Physiology Midterm

Lecture 9-11

Divisions of Circulatory System

Pulmonary and systemic

Pulmonary Circulation

Takes deoxygenated blood from heart to lungs and delivers oxygenated blood back

Systemic Circulation

Delivers oxygenated blood from heart to rest of body ad takes deoxygenated blood back

Types of Specialized Muscle Cells

Pacemaker cells and conduction fibers

Pacemaker cells

Cells that continuously depolarize- generate regular action potentials. These stimulate cardiac muscle to contract rhythmically- determine pace at which heart beats

Sinoatrial Node

Located in superior vena cava- rate of about 75 beats per minute. Drive the beating of the heart

Atrioventricular Node

Interatrial septa superior to ventricles- 50 beats per minute

Conduction Fibers

Specialized to conduct quickly the action potentials generated by the pacemaker cells, innervate cardiac muscle cells of myocardium

Artificial Pacemakers

Implanted to regulate irregular contractions of the heart- most frequently used to increase heart rates, occasionally used to slow a fast heart rate

Electrocardiogram

Electrical activity of heart recorded by surface electrodes on the skin

P Wave (EKG)

Depolarization of atria

QRS Complex (EKG)

Depolarization of ventricles- repolarization of atria occurs here

T Wave (EKG)

Ventricle repolarization

Heart Arrhythmia

Irregular beating of the heart caused by defects in electrical signals from heart

Fibrillation

Very rapid, out-of-phase contractions. Need to defibrillate- shock the heart

Cardiac Cycle

Involves the events of one heartbeat- both ventricular contraction and ventricular relaxation. Divided into two stages

Systole

Ventricular contraction

Diastole

Ventricular relaxation

Lub Sound

Caused by ventricles contracting at beginning of systole

Dub Sound

Caused by ventricles relaxing at beginning of diastole

Phonocardiogram

Detects and records heart sounds and murmurs. Four sounds are usually produced- only two are ordinarily audible

Three Types of Blood Vessels

Arteries, capillaries, veins

Elastic Artery

More elastic, closer to the heart

Muscular Artery

More muscle, farther from heart

Pressure Gradient

Difference in pressure between the beginning and end of a blood vessel. Contraction of heart provides pressure- decreases as it flows through vessels due to resistance

Resistance

Measure of hindrance to blood flow caused by friction between the moving fluid and the stationary walls. Dependent on viscosity and vessel length/radius

Viscosity

Friction between molecules, tends to be relatively constant in blood

Vessel length / radius

Friction between blood and vessel

Cardiac Output

Refers to the volume of blood pumped per minute by each ventricle- equivalent to the total blood volume of body. Regulated by rate and/or the volume

Factors Regulating Stroke Volume

Contractility, End Diastolic Volume, Afterload

Contractility

The strength of ventricular contraction- Any force that causes the ventricles to contract with more force will increase stroke volume

Nervous Control (Contractility)

ANS control of stroke volume regulated almost entirely by sympathetic nervous system, epinephrine increase contraction strength

Hormonal Control (Contractility)

Ventricular contractility increased by number of hormones- insulin, glucagon, thyroid hormones

End Diastolic Volume

The amount of blood in the ventricles just before they begin to contract, force of ventricular contraction varies in response to stretching of ventricular wall- Starling’s Law

Starling’s Law

When the rate at which blood flows into the heart from the veins changes, stretching of the ventricular wall changes, causing the ventricle to contract with greater or lesser strength so that the stroke volume matches the venous return

Afterload (Total Peripheral Resistance)

The pressure ventricles have to work against, determined in the aorta after contraction starts

Blood Pressure

Regulated by blood volume, peripheral resistance, and cardiac rate

Baroceptors

Stretch receptors located in the aortic arch and the carotid sinuses that detect changes in blood pressure. Function to counteract pressure changes

Circulatory Shock

Inadequate blood flow and/or oxygen uptake by tissues, can result from low blood volume- blood is diverted to heart and brain. Vasoconstriction in various organs including skin, results in low blood pressure, rapid pulse, cold, clammy skin

Septic Shock

Dangerously low blood pressure that results from sepsis (infection), very high mortality rate. Bacterial action activates immune system which promotes vasodilation and leakage from blood vessels causing blood pressure to drop

Blood Composition

Consists of blood cells and platelets in a fluid matrix (plasma)

Blood Cells

Red blood cells carry oxygen to tissues, white blood cells have a number of functions- mainly defensive

Platelets

Cell fragments responsible for coagulation

Plasma

Fluid matrix in blood- mainly water, various wastes, nutrients, hormones etc.

Red Blood Cells

Erythrocytes, optimized for gas transport. Biconcave disk shape maximizes surface area, nucleus-free cytoplasm packed with hemoglobin. Each molecule can carry four molecules of oxygen and a very small amount of CO2

Life Cycle of Erythrocytes

Remain in bloodstream for 120 days, new ones are produced at 2-3 million per second. Low O2 will cause erythropoietin released from kidney and trigger greater erythrocyte production in bone marrow

White Blood Cells

Leucocytes, divided into granulocytes and agranulocytes. Have nuclei and mitochondria, move in ameboid fashion. Play an important role in the immune system, found both in and out of the cardiovascular system

Granulocytes

Neutrophils, eosinophils and basophils

Agranulocytes

Lymphocytes and monocytes

Neutrophils

Make up 50-80% of all wbc, circulate in blood for 7-10 hours then migrate into tissues. Capable of phagocytosis- engulfs and digests microorganisms, abnormal cells, foreign particles. Levels increase during bacterial and viral infections and in response to inflammation and after surgery

Eosinophils

Make up 1-4% of all wbc, capable of phagocytosis- mainly attack parasitic invaders too large to be engulfed by neutrophils. Attach to body of parasites and discharge toxic molecules from cytoplasmic granules. Elevated levels often due to parasitic infections and can be a result of a number of diseases (asthma, eczema)

Basophils

Make up

Monocytes

Make up 2-8% of wbc, important phagocytes that do most of their work outside blood vessels. In blood for a few hours before migrating into tissues, become 5-10x larger and develop into macrophages

Lymphocytes

Make up 20-40% of wbc, 99% found in interstitial fluid. Three types: B-cells, T-cells, null cells. Have complex functions in the immune system

Platelets

Thrombocytes, fragments of large cells called megakaryocytes (found in bone marrow). Capable of ameboid movement but lack nuclei, play an important role in blood clotting. Lifespan is 5-9 days

Transfusion Reactions

Recipient’s antibodies can attach to donor’s red blood cells and cause cells to lump together and block small arteries if they don’t match

Universal Donor

Type O blood, any recipient antibodies have nothing to attach to

Universal Recipient

Type AB, recipient lacks antibodies for A and B antigens

Blood Clotting Methods

Vasoconstriction, formation of platelet plug, production of a web of fibrin proteins

Intrinsic Pathway

Formation of fibrin activated with no additional extrinsic chemicals

Extrinsic pathway

Formation of fibrin activated by chemicals released from damaged tissues

Lymphoid Tissue

Composed of reticular connective tissue, macrophages attached to fibers

Diffuse Lymphoid Tissue

Found in nearly every organ

Lymphoid Nodules

Solid, spherical bodies, lots of B-lymphocytes

Nodes

100s of small organs located along lymphatic vessels. Found in cervical, axillary, and inguinal surface regions. Filter blood before returning it to bloodstream and activate immune system

Spleen

Similar in shape and structure to a lymph node but much larger, largest lymphoid organ. Filters blood in much the way that the lymph nodes filter lymph, and stores breakdown products of red blood cells and re-circulates them to the liver

Thymus

Located just above the heart- large in newborns and continues to increase in size, begins to decline after puberty and function declines as we get older. Processes and matures T-lymphocytes and development of immune responses

Mucosa-Associated Lymphoid Tissue

Patches of lymphoid tissue located on mucous membranes throughout the body. Strategically placed to protect us from pathogens entering the body

Tonsils

Form a ring of lymphoid tissue around entrance to pharynx, remove many of the pathogens entering through the mouth or nose

Peyer’s Patches

Patches of lymphoid tissue located in the small intestine, helps destroy bacteria

Appendix

Tubular offshoot at beginning of large intestine, helps destroy bacteria in intestine

Lymphatic Interactions with Cardiovascular System

Returns fluid and proteins that have been filtered out of blood vessels

Lymphatic Interactions with Immune System

Acts as a filter to help capture and destroy foreign pathogens

Lymphatic Interactions with Digestive Systems

Picks up absorbed fat and transfers it into circulatory system

External Respiration

Exchange between atmosphere and body tissues

Internal Respiration

Use of oxygen to generate ATP in cells (cellular respiration)

External Respiration Processes

1) Breathing

2) Exchange of gases between blood and lungs

3) Transportation of gases between lungs and tissues

4) Exchange of gases between blood and tissues

Respiratory Side Functions

1) Contributes to acid-base balance in blood

2) Enables vocalization

3) Defense against pathogens and foreign particles

4) Provides route for water and heat loss

5) Enhances venous return

6) Activates certain plasma proteins

Pulmonary Pressures

Atmospheric pressure, Alveolar pressure, Pleural pressure

Atmospheric Pressure

Pressure in air around you, usually around 760mm Hg at sea level and can be affected by a number of things

Alveolar Pressure

Air pressure in alveoli, at rest is the same as atmospheric pressure. Varies during different stages of respiration, difference between these two pressures drives respiration

Pleural Pressure

Air pressure in pleural cavity, always slightly lower than alveolar pressure, the slight pressure differences keep the lungs inflated

Transpulmonary Pressure

Difference between the intra-pleural pressure and the intra-alveolar pressure

Inspiration

Diaphragm contracts, move inferiorly. Volume of thoracic cavity increases, can be aided by external costal muscles

Expiration

Relies more on the elasticity of the lungs, diaphragm relaxes, rib cage descends. Can be aided by internal intercostal muscles

Inspirational Reserve Volume

Maximum amount of air that can be inspired from the end of a normal inspiration (2000ml)

Tidal Volume

Single, unforced breath (500ml)

Expiratory Reserve Volume

Maximum amount of air that can be expired from the end of a normal expiration (1000ml)

Residual Volume

Left over air that can’t be expired (1200ml)

Gas Exchange

Oxygen diffuses into the blood and carbon dioxide diffuses out, passive process requiring no energy, relies on pressure relationships

Factors that Aid Gas Exchange

Large surface area, very thin membrane

Control of Respiration

Automatic- should not depend on levels of consciousness

Adaptable- be able to compensate for changes in O2 or CO2

Subject to voluntary control- need to override the control mechanisms at least for brief periods of time, control mechanisms are often hereditary

Hyperventilation

Increase in rate and depth of breathing, exceeds body’s need to remove CO2, low CO2 results in cerebral blood vessel constriction and can lead to fainting

Hypothalamus (Breathing)

Can influence breathing rate during strong emotions or pain

Cerebral Cortex (Breathing)

Can consciously control breathing rate and bypass medulla

Arterial Blood pH

7\.4

Venous Blood and IF pH

7\.35

Intracellular Fluid pH

7\.0

Alkalosis

pH of arterial blood > 7.45

Acidosis

pH of arterial blood < 7.35