cvs ppt
TRANSCRIPT
Hydrostatic pressure is what is exerted by a liquid when it at rest. The height of a liquid column of uniform density is directly proportional to the hydrostatic pressure. The hydrostatic properties of a liquid are not constant and the main factors influencing it are the density of the liquid and the local gravity. Both of these quantities need to be known in order to determine the hydrostatic pressure of a particular liquid.
Hydrostatic Pressure (Pa or N/m2) = Height (m) x Density (kg/m3) x Gravity (m/s2)
The density of a liquid will vary with changes in temperature so this is often quoted alongside hydrostatic pressure units while the local gravity depends on latitudinal position and height above sea level.
For convenience the most common standard for hydrostatic pressure is metres of water or feet of water at 4 deg C (39.2 degF) with a standard gravity of 9.80665 m/s2.
First of all, let us assume that the density of the liquid remains constant. As gravity acting downwards on the liquid is also said to be constant at 9.8m/s^2 , the independent variable would be the height of the liquid in the column. Hence, the dependent variable would be the hydrostatic pressure of the column of liquid.
As the bottom hole has more height as compared to the one at the top, there is so much more water above it causing a larger force pushing down and thus, resulting in the jet of water to stream out of the hole with a larger force too. This is evident from the larger distance that the stream of water from the bottom hole makes, since it has higher energy as compared to the hole at the top.
skin
Cell membrane
nucleus
cytoplasm
Internal environment
skin
Cell membrane
Cell
External environment
The Microcirculation
The Microcirculation
The Functions of Microcirculation
Net Starling Forces in Capillaries
Net filtration pressure of .3 mmHg which causes a net filtration rate of 2ml/min for entire body
Net Starling Forces in Capillaries
Net filtration pressure of .3 mmHg which causes a net filtration rate of 2ml/min for entire body
The four Starling Forces can be broken into two hydrostatic pressures and two osmotic forces (sometimes called colloid osmotic
Starling Forces—Hydrostatic Pressures
The capillary (blood) hydrostatic pressure (or Pc for short) is the pressure on the fluid forcing it outward on the walls of the capillaries. This pressure is roughly 35 mmHg at the arterial end of the capillary and 15 mmHg at the venous end of the capillary causing filtration. Recall that resistance causes this decrease in pressure along the capillary.
The interstitial-fluid hydrostatic pressure (or PIF for short) is the pressure from the fluid in the interstitial compartment pushing back on the capillary. This pressure varies from organ to organ, varying from –6 mmHg (in subcutaneous tissue) to +6 mmHg (in the brain and kidneys). Here we will assume that there is no hydrostatic pressure in the interstitial fluid.
The two remaining Starling Forces, called osmotic forces (or colloid osmotic pressures—COP), cause fluid to move into an area due to osmosis. The osmotic forces at right are caused by the presence of large proteins in the plasma (generally albumin) and in the interstitial fluid. These large proteins are unable to move across the capillary and will, consequently, cause osmosis.
The osmotic force of plasma proteins (or P) will draw fluid back into the capillary, causing reabsorption. Since the plasma contains a lot of proteins, this force is high at 28 mmHg.
The osmotic force of proteins in the interstitial space (or IF) will pull fluid out of the capillary, causing filtration. Since the interstitial fluid contains little proteins, this force is low—around 3 mmHg.
Autoregulation is a manifestation of local blood flow regulation. It is defined as the intrinsic ability of an organ to maintain a constant blood flow despite changes in perfusion pressure. For example, if perfusion pressure is decreased to an organ (e.g., by partially occluding the arterial supply to the organ), blood flow initially falls, then returns toward normal levels over the next few minutes
This autoregulatory response occurs in the absence of neural and hormonal influences
and therefore is intrinsic to the organ. When perfusion pressure (arterial minus
venous pressure, PA-PV) initially decreases,
blood flow (F) falls because of the following relationship between
pressure, flow and resistance:
When blood flow falls, arterial resistance (R) falls as the resistance vessels (small arteries and arterioles) dilate. Many studies suggest that that metabolic, myogenic and endothelial mechanisms are responsible for this vasodilation. As resistance decreases, blood flow increases despite the presence of reduced perfusion pressure.
Under what conditions does autoregulation occur and why is it important? A change in systemic arterial pressure, as occurs for example with hypotension caused by hypovolemia or circulatory shock, can lead to autoregulatory responses in certain organs
Different organs display varying degrees of autoregulatory behavior. The renal, cerebral, and coronary circulations show excellent autoregulation, whereas skeletal muscle and splanchnic circulations show moderate autoregulation. The cutaneous circulation shows little or no autoregulatory capacity.
Autoregulation, therefore, ensures that these critical organs have an adequate blood flow and oxygen delivery.
There are situations in which arterial pressure does not change, yet autoregulation is very important. Whenever a distributing artery to an organ becomes narrowed (e.g., atherosclerotic narrowing of lumen, vasospasm, or partial occlusion with a thrombus) this can result in an autoregulatory response.
Narrowing (see stenosis) of distributing arteries increases their resistance and hence the pressure drop along their length. This results in a reduced pressure at the level of smaller arteries and arterioles, which are the primary vessels for regulating blood flow within an organ. These resistance vessels dilate in response to reduced pressure and blood flow. This autoregulation is particularly important in organs such as the brain and heart in which partial occlusion of large arteries can lead to significant reductions in oxygen delivery, thereby leading to tissue hypoxia and organ dysfunction.
•Flow rate Q is defined to be the volume V flowing past a point in time t, or Q=Vt where V is volume and t is time.• •The SI unit of volume is m3.AnotheFlow rate Q is defined to be the volume V flowing past a point in time t, or Q=Vt where V is volume and t is time.The SI unit of volume is m3.
Another common unit is the liter (L), which is 10−3m3.•Flow rate and velocity are related by Q=Av¯ where A is the cross-sectional area of the flow and v¯ is its average velocity.•For incompressible fluids, flow rate at various points is constant. That is, A1v¯1=A2v¯2n1A1v¯1=n2A2v¯2.
U R WHAT U EAT
Arterial pressure that must be overcome before blood can be ejected from the heart. (Afterload is indicated by the diastolic blood pressure)
Contractility: contractile strength (for a given EDV ) increases if there is an increase in cytoplasmic calcium ion concentration.
Regulation of Heart Rate
Factor Type Increase Rate Decrease Rate
Autonomic NS
Sympathetic (stimulation of pacemaker cells increases heart
rate and contractility)
Parasympathetic (inhibition of cardiac pacemaker cells
decreases heart rate)
Hormones
Epinephrine
Thyroxine (increases BMR and potentiates epi and NE)Insulin
GlucagonGlucocorticoids
Ions
Hypercalcemia
Hypocalcemia
Hypernatremia (inhibits calcium transport)Hyperkalemia (lowers resting membrane potential)
Hypokalemia (causes both abnormal contractions and decreases contractility
Other factors
Fetal>child>adult;
Female>maleExercise
Heat Fever Stress
Inspiration
Exercise* (long term aerobic conditioning)
Cold
Regulationof Heart Rate
The heart begins as a pair of endothelial tubes that fuse to make a single heart tube with four bulges representing the four chambers.Referring to (b) in the figure above:The sinus venosus receives all embryonic venous blood. It becomes the smooth-walled part of the right atrium and the coronary sinus and gives rise to the sinoatrial node.The atrium gives rise to the pectinate muscle-ridged parts of the atria.The ventricle becomes the left ventricle.The bulbus cordis and the truncus arteriosus give rise to the pulmonary trunk, the first part of the aorta, and most of the right ventricle.The foramen ovale is an opening in the interatrial septum that allows blood returning to the pulmonary circuit to be directed into the atrium of the systemic circuit.The ductus arteriosus is a vessel extending between the pulmonary trunk to the aortic arch that allows blood in the pulmonary trunk to be shunted to the aorta.
1. mixing of oxygen-poor blood with oxygenated blood
Septal defectsPatent ductus arteriosus
2. Narrowed valves or vessels that increase the workload of the heart
Coarctation of the aortaTetralogy of Fallot
Congenital Heart Defects
Sclerosis and thickening of the valve flaps occurs over time, in response to constant pressure of the blood against the valve flaps.
Decline in cardiac reserve occurs due to a decline in efficiency of sympathetic stimulation.
Fibrosis of cardiac muscle may occur in the nodes of the intrinsic conduction system, resulting in arrhythmias.
Atherosclerosis is the gradual deposit of fatty plaques in the walls of the systemic vessels.
Aging Aspects of the Heart
Homeostatic Imbalance of Cardiac Output
Congestive heart failure occurs when the pumping efficiency of the heart is so low that blood circulation cannot meet tissue
needs.Pulmonary congestion occurs when one
side of the heart fails, resulting in pulmonary edema.