A+P L Midterm Pt 4 Flashcards
Trace the normal pathway of an electrical impulse through the heart’s conduction system.
SA Node (generates impulse)
Atria (contract)
AV Node (delays impulse)
Bundle of His (transmits signal to ventricles)
Right and Left Bundle Branches (carry the impulse to ventricles)
Purkinje Fibers (distribute impulse to ventricles, causing contraction)
Describe the effects of epinephrine, norepinephrine, glucagon, and thyroid hormones on heart contractility.
Epinephrine:
Increases heart contractility by stimulating beta receptors, making the heart beat stronger and faster (enhances cardiac output).
Norepinephrine:
Increases heart contractility by also stimulating beta receptors, leading to stronger heart contractions and increased heart rate.
Glucagon:
Increases heart contractility by increasing the levels of cyclic AMP (cAMP), which enhances heart muscle strength.
Thyroid Hormones (T3 and T4):
Increase heart contractility by upregulating the number of beta receptors, making the heart more responsive to catecholamines (like epinephrine and norepinephrine). This leads to stronger heart contractions.
Trace the path of a drop of blood from the left ventricle of the heart to the right wrist and back.
Left Ventricle → Blood is pumped from the left ventricle through the aortic valve into the aorta.
Aorta → The blood travels through the ascending aorta, then the aortic arch.
Brachiocephalic Artery → Blood moves into the brachiocephalic artery, which branches into the right subclavian artery.
Right Subclavian Artery → The blood flows through smaller arteries, eventually reaching the radial artery or ulnar artery in the right wrist.
Right Wrist → Blood moves through the veins (such as the radial vein or ulnar vein) back toward the heart.
Superior Vena Cava → The blood enters the superior vena cava and returns to the right atrium.
Trace the path from the left ventricle to the dorsum of the right foot and back to the right atrium.
Left Ventricle → Blood is pumped from the left ventricle through the aortic valve into the aorta.
Aorta → The blood travels down the descending aorta.
Abdominal Aorta → Blood continues through the abdominal aorta and eventually branches into the common iliac arteries.
External Iliac Artery → Blood moves into the external iliac artery and continues into the femoral artery.
Femoral Artery → The blood flows into the popliteal artery, then into smaller arteries in the dorsum of the foot.
Dorsum of the Foot → Blood moves through veins like the dorsal venous arch and into the great saphenous vein.
Inferior Vena Cava → Blood moves through the veins and ultimately returns to the right atrium through the inferior vena cava.
Describe the pathway a drop of blood follows from the right atrium to the left atrium. What is this circuit called?
Right Atrium → Blood enters the right atrium from the superior and inferior vena cava.
Right Ventricle → The blood is pumped from the right atrium into the right ventricle.
Pulmonary Artery → Blood is pumped from the right ventricle through the pulmonary valve into the pulmonary artery.
Lungs → The blood travels through the pulmonary arteries to the lungs where it gets oxygenated.
Pulmonary Veins → Oxygenated blood returns from the lungs through the pulmonary veins.
Left Atrium → The oxygenated blood enters the left atrium.
What is the function of the fluid within the pericardial sac?
Lubrication – Reduces friction as the heart beats.
Cushioning – Protects the heart from physical shock.
Prevents Adhesion – Keeps the heart from sticking to the sac, allowing it to move freely.
Define systole, diastole, stroke volume, and the cardiac cycle.
Systole – The phase when the heart contracts and pumps blood out.
Diastole – The phase when the heart relaxes and fills with blood.
Stroke Volume – The amount of blood pumped by the heart in one beat.
Cardiac Cycle – The complete cycle of one heartbeat, including both systole and diastole.
Compare and contrast the structural differences between small, medium, and large veins and arteries.
Arteries:
Large Arteries (e.g., aorta):
Thick, elastic walls to handle high pressure from the heart’s pumping.
Thick tunica media (muscle layer) for strength and elasticity.
Medium Arteries (e.g., femoral artery):
Thicker walls than small arteries but less elastic than large arteries.
The muscle layer is still significant for regulating blood flow.
Small Arteries:
Thinner walls than medium arteries.
Less elastic tissue, more muscle for regulating blood flow to smaller areas.
Veins:
Large Veins (e.g., vena cava):
Thin walls are compared to arteries because they carry blood under low pressure.
Wide lumen for easy blood flow back to the heart.
Valves to prevent backflow of blood.
Medium Veins (e.g., femoral vein):
Thinner walls and less muscular than large arteries.
Valves are present to help move blood upwards toward the heart.
Small Veins:
Thin walls, much thinner than arteries.
Valves to ensure blood flows in one direction.
Describe the structure of capillary walls and explain how it facilitates their function.
Capillary walls are very thin and made of a single layer of endothelial cells. This structure helps their function in several ways:
Thin walls: Allows easy exchange of gases, nutrients, and waste products between blood and tissues.
Porous: Small openings (pores) between cells enable substances to pass through.
Small diameter: Capillaries are narrow, so red blood cells move through in a single file, making it easier for exchange.
Why are artery walls significantly thicker than those of veins?
Higher Pressure: Arteries carry blood pumped directly from the heart, which creates high pressure. Thicker walls help them withstand this pressure.
Elasticity: Arteries need to be flexible to expand and contract with each heartbeat, which requires thicker, more elastic walls.
Muscle Layer: Arteries have a thicker muscle layer to help regulate blood flow by constricting or dilating.
Identify three key factors that promote venous return to the heart.
Skeletal muscle contraction: Muscles squeeze veins, pushing blood toward the heart.
Valves in veins: Prevent blood from flowing backward, ensuring it moves in one direction.
Breathing: Inhalation creates pressure changes that help draw blood back to the heart.
Two main factors influence blood pressure: cardiac output and peripheral resistance. Name two factors that increase cardiac output and two factors that increase peripheral resistance.
CO
Increased heart rate: When the heart beats faster, more blood is pumped out.
Increased stroke volume: When the heart pumps more blood with each beat, cardiac output increases.
PR
Vasoconstriction: When blood vessels narrow, it increases resistance to blood flow.
Increased blood viscosity: Thicker blood creates more resistance to flow.
Why is blood flow in arteries pulsatile, whereas blood flow in veins is relatively steady?
Blood flow in arteries is pulsatile because:
Arteries receive blood directly from the heart’s pumping, causing a surge of blood with each heartbeat, creating a pulse.
Blood flow in veins is steady because:
Veins carry blood back to the heart under lower pressure, and the blood flow is not affected by heartbeats. It moves smoothly and steadily.
