Human Physiology Exam 3

what are the 3 principle components that comprise the circulatory ( CARDIOVASCULAR system)

• blood- a fluid connective tissue containing water, solutes, and cells that fills the tubes

• blood vessels or vascular system - set of interconnected tubes

• blood flow

• the heart - the pump

which systems is the cardiovascular system impacted by

endocrine

nervous

urinary

blood dopping

an illicit method of improving athletic performance by artificially boosting the bloods ability to bring more oxygen to muscle

blood consists of what

plasma and formed elements

plasma composition 

• 46-63%

• plasma proteins 7

• other solutes 1

• water 92%→ transports organic and inorganic molecules, forced elements, and heat 

Plasma proteins

• albumin 60%- osmotic pressure, transport lipids, hormones, steroids

• globulins - 35% transport immunoglobins( antibodies) and other globins

• fibrinogen 4% essential for clotting

  • regulatory <1% enzymes, proenzymes, hormones

other solutes in plasma

• electrolytes- eg plasma salt

• organic nutrients eg lipids, carbs, amino acids

• organic wastes- urea, creatine, bilrubin

formed elements components

platelets and wbc’s 0.1%

rbc’s 99.9%

Platelets

fragments of megakaryotcytes critical for clotting 

Leukocytes

• defense against infection

• Neutrophils 50-70

• Lymphocytes 20-30

• Monocytes 2-8

• Eosinophils 2-4

• Basophils <1

NEVER LET MONKEYS EAT BANANAS!

Erythrocytes- rbc’s

delivers O2 and removes CO2

Neutrophils 

phagocytes and their production and release from the bone marrow increases during infection 

• 1st to arrive, 1st to leave 

  • soldiers 

Lymphocytes

comprised of T and B lymphocytes that protect against specific pathogens, including viruses, bacteria, toxins, and cancer cells. some directly attack pathogens and others secrete antibodies that begin the process of destruction

monocytes

phagocytes that circulate in the blood for a short time after which they migrate into tissues and organs and develop into macrophages

eosinophils 

fights off invasions by eukaryotic parasites, they either release toxins chemicals that kill parasites or they phagocytize the parasites. protects from allergens/allergies 

basophils

secretes an anticlotting factor called heparin at the site of infection which helps the circulation flush out of the infected site, they also secrete histamine to attract infection fighting cells and proteins to the sight

macrophages

large phagocytes capable of engulfing viruses and bacteria

what does a complete blood count provide

detailed info about blood contents

WBC, RBC

number of white or red blood cells per volume blood analyzed

HGB

mass of hb found in a given volume of blood

HCT

hematocrit

MCV

mean corpuscular volume, approximates size of a typical rbc

MCH

mean cell hb, avg amount of hb within each rbc

MCHC

mean corpuscular hb concentration, amount of hb in a packed volume of cells 

RDW

RBC distribution width , approximates fluctuation in MCV from cell to cell

PLT

number of platelets per volume blood analyzed

blood count normal range of values 

Males have more RBC, more HB ( more carry O2 capacity), but same total white count as women 

Erythrocytes

• they last about 120 days

• synthesized in the red bone marrow by a process called erthryopoiesis

• (erythropoietin - a hormone from the kidneys triggers differentiation of stem cells to erythrocytes)

• more attachment to oxygen - iron, folic vitamin b12

Anemia

decrease in the oxygen-carrying capacity of blood due to:

• a decrease in the total number of erythrocytes,a dminished concentration of hemoglobin a combination of bothicS

Sickle cell anemia

due to genetic mutation that alters amino acid in the hemoglobin chain

Anemia is caused by

• dietary defiencies of iron-defiency anemia) vitamins B12, or folic acid

• bone barrow failure due to toxic drugs or cancer

• blood loss from the body - hemorrhage

• inadequate secretion of erythropoietin in kidney disease

• excessive destruction of erythrocytes - sickle cell

Pulmonary circulation 

carries oxygen poor blood from the right ventricle to the lungs and then returns oxygen which blood to the left atrium 

Arteries carry deoxygenated blood and veins carry oxygenated

systemic circulation

carries oxygen rich blood from the left ventricle to all the organs and tissues of the body, except the lungs, and then returns to the right atrium

arteries carry oxygenated blood and veins carry deoxygenated blood

Sequence of blood vessels

arteries→ arterioles→ capillaries→ venues→ veins

how much blood in body

5L

distribution of systemic blood flow to the various organs and tissues of the body at rest 

brain 650- 13%

heart 215 4%

skeletal muscle 1030 20%

skin 430 9%

kidneys 950 20%

abdominal organs 1200 24%

other 525

rest vs vigorous exercise

rest:

• more blood in brain kidneys , GI tract, skin and other tissues

vigorous activity

• more blood in skeletal muscle

arteries and arterioles

carry blood away from heart

veins and venules 

carries blood toward the heart 

tunica intima

innermost layer, contains endothelium, runs uninterrupted through entire cardiovascular system

internal, external elastic lamina

present in only arteries

needs elasticity

tunica media 

contains smooth muscle fibers - vasoconstriction 

tunica externa

connective tissue that stabilized blood vessels

structure and function of veins

• venules- smallest of vessels carrying blood back to the heart

  • have all 3 tunics but very thin

• venues converge to form veins

  • have large lumens: blood reservoirs- or capacitance vessels

systemic veins hold more blood - biggest blood reservoir

heart- atria 

chambers through which blood flows from veins to ventricles. atrial contraction adds to ventricular filling but is not essential for it 

heart -ventricles

chambers whose contractions produce the pressures that drive blood through the pulmonary end systemic vascular systems and back to the heart

Vascular system- arteries 

low resistance tubes conducting blood to the various organs with little loss in pressure. they also act as pressure reservoirs for maintaining blood flow during ventricular relaxation

Vascular system- arterioles

major site of resistance to flow, responsible for regulating the pattern of blood flow distribution to the various organs participate in the regulation of arterial blood pressure

Vascular system capillaries

major sites of nutrient, gas, metabolic end product, and fluid exchange between blood and tissues

vascular system- venules

capacitance vessels that are sites go migration of leukocytes from the blood into tissues during inflammation and infection

Vascular system- veins 

low resistance, high capacitance vessels carrying blood back to the heart. their capacity for blood is adjusted to facilitate this flow 

Blood- Plasma

liquid portion of blood that contains dissolved nutrients, water, ions, wastes, gases, and other substances. its composition equilibrates with that one of the interstitial fluid at the capillaries

Blood- Cells

includes erythrocytes that function mainly in gas transport, leukocytes that function in immune defenses, and platelets ( cell fragments) for blood clotting

Blood Flow at Capillary cross sections/ hemodynamics physical principles of hemodynamics - BLOOD FLOW

Volume of blood moving through a vessel, tissue, organ, or entire circulation per unit of time

Blood Flow at Capillary cross sections/ hemodynamics physical principles of hemodynamics - BLOOD PRESSURE

force exerted onto a given area of the vessel wall by the blood contained within it , measured in mmHgBlood Flow at Capillary cross sections/ hemodynamics physical principles of hemodynamics -

Blood Flow at Capillary cross sections/ hemodynamics physical principles of hemodynamics - RESISTANCE (R)

Friction encounterd By blood, opposite its flow

Blood Flow at Capillary cross sections/ hemodynamics physical principles of hemodynamics - FORMULA

F= delta P/ resistance

flow

the volume of blood moved per unit and it is measured in milliliters/minutes

pressure 

the force exerted by the blood and is measured in mmHg. Blood flows from a region of higher pressure to a region of lower pressure 

resistance

describes how difficult it is for blood to flow bw 2 points at any given pressure difference . resistance is the measure of the friction that impeded flow

the basic equation relating these variables is : F= delta P/R

flow rate is directly proportional to the to pressure difference and inversely proportional to the resistance

f= 6/3= 2 f = 6/6=1

Factors that determine resistance

BLOOD VISCOSITY

• bv is the function of the friction between molecules of a flowing fluid, this is affected by water volume and the number of erythrocytes

TOTAL BLOOD VESSEL LENGTH:

• which remains constant

BLOOD VESSEL RADIUS

• dilated vessels decrease resistance while constricted vessels increase resistance

• the ratio of the blood vessels do not remain constant so this is the most important determinant of changes in resistance

resistance and poiseuille’s equation

on slides

relative compliance of arteries and veins

blood vessels exhibit compliance - ability to changes in pressure

• arteries have low compliance bur are relatively elastic

• 'veins are more compliant than arteries and not very elastic

velocity of blood flow and total cross-sectional area of a vascular bed are

inversely related

capillary blood pressure and exchange

look at slide + starling forces

starling forces - chat gpt

escribe how water moves across capillary walls because of the balance between hydrostatic pressures (pushing fluid) and oncotic/colloid osmotic pressures (pulling fluid). They explain the continual exchange of plasma and interstitial fluid—sometimes called capillary fluid dynamics.

The Four Classic Starling Forces

Force	Symbol	Tends to…	Typical Value*
Capillary hydrostatic pressure	Pc	Push fluid out of the capillary into the interstitial space	~25–35 mmHg at arteriolar end, ~10–15 mmHg at venular end
Interstitial hydrostatic pressure	Pi	Push fluid into (if positive) or out of (if negative) the capillary	≈ 0 mmHg (often slightly negative)
Plasma oncotic (colloid osmotic) pressure	πc	Pull fluid into the capillary (due to plasma proteins, mainly albumin)	~25 mmHg
Interstitial oncotic pressure	πi	Pull fluid out of the capillary toward interstitial proteins	~3 mmHg

net filtration pressure NFP

NFP= Pc+ Pi if=Pif-Pic

Pc= hydrostatic pressure of blood

Pif= hydrostatic pressure of the interstitial fluid

Pic= osmotic pressure of blood due to plasma proteins

Piif= osmotic pressure of the interstitial fluid due to the presence of protein

• if forces favoring filtration ( Pc and Piif) exceed forces that favor reabsorption ( Pif & Pic) then fluid leaves the capillaries by filtration

  • for the aggregate of capillaries in the body, the net outward force is normally slightly larger than the inward force, so there is a net filtration amounting to approx 4 Liters /day ( this number does not take include the capillaries in the kidneys). this fluid is taken up by the lymphatic system and returned to the systemic circulation

venous BP and flow

• pressure in veins is much LOWER than arteries

• mucular pump assists venous return

  • during contraction, bulging muscles compress veins forcing blood back towards the heart

• respiratory pump also assists

  • during inspiration, intrathoracic pressure decreases drawing blood towards the thoracic cavity

venules & veins

• venules have a large capacity for blood so they are called capacitance vessels. they have some permeability to macromolecules, and they are also the site of migration of leukocytes into tissues during inflammation and infection

• the walls of the veins are thinner and much more compliant than those of arteries. veins have less smooth muscle than arteries and arterioles

  • bc of their high compliance, veins are referred to as capacitance vessels that act as blood reservoirs 

varicose veins

• what is it

  • failure of venous valves allowing blood to pool in peripheral veins of legs

• causes:

  • anything that impedes venous return so pregnancy obesity or prolonged periods of standing

• symptoms

  • dilation and distention of veins sometimes causing discomfort or pain

the heart is a double pump

contraction

• decreases chamber volume

• increases chamber pressure

relaxation

• increases chamber volume

  • decreases chamber pressure

2 major divisions of circulatory system

• pulmonary circulation 

  • systemic circulation 

coordination of the beating heart

• pulmonary and systemic pumps work in parallel

• they are connected to each other and highly coordinated

• contract and relax together

• pump roughly the same volume of blood

heart has 4 chambers

2 upper chambers aka atria

2 low chambers aka ventricles

• left and right side are separated by cardiac septum

• L atrium + L ventricle = systemic pump AKA pumps oxygenated blood

• R atrium + R ventricle= pulmonary pumps AKA pumps deoxygenated blood

Pathway of blood through the entire circulatory system

right atrium

right AV valve - tricuspid

pulmonary valve 

pulmonary trunk

pulmonary arteries 

pulmonary arterioles 

capillaries of lungs 

pulmonary venules 

pulmonary veins 

L atrium 

left AV valve- bicuspid 

L ventricle 

Aortic valve

Aorta

arteries 

arterioles

capillaries 

venules 

veins 

vena cava

blood flow thru the heart and major vessels

• Deoxygenated blood enters R atrium from body through superior ( upper body) and inferior ( lower body) vena cava

• Pumped thru tricuspid valve to right ventricle

• blood exists heart through pulmonary arteries into pulmonary circulation

• O2 rich blood returns through pulmonary veins into the L atrium

• Pumped thru the mitral valve into L ventricle

  • blood exits the heart through aorta into systemic circulation

Cardiac communication

• approx 1% of cardiac cells do not function in contraction but have specialized features that are essential for normal heart excitation

• these cells construe a network know as the CONDUCTING SYSTEM of the heart and are in electrical contact w the cardiac muscle cells via gap junctions

• the conduction system initiates the heart beat and help spread an action potential rapidly throughout the heart

Sequence of Cardiac Excitation 

atrial excitation 

• SA node

• AV node 

Ventricular excitation 

• atrial relaxation

• ventricular depolarization 

Ventricular relaxation 

• repolarization 

Cardiac excitation sequence

Sa node

Internodal pathways

AV node

Bundle of His

R and L bundle branches

Purkinje Fibers

SA node

where pacemaker cells are located, generate action potentials faster than other heart cells

internodal pathways 

conducts action potentials from SA node to myocytes in the atria through gap junctions 

AV node

contains slower pacemaker cells, slows action potential conduction to allow time for an atrial refractory period

Bundle of His

Conducts action potentials from Av node to interventricular septum where it splits into L and R bundle branches

R and L bundle branches

propagate action potential through inter ventricular septum to heart apex

Purkinje fibers 

spread action potentials from apex to L and R ventricles rapidly due to their heigh proportion of intercalated discs

Action Potential in Contractile Cardiomyocytes - PHASES

resting membrane potential 

depolarization 

transient repolarization 

plateau phase

rapid repolarization

resting membrane potential

• typically bw -80mV and -90 mV ( vs skeletal muscle which is -70mV)

• created from continuous efflux of K+ thru inward rectifier potassium channels ( KIR)

• also small amounts of Ca2+ and Na+ permeability

  • Na/K/ATPase serves to maintain concentration gradients

depolarization

• similar to the process in skeletal muscle

  • voltage gated fast sodium channels Naf- are activated allowing influx of positively charged sodium ions

Transient repolarization 

• voltage gated Na channels rapidly inactivate at the peak of the action potential 

• sodium permeability decreases

• cardiomyocytes go into a refractory period

  • membrane potential begins to hyperpolarize due to transient outward current from K+ channels 

plateau phase

• voltage gated L type calcium channels CaL open brining + charged Ca2+ ions into the cell

• this is opposed by the reflex of K+ ions through delayed rectifier K channels KDR

  • 2 opp electrical forces create plateau in membrane potential

rapid repolarization

L type calcium channels close

Efflux of K+ continues thru voltage gated K channels

membrane potential repolarizes to resting state

Membrane potential recording from a ventricular muscle cell w simultaneously measured permeability to K, Ca2+, Na

These ions dont have the same permeabilities

ECG/ EKG

• electrocardiogram is a tool for evaluating the electrical events within the heart 

a typical ECG makes use of multiple combinations of recording locations on the limbs and chest - ( called ECG leads ) to

obtain as much info as possible concerning different areas of the heart

is the ECG a direct record of changes in membrane potential across indv cardiac muscle cells

NO- it is a measure of the currents generated in the extracellular fluid by the changes occurring simultaneously in many cardiac muscles

where does summary of electrical charges take place

within all cells of an entire organ

T or F ECG is not a direct measure of action potentials within indv cells 

T

P wave

current flow during atrial depolarization

QRS Complex

result of ventricular depolarization