2. PATH OF BLOOD FLOW
Scenario:
• You inject a medication into the client’s arm
• Within a few minutes, some of that drug has
reached the client’s liver and is being
deactivated
Question:
• How did it get there?
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3. SIMPLIFIED PATH OF BLOOD FLOW
right
heart
lungs
left
heart
body
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5. QUESTION
Tell whether the following statement is true or
false:
The pulmonary circulation moves blood
through the left side of the heart.
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6. ANSWER
False
The right side of the heart pumps blood to the
lungs through the pulmonary arteries, where
gas exchange takes place. The left side of the
heart is considered systemic circulation
because blood is pumped to all body tissues.
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8. THE BASICS OF CELL FIRING
• Cells begin with a
negative charge:
resting membrane
potential
• Stimulus causes
some Na+ channels
to open
• Na+ diffuses in,
making the cell
more positive
Threshold potential
Resting
membrane
potential
Stimulus
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9. THE BASICS OF CELL FIRING (CONT.)
• At threshold potential,
more Na+ channels
open
• Na+ rushes in, making
the cell very positive:
depolarization
• Action potential: the cell
responds (e.g., by
contracting)
Threshold potential
Resting
membrane
potential
Stimulus
Action potential
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10. THE BASICS OF CELL FIRING (CONT.)
• K+ channels open
• K+ diffuses out,
making the cell
negative again:
repolarization
• Na+/K+ ATPase
removes the Na+ from
the cell and pumps
the K+ back in
Threshold potential
Resting
membrane
potential
Stimulus
Action potential
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11. CARDIAC CELL FIRING
• Cells begin with a negative
charge: resting membrane
potential
• Calcium leak lets Ca2+
diffuse in, making the cell
more positive
Threshold potential
Resting
membrane
potential
Calcium leak
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12. CARDIAC MUSCLE FIRING (CONT.)
• At threshold potential,
more Na+ channels
open
• Na+ rushes in, making
the cell very positive:
depolarization
• Action potential: the
cell responds (e.g., by
contracting)
Threshold potential
Resting
membrane
potential
Action potential
Calcium leak
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13. CARDIAC MUSCLE FIRING (CONT.)
• K+ channels open
• K+ diffuses out, making
the cell negative again,
but Ca2+ channels are
still allowing Ca2+ to
enter
• The cell remains
positive: plateau
Threshold potential
PLATEAU
Action potential
Calcium leak
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14. CARDIAC MUSCLE FIRING (CONT.)
• During plateau,
the muscle
contracts
strongly
• Then the Ca2+
channels shut
and it repolarizes
Threshold potential
PLATEAU
Action potential
Calcium leak
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15. QUESTION
Which ion channels allow cardiac muscle to
fire without a stimulus?
a. Na+
b. K+
c. Ca2+
d. Cl-
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16. ANSWER
c. Ca2+
In the S-A node and A-V node, resting cardiac
muscle cells have open Ca2+ channels. This
allows Ca2+ to leak into the cells, making them
more positive (the cells reach threshold this
way without the need for a stimulus).
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18. HEART CONTRACTION
How would each of the following affect heart
contraction:
• A calcium-channel blocker
• A Na+ channel blocker
• A drug that opened Na+ channels
• A drug that opened K+ channels
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19. CARDIAC CYCLE—DIASTOLE
• Ventricles relaxed
• Blood entering atria
• Blood flows through AV valves into
ventricles
• Semilunar valves are closed
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22. CARDIAC CYCLE—SYSTOLE
• Ventricles contract
• Blood pushes against AV valves and they shut
• Blood pushes through semilunar valves into
aorta and pulmonary trunk
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23. QUESTION
Which of the following statements is true
about ventricular systole?
a. Atria contract
b. Ventricles contract
c. AV valves are open
d. Semilunar valves are closed
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24. ANSWER
b. Ventricles contract
During ventricular systole, the ventricles
contract. Because blood is being forced from
the ventricle, semilunar valves must be open
and AV valves, closed. The atria is in diastole
(relaxation) during ventricular systole.
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25. CARDIAC CYCLE
Discussion:
• Arrange these steps in the proper order:
– Ventricles relax – First heart sound
– Systole – Semilunar valves open
– Diastole – AV valves close
– AV valves open – Semilunar valves close
– Ventricles contract – Second heart sound
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26. PRESSURE, RESISTANCE, FLOW
• Fluid flow through a vessel depends on:
– The pressure difference between ends of the vessel
• Pressure pushes the fluid through
• Pressure keeps the vessel from collapsing
– The vessel’s resistance to fluid flow
• Small vessels have more resistance
• More viscous fluids have greater resistance
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27. PRESSURE, RESISTANCE, FLOW OF
BLOOD
• Blood flow through a vessel depends on:
– Heart creating pressure difference between ends
of the vessel
• Heart pushing the blood through
• Blood pressure keeping the vessels open
– The vessel’s resistance to fluid flow
• Constricting arterioles increasing resistance
• Increased hematocrit increasing resistance
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28. DISCUSSION
How will each of these factors affect
arteriole size and peripheral resistance?
• Lactic acid • Low PO2
• Cold • Histamine
• Endothelin • Heat
• NO • Adenosine
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29. BLOOD PRESSURE
• BP = CO x PR
• Blood Pressure = Cardiac Output × Peripheral
Resistance
• CO = SV X HR
• In healthy adult
– Highest pressure(systolic)- < 120 mmHg
– Lowest pressure (diastolic) < 80 mmHg
• Difference between systolic and diastolic
pressure = pulse pressure
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30. REGULATION OF BP
Short term regulation of BP relies on neural and
hormonal mechanisms
A) Neural centers are located in the reticular
formation of lower pons and medulla of the
brain
• Area also called cardiovascular center
• ANS control of BP is mediated by intrinsic
circulatory reflexes, extrinsic reflexes, and higher
neural control centers
• Intrinsic mechanism involves Baroreceptors and
chemoreceptors
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31. REGULATION OF BP CON’T
• Baroreceptors
– Pressure sensitive receptors
– Located in the walls of blood vessels and heart
– Carotid & aortic baroreceptors are located in
strategically
– Send impulse to the cardiovascular centers
• Arterial chemoreceptors
– Sensitive to changes in oxygen, Carbondioxide, and
Hydrogen ion content of blood
– Located in carotid and aortic bodies
– Can also induce widespread vasoconstriction
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32. HORMONAL MECHANISMS
• Involves: renin- angiotensin- aldosterone mechanism,
Vasopressin, epinephrine
• Renin
– An enzyme found in the juxtaglomerula cells of the kidneys
– Released in blood where it converts
angiotensinogen(plasma protein) to angiotensin I
– Angiotensin I is converted to angiotensin II in the lungs by
Angiotensin Converting Enzyme (ACE) present in the
endothelium of the lung vessels
– Angiotensin II :
• Is a strong vasoconstrictor (arterioles and Veins)
• Stimulates aldosterone secretion from adrenal (cortex) gland
bringing about Na/water retention by kidneys
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33. VASOPRESSIN
• Released from the posterior pituitary gland in
response to decreased blood volume and BP,
increased osmolality of body fluids
• Has vasoconstrictor effect on blood vessels
especially those of the planchnic circulation
that supplies the abdominal viscera
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34. HYPERSTENSION
• Classified into Primary (essential) and
secondary hypertension
• Essential is the most common accounting for
90-95% of HT cases
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BP classification Systolic BP(mmHg) Diastolic BP (mmHg)
Normal < 120 And < 80
Pre-hypertension 120 – 139 And 80 – 89
Stage 1 Hypertension 140 – 149 And 90 - 99
Stage 2 Hypertension ≥ 160 ≥ 100
35. RISK FACTORS FOR HT
• Family history, race, age related increase
• Life style
– High sodium intake, excessive calorie intake and
obesity, physical inactivity, excessive alcohol intake
• Oral contraceptives
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36. MANIFESTATION
• Target organ damage affecting the following organs
• Heart
– Left ventricular hypertrophy
– Angina or prior myocardial infarction
– Prior coronary revascularization
– Heart failure
• Brain
– Stroke or transient ischemic attack
• Chronic kidney disease
• Peripheral vascular disease
• Retinopathy
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37. DIAGNOSIS
• Repeated BP measurement
• BP measurement should be taken when the
person is relaxed and has rested for at least 5
minutes and had not smoked or taken caffein
within 30 minutes
• Pharmacological treatment based on:
– severity of disease
– Presence of target organ disease
– Existence of other conditions and risk factors
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39. SECONDARY HYPERTENSION
• Most common causes are: Kidney disease,
adrenocortical disorder, phenochromocytoma,
coarctation of the aorta, drugs such as cocaine
• HT arising from kidney disease is usually a result of:
– Acute glomerulonephrites
– Acute renal failure
– End stage renal disease
• 80% of patients with Chronic renal failure have HT
• Most acute kidney disorders result in decreased urine
formation, retension of water & Na and HT
• Reduced renal blood flow causes the affected kidney
to release excess amounts of renin
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40. ORTHOSTATIC HYPERTENSION
• Read about its causes and management
• Also read about venous thrombosis especially
Deep Vein Thrombosis( DVT)
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41. QUESTION
Tell whether the following statements is true
or false:
In patients with hypertension (high blood
pressure), peripheral resistance is increased.
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42. ANSWER
True
In hypertension, blood vessels are
constricted/narrowed. Smaller vessels
increase resistance (it’s harder to push the
same amount of fluid/blood through a tube
that has become smaller).
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