Circulation

Circulatory System Components

Fluid, vessels, and heart.

Open Circulatory System

System where fluid is hemolymph and it flows through interconnected sinuses.

Closed Circulatory System

System where blood circulates in vessels and is pumped by the heart.

Types of Circulatory Systems

Open and Closed Circulatory Systems.

Hemolymph

The fluid in an open circulatory system equivalent to interstitial fluid.

Efficiency of Closed Circulatory System

Operates under high pressure, requiring more energy and providing greater efficiency.

Vertebrate Circulation Components

Heart, blood vessels, and capillary exchange.

Single Circulation (Fish)

Heart has 2 chambers: 1 atrium and 1 ventricle.

Double Circulation (Amphibians)

Heart has 3 chambers: 2 atria and 1 ventricle, with some mixing of blood.

Mammals and Birds Circulation

Heart has 4 chambers: 2 atria and 2 ventricles, with completely separate pulmonary and systemic circuits.

Heart Structure

Pumping organ with 2 muscular chambers (atria and ventricles) and surrounded by the pericardium.

Atria

Chambers of the heart that receive blood from veins.

Ventricles

Chambers of the heart that pump blood to arteries.

Valves of the Heart

Flaps of connective tissue that prevent backflow of blood.

Atrioventricular (AV) Valves

Valves that open due to blood pressure in atria.

Semilunar Valves

Valves opened by ventricular contraction that allow blood to enter the arteries.

Autorhythmic Heart

Heart capable of generating its own rhythm without external nervous system input.

Sinoatrial (SA) Node

The pacemaker of the heart located in the right atrium.

Atrioventricular (AV) Node

Responsible for transmitting impulses from atria to ventricles.

Bundle Branches

Pathways that transmit the impulse to the heart apex.

Purkinje Fibers

Fibers that spread impulses throughout the ventricles, leading to contraction.

Baroreceptors

Sensors that detect changes in blood pressure and regulate heart rate.

Sympathetic Nervous System

Increases heart rate and strength of contractions.

Parasympathetic Nervous System

Decreases heart rate.

Epinephrine

Hormone released from adrenal medulla that increases heart rate.

Blood Vessel Structure

Composed of three layers: endothelium, smooth muscle, and connective tissue.

Arteries

Vessels that carry blood from the heart to organs.

Capillary Function

Site of exchange between blood and tissues.

Capillary Structure

Consists of two layers: endothelium and basal lamina.

Veins

Vessels that carry blood from organs back to the heart.

Mechanism of Exchange in Capillaries

Allows diffusion of nutrients, ions, gases, and wastes.

Interstitial Fluid

Fluid that surrounds cells, derived from plasma.

Antagonistic Forces in Capillary Exchange

Blood pressure and osmotic pressure work against each other during fluid exchange.

Lymphatic System Function

Transfers interstitial fluid to blood, absorbs lipids, and defends against disease.

Lymph

Watery fluid derived from interstitial fluid within lymph vessels.

Capillary Bed

Networks of capillaries that infiltrate tissues for exchange.

Blood Pressure

Force exerted by circulating blood on the walls of blood vessels, important for fluid exchange.

Fluid Exchange Mechanisms

Occurs via diffusion through capillary walls, driven by differences in pressure.

Return of Fluid to Capillaries

Not all fluid returns; variation depends on the region of capillary.