Circulatory System Flashcards
(130 cards)
1
Q
Whats the main function of the circulatory system?
A
Transport
2
Q
What does the circulatory system transport?
A
Nutrients and water.
Hormones -> cell-cell communication.
Respiratory gases.
Cells -> immunity and repair of injuries.
3
Q
What does the circulatory system consist of?
A
A series of tubes (blood vessels) filled with fluid (blood) and connected to a muscular pump (heart).
4
Q
What ensures continues blood flow through the body?
A
The heart.
5
Q
What does the circulatory system work integrated with?
A
The respiratory system to transport gases through tissues.
6
Q
What animals lack a circulatory system?
A
Sponges
Cnidaria
Nemotoda
7
Q
How do small aquatic invertebrate’s without circulatory systems exchange materials with their enviroment?
A
Diffusion.
8
Q
How does gravity affect the circulatory system?
A
In water blood is weightless and the heart only has to overcome fluid resistance.
On land blood pressure needs to be higher to push blood upwards through veins against gravity.
9
Q
How does body size affect the circulatory system?
A
In larger bodies blood has to travel further to reach all cells.
10
Q
What are the adaptions to maximise the transport of gases and nutrients?
A
closed circulation vs open
single vs double circulation
4 chambered heart.
11
Q
high metabolic rates need….
A
efficient gas exchange.
12
Q
which animals have open circulatory systems?
A
insects
other arthropods
some mollusks
13
Q
describe an open circulatory system
A
one or more hearts to generate propulsive force.
no distinction between tissue fluid and blood = haemolymph bathes cells directly and consists of haemocytes (immune cells) and liquid component.
blood enters into branching arrangment of vessels and empties in sinuses or lacunae i.e. haemocoel.
BLOOD PRESSURE LOW AND VOLUME HIGH.
no respiratory pigments pr haemocyanin.
14
Q
how do insects with open systems transport oxygen?
A
tracheal system.
15
Q
what is the dorsal vessel in insects?
A
the main driver of haemoloymph circulation containing aorta and heart (with ostia(small pores))
16
Q
what are accessory pulsatile organs or auxiliary hearts in insects?
A
peripheral circulation in the appendages driven by autonomous pumps.
17
Q
describe haemoglobin
A
iron based
bound to red blood cells
high affinity for oxygen
readily releases oxygen
sensitive to changes in ph and temperature.
18
Q
describe haemocyanin
A
copper based
free floating
lower affinity to oxygen
lower release rate
less sensitive to ph and temperature.
19
Q
who has haemoglobin?
A
humans and majority of other vertebrates
20
Q
who has haemcyanin?
A
spiders, crustaceans, some mollusc’s, octopuses, and squid.
21
Q
which animals have closed circulatory systems?
A
annelids
cephalopods
vertebrates
humans
22
Q
describe a closed circulatory system
A
hearts generate propulsive force
blood is kept separate from interstitial fluid and cellular and macromolecular components never leave the vessels.
blood contains, red blood cells, white blood cells, platelets, and plasma.
blood pressure high
red blood cells contain haemoglobin (iron based)
23
Q
what animal has three hearts?
A
octopus
they have 2 branchial hearts that pump blood through bills and 1 systemic heart that stops when the octopus swims.
the atria and ventricle contract in synchrony.
24
Q
what would be a benefit of an octopus having 3 hearts?
A
enhancement of oxygen delivery.
25
describe the circulatory system in fish
closed.
single circulation.
two-chambered heart (and bulbus connected in series)
unidirectional flow of blood is enabled by one-way valves between the heart chambers.
DISADVANTAGES: inefficient as loss of blood pressure after gills -> slows delivery of oxygen to tissues.
26
describe the circulatory system in LUNG fish
closed
lungfish intermediate between breathing water to breathing air.
an outpocketing of the gut forms a lung.
some vessels in the gill arches are modified to carry blood.
atrium is partially divided.
27
describe the circulatory system in amphibians
closed
three chambered heart
ventricle directs blood flow to either the pulmonary or systemic circuit.
can pick up oxygen from small vessels in skin.
ADVANTAGES: partial separation of pulmonary and systemic circulation allows blood going to the tissues to sidestep the large pressure drop that occurs in the gas exchange organ.
28
describe the circulatory system in reptiles
closed
three chambered heart (with septum)
two aortas
can bypass the pulmonary circuit when inactive by changing resistance in pulmonary circuit - cardiac shunt
low when breathing, high when not breathing
ADVANTAGES: saves cardiac energy, facilitates warming, triggers hypometabolism.
29
describe the circulatory system in birds and mammals
four chambered heart (with septum)
pulmonary and systemic circulation completely separated.
ADVANTAGES: systemic circuit always receives blood with higher O2 content.
gas exchanged is maximised.
circuits can operate at different pressures.
30
how does the right side of the heart receive oxygen?
coronary arteries
31
compare bird and mammalian hearts
birds and mammals are derived from different groups of reptilian ancestors and the anatomically complete double circulation thus arose independently twice -> convergent evolution.
birds tend to have larger hearts than mammals (relative to body size)
cardiac output (amount of blood pumped per minute) for birds is typically greater than that for mammals of the same body mass.
32
what is the structure of an ectothermic vertebrates heart? (hagfish through fishes, amphibians, and reptiles)
trabecular
sponge like ventricle with 100% ejection fraction.
33
what is the structure of birds and mammals hearts?
single-lumen ventricles composed of compact walls with 50% ejection fraction.
34
whats the cardiac output?
volume of blood pumped by each ventricle and equals the product of heart rate and stroke volume.
cardiac output (l/min) = heart rate X stroke volume
CO=HRxSV
35
what is the heart?
muscular organ in the centre of the thoracic cavity.
36
what is the heart composed of?
epicardium - outermost layer, reduces friction.
myocardium- thick layer, contains cardiac muscle.
endocardium- innermost layer, contact with blood.
37
whats the pericardium?
protective membrane around the heart.
38
describe the mammalian heart
4-chambered heart.
the chambers contract in a coordinated way in response to electrical excitation from pacemaker cells in heart.
38
explain stroke volume
volume of blood that is ejected from a ventricle with each heartbeat.
directly related to the force generated by cardiac muscle during contraction.
39
explain heart rate
number of beats per time interval.
40
describe the cardiac cycle
the period of time that begins with contraction of the atria and ends with ventricular relaxation is known as the cardiac cycle.
both atria and ventricles undergo systole and diastole and these events are carefully regulated to ensure blood is pumped efficiently to the body.
valves play an important role (artio-ventricular valves and semilunar valves)
41
whats a systole?
period of contraction when heart is emptying.
42
what is diastole?
period of relaxation as the chambers fill with blood.
43
whats ejection fraction?
EDV(end-diastolic volume) - ESV(systolic volume)
divide the final value with EDV to find ejection fraction.
44
what does the force ventricular contraction depend on?
preload (end diastolic volume) -> length of muscle fibres.
contractility -> ability of cardiac muscle to contract at any given fibre length.
afterload (pressure required to open aortic valve).
45
what are the cardiovascular trends?
smaller animals have higher HR.
birds generally have higher HR than mammals of similar size.
Systolic volume increases with body size.
Cardiac output per kg body mass are similar.
Blood pressure is similar across animals; with notable exceptions.
46
what are the 2 types of cardiac muscle?
contractile
non-contractile (pacemaker cells) 1%
47
what are pacemaker cells?
cells that generate action potentials autonomously (myogenic)
48
describe cardiac muscles
smaller and only have a single nucleus per fibre and connected to each other via intercalated discs.
49
what are gap junctions function?
direct transmission of the depolarising current from cell to cell.
50
what are desmosomes function?
hold the cardiac muscle cells together during contraction.
51
what is excitable tissue?
cardiac muscle is an excitable tissue meaning that it has the ability to generate signals that may be quickly transmitted to other cells.
each type pf cardiac muscle cell has a distinctive action potential
Ca2+ plays an important role in both.
52
describe a cardiac pacemaker potentials
no stable resting potential.
action potential that occur in pacemaker cells.
determine heart rate.
53
describe a cardiac action potentials
stables resting potential.
action potentials that precede contraction in all cardiac muscle fibres (except pacemaker cells)
54
what is action potential?
a rapid change in the membrane potential causing depolarisation, followed by depolarisation.
55
what is depolarising?
when the membrane potential moves toward zero.
result of Na+ entry.
56
what is repolarising?
when the membrane potential moves back negative after depolarisation.
result of K+ leaving the cell.
57
is membrane potential positive or negative?
negative
(is polarised)
58
whats an effective refractory period?
resting period where the heart does not respond to a stimulus or produce an action potential.
59
whats the function of the effective refractory period?
prevents arrythmias and coordinates muscle contraction.
60
how does the effective refractory system work?
during ERP simulation of the cell by an adjacent cell undergoing depolarisation does not propagate an action potential.
no summation of contractions like in skeletal muscle.
61
how do we compare action potentials?
differences in resting membrane potential.
length of depolarisation phase.
movement of ions.
62
where does the action potential enter from?
an adjacent cell.
63
how does the membrane potential work?
concentration of Na+,K+, and Ca2+ ions is NOT equal across cell membrane.
Na+ and Ca2+ out>>in.
K+ in>>out.
voltage gated Na+, Ca2+, and K+ channels control cardiac cell membrane permeability to specific ions.
64
how do ions pass the cell membrane?
through ion channels.
65
how is pacemaker potentials depolarised?
a calcium influx.
if channels are permeable to both K+ and Na+ ions causes slow depolarisation up to threshold.
66
whats a myogenic heart?
a heart that can initiate its own contractions.
contains many cells capable of pacemaker activity, but the cell with the fastest intristic activity is the one that simulates the whole heart to contract and determines heart rate.
if this cell stops others can take over with a slower heart rate.
67
whats the propagation of electrical signal in the heart.
sinoatrial (SA) node initiates signal.
artioventricular (AV) node acts as a gatekeeper.
bundle of his a pathway of specialised nerve fibres.
purkinje fibres the fibres which simulate the ventircles to contract.
68
whats an electrocardiogram?
reflects electrical activity in the heart and provides a non-invasive way of assessing cardiac function.
69
whats the first curve on an ECG?
signals from SA node spreading through artia.
70
what is the straight line on an ECG?
signals are now being delayed at AV node.
71
what is the slope on an ECG?
bundle branches passing signals to heart apex.
71
whats the peak on an ECG?
signals spreading throughout ventricles.
72
what are the control autonomic functions of the body?
respiration.
heart rate.
digestion.
73
whats the sympathetic nervous system?
known as fight or flight.
counteracts the autonomic nervous system.
prepares body for stress (increases heart rate in emergencies).
74
what is the parasympathetic nervous system?
the system that relaxes the body after a sympathetic nervous system response.
75
what counteracts the autonomic nervous system?
sympathetic and parasympathetic nervous systems.
76
what is norepinephrine?
released by the sympathetic nervous system to accelerate the heartbeat by activating Ca2+ and Na+ channels via B1- receptors.
77
what is acetylcholine?
released by the parasympathetic nervous system to slow the heartbeat by increasing K+ conductance and reducing Ca2+ conductance via muscarinic receptors.
78
what do chemoreceptors detect?
changes in respiratory gases CO2 and O2.
79
what do baroreceptors detect?
changes in blood pressure.
80
what do proprioceptors detect?
changes in muscle movement.
81
what is preload in the context of stroke volume?
determined by the amount of blood returned to the heart (venous return).
82
what is afterload in the context of stroke volume?
determined by resistance in blood vessels/ blood pressure (which is under autonomic control).
83
what is contractility in the context of stroke volume?
can be controlled by hormones and autonomic control (sympathetic nervous system).
84
3 types of blood vessels
arteries.
capillaries.
veins.
85
what is the function of arteries?
to carry blood AWAY from the heart under high pressure.
86
describe the structure of an artery.
ensures there is a continuous and constant flow of blood to the capillary beds, narrow lumen to maintain high blood pressure.
thick muscular walls and a large amount of elastic and fibrous connective tissues (elastic recoil) to maintain blood pressure.
elastic walls but walls become less elastic and more muscular in arteries further from heart. this muscle allows constriction and dilation.
thick outer layer of collagen on outer wall to withstand high pressure of blood.
87
what is the function of capillaries?
allow exchange of materials between the blood and the tissue fluid.
88
describe the structure of capillaries
no muscle.
extensive network (no cell is more than 3-4 cells away from a capillary).
very narrow lumen reducing rate of flow providing a short diffusion distance.
walls consist of single layer of flattened endothelial cells with gaps between allowing materials to enter and leave the blood.
89
what contributes to the permeability of capillaries?
pericytes
90
what are micro capillary beds?
the main site of exchange.
filtration and absorption.
91
how do micro capillary beds work?
plasma, containing dissolved oxygen and nutrients, is forced through the capillary wall at the arteriole end of the capillary bed.
cells, platelets, and large plasma proteins remain in blood.
at venule end, tissue fluid is returned to blood and contains waste products from cells.
net loss of fluid - remainder is taken up by lymphatic system.
92
what is the function of veins?
carry blood towards the heart under low pressure.
storage of blood.
93
what regulates blood flow in in the capillary beds?
precapillary sphincters.
94
what causes vasoconstriction of the venous system?
blood loss.
vasoconstriction is regulated by the sympathetic nervous system and reduces venous blood volume in order to maintain arterial pressure and capillary blood flow.
95
describe the structure of veins.
wider lumen to reduce resistance and allow the blood to flow faster.
thinner layer of elastic tissue as veins do not need to expand and recoil to maintain blood pressure.
thinner layer of smooth muscle as veins do not need to constrict and dilate to maintain blood pressure.
thinner layer of collagen and elastic fibres in outer wall as the blood is under very low pressure.
presence of valves to prevent backflow of blood.
96
what is the cellular fraction of blood?
red and white blood cells.
97
what is the liquid fraction of blood?
plasma.
98
what does enucleated mean?
contain no nuclei.
99
what does cell width correlate with?
capillary diameter.
100
describe red blood cells in mammals?
enucleated and circular rather than elliptical. most likely an adaption to increase oxygen uptake.
101
another name for red blood cells?
erythrocytes
102
is a bird or mammal red blood cell more efficient?
mammal.
their rbcs are smaller and have a greater surface area due to lack of nucleus.
103
whats the pressure in the aorta?
93mm Hg
104
what is the pressure in the vena cava?
1-5mm Hg
105
how does blood flow?
down a pressure gradient from high to low.
the heart creates high blood pressure when it contracts and as it flows through the system pressure is lost due to friction from the blood vessel walls.
aorta -> vena cava
the higher the pressure the greater the flow (the absolute pressure does not affect flow).
106
whats pressure in a fluid?
the pressure exerted by the fluid on its container and is measured in mm Hg.
107
whats hydrostatic pressure?
the force fluid exerts when it is not moving.
108
what is driving pressure?
when fluid cannot be compressed so when ventricles of the heart contract the fluids is forced out.
109
whats the blood flow equation?
change in P/ R
110
what happens when ventricles relax?
pressure inside the fluid filled chamber falls.
111
what is resistance in circulatory terms?
the tendency of the cardiovascular system to oppose blood flow.
112
whats the relationship of flow and resistance?
flow is inversely related to resistance.
113
what factors affect resistance?
radius of the tube.
length of the tube.
viscosity of the fluid.
114
whats poiseuilles law?
R = L n / r4
the resistance of a fluid increases with viscosity and length, but decreases with tube diameter.
115
what is blood flow?
volume of blood that passes a given point in a system per unit of time (L/min).
116
what is velocity in circulatory terms?
the distance a fixed volume of blood travels in a given period of time (m/s).
117
velocity (circulatory) calculation.
V = Q/A
velocity (V) depends on the flow (Q) and cross-sectional area (A) of the tube.
118
is velocity (circulatory) faster in narrow or wide sections?
faster in narrow and slower in wide.
119
what is blood pressure?
the pressure that your blood exerts against your arteries as it is pumped through your body by the heart.
the pressure in the arteries in the arteries increases when the heart beats (systole) and decreases while it is resting (diastole).
THE MEASUREMENT OF FORCE APPLIED TO ARTERY WALLS
120
what happens to blood flow during diastole?
during diastole, aortic valve closes and the elastic arterial walls recoil, propelling blood forward and sustaining the driving pressure for blood flow during diastole ensuring continuous flow of blood.
121
what is meant arterial blood pressure?
a balance between blood flow in and out of the arteries.
cardiac output x resistance.
122
factors affecting arterial blood pressure
blood volume.
effectiveness of the heart as a pump (cardiac output).
resistance of the system to blood flow.
relative distribution of blood between arterial and venous blood vessels.
123
factors affecting blood pressure?
local control: myogenic auto-regulation, paracrine signals.
sympathetic reflexes
hormones (salt and water excretion).
124
explain sympathetic control of blood pressure
most systemic arterioles are innervated by sympathetic neurons.
norepinephrine binds a-receptors on innervated muscles resulting in vasoconstriction.
epinephrine from adrenal medulla binds a-receptors (low affinity) causing vasoconstriction and B2-receptors on smooth muscle of heart, liver and skeletal muscle which are not innervated causing vasodilation
these mechanisms allow blood to be diverted from non- essential organs. (fight or flight)
125
how can blood flow be redistributed?
by altering arterial resistance.
blood is diverted from high to low resistance arterioles.
126
where is the cardiovascular control centre?
medulla oblongata.
127
describe the blood pressure of tree climbing snakes
they generate greater blood pressures when at rest than other species of snake and can increase blood pressure even more when head is tilted.
128
describe a giraffes circulation
MAP of 200mm Hg and an arterial pressure at the head of about 100mm Hg.
powerful heart together with thick, elastic arteries generate and maintain high blood pressures.
adaptions to blood vessels prevent sudden pressure fluctuations and prevent pooling of blood in head or legs.
