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!
AortaAorta
Cardiac Output = Area*Velocity = Total Area * Velocity
Figure 44-30
From heart Capillaries Return to heart
Velocity
Total area
Cardiac Output = PA-PV/R R = 8 L/ r4
What is blood?
40% RBC, 60% Plasma
How does the viscosity of blood vary with hematocrit (fraction rbc) ?
hematocrit
0 20 40 60 80
Figure 44-3Closed system: Blood never leaves vessels.
Tubular heart
Single heart
Open system: Hemolymph leaves vessels and comes intodirect contact with tissues.
Other circulatory systems
Open versus closed
Figure 44-23
Interstitial fluid
Excess fluid in interstitialspace enters lymphatic duct Lymph leaves tissue
Blood enterscapillary fromarteriole (asmall artery)
Net pressure 10 mm Hg out
Osmoticpressure22 mm Hg
Blood pressure32 mm Hg
Capillary
Fluid leaves
Blood leavescapillary tovenule (asmall vein)
Net pressure 7 mm Hg in
Osmoticpressure22 mm Hg
Blood pressure15 mm Hg
Fluid returns
Lymphatic duct
Is it really “closed”?
Plasma and lymphatic exchange : a consequence of the balance of mechanical and osmotic pressures.
Environmental oxygen:Earth’s atmosphere today:Nitrogen 78%Oxygen 21%CO2 0.03%Other gases (H, Ar …)
250 mmHg
760 mmHg
Gas concentrations measured as Partial Pressure:
Strategies for getting oxygen to tissues
Simple diffusion:Protozoa,plankton, tiny insectsAnd small cold creatures..
Strategies for getting oxygen to tissues
FISH GILLS : COUNTER CURRENT EXCHANGERS
Strategies for getting oxygen to tissuesFick’s Law: Rate of diffusion = k A P2-P1
DFISH GILLS : COUNTER CURRENT EXCHANGERS
100 90 70 50100 90 70 50
0 10 30 500 10 30 50 90 60 30 590 60 30 5
100 90 70 50100 90 70 50
O2 O2
Strategies for getting oxygen to tissues
BIRD LUNGS : COUNTER CURRENT EXCHANGERS
Trachea
Bronchi
Bronchioles
Lung
Human gas exchange: tidal respiration.
D = 0.2 um
D = 0.2 um
Red blood cells represent about 40% of the total blood volume in humans.
Hemoglobin Transports Oxygen to Tissues
1.5% of oxygen loads to blood
plasma
Hemoglobin
O2 to tissues
O2 fromlung
98.5% of oxygen loads to hemoglobinin red blood cells
Hemoglobin Transports Oxygen to Tissues
98.5% of oxygen loads to hemoglobinin red blood cells
Heme group
The Oxygen-Hemoglobin Equilibrium Curve
CO2 Handling by red blood cells -- Hemoglobin buffers pH changes.
Key characteristics of nervous systems
Key characteristics of nervous systems
• Fast• Not long lasting• Highly specific• Transmission in the form of action
potentials (fast and electrical)• Chemical transmission largely
restricted to synapses with very small distances.
Contrast to endocrine systemContrast to endocrine system
• Slow (long lasting).• Can have both specific and broad
actions.• Transmission via circulatory
system. • Chemical transmission dominates
and occurs over long distances.• Specificity determined by
receptors.
Six categories of chemical signaling
Autocrine signals
Endocrine signals
Paracrine signals
Neural signals
Neuroendocrine signals
Pheromones
Examples
ProteinInsulinGrowth hormone
Amio AcidNorepinephrineEpinephrineSerotonin
SteroidEstradiolTestosteroneCortisol
Three categories of chemical signalsAnd the signals are amplified!
Amplification via two different mechanisms
STEROID HORMONE ACTIONHormonereceptor
Steroidhormone
Hormone-receptorcomplex
Hormone-responseelement
RNApolymerase
DNA
mRNA
Nucleus
Proteins
Ribosome
MODEL FOR EPINEPHRINE ACTION
Epinephrine
Receptor
1. Epinephrinebinds to receptor
Adenylylcyclase
3. Activated adenylyl cyclase catalyzes formation of cAMP
2. Activationof G protein
Transmission ofmessage fromcell surface
The major components of the endocrine system
Hypothalamus
Posteriorpituitary
Hypothalamichormones
Neurosecretorycells of thehypothalamus
Blood vessels
Hormone
Response
ADH Oxytocin
Mammary glands,uterine muscles
Aquaporinsactivated; H2O reabsorbed
Contraction duringlabor; ejection of
milk during nursing
Kidneynephrons
Target
The anterior pituitary
Blood vessels
Neurosecretorycells of thehypothalamus
Hypothalamichormones
Anteriorpituitary
Pituitaryhormones
Hormone
Target
Response
ACTH Follicle-stimulatinghormone (FSH)and luteinizinghormone (LH)
Adrenalcortex
Testes orovaries
Production of sexhormones; controlof menstrual cycle
Production ofthyroid
hormones
Growthhormone
(GH)
Prolactin(PRL)
Thyroid-stimulatinghormone
(TSH)
Many tissues Mammaryglands
Thyroid
Mammarygland growth;
milk production
GrowthProduction ofglucocorticoids
Three pathways regulated by feedback inhibitionAmplification again.
Neuroendocrine pathway
Neuroendocrinesignal
Endocrine pathway Neuroendocrine-to-endocrine pathway
Neuroendocrinesignal
Endocrinesignal
Endocrinesignal
Endocrine cell
Effectorcell
Response
Response
Stimulus Stimulus
Fee
db
ack
inh
ibit
ion
Fee
db
ack
inh
ibit
ion
Sensor cell
Effectorcell
Fee
db
ack
inh
ibit
ion
Neural signal
CNS
Stimulus
Sensor cell
Neural signal
CNS
Response
Effectorcell
Endocrine cell
