

Atrial contraction

T-wave

Ventricles recover

QRS-wave

Ventricular contraction

Regulation of Heart Rate Autonomic Nervous System (ANS)

• Although the heart can beat without nervous intervention, heart rate must be regulated by the nervous system as conditions change

• The ANS is comprised of the sympathetic nervous system and the parasympathetic nervous system

ANS

Sympathetic nervous system

Parasympathetic nervous system

Stimulated by brain in times of stress. It makes heart beat faster. Blood flow increases.

Stimulated by brain in times of relaxation. It makes heart beat slower. Blood flow decreases.

• Tachycardia When Heart Rate > 100 bpm. This can be caused by exercise or drugs such as caffeine or nicotine.

Regulation of Blood Flow

• The Autonomic nervous system (ANS) maintains homeostasis automatically.

• Precapillary sphincter muscles encircle arterioles before capillary beds. The ANS can regulate blood flow to tissues by sending a nerve impulse to these muscles causing them to contract or relax.

• Contraction of precapillary sphincter muscles vasoconstriction (less blood flow)

• relaxation of precapillary sphincter muscles vasodialation (more blood flow)

What is Blood Pressure?• Blood pressure is the measure of force against the

blood vessel walls.

• measured in the brachial artery (in upper arm). It is measured in the units “mm Hg” (millimetres of mercury).

• Blood pressure has two readings; systole and diastole.

• systole: blood pressure when the ventricles are contracting.• diastole: blood pressure when the ventricles are relaxed.• blood pressure varies with age, health, exercise. A typical resting

bp is 120/80 (read as “120 over 80”)

What is this called?

Sphygmomanometer

• It is important to regulate blood pressure. Low blood pressure reduces blood flow. High blood pressure weakens arteries which may rupture. Consistently high blood pressure is called hypertension.

• bp is regulated by renal system (kidneys), nervous system, and by hormones. Together, physiological changes are made to raise or lower blood pressure.

• Special sensors called baroreceptors detect pressure change in the aorta and carotid artery (in neck). The baroreceptors send messages to medulla oblongata to increase/decrease.

Regulation of Blood Pressure

regulation of blood pressure

…Regulation of Blood Pressure

…Regulation of Blood Pressure• If blood pressure is LOW:• vasoconstriction: smooth muscle around the blood vessels contracts,

narrowing the lumen of the vessels ...bp • blood volume: blood volume …blood pressure • cardiac output Heart Rate (beats/min) and Stroke Volume (mL per beat)

increase… blood pressure

• If blood pressure is HIGH:• vasodilation: smooth muscle around the blood vessels relaxes.

the blood vessel opens up …bp .• blood volume: blood volume …blood pressure • cardiac output Heart Rate and Stoke Volume … blood pressure

measuring blood pressure

…Regulation of Blood Pressure

Cool facts:

• Some people think a alcoholic drink will warm you up on a cold day. It actually cools you down! Alcohol causes vasodilation of blood vessels in skin. this blood flow to skin…heat is lost!

• Alcohol makes some people congested! Blood vessels in nose dilate nasal passages close off.