Circulation! Flashcards
How do exchanges occur at the cellular level?
By crossing the plasma membrane
How do exchanges occur in unicellular organisms?
Directly with the environment via diffusion
What is Fick’s law?
The rate of diffusion is proportional to (surface area x concentration difference) divided by the thickness of membrane.
What are the three components of a circulatory system?
Circulatory fluid, interconnecting vessels and a muscular pump.
What is the fluid circulated in an open circulatory system?
Haemolymph
Briefly describe how an open circulatory system works
The heart contracts, pushing the interstitial fluid (haemolymph) into sinuses surrounding the organs. Gas exchange then occurs with the cells. Relaxation of the heart as well as periodic body contractions help to draw blood back to the heart for contraction.
In a closed circulatory system what liquid is confined to vessels and which surrounds cells?
Blood is confined to vessels and the interstitial fluid bathes the cells.
What are the three main types of blood vessels?
Arteries, Veins and capillaries
What do arteries branch into to? What vessels feed into veins?
Arteries branch into arterioles and venules converge into veins
How are arteries and veins distinguished?
By the direction of blood
What chambers of the heart do organisms with a single circulation have?
One atrium and one ventricle
Describe the circulation series of a single circulatory system
Deoxygenated blood is pumped from the heart to the gill capillaries to become oxygenated. This blood then flows to the body capillaries to supply oxygen to the body/organs. The now deoxygenated blood flows back to the heart.
Which type of closed circulatory system maintains a higher blood pressure for the organism?
Double
Why do single circulatory organisms have a relatively low metabolic rate?
They are ectothermic - they rely on environmental heat sources to regulate their body temp
Describe the chambers in an amphibian heart
Two atria and one ventricle
What circuit does oxygen-poor blood flow through in an amphibian?
A pulmocutaneous circuit
What happens to an amphibians circulatory system when they go underwater?
Blood flow to the lungs is severely reduced and respiration occurs through the skin.
Describe the chambers of a reptilian heart
Two atria and one ventricle. The ventricle is partially divided by an incomplete septum.
How do crocodilians’ hearts differ from other reptiles?
They have a 2 ventricles, fully divided by a septum.
Which sides of the mammalian heart deal with oxygenated and deoxygenated blood?
Left side = oxygen-rich blood. Right = oxygen-poor blood
What are the two loops of vessels known as in mammalian hearts?
The pulmonary circulation and the systemic circulation.
What is the function of the atria?
They serve as collection chambers for blood returning to the heart.
In terms of thickness of the cardiac tissue, describe the relative thickness of the atria and the ventricles
The atria are relatively thin and the ventricles are much thicker with more muscle. The left ventricle has the most muscle.
Define the cardiac cycle
The heart rhythmically contracting and relaxing in a cycle.
What is the name for the contraction phase of the cardiac cycle?
Systole
What is the name of the relaxation phase in the cardiac cycle?
Diastole
Describe the blood that passes through the left atrium
Receives oxygenated blood from the lungs via the pulmonary veins.
Describe the blood that passes through the left ventricle
Receives oxygenated blood from the left atrium and pumps it to the body via the Aorta
Describe the blood that passes through the right atrium
Receives deoxygenated blood from the body via the Vena Cava
Describe the blood that passes through the right ventricle
Receives deoxygenated blood from the right atrium and pumps it to the lungs via the pulmonary artery.
Name the four valves in the heart
The pulmonary valve, the Tricuspid valve, the mitral valve and the aortic valve.
What is the function of the heart valves?
Ensures blood flows in the correct direction
What causes the “lub” and the “dub” sounds heard on a stethoscope?
Lub = the closing of the atrioventricular valves. Dub = the closure of the semilunar valves.
What causes heart murmurs to be heard?
The backflow of blood through a defective valve.
In vertebrates, where does the heartbeat originate?
In the heart itself
Describe autorhythmic cells
They contract and relax repeatedly without any signal from the nervous system
Describe the four stages of the heart conduction system
SA node sends an electrical signal which spreads through the atria causing atrial systole. The signals have a small delay at the AV node. The AV node then sends an electrical signal down to the heart apex. This signal then spreads upwards throughout the ventricles causing ventricular contraction.
why is the AV node considered a “relay point”?
It delays the electrical signal after atrial systole to ensure the atria can fully close before the ventricles contract.
Name three different physiological ways to control the heart beat
Temperature, hormones and nerve impulses.
Where do the sympathetic nerves originate from?
The T1-T4 levels of the spinal cord
What effects do the sympathetic nerves have on the heart? What parts of the heart do they effect? What do they release?
They increase heart rate and the force of contraction. The sympathetic nerves act on the entire heart. They release norepinephrine.
What effects do the parasympathetic nerves have on the heart? What parts of the heart do they effect? What do they release?
They decrease heart rate and reduce the force of contraction. They act mostly on the SA node. They release acetylcholine.
Where do the parasympathetic nerves originate from?
The Vagus Nerves
What is the cardiac output?
The volume of blood pumped into the systemic circulation per minute
Define the heart rate
Beats per minute
Define stroke volume
Amount of blood pumped in a single ventricular contraction
How is blood pressure determined?
By the cardiac output and peripheral resistance met by blood as it passes from the arteries into the capillaries.
Name a function of the epithelium being smooth
It reduces resistance
What are the functions of arteries?
To transport blood from the heart to the capillaries. To act as a pressure reservoir for forcing blood into smaller vessels. To dampen oscillations (ensure a more even blood flow).
What are the functions of Veins?
To transport blood from capillaries back to the heart. To act as a storage reservoir for blood.
How is blood returned via veins even though the pressure is low?
One-way valves prevent backflow of blood and skeletal muscle contractions help move blood against gravity.
What is atherosclerosis? What can this lead to?
The deposition of plaques in arterial walls. Can lead to a myocardial infarction (heart attack)
What is Deep Vein Thrombosis? What is a possible cause of this?
Pooling of blood in deep veins leads to the formation of a clot. Can be caused by prolonged inactivity.
How can we calculate pulse pressure?
Systolic pressure - diastolic pressure
In which blood vessel is blood flow velocity the slowest? Why?
Capillary beds due to a high resistance and a large total cross-sectional area.
Define systolic pressure
the pressure in the arteries during ventricular systole
Define a pulse
The rhythmic bulging of artery walls with each heartbeat.
Define diastolic pressure
the pressure in the arteries during diastole
What mechanisms regulate blood pressure? How do they do this?
Homeostatic mechanisms regulate blood pressure by altering the diameter or the vessels. i.e. vasoconstriction and vasodilatation.
How does passive transport occur in capillaries?
Through thin capillary endothelial cell walls - no energy required.
How does active transport occur in capillaries?
By bulk flow through intercellular spaces between endothelial cells (can be described as a sieve-like mechanism)
What kind of junctions appear frequently in the brain capillaries? why are they needed?
Tight junctions - they close the intracellular spaces which forms the blood-brain barrier.
What creates the osmotic pressure in capillaries?
Blood proteins - this pulls fluid back into the capillaries
What drives fluid out of the capillaries?
Blood pressure - this gets less towards the venule side of the capillary bed.
True or false: On average there is a net gain of fluid from the capillaries.
False - on average there is a net loss of fluid from the capillaries
What is the fluid lost by capillaries known as?
Lymph
What is the function of the lymphatic system in relation to capillaries?
To return the fluid that leaks out from the capillaries back to the venule side of the capillary bed.
What is an oedema?
Swelling caused by disruptions in the flow of lymph
What two physical defence mechanisms does the pharynx have to clean the respiratory system?
Cilia and mucas
What are the two layers of the pleural membrane?
The visceral and parietal
What is the pleural cavity?
The potential space between the layers of the pleural membrane which contains pleural fluid
What are the functions of pleural fluid?
They prevent friction and cause the layers of the pleural membrane to adhere (stick) to one another i.e. causing surface tension
What three factors does diffusion rate depend on in the alveoli?
Surface area, distance and concentration difference
What is the purpose of Surfactant?
It lines the alveolus and reduces surface tension and allows alveolar expansion during inhalation.
Describe inhalation in terms of the lungs, direction of air flow, the diaphragm and the pressure of breathing
The lungs expand to fill the enlarged thoracic cavity. Air is drawn into the lungs and the diaphragm is pulled downwards. This is negative pressure breathing.
Describe what happens during exhalation in terms of the rib muscles, the diaphragm, the elasticity of the lungs, and the direction of air
The rib muscles relax and the diaphragm relax, and the elasticity of the lungs drives the air out of them.
What makes up haemoglobin?
Four protein subunits consisting of a polypeptide chain and a haem group. This haem group contains iron atoms which allows oxygen to bind to it.
Describe briefly how venous blood becomes saturated with oxygen. Use the oxygen partial pressure.
At the alveoli, the Partial oxygen pressure is roughly 100mmHg which then diffuses across the capillary membrane into the venule side of the capillary bed. This oxygen then binds to the available haemoglobin molecules. This allows the partial oxygen pressure in the blood to rise from 40 to 95mmHg
When would you see a persons haemoglobin least saturated?
During strenuous exercise as the haemoglobin has unloaded its oxygen to be used in the tissue
Describe the co-operativity of the haem groups in haemoglobin
The subunits of haem work together in terms of their affinity for oxygen i.e. when one loads/unloads their oxygen molecule, the other subunits are more readily able to do the same.
In what three ways is carbon dioxide transported out of the cells?
5% as dissolved CO2, 5% is attached to haemoglobin and other blood compounds, 90% as bicarbonate ions (carbonic acid is catalysed within red blood cells to form the bicarbonate)
