Body systems unit 1
What does the blood transport around the body?
Oxygen, nutrients, antibodies, Hormones, heat, carbon dioxide, urea
What are Erythrocytes
Erythrocytes are red blood cells. They transport oxygen from the lungs to respiring cells, and carbon dioxide from respiring cells to the lungs.
What is plasma?
Plasma s a solvent which transports nutrients (from gut to liver), hormones, urea (liver to kidney), dissolved proteins and antibodies, gases and waste.
What is urea?
a compound that is excreted to remove nitrogen from the body
Red blood cells adaptations to function
They have no nucleus to allow space for more hemoglobin. They have a cytoplasm with a large number of hemoglobin, and their shape gives a large surface area to volume ratio.
What are arteries?
Arteries are blood vessels that cary high pressure blood away from the heart. They have a relatively small lumen (hollow central chamber) in relation to the wall to maintain a high blood pressure.
What are capillaries?
Capillaries are a very small blood vessel and therefore can penetrate virtually every tissue in the body. Blood moves slowly through them under low pressure providing opportunities for the exchange of substances.
What are veins?
Veins are blood vessels that carry low pressure blood back to the heart, using valves to ensure the correct direction.
Vasoconstriction
The small lumen maintains a high blood pressure. Muscle contracts to decrease the size of the lumen (called vasoconstriction) and increases blood pressure, allowing it to maintain a high blood pressure between pulses of blood travelling from the heart.
Vasodilation
When the muscles relax (called vasodilation), it decreases blood pressure.
Function of elastic fibres in arteries
Elastic fibres are able to stretch to increase the lumen with each pulse of blood. After the pulse of blood passes through, the fibres recoil to decrease the lumen size and maintain a high blood pressure. The pressure exeted on the arterial wall is returned to the blood when the artery returns to its normal size (elastic recoil). This helps push the blood forward through the artery.
Flow of blood in arteries (pulses)
Blood is expelled from the heart when it contracts, allowing it to flow through the arteries in repeated surges called pulses.
Function of muscle fibres in arteries
Muscle fibres help to form a rigid arterial wall that is capable of withstanding the high blood pressure without rupturing. They can also contract to help narrow the lumen.
The function of the structure of the capillaries
Capillaries are the smallest blood vessels, they are only one cell thick which enables tissues to gain nutrients and molecules (oxygen), and rid themselves of waste materials via diffusion. The branching of arteries into a capillaries ensures blood moves slowly and all cells are located near a blood supply.
Flow of blood in capillaries
Blood flows throught he capillaries very slowly and at a very low pressure to allow for maximal material exchange. The hgih blood pressure from arteries is dissipated by extensibe branching of the vessels and narrowing of the lumen.
Flow of tissue fluid in capillaries
The higher pressure at arteriole end of the capillary forces material from the bloodstream into the tissue fluid (materials include oxygen and nutrients). Lower pressure at the venule end allows materials from the tissues to enter the bloodstream (carbon dioxide, urea). Tissue fluid is formed by pressure filtration of plasma in capillaries.
Draining excess tissue fluid into lymph ducts
Excess tissue fluid will be absorbed by vessels of the lymphatic system. This prevents tissue swelling (edema). Lymphatic vessels have permeable walls through which tissue fluid can pass, and valves to prevent backflow. The lymph flows into two wider lymphatic vessels and merges into the veins.
Adaptations of veins for returning blood to the heart
The large lumen in veinis means that the blood is under low pressure. The walls are thinner and less elastic, as well as containing less muscle than arteries. Veins have vales to prevent the back-flow of blood to ensure it moves towards the heart.
Flow of blood in veins
Because the blood is at low pressure it can make it difficult for blood to move against the flow of gravity in the veins. The veins contain valves to prevent this. Veins also pass between skeletal muscle groups (when skeletal muscles contract they squeeze the vein and cause blood to flow from the site of compression). This effect can also be caused by arterial bulging created by the pulse as veins run parallel to them.
Pressure changes along blood vessels
Blood leabing the heart (into arteries) is under high pressure and travels in pulses that follow each heartbeat. By the time the blood has reached the capillaries, it is under lower pressure without a pulse. By the time it reaches the veins, the pressure is almost 0 mm Hg.
What is systolic pressure
the pressure of the arteries when the ventricles are contracting
What is diastolic pressure
the pressure in the arteries when the ventricles are relaxed
Velocity changes along blood vessels
Blood has a high velocity in arteries and a low velocity in the capillaries. When the blood goes into the veins the speed increases (because of diameter)
Measuring pulse
Ventricular contractions cause blood to be expelled into the arteries, causing their expansion which can be felt as a pulse near the skin surface and where it passes over a bone. Two fingers compress the artery and the number of beats per minute can be counted, typically on the neck (carotid artery) or the wrist (radial artery). Other methods like pulse oximeters or heart rate monitors can be used.
Single circulation (fish)
Fish pump blood through capillaties to their gills where gas exchange happens. The capillaries do not burst under high pressure because of the water. After the blood is oxygenated, there is enough pressure to push the blood to the organs, and when doexygenated the pressure falls and blood must return to the heart.
Double circulation (mammals)
Blood flows from the heart through two different circuits, one through the lungs and the other throughout the rest of the body.
Pulmonary circulation
Blood moving from the heart to the lungs and back. Deoxygenated blood enters the right atrium and travels through the tricuspid valve into the right ventricle. The right ventricle fills with blood and contracts, causing the closure of the tricuspid valve to prevent backflow and a dramatic increase in blood pressure in the right ventricle that opens the semilunar valve and allows blood to enter the pulmonary artery. The increasing pressure causes blood to leave the heart through the pulmonary artery.
Systemic circulation
The route the blood takes from the heart to the rest of the body and back. Oxygenated blood enters the left atrium and travels through the mitral valve into the left ventricle. The left ventricle fill with blood and contracts, causing the closure of the mitral valve to prevent backflow and a dramatic increase in blood pressure inside the left ventricle which opens the aortic valve and allows blood to enter the aorta.
Adaptations of cardiac muscle
Cardiac muscle fibres have cylindrical branching columns of fibres that form a three dimensional network (allows for contraction in three dimensions). Each fibre has a single nucleus and are striped or striated. Fibres are surrounded by a plasma membrane called the sarcolemma.
Atherosclerosis
Areas of the atery become damaged (degenerative). Macrophages release growth factors that cause fibrous tissue to grow. Cholesterol builds up in the damaged area and form a plaque that makes the artery wall less elastic. As this combination forms (atheroma), the lumen narrows and restricts blood flow (coronary occlusion). Lack of oxygen and nutrients to the heart from blood impairs the heart's ability to contract and causes pain (angina). If the plaque ruptures, blood clotting is triggered (coronary thrombosis).
Coronary heart disease
Blood clotting from atherosclerosis in myocardial tissue is called coronary heart disease. A heart attack (myocardial infraction) occurs if a coronary artery becomes completely blocked. Muscle tissue dies as a result of the lack of blood and oxygen. The blockages are typically trated by the creating of a stent in surgery (balloon angioplasty).
Risk factors of coronary heart disease
those pre-disposed for high cholesterol levels and high blood pressure, older people (less elastic arteries), males at higher risk, smokers, those with more fatty diet, lack of excercise (weakened circulation), obesity (increased blood pressure), stress (cortisol in blood causes increased atherosclerosis), hormonal contraceptives (increases risk of thrombosis)
control of the heartbeat
The myocote (muscle cell) itself is the origin of the heart's contraction and is not controlled externally (called myogenic muscle contraction). A region of myocotes called the sinoatrial node (pacemaker) controls the rate of the heartbeat, truggering roughly 60-100 cardiac coontractions per min. If it fails, a secondary pacemaker (AV node) maintains contractions at roughly 40-60 bpm. If both fail the bundle of his contracts at a constant rate of 30-40 bpm. Cardiac muscle cannot tire out.
Cardiac cycle (atrial systole)
Passive filling from pulmonary veins and vena cava. The atria contract, forcing blood into the ventricals. Pressure increases slowly, AV vales are open, but the SL is still closed.
Cardiac cycle (early ventricular systole)
Isovolumetric contraction of the ventricles (volume increases under equal pressure until the av valves close - lub). Semilunar valves are still closed, because the pressure in Aorta and pulmonary arteries is still higher than in the ventricles.
Cardiac cycle (late ventricular systole)
Ventricular contraction continues. Pressure in the ventricles exceeds the pressure in the pulmonary artery and aorta, causing the SL valves to be pushed open and blood is ejected.
Cardiac cycle (early ventricular diastole)
The ventricles relax. Pressure in the ventricles fall rapidly. the SL valvves close shut due to backdrop of blood - dub. Passive ventricular filling starts.
Cardiac cycle (atrial and ventricular diastole)
continued passive filling of both atria and ventricles through open AV valves due to backflow of blood from vena cava inferior/superior, and the pulmonary vein. The pressure in the aorta is much higher than in the left ventricle, which causes semilunar valves to be closed.
Causes of accelerated or slowed heart rate
Excercise causes more co2 to be present in the blood, dectected by chemoreceptors in the medulla oblongata and resulting in a nerve signal being sent to the SA node to speed up the heart rate, when co2 falls, the vagus nerve reduces the heart rate. Adreneline can also caused an increase in fight-or-flight responses and a rapid increase in heart rate, which can also be mimicked by drugs. Acetylcholine slows the firing of the SA node.
Recording the heart rate
heart function can be assessed by measuring the electrical activity of the heart with each contraction. Activity is measured using a machine called an electrocardiograph.
PQRST wave
The P wave represents depolarization of the atria in response to signalling from the SA node. The QRS complex represents depolarization of the ventricles triggered by signals from the AV node. The T wave represents repolarization of the ventricles and the completionof a standard heart beat. Between these periods (PR and ST intervals) there are intervals allowing for blood flow.
The heart beat (cardiac cycle)
1. The wave of excitations is sent from the sinoatrial node, causing the atria to contract.
2. The impulses reach another node located near the area on the partition between two ventricles called the atrioventricular, or A-V node.
3. It transmits the electrical impulses down the septum via fibers called the bundle of His and then into the Purkinje fibers which spread over the ventricles. This causes the ventricles to contract
Heart conditions data (electrocardiography)
Tachycardia (elevated resting rate) and bradycardia (depressed resting rate). Arrhythmias (irregular heat beats so common in young people that its not considered a disease). Fibrillations (unsynchronized contractions of either atria or ventricles)
Changes in blood supply to organs in response to activity
Skeletal muscle: increased during excercise, moderate in wakeful rest, reduced during sleep. Digestive system: reduced during excercise, variable during wakeful rest, variable during sleep. Kidneys: reduced during excercise, maximal during wakeful rest, reduced during sleep. Brain: increased during excercise, moderate during wakeful rest, increased during sleep
Ventilation
movement of air into and out of the lungs in two stages: inspiration and expration, This is controlled by movement of the diaphragm and ribcage.
Gas exchange
the exchange (diffusion) of oxygen and carbon dioxide to and from the blood at the alveoli and the respiring tissues
Properties of gas exchange surfaces
There is a large variety of different gas exchange surfaces in plants and animals. Some may lack an open or closed circulatory system and exchange gases with the environment directly. However all gas exchange surfaces share 4 properties: Permeable to Co2 and O2, large surface area, moist, and thin
Adaptation of Mammalian lungs for gas exchange
The larger the animal, the greater the suface area for the exchange of gases has to be. Our lungs are moist membranes to allow gases to diffuse as they need moist surfaces to do so (we are landborne). The ventilation system maintains a concentration gradient between alveoli and the blood.
Type I Pneumocytes
A single layer of cells form the walls of alveolus. Extremely thin (short diffusion distance), permeable - aids diffusion.
Type II pneumocytes
Secrete fluid to moisten the inner surface of the alveolus. Fluid aids diffusion of gasses and contains a surfactant to prevent the walls sticking together (maintains the lumen). Can divide to form type I pneumocytes and repair damage
Lamellar bodies (type II penumocytes)
They are specialized secretory vesicles which store the large amounts of phospholipids and proteins produced by the rER. The contents of the lamellar bodies are secreted by exocytosis and form the surfactant.
Lung surfactant
produced and released by type II alveolar cells and results in the formation of a moist film covering the inner lining of the alveoli. It is a detergent-like mixture of lipoproteins and phospholipid-rich secretion with hydrophilic and hydrophobic areas that line the inner surface of the alveoli.
Purposes of surfactant
In lungs, the surfactant layer reduces the surface tension of the alveolus and the moisture facilitates the diffusion of gases. The pulmonary surfactants form a single layer on the surface of the moisture lining of alveoli and help to prevent lung collapse when air is exhaled.
Surfactant in lungs with penumonia
Lungs affected by penumonia or other lung diseases cannot produce sufficient surfactant, leading to a collapse of the alveolus
Concentration gradients in the ventilation system
High concentration gradients must be maintained in the alveoli. Breathing in increases the concentration gradient of oxygen between the alveoli and blood. Breathing out removes co2 and unused o2. The continuous movement of blood throughout the dense network of blood vessels ensures a low concentration of o2 as blood which has become enriched with o2 is imeediately moved away.
Concentration gradients in gils (ventilation)
Movement of water through the gills ensures a high concentration of 02 and low concentration of c02 outside the gills
Oxygen dissociation curves
A graph showing the percentage saturation (of oxygen) of hemoglobin against the concentration of available oxygen. The concentrationo f oxygen is usually shows as partial pressure of oxygen in air (kPa). Partial pressure of oxygen is the pressure of it in a mixture of gases.
What is cooperative binding?
When oxygen binds to a heme group, conformational changes are caused that increase the oxygen affinity of other heme groups.
Oxygen saturation in hemoglobin
Positvely correlated with oxygen concentration, but not directly proportional. It changes from fulls saturated to unsaturated over a relatively narrow range of oxygen concentrations (s shaped curve on a graph). This is because of cooperative binding. Because the shape of hemoglobin is altered as each oxygen molecule binds, each successive binding of oxygen is made easier.
cooperative binding in oxygen-rich areas
The higher affinity of hemoglobin results in the promotion of oxygen loading and higher chances of reaching saturation levels (even when concentration gradients are steep)
cooperative binding in oxygen-poor areas
The successively lower oxygen affinity promotes oxygen unloading in areas where high cellular respiration takes place.
adaptations of fetal hemoglobin for transporting oxygen
During pregnancy a fetus obtains oxygen from the placentra and the umbilical cord which transports the blood. O2 dssociates from hemoglobin in maternal blood in the placenta and binds to hemoglobin in the fetal blood. The placenta has extensions with capillaries (chorionic villi) that are surrounded by maternal blood, allowing for gas exchange. Maternal blood has higher o2 and lower co2, creating a pressure gradient that allows o2 to flow into the fetal blood and vice versa. Fetal hemoglobin has a stronger affinity for oxygen for this reason.
Inspiration
Occurs when air is taken into the lungs. The diaphragm contracts and moves downward. External intercostal muscles contract and the thoracic cage (ribs) moves upward and outward. The abdominal muscles relax. The volume of the thorax increases and the air pressure in the thoracic cavity decreases. The air pressure in the lungs is now lower than air pressure outside the body, allowing air to rush into the lungs (moves from high pressure to low pressure)
Expiration
Occurs when air is removed from the lungs. Diaphragm relaxes and abdominal muslces contract to move upwards. External intercostal muscles relax and internal intercostal muscles contract causing the thoracic cage to move down and inward. Volume of thorax decreases, air pressure increases inside the lungs, air moves from lungs to lower pressure outside th ebody. Air is aided out by the squeezing of the chest cavity, done by elastic recoil of tissues and muscles.
Tidal volume
The volume of air that is inhaled and exhaled in a normal breathing movement (taken when body is at rest)
inspiratory reserve volume
the addtional volume of air that can be taken into the lungs beyond a regular (tidal) inhalation
expiratory reserve volume
the additional volume of air that can be forced out of the lungs beyound a regular (tidal) exhalation
vital capacity (total lung volume)
the total volume of gas that can be moved into or out of the lungs.
Residual volume
the amount of air that remains in the lungs and passageways even after a full exhalation
Factors determining total lung cpaacity
height (taller = bigger chest), loaction, lifestyle, physical activity
Methods of measuring ventilation
Simple observation (counting number of breaths per minute), chest belt and pressure meter (recording the rise and fall of the chest), and spirometer (recording the volume of gas expelled per breath)
spirometre process
Measures the amount (volume) and/or speed (flow) at which air can be inhaled or exhaled. The spirometer detects the changes in ventilation and presents the data digitally.
displacement method (lung volume bags)
A normal breath is exhaled through the tibe into an inverted vessel and the displaced volume of water can be measured by reading off the remaining water level inside the container.
Vital capacity formula
Male: L = ((27.63 - 0.112 x age in years) x height in cm)/1000
Female: L = ((27.78 - 0.101 x age in years) x height in cm)/1000
Bohr shift
In active tissues co2 diffuses into red blood cells where it reacts with water, creating H+ and Hco3- ions. H+ binds to hemoglobin. A change in H+ concentration in blood causes pH to drop below normal values, causing hemoglobin shape to change as well as oxygen affinity. Co2 lowers the ph of the blood, causing hemoglobin to release its oxygen (bohr effect).
What is a pathogen?
A disease-causing organism, including viruses, bacteria, protozoa, or fungi
Bacteria
No nucleus, prokaryotes that divide by binary fission
fungi
eukaryotes, reproduce with spores, cell walls contain chitin
Protozoa
parasitic or symbiotic, unicellular eukaryotes, making treatment difficult
Helminthic parasites
parasitic dieases, multicellular and eukaryotic
Innate immunity
non-specific defense mechanisims that come into play immediately of an antigen's appearance in the body
adaptive immunity
specific defense mechanisms using antibodies (active and passive)
active immunity
form of adaptive immunity. Immunity due to the production of antibodies by the organism itself after immune response is stimulated by a pathogen
passive immunity
a form of adaptive immunity. The acquisition of anti-bodies from another organism (e.g placenta or breastmilk from mother to baby)
Skin as a barrier to pathogens
Protects external structures, is a thick and tough region made of dead surface cells. Secretes enzymes that inhibit microbial growth, lactic acid and fatty acids to lower pH
Mucous membranes and defense against pathogens
protects internal structures, is a thin region of living surface cells that release fluids to wash away pathogens. Secretes lysozyme that destroys cell walls and cause lysus. Some membranes may be ciliated to aid in removing pathogens. Produces a lining of sticky mucus to trap pathogens.
sealing cuts with blood clotting
When blood vessels are damaged, cells release chemicals that cause platelets to adhere to the area. The tissue and platelets release clotting factors that convert prothrombin (inactive protein) into thrombin (active enzyme). Thrombin catalyzes the conversion of fibrinogen to fibrin, which is a fibrous protein that forms a mesh-like network. Cellular debris gets trapped in the mesh to help form a stable clot.
Lymphocytes
Responsible for the production of antibodies. They are more common in the lymphatic system than blood, the slowest to respond. Lymphocytes include B cells and T cells. They also help with the destruction of virus-infected body vells (via cytotoxic T cells and natural killer cells)
What are macrophages
Large white blood cells that can change their shape to engulf an invader (phagocytosis). They are able to squeeze in and out of small blood vessels. Phagocytes can ingest pathogens in the blood or at the sites of infection. Large numbers of phagocytes at a site of infection form pus.
glycoproteins on cells and recognition
Macriphages recognize cells as either self or not self based on the protein molecules found on the surface of all cells and viruses. This response is called non-specific immunne response as the pathogen is not known at this time.
B cells specificity
each B cell is programmed to make one specific antibody. When a B cell encounters its specific or eliciting antigen it changes into an antibody producing cell.
Antigens
substance or molecule found on a cell or virus surface that causes antibody formation
Antibodies
a globular immunoglobulin protein that recognizes a specific antigen and binds to it to stimulate its destructionm produced by lymphocytes.
cell-mediated immunity
A pathway that does not result in antigen production, but targets endogenous antigens (cancerous and virus infected cells that involve the body's own cells evade detection as they are not seen as foreign). Helper T cells indentify these cells and stimulate cytotoxic T cells. Tc cells release perforating enzymes that cause the target cell to be lysed.
cytotoxic t cell activation
Helper T cells secrete chemicals that activate cytotoxic T cells. They can bind to cells that have been infected by pathogens and secrete chemicals that will kill the infected cell.
B lymphocyte activation
the B cell searches for an antigen matching its receptors, connecting to it. The B cell then waits to be activated by the helper T cells as it needs certain proteins. The T cell activates the B cell by releasing a chemical called cytokines.
clonal selection
activated B cells divide through mitosis to create a clone of plasma cells which all produce the same antibody type. The plasma cells produce a large amount of antibodies and release them into the bloodstream to circulate for a couple weeks.
Memory B-cells
some plasma clones differentiate into memory B-cells. These cells remain inactive unless the same pathogen infects the body again, as lymphocytes that produced the antibodies will be lost once the infection is over.
primary immune response
the initial response to a new pathogen. The immune response in non-specific, and time taken varies depending on the pathogen, but it allows time for symptoms of disease to develop
secondary immune response
The response to a second exposure to a pathogen. Memory B cells differentiate into plasma and quickly produce antibodies (they have large number of rER, which manufactures, modifies, and transports antibodies)