Transcript Lectures220Week9Note..

Conservation of mass: the total blood volume is (nearly) constant.
That means all of the blood passing though the aorta has to equal all of the blood
passing though the capillaries in every second!
Cardiac Output = Area*Velocity = Total Area * Velocity
Aorta
Figure 44-30
From heart
Velocity
Total area
Capillaries
Return to heart
Cardiac Output = PA-PV/R
R = 8 h L/p r4
What is blood?
40% RBC, 60% Plasma
How does the viscosity of blood vary with hematocrit (fraction rbc) ?
h
0
20 40
60 80
hematocrit
Figure 44-3
Closed system: Blood never leaves vessels.
Single heart
Open system: Hemolymph leaves vessels and comes into
direct contact with tissues.
Tubular heart
Other circulatory systems
Open versus closed
Is it really “closed”?
Plasma and lymphatic exchange : a
consequence of the balance of
mechanical and osmotic pressures.
Blood enters
capillary from
arteriole (a
small artery)
Blood pressure
32 mm Hg
Blood pressure
15 mm Hg
Net pressure 10 mm Hg out
Net pressure 7 mm Hg in
Blood leaves
capillary to
venule (a
small vein)
Capillary
Osmotic
pressure
22 mm Hg
Osmotic
pressure
22 mm Hg
Lymphatic duct
Excess fluid in interstitial
space enters lymphatic duct
Interstitial fluid
Lymph leaves tissue
Environmental oxygen:
Earth’s atmosphere today:
Nitrogen 78%
Oxygen 21%
CO2
0.03%
Other gases (H, Ar …)
Gas concentrations measured as
Partial Pressure:
250 mmHg
760 mmHg
1
2
3
4
Strategies for getting oxygen to tissues
Simple diffusion:
Protozoa,
plankton,
tiny insects
And small cold creatures..
Strategies for getting oxygen to tissues
FISH GILLS :
COUNTER CURRENT EXCHANGERS
Strategies for getting oxygen to tissues
Fick’s Law: Rate of diffusion = k A P2-P1
D
FISH GILLS :
100
90
COUNTER CURRENT EXCHANGERS
70
50
100
90
70
O2
0
10
50
O2
30
50
90
60
30
5
Strategies for getting oxygen to tissues
BIRD LUNGS : COUNTER CURRENT EXCHANGERS
Human gas exchange: tidal respiration.
Trachea
D
=
0
.
2
u
m
Bronchi
Bronchioles
Lung
D
=
0
.
2
u
m
Red blood cells represent about 40% of the total blood volume in humans.
Hemoglobin Transports Oxygen to
Tissues
Hemoglobin
O2 from
lung
98.5% of oxygen
loads to hemoglobin
in red blood cells
1.5% of oxygen
loads to blood
plasma
O2 to tissues
Hemoglobin Transports Oxygen to
Tissues
Heme group
98.5% of oxygen
loads to hemoglobin
in red blood cells
The Oxygen-Hemoglobin Equilibrium Curve
CO2 Handling by red blood cells -Hemoglobin buffers pH changes.
Key characteristics of
nervous systems
Contrast to endocrine system
• Fast
• Slow (long lasting).
• Not long lasting
• Can have both specific and broad
actions.
• Highly specific
• Transmission in the form of action
potentials (fast and electrical)
• Chemical transmission largely
restricted to synapses with very
small distances.
• Transmission via circulatory
system.
• Chemical transmission dominates
and occurs over long distances.
• Specificity determined by
receptors.
Six categories of chemical signaling
Examples
Autocrine
signals
Paracrine
signals
Endocrine
signals
Neural
signals
Neuroendocrine
signals
Pheromones
Three categories of chemical signals
And the signals are amplified!
Protein
Insulin
Growth hormone
Amio Acid
Norepinephrine
Epinephrine
Serotonin
Steroid
Estradiol
Testosterone
Cortisol
Amplification via two different mechanisms
MODEL FOR EPINEPHRINE ACTION
1. Epinephrine
binds to receptor
Epinephrine
Adenylyl
cyclase
Receptor
2. Activation
of G protein
adenylyl cyclase
catalyzes
formation of
cAMP
Transmission of
message from
cell surface
STEROID HORMONE ACTION
Nucleus
Hormone
receptor
Steroid
hormone
3. Activated
mRNA
Proteins
DNA
Hormonereceptor
complex
Hormoneresponse
element
RNA
polymerase
Ribosome
The major components of the endocrine system
Hypothalamus
Neurosecretory
cells of the
hypothalamus
Hypothalamic
hormones
Posterior
pituitary
Blood vessels
Hormone
Target
Response
ADH
Oxytocin
Kidney
nephrons
Mammary glands,
uterine muscles
Aquaporins Contraction during
activated; H2O labor; ejection of
reabsorbed milk during nursing
The anterior pituitary
Neurosecretory
cells of the
hypothalamus
Hypothalamic
hormones
Blood vessels
Anterior
pituitary
Pituitary
hormones
Hormone
Target
ACTH
Adrenal
cortex
Follicle-stimulating Growth
hormone (FSH) hormone
and luteinizing
(GH)
hormone (LH)
Testes or
ovaries
Prolactin
(PRL)
Many tissues Mammary
glands
Thyroidstimulating
hormone
(TSH)
Thyroid
Response Production of Production of sex Growth
Mammary
Production of
glucocorticoids hormones; control
gland growth;
thyroid
of menstrual cycle
milk production hormones
Three pathways regulated by feedback inhibition
Amplification again.
Endocrine pathway
Neuroendocrine pathway
Stimulus
Neuroendocrine-to-endocrine pathway
Stimulus
Stimulus
Endocrine cell
Endocrine
signal
Effector
cell
Response
Sensor cell
Sensor cell
Neural signal
Neural signal
CNS
CNS
Neuroendocrine
signal
Effector
cell
Response
Neuroendocrine
signal
Endocrine cell
Endocrine
signal
Effector
cell
Response