B8 - Transport in animals Flashcards
1
Q
Why do animals need specialised transport systems?
A
- high metabolic demands (require lots of oxygen/produce lots of waste products)
- small SA:V ratio (SA available for absorption/removal decreases)
- larger size (increase in diffusion distance, which decreases rate of diffusion/its efficiency)
2
Q
What are the features of a circulatory system?
A
- liquid as a transport medium that circulates around the system
- blood vessels that carry the transport medium
- pumping mechanism that moves the fluid around the system
3
Q
What are the different types of circulatory systems?
A
- single (closed):
- blood flows through the heart and is pumped out to travel around the body, then returns to the heart
- (blood passes through two sets of capillaries)
- double (closed):
- blood travels through the heart twice for each circuit of the body
- (each circuit passes through one capillary network)
- open:
- very few vessels that contain the transport medium
- it comes into direct contact with the tissues/cells
- closed:
- blood is enclosed in blood vessels and does not come into direct contact with cells
- the blood is pumped around under pressure
4
Q
What is the open circulatory system? (insects)
A
- very few vessels to contain the transport medium
- pumped straight from the heart to the body cavity
- open body cavity = haemocoel
- transport medium is under low pressure
- comes into direct contact with the tissues and cells
- where exchange takes place between the transport medium and cells
- where exchange takes place between the transport medium and cells
- found in insects and other invertebrates
- insect blood = haemolymph
- does not carry CO2 or O2 (transports food/nitrogenous waste/cells involved in disease defence)
- membrane splits body cavity
- heart extends along thorax and abdomen
- ** steep diffusion cannot be maintained and amount of haemolymph cannot be varied **
5
Q
What is the closed circulatory system?
A
- blood is pumped and enclosed within blood vessels
6
Q
What is the single closed circulatory system?
A
- blood passes through the heart once in each complete circulation, and is transported within blood vessels
7
Q
What is the double closed circulatory system?
A
- blood is pumped through the heart twice for each circuit of the body
- blood is enclosed within blood vessels
8
Q
What are some components of blood vessels?
A
- elastic fibres:
- composed of elastin
- allows vessel to stretch and recoil (flexibility)
- smooth muscle:
- contracts/relaxes
- changes the size of the lumen
- collagen:
- provides structural support
- maintains shape/volume of vessel
9
Q
What are arteries?
A
- carry blood away from the heart to the body tissues
- carries oxygenated blood
- except the pulmonary/umbilical artery (carry deoxygenated blood from heart to lungs)
- blood is under higher pressure
10
Q
What are artery walls made of?
A
- elastic fibres (inner layer):
- helps to withstand the force of blood pumped away from heart
- allows them to stretch and increase blood volume
- they recoil and return to original size (evens out surges of blood)
- generates blood pressure with the stretching and recoiling
- smooth muscle (middle layer)
- collagen (outer layer):
- provides strength to withstand the high pressure
- endothelium - smooth layer which allows blood to easily flow over it
11
Q
What is the structure of arteries?
A
- small lumen to maintain high pressure as the blood is transported around the body
12
Q
What are arterioles?
A
- they are vessels that link the arteries and the capillaries
13
Q
What are arterioles made of?
A
-
less elastin:
- they have little pulse surge (do not need to eliminate)
-
more smooth muscle:
- allows the walls to constrict/dilate to control flow of blood into certain organs
14
Q
What is vasoconstriction?
A
- when the smooth muscle of the arteriole wall constricts and prevents the flow of blood into a capillary bed
15
Q
What is vasodilation?
A
- when the smooth muscle of the arteriole wall relaxes and allows blood to flow into the capillary bed
16
Q
What are capillaries?
A
- they are microscopic vessels that link the arterioles with the venules
- form an extensive network through all the tissues of the body
17
Q
What is the structure of capillaries?
A
- small lumen:
- red blood cells have to travel in single file
- large enough gaps between endothelial cells (wall):
- where substances pass out into the fluid
- ** except the capillaries in the central nervous system (tight junctions) **
18
Q
How are capillaries adapted to their function?
A
- thin wall (one cell thick):
- allows for short diffusion distance
- substances can be exchanged through the capillary walls between the tissue cells/blood
- large SA:
- helps for efficient diffusion of substances into and out of the blood
- greater cross-sectional area:
- rate of blood flow falls
- the relatively slow movement allows for enough time for exchange of substances
19
Q
What are veins?
A
- they are blood vessels that carry blood away from the cells towards the heart
- carry deoxygenated blood
- except pulmonary vein (oxygenated) and umbilical vein (during pregnancy) carries ox. blood from placenta to foetus
20
Q
What are vein walls made of?
A
- lots of collagen
- relatively less elastic fibre (pulse is absent)
- they do not need to withstand a high blood pressure
21
Q
What is the structure of veins?
A
- larger lumen
- valves in medium-sized veins to prevent backflow
- thin lining (endothelium) allowing for easy blood flow
22
Q
What are venules?
A
- they are blood vessels that link capillaries with veins
23
Q
What are venules made of?
A
- very thin walls
- little smooth muscle
24
Q
How does the body overcome low pressure/gravity?
A
- veins have one-way valves:
- close when blood flows backwards
- bigger veins run through active muscles:
- when muscles are active they squeeze the veins, forcing blood towards the heart
- valves prevent backflow when muscles relax
- breathing movements act as pump:
- pressure changes and squeezing actions move blood in chest veins towards the heart
25
What does blood consist of?
- *plasma*: 55%
- carries dissolved glucose, amino acids, mineral ions, hormones
- large plasma proteins (albumin, *fibrinogen*, *globulins*)
- also transports rbcs and wbcs
- carries *platelets* (fragments of large cells found in red bone marrow)
26
What are the functions of blood?
- transport of:
- O2 to/CO2 from respiring cells
- digested food from small intestine
- *nitrogenous waste* products from cells
- chemical messages (*hormones*)
- food molecules from storage compounds
- platelets to *damaged areas*
- cells/antibodies (*immune response*)
- maintains steady body temp.
- acts as *buffer*, minimises pH changes
27
What is tissue fluid?
- the fluid that fills the spaces between cells
- has the same composition as plasma with no *plasma proteins* and *rbcs*
28
What is oncotic pressure?
- the tendency of water to move into the blood by osmosis (-3.3 kPa)
29
What is hydrostatic pressure?
- the pressure exerted by blood in an enclosed system (blood vessels)
30
How is tissue fluid formed?
- since plasma proteins cannot pass through capillary walls, they give the blood a *low water potential*
- this causes water to move into the blood in capillaries (from arterioles)
- arterial end:
- hydrostatic pressure = 4.6 kPa
- higher than onc. pressure, so fluid is squeezed out (tissue fluid)
- venous end:
- hydrostatic pressure = 2.3 kPa
- lower than onc. pressure
- water moves back into capillaries
- 90% of the tissue fluid is back into blood vessels
31
What is lymph?
- 10% of the liquid that leaves the blood vessels and drains into *lymph capillaries*
- similar in composition to plasma/tissue fluid but has less *oxygen*/*nutrients*
- contains fatty acids
32
What are lymph vessels?
- joined up lymph capillaries which transport the. lymph
- contain one-way valves to prevent backflow
- ** lymph returns to blood (into the clavicle veins) **
33
What are lymph nodes?
- small glands that can contain lymphocytes that produce antibodies
- they intercept bacteria (ingested by phagocytes)
- enlarged lymph nodes are a sign that the body is fighting off an invading pathogen
34
How is oxygen transported?
- erythrocytes contain *haemoglobin* which carry O2
- haemoglobin is a large globular conjugated protein
- O2 binds loosely to haemoglobin forming *oxyhaemoglobin* (reversible)
- steep conc. gradient between lungs (high O2) and erythrocytes (low O2)
- O2 moves in and binds with haemoglobin
- since free O2 levels are low, steep conc. gradient is maintained
35
What is the oxygen dissociation curve?
- percentage saturation haemoglobin plotted against partial pressure of oxygen
- high partial pressure = haemoglobin is rapidly loaded with O2
36
What is the Bohr effect?
- as partial pressure of CO2 rises, haemoglobin gives up oxygen more easily
- active tissue = haemoglobin gives up O2 more easily
37
What is fetal haemoglobin?
- higher affinity for O2 than adult haemoglobin as they will jot receive enough O2
38
How is carbon dioxide transported?
- react slowly with water to form carbonic acid
- this then dissociates and forms H ions and hydrogen carbonate ions
- carbonic anhydrase catalyses this reaction
39
What is chloride shift?
- when the negatively charged hydrogen carbonate ions move out of the erythrocytes into the plasma, chloride ins move into the cells
- this maintains the electrical balance of the cell
40
What does the heart consist of ?
- it is made of a cardiac muscle
- four chambers and two pumps
- deoxygenated = right
- oxygenated = left
- *coronary arteries* supply muscle with blood
41
What is the external structure of the heart?
- ** clockwise **
- aorta (aortic arch)
- pulmonary artery
- pulmonary vein
- left atrium
- left ventricle
- (descending aorta)
- inferior vena cava
- right ventricle
- right atrium
- superior vena cava
42
What is the internal structure of the heart?
- pulmonary veins
- left atrium
- bicuspid valve (left atrioventricular/*tendinous cords*)
- left ventricle (thick muscular wall)
- semilunar valves
- aorta
- vena cava
- right atrium
- tricuspid valve (right atrioventricular/*tendinous cords*)
- right ventricle
- semilunar valves
- left pulmonary artery
43
What is the movement of deoxygenated blood through the heart?
- enters the *right atrium* from the *vena cava* (inferior = lower body, superior = upper body) at a low pressure
- pressure builds as blood flows in
- *tricuspid valve* opens to allow blood to flow into the *right ventricle*
- the valve then closes to prevent backflow
- right ventricle contracts and pumps the blood through the *semilunar valves*
- the blood is sent through the *pulmonary artery*
- this transports it to the *capillary beds* of the lungs
44
What is the movement of oxygenated blood through the heart?
- enters the *left atrium* from the *pulmonary vein*
- as pressure builds, *bicuspid valve* opens and allows blood to enter the *left ventricle*
- valve closes to prevent backflow
- left ventricle then contracts and pumps the blood through the *semilunar valves*
- it then enters the *aorta* and is pumped around the body
45
Why is the muscular wall of the left side much thicker than the right?
- the lungs are relatively close to the heart and are much smaller than the rest of the body
- so the right ventricle pumps the blood a relatively short distance
- it only has to overcome the resistance of *pulmonary circulation*
- the left ventricle has to overcome the resistance of the aorta and the arterial systems of the *whole body*
- blood must also be pumped under pressure to all areas of the body
46
What is the septum?
- inner dividing wall of the heart
- prevents the mixing of deoxygenated and oxygenated blood
- allows for efficient supply of oxygen around the body
47
What is the cardiac cycle?
- the events that take place in a single heartbeat
- this lasts about 0.8 seconds in an adult
48
What is diastole?
- the heart relaxes
- atria then the ventricles fill with blood
- volume and pressure of blood in the heart build as the heart fills
- pressure in the arteries is at a minimum
49
What is systole?
- when the atria contract (atrial systole) and then the ventricles contract (ventricular)
- increases the pressure inside the heart
- this forces out the blood from the right (lungs) and the left (body)
- volume and pressure of blood in heart are low at the end of systole
- pressure in the arteries are at a maximum
50
What is the cardiac output equation?
- cardiac output = heart rate x stroke volume
51
What happens to aortic pressure?
- rises when the ventricles contract
- then gradually falls (never falls below 12kPa due to its elasticity)
- recoil produces a slight rise in pressure at the start of the relaxation phase
52
What happens to atrial pressure?
- always relatively low due to thin walls (less force)
- highest when contracting
- pressure builds when atria fill with blood until atro-ventricular valve opens
53
What happens to ventricular pressure?
- low at first, gradually increases when ventricles fill with blood
- atrioventricular valves close and pressure rises (thick walls contract)
- as pressure rises above the aorta's, blood is forced into it
- pressure falls as ventricles empty
54
What happens to ventricular volume?
- rises as the atria contract and ventricles fill with blood
- drops suddenly as blood is forced out into aorta
55
What is the lub-dub sound?
- lub = blood forced against the *atrio-ventricular* valves (closes) as ventricles contract
- dub = blood closes the *semilunar* valves as ventricles relax
56
Why is the cardiac muscle myogenic?
- it is able to initiate its own contractions without the need for nervous stimulation
- the average resting heart rate of an adult is around 70 bpm
57
How is heart action initiated and coordinated?
- the *sino-atrial node* (SAN) initiates the electrical activity in the atria
- causes them to contract, starts the heartbeat
- it is picked up by the *atrio-ventricular node* (AVN) which causes a slight delay
- the electrical wave then stimulates the *bundle of His* (consisting of Purkyne fibres)
- they go through the septum
- the bundle of His splits into two branches and sends a wave of excitation down to the *apex*
- at the apex, the Purkyne fibres spread through the ventricle walls
- this triggers the contraction of the ventricles
58
What is an ECG?
- electrocardiogram
- measures the electrical differences in the *skin* which result from the *heart's* electrical activity
- they can be used to help diagnose heart problems (treated correctly/fast)
59
What is tachycardia?
- very rapid heartbeat (over 100 bpm at rest)
- abnormal if caused by problems in electrical control of the heart
- treated by medication/surgery
60
What is bradycardia?
- slow heartbeat (below 60 bpm)
- fitness/training can cause this as heart beats more slowly and efficiently
- severe cases require an artificial pacemaker
61
What is ectopic heartbeat?
- extra heartbeats that are out of the normal rhythm
- mostly have it at least once a day
- can be serious if it is very frequent
62
What is atrial fibrillation?
- example of arrhythmia (abnormal rhythm of the heart)
- rapid electrical impulses are initiated in the atria
- fibrillate up to 400 times a min
- but it does not allow for proper contractions
- heart does not pump blood around very effectively
