42 Circulation and Gas Exchange Flashcards
What structural adaptation do axolotyls have?
They have external gills that are feathered to maximise surface area and thus gas exchange.
What are axolotyls classed as?
Salamanders
How does time taken to diffuse relate to distance and what is the implication of this?
The taken is proportional to the square of the distance.
Thus as body size gets larger diffusion is slower, resulting in the need for more sophisticated circulatory systems.
What are the basic adaptations to the fact that diffusion is slower over long distances?
Either have a body plan where all the cells are near the environment i.e. cnidarians and flatworm gastrovascular cavities.
Alternately large organisms can overcome this with circulatory systems where the products are bought close to the cell.
What animals have gastrovascular cavity?
Cnidarians like jellyfish, hydras and flatworms.
Describe the gastrovascular cavity of jellyfish?
There is a “central canal” that has many “radial canals” branching from it
Describe the gastrovascular cavity of flatworms?
It is highly branched.
What are the basic forms of circulatory system?
Open circulatory systems and close circulatory systems.
What are open circulatory systems?
Systems in which the circulatory fluid, known as “hemolymph” can leave the vessels through pores and thus is the interstitial fluid between cells.
The hemolymph is then collected by the heart and re circulated.
What is an example of an animal that uses an open circulatory system?
Grasshoppers.
How does the heart pump the hemolymph?
As in other animals by contraction.
As the emptied heart expands it creates a vacuum and thus sucks in some hemolymph.
What is an open circulatory system typical of?
Most, but not all, invertebrates use it.
Describe the heart of a grasshopper.
It is a long tube, known as the “sinuses”, that extend down the grasshopper’s “back” and has pores to allow hemolymph to enter and exit.
What are the advantages of and open circulatory system?
It operates under a lower pressure and thus requires less energy.
What can open circulatory systems be used besides transport?
Spiders use the hydrostatic pressure of the hemolymph to move their legs.
Where does hemolymph get released into the body?
In many organism this occurs at the heart.
However some larger animals like lobsters and crabs still use open circulatory systems but have vessels that carry the hemolymph part of the way.
What is a close circulatory system?
A circulatory system in which the circulating fluid does not leave the vessels and instead only nutrients can leave through diffusion.
What are the advantages of an open circulatory system?
It avoids mixing oxygenated and deoxygenated fluid as it is directional.
It also allows the control of blood flow to specific organs and regions.
What animals have closed circulatory systems?
All vertebrates as well as annelids and cephalopods.
What are annelids?
A phylum of invertebrate animals that includes earthworms and leeches.
What are cephalopods?
A phylum of invertebrate animals that includes squids and octopuses.
What is the closed circulatory system often called?
The cardiovascular system.
How are capillaries arranged?
In networks called capillary beds” that ensure they provide all cels with nutrients.
In order, what are the vessel types blood passes through as it leaves the heart?
Artery, Arterioles, Capillaries, Venules, Vein
What are arterioles and venules?
Small arteries/veins respectively that carry blood to and from the capillaries.
What can vertebrate circulation be divided into?
Single circulation and double circulation.
In what animals does single circulation occur?
Bony fishes, rays and sharks
In what animals does double circulation occur?
All other vertebrates i.e. Amphibians, reptiles, birds and mammals.
What is single circulation?
A form of circulation in which there is a single circuit of blood flow that passes through two capillary beds: one in the lungs and one in the body
How does single circulation affect blood flow?
It significantly decreases pressure after the first gill capillary beds and thus limits the rate of blood flow in the rest of the body.
What is the structure of the heart of an animal that uses single circulation?
It has two chambers (one ventricle and one atrium.)
How is the slow movement of blood mitigated in animals that use single circulation?
The contraction of muscles during swimming leads to some increase in blood pressure.
What is double circulation?
The form of circulation in which blood that leaves the heart passes through the lung capillaries then returns to the heart where it is pumped through the body.
What are the circuits of double circulation named?
The circuit through the body i shamed the ‘systemic circuit’.
The other circuit is named the ‘pulmonary circuit’ if it passes exclusively through the lungs or the ‘pulmocutaneous’ is is passes through the skin and lungs.
What groups of animals have distinct double circulatory systems?
Amphibians, Reptiles and Mammals/Birds
Describe the circulatory system of Amphibians?
They have 3 chambered hearts with 2 atria and one ventricle. The ventricle is not separated by a septum but it does have a ridge that stops 90% of the blood from mixing.
They have two circuits: the pulmocutaneous and the systemic circuit.
Why do amphibians have a pulmocutaneous circuit as opposed to just a pulmonary circuit?
The capillaries passing through the skin are the sole site of gas exchange when the frog etc. is submerged.
Describe the circulatory system of reptiles?
Most i.e. snakes, turtles and lizards have a 3 chambered heart separated by an incomplete septum. In crocodilians like alligators and caimans this septum is complete leading to 4 chambers.
They have system and pulmonary circuits. They have two aortas. The left systemic aorta carries oxygenated blood to the systemic capillaries while the right systemic aorta carries blood that is mixed due to the incomplete septum to the system circuit.
Crocodilians with 4 chambered hearts still have right aortas but they carry oxygenated blood.
What circulatory adaption do crocodilians have besides a complete septum?
The right systemic aorta takes blood from both the left and right ventricle. Therefore when the crocodile dives and circulation to the lung is frivolous. The “foramen of panizza’ can constrict the pulmonary vein so that blood of the right ventricle destined for the lungs can be re-routed to the systemic circuit, giving it more blood for its underwater activities.
Which type of animal has a circulatory system most like a mammal?
Birds
From what side does blood enter the heart and from what side does it leave? How does this differ among double circulating animals?
In all double circulating vertebrates blood enters through in the right side of the heart (drawn on left) and exits through the left side (drawn on right)
Describe the path blood takes from when it enters the heart to when it leaves?
Right atrium - right ventricle - pulmonary artery - alveolar capillaries - pulmonary vein - left ATRIUM then left VENTRICLE - aorta.
How many are there of each vessel entering and exiting the heart?
There are two vena cava : the inferior vena cava and the superior vena cava. Similarly two pulmonary veins enter the left atrium, with one from each lung.
There is one one each of aorta and pulmonary artery although both branch off after they leave the heart.
Where is the heart located?
Behind the sternum (breast bone)
Which ventricle is under the greatest pressure? How much more blood does it pump?
The left ventricle is under the greatest pressure as it has to pump blood around the entire body. It therefore has the thickest walls.
However because the human circulatory system is a closed system they both pump the same amount of blood per stroke.
How many stages is the cardiac cycle divided into?
3
What is stage 1 of the cardiac cycle?
Atrial and ventricular diastole.
What is stage 2 of the cardiac cycle?
Atrial systole and ventricular diastole
What is stage 3 of the cardiac cycle?
Ventricular systole and atrial diastole
What happens during Atrial and ventricular diastole?
Blood flows into the atria and can also moves through the atria into the ventricle.
What happens during Atrial systole and ventricular diastole?
Blood flow into the atria shuts off as the atrium constricts to force blood into the ventricle.
What happens during Ventricular systole and atrial diastole?
The valves between the atria and ventricle closes. The ventricle then constricts forcing blood out of the aorta/pulmonary artery.
How long does the Atrial and ventricular diastole stage of the cardiac cycle take?
0.4 seconds
How long does the Atrial systole and ventricular diastole stage of the cardiac cycle take?
0.1 seconds
How long does the Ventricular systole and atrial diastole stage of the cardiac cycle take?
0.3 seconds
What does diastole refer to?
The phase of the heartbeat (or particular area) where the heart is relaxed.
What does systole refer to?
The phase of the heartbeat (or particular area) where the heart is contracted.
What is the sum of blood exiting the heart called?
Cardiac output.
How is cardiac output calculated?
It is heart rate (beats per minute) multiplied by stroke volume (amount of blood pumped per contraction)
What is a typical BPM?
72 beats per minute
What is a typical cardiac output?
5L per minute
What is typical stroke volume?
Around 70 mL
What are the valves of the heart?
The atrioventricular valves (AV) are between the atria and their ventricles. The semi-lunar valves are at the exits of the heart (pulmonary artery and aorta)
How are heart valves regulated?
Entirely passively based on the pressure of the blood.
The atrioventricular valves are closed by the high pressure of the contracting ventricles and thus prevent blood form back flowing into the atria.
The semilunar valves are pushed open by the pressure of the contracting ventricles so that blood can leave. However as the contraction stops they close themselves to prevent back flow.
What causes a ‘heart murmur’ and what is it?
An unusual sound caused by a defective valve
What can lead to heart murmurs?
Damage to the valves i.e. through rheumatic fever.
How can heart activity be detected?
An electrocardiagram (EKG from german name) consist of sensors placed on the skin that detect the electrical signals of the heart to diagnose heart attacks etc.
Where are the electrical signals that control a heart beat regulated?
In vertebrates it is in the heart. Some arthropods have it in the nervous system.
What are the regions of a vertebrate heart involved in regulating the heart?
The sinoatrial (SA) node and the atrioventricular (AV) node
What are the steps of heart beat regulation?
Signals generated by the SA node spread through the atria.
These signals reach the AV nodes which delay them for around 0.1 seconds to give the atria time to fill with blood.
The AV nodes then pass on the signals which travels along special muscle fibres called “bundle branches” which carry the signal to the ‘apex’ (bottom) of the heart.
From the apex of the heart the signals travel along another specialised form of muscle fibre: Purkinje fibres. These fibres cary the signal from the bottom of the heart to the top, causing contractions as they travel up the heart.
What is the significance of heart signals being carried to the apex of the heart then travelling back up again?
This ensure contractions start at the bottom so blood is forced up and out of the aorta/pulmonary artery
What is the primary system regulating heart beat?
The sympathetic and parasympathetic divisions of the nervous system?
How does body temperature affect heart rate?
As body temperature increases by 1ºC heart rate increases by 10 bpm.
This explains why heart rate is accelerated during a fever.
What do all blood vessels contain?
A core of endothelium tissue
What is the structure of a capillary?
It has a one cell thick layer of simple squamous epithelium tissue and the associated “basal lamina” of ECM on the outside.
From inside to outside, what is the structure of an artery?
Endothelium, smooth muscle and elasticated connective tissue
From inside to outside, what is the structure of a vein?
Endothelium, smooth muscle and connective tissue
How do arteries and veins differ and what is the significance of this?
Veins have valves to prevent the back flow of blood under lower pressure.
Veins have thinner walls and thus larger lumens to facilitate carrying blood that is not under pressure.
Arteries have more elasticated connective fibres. This allows them to expand as the heart forces blood into them. As they recoil this provides a force that pushes blood along between heartbeats.
Why doesn’t blood speed up as it enters the capillaries?
Traditionally as a fluid enters smaller diameter tube it speeds up. Conversely blood slows down as it enter the capillary. This is due to the fact that the total cross section of all the capillaries is greater than the total cross section of the arteries so the blood slows down.
What is the advantage of blood flow slowing through the capillaries?
It allows more time form gas exchange and solute diffusion to occur between the capillaries and the surrounding cells.
(it also mitigates the high pressure that would otherwise damage capillaries)
What is blood pressure divided into?
Systolic and diastolic pressure
How do systolic and diastolic pressure differ?
Systolic is measured when the ventricles contract whereas diastolic is measures when the ventricles relax.
Why is diastolic pressure not 0?
The elastic walls of the arteries recoiling provides some pressure.
What is blood pressure typically measured in?
mmHg (millimetres of mercury)
What is “pulse”
They rhythmic bulging of the arteries (not to be confused with heart beat).
How can blood pressure vary?
Physical and emotional stress trigger the smooth muscles of the arteriole walls to constrict, known as vasoconstriction. This reduces cross section and thus blood pressure.
What happens when muscles need more blood and how does this affect blood pressure?
Arterioles leading to them undergo vasodilation so that more blood can flow to them.
As this increases surface area it this would be indicative of causing the blood flow to drop.
In reality the heart adjusts its cardiac outputs so blood pressure remains constant.
What is a typical blood pressure reading and how is it interpreted?
120/70 indicating 120 mmHg of systolic blood pressure and 70 mmHg of diastolic blood pressure
What is used to measure blood pressured?
A sphygmomanometer
How does a sphygmomanometer work?
A cuff is placed around the arm and inflates so that it cuts of arterial blood flow?
As the cuff slowly deflates a stethoscope is used to record the point at which blood can periodically pass through due to the pulse. As this point the pressure of the cuff is the systolic blood pressure.
The cuff continues to deflate until blood can flow freely. This indicates the diastolic blood pressure.
How is blood flow maintained through the veins?
As the skeletal muscles contract they push blood back to the heart. This is helped by veins that stop this blood flow flowing back own between contractions.
Why is physiologically important that athletes ‘cool down’ after exercise?
The skeletal muscles suddenly stop so less blood returns to there heart. The heart, however, continues pumping at the accelerated rate and thus blood pressure drops.
How can blood flow to capillaries be regulated?
Either the arterioles that lead to capillaries undergo vasodilation/vasoconstriction to adjust the blood flow.
Alternately there can be a an arteriole that leads straight from the artery to the vein (this is known as the thoroughfare channel) Smooth muscle sphincters named “precapillary sphincters” can dilate or contract to allow or prevent blood from flowing into the capillaries that branch off the thoroughfare channel.
How is the regulation of blood flow to the capillaries related to the response to an injury?
At the injury the chemical histamine is released to INCREASE blood flow to the wound site. This is beneficial as it provides greater access for platelets and white blood cells.
How do solutes leave the capillaries?
Mostly by diffusion but some leave by exocytosis.
To facilitate the diffusion of ions and polar macromolecules out of the capillaries many have pores to allow sugars, salts and urea to leave.
How is water loss from blood vessels regulated and what is the net direction?
The pores allow the bulk exiting of water and the removal of solutes leads to osmotic pressure to suck the water out of the capillaries. Despite this the proteins of the blood, which are too large to leave via the pores/endothelium, give some osmotic pressure to retain the blood.
The net effect of these factors however is a net loss of fluid.
Where is most water lost through blood vessels and why is this beneficial?
Through the arteries as they are under the highest pressure.
This is beneficial as it reduces the volume and thus pressure of the blood and thus aids in reducing the pressure by the time it reaches the capillaries.
How is water lost by the blood vessels returned?
As it exits it becomes interstitial fluid. It then diffuses into lymph vessels where the fluid is named as “as lymph”
What happens to lymph after it enters the lymph vessels?
It circulates based on the contractions of surrounding skeletal muscles. (lymph vessels have valves)
It passes through lymph vessels before being deposited into a major vein.
How can lymph vessels be blocked and what does this cause?
Parasitic worms can block the lymph vessels.
Blocked lymph vessels lead to pooling of vessel which leads to swelling named elephantiasis.
Where are lymph nodes concentrated?
Neck, armpits and groin.
What are blood components divided into? (what is the relative concentration)
Plasma (55%) and Cellular Elements (45%)
What are the basic constituents of plasma?
Water, Ions (“blood electrolytes”), “Plasma proteins” and Transported Substances
What is the function of water in the plasma?
Its a solvent for carrying other substances and also reduces the viscosity.
What are the “blood electrolytes” found in plasma?
Sodium, Potassium, Calcium, Magnesium, Chloride and Bicarbonate ions
What is the function of blood electrolytes in plasma?
They maintain osmotic balance (prevent excess water loss from blood vessels), act as pH buffers, and regulate membrane permeability.
