70 kg (-150lbs)

Person = 5.5L

Plasma includes water proteins ions nutrients hormones wastes etc

Plasma = 55%

Leukocytes and Platelets - "buffy coats"

Erythrocytes = 45% (hematocrit = 45%)

CO = HR xSV, as follows,

The heart is the pump that moves the blood. Its activity can be expressed as "cardiac outut (CO)" in reference to the amount of blood moved per unit of time.

CO = Heart rate x Stroke volume, as follows,

CARDIOVASCULAR PHYSIOLOGY

PT. 2

Myocardiocytes are the cells of the heart:

A small fraction of cardiac muscle cells, called the auto-rhythmic cells, determine the heart rate (HR).

A much larger group, making up 99% of the total cells the heart, constitutes the contractile cells, Their activity determines the stroke volume (SV).

CARDIOVASCULAR PHYSIOLOGY

PT. 3

Mean arterial pressure, which drives the blood, is the sum of the diastolic pressure (peak) plus one-third of the difference between the systolic (trough) and diastolic pressures.

The autonomic system dynamically adjusts CO and mean arterial pressure.

Blood composition affects viscosity

COMPONENTS

• Heart

Pump of variable rate and strength

• Vessels

Pipes of variable diameter

• Blood

Fluid of variable volume and viscosity

• Flow units are volume/unit time
• Flow = Pressure difference/Resistance to Flow
• Flow = ΔP/R
• Resistance is related to fristion and is a function of blood viscosity (η), length (L) and radius (r) of the vessel
• Resistance = 8Lη/ π r⁴
• Vasoconstriction and vasodilation are important controls. Note that the radius is races to the fourth power.
  

Three things contribute to the resistance:

1. Blood viscosity

(affected by volume and # of RBC)

2. Total blood vessel length

(how much tubing is needed)

3. Blood vessel diameter

(relaxed vessels increase diameter, vasoconstricted vessels decrease diameter)

Heart

• Atria - Chambers through which blood flows from veins to ventricles. Atrial contraction adds to ventricular filling but is not essential for it.
• Ventricles - Chambers whose contractions produce the pressures that drive blood through the pulmonary and systemic vascular systems and back to the heart.
  

THE CARDIOVASCULAR SYSTEM

PT. 2

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.
• Arterioles - Major sites of resistance to flow; responsible for the pattern of blood flow distribution to the various organs; participate in the regulation of arterial blood pressure.
  

THE CARDIOVASCULAR SYSTEM

PT. 3

Vascular System

• Capillaries - Sites of nutrient, metabolic end product, and fluid exchange between blood and tissues.
• Venules - Sites of nutrient, metabolic end product, and fluid exchange between blood and tissues.
• Veins - Low-resistance conduits for blood flow back to the heart. Their capacity for blood is adjusted to facilitate this flow.
  

THE CARDIOVASCULAR SYSTEM

PT. 4

Blood

• Plasma - Liquid portion of blood that contains dissolved nutrients, ions, wastes, gases, and other substances. Its composition equilibrates with that of interstitial fluid at the capillaries.
• Cells - Includes erythrocytes that function mainly in gas transport, leukocytes that function in immune defenses, and platelets (cell fragments) for blood clotting.
  

• Epicardium: This is the most superficial (outer) layer. It is the visceral layer of the serous pericardium.
• Myocardium: The middle later of the heart muscle. It is composed of cardiac muscle and forms the bulk of the heart mass. This is the layer that contracts.
• Endocardium: The inner layer, it is of endothelium which rests on a thin layer of connective tissue. It is continuous with the lining of the blood vessels entering and leaving the heart.
  

• Approximately 1 percent of cardiac cells do not function in contraction, but have specialized features that are essential for normal heart excitation.
• These cells constitute a network known as the conducting system of the heart and are in electrical contact with the cardiac muscle cells via gap junctions.
• The conducting system initiates the heartbeat and helps spread the impulse rapidly throughout the heart.
  

The signal starts in the SA node (normal rate is about 75 signals per minute).

The wave of depolarization travels through the internodal pathway (via gap junctions) to the AV node. The signal then has a 0.1s delay to allow the atria to contract and totally fill the ventricles before they contract.

EXCITATION OF THE HEART

PT. 2

Then the wave of depolarization travels through the AV bundle (bundle of His) down towards the purkinjie fibers in the ventricle from bottom to top

The purkinjie fibers also supply the papillary muscles which tell them to contract before the rest of the atria help prevent backflow through the valves.

• Arrhythmias are uncoordinated atrial and ventricular contractions caused by a defect in the conduction system.
• A fibrillation is a rapid and irregular (usually out of phase)
  

• A graphic record of the hearts elec. Activity
• The leads must be placed correctly to get a proper reading
• The reading
  

• A small amt. of extracell. Ca enters the cell through the L-type Ca channels during the plateau of the action potential
• This calcium binds to ryanodine receptors on the SR membrane and triggers the release of a larger quantity of Ca
  

• non-oxygen blood leaving = 2 branches
• non-oxygen blood enter = 2 branches
• oxygen blood enter = 2 branches
• oxygen blood leaving = 4 branches
  

• Brain = 650 (13%)
• Heart = 215 (4%)
• Skeletal muscle = 1030 (20%)
• Skin = 430 (9%)
• Kidney = 950 (20%)
• Abdominal organs = 1200 (24%)
• Other = 525 (10%)

BLOOD FLOW AT REST

PT. 2

The distribution of blood in a confortabe reseting person is shown here

Synamicadj in blood devel all on a person to respond to widely varying circumstances. Incl emergencies

ex: cold decrease in blood flow, = moves towards the core

• Radius of A = 2
• Radius of B = 1

• 1/2⁴ = 1/16 (A)
• 1/1⁴ = 1/1 (B)
• Resistance in A is 1/16th of B
• Flow of A is 16X than B
  

Normally, the heart beat starts in the right atrium when a special group of cells sends an electrical signal. As a group, these cells are called the sinoatrial (SA) node or the sinus node. They are the heart’s pacemaker.

The heart normally beats about 70 to 80 times per minute; it is the only self-contracting muscle in the body, acting without an external signal from nerves.

The cardiac cycle is all the events involved with the blood flow through the heart during one heart beat.

Systole is the contraction phase.

Diastole is the relaxation phase.

• Opening of AV valves

Rapid ventricular filling

Atrial contraction

• Closing of AV valves

Isovolumetric ventricular contraction

CARDIAC CYCLE

PT. 2

• Opening of semilunar valves

Rapid ventricular ejection

• Closing of semilunar valves

Isovolumetric ventricular relaxation

• Valves only open one way
• Valvles open when a small pressure difference occurs in the appropriate direction
• Aortic valve opens when pressure inside ventricle > aortic pressure
• High blood pressure means heart most work harder to overcome aortic pressure
  

• Stroke volume equals amount of blood pushed out of ventricle
• End diastolic volume (EDV) minus End systolic volume (ESV). So Stroke Volume = EDV - ESV
• 135ml - 65ml = 70ml stroke volume
  

• Ventricles fill from expanding ventricles and venous pressure (65ml to 130ml)
• Atria adds about 20% of the filling, 130ml to 135ml
• So if atria fail to contract not as serious a problem
  

• Pulmonary artery (heart to lung) is 25 mmHg systolic and 10 mmHg diastolic.
• Aortic artery (heart to body) is 120 mmHg systolic to 80 mmHg diastolic.
• Stroke volumes are the same
  

Abnormal heart sounds are called heart murmurs.

Blood flow should be silent as long as it is smoothly flowing.

Most causes of heart murmurs in adults are valve problems.

• Sympathetic (NE)

Heart Rate

Contractility

Atria and ventricles

AUTONOMIC CONTROL

PT. 2

• Parasympathetic (ACh)

Heart Rate

Contractility

Atria only

• Increase amount of blood in ventricle and result in increase in blood pumped out
• Stroke Volume = End Diastolic-V - End Systolic-V
• Stroke volume = Filled ventricle volume - Contracted ventricle volume
  

• Anything that increases End Diastolic Volume (EDV) or increases the force of the ventricular contraction can increase Stroke Volume.
• The ventricules are never completely empty of blood, so a more forceful contraction will expel more blood with each pump.
  

• Arteries have strong walls that resist flow

Muscular arteries have a stable resistance

High pressure/Low Volume

• Veins have weaker walls and fill more easily

Act as volume reservoirs (54% of total volume)

Low Pressure/High Volume

• These are the smallest arteries. Their function is controlled by neural, hormonal, and local chemicals.

• They control minute-to-minute blood flow into the capillary beds. If they contract, blood flow is diverted away from their tissues; if they dilate, then blood flow to the tissue increases.

ARTERIOLES

PT.2

• The smaller ones, which directly lead into the capillary beds, are usually just a single layer of smooth muscle which spirals around the endothelium.

• These vessels have an impact on blood pressure.

• No direct effect of parasympathetic nervous system on arteriokar constriction/dilation

• Vasodilation results in blood flow to penis and erection via the action of nitric oxide
• Viagra and Cialis enhance nitric oxide signaling
• Morning erection is due to muscle relaxation during sleep
  

• Exchange of Nutrients and Wastes
• 3 basic mechanisms.:
• Passive diff.: lipid soluble

Bulk flow: fluid and non lipid sol.

Vesicle trans: non lipid sol.

• Gas exchange (O₂, CO₂)
• Nutrient and waste exchange
• Dynamics of exchange depend upon blood flow through the tissue and the metabolic state of the tissue (i.e. demand for nutrients and production of wastes)
  

Cardiac output = stroke volume X heart rate X peripheral resistance

Flow = Change in pressure / resistance

Stroke volume = end-diastolic - end-systolic volumes

ells can kill pathogens and other cells by three basic mechanisms

regulation of arterial pressure