L31+circ+_+electric+preview+19++apr+2010[1].ppt

* Circulatory system * In closed circulatory systems, blood is completely contained within blood vessels and flows in a continuous circuit through the body under pressure generated by the heart. Because blood in a closed system is confined to vessels, the system can generate enough pressure to maintain a high flow rate, and Blood flow can also be directed in a precise way. Regulatory systems can direct blood to specific vessels and thus to specific locations. The basic function of a circulatory system is to carry blood or hemolymph into close contact with every cell in the body. * one or more pumps called hearts; tough, thick-walled tubes called arteries that carry blood away from the heart under high pressure, to arterioles; small vessels called capillaries whose walls are just one cell thick, allowing the exchange of gases and other molecules with tissues in networks called capillary beds; vessels called venules and veins that return blood to the heart under low pressure A closed circulatory systems consist of: Fish Two circulatory loops 1 circuit 2-chambered heart Frogs Gills Lung Turtles, lizards 2 circuits 3-chambered heart Lung 2 circuits ?5-chambered? heart Crocodiles Lung 2 circuits 4-chambered heart Birds Lung 2 circuits 4-chambered heart Mammals Lung 2 circuits 4-chambered heart Body Body Body Body Body Body Three-chambered heart Ventricle divided into chambers A ? Atrium V ? Ventricle A V A V A A V A A V A V A V A V A V A V Evolution of the Vertebrate Heart and Circulatory System Fish have a two-chambered heart and single circulatory circuit to both gills and the rest of the body. Fish Two circulatory loops 1 circuit 2-chambered heart Frogs Gills Lung Turtles, lizards 2 circuits 3-chambered heart Lung 2 circuits ?5-chambered? heart Crocodiles Lung 2 circuits 4-chambered heart Birds Lung 2 circuits 4-chambered heart Mammals Lung 2 circuits 4-chambered heart Body Body Body Body Body Body Three-chambered heart Ventricle divided into chambers A ? Atrium V ? Ventricle A V A V A A V A A V A V A V A V A V A V Evolution of the Vertebrate Heart and Circulatory System Tetrapods evolved two separate pumping circuits serviced by at least three chambers: Pulmonary circulation is a lower-pressure circuit to the lungs. Systemic circulation is a higher-pressure circuit to the rest of the body. * Valves Atrioventricular valves prevent blood from flowing back into the atria when the ventricles contract. Semilunar valves prevent blood from flowing back into the ventricles * Vessels: structure & function Vessels: Structure & Function The walls of both arteries and veins have three similar layers; capillaries have one Structural differences correlate with the different functions of arteries, veins and capillaries. Arteries have thicker & more elastic outer and middle layers than veins; accommodates high and uneven pressures and flows * Vessels: structure & function Vessels: Structure & Function The walls of both arteries and veins have three similar layers; capillaries have one Structural differences correlate with the different functions of arteries, veins and capillaries. Veins convey blood back to the heart at low velocity and pressure, mainly as a result of muscle action * Vessels: structure & function Vessels: Structure & Function The walls of both arteries and veins have three similar layers; capillaries have one Structural differences correlate with the different functions of arteries, veins and capillaries. Capillaries consist only of endothelium and its basement membrane; facilitates exchange of substances between the blood and the interstitial fluid that bathes the cells. Pressure Differences in Capillaries Create Interstitial Fluid and Lymph Interstitial fluid Excess fluid in interstitial space enters lymphatic duct Lymph leaves tissue Blood enters capillary from arteriole (a small artery) Net pressure 10 mm Hg out Osmotic pressure 22 mm Hg Blood pressure 32 mm Hg Capillary Fluid leaves Blood leaves capillary to venule (a small vein) Net pressure 7 mm Hg in Osmotic pressure 22 mm Hg Blood pressure 15 mm Hg Fluid returns Lymphatic duct Mechanisms of solute movement across endothelium Across endothelial cells in vesicles Passive diffusion ? e.g., O2 & CO2 Movement through clefts diffusion (some) bulk flow due to blood pressure; fluid pressure (=blood pressure) * Lymphatic system Capillary bed * The control of heart rhythm Sinoatrial node generates endogenous electrical signals that cause contraction of all heart muscle cells; cells are electrically coupled by intercalated disks between adjacent cells Semilunar valves closed AV valves open AV valves closed Semilunar valves open Atrial and ventricular diastole 1 Atrial systole; ventricular diastole 2 Ventricular systole; atrial diastole 3 0.1 sec 0.3 sec 0.4 sec Cardiac Cycle Systole: Contraction phase of the atria and the ventricles, Systole is coordinated with their relaxation phase, or diastole. One cardiac cycle consists of one complete systole and one complete diastole. Systolic blood pressure. Blood pressure measured in the systemic arterial circulation at the peak of ventricular ejection into the aorta Diastolic blood pressure. Blood pressure measured just prior to ventricular ejection Electrical Signals in Animals All animal cells have a membrane potential Neurons and muscle cells evolved a specialized use for this potential The nervous system is one of two control systems involved in whole body regulation Sensory input ? integration ? and motor output. Electrical Signals in Animals Basic Structure and Function of the Vertebrate Nervous System Nerve net Nerve ring Radial nerve Eyespot Brain Nerve cord Transverse nerve Brain Segmental ganglion Ventral nerve cord Brain Ventral nerve cord Segmental ganglia Anterior nerve ring Longitudinal nerve cords Ganglia Brain Ganglia Sensory ganglion Spinal cord (dorsal nerve cord) Brain (d) Leech (annelid) (c) Planarian (flatworm) (b) Sea star (echinoderm) (a) Hydra (cnidarian) (e) Insect (arthropod) (f) Chiton (mollusc) (g) Squid (mollusc) (h) Salamander (chordate) Diversity in Organization of Nervous Systems The three stages in the processing of information by nervous systems -- sensory input, integration, and motor output Nerve net Nerve ring Radial nerve Eyespot Brain Nerve cord Transverse nerve Brain Segmental ganglion Ventral nerve cord Brain Ventral nerve cord Segmental ganglia Anterior nerve ring Longitudinal nerve cords Ganglia Brain Ganglia Sensory ganglion Spinal cord (dorsal nerve cord) Brain (d) Leech (annelid) (c) Planarian (flatworm) (b) Sea star (echinoderm) (a) Hydra (cnidarian) (e) Insect (arthropod) (f) Chiton (mollusc) (g) Squid (mollusc) (h) Salamander (chordate) Diversity in Organization of Nervous Systems Structurally, the simplest nervous systems occur in some cnidarians that have a nerve net Most animals are bilaterally symmetrical and have a bilaterally arranged nervous system with peripheral and central elements Dendrites Cell body Nucleus Axon hillock Axon Signal direction Synapse Myelin sheath Synaptic terminals Presynaptic cell Postsynaptic cell The neuron, or nerve cell, is the basic structural and functional unit of the nervous system The three stages in the processing of information by nervous systems -- sensory input, integration, and motor output ? are handled by specialized populations of neurons CNS gathers and processes information, and issues instructions to effectors The simplest type of neural circuit regulates a reflex, or automatic response, and is called a reflex arc. Sensory neurons transmit signal to brain where it is integrated with other information.