Circulation Chapter 42

The Need for a Circulatory System? One celled organisms (bacteria) do not have a circulatory system—they rely solely on diffusion Cnidarians (hydra, jelly fish) do not have a true circulatory system- the gastrovascular cavity branch throughout the organism relying on diffusion to distribute nutrients So why do other organisms need a circulatory system?

The Basics of a Circulatory System Circulatory fluid (ie: blood) Vessels A muscular pump (ie: a heart)

Invertebrate Circulation - Open Open Circulatory System –blood and interstitial fluid (together called hemolymph) bathe organs directly, blood is pumped to the spaces (sinuses) around the organs and returns to the heart through pores called ostia ex: mollusks and arthropods Advantage: requires less energy to maintain (as compared to closed)

Open Circulatory System- the grasshopper

Invertebrate Circulation - Closed Blood is moved through blood vessels and is separate from interstitial fluid ex: earthworm, squid, octopi Advantage: more effective, faster

Closed Circulatory System – the earthworm

All Vertebrate Circulation Has: Closed circulatory system AKA cardiovascular system Heart- has atria and ventricles Vessels: have arteries, veins and capillaries, along with arterioles and venules

Parts of the Circulatory System Atria – chamber of heart that receives the blood Ventricles – chamber of heart that pumps blood out of heart—more muscular Artery – pumps blood away from heart, flows into arterioles then to capillaries Vein – capillary blood flows into venules which turn into veins, then bringing blood to the heart Capillary – very thin vessels that allow for quick diffusion

Fish Circulation Heart: one ventricle and one atria Gill Circulation: blood pumped from heart to gills where gas exchange occurs Systemic Circulation: blood from gills gets carried to all the other parts of the body

Amphibian Circulation Heart: 2 atria and one ventricle Artery out of ventricle splits into two: pulmocutaneous circuit and the systemic circuit – double circulation

Reptile Circulation Heart:3 chambers (ventricle is separated by septum to prevent mixing of blood) Pulmonary and systemic (double circulation) circuits

Mammals and Birds Heart: 4 chambered (completely separates oxygen rich and poor blood), double circulation

Vertebrate Circulation

Simple Diagram of Blood Flow through Heart Superior and inferior vena cava Pulmonary artery Pulmonary vein Aorta

Blood Flow through a Mammalian Heart

The Heart Cardiac Cycle – complete sequence of pumping and filling Systole – contraction phase of heart Diastole – relaxation phase of heart Semilunar Valves –stop backflow of blood out of heart “dub” Atrioventricular (AV)Valve – separate and stop backflow of blood between atria and ventricles “lub” Sinoatrial (SA) Node – in RA, pacemaker, coordinates contraction of atria Atrioventricular (AV) Node - receives message from SA node and contracts ventricles

The Cardiac Cycle Diastole – during relaxation phase blood flows into the atria Atrial Systole – contracts blood from atria into ventricle Ventricular Systole – contracts ventricular blood into arteries

The Control of Heart Rhythm

Blood Vessels Arteries and veins made up of connective tissue outside, smooth muscle in the middle and endothelium in the middle Arteries – pump blood away from heart, have more muscle, helps maintain blood pressure Veins – bring blood to the heart, valves, associated with the skeletal muscles Capillaries – consist of only endothelium, very thin to allow for diffusion between blood and ISF

Artery to Vein

Blood Pressure Blood Pressure – pressure blood puts on its vessels, highest in arteries Systolic – pressure in arteries when heart contracts Diastolic – pressure when heart is relaxed Stress, high sodium diet, etc. can raise blood pressure

Lymphatic System Capillaries lose fluid as they diffuse materials from blood to ISF The lymphatic system recycles this lost fluid through lymph vessels- carries fluid called lymph and returns it to circulatory system Lymph nodes are filled with WBC’s that attack viruses and bacteria Why would your lymph nodes (“glands”) be swollen when you are sick? What are the two major roles of the lymphatic system?

The Fluid of the Blood Plasma – mainly water, also contains proteins, ions, antibodies, fibrinogen, nutrients, wastes, hormones; serves to maintain osmotic balance and buffer the blood

RBC’s AKA erythrocytes Small and biconcave to allow the most surface area for oxygen transport Contain hemoglobin (contains iron) that binds to oxygen Lack nuclei and mitochondria Why is it important that RBC’s do not have mitochondria?

WBC’s AKA Leukocytes Involved in immune system Found in blood, lymph and ISF You can wait to learn these cells until next chapter!!!

Platelets Involved in clotting by serving as a physical barrier (plug) to the wound, and by secreting chemical clotting factors (prothrombin, thrombin and fibrinogen) that make fibrin (a fibrous network)

Circulatory Diseases Hemophilia – genetic disease that results in improper clotting Murmor – defect in heart valves, usually harmless Artherosclerosis – plaques narrow coronary arteries High Cholesterol – HDL and LDL Hypertension – high blood pressure Heart Attack – blockage that stops blood flow to heart, could result in death of the cardiac muscle Stroke – blockage in artery of head, result in death of nervous tissue

The Respiratory System Gas exchange – uptake of oxygen and release of carbon dioxide Need a respiratory surface- the place where gases are exchanged Respiratory surface should be high in surface area and moist COUNTERCURRENT EXCHANGE

Respiratory Adaptations Respiratory Surface/ Organism Cell Membrane/ Unicellular and Simple Animals Skin/earthworm (amphibians) Gills/aquatic organisms Tracheae/ insects Lungs and alveoli/ vertebrates

Gills as a Respiratory Surface Aquatic organisms have no problem with moisture, but water has a low oxygen content, therefore ventilation (increasing the flow) is necessary Countercurrent exchange-blood flows opposite to water flow

Countercurrent Exchange

Tracheal System as a Respiratory System Made up of air tubes which branch to the surface of every cell

Lungs as a Respiratory Surface Alveoli are interface between the respiratory system and the circulatory system – they are closely related to capillaries

Parts of Mammalian Respiratory System Nose/Mouth Larynx Trachea Bronchi Bronchiole Alveoli

Negative Pressure Breathing Pulls air into lungs (like a suction pump) Aided by the contraction of the diaphragm

Negative Pressure Breathing

Autonomic Control of Breathing Pons and medulla regulate breathing Sensors respond to pH changes – lowered pH signals increase breathing

Respiratory Pigments Carry oxygen to increase efficiency Hemocyanin- contains copper, found in arthropods Hemoglobin – contain iron, found in vertebrates