the circulatory and respiratory systems chapter 49
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The Circulatory andRespiratory Systems
Chapter 49
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Invertebrate Circulatory SystemsSponges, Cnidarians, and nematodes lack a
separate circulatory system
-Sponges circulate water using many incurrent pores and one excurrent pore
-Hydra circulates water through a gastrovascular cavity (also for digestion)
-Nematodes are thin enough that the digestive tract can also be used as a circulatory system
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Invertebrate Circulatory SystemsLarger animals require a separate circulatory
system for nutrient and waste transport
-Open circulatory system = No distinction between circulating and extracellular fluid
-Fluid called hemolymph
-Closed circulatory system = Distinct circulatory fluid enclosed in blood vessels & transported away from and back to the heart
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Vertebrate Circulatory Systems
Mammals, birds and crocodilians have a four-chambered heart with two separate atria and two separate ventricles
-Right atrium receives deoxygenated blood from the body and delivers it to the right ventricle, which pumps it to the lungs
-Left atrium receives oxygenated blood from the lungs and delivers it to the left ventricle, which pumps it to rest of the body
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Later-Evolved Vertebrate Circulatory Systems
-Oxygenated and deoxygenated blood don’t mix in heart
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Heart Valves
The heart has two pairs of valves:
-Atrioventricular (AV) valves guard the openings between atria and ventricles
-Tricuspid valve = On the right
-Bicuspid, or mitral, valve = On the left
-Semilunar valves guard the exits from the ventricles to the arterial system
-Pulmonary valve = On the right
-Aortic valve = On the left
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The Cardiac CycleThese valves open and close as the heart
goes through the cardiac cycle of rest (diastole) and contraction (systole)
-“Lub-dub” sounds heard with stethoscope
-Systolic pressure is the peak pressure at which ventricles are contracting AV valves close (to prevent backwash)= “lub”
-Diastolic pressure is the minimum pressure between heartbeats at which the ventricles are relaxed, semilunar valves close = (to prevent backwash)“dub”
-Blood pressure is written as a ratio of systolic over diastolic pressure
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Contraction of Heart Muscle
Electrocardiogram (ECG or EKG)
Autorhythmic SA node
Initiates
depolarization
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Characteristics of Blood Vessels
*Arteries and veins are composed of four tissue layers
*Capillaries are composed of only a single layer of
endothelial cells...They allow for rapid exchange of
gases and metabolites between blood and body cells
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Arteries and Arterioles Regulate Heat Loss
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Cardiovascular Diseases
Atherosclerosis
-Accumulation of fatty material within arteries
Arteriosclerosis
-Arterial hardening due to calcium deposition
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Blood Flow and Blood Pressure
Blood flow and pressure are regulated by the autonomic nervous system
The cardiac center of the medulla oblongata modulates heart rate
-Norepinephrine, from sympathetic neurons, increases heart rate
-Acetylcholine, from parasympathetic neurons, decreases heart rate
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Blood Flow and Blood Pressure
Cardiac output is the volume of blood pumped by each ventricle per minute
-Increases during exertion because of an increase in both heart rate & stroke volume
Arterial blood pressure (BP) depends on the cardiac output (CO) and the resistance (R) to blood flow in the vascular system
BP = CO x R
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Blood Flow and Blood Pressure
The baroreceptor reflex is a negative feedback loop that responds to BP changes
-Baroreceptors detect changes in arterial BP
-If BP decreases, the number of impulses to cardiac center is decreased
-Ultimately resulting in BP increase
...and vice versa.
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Veins and Venules
Veins and venules
-Have thinner layer of smooth muscles than arteries
-Return blood to the heart with the help of skeletal muscle contractions and one-way venous valves
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A connective tissue composed of a fluid extracellular matrix, called plasma, within which are found different cells and formed elements
What is Blood?
The functions of circulating blood are:
1. Transportation of materials
2. Regulation of body functions
3. Protection from injury and invasion
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The Components of Blood
Plasma is 92% water, but it also contains the following solutes:
-Nutrients, wastes, and hormones
-Ions
-Proteins
-Albumin, alpha () & beta () globulins
-Fibrinogen
-If removed, plasma is called serum
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The Components of Blood
The formed elements of the blood include red blood cells, white blood cells and platelets
Red blood cells (erythrocytes)
-About 5 million per microliter of blood
-Hematocrit is the fraction of the total blood volume occupied by red blood cells
-RBCs of vertebrates contain hemoglobin, a pigment that binds and transports oxygen
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White Blood Cells
White blood cells (leukocytes)
-Less than 1% of blood cells
-Larger than erythrocytes and have nuclei
-Can also migrate out of capillaries
-Granular leukocytes
-Neutrophils, eosinophils, and basophils
-Agranular leukocytes
-Monocytes and lymphocytes
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4. Threads of fibrin trap erythrocytes and form a clot.
1. Vessel is damaged, exposing surrounding tissue to blood.
5. Once tissue damage is healed, the clot is dissolved.
3. Cascade of enzymatic reactions is triggered by platelets, plasma factors, and damaged tissue.
2. Platelets adhere and become sticky, forming a plug.
Prothrombin
Thrombin
Thrombin
Fibrinogen
Fibrin
The Components of Blood
Platelets are cell fragments that pinch off from larger cells in the bone marrow
-Function in the formation of blood clots
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All of the “formed elements”
develop from pluripotent
stem cells
Hematopoiesis is blood
cell production
-Occurs in the bone
marrow of (medullary bone),
and produces:
-Lymphoid stem cell...Lymphocytes
-Myeloid stem cell...All other blood cells
Red blood cell production
is called erythropoiesis
Making Blood “Formed Elements”
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LungsGills were replaced in terrestrial animals because
1. Air is less supportive than water
2. Water evaporates
The lung minimizes
evaporation by moving
air through a branched
tubular passage
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Gas Exchange
Gases diffuse directly into unicellular organisms
However, most multicellular animals require system adaptations to enhance gas exchange
-Amphibians respire across their skin
-Echinoderms have protruding papulae
-Insects have an extensive tracheal system
-Fish use gills
-Mammals have a large network of alveoli
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Gills
Gills are specialized extensions of tissue that project into water
External gills are not enclosed within body structures
-Found in immature fish and amphibians
-Two main disadvantages
-Must be constantly moved to ensure contact with oxygen-rich fresh water
-Are easily damaged
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Gills
The gills of bony fishes are located between the oral (buccal or mouth) cavity and the opercular cavities
-These two sets of cavities function as pumps that alternately expand
-Moving water into the mouth, through the gills, and out of the fish through
the open operculum or gill cover
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Gills
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Gills
There are four gill arches on each side of a fish’s head
-Each is composed of two rows of gill filaments, which consist of lamellae
-Within each lamella, blood flows opposite to direction of water movement
-Countercurrent flow
-Maximizes oxygenation of blood
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Gas Exchange
The rate of diffusion between two regions is governed by Fick’s law of diffusion
R =D A p
dR = Rate of diffusion
D = Diffusion constant
A = Area over which diffusion takes places
p = Pressure difference between two sides
d = Distance over which diffusion occurs
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Lungs
-Lungs of mammals are packed with millions of alveoli (sites of gas exchange)
-Inhaled air passes through the larynx, glottis and trachea
-Bifurcates into the right and left bronchi, which enter each lung and further subdivide into bronchioles
-Surrounded by an extensive capillary network
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LungsAir exerts a pressure downward, due to gravity
-A pressure of 760 mm Hg is defined as one atmosphere (1.0 atm) of pressure
Partial pressure is the pressure contributed by a gas to the total atmospheric pressure-Based on the % of the gas in dry air-PN2 = 760 x 79.02% = 600.6 mm Hg
-PO2 = 760 x 20.95% = 159.2 mm Hg
-PCO2 = 760 x 0.03% = 0.2 mm Hg
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Lungs
Lungs of amphibians are formed as saclike outpouchings of the gut
Frogs have positive pressure breathing
-Force air into their lungs by creating a positive pressure in the buccal cavity
Reptiles have negative pressure breathing
-Expand rib cages by muscular contractions, creating lower pressure inside the lungs
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Lung Structure and Function
During inhalation, thoracic volume increases through contraction of two muscle sets
-Contraction of the external intercostal muscles expands the rib cage
-Contraction of the diaphragm expands the volume of thorax and lungs
-Produces negative pressure which draws air into the lungs
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Lung Structure and Function
Tidal volume = Volume of air moving in and out of lungs in a person at rest
Vital capacity = Maximum amount of air that can be expired after a forceful inspiration
Hypoventilation = Insufficient breathing-Blood has abnormally high PCO2
Hyperventilation = Excessive breathing-Blood has abnormally low PCO2
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Lung Structure and Function
Each breath is initiated by neurons in a respiratory control center in the medulla oblongata
-Stimulate external intercostal muscles and diaphragm to contract, causing inhalation
-When neurons stop producing impulses, respiratory muscles relax, and
exhalation occurs
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Gas Exchange
Gas exchange is driven by
differences in partial pressures
-As a result of gas exchange
in the lungs, systemic arteries
carry oxygenated blood with
relatively low CO2 concentration
-After the oxygen is
unloaded to the tissues,
systemic veins carry
deoxygenated blood with a high
CO2 concentration
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Lung Structure and Function
Neurons are sensitive to blood PCO2 changes
-A rise in PCO2 causes increased production of carbonic acid (H2CO3), lowering the pH
-Stimulates chemosensitive neurons in the aortic and carotid bodies
-Send impulses to control center
Brain also contains central chemoreceptors that are sensitive to changes in the pH of cerebrospinal fluid (CSF)
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Lung Structure and Function
-Each breath is initiated by neurons in a respiratory control center in the medulla oblongata
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Respiratory Diseases
Chronic obstructive pulmonary disease (COPD) refers to any disorder that obstructs airflow on a long-term basis
-Asthma = An allergen triggers the release of histamine, causing intense constriction of the bronchi and sometimes suffocation
-Emphysema = Alveolar walls break down and the lung exhibits larger but fewer alveoli
-Lungs become less elastic
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Respiratory Diseases
Lung cancer follows or accompanies COPD
-The number one cancer killer
-Caused mainly by cigarette smoking
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RBCs of vertebrates contain Hemoglobin,
a pigment that binds and transports oxygen
Hemoglobin consists of four polypeptide chains: two and two -Each chain is associated with a heme group, and each heme group has a central iron atom that can bind a molecule of O2
Hemoglobin loads up with oxygen in the lungs, forming oxyhemoglobin
-Some molecules lose O2 as blood passes in capillaries, forming deoxyhemoglobin
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Hemoglobin
In a person at rest, about one-fifth of the oxygen is unloaded in the tissues
-Leaving four-fifths of the oxygen in the blood as a reserve
-This reserve enables the blood to supply body’s oxygen needs during exertion
The oxyhemoglobin dissociation curve is a graphic representation of these changes
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Hemoglobin
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Hemoglobin
Hemoglobin’s affinity for O2 is affected by pH and temperature
-The pH effect is known as the Bohr shift
-Caused by H+ binding to hemoglobin
-Results in a shift of oxyhemoglobin dissociation curve to the right
-Facilitates oxygen unloading
-Increasing temperature has a similar effect
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Hemoglobin
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-Mitochondria release CO2 after pyruvate oxidation and the Krebs Cycle
Mitochondria also reduce oxygen to H20 (water) at the end of the electron transport chain.
C02 leaves tissue cells
Gas Exchange BiochemistryIn Tissue Cells
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-The enzyme carbonic anhydrase combines CO2 with H2O to form H2CO3
-H2CO3 dissociates into H+ and HCO3
–
-H+ binds to deoxyhemoglobinmaking O2 get into tissue
-HCO3– moves out of the
blood, and into plasmaacts as buffer
72% of the CO2 in blood is“hidden” in HCO3
Gas Exchange BiochemistryIn Red Blood Cells & Plasma
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-CO2 goes into Alveoli...HCO3– moves INTO red blood cells
-H+ and HCO3– associate
into H2CO3
-H2CO3 changes into CO2
with H2O
-CO2 leaves Red Blood Cellsand goes into the alveoli
THEN YOU EXHALE IT...Bronchioles, bronchi,trachea, pharynx, mouth,atmosphere!!
Gas Exchange BiochemistryInto Alveoli
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When blood passes through pulmonary capillaries, these reactions are reversed
-The result is the production of CO2 gas, which is exhaled
Other dissolved gases are also transported by hemoglobin-For example, nitric oxide (NO) and carbon monoxide (CO)...so these molecules compete with, oxygen, the terminal electron acceptor in the electron transport chain...can be deadly
Transportation of Carbon Dioxide