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MCAT Biology > Circulatory and Cardiovascular System > Flashcards

Circulatory and Cardiovascular System Flashcards

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1
Q

What is the function of blood?

A

Transport oxygen to tissues
Carry away carbon dioxide from tissues
Regulate extracellular environment of body by transporting nutrients, waste products, and hormones
Important for thermoregulation

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2
Q

How does the circulatory system control thermoregulation?

A

Dilation of peripheral blood vessels allows the body to radiate heat and cool off
Constriction of peripheral blood vessels prevents heat loss in cold temperatures

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3
Q

What type of tissue is the blood?

A

Connective tissues

Contains cells and a matrix

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4
Q

What are the three main components of the blood?

A
  1. Plasma
  2. Red blood cells
  3. Buffy coat (white blood cells)
    Separate when a blood sample is placed in a centrifuge
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5
Q

Plasma

A

Contains matrix of the blood
Includes water, ions, urea, ammonia, proteins, and other organic and inorganic compounds
Alter amount of water in plasma to control blood volume and pressure
Proteins in plasma: albumin, immunoglobulins, clotting factors

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6
Q

Albumins

A

Transport fatty acids and steroids

Help regulate osmotic pressure of the blood- facilitate transfer of substances across capillary walls

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7
Q

Immunoglobulins

A

Antibodies

Major component of immune system

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8
Q

Serum

A

Blood plasma from which clotting protein fibrinogen has been removed

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9
Q

Where are albumin, fibrinogen, and most other plasma proteins formed?

A

Liver

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10
Q

Where are Gamma globulins (constitute antibodies) made?

A

Lymph Tissue

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11
Q

What is an important function of the plasma proteins?

A

Act as a source of amino acids for tissue protein replacement

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12
Q

Erythrocytes

A

AKA Red blood cells
Disk-shaped vesicles with main function to transport O2 and CO2
Essentially all hemoglobin
No organelles, no nuclei, do not undergo mitosis
Squeezing through plasma membranes wears out organelles in 120 days- then removed from circulation and destroyed when entering spleen/liver

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13
Q

Hematocrit

A

Percentage by volume of RBCs

35-50% greater in men than women

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14
Q

Leukocytes

A

AKA white blood cells
Contain organelles, do not contain hemoglobin
Protect body from foreign invaders

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15
Q

Where do all blood cells differentiate from?

A

Come from precursor cell or stem cell residing in bone marrow
Erythrocytes lose nuclei while still in marrow, and lose other organelles within 1 or 2 days after entering blood stream

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16
Q

Granulocytes

A

AKA Granular leukocytes
Neutrophils (neutral to basic and acidic dyes), eosinophils (stain in acidic dyes), and basophils (stain in basic dyes)
Remain in blood for only 4-8 hours before deposited in tissue to live for 4 to 5 days

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17
Q

Neutrophils

A

Most abundant type of granular leukocyte

First responders to scene of infection to kill foreign pathogens and recruit other immune cells

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18
Q

Agranular leukocytes

A

AKA agranulocytes
Monocytes, lymphocytes, megakaryocytes
Monocytes -> macrophages, live for months - years
Lymphocytes may live for years

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19
Q

Platelets

A

Small portions of membrane-bound cytoplasm torn from megakaryocytes
Do not have nuclei
Contain actin and myosin, mitochondria, and residual pieces of Golgi body and endoplasmic reticulum
Capable of making prostaglandins and some important enzymes
Half life of 8-12 days in the blood, need many platelets to be healthy

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20
Q

How do platelets aid coagulation?

A

Platelets come in contact with injured endothelium and become sticky and begin to swell, releasing various chemicals
Activate other platelets
Platelets stick to endothelium and to each other, forming loose platelet plug
Trigger enzymatic cascade that results in formation of blood clot

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21
Q

Coagulation

A

Functions to minimize blood loss and facilitate healing when blood vessels are damaged
Begins with platelets coming in contact with injury, releasing enzymes, sticking together to form platelet plug
Polymerization of plasma protein fibrinogen to form fibrin threads that attach to platelets to form tight plug

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22
Q

How fast does coagulation begin to appear?

A

Seconds in small injuries, 1-2 minutes in large injuries

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23
Q

What is the percentage of leukocyte composition in the blood?

A

Neutrophils: ~62%, Lymphocytes: ~30%, Monocytes: ~5.3%, Eosinophils: ~2.3%, Basophils: ~0.4%

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24
Q

What is the reason for the difference in lifespan between granulocytes and agranulocytes in the blood?

A

Granulocytes live for very short time, function nonspecifically against all infective agents
- multiply quickly against any infection, and die once infection is goneu
Agranulocytes live for longer period of time, function specifically against pathogens, hang around in case same infective agent returns

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25
Q

Cardiovascular system

A

Consists of heart, blood, blood vessels
Transport system that pumps blood throughout the body, carrying out functions of extracellular environment regulation and the delivery of nutrients, oxygen, hormones, immune cells to tissues
Removes waste products

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26
Q

How does the cardiovascular system react to endocrine and nervous control?

A

Directs the flow of blood in response to both systems
Epinephrine and norepinephrine which are released by neurons of SNS and by adrenal medulla of endocrine system can cause constriction of blood vessels
Divisions of cardiovascular system into smaller and smaller branches allows strict regulation of flow of blood according to metabolic needs of specific tissue

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27
Q

Closed circulatory system

A

Cardiovascular system contains no openings for blood to leave the vessels
First half: systemic circulation directs oxygenated blood to tissues and then returns deoxygenated blood to heart
Second half: pulmonary system transports blood to the lungs for oxygenation

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28
Q

What is the path of the circulatory system through the systemic circulation?

A

Blood pumped from left ventricle through aortic valve into aorta
Branch into arteries and then arterioles, which branch into capillaries
Blood from capillaries is collected into venules, which collect into larger veins that collect again into superior and inferior venae cavae
Venae cavae empties into right atrium of the heart

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29
Q

What is the path of the blood through pulmonary circulation in the heart?

A

Blood squeezed through tricuspid valve from the right atrium into the right ventricle
Right ventricle pumps blood through the pulmonary valve to pulmonary arteries, arterioles, and then capillaries of the lungs
From capillaries of lungs, blood collects in venules, then in veins, and finally in pulmonary veins leading to left atrium of heart, leading to left ventricle through the mitral/bicuspid valve

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30
Q

Compare and contrast the left and right ventricles of the heart

A

Both ventricles pump blood out of heart towards an area of the body
The left ventricle pumps blood to the entire systemic circulation, so must have greater force (more muscular, thicker walls)
Right ventricle pumps blood to pulmonary system, pumping waste RIGHT out of the body and returning with oxygen

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31
Q

Name all of the valves in the heart and where they are located

A

Pulmonary valve is located in the right ventricle on the way to the pulmonary arteries
Aortic valve is located in left ventricle on the way to the aorta
Tricuspid valve is located in right atrium on the way to right ventricle
Mitral/bicuspid valve is located in left atrium on the way to left ventricle

32
Q

How do the regular contractions in the heart come about?

A

Stimulated by electrical activity (action potentials)
Special groups of cells in the heart initiate cardiac impulse
Nervous system regulation of these cells can slow down or speed up the heart rate according to the body’s needs

33
Q

Systole

A

Ventricles contract and send blood out of the heart

34
Q

Diastole

A

Relaxation of the entire heart, and then contraction of the atria

35
Q

What controls the rate of contraction of the heart?

A

Autonomic nervous system
Does not initiate contractions, however
Heart contracts according to the pace set by the sinoatrial (SA) node

36
Q

Sinoatrial node

A

SA node
Group of specialized cardiac muscle cells located in the right atrium
Autorhythmic (contracts by itself at regular intervals)
Spreads contraction to surrounding cardiac muscles via electrical synapses formed by gap junctions
Conducting cells gather into fibers that ensure coordinated spread of action potentials

37
Q

Is the pace of the SA node faster or slower than normal heartbeats?

A

Parasympathetic vagus nerve innervates the SA node, slowing contractions to produce typical resting heart rate
Increased or decreased parasympathetic input can trigger quick changes in heart rate in response to organism’s internal and external environment

38
Q

What is the propagation of electrical impulses throughout the heart from the SA node?

A

Action potential from SA node spreads to both atria (contraction)
Simultaneously, spreads to atrioventricular (AV) node located in the interatrial septum (wall of cardiac muscle between atria)
AV node is slower to depolarize, creating delay in impulse so atria finish contractions
APs move from AV node down conductive fibers called bundle of His (wall separating ventricles), then branching out through ventricular walls via conductive fibers called Purkinje fibers. AP spreads through gap junctions from one cardiac cell to another

39
Q

Purkinje fibers

A

Conductive fibers in the ventricular walls of the heart

Allow for more unified and stronger contraction, after receiving APs from the bundle of His

40
Q

Atrioventricular node

A

AKA AV Node
Group of specialized cardiac muscle cells located in interatrial septum (wall of cardiac muscle between atria)
Depolarizes slower than SA node and allows for contraction of atria before passing signal to bundle of His

41
Q

Bundle of His

A

Conductive fibers located in the wall separating the ventricles
Receives signal from atrioventricular node and passes signal to the Purkinje fibers

42
Q

What are the three major types of blood vessels?

A

Arteries, capillaries, and veins

Physical characteristics allow for difference in function related to radius, wall thickness, and elasticity

43
Q

Arteries

A

Serve as a pressure store, facilitating travel of blood to lower-pressure venous system
Thick elastic walls that stretch as they fill with blood during systole, and recoil after ventricular contraction to maintain blood pressure
Wrapped in smooth muscle that is typically innervated by SNS, medium arteries have more smooth muscle / volume than large arteries, can reroute blood
Epinephrine is powerful vasoconstrictor

44
Q

Arterioles

A

Very small, wrapped in smooth muscle
Constriction and dilation of arterioles in response to stimulation from nervous and endocrine systems can be used to regulate blood pressure and reroute blood
Thermoregulation: control flow of warm blood to capillary beds in skin (dilate to allow radiative heat transfer outside of body)

45
Q

Capillaries

A

Microscopic blood vessels
Have huge total surface area created by branching of larger structures (alveoli)
Walls composed of endothelial cells one cell thick, diameter ~1 RBC thick
Thin walls well-suited for transport of materials (nutrient and gas exchange)
Substances travel across capillary wall and enter interstitium

46
Q

Interstitium

A

Fluid surrounding cells in cellular networks known as tissues
Differential pressure between interstitium and blood in the adjacent capillary guide the transfer of materials

47
Q

What are the four methods that materials cross capillary walls?

A
  1. Pinocytosis
  2. Diffusion or transport through capillary cell membranes
  3. Movement through pores in cells called fenestrations
  4. Movement through spaces between cells
48
Q

How is the rate of diffusion across a membrane related to thickness of a membrane?

A

Rate of diffusion is inversely proportional to thickness of membrane
Makes capillaries well-suited for nutrient and gas exchange (1 cell thick endothelial)

49
Q

What determines the method by which substances use to cross capillary walls?

A

Solubility, size
Small lipid-soluble molecules (O2, CO2) diffuse through endothelial membrane
Water-soluble substances pass through gaps between cells
Proteins are large and charges, so only pass when able to perform pinocytosis or through fenestrations

50
Q

Veins

A

Volume store for blood traveling back towards the heart
Larger lumen than comparable arteries
Walls much thinner and have less elasticity (can stretch to hold a far greater volume of blood)
Contain one-way valves to prevent backflow of blood

51
Q

What is the percentage of blood in each area of the cardiovascular system?

A

Veins, venules, venus sinuses contain ~64% of blood in body at rest
Arteries, arterioles, capillaries contain ~20% of blood
Heart contains ~7%
Pulmonary circulation ~9%

52
Q

Which artery in the body is deoxygenated?

A

Pulmonary artery

53
Q

What is an analogous relationship that can be used to understand the mechanics of pressure difference and fluid flow throughout the circulatory system?

A

Analogous to relationship between voltage and current flow
Where voltage / pressure provide the driving force through the system, and current / fluid flow are the amount of flow through the system
Q = delta P / R
I = V / R

54
Q

Systolic pressure

A

Highest pressure, measured in the arteries during systole

55
Q

Diastolic pressure

A

Pressure during relaxation of ventricles and filling of the atria
Lowest pressure in cardiac cycle

56
Q

Why must blood pressure in the arteries be kept at such a constant high level?

A

Kept at around 100 mm Hg to provide sufficient drivig pressure for blood to travel through systemic circulation and back to the heart
Blood pressure drops as it travels through the circulatory system
Insufficient pressure in arteries would provide insufficient pressure at capillaries for nutrient and waste exchange

57
Q

What are the two main methods used by the body to regulate blood pressure?

A

Baroreceptor reflex: quick nervous system control
Renin-angiotensin-aldosterone system (slower, more prolonged hormone control)
Involve detection of changes in blood pressure by mechanoreceptors and alter blood pressure by changing output of blood from the heart and total peripheral resistance

58
Q

Total peripheral resistance

A

Overall resistance of entire systemic circulatory system
Changes in total peripheral resistance are primarily achieved through constriction or dilation of smooth muscle surrounding arterioles (blood vessels that contribute the most to peripheral resistance)

59
Q

What happens to resistance when a blood vessel is constricted?

A

Cross sectional area of blood vessel decreases and resistance increases
Increasing resistance of arterioles throughout peripheral circulation increases TPR

60
Q

What is the analogous relationship in thinking of the total resistance through capillaries?

A

A bunch of resistors in parallel
Blood able to flow through many capillaries that are arranged in parallel
Decreases overall resistance of the capillary bed

61
Q

How does the baroreceptor reflex regulate blood pressure?

A

Alters both cardiac output and blood vessel resistance to flow
Baroreceptors (type of mechanoreceptor) are located within arteries to detect changes in blood pressure
Respond by signaling centers in brainstem to alter SNS and PNS output to heart and blood vessels
SNS: counteracts decrease in blood pressure by causing heart rate to increase and blood vessels to constrict
PNS: counteracts increase in blood pressure by slowing heart rate

62
Q

Renin-angiotensin-aldosterone system

A

Regulates blood pressure through regulation of plasma volume
System activated when mechanoreceptors in arteries leading to kidneys detect a decrease in blood pressure
Cascade of enzymatic effects triggered by secretion of renin (enzyme) leads to increased intake and retention of water, increasing plasma volume, increasing blood pressure
Aldosterone and antidiuretic hormone involved

63
Q

How does cross-sectional area of veins compare to arteries?

A

Total cross-sectional area of veins is four times that of arteries
Total cross-sectional area of capillaries is far greater than cross-sectional area of either arteries or veins

64
Q

How is blood velocity related to cross-sectional area?

A

Blood volume flow rate is approximately constant through system
Blood velocity is inversely proportional to cross-sectional area
Movement of blood is slowest in capillaries (more time for nutrient, waste exchange)

65
Q

Poiseuille’s Law

A

Q = delta P * (pi * r^4 / 8 * eta * L)
Flow is directly proportional to pressure difference
Radius has largest impact, nervous system input to smooth muscle can have big impact
Eta is dynamic viscosity, L is length of vessel, Q is volumetric flow rate

66
Q

How does pressure change as it flows through circulatory system?

A

Highest in arteries after exiting the left ventricle, lower in capillaries, lowest in veins allowing blood to pool and be transferred back to heart
Veins have valves to prevent backflow due to low pressure

67
Q

What is the major propulsive force that moves blood through the veins?

A

Pumping of the heart

Contraction of skeletal muscle also helps move blood through veins, but secondary factor

68
Q

How does cross-sectional area and blood pressure vary as blood moves through systemic circulation?

A

Add graphs on page 126 of Biology 2 via website

69
Q

Continuity Equation

A

Q=Av
A: cross-sectional area, v is velocity, Q is flow rate
Means that velocity is highest in arteries where A is lowest, and velocity is lowest in capillaries where A is highest

70
Q

What is Bernoulli’s equation and how does it relate to blood flow?

A

Total pressure = static pressure + dynamic pressure
Sum of potential energy, kinetic energy, and pressure of a flowing fluid is equal to a constant
Decrease in velocity of blood should correspond to increase in pressure
However, does not mean that blood pressure is higher in capillaries, however blood is not ideal fluid and energy is lost due to friction against walls of blood vessels

71
Q

Precapillary sphincters

A

Regulate flow of blood into capillary beds according to metabolic needs of tissues
Band of contractile mural cells (smooth muscle or pericytes)

72
Q

What are the two types of pressure across the wall of the capillary?

A

Osmotic pressure: “pulling” pressure of solutes in solution that leads to diffusion of solutes across a membrane
- encourages flow of fluid from tissues into capillaries, constant and set by proteins that are too large to move through membranes
- Overcomes hydrostatic pressure near venule end (interstitium to capillary)
Hydrostatic pressure: Due to slow movement of fluid in capillaries, exerts high pressure on the walls to encourage flow of fluid into interstitium
- First pressure as blood enters capillaries, drops as moves towards venule end

73
Q

What is the net result of fluid exchange by capillaries?

A

10% loss of fluid from capillaries to interstitium

Lymphatic system acts to prevent excess fluid buildup in tissues

74
Q

Filtration

A

Movement of fluid into the interstitium

75
Q

Reabsorption

A

Movement of fluid back into blood vessels

76
Q

Stroke Volume

A

Amount of blood pumped per contraction by either left or right ventricle

MCAT Biology (14 decks)

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