Bio 191 Ch. 36 - Circulation

Circulatory’s Main Function

transport necessary materials to animal’s body and transport waste away

Main Components

• Heart (pump)

• Blood (fluid)

• Blood Vessels (conduits)

Why is having many blood vessels important for animals?

Blood has to flow and surround all of the cells

Hemolymph & cells exchange?

Nutrients & waste (open)

Open Circulatory System

Hemolymph is pumped by one or more contractile hearts into hemoceol (body cavity)

Limitation to open circulatory systems

Cannot control where hemolyph is directed towards (lacks specificity)

Closed Circulatory System

Separate blood and interstitial fluid —> blood flows through vessels

Earthworms, cephalopods, vertebrates

Closed Circulatory System

Benefit of open circulatory systems

Needs less energy

Benefit of closed circulatory systems

Blood flow can be adjust of metabolic demands & animals can grow larger

Capillaries

• Carry oxygen and nutrients to body

• Carry away carbon dioxide and waste

• Thin walls allow molecule to diffuse

Single Circulation

Heart has

• Atrium - filling chamber

• Ventricle - single exit chamber

Double Circulation

• 4 chambers

  • left & right atrium

  • left & right ventricles

• 2 circuits

  • pulmonary circulation

    • deoxygenated blood from heart —> transport to lungs —> oxygenated blood returns to the heart

  • systemic circulation

    • oxygenated blood from the heart —> transport to body & organs —> carries deoygenated blood to heart

Crocodiles, birds, & mammals circulation

Double Circulation

Fish circulation

Single Circulation

Blood Components

• Plasma (55%)

• Erythrocytes (44%) - red blood cells

• Leukocytes (~1%) - immune system

• Platelets (~1%) - blood clotting fragments

Plasma Components

• glucose

• nutrients

• ions

• water

• waste

• hormones

• clotting proteins

Contains hemoglobin and carries oxygen and carbon dioxide

Erythrocytes

Erythrocytes in mammals

Lack a nucleus

How do platelets form a blood clot?

1. Platelets stick together and to broken vessels to form a plug

2. Platelets signals for clot formation

3. A fibrin mesh traps erythrocytes (red blood cells) and platelets to form the clot

Platelets vs. Thrombocytes

• Platelets - only mammals, no nucleus

• Thrombocytes - other vertebrates, nucleus

Neurogenic Heart

A heart beats only through electrical impulses (arthropods)

Myogenic Heart

• receives signals from pacemaker (sinoatrial (SA) node)

• pulse conducted by atrioventricular (AV) node

  • causes ventricles to contract

Cardiac Cycle

Contract & relaxation produces heartbeats

Diastole

Muscle relaxed; chamber fills

Systole

Muscle contracted; chamber empties

Blood Pressure

Force pushed by blood onto vessels

Pressure measurement

(systolic/diastolic)

• Highest - ventricular systole

• Lowest - ventricular diastole

Electrocardiogram (ECG or EKG)

Measures voltage changes during cardiac cycle

• P wave —> atrial excitation

• QRS complex —> ventricular excitation

• T wave —> resets ventricles to resting state

Blood flow in a closed circulatory system

^{Heart → larger arteries → small arteries → arterioles → capillaries → venules → small veins → large veins → heart}

Arteries

Take blood AWAY from the heart (high pressure)

• thicker muscle

• endothelium inner lining

• larger arteries have elstain fibers

Arterioles

Distribute blood to capillaries

What are capillaries made of?

Singler layer of endothelial cells & a layer of extracellular matrix

Lymphatic System

Returns interstitial fluid to the blood

Lymphatic Capillaries

• Take up excess fluid

• Merge into larger vessels

  • empties into neck veins

Lymph Nodes

• Filters objects from lymph fluid

• Contains lymphocytes and other immune system cells

Venules

Thin-walled vessels that cary blood away from the capillaries and empties into veins

Veins

Takes blood TO the heart (low pressure)

Vasoconstriction

Decrease blood flow; increase resistance

What do arterioles do during exercise?

Arterioles dilate in muscles to increase blood flow and oxygen