TRG Blood System

Circulatory System & The Heart TRG

State the function of arteries

State the function of arteries

moves blood at high pressure AWAY from the heart ventricles to body tissue & lungs

Outline the role of elastic and muscle tissue in arteries

elastic fibers allow arterial wall to stretch and expand through mechanism called elastic recoil, muscle fibers form rigid arterial wall to withstand high blood pressure (also can contract to narrow lumen and increase blood pressure)

State the reason for the toughness of artery walls

they need to withstand the high blood pressure

Describe the structure and function of the three layers of artery wall tissue

tunica externa: tough outer layer of collagen maintains high blood pressure

tunica media: thick layer containing smooth muscle and elastic fibers allows for contraction and stretching for pulse flow

tunica intima: smooth endothelium that forms the artery lining

Describe the mechanism used to maintain blood flow in arteries between heartbeats

at the end of the heartbeat, the arterial pressure falls to allow for the stretched elastic fibers to squeeze the blood into the lumen

Describe the structure and function of capillaries

capillaries are used to exchange materials between tissues’ cells and blood at low pressure

• has small diameter for the passage of one red blood cell at a time

• single layer of cells in wall minimizes the distance for permeable materials

• basement membrane is permeable for specific materials

• pores aid in transport of materials between tissue fluid and blood

Describe the cause and effect of diffusion of blood plasma into and out of a capillary network

cause: the capillary wall has a thin layer of endothelium cells that have a filter-like protein gel with pores; this creates a permeable membrane that enables part of the plasma to leak and form a tissue fluid

effect: fluid flows between cells in tissue, allows cells to absorb useful substances and excrete waste

State the function of veins

transport blood from capillary networks to the atria in the heart

Outline the roles of gravity and skeletal muscle pressure in maintaining flow of blood through a vein

gravity assists blood flow in veins, skeletal muscle contraction causes blood flow out of the contraction area and helps move blood flow against gravity and prevent back flow

Outline the structure and function of a pocket valve

consists of three cup-shaped flaps of tissue

allows blood to flow in one direction to ensure correct blood circulation

Compare the circulation of blood in fish to that of mammals

fish: single circulation, blood pumped at high pressure to the gills to be oxygenated, then the blood flows relatively slowly to the rest of the organs before returning to the heart

mammals: lungs are supplied with blood from a separate circulation

Explain the flow of blood through the pulmonary and systemic circulations

pulmonary: to and from the lungs, receives deoxygenated blood from the systemic circulation

systematic: to and from all other organs including the heart, receives oxygenated blood from the pulmonary circulation

Explain why the mammalian heart must function as a double pump

the heart needs to deliver blood under different pressures separately to the two circulations

Outline the role of cells in the sinoatrial node

direct the heart contractions at about 60-100 cardiac contractions per minute

State the reason why the sinoatrial node is often called the pacemaker

the sinoatrial node or SA node directs each heartbeat which sets the pace for the heartbeats

Describe the propagation of the electrical signal from the sinoatrial node through the atria and ventricles

1. sinoatrial node sends electrical impulse that stimulates myocardium contraction

2. node at the junction between the atrium and the ventricle is stimulated (called the atrioventricular or AV node)

3. sends signal to the septum via a nerve bundle (called bundle of His)

4. the bundle of His innverates the Purkinje fibers in the wall to cause a ventricular contraction

Outline the structures and functions of nervous tissue that can regulate heart rate

a region in the medulla of the brain called the cardiovascular center sends signals to the sinoatrial node for the beating of the heart

• sympathetic nerve can increase heart rate

• parasympathetic nerve or vagus nerve can decrease heart rate

Describe factors that will increase heart rate

• sympathetic nerve can release the neurotransmitter called noradrenaline to increase heart rate

• in preparation for vigorous physical activity, adrenal glands above the kidneys can release adrenaline aka epinephrine to increase heart rate

Describe factors that will decrease heart rate

the parasympathetic nerve or vagus nerve can release the neurotransmitter called acetylcholine to decrease heart rate

Outline conditions that will lead to epinephrine secretion

• vigorous physical activity

• threat/opportunity

• adventurous sports

Explain the effect of epinephrine on heart rate

increases heart rate by activating the same chemical pathways as noradrenaline (a neurotransmitter from the sympathetic nerve)