Download OLD NOTES – FOR REFERENCE ONLY! Chapter 42 – Circulation

OLD NOTES – FOR REFERENCE ONLY!
Chapter 42 – Circulation and Gas Exchange
I.
Circulation in Animals
a. Diffusion not sufficient for transport of substances (oxygen, carbon dioxide,
glucose, etc) because it is too slow; therefore transport systems that can move
substances in bulk are necessary
i. Ex. Heart pumps blood to all parts of the body and the blood carries
oxygen to all the body cells
b. Inverts = have either a gastrovascular cavity OR a circ. System for transport
i. Open and Closed Circ. Systems
1. Three Basic components:
a. Circ. Fluid (blood)
b. Tubes (blood vessels)
c. Pump (heart)
2. OPEN Circ. Systems
a. Blood and interstitial fluid are combined and called
hemolymph
b. Heart pumps hemolymph into sinuses, which are spaces
that surround the organs
c. Hemolymph NOT confined to blood vessels
3. CLOSED Circ. Systems
a. Blood is distinct from interstitial fluid; confined to blood
vessels
b. Materials are exchanged by diffusion between blood and
inersitital fluid that bathes the cells
c. Adapatations of the Cardiovascular System
i. Atrium (atria = pl.)  receives blood; thinner walls (collection)
ii. Ventricles  pumps blood; thicker, muscular walls for pumping
iii. Blood vessels
1. Arteries – carry blood away from heart (oxygenated); towards
capillaries
2. Veins – carry blood toward the heart (non-oxygenated); from
capillaries
3. Capillaries – microscopic vessels with thin, porous walls; good for
diffusion
iv. Circuit of Blood Flow
1. Systemic Circulation = branch of circ. System that supplies all
body organs then returns oxygen-poor blood back to atrium
(pumps to body)
2. Pulmocutaneous Circulation = leads capillaries to the gasexchange organs (lungs, skin, etc) where the blood picks up
oxygen and then returns to the left atrium; from here pumped to
systemic circulation (to rest of body) (pumps to lungs)
3. Combination of these two things is called double circulation
v.
vi.
vii.
RV – right ventricle
LV – left ventricle
RA – right atria
LA – Left atria
The tempo of the
heart is set by:
SA node (mainly)
Nerves
Hormones
Body temp
viii.
4. Fig. 42.3 pg. 874
Fish  two main chambers (one atriaum, one ventricle); TWO
CHAMBERED HEART; single circuit (systemic circulation)
1. Path of Blood: Pumped from ventricle  gills (exchange CO2 for
O2)  capillary beds (oxygenates rest of body)  veins  atrium
Amphibians  three main chambers (two atria, one ventricle); THREE
CHAMBERED HEART; double circulation (both systemic and
pulmocutaneous circulation)
Mammals and Birds four chambers (two atria, two ventricles); FOUR
CHAMBERED HEART; double circulation
1. Evolved to support the endothermic way of life
2. Pumping cycle of Mammalian Heart
a. RV pumps to lungs via pulmonary artery
b. Blood gets oxygenated and returned to the LA
SUMMARY
c. Flows to LV
RV = pumps blood to lungs
d. Gets pumped to body via aorta
LA = collects oxygen rich
e. Gives O2 to body and picks up CO2
blood from lungs
f. Blood comes back to RA via 2 vena cava LV = pumps blood to rest of
g. Flows into the RV to go back to the lungs body
3. Fig. 42.4 pg. 875
RA = collects oxygen poor
4. Regulated by cardiac cycle
blood from body and sends it to
RV
a. Systole = contraction phase
b. Diastole = relaxation phase
c. Cardiac output = amt of blood pumped per minute;
regulated by two things:
i. Heart rate (beats/min)
ii. Stroke volume (amt pumped by LV)
d. Fig. 42.6 pg. 876
5. Valves of the Heart
a. AV (Atrioventricular) valve  between each atrium and
ventricle; keeps blood from flowing back into the atria
b. Semilunar valve  at the two exits of the heart (where
aorta leaves the LV and where the pulmonary artery leaves
the RV); prevents blood from flowing back into the
ventricles
c. Heart Murmur = defect in one or more of the valves
6. Pacemaker of the heart  Sinoatrial (SA) node = sets the rate and
timing at which all the cardiac muscles contract
a. Makes sure the atria contract in unison and then, once they
are emptied, the ventricles all contract in unison
b. Uses electrical currents to maintain timing
Structural Differences in arteries, veins, and capillaries (correlate with
function)
1. Arteries  three layers of tissue; innermost layer = endothelium
(flattened cells; minimize resistance to blood flow; good for
diffusion); thick middle and outer layers for strength when
pumping blood
2. Veins  three layers of tissue; thinner middle and outer layers
than arteries
3. Capillaries  only the endothelium (one layer); facilitates
exchange of substances
4. Fig 42.9 pg. 878
ix. Blood Pressure
1. Highest in arteries during times of contraction (systole); lower in
veins
2. Stress raises blood pressure b/c it constricts blood vessels
3. BP is determined by both cardiac output AND peripheral
resistance (the impedance of blood flow by the arterioles)
4. When being measured, the first number is the systolic pressure
(contraction) and the second number is the diastolic number
(relaxation)
x. Lymphatic System
1. Helps defend the body against infection and maintains the volume
and protein concentration of the blood
2. See Fig 42.13 pg. 881
d. Blood
i. Blood is connective tissue with cells suspended in plasma (liquid matrix)
ii. When taking blood, you can separate out the cellular parts and the plasma
iii. Plasma
1. Composition = 90% water and inorganic salts
2. It is important in maintaining osmotic balance in the blood and
help buffer the blood
3. The kidney maintains plasma electrolytes at specific concentrations
iv. Cellular components
1. Two major classes: red blood cells (RBC’S) and white blood cells
(WBC’s)
2. Red Blood Cells (erythrocytes)
a. Function = transport oxygen
b. Most numerous
c. Large SA for diffusion
d. Lack nuclei (therefore more space for hemoglobin, about
250 million per cell)
e. Hemoglobin = iron-containing protein that transports
oxygen
f. Lack mitochondria and make ATP via anaerobic
metabolism
g. Lifespan = about 3-4 months
3. White Blood Cells (leukocytes)
a. Function = fight infection
b. Spend most of their time outside the circ. system in the
interstitial fluid and the lymphatic system
II.
c. 5 types:
i. Monocytes (phagocyte)
ii. Neutrophils (phagocyte)
iii. Lymphocytes (B and T cells – see Ch. 43)
iv. Basophils
v. Eosinophils
4. Platelets
a. Function = clotting
b. Fragments of cells; no nuclei
5. All the cellular elements in blood are made from pluripotent stem
cells (potential to differentiate into any type of blood cell) in the
red marrow of bones
v. Blood Clotting
1. Blood contains a sealant that clots the blood; it is always present in
its inactive form called fibrinogen.
2. When the blood needs to clot, the plasma protein fibrinogen is
converted to the active form fibrin (change is caused by release of
clotting factors; mechanism is not fully understood)
e. Cardiovascular Disease is the leading cause of Death in the US
i. Heat attack = death of cardiac muscle tissue; resulting from blockage of
one or more coronary arteries (arteries that supply oxygen-rich blood to
the heart)
ii. Stroke = death of nervous tissue in the brain; due to blockage/rupture of
arteries in the head
iii. Atherosclerosis = plaques develop on the arteries and narrow their
diameter
iv. Arteriosclerosis = hardening of the arteries; a form of atherosclerosis
v. Hypertension = high blood pressure; promotes atherosclerosis and
increases risk of heart attack and stroke; controlled by diet, exercise, and
healthy life style
vi. These diseases are partially genetic; also due to lifestyle
vii. Cholesterol
1. LDL’s (low-density lipoprotein) = “bad cholesterol”; forms
plaques
2. HDL’s (high-density lipoprotein) = “good cholesterol”; reduce
cholesterol deposition
Gas Exchange in Animals (Respiratory System)
a. Respiratory medium = source of oxygen (aquatic animals = water; terrestrial
animals = air)
b. Respiratory surface = part of animal where gases are exchanged
i. Usually thin and have large surface areas
ii. Must be moist
iii. Some animals use entire outer skin as a respiratory surface (ex.
Earthworm)
iv. Most common respiratory organs = gills, tracheae, lungs
c. Gills
i. Outfoldings of the body surface that are suspended in water
ii. HIGH surface area
iii. Problems with getting oxygen from water:
1. Oxygen concentration in water are low (as compared to air)
2. The warmer and saltier the water, the less dissolved oxygen it can
hold
iv. Ventilation  process that increases the flow of water over the gills to
maximize oxygen consumption
v. Countercurrent Exchange  efficient process of oxygen being transferred
from the water to the blood
1. The blood travels through the capillaries the opposite way of how
the water is flowing over the gills
2. As blood moves through the gill capillary, it becomes more and
more loaded with oxygen, but it simultaneously encounters water
with even higher oxygen concentrations because the water is just
beginning its passage over the gills; THIS MEANS THAT
ALONG THE ENTIRE LENGTH OF THE CAPILLARY,
THERE IS A DIFFUSION GRADIENT FAVORING THE
TRANSFER OF OXYGEN FROM THE WATER TO THE
BLOOD!
3. Because of the efficiency of the countercurrent exchange system,
the gills can remove 80% of the oxygen dissolved in the water
passing over the respiratory surface
4. Fig. 42.20 pg. 888 and Fig. 42.21 pg. 888
d. Tracheal Systems
i. Found in insects
ii. Made up of air tubes that go throughout the body; largest tubes (tracheae)
open to the outside
iii. Tracheoles (smaller tubes) take oxygen to the individual body cells
e. Lungs
i. Circulatory system transports gases between lungs and rest of body
ii. Amphibians  small lungs, also rely on diffusion (through skin for
example)
iii. Birds, Mammals, and most Reptiles  rely entirely on lungs for gas
exchange
f. Mammalian Respiratory System
i. Located in thoracic cavity
ii. Lungs have a spongy texture with a honeycombed/moist epithelium that
acts as the respiratory surface
iii. Path of air:
Nostrils  nasal cavity  pharynx (path where air and food
crosses)  larynx (voicebox/ upper part of resp. tract)  trachea
(windpipe)  lungs
1. glottis = opening of the windpipe; when open, we can breathe
2. epiglottis = covers the glottis when food is there so it doesn’t go
“down the wrong pipe”
iv. Trachea forks into two bronchi, one leading to each lung
1. Each of these branch into finer and finer tubes called bronchioles
2. Bronchioles dead end into air sacs called alveoli, which is where
gas exchange occurs
v. Process that ventilates lungs is called breathing
1. Negative pressure breathing  process by which mammals
ventilate their lungs; PULL air into lungs instead of PUSHING it
2. Positive pressure breathing  how frogs ventilate their lungs;
PUSH air into their lungs instead of PULLING it
vi. Diaphragm  sheet of skeletal muscle that forms the bottom wall of the
chest cavity
1. Inhalation = diaphragm contracts; moves down; lung volume
increased
2. Exhalation = diaphragm relaxes; moves up; lung volume reduced
3. Fig. 42.24 pg. 891 = important!
vii. Tidal volume  volume of air animal inhales and exhales with each
breath
viii. Vital capacity  maximum tidal volume
ix. Residual volume  amount of air that remains in the lungs even after we
forcefully exhale as much as we can (can never deflate the alveoli
completely)
1. When we get old, lungs lose their resilience and the newly inhaled
air is mixed with old oxygen-depleated air; this increases the
residual volume and decreases the tidal volume = limits
effectiveness of gas exchange!
g. Control centers in brain regulate rate and depth of breathing
i. Automatic mechanisms regulate our breathing; coordinates respiratory
system with cardiovascular system
ii. Breathing Control centers are located in two part of the brain = medulla
oblongata and the pons
1. Sets the basic breathing rhythm
2. Uses negative feedback so the lungs don’t overexpand
3. Works by monitoring level of CO2 in blood and regulates breathing
accordingly
a. CO2 reacts with H20 to form carbonic acid, which lowers
pH
b. When the Medulla recognizes a lower pH, it increases the
depth and rate of breathing
iii. Hyperventilating = tricks the breathing center; messes up CO2 to O2 ratio
iv. Breathing center responds to a variety of nervous and chemical signals and
adjusts the rate and depth of breathing to meet the changing demands of
the body
v. Fig. 42. 26 pg. 893
h. Partial Pressure = concentration of gasses; a fraction of the total pressure
i. A gas will always diffuse from an area of higher partial pressure to one of
lower
ii. Ex. Blood arriving at the lungs from the heart has a lower PO2 and a
higher PCO2
iii. Fig. 42.27 pg. 894
i. Respiratory Pigments
i. Major problem: low solubility of oxygen in water
ii. Most animals use special proteins called respiratory pigments that bind
oxygen and circulate with the blood (instead of using dissolved O2 in the
solution)
1. This greatly increases the amount of oxygen that can be carried in
the blood
2. Hemocyanin  found in the hemolymph of arthropods and many
mollusks; has copper as its O2 binding component
3. Hemoglobin  resp. pigment used by almost all vertebrates
a. Found in red blood cells
b. Made of 4 subunits; each with an iron center
c. Iron binds O2; so each hemoglobin molecule can carry 4
molecules of O2
d. Hemoglobin’s conformation is sensitive; ex. Drop in pH
lowers the affinity of hemoglobin for O2
iii. CO2 transport
1. Hemoglobin also helps transport CO2 and helps in buffering
2. 70% of CO2 is transported in the blood in the form of bicarbonate
ions, which diffuses into the plasma