exam IV A&P

Cardiovascular system

the cardiovascular system is composed of three parts:

  • Heart

    • the pump that moves blood throughout the body

    • made primarily of cardiac muscle

  • Blood vessels

    • tubes that carry blood and allow exchange of nutrients and waste

    • Arteries carry blood away from the heaart

    • Veins carry blood back to the heart

    • capillaries connect between the arteries and veins

  • Blood

    • cells- RBC’s, WBC’s, platelets (cell fragments)

    • fluid-plasma

  • Tissue types

    • cardiac muscle

    • non-contractile autorhythmic cells ( conduction system)

    • epithelial cells ( inner lining)

    • pericardial cells ( outerlining)

Apex: pointed end of the heart

  • shifted towards left side

  • points down/ left within the chest

Base: rounded cranial end of heart

  • shifted towards right side

Pericardium (pericardial sac)

  • protects heart

  • bag around heart ( fibrous, not stretchy)

  • keeps heart separated from lungs, diaphragm

inside sac= visceral pericardium

Outside of sac= Parietal pericardium

  • filled with pericardial fluid to reduce friction woth each heart beat

Myocarditis: inflammation of the heart

Pericarditis: inflammation of the pericardium

Heart: Tissue layers

Epicardium: outermost membrane layer ;AKA visceral pericardium

Myocardium: middle layer made up of cardiac muscle cells

Endocardium: inner layer that lines the inside of the heart chambers

  • epithelial tissue, single layer of cells

  • also lines the valves of the heart

Heart: types of muscle

Three main types of muscle tissue
1. Skeletal Muscle:
• Moves bones
• Multiple nuclei (100 +)
• Striated in appearance
• Requires motor neuron innervation:
“voluntary”
2. Cardiac Muscle:
• Moves blood
• Single nucleus
• Striated in appearance
• Modified by nerve innervation (but not
required)- “involuntary”
3. Smooth Muscle:
• Moves organs/blood vessels/tissues
• Single nucleus
• Non-striated in appearance
• Modified by nerve innervation (but not
required)- “involuntary”

Muscle fiber anatomy

• Cell Membrane sarcolemma
Interior units myofibrils
• Transverse Tubules (T-tubules) are
extensions of sarcolemma interior of
the cell that wrap around myofibrils
• Allows electrical signals (action potentials)
to spread quickly into the interior of the
muscle cell
• Electrical signal is required for every muscle
contraction
• The sarcoplasmic reticulum stores and
releases Ca++ ions into the muscle fiber
• Ca++ ions trigger the myofilaments to
contract
• SR wraps around myofibrils to allow fast
access to the Ca++
• Parts of the SR that border the T-tubules
are called the terminal cisternae
• Neuron Sarcolemma T-tubules
SR Ca++ release contraction
Cardiac Muscle and conduction system

Myocarium: cardiac muscle

  • 2 types of cardiac muscle

    • Myocaardial contractile (99% of cells)

  • Myocaardial conduction(1% of cells)

Four Characteristics of myocardial contractile cells

1) Has striated muscle fibers

  • Striated- organized into sarcomeres

Sacromere: unit of cell that contracts

  • shorter than skeletal musvle

  • thinner diameter

  • fibers have branching shape

  • Intercalated disks: gap junctions that connect muscle fibers ( allows the spread of Ca2+ from fiber to fiber)

Muscle Contraction

Sarcomere is the Contractile unit of the muscle fiber

Two main anatomic components

1) Thin filament=actin

  • troponin: lock that binds Ca+)

  • Tropomyosin: Covers myosin bindingg sites until Ca2+ is present)

2) Thick filament = myosin

Contraction of sarcomere

  • relaxed sarcomere: resting state between thick and thin filament

  • Contracted Sarcomere: The thin filaments are pulled together and shorten the sarcomere

Contraction: Occurs when actin and myosin form a cross bridge

  • calcium is key to contraction (binds to Troponin)

  • Allows actin and myosin to form the cross bridge and muscles to contract

  • Requires ATP to release cross bridge and reset cycle contrations

ALL muscle requires Ca to contract

Cardiac muscle is involuntary

Voluntary muscle (skeletal muscle)

  • requires signal from motor neuron

INvoluntary muscle ( cardiac and smooth muscle)

  • does NOT use a motor neuron

  • Ca release is controlled by pacemaker/ autorhythmic cells

    • can be modified by autonomic input

  • can be modified by hormones

  • Ca can also spread from neighbors through intercalated disks

Cardiac muscle is Aerobic

  • aerobic muscle requires a constant supply of oxygen and glucose

  • lots of mitichondria ( red muscle) and myoglobin protein

  • myoglobin: holds spare oxygen to help with ATP production

  • Heart reveives about 5% of all cardiac output

Cardiac ischemis: no oxygen to heart

Myocardial infarcton: when heart tissue dies

Two ways to depolarize Cardiac muscle: AP and spread of Ca

cardiac muscle relaxation:

  1. Ca gets reabsorbed

  2. Ca gets exported out ofthe ell by Na/ Ca exchange pump

  3. Noca=relaxation of cardiac muscle

Chambers of the heart

Top: right and left atrium

  • atria receive blood from large veins and fill ventricles

  1. Right atrium receives blood from

    • inferior and superior vena cava

    • coronary sinus

  2. Left atrium receives blood from:

    • left/right pulmonary veins

Atria contraction= blood to the ventricles

  • leaves through the left abd right AV valves

    • right AV= Tricuspid

    • Left AV= Bicuspid

Fossa ovalis: closed hole between L/R atria

Bottom: left and right ventricle

  • receive blood from atria

  • pump blood out into the large arteries

1. Atria receive blood and fill the
ventricles
2. Ventricles generate blood pressure and
send blood out to the whole body
• Systolic = pressure created when
ventricles contract
• Diastolic = pressure at which semilunar
valves remain closed

Blood exits ventricles through semilunar valves

  • right ventricle: pulmonary valve

  • Left ventricle: Aortic valve

Two types of cardiac muscle cells
• Myocardial contractile cells (99% of cells)
• Myocardial conducting cells (1% of cells)
• Myocardial conducting cells
• Non-contractile cells (do not
contract)
• Autorhythmic = pacemaker cells
• Provide rhythm of action potentials
• Spread through the heart to create a
synchronized contraction
• Conduction system of the heart:
1. Sinoatrial (SA) node = sets the normal
cardiac heart rate
2. Internodal cells
• Connect SA to AV node
3. Atrioventricular (AV) Node
4. AV bundle (Bundle of His)
5. Left and right bundle branch
6. Purkinje Fibers

Regulation of heartbeat

Conduction pathway
1. Sinoatrial (SA) node is the normal
pacemaker
• Fastest rate of autorhythmicity
2. Atrial excitation (Bachman’s
Bundle)
3. Internodal cells: connect SA node to
AV node
4. Atrioventricular (AV) node
transmits impulses between the
atria and the ventricles
• Slower rate of autorhythmicity
• Impulse is delayed about 0.1 sec
5. Ventricular excitation
• Impulse passes down the bundle
of His in the interventricular
septum L and R bundle
branches
• Purkinje fibers extend through the
ventricular myocardium

Pacemaker cells

Autorhythmic pacemaker cells generate a
repeating pattern of action potentials
• These cells have a series of sodium leak ion
channels that drive this pattern
1. Allow a normal and slow influx of sodium ions
2. Causes the membrane potential to rise:
raises from −60 mV (resting) –40 mV
(cardiac threshold potential)
3. Creates “spontaneous depolarization”
4. Opens voltage-gated Ca++ channels
5. Ca++ enters depolarizing +10 mV
6. Ca++ ion channels close, K+ channels open
• Efflux of K+ repolarization
7. When membrane potential reaches −60 mV, the
K+ channels close and Na+ channels open, and
the cycle begins again
8. Repeats until death of the heart


Implanted pacemaker
• Surgically put into people with damage to
the conducting system of the heart
• Heart blocks
• Arrythmias
• Heart Failure
• Provide electrical signal to keep the heart
beating

Arteries: carry blood away from the heart

veins: carry blood towards the heart

capillaries: connect arteries and veins

Cardiac cycle

The heart contracts as a unit
• Left and right atrium contract
together
• Left and right ventricles contract
together

The coordinated actions of the heart
is called the “cardiac cycle”
• Diastole = relaxed cardiac muscle
• Systole = contracting cardiac
muscle
• Cardiac cycle: Steps
1. Heart filling (Cardiac Diastole)
2. Atria muscles contract (Atrial
Systole)
3. Ventricle muscles contract
(Ventricular Systole)
4. Heart filling (Cardiac Diastole)

ECG

Coordinated by the conduction system
of the heart
• The electrical activity of conduction
through the heart can be measured by
an ECG (electrocardiogram)
1. P wave = atrial depolarization
• SA node signal into atria
• Atria muscles contract
2. QRS complex = ventricular
depolarization
• AV node bundle of His Purkinje
fibers
• Ventricular muscles contract
3. T wave = ventricular
repolarization
• Muscles all relax to resting state


Cardiac cycle: Steps
1. Heart filling (Cardiac Diastole)

  • enters right atria from vena cava

  • enters left atria from pulmonary veins

  • equal volume of blood fills each side of the heart

  • heart is filled but not pressurized
    2. Atria muscles contract (Atrial Systole)


  • SA node fires (P wave of ECG)
    • Muscles of Left and Right Atria contract
    at the same time
    • Pushes all blood into the ventricles /
    pressurizes ventricles
    • Pressure in ventricles > pressure in atria
    • AV valves close = “Lub” heart sound
    • Valves closed = closed, pressurized
    chamber

    3. Ventricle muscles contract
    (Ventricular Systole)

  • AV node fires → His bundle → Purkinje
    fibers (QRS complex on ECG)
    • Ventricle muscles start contracting,
    further increasing pressure
    1. “Isovolumetric contraction”
    • While pressure in ventricle < pressure in
    arteries (blood pressure) semilunar
    valves are shut, blood stays in ventricle
    2. “Ventricular ejection”
    • When pressure in ventricle > pressure
    in arteries (blood pressure)semilunar
    valves will open
    • Blood leaves the ventricles into the
    pulmonary trunk (right) or aorta (left)
    3. When pressure in arteries > pressure in
    ventricle after ejection, SL valves slam
    shut (Dub, S2 heart sound)
    4. Heart filling (Cardiac Diastole)

  • • All cardiac muscle in atria and ventricle
    relaxes (T wave of ECG)
    • All valves are closed
    • Blood starts passively filling into atria
    again

    Normal heart sounds
    • S1 = “Lub” - AV valves snap shut
    • S2 = ‘Dub”- Semilunar valves snap shut
    Abnormal heart sounds
    • Murmur = turbulent flow between
    chambers
    • Sounds like a whooshing noise
    • Valve insufficiency leads to
    regurgitation back through a valve
    • Valve stenosis leaves some blood
    left in the chamber

    Carl Wigger’s diagram

    • Phases of Wigger’s Diagram
    1. Heart filling (Cardiac Diastole)
    • Pressure in atria and ventricles is low
    • Volume of blood in ventricle starts to
    increase
    • ECG is passive
    2. Atria muscles contract (Atrial Systole)
    • P wave
    • Atria contract, increasing atrial
    pressure
    • Ventricle volume increases to highest
    3. Ventricle muscles contract
    (Ventricular Systole)
    • First step: isovolumetric contraction
    • Second step: ventricular ejection
    4. Heart filling (Cardiac Diastole)
    • Isovolumetric relaxation
    • Then, blood starts to flow in...

    Cardiac output

  • Cardiac output (C.O.) is how much blood
    the heart pumps out each minute
    • Cardiac output = heart rate x stroke
    volume
    • Heart rate = Beats per minute
    • Stroke Volume = amount of blood
    ejected from ventricle
    • Ejection fraction = % of blood that
    gets ejected during each stroke
    • Larger animals have slower heart rates,
    but larger stroke volume


    Human heart rate: 60-100 bpm

    1. Resting heart rate: determined by the
    autorhythmic pacemaker potential of
    the SA node
    2. Changes in heart rate: modified by
    the autonomic nervous system
    • Parasympathetic slows heart rate
    • Neurotransmitter: Acetylcholine
    • Acts on SA an AV nodes
    • Sympathetic increases heart rate
    • Neurotransmitter: Norepinephrine
    • Hormone: Epinephrine

  • bind to b1- adrenergic receptors
    • Acts on nodes and throughout muscle
    • Autonomic neurons synapse around
    the base of the heart
    • Called the Cardiac Plexus


    Stroke volume = volume of blood ejected
    from the ventricle during systole
    • Volume ejected from right ventricle
    and left ventricle is the same
    • Pressure of blood ejected from left and
    right ventricles is different
    • Volume ejected = volume returning
    through the veins
    • Cardiac output = venous return
    • Ejection fraction = % of blood ejected
    from ventricle
    • End diastolic volume (EDV) = totally
    full ventricle
    • End systolic volume (ESV) = what's left
    after contraction of ventricle

Stroke volume Control

Stroke volume control:
1. Intrinsic (internal) control
• More blood flow into heart more
output from heart
• “The greater the volume of blood
entering the heart, the greater the
volume ejected”
• Frank-Starling law of the heart
2. Extrinsic (external) control
• Sympathetic nervous system
1. Enhances contractility
• Contractility = Heart “pumps
harder”
• Increases ejection fraction
increases stroke volume
2. Constricts veins
• Returns more blood to the
heart...


Preload = the stretching of the
muscle in the ventricle during Diastole
• Based on volume of blood in the
ventricles when full (end diastolic
volume, EDV)
• Muscle fibers (sarcomeres) are stretched
• More preload = higher stroke volume
2. Afterload = pressure in the ventricles
needed to open semilunar valves
• Based on the diastolic pressure of blood
in the aorta or pulmonary arteries
• Higher afterload = faster closing of valves
lower stroke volume
3. Contractility = stronger muscle
contractions of the heart muscle
• Due to increased concentration of Ca++
inside cardiomyocytes
• More contractility = more ejection
fraction = higher stroke volume

Heart disease

• Cardiomyopathy = disease of heart muscle
• Dilated CM = ventricle is enlarged
• Can be due to infection, diabetes, or idiopathic
• Weakened ventricle muscles
• Reduced ejection fraction and reduced stroke
volume
• Hypertrophic CM = heart muscle in ventricle
is thickened
• Can have a genetic basis
• In left ventricle, is usually caused by high blood
pressure
• Decreased volume of the ventricle Reduced
stroke volume
• Heart failure = syndrome in which heart is no
longer able to effectively perfuse the body
with blood
• Can be due to:
• Weakness in contracting
• High blood pressure shutting valves too fast
• Poor coordination of the heart
• Fluid backs up into the lungs, into the periphery
of the body, or both

• Blood pressure (BP) is the pressure exerted
by blood on the walls of a blood vessel
• Pressure pushes blood through the body
• Blood flows from High Pressure Low
Pressure
• Highest pressure: Left Ventricle/Aorta
• Lowest Pressure: Vena Cava / Right
Atrium
• Blood pressure is measured as a ratio of two
numbers- Systolic and Diastolic
• Systolic pressure is the higher value
• Typically around 120 mmHg in humans
• Peak pressure from ventricular ejection
(ventricular systole)
• Diastolic pressure is the lower value
• Typically around 80 mmHg in humans
• Pressure of blood during ventricular
relaxation (Cardiac diastole)

  • Mean arterial pressure: id driving force due to the two pressures

BLood pressure

• Blood flows from High Pressure Low
Pressure
• Highest (Aorta) Lowest (Vena cava)
• Blood leaves the heart - Aorta
• Aorta branches into slightly smaller arteries
• Branch into small arteries branch into
arterioles branch into capillaries
• Branching: smaller vessels, but large
number of branches
• More vessels = large cross-sectional area =
lower pressure/ slower speed of blood flow
• Slow speed allows best diffusion of
oxygen and nutrients
Blood vessel anatomy

Blood circulates through the body in
blood vessels (Vasculature)
• Arteries = blood away from the heart
• Thick middle layer of smooth muscle
to control artery diameter
• High pressure blood, no valves
• Classes by size:
• Largest: Aorta
• Named Arteries:
• Conducting arteries (conduits)-
carotid arteries, iliac arteries,
subclavian arteries
• Muscular arteries- distribute to
specific organs
• Resistance arteries- small branches off
muscular arteries
• Too many to name/count
• Generate the largest drops in blood
pressure (highest resistance to flow)
• Arterioles = very small arteries
• Thinner than a human hair (<200 uM)
• Veins = blood back to the heart

• Venule = very small vein; collect blood
from capillary beds

  • • Muscular venules- have some muscle
    around them allowing vasoconstriction
    • Named Medium veins- start to
    contain valves
    • Named Large veins – lowest pressure
    in body
    • Superior and Inferior Vena Cava
    • Capillaries = connect arteries & veins

  • smallest blood vessels

  • exchange of oxygen ans nutrients from blood into tissue, and waste from tissue back into blood

Tissue layers of blood vessels

Three layers in arteries and veins
1. Innermost = tunica interna = endothelium
2. Middle = tunica media = smooth muscle
3. Outer= tunica externa = connective tissue


• Arteries = blood away from the heart
• Interna (Endothelium)- 1 cell layer thick
• Elastic Lamina = allows arteries to be
stretchy/absorb pressure changes
• Media (Smooth Muscle)- thick muscle layer
• Externa (Connective tissue)- thin connective
structural layer of collagen
• No valves (high pressure keeps flow one-way)
• Veins = blood back to the heart
• Interna (Endothelium)- 1 cell layer thick
• Media (Smooth Muscle)- thin muscle layer
• Externa (Connective tissue)- thick connective
structural layer of collagen
• Valves- direct one-way flow through veins
• Capillaries = connect arteries and veins
• Interna (Endothelium)- 1 cell layer thick

Arteries = blood away from the heart
• Largest: Aorta, then Conduit Arteries
• Resistance arteries- small branches off
muscular arteries
• Too many to name/count
• Generate the largest drops in blood
pressure (highest resistance to flow)
• Narrower Diameter = ↑
resistance to blood flow
• Thinner than a human hair (<200
uM)
• Endothelial cells flatten in shape to
align with direction of flow
• Band of Elastin protein (internal
elastic lamina) allows arteries to
stretch or shrink as needed to control
rate of blood flow

Veins: valve and pump


Veins = blood back to the heart
• Veins have very low blood
pressure
• Pressure in blood vessels drops the
further from the ventricles it travels
• Venule = very small vein; collect blood
from capillary beds
• Muscular venules- have some muscle
around them allowing vasoconstriction
• Medium veins- start to contain valves
• Valves: Prevent backflow
• Arteries and capillaries- pressure is
high enough to keep blood flowing
• Veins- pressure is not high
enough, blood would backflow if
there wasn’t valves to block
• ‘Blown veins’ = valves are
damaged, blood can backflow
• Skeletal muscles: work to “pump”
blood against gravity
• Large veins – lowest pressure in body
• Pressure in Vena Cava is ~0mmHg,
can even go negative when heart is
filling

Blood has 3 main function: transportantion , regulation, defense

Transportation : Nutrients and wastes throughout the body

  • gases: Oxygen and CO2

  • glucose, amino acids, lipids, wastes

Regu;ation: homeostasis

  • circulates horomnes

  • pH: 7.35-7.45

  • , water, BP, temperature balance
    Defense:

  • WBC’s: leukyocytes

  • Antibodies: stick and label foreign substances for removal

Blood clotting
Blood has two components: liquid and blood cells

BLood Liquid: plasma

Blood Pressure

  • flows from high → low pressire

  • Highest ( aorta)→ lowest (vena cava)

  • blood leaves heart (aorta) → arteries → arterioles → capillaries

BLood (BP) is the pressure exerted by blood on walls of a vessel

  • as vessels get smaller pressure decreases until capillaries

  • highest pressure: Left ventricle/Aorta

  • Lowest pressure: Vena Cava/ right atrium

Blood Pressure is measured by Systolic and diastolic

Systolic pressure:When the heart contracts

  • peak pressure from ventricle system

  • typically around 120mmHg in humans

    Diastolic: when the heart rests

  • around 80mmHg in humans

  • pressure of blood during ventricular relaxation

    Mean arterial pressure: driving force due to two pressures

  • MAP= diastolic BP + (Systolic- diastolic BP)/3

    Pulse pressure: difference between sustolic and diastolic pressure

Factors that affect blood pressure

  • Cardiac output: increase output= BP goes up

    • increased heart rate

    • increased stroke volume

Volume of blood: increased volume → increased pressure

Viscosity( thickness): higher viscosity→ higher BP

  • can be caused by liver damage or disease ( blood sugar)

low viscosity by anemia
Diameter of blood vessels

  • Larger diameter ( vasodilation)= lower pressure

Smaller diameter ( vasoconstriction)= Higher pressure
Hypertension= high Blood pressure

  1. Cardiac output

  2. Peripheral resistance

Common factors of high BP

  • Narrowed vesseld

    • plaque= asthersclerosis

    • stiffness=arteriosclerosis

    • loss of ability to dialate

  • Kidneys- extra wter retention

  • loss of peripheral blood vessles ( rarefaction)

  • Chronic sympathetic nervous system activation

Athersclerosis: leading cause of heart disease and High BP

  • injury to vessel causes a buildup of scar tidsue

  • fats get trapped in scar tissue causing plaque

Plaque narrows arteries and impairs blood flow

  • narrow -High BP

  • blocked= no blood flow ( heart attack, stroke)

Treatments:

  • stent/ bybass surgery

  • angioplasty

  • BP meds