Final Exam Flashcards
Heart
pump that provides pressure to blood to establish pressure gradients need for blood to flow to tissues
Blood vessels
Passageway through which blood is directed and distributed from hear to the rest of the body and return blood back to the heart
Blood
Used as transport medium
Diffusion
Capillaries are the sight of diffusion of molecules between blood and interstitial fluid
Arterioles
Are the resistance vessels
Smooth muscle makes variable resistance possible
Capillaries
Are the exchange vessels
Capillaries are made up of endothelial cells only, and are very permeable
Veins
Are thin walled. Have many elastic fibers and are stretchable, they are therefore capacitance vessels (the site where most of the blood volume is found and where regional blood volume is regulated)
Capacitance vessels
The site where most of the blood volume is found and where regional blood volume is regulated
At rest
About 60% of your blood volume is in your systemic veins and only 18% is in arteries
Blood Pressure
(BP) force per unit area exerted on the wall of a blood vessel by the blood.
Expressed in mmHg
Measured as systemic arterial BP in large arteries near the heart
The pressure gradient….
Provides the driving force that keeps blood moving from higher to lower pressure areas
Resistance
(Peripheral resistance)
Opposition to flow
Measure of the amount of friction blood encounters
Generally encountered in the peripheral systemic circulation
Three important sources of resistance
Blood viscosity
Total blood vessel length
Blood vessel diameter
Resistance =
1/r^2
Flow=
1/resistance (or r^2)
Mean BP in Systemic Circulation
100mmHg = aorta 90 = arteries 65 = areterioles 25 = capillaries 20 = venules 10 = veins 5 = vena cava
Most adult cardiac tissue is
Amitotic; most areas of cell death result in non-functional scar tissue
Mean arterial blood pressure
Systemic MAP is regulated by the cardiovascular system
Short-Term regulation of MAP
seconds to minutes
Occurs through neural pathways and targets heart, vessels, and adrenal medulla
Long-term regulation of MAP
Hours to days
Occurs through pathways that target the blood vessels and kidneys and their control of extracellular fluid volume
Stroke volume equation
And three main factors affecting
SV = EDV-ESV
Preload
After-load
Contractility
Preload
Degree of stretch of cardiac muscle cells before they contract (Frank-Starling law of the heart)
Preload
Cardiac muscles exhibits
A length-tension relationship
Preload
At rest,
Cardiac muscles are shorter than optimal length
Preload
Increased venous return
Distended (stretches) the ventricles and increases contraction force
After load
Pressure that must be overcome for ventricles to eject blood
After load
Hypertension
Increases after load, resulting in increases ESV and reduced SV
Contractility
Contractile strength at a given muscle length, independent of muscles stretch and EDV
Increased contractility
Positive inotropic agents
Increased Ca2+ influx due to sympathetic stimulation
Hormones (thyroxine, glucagon, and epinephrine)
Decreased contractility
Negative inotropic agents
Acidosis
Increased extracellular K+
Calcium channel blockers
Mechanoreceptors
Carotid sinus & aortic arch
Sensory nerve fibers (cells bodies in ganglia near BS) that project into the medulla
Stretching of vessel
Causes vasodilation and decreased HR
Stretch produces inward current that depolarizers the receptor generating receptor potential
Carotid sinus
In some individuals is unusually sensitive
Two classes of humoral controls
Influence the circulation:
Vasoactive substances that affect vasomotor tone of vessels affecting BP and blood flow
Nonvasoactive substances that act on non-CV targets to control extracellular fluid volume
Hormonal Controls
also influence MAP (draw diagram)
Solubility of O2 and CO2
In aqueous fluids is low
Diffusion of these gasses is therefore low - animals use respiratory pigments
Metalloproteins
(Respiratory pigments)
Proteins that contain metal ions which reversible bind to oxygen
Increase oxygen carrying capacity 50x
Three major types of respiratory pigments
hemoglobin
Hemocyanins (arthropods & mollusks)
Hemerythrins (some invertebrates)
Convection
Movement of molecules in fluid.
Can produce a steeper gradient across the diffusion barrier
In mammals
The bulk phase is the atmosphere and the external convective system is an air pump that includes
Air pump that includes
Chest wall
Respiratory muscles
Passages through which air flows (nose to alveoli)
External convection system
Maximizes gas exchange by continuously supplying the bulk-phase water or air to the external surface of gas exchange barrier (maintains high external PO2 and low external PCO2)
The concentration of dissolved O2 in the blood obey’s Henry’s Law
Gas molecules in the air must first dissolve in liquid in order to diffuse into a cell
The concentration of gas
In a liquid is proportional to its partial pressure and solubility
Henry’s Law
Concentration of G = Pgas x Sgas
Hemoglobin
Adult = tetramer Monomer = heme & globin
Heme
Porphyria compound coordinate to a single iron atom
Globin
Polypeptide, alpha or beta chain
Stoichiometrically alpha heme2, beta heme2
The complete Hb
Molecule can bind up to 4 O2 molecules (one for each atom)
O2 binding of Fe2+
The Fe2+ moves down into the plane of the porphyrin ring
When enough O2 molecules bind
Enough energy is built up and all 4 subunits of the Hb simultaneously snap into the relaxed (R) state - whether bound or not
O2 affinity
In R state is ~150x > than in the T state
when PO2 = 0
Hb molecules are in T state and have low O2 affinity
When PO2 is very high
All the Hb molecules are in the R state and have high O2 affinity
Intermediate PO2 values
Results in equilibrium between Hb molecules in the T and R states
What decreases the O2 affinity of Hb?
High temperature
High PCO2
Low pH
(Right shift of curve)
Temperature affecting oxygen affinity
increase temps = decreased affinity
Higher Pressure of oxygen with Hb saturation % = 50
Promotes oxygen unloading to warm muscles during exercise
pH and PCO2 alter Oxygen Affinity
Increased extracellular PCO2 causes CO2 to enter RBC, which leads to a decrease in intracellular pH (carbonic acid production)
Respiratory acidosis
Shifts the curve to the right
Hb is a buffer, sensitive to changes in pH
Raise in [Hb/H+]:[Hb] changes the conformation of Hb, lowering O2 affinity
pH and CO2 also
Facilitate oxygen transport to active tissues and facilitate oxygen binding at the respiratory surfaces
2,3 DPG
2,3-dipohosphoglycerate
RBCs and high [DPG]?
RBCs are producing energy via glycolysis and producing DPG as a result
CO2 transported in three ways
In plasma (5%), more soluble than O2 in body fluids
Binds to protein (20%)
Transported as bicarbonate (75%)
The glomerular filtration barrier
Carries a net negative charge that restricts movement of anions but enhances movement of cations.
Insulin
MW = 5,200 Da
Effective Molecular Radius = 1.48nm
Filtrate = 0.98 UFx/Px
Nephrotoxic serum nephritis
The negative charge on the glomerular filtration barrier is gone, allowing for easier diffusion of anions.
