The Cardiovascular System Flashcards
WHEN DOES A MYOCARDIAL INFARCTION OCCUR?
When blood circulation to the muscle of the heart itself is blocked
WHAT IS DIFFUSION?
The net movement of solute down a concentration gradient, brought about by the innate, randomly-directed jumping around of the solute due to its thermal energy
FUNCTION OF THE CARDIOVASCULAR SYSTEM
- Delivery of O2 and nutrients to each cell
- Removal of CO2 and waste products from each cell
- Communication between organs through transport of hormones and other extracellular mediator
- Temperature regulation
- Crucial hydrodynamic device in sexual reproduction!
WHAT THREE FACTORS DETERMINE BLOOD PRESSURE?
Blood pressure is determined by three main factors – cardiac output (pumping of the heart), the blood vessels or vasculature which not only carry the blood but are responsible for the resistance that creates the blood pressure and the various fluid compartments.
Cardiovascular circulation can be divided into the systemic and pulmonary (lung) circuits with the heart as the central pump
WHAT TWO CIRCUITS IS CARDIOVASCULAR CIRCULATION DIVIDED INTO?
Systemic and Pulmonary (lung)
WHAT IS THE COMPOSITION OF BLOOD?
BLOOD DISTRIBUTION AT REST
At rest….most blood is flowing through abdominal organs and _.
Majority of pumping is in parallel which means that all flow through organs is not linked. Some exceptions including intensines which run into liver….carry food. However if blood flow is occulled then reduction in blood to liver
Heart flow is quite small and any small change in flow and therefore oxygen can lead to reduce O2 and pain (called angina).
Kidneys
AT REST, WHERE DOES MOST BLOOD FLOW THROUGH?
Abdominal organs
Kidneys
BLOOD VESSELS CONTAIN MULTIPLE CELL LAYERS THAT REGULATE THEIR FUNCTION
Lumen
Endothelial cells (Tunica Intima)
Smooth muscle cells (Tunica Media)
Connective Tissue (Tunica Adventita)
All blood vessels contain endothelial cells but vary in the _ of the smooth muscle and connective tissue.
Thickness
BLOOD VESSELS INVOLVED IN THE CIRCULATION
THICH LAYER OF ELASTIC SMOOTH MUSCLE ACTS AS A PRESSURE RESERVOIR
ARTERIOLES CONTAIN A THIN MUSCULAR WALL AND SMALL LUMEN
Contraction of the smooth muscle regulates the diameter of the lumen:
- Determine blood flow to organs
- Major determinant of mean arterial pressure
CAPILLARIES HAVE A SINGLE LAYER OF ENDOTHELIAL CELLS
Exchange of nutrients, oxygen and _ across the capillary wall but NOT proteins.
Intercellular clefts and fused vesicles channels assist the exchange.
Waste
WHAT SUBSTANCES ARE EXCHANGED ACROSS CAPILLARY WALLS?
Nutrients
Oxygen
Waste
THE SKELETAL MUSCLE PUMP
Return of venous blood to the heart is facilitated by valves and the skeletal muscle pump.
Veins run close to the _ muscle .
Skeletal
SUMMARY OF STRUCTURE AND FUNCTION OF BLOOD VESSELS
OVERALL STRUCTURE OF THE HEART
MAJOR BLOOD VESSELS TO THE HEART
INTERNAL STRUCTURE OF THE HEART
WHAT DO VALVES DO?
Prevent the backflow of blood (ensures that blood flows in one direction).
BLOOD FLOW
BLOOD SUPPLY TO THE HEART
- Heart is has an extensive network of blood vessels supplied with oxygenated blood via the coronary arteries.
- Coronary arteries branch off the _ (coming from left ventricle)
- Most deoxygenated blood drains back into the right atrium via a single vein (coronary sinus)
Aorta
CORONARY ARTERIAL DISEASE CAN LEAD TO ISCHEMIA AND HEART ATTACKS
Coronary Arterial Disease
- insufficient blood flow (ischemia) is associated with chest pains (angina) often radiating down left arm
- severe blockage leads to damage (death) of the heart region and myocardial infarction or heart attack
- ventricular fibrillation and death (heart attack)
Causes of Coronary Arterial Disease
- Atherosclerosis (thickening of the coronary arteries)
- Blood clot (coronary thrombosis)
- Drugs
- Surgery
WHAT DO YOU CALL A BACTERIAL INFECTION IN THE CEREBRAL SPINAL FLUID?
Meningitis
CEREBRAL SPINAL FLUID (CSF)
- CSF cushions the brain against damage (brain is floating in CSF).
- CSF produced in specialised epithelial cell called choroid _ (500ml/day)
- Circulation around brain and spinal cord driven by changes in circulation, respiratory and posture.
- Passes into vein via valves at the top of the skull (arachnoid villus)
- Bacterial infection in CSF is called meningitis (increased pressure in brain leading to seizures and loss of consciousness)
Plexus
WHERE IS CSF PRODUCED?
In a specialised epithelial cell called the choroid plexus
BLOOD VESSELS AND BLOOD-BRAIN BARRIER
- Blood vessels ‘dive’ down into the brain.
- Capillaries contain tight junction and are less permeable to many substances (blood brain barrier)
- Difficult to get drugs and proteins into brain.
- Exception is lipophilic molecules such as anaesthetics, alcohol etc .
- Brain has no stored glycogen and requires constant supply of glucose and oxygen (damage within minutes) – 15% of resting blood flow
- Loss of blood supply and death of neurons - stroke
WHAT CAUSES A STROKE?
Loss of blood supply and death of neurons in the brain
TWO MAJOR FLUID COMPARTMENTS: EXTRACELLULAR AND INTRACELLULAR
THIS OCCURS IN THE CAPILLARIES
HOW ARE THE VOLUMES IN THESE COMPARTMENTS MAINTAINED?
WHAT IS OSMOSIS?
Net diffusion of water across a selectively permeable membrane from a region of high water concentration to one that has a lower water concentration (low particle concentration to high particle concentration)
OSMOLES
One osmole (osm) = 1 mole (6.02 x 1023 ) of solute particles in 1L.
FOR EXAMPLE:
1 M glucose = 1 Osm
1 M NaCl = 2 Osm
1 M MgCl2 = 3 Osm
Osmolarity is INDEPENDENT of molecular weight
CELLULAR MEMBRANES
- Permeable to water
- Impermeable to solutes (ions) such as Na+, Cl-, K+ etc
- Osmosis determines distribution of water (i.e. size of intracellular and extracellular compartments)
WHAT IS OSMOTIC PRESSURE?
The pressure required to prevent osmosis
WHAT WOULD HAPPEN IF YOU PUT A CELL INTO A HYPOTONIC SOLUTION?
The cell would swell (due to water moving into the cell).
WHAT WOULD HAPPEN IF YOU PUT A CELL INTO A HYPERTONIC SOLUTION?
The cell would shrink (due to water moving out of the cell)
WHAT IS THE COLLOID OSMOTIC PRESSURE?
Capillary membrane is semi-permeable.
- Permits diffusion of ions, water, oxygen, nutrients and waste
- NOT PROTEINS.
- Pressure exerted by the higher levels of protein in the plasma compared with the interstitial fluid= draws water back into plasma by osmosis (absorption)
- 28mmHg (plasma) – 3mmHg (interstitium)
= 25mmHg
WHAT IS HYDROSTATIC PRESSURE?
The force exerted by the blood on the capillary walls.
Hydrostatic pressure drives blood from plasma into interstitial space
CAPILLARY NET FILTRATION PRESSURE VARIES BETWEEN THE ARTERIAL AND VENOUS END OF THE CAPILLARIES
BULK FLOW OF FLUID FROM PLASMA
LYMPHATIC SYSTEM
- Lymph system is parallel vascular system with two major functions:
- Draining fluid from the tissues and returning to the cardiovascular system
- Maintenance of the immune response
WHAT ARE THE TWO MAJOR FUNCTIONS OF THE LYMPH SYSTEM?
- Draining fluid from the tissues and returning to the cardiovascular system
- Maintenance of the immune response
LYMPHATIC SYSTEM: DRAINAGE
- Fluid (plasma) passes (8L/day) from blood into the interstitial area (surrounds cells in the tissues)
- Collects fats from the intestines/liver and deposits into veins
- Excess fluid passes into lymph capillaries, through lymph nodes (detection of infection) before passing back to blood stream at the neck (largest is thoracic duct that drains into subclavian vein)
- Lymph vessels contain valves and fluid is forced along by action of muscles and breathing (respiration). Larger lymph vessels are surrounded by smooth muscle that contract spontaneously and driven by pacemaker cells (~ heart)
LYMPHATIC SYSTEM: IMMUNITY
- Lymph fluid contains white immune blood cells (lymphocytes, macrophages, dendritic cells)
- Collects antigens (proteins produced by pathogens)
- Antigens recognised by B-lymphocytes in lymph nodes leading to activation of immunity.
- B-cell proliferate to produce antibodies. Lymph nodes also contain multiple other immune cells (swelling can occur)
HEART FAILURE
Excessive kidney retention of water
Increased arteriolar resistance
High venous pressure
DECREASE IN COLLOID OSMOTIC PRESSURE
Reduction in plasma proteins
Loss of proteins in urine (kidney failure)
Loss of protein in denuded skin areas (burns)
Malnutrition
WHAT IS INTRACELLULAR OEDEMA?
Depression of metabolic systems of the tissues and lack of adequate nutrition to the cells e.g. ischaemia: reduced activity of Na+ pumps leads to accumulation of Na+ in cells, causing osmosis of water into cells
WHAT IS IT THAT DRIVES HEART RATE?
Heart rate is driven by waves of electrical activity that induce the cardiac muscles to contract
HEART- BLOOD FLOW
COMPONENTS OF THE CONDUCTION SYSTEM OF THE HEART
If you cut the nerves the heart continues to beat …..Shows that heart has its own intrinsic beat.
Heartbeat is driven by specialised myocytes composed of the sino-arterial node (at the top of the right atrium) and the artrioventricular node.
AV node connects atria and ventricles and delays the signal for 0.1ms….allow atrial to contract before ventricle
Bundles of his are fast conducting myocytes that connect to the Purkinje fibers. Purkinje fibers are very wide allowing rapid conduction throughout the ventricle and simultaneous contraction.
WHAT ARE THE BUNDLE OF HIS?
Fast conducting myocytes that connect to the Purkinje fibers. Purkinje fibers are very wide allowing rapid conduction throughout the ventricle and simultaneous contraction.
SEQUENCE OF CARDIAC EXCITATION
Delay at AV node allows atria to contract before ventricles
WHAT CAUSES THE PACEMAKER CELLS OF THE S-A NODE TO TRIGGER AN ACTION POTENTIAL?
Low resting membrane potential (-60 to -70 mV)
Na+ leakage that leads to depolarization
Graph for the SA node cell
MECHANISM UNDERLYING THE ‘SPONTANEOUS’ ACTION POTENTIALS IN THE PACEMAKER CELLS (SINO-ATRIAL NODES)
MECHANISM OF CONTRACTION OF THE VENTRICULAR CARDIOCYTES
WHAT IS IT THAT REGULATES THE CONTRACTION OF CARDIAC MUSCLES?
Calcium ions
HOW DOES CALCIUM PRODUCE CONTRACTION OF THE CARDIAC MUSCLES?
The entry of extracellular calcium ions causes the release of calcium from the sarcoplasmic reticulum, the source of about 95% of the calcium in the cytosol.
WHAT IS THE REFRACTORY PERIOD?
Time required before it is possible to re-stimulate muscle contraction