MODULE 4: Circulation and Gas Exchange Flashcards
Open Circulatory System
- one type of fluid (hemolymph)
- heart pulses = fluid out
- heart relaxes = fluid in
- simple to maintain
- less energy/lower pressure
Closed Circulatory System
- two types of fluid
- circulatory fluid never leaves system (blood)
- interstitial fluid on outside
- exchange happens b/w two fluids
- high pressure
- increased efficiency for meeting high metabolic demand
Vein
blood to heart
Artery
blood away from heart
Ventricle
- receives blood from atrium
- left V pumps to all parts of body
- right V pumps to lungs
- works against gravity so has thick muscle
- left V has thickest muscle of heart
Atriums
- blood enters heart through two atria
- deoxeygenated blood enters through right atrium via vena cava and is pumped into pulmonary veins through lungs
- oxygenated blood enters left atrium through pulmonary vein and is pumped into left ventricle
Atrioventricular Valve
b/w atrium and ventricle (both left and right)
Semilunar Valve
- b/w right ventricular and lungs
- b/w left ventricular and aorta
Flow of Blood Through CV System
- right ventricle relaxes
- right ventricle contracts and pushes blood through pulmonary arteries
- blood reaches lungs where exchange occurs
- fresh oxygenated blood collected by pulmonary veins
- empty oxygenated blood into left side
- reaches left atrium and goes to left ventricle
- from left ventricle goes through aorta and is supplied to all parts of the body
- deoxygenated blood collected by posterior & anterior vena cava
- deoxygenated blood goes through right atrium to right ventricle (cycle repeats)
Cardiac Output
= heart rate x stroke volume
= 70 beats/min x 75mL/beat
= 5L/min
- Atrial and Ventricular Diastole
- Atrial Systole and Ventricular Diastole
- Ventricular Systole and Atrial Diastole
- atrioventricular valves open
- semilunar valves closed
- 0.4 seconds
- 0.1 seconds
- atrioventricular valves closed
- semilunar valves open
Pacemaker
- 1% of cells
- generate own AP
- spreads to nonpacemaker cells
Sinoatria Node (SA Node)
- contains pacemaker
- sets rate and timing at which all cardiac muscle contracts
- impulses trave; to atrioventricular node
Atrioventricular Node (AV Node)
- impulses from SA node are delayed
- travel to Purkinje fibres which make ventricles contract
Artery Structure
- endothelium
- smooth muscle
- connective tissue
Capillary Structure
- endothelium
- basement membrane
Vein Structure
- valve
- endothelium
- smooth muscle
- connective tissue
Veins - Skeletal Muscle and Valves
- in thinner walled veins, blood flows back to heart as a result of muscle action and valves
- muscle contracts and valve opens, blood vessel squeezed and blood moves up
- muscle relaxes and valves closes to prevent backflow
Veins - Odema
- pooling of blood in distended veins
- increase filtration = swelling of ankles and feet
Capillaries - Exchange
- exchange of substances b/w blood and interstitial fluid takes place across thing endothelial walls of capillaries
- substances move in and out via pores
- plasma proteins never leave capillary to make process efficient
Capillary Function
- capillaries in major organs usually filled to capacity
- blood supply varies in other sites
- regulates distribution of blood in capillary beds
- contraction of smooth muscle layer in wall of arteriole constricts vessel (e.g. digestive tract during exercise)
Systolic / Diastolic Pressure
Systolic pressure: press in arteries during ventricular systole. Highest pressure in arteries
Diastolic pressure: during ventricular diastole. Lowest pressure in arteries
Laminar Flow
- no sound
- blood flow in same direction
Turbulent Flow
- creates sound
- blood flow in different directions
- laminar flow –> increase pressure to close artery –> decrease pressure –> turbulent flow –> sound
Regulation of Blood Pressure
- partly determined by cardiac output
- nervous & hormonal stimuli can affect contraction of smooth muscle in arteries
- vasoconstriction (smooth muscle) narrows the arteries and upstream blood pressure increases
- vasodilation widens the arteries and blood pressure decreases
- this allows regional regulation of blood flow
Lymphatic System
- approx. 85% of fluid leaving capillaries re-enters due to osmotic pressure
- remaining fluid is returned to blood via lymphatic system
- plays important role in body’s defence mechanism
Blood Composition
- 55% plasma
- 45% red blood cells (packed cell volume = haematocrit)
- buffycoat = platelets & white blood cells
Plasma Composition
Function - solvent for carrying substances
Plasma proteins
- albumin: osmotic balance and pH buffering
- fibrinogen: clotting
- immunoglobulins: antibodies and defence
Respiration on a Cellular Level
- occurs via passive diffusion and needs a concentration gradient
- need thin cells with large surface area so molecules do not have to travel far
- respiratory surface must be moist so gas can dissolve and diffuse into cells
Gills
- water sucked in through mouth and pumped to gills
- opposite to flow of circulation in gills
- this is very efficient –> countercurrent exchange system
- ppO2 in water always higher than in blood meaning O2 constantly diffuses into blood
Tracheal Systems in Insects
- air travels through trachea into smaller and smaller airways
- air transported directly to tissues
- dry environment = difficult to maintain moisture
Mammalian Respiratory System
Nasal cavity:
- takes in air
- heats and moisturises
Trachea:
- windpipes
- passage of air
Bonchus
- separates into left and right lungs
Alveoli:
- where gas exchange occurs
- huge surface area
Double circulation is very efficient:
Lungs = low pressure
Blood vessels = high pressure
Negative Pressure Breathing
Inhalation;
- diaphragm contracts
- rib cage expands as rib muscles contract
- negative pressure compared to atmosphere
Exhalation:
- rib cage gets smaller as rib muscles relax
- diaphragm relaxes
- positive pressure compared to atmosphere –> air moves out
Pleural Sac
- forms double membrane surrounding the lung
- “fluid filled balloon surrounding an air filled balloon”
- pleural fluid has very small volume
- protects fragile lung tissue
- lungs constantly expanding
elastic recoil of chest wall tries to pull chest wall outward
Elastic recoil of lung creates inward pull
Regulation of Breathing
Homeostasis: blood pH~ 7.4
—>
Stimulus: rising levels of CO2 in tissues lowers blood pH
—>
Sensors in major blood vessels detect decrease in blood pH. Medulla detects decrease in pH of cerebrospinal fluis
—>
Sensor Centre: medulla receives from major blood vessels
—>
Response: Signals from medulla to rib muscles and diaphragm increase rate and depth of ventilation. CO2 level decreases and pH is restored to normal
—>
Homeostasis: blood pH~ 7.4
Mechanisms for Transport of Large Amounts of CO2 and O2
- gasses diffuse down pressure gradients
- Fick’s law of diffusion
- depends on differences in pp of gasses
- respiratory pigments transport gasses in blood
- overcome the low solubility of gasses in blood
- Haemocyanin: arthropods, molluscs
- Haemoglobin: invertebrates and vertebrates
- Increases from 4.5mL dissolved O2 per litre of blood to 200mL/L
O2 Use During Intense Exercise
2L of O2 per minute
Partial Pressures in Circulation
INHALED AIR pO2 = 160mmHg pCO2 = 0.2mmHg ---> ALVEOLAR SPACES pO2 = 104mmHg pCO2 = 40mmHg ---> PULMONARY VEINS / SYSTEMATIC ARTERIES pO2 = 104mmHg pCO2 = 40mmHg ---> BODY TISSUES supplying O2 and taking CO2 from cellular processes pO2 < 40mmHg pCOS > 45mmHg ---> SYSTEMATIC VEINS / PULMONARY ARTIERIES pO2 = 40mmHg pCO2 = 45mmHg
EXHALED AIR
pO2 = 120mmHg
pCO2 = 27mmHg
Haemoglobin
- consists of 4 polypeptide chains per molecule
- each chain contain a heme group which has an Fe2+ ion
- O2 binds to heme group
- 4 oxygen molecules per haemoglobin
positive cooperativity:
one heme group bonds to O2, strucutre of haemoglobin changes to make it easier for another O2 to bind
draw boar shift diagram
blood more acidic during exercise –> curve moves to right
Diving Mammals
Store large amounts of O2
- large volume of blood
- huge spleen which can store 24L of blood
- high concentration of myoglobin (binds to O2) in muscles
Adaptations to conserve O2 during a dive
- decrease heart rate
- decrease blood supply to muscles
Short term response to environmental and natural selection
Blood Clotting
- platelets release chemicals and stick together, forming a platelete plug
- initiates clotting cascade
- results in active thrombin which activates fibrin
- forms fibrin clot
O2 Delivery To An Athletes Muscles During A Race
- increased cardiac output —> increased blood flow to muscle
- increased cellular respiration uses O2
- pO2 in tissue capillaries drops to < 40mmHg
- decrease O2 saturation of haemoglobin
- increase O2 release into tissues
Tidal Volume
normal volume of air displaced between inhalation and exhalation
normal tidal volume is ~ 500mL
Vital Capacity
greatest volume of air that can be expelled after taking the deepest possible breath
Residual Volume
volume of air still remaining in lungs after exhaling as much air as possible
