Integrative Physiology: Hemodynamics I & II (copy)

Definition: The volume of blood pumped from the left ventricle of the heart with each beat.

End-Diastolic Ventricular Volume: The amount of blood in a ventricle at the end of diastole.
Mean Systemic Arterial Pressure: The average arterial pressure during one cardiac cycle.
Cardiac Output: The volume of blood the heart pumps per minute, calculated as:
$ext{Cardiac Output} = ext{Stroke Volume} imes ext{Heart Rate}$
Total Peripheral Resistance: The resistance to blood flow offered by all of the systemic vasculature.
Activity of Sympathetic Nerves to the Heart: Increases heart rate and contractility.
Activity of Parasympathetic Nerves to the Heart: Decreases heart rate.
Plasma Epinephrine: Hormone that increases heart rate and force of contraction.
Atrial Pressure: Pressure in the atria of the heart during different phases of the cardiac cycle.
Venous Return: The flow of blood back to the heart.
Intrathoracic Pressure: Pressure within the thoracic cavity which affects venous return.
Skeletal Muscle 'Pump': Mechanism aiding venous return during muscle contraction.
Blood Viscosity: Thickness and stickiness of blood which can also affect circulation.
Sympathetic Vasodilator and Vasoconstrictor Nerves: Different types of sympathetic nerves affecting arterial diameter.
Local Controls: Factors that alter blood flow locally, such as metabolites and injury agents.
Hematocrit: The volume percentage of red blood cells in blood.

Overview of blood vessel types: Arteries, arterioles, capillaries, venules, and veins.
Comparison between types:
- Arteries:
- Diameter: 4.0 mm (Elastic arteries)
- Provides high-pressure blood flow from the heart.
- Arterioles:
- Diameter: 30.0 µm
- Regulate blood flow into capillary beds.
- Capillaries:
- Diameter: 8.0 µm
- Site of exchange between blood and tissues.
- Venules and Veins:
- Venules: 20.0 µm diameter
- Veins: 5.0 mm diameter, return blood to the heart with lower pressure than arteries.

Capillaries lack smooth muscle and elastic tissue, facilitating material exchange with tissues.
Metarterioles: Regulate blood flow into capillary beds and can act as bypass channels.
Exchange at Capillaries:
- Bulk Flow: Governed by hydrostatic and osmotic pressure gradients.
- Filtration: Occurs at the arterial end due to higher hydrostatic pressure.
- Absorption: Occurs at the venous end when osmotic pressure pulls fluid back into the capillaries.

Mean Arterial Pressure (MAP): Calculated as:
$ext{MAP} = ext{Diastolic Pressure} + rac{1}{3}( ext{Systolic Pressure} - ext{Diastolic Pressure})$
MAP is influenced by:
- Cardiac Output
- Total Peripheral Resistance
Regulation includes both rapid cardiovascular responses and slower kidney mechanisms.

Blood Volume
Heart Effectiveness: How well the heart pumps (Cardiac Output)
Resistance to Blood Flow: Primarily influenced by arteriolar diameter and fluid dynamics.

Involved in short-term regulation of blood pressure.
Senses stretch in arteries:
- Decreased blood pressure leads to less stretch and lower action potential frequency in baroreceptors, increasing sympathetic activity.
- Increased blood pressure causes increased baroreceptor firing leading to decreased sympathetic output.

Renin–Angiotensin–Aldosterone System (RAAS): Increases blood pressure.
Epinephrine and Norepinephrine: Also increase blood pressure through vasoconstriction and increased heart rate.
Antidiuretic Hormone (ADH): Increases blood volume by promoting water retention.
Atrial Natriuretic Peptide (ANP): Reduces blood pressure by promoting sodium and water excretion.

Uncontrollable: Age, sex, family history.
Controllable: Smoking, obesity, sedentary lifestyle, untreated hypertension.
Blood Lipids: Relation to atherosclerosis and different lipoprotein levels (LDL and HDL).
Hypertension: Risk increases with each incremental increase in blood pressure.

Hematocrit: Ratio of red cells to plasma volume. Standard ranges:
- Males: 40% - 54%
- Females: 37% - 47%
Red cell count, white cell count, differential white cell count are also important metrics.

Process occurs in bone marrow, regulated by cytokines.
Three main blood cell types:
- Erythrocytes (Red Blood Cells): Transport oxygen; live approximately 120 days.
- Thrombocytes (Platelets): Involved in clotting, derive from megakaryocytes.
- Leukocytes (White Blood Cells): Immune system function (including lymphocytes, monocytes, and granulocytes).

Coagulation Reaction Steps:
1. Injury exposes tissue factors.
2. Platelet adhesion and release of factors.
3. Activation of clotting factors through intrinsic and extrinsic pathways.
4. Fibrinogen converted to fibrin, forming a clot.
Fibrinolysis: Process that removes the clot after healing is complete, involving the conversion of plasminogen to plasmin.

Antigens on red blood cells define blood types (A, B, AB, O).
Blood transfusions require careful matching to prevent agglutination and hemolysis.
Rh factor significance, particularly in prenatal care to prevent hemolytic disease of the newborn.

Understanding hemodynamics is crucial for recognizing cardiovascular function, pathology, and treatment approaches in clinical settings.