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Physiology > Chapter 15 > Flashcards

Chapter 15 Flashcards

1
Q

What is the equation for blood pressure?

A

Blood Pressure = Cardiac Output x Resistance (in arteries)

BP = CO x R(arteries)

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2
Q

What is Poisevilles Law? What is the complex formula? What are the easy equations?

A

the velocity of the steady flow of a fluid through a narrow tube (as a blood vessel or a catheter) varies directly as the pressure and the fourth power of the radius of the tube and inversely as the length of the tube and the coefficient of viscosity.
Complex: Flow = deltaP x r4 x pi / 8 x L x R
Easy: Flow = deltpP x r4 / L x R , Flow = deltaP / R

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3
Q

When considering all of the vessels in the vascular system, which vessels contribute most to the total resistance?

A

arterioles

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4
Q

Define shock. Explain why shock is dangerous. List three types of shock. For each explain how shock is generated.

A

Shock - decrease in cardiac output which results in inadequate tissue perfusion.

  1. cardiogenic - shock due to infarct (heart attack) cell death to parts of the heart - decrease contractility
  2. hypovoemic - shock due to bleeding (low blood volume) dehydration (burns)
  3. septic (sepsis) - shock due to infection = blood poisoning; bacteria in body cavity… vasodialation causes decrease in BP which increases the permeability of venules which results in excess plasma leakage.
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5
Q

In shock the compensatory mechanisms are failing to maintain homeostasis. What are the mechanisms that are failing? in other words, describe the mechanisms the body has to counteract shock.

A 
The sympathetic nervous system:
- increases HR
- increases contractility
- increases vasoconstriction
- increases venous return
(can also decrease the parasympathetic NS)
ALL OF WHICH INCREASE BP
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6
Q

Angiotensin II: What is its major and direct effect on the circulation?

A

very powerful vasoconstrictor that is present when BP is low. (increase BP = CO x increased R (arteries)

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7
Q

Explain the myogenic mechanism in arterioles. Explain why it is significant.

A

An intrinsic local control over the vasoconstriction and vasodialation of arterioles in response to a sudden increase or decrease in pressure.
Maintains normal flow as we are constantly moving and pressure in our vessels is changing.

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8
Q

Explain how blood flow through capillaries is regulated.

A

Regulated by paracrines which are signaling molecules that only work locally. Cells near an arteriole or pre-capillary sphincter release chemical signals.

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9
Q

the specific branch of the nervous system that controls most blood vessels is the what?

A

Sympathetic NS

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10
Q

What neurotransmitter does the sympathetic NS generally release to control blood vessels?

A

norepinephrine

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11
Q

What is the response of the blood vessels if more norepinephrine is released by the sympathetic NS?

A

vasoconstriction

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12
Q

What is the response of the blood vessels if less norepinephrine is released by the sympathetic NS?

A

vasodialation

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13
Q

List each component of the Baroreceptor reflex. Describe the role that each plays in the reflex.

A
  1. Stimulus - change in BP
  2. Sensor - baroreceptor (aortic sinus, carotid sinus - increase stretch = increase AP, decrease stretch = decrease AP)
  3. Sensory input - sensory neurons (vagus nerve)
  4. Integrating Centers - Medulla = setpoint for BP; Cardiac Center = HR contractility; vasomotor center = vessel tone (vasoconstrict0
  5. Motor output - parasympathetic neurons: HR vagus nerve; sympathetic neurons: HR, contractility, vessel tone
  6. Effectors - SA Node, myocardium, smooth muscle in vessels
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14
Q

What happens to blood pressure immediately upon standing up from a prone position? Explain how the body compensates. What is this phenomenon called?

A

there’s a sudden increase in BP.
The parasympathetic NS responds to decrease it.
Orthostatic Hypertension

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15
Q

What happens to blood pressure immediately upon lying down from a standing position? Explain how the body compensates.

A

there’s a sudden decrease in BP.

the sympathetic NS responds to increase it.

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16
Q

Explain the mechanism of cardiogenic shock using a cause and effect argument.

A

Infarct (heart attack) causes cell death decreasing contractility which decreases SV which decreases CO which ultimately decreases your BP

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17
Q

Explain the mechanism of hypovolemic shock using a cause and effect argument.

A

Bleeding or dehydration cause low blood volume which decreases venous return which decreases EDV which decreases stretch which decreases contractility which decreases SV which decreases CO which decreases BP.

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18
Q

Explain the mechanism of septic shock using a cause and effect argument.

A

Bacteria in body cavity results in toxins that cause vasodialation which decreases blood volume which decreases venous return which decreases EDV which decreases stretch which decreases contractility which decreases SV which decreases CO which decreases BP

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19
Q

Define filtration as it relates to capillaries. Why does filtration occur?

A

The movement of water and small molecules from the capillary in response to the difference in pressure. Filters about 20 L/day

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20
Q

The hydrostatic pressure of the blood at the beginning of a continuous capillary is about what? at the end?

A

beginning: 32 mmHg
end: 16 mmHg

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21
Q

The gaps between adjacent endothelial cells in capillaries are called what? What can and cannot pass through?

A

Clefts
CAN: fluid, small molecules, ions and nutrients
CANNOT: formed elements (plasma proteins cannot pass) - albumin, fibrinogen, globins, gammaglobins

22
Q

the process by which interstitial fluid is returned to the blood at capillaries is called what? How much is reabsorbed? Where is the remainder absorbed?

A

Reabsorption
90% which is ~ 18 L/day reabsorbed into capillaries
~2L/day is reabsorbed by the lymphatic system

23
Q

What is oncotic pressure? How does it operate?

A

form of osmotic pressure exerted by proteins, notably albumin, in a blood vessel’s plasma (blood/liquid) that usually tends to pull water into the circulatory system.
~25mmHg

24
Q

the most important plasma protein responsible for colloid oncotic pressure is what? Why?

A

Albumin because it is the most common

25
Q

Define edema.

A

accumulation of interstitial fluid in the tissue.

26
Q

using cause and effect arguments, explain how right heart failure causes edema.

A

excess venous blood causes extra pressure in capillaries. Increase in hydrostatic pressure increases filtration and decreases absorption.

27
Q

using cause and effect arguments, explain how liver failure causes edema.

A

decrease in plasma proteins which aids in reabsorption so causes a decrease in reabsorption

28
Q

using cause and effect arguments, explain how histamines cause edema.

A

increases the diameter of intercelular clefts which allow plasma proteins into the interstitial fluid which decreases reabsorption.

29
Q

Describe the effect of vessel radius on blood flow. What is the mechanism that explains this effect?

A

vasodialation/vasoconstriction - the larger the radius, the more laminar flow which increases blood flow

30
Q

What is the primary component in blood that affects its viscosity?

A

Red Blood Cells

31
Q

Describe the effect of vessel length on blood flow. What is the mechanism that explains this effect?

A

Increase length = decrease blood flow

Bainbridge reflex?

32
Q

Describe the effect of blood pressure on blood flow. Explain why pressure changes are probably not the best way to control flow.

A

Blood always flows from High to low pressure. If we used pressure to maintain blood flow than when lay down there would be no flow, when we raise our hand it would lose blood flow and when we stood up all our blood would run to our feet.

33
Q

Describe the intrinsic mechanism that the heart uses to increase stroke volume.

A

The sympathetic NS causes vasoconstriction which increases venous return which increases contractility which in turn increases stroke volume.

34
Q

What does TV stand for? What does it mean? What is the typical value?

A

Tidal Volume - the volume of air in a normal quiet breath

~500mL

35
Q

What does IRV stand for? What does it mean? What is the typical value?

A

Inspiratory Reserve Volume - the volume of additional air that can be inspired following a tidal inspiration.
(~3,000mL)

36
Q

What does ERV stand for? What does it mean? What is the typical value?

A

Expiratory Reserve Volume - The volume of additional air that can be expired following a tidal expiration
(~1L)

37
Q

What does RV stand for? What does it mean?

A

Residual Volume - the volume of air that remains in lungs after an ERV

38
Q

What does VC stand for? What does it mean? What is the typical value?

A

Vital Capacity - the maximum volume of air that can be moved. (~5L)

39
Q

How can you calculate VC?

A

VC = IRV + TV + ERV

40
Q

What does TLC stand for? What does it mean? What is the typical value?

A

Total Lung Capacity - the maximum volume of air that can be in the lungs. (~6L)

41
Q

What does FEV1 stand for? What does it mean? What is the typical value?

A

Forced Expiratory Volume - percent of vital capacity (VC) expired in first second of forced expiration. (75% or better)

42
Q

Explain why a person having an acute asthma attack would score a low value with the FEV1 test.

A

blocked bronchioles - increase resistance = decrease flow rate

43
Q

Explain the role of surfactant in the lungs. Explain why it is significant.

A

Surfactant lowers the surface tension in order to increase flow rate.

44
Q

If a lung is punctured or the pleural cavity is punctured, air enters the pleural cavity causing what?

A

a collapsed lung.

45
Q

What is emphysema?

A

loss of lung elasticity

46
Q

What instrument is used to measure respiratory volumes and capacities?

A

spirometry

47
Q

Explain the mechanism of quiet inspiration. Explain the mechanism of quiet expiration.

A

Quiet inspiration - Contraction of the diaphragm and external intercostal muscles increases the thoracic lung volume
Quiet expiration - relaxation of the diaphragm and external intercostals plus elastic recoil of lungs decreases lung volume

48
Q

Explain the mechanism of forced inspiration. Explain the mechanism of forced expiration.

A

Forced inspiration - contraction of accessory muscles such as the scalenes and sternocleidomastoid
Forced expiration - contraction of abdominal muscles and internal intercostal muscles.

49
Q

What class of disorder does a low FEV1 value indicate?

A

Obstructive pulmonary disorder such as Asthma, chronic bronchitis or emphysema

50
Q

What class of disorder does a low VC value indicate?

A

Restrictive lung disorder such as pulmonary fibrosis

Physiology (25 decks)

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