Unit 3 Study Guide

Alveolus

A tiny air sac in the lungs where gas exchange occurs.

Aortic Valve

Valve that regulates blood flow from the heart into the aorta.

Arteriole

A small branch of an artery leading into capillaries.

Artery

A blood vessel that carries oxygenated blood away from the heart.

Atrioventricular Node

A cluster of cells that serves as a gatekeeper for electrical impulses between the atria and ventricles.

Atrium

The upper chamber of the heart that receives blood. (two atria, thin-walled)

Autorhythmic cells

“Pacemaker cells,” Specialized heart cells in the right atrium that generate their own electrical signals.

Bicuspid Valve

Also known as the mitral valve, it has two flaps and is located between the left atrium and left ventricle.

Blood

Fluid that circulates in the heart and vessels, delivering nutrients and oxygen.

Blood Vessels

The network of tubes through which blood flows, including arteries, veins, and capillaries.

Bohr Effect

The physiological phenomenon where increased carbon dioxide and decreased pH result in hemoglobin releasing oxygen more readily.

normal pH, normal temp = high affinity

low pH, high temp = low affinity

CO2 and lactic acid promote off-loading of O2

Bronchiole

Small air passages that lead to the alveoli in the lungs.

Bronchus

The main passageway that directs air into the left and right lungs.

Capillary

The smallest blood vessels where nutrient and gas exchange occurs.

Cardiac Muscle

Specialized muscle tissue of the heart that is autorhythmic.

Cardiomyocyte

A cardiac muscle cell responsible for the contraction of the heart, have a single nucleus, linked to neighbors by gap junctions and are striated and branched

Chemoreceptors

Sensory receptors that respond to chemical stimuli, particularly in blood gases.

Deoxygenated

Referring to blood that has a low level of oxygen, returning from the body and pumped toward the lungs/heart

Diastole

The phase of the heartbeat when the heart muscle relaxes.

Electrocardiogram

A recording of the electrical activity of the heart.

Endocardium

The inner lining of the heart chambers, forms valve structures.

Endothelial Cells

Cells that line the blood vessels, playing a role in vascular health.

Epiglottis

The flap of cartilage that covers the windpipe during swallowing.

Erythrocyte

A red blood cell that carries oxygen to body tissues.

Gap Junctions

Intercellular connections that allow for rapid electrical communication between heart cells.

Globin

The protein portion of hemoglobin responsible for binding oxygen.

Heart

The organ that pumps blood throughout the body.

Hematocrit

The proportion of blood volume occupied by red blood cells.

Heme Complex

The iron-containing structure in hemoglobin that binds oxygen, a human Hb has four of these and can carry 4 O2 molecules

Hemoglobin

The protein in red blood cells that carries oxygen.

Inferior Vena Cava

The large vein that carries deoxygenated blood from the lower body (below the arms) to the heart.

Iron

A mineral essential for the formation of hemoglobin.

Larynx

The voice box that also plays a role in protecting the trachea against food aspiration.

Leaky Na+ Channels

Ion channels that allow sodium ions to enter cells, influencing heart rhythm.

Myocardium

The muscular middle layer of the heart wall responsible for contractions.

Myoglobin

An iron-containing, oxygen-binding protein found in muscle tissue, greater affinity for O2 than Hb, which promotes transfer better

Oxygenated

Referring to blood that is rich in oxygen, typically leaving the lungs.

P Wave

The part of an electrocardiogram that represents atrial depolarization.

Pericardium

The protective fibrous sac/membrane surrounding the heart, fluid-filled.

Plasma

The liquid component of blood that carries cells and proteins.

Precapillary Sphincter

A band of smooth muscle that controls blood flow into capillaries.

Pulmonary Valve

Valve that regulates blood flow from the right ventricle to the pulmonary artery.

Pump

The function of the heart to circulate blood.

QRS Complex

The depiction of ventricular depolarization on an electrocardiogram.

Red Blood Cell

Another term for erythrocyte, responsible for transporting oxygen.

Sinoatrial Node

The natural pacemaker of the heart that initiates the heartbeat.

Smooth Muscle

Involuntary muscle type found in the walls of blood vessels and organs.

Stroke Volume

The amount of blood pumped by the heart with each beat.

Superior Vena Cava

The large vein that carries deoxygenated blood from the upper body (head and arms) to the heart.

Systole

The phase of the heartbeat when the heart muscle contracts.

T Wave

The part of an electrocardiogram that represents ventricular repolarization.

Trachea

The windpipe that carries air to and from the lungs.

Tricuspid Valve

Valve that regulates blood flow between the right atrium and right ventricle.

Vasoconstriction

The narrowing of blood vessels, which increases blood pressure.

Vasodilation

The widening of blood vessels, which decreases blood pressure.

Vein

A blood vessel that carries deoxygenated blood back to the heart.

Ventricle

The lower chamber of the heart that pumps blood out of the heart. (two, thick-walled)

Venule

Small blood vessel that collects blood from capillaries.

Major arteries

aorta and pulmonary arteries carry blood away from the heart

Major veins

vena cava and pulmonary veins return blood to heart

oxygenated blood

blood rich in oxygen, returning from the lungs and pumped toward the body.

flow of deoxygenated blood in the human heart

deoxy blood from body enters the right atrium, arrives at RA via superior vena cava & inferior vena cava, then deoxy blood moves from RA to right ventricle through the tricuspid valve, then deoxy blood gets pumped to the lungs via the pulmonary artery through the pulmonary valve, then is oxygenated in the lungs

flow of oxygenated blood in the human heart

oxygenated blood from the lungs enters the left atrium, transported to LA from lungs via pulmonary veins, oxygenated blood moves from LA to left ventricle, valve between LA and LV is the bicuspid valve, oxygenated blood gets pumped to the body via the aorta, valve between LV and aorta is the aortic valve, blood becomes deoxygenated in the body

action potential in autorhythmic cardiomyocytes

action potential in contractile cardiomyocytes

autonomic control of arteriolar tone (vasoconstriction)

sympathetic control, norepinephrine maintains arteriolar tone. when norepinephrine is released by a neuron, it binds to alpha receptors and causes vasoconstriction.

Epinephrine released by adrenal medulla binds:
• α receptors = vasoconstriction
• β receptors = vasodilation

autonomic control of autorhythmic cardiomyocytes

Parasympathetic fibers reach the heart via the Vagus nerve and act on the autorhythmic cells through the neurotransmitter acetylcholine.

components of blood

~58% plasma, <1% white blood cells, 42% packed red cell volume

• H2O

• Ions (Na+, Cl-, K+, Ca2+)

• Dissolved gases (O2 and CO2)

• Sugars (glucose)

• Amino acids, proteins, N waste

• Various cells of the immune system (lymphocytes, macrophages; white blood cells)

• Platelets (clotting factors)

• Red blood cells

Electrical conduction throughout the heart

pacemakers set the heart rate, electrical signals coordinate contraction; internodal pathway from sinoatrial node to atrioventricular node; routes direction of signals so heart contracts from apex to base

formation of red blood cells

RBCs are formed in the bone marrow from stem cells, takes 7 days, mature RBCs are unnucleated, and live in blood for 120 days

hierarchical organization of blood vessels

arteries → arterioles → capillaries → venules → veins

nervous control of breathing

neurons projecting from the medulla oblongata controls ventilatory muscles, chemoreceptors that can detect pH, PO2, PCO2, initiate sensory signals towards medulla oblongata,; increases PCO2 is a primary trigger for breathing

“Onloading” of O2 onto hemoglobin in alveoli

• CO2 diffuses much faster than O2

• CO2 is removed, blood pH increases

• blood temp decreases via proximity to air in alveoli

• increase in pH and decrease temperature at alveoli promotes O2 on-loading to Hb (“Bohr Effect”)

“Offloading” of O2 from hemoglobin

• a decrease in pH and increase temperature at target tissue promotes O2 off-loading from Hb (“Bohr Effect”)

organization of a capillary bed

path of inhaled air

→ air is inhaled via the nasal passages or the mouth
→ inhaled air enters windpipe when the epiglottis is
open, arriving at the larynx
• epiglottis: a muscular flap preventing food from entering
trachea
→ air moves to trachea, which branches into two
bronchi leading to each lung
→ each bronchus branches into smaller bronchioles
→ a bronchiole ends at an alveoli
• alveoli: air sac, site of gas exchange

path of inhaled O2

→ dissolves in alveolar epithelial surface fluid

→ crosses lung epithelial cell

→ crosses endothelial cell, enters capillary

→ enters red blood cell, binds to hemoglobin

sounds of a heartbeat

“Lub” = atrioventricular valves closing (ventricular systole)
“Dup” = semilunar valves closing (ventricular diastole)

structure and organization of cardiomyocytes

• striated: the contractile fibrils (containing actin and myosin) are aligned in parallel bundles

• branching, and linked to neighbors by gap junctions

structure of blood vessels

1. Endothelium: inner layer of cells lining all blood vessels

2. Vascular smooth muscle: surrounds endothelial layer, contraction/relaxation drives vasoconstriction/dilation

3. Connective tissue: outer layer that provides supports and anchors blood vessels within tissues

systolic and diastolic blood pressure

• sys: arterial blood pressure during ventricular systole, cardiac muscle contraction

• dia: arterial blood pressure during ventricular diastole, cardiac muscle relaxation

vasoconstriction vs vasodilation

narrowing of bllood vessel diameter vs expanding of blood vessel diameter

properties of arteries

• thickest blood vessel walls (all layers present)

• site of highest blood pressure

• carries blood from heart

properties of arterioles

• less elastic and more muscular

• divergent pattern of flow

• site of variable resistance to direct blood flow

properties of capillaries

• smallest vessels (only endothelial cells)

• most abundant blood vessel type in body

• primary site of material exchange

properties of venules

• some connective tissue

• convergent pattern of flow

properties of veins

• not as thick as arteries (all layers present)

• contains one-way valves

• returns blood to heart