58. 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.
61. 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.
62. 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.
63. 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.
64. 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.
76. Net Starling Forces in Capillaries
Net filtration pressure of .3 mmHg which causes
a net filtration rate of 2ml/min for entire body
77.
78.
79.
80.
81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
91.
92.
93.
94.
95.
96.
97.
98.
99.
100.
101.
102.
103.
104.
105.
106.
107.
108.
109.
110.
111.
112.
113.
114.
115.
116.
117.
118.
119.
120.
121.
122.
123.
124.
125.
126.
127.
128.
129.
130.
131.
132.
133.
134.
135.
136.
137.
138.
139.
140.
141.
142.
143.
144.
145.
146.
147.
148.
149.
150.
151.
152.
153.
154.
155.
156.
157. Net Starling Forces in Capillaries
Net filtration pressure of .3 mmHg which causes
a net filtration rate of 2ml/min for entire body
158.
159.
160.
161.
162.
163.
164.
165.
166.
167.
168.
169.
170.
171.
172.
173.
174.
175.
176.
177. The four Starling Forces can be broken into
two hydrostatic pressures and two osmotic
forces (sometimes called colloid osmotic
178. 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.
179. 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.
180. 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.
181. 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.
182. 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.
183.
184.
185.
186.
187.
188.
189.
190.
191.
192.
193.
194.
195.
196.
197.
198.
199.
200.
201.
202.
203.
204. 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
205. 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:
206. 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.
207. 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
208. 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.
210. 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.
211. 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.
212.
213. •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.
298. 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
Glucagon
Glucocorticoids
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>male
Exercise
Heat
Fever
Stress
Inspiration
Exercise* (long term aerobic conditioning)
Cold
Regulationof Heart Rate
299.
300.
301.
302. 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
The foramen ovale is an opening in the interatrial septum that allows blood returning to the pulmonary circuit to be d
The ductus arteriosus is a vessel extending between the pulmonary trunk to the aortic arch that allows blood in the p
303. 1. mixing of oxygen-poor blood with
oxygenated blood
Septal defects
Patent ductus arteriosus
2. Narrowed valves or vessels that
increase the workload of the heart
Coarctation of the aorta
Tetralogy of Fallot
Congenital Heart Defects
304.
305. 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
306. 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.
