Unit 4; Cardiovascular System (Part 2) Flashcards
What are the 4 components of cardiac regulation
- cardiac output
- factors influencing heart rate
- factors influencing stroke volume
- factors affecting venous return
What is the equation for cardiac output
heart rate x stroke volume
Stroke volume = _______ - _______
Stroke volume = (EDV - ESV)
*big number minus small number
CO = 72 beats/min x 70 mL/beat
what is the cardiac output
*In-class knowledge testing question
5040 mL/min (approx. 5L per min)
What is meant by cardiac output
the amount of blood pumped by the heart in one minute
What 3 factors influence heart rate
- parasympathetic stimulation: decreases heart rate
- via vagus nerve; acetylcholine - sympathetic stimulation: increases heart rate
- via great cardiac nerve; norepinephrine - plasma epinephrine (from the adrenal medulla): increases heart rate
What 4 factors influence stroke volume
- parasympathetic stimulation; decreases contractility
- sympathetic stimulation; increases contractility
- plasma epinephrine; increases contractility
- increased end-diastolic volume; increases stroke volume
What 4 factors influence venous return
- total blood volume; more blood means more can be loaded into ventricles
- sympathetic vasoconstrictor nerves; constrict blood vessels pushes blood towards heart
- skeletal muscle pump; muscle contractions push blood towards the heart
- respiratory pump; creates low pressure in thorax and high pressure in abdomen
What is the physical structure of blood vessels
hollow tubes made up of;
lumen: central cavity
wall: made of layers
(review figure 4.9*)
Where does the blood flow in the blood vessel
the lumen (central cavity)
What are the components of the blood vessel wall
inner lining (endothelial cells make up endothelium)
elastic connective muscle
vascular smooth muscle
fibrous connective tissue
(refer to figure 4.9*)
What is vasoconstriction
narrowing of blood vessel
What is vasodilation
expansion (widening) of blood vessel
What are the 5 types of blood vessel
artery
arteriole
capillary
venule
vein
(*review figures 15.2 and 15.3)
What is the main characteristic of arteries
thick-walled to withstand high pressures
What is the main characteristic of arterioles
small arteries
What is the main characteristic of capillaries
smallest blood vessel (highest surface area): used for exchange of materials
What is the main characteristic of venules
small veins
What is the main characteristic of veins
transport blood at low pressure
Why does blood flow
because of a pressure gradient between arteries and veins (flow is directly proportional to the pressure gradient)
pressure gradient (delta P)
arteries (P1 - highest)
veins (P2 - lowest)
*therefore P1-P2 = delta P (change in pressure)
(*review figure 14.3)
What is the change in pressure when 100mm Hg moves to 75mm Hg
100-75 = 25mm Hg
What is the change in pressure when 100mm Hg moves to 100mm Hg
no change in pressure: no pressure gradient
What 4 factors influence blood flow in the vessels of the body
- myogenic autoregulation (vascular smooth muscle)
- stretch receptors in the walls of arterioles that cause vasoconstriction when activated - paracrine hormones
- released from vascular endothelium and tissues
- causes vasodilation or vasoconstriction - innervation by sympathetic division of autonomic nervous system
- norepinephrine binds to alpha receptors and causes vasoconstriction
- epinephrine binds to alpha receptors and reinforces vasoconstriction - hormonal signals via circling epinephrine
- binds to beta2 receptors
- found ONLY in the vascular smooth muscle of the heart, liver, and skeletal muscle arterioles*
- causes vasodilation
(*refer to page 79 of course notes and know this)
What does the term “vaso” refer to
blood vessels
How does resistance oppose flow
- pressure increases when volume decreases
- pressure is decreased by friction
Explain how pressure increases when volume decreases in the heart
heart generates pressure by contracting, and by doing so, increases the pressure (contracting decreases the volume)
Explain how pressure is decreased by friction in the circulatory system
friction occurs between blood and the walls of the blood vessels
Friction exerted by a tube usually called…
resistance
Blood flows from ______ to ______ pressure
high to low
What is resistance determined by
length, radius, and viscosity
Of length, radius, and viscosity, change in which is most important under normal physiological conditions
radius
L represents
length
n represents
viscosity
r represents
radius
Adjustments are made in which variable
r - the radius of the blood vessels
In the human body, which two variables are almost always constant
L and n
For fluid in a tube, what is the equation
R = 8Ln/πr^4
Since the flow is proportional to the pressure difference and inversely proportional to the resistance, …
F is proportional to delta P/R
Arterial blood pressure reflects the driving pressure cause by the _________ ______________
heart pumping
- highest in arteries
- lowest at point of return to the heart
- your pulse is increase in pressure caused when ventricles contract and push blood into aorta
What two parts make up blood pressure
systolic pressure: the time when heart is contracting (highest arterial pressure)
diastolic pressure: the time when ventricle relaxes (lowest arterial pressure)
What is the estimation of blood pressure determined by
sphygmomanometry (use of blood pressure cuff and stethoscope)
What are the steps of sphygmomanometry
- inflate the cuff to cut off blood flow
- cuff is gradually deflated, when pressure in cuff = the systolic pressure, blood will start to flow
- turbulent flow results in sound (Krotkoff sound)
- cuff pressure is further reduced
- eventually all sound will cease because flow is no longer turbulent; diastolic pressure
What does MAP stand for
mean arterial pressure
How is mean arterial pressure interpreted
since arterial pressure is pulsatile, use a single value to represent driving pressure
What is the MAP equation
mean arterial pressure
= diastolic P + 1/3(systolic P - diastolic P)
What factors affect mean arterial pressure
- cardiac output
- changes in blood volume (constant under normal circumstances*)
- peripheral resistance
What is peripheral resistance controlled by
arterioles (have large surfaces of smooth muscle in their walls - can modify diameter)
- small changes in radius result in large changes in pressure!
- influenced by both local and reflex control systems
What system coordinates regulation of blood pressure
central nervous system (CNS) - a homeostatic reflex
BP is monitored through sensory input from ______________________
baroreceptors
Carotid artery monitors…
blood pressure to brain
Aorta monitors…
blood pressure to body
Explain how baroreceptor reflex causes a decrease in blood pressure when too high
- membrane of baroreceptor stretches
- increases firing rate of receptor
- action potentials travel to CNS
- control center integrates the info
- efferent output carried by autonomic neurons
- decrease in sympathetic output & increase in parasympathetic output
- results in decrease in BP
(*review figure 15.14 and understand these steps)
What causes decreases in sympathetic output and increases in parasympathetic output
vasodilation
decrease in force of cardiac contraction and heart rate
decrease in peripheral resistance and cardiac output
What is blood
the circulating component of extracellular fluid responsible for carrying substances around the body
What are the 4 components of blood
plasma, RBCs, WBCs, and platelets
What is plasma
the fluid portion of the blood
What is the scientific term for red blood cells
erythrocytes
What is the shape of RBCs
bioconcave
Which blood cell type is most abundant in the blood
RBCs
What important protein do RBCs contain
hemoglobin
What is a major function of RBCs
gas transport (O2 and CO2)
What cell components are lacking in human red blood cells
nucleus and mitochondria
- rely on glycolysis to produce ATP
What is the scientific term for WBCs
leukocytes
What is the main function of WBCs
immune responses
What is the section of WBCs called in a centrifuge
Buffy coat
What are the 5 types of leukocyte
lymphocytes, monocytes, neutrophils, eosinophils, and basophils
What are the 3 types of granulocytes
neutrophils, eosinophils, and basophils
What are the natural phagocytes in the body
macrophages (monocytes) and neutrophils
What is another term for platelets
thrombocytes
What do platelets do
blood clotting
Where do platelets come from
megakaryocytes
- branches of these huge cells pinch off without a nucleus, and become platelets
What is hemoglobin needed for
RBC production (needed to transport oxygen)
Hemoglobin synthesis is a large complex molecule made up of 4 protein chains called
globins
Each globin subunit is wrapped around an iron containing ________ __________
haeme group
How is a haeme group iron-containing ?
The haeme group C-H-N porphyrin ring has an Fe in the center
Since a haeme group contains iron, what dietary nutrient must be consumed in order to maintain hemoglobin synthesis
iron
What shape is the hemoglobin-oxygen saturation curve
S shaped
- steep portion followed by a plateau
Do different forms of hemoglobin have different saturation curves?
yes
Hemoglobin binds reversibly to oxygen, what is an example of this process?
hemoglobin scoops oxygen from tissues with high oxygen partial pressure (like lungs) and carries it to areas of lower oxygen pressure (like muscle tissues)
What factors effect hemoglobin oxygen binding
temperature, pH, etc.
Factors that affect hemoglobin-oxygen binding alter the configuration of hemoglobin, which in turn, alters its properties. This is a form of _________ _______________
allosteric modification
Increase in temperature __________ hemoglobin-oxygen affinity
decreases
Decrease in temperature ____________ hemoglobin-oxygen affinity
increases
Increase in blood-oxygen levels, or increases in pH, cause __________ hemoglobin-oxygen affinity
decreases
The shift in hemoglobin-oxygen saturation due to pH change is due to the ________ effect
Bohr
What is the Bohr affect
the change in hemoglobin-oxygen saturation as a result of pH change
All hemoglobin-oxygen factors are elevated in the ________ relative to the _______
increased in tissues relative to the lungs
- see greater changes in temp, saturation, and pH in tissues vs lungs
The greater activity in a tissue, the greater the increase in ____,_____, etc.
pH and oxygen saturation
With greater activity comes greater O2 unloading on tissues, therefore we see a(n) ______________ in O2 release
increase
What is the process in which blood cells are formed
haematopoiesis
What does the word haematopoiesis break down into
Haima = blood
Poeisis = formation
All blood cells are produced in the _________ _________
bone marrow
All blood cells arise from a single precursor cell called a _____________ ________________ stem cell
pluripotent haematopoietic stem cell
What are the stages of blood cell development
pluripotent hematopoietic stem cells specify into uncommitted stem cells, which specify further into committed progenitor cells (committed to one or 2 specific cell types)
What directs the specification of stem cells
signalling molecules called cytokines
Where does the differentiation and specification of blood cells occur
in the bone marrow
What are cytokines
small peptides/proteins secreted by one cell to send signals to another
What are cytokines often called/described as
often called “factors”, with a descriptive word following to describe its function
- ie. growth factor, modifying factor, etc.
What is the formation of WBCs called
leukopoiesis
What is leukopoiesis regulated by
colony-stimulated factors (CSFs)
- remember this is a type of cytokine
Where are CSFs secreted
endothelial cells, WBCs, and marrow fibroblasts
What do CSFs induce
cell division and maturation in stem cells
Cytokines released by leukocytes regulate what
further leukocyte production
- ie. if you have an infection, more WBCs are produced
What is thrombopoeisis
the formation of platelets
What are the parent cells in thrombopoeisis
megakaryocytes
What regulates the growth and maturation of megakaryocytes
TPO (thrombopoietin)
Stem cells undergo ___________ up to 7x without undergoing nuclear or cytoplasmic division
mitosis
- this creates a polyploid (megakaryocyte is a polyploid)
Polyploid cells have a ________ nucleus
lobed
In the bone marrow, megakaryocytes extend their outer edges through the ____________ (cells lining the blood vessels) and into the _________________
endothelium, bloodstream
- this is where platelets pinch off the polyploid cell
Summarize thrombopoiesis
megakaryocyte extends cytoplasmic extensions (without nuclear components), from the bone marrow into the neighbouring blood vessels, where platelets are pinched off and enter the bloodstream
Although platelets (cytoplasmic components of megakaryocytes) have no nuclear component, what other cell components do they contain
mitochondria, smooth ER, and granules filled with clotting proteins/cytokines
What is the lifespan of a platelet
10 days
Are platelets always active?
they are always PRESENT in the bloodstream, but only ACTIVE when damage has occurred to the walls of the circulatory system
Inactivated platelets are ________ in shape, but activated platelets are ________
rounded and smooth = inactive
edges and misshaped = active
What is erythropoiesis
formation of RBCs
What regulates formation of RBCs
EPO (erythropoietin)
Is EPO a hormone or a cytokine
cytokine (often called a hormone but its not)
EPO is a ______________ made primarily in the _________
glycoprotein, made in the kidneys
What regulates EPO synthesis
hypoxia (low O2 content)
What is haemostasis
the process of keeping blood within a damaged area (opposite to a hemorrhage)
Why is haemostasis important
blood flow cannot be stopped or paused to stop a leak, therefore holes must be plugged under pressure to avoid bleeding out
What happens if the “patch” created by haemostasis is too weak
it falls off and blood flows
What are the 3 steps in haemostasis
- vascular spasm
- platelet plug to temporarily block
- blood clot to seal
(review figure shown in lecture recording March 7*)
What happens in step 1 of haemostasis (vascular spasm)
damaged endothelium releases vasoconstrictive paracrine that decreases blood flow and promotes the formation of a platelet plug
- similar to putting pressure on a bleeding wound
What happens in step 2 of haemostasis (formation of a platelet plug)
- damage to the epithelial layer of the blood vessel exposes collagen found in the sub-epithelial layer (usually not exposed to the lumen)
- exposure of collagen activates platelets (platelets stick to collagen and stick together)
- when platelets gather on collagen and begin sticking together, it forms a framework for clotting and creates the formation of a platelet plug
What happens in step 3 of haemostasis (blood clotting)
blood clots as a result of the coagulation cascade
Inactivated plasma proteins activated by exposure to either __________________________ or _______________________ released by damaged cells
- factor XII (12) collagen (intrinsic)
- factor III (3) collagen (extrinsic)
When should blood clotting NOT happen
when there is not damaged tissue
What starts the intrinsic pathway
collagen is exposed which activates tissue factor XII
What starts the extrinsic pathway
tissue damage activated tissue factor III
The intrinsic and extrinsic pathways come together to form _______________
thrombin
- eventually leads to cross-linked fibrin
What is the function of thrombin
cleaves fibrinogen (in the blood) into fibrin (important for blood clotting)
Thrombin activates factor ______
factor XIII (13)
What does factor 13 do to fibrin
- crosslinks it into long fibres that intertwine
- the intertwined fibres reinforce the platelet plug making it a clot
What occurs in excessive clotting
produces a thrombus; a clot which can BLOCK blood vessels
During healing, what happens to the clot
as repair progresses, the clot shrinks
What enzyme dissolves clots
plasmin
(this process is called fibrinolysis)
What is fibrinolysis
the dissolving of blood clots via enzyme
