Chapter 20: Vessels & Circulation Flashcards Preview

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Flashcards in Chapter 20: Vessels & Circulation Deck (69):
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Capillaries:

Exchange of gas, nutrients, wastes, & hormones through diffusion. Usually pinocytosis.

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Bulk flow

Movement of large volumes of H2O & Solutes by osmosis but also by physical force on blood vessels

2 types: filtration & diffusion

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Filtration:

Bulk flow out of a blood vessel at origin or start of a capillary (near arteries)

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Reabsorption:

Bulk flow into a blood vessel towards end of capillary

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Bulk flow is determined by:

1) Hydrostatic Pressure

2) Interstitial Pressure

3) Colloid Osmotic Pressure

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Hydrostatic Pressure:

Physical pressure of fluid on its structure

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Interstitial Pressure:

Hydrostatic pressure of the interstitial fluid on the exterior of the blood vessel

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Colloid Osmotic Pressure:

Pressure due to the movement of water. Which is determined by the amount of dissolved substances in the fluid (especially protein concentration)

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Types of colloid pressure:

1) blood colloid osmotic pressure

2) interstitial colloid osmotic pressure

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Blood colloid osmotic pressure:

*lots of dissolved substances (esp. Proteins)

*opposite direction to the blood pressure

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Interstitial colloid blood pressure:

Few proteins, very low

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Net filtration pressure:

Difference in hydrostatic pressure & colloid osmotic pressure.

Determines filtration direction & quantity

NFP= (HPb + HPif) - (COPb-COPif)

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Difference in hydrostatic pressure =

BP-IP

Ip is always very low=0

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Difference in colloid osmotic pressure =

Bloop Cop - Interstitial Cop

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If Net filtration pressure is +

= Filtration

Fluid moving out of blood vessels

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If net filtration pressure is -

=reabsorption

Fluid moving into blood vessels

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Difference in hydrostatic pressure of Arterial end of capillary:

*BP = 35 mm of Hg (mercury)
-
*IP = 0 mm of Hg (mercury)

Difference in hydrostatic pressure (HP) =35

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Arterial end of capillary is:

Hypothetical because these values change depending on age & distance from Heart Rest vs. Active

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Difference in colloid osmotic pressure at Arterial end of capillary:

*Blood colloid osmotic pressure = 26mm Hg
-
*Interstitial colloid osmotic pressure= 5 mm Hg

Difference in colloid osmotic pressure (cop) = 21 mm Hg

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At Venous End of Capillary:

Blood moves from one end of the capillary to the other end

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Net filtration at venous end of capillary:

*Difference in HP
BP=16 mm Hg
IP= 0mm Hg
16-0=16

*Difference in colloid osmotic pressure
BP=26 mm Hg
IP= 5 mm Hg
26-5=21

16-21=-5 mm Hg

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How many miles of blood vessels?

600,000 miles of BV

We don't have enough blood to fill all BV so body controls blood flow to areas that need it the most.

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Local blood flow

Blood that is delivered to a specific region

Measured by perfusion

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Goal of CV system:

Adequate perfusion for all tissues

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Degree of vascularization

Amount of blood vessels in a given tissue

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Angiogenesis

Process in which the body grows new blood vessels

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Regression

Process by which the body disassembles unneeded blood vessels

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Local regulator factors that alter blood flow:

Vasoactive chemicals

1)vasodilators
2)vasoconstrictors

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Vasodilators:

Dilate arterioles and relax precapillary sphincters

1)nitric oxide

2)elevated levels of carbon dioxide, H+/acidity of blood, K+

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Vasoconstrictors:

Constrict arterioles and close precapillary sphincters

1)prostaglandins & thromboxanes
-we've seen in action during hemostasis

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Blood pressure:

Force per unit area of blood on wall of BV

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Blood pressure gradient:

Difference in BP from 1 end of BV to the other

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Total blood flow resting:

= 5.25 L/min

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Arterial blood pressure:

Blood flow is pulsing in arteries due to ventricular contractions

Average in healthy individual = 120/80 mm Hg

Highest at ventricular systole, arteries are stretched = systolic pressure

Lowest at ventricular diastole, arteries recoil = diastolic pressure

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Systolic pressure

Arteries are stretched

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Diastolic pressure

Arteries recoil

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Pulse pressure:

The additional pressure on arteries when the heart is resting vs contracting

Measures elasticity and recoil of arteries

SP-DP =120-80 = 40 mm Hg

Highest closest to the heart

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High pulse pressure:

Means arteries are not elastic, not stretching due to atherosclerosis (clogging of arteries)

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Mean arterial pressure (MAP)

DP + PP/3

Describes how well the body is perfused. Need MAP of 70-110 mm Hg

Highest closest to the heart

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If Mean arterial pressure (MAP) is too high/low:

Too much perfusion= edema & kidney damage

Too low perfusion= inadequate perfusion

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Capillary blood pressure:

By the time blood reaches the capillaries--not pulsatile, no fluctuations between systole & diastole

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Capillary Blood pressure at arterial & venous ends:

Arterial end: 40 mm Hg

Venous end: 20 mm Hg

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Venous blood pressure:

*not pulsatile

*20 mm Hg in venules & 0 mm Hg in veins

(BP is insufficient to move blood when standing--need valves in veins)

* has two pumps that move blood in veins:
1)skeletal muscle pumps in limbs
2)respiratory pump in thoracic cavity

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Skeletal muscle pump

* in the limbs

*as muscles contract, they squeeze the blood up the veins while valves prevent back flow

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Respiratory pump:

*in thoracic cavity

*diaphragm contracts and relaxes increasing and decreasing pressure in both major ventral cavities

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Resistance:

The amount of friction the blood most overcome as it travels through the blood vessels

*opposes blood flow

*peripheral resistance--in BV not heart

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Factors affecting resistance:

1)blood viscosity

2)blood vessel length

3)vessel radius

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Blood viscosity:

Thickness of blood due to formed elements and plasma proteins.

*Thicker= more friction

*caused by Anemia, dehydration

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Blood vessel Length

*obesity creates need for longer vessels

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Vessel Radius

*narrower vessels have more friction

*in terms of friction:
arteries < arterioles < capillaries
--vasoconstriction/vasodilation can change that

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5 ways of neural regulation of blood pressure:

CV center of Medulla Oblongota

1)cardiac center

2)Vasomotor center

3)Baroreceptors

4)Chemoreceptors

5)High Brain Centers

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Cardiac Center:

speeds up/slows down HR and strength of contraction
*cardioaccelatory center
*cardioinhibatory center

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Cardioaccelatory Center:

Sympathetic pathways to SA node and myocardium

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Cardioinhibitory Center:

Parasympathetic pathways to SA node and AV node

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Vasomotor Center

Sympathetic pathways release E & NE

Which causes vasodilation in skeletal muscle & coronary vessels

Which caused vasoconstriction in most of the body ESPECIALLY in veins

Which causes:

1)increased peripheral resistance raises BP
2)larger circulating blood (shunted away by
most of the body)

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Baroreceptors:

Dendrites in tunica Externa that detects stretch in BV.

The firing rate increases when stretch increases (and vice versa)

1)in aorta to detect systematic BP
*send info back to CV center through vagus
nerve

2)in carotid to detect BP in head and neck
*send info back to CV through glossy
pharyngeal nerve

Low BP: more sympathetic signals increases
hearts contraction rate & strength

High BP: fewer parasympathetic signals
decrease info to more sympathetic
signals to increase vasoconstriction/
peripheral resistance

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Chemoreceptors

Detect high C02, low PH, and very low 02;both activate vasoconstriction

1)Aortic bodies in Aorta

2)Carotid body in Carotid Arteries

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Higher Brain Centers

Hypothalamus increased BT, exercise

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Hormonal regulation of blood pressure:

1)Renin-Angiotensin system

2)Atrial Natriuretic Peptide

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Renin-angiotensin system:

Low BP sensed by kidney or sympathetic stimulation

Kidneys release renin enzyme into blood

Renin converts angiotensinogen in blood to angiogenesin I.

Angiotensin I travels to the lung via blood

Angiotensin converting enzyme (ACE) mostly in lungs converts angiotensin I to angiotensin II.

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Angiotensin II's effects/jobs:

1)powerful vasoconstrictor

2)stimulates thirst center

3)decreases urine output

4)signals release of aldosterone from adrenal cortex or anti diuretic hormone from posterior pituitary

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Aldosterone:

Increase absorption of Na & water in the kidney reducing fluid losses to maintain pressure

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Antidiuretic Hormone:

Hypothalamus detects, signals pituitary to release

increases water absorption in the kidney

Also stimulates thirst center

Can also cause vasoconstriction in large doses

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Atrial Natriuretic Peptide:

Released from the heart if too much stretch in walls of heart

Stimulates vasodilation

Increases urine output

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Baroceptor in Aorta:

detects systematic BP

*send info back to CV center through vagus
nerve

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Baroreceptor in carotid:

Detects BP in head and neck

* sends info back to CV through
glossopharyngeal nerve

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Low BP baroreceptor

More sympathetic signals increases hearts contraction rate & strength

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High BP baroreceptor

Fewer parasympathetic signals decrease info to more sympathetic signals to increase vasoconstriction/ peripheral resistance

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Blood hydrostatic pressure (BP)

hydrostatic pressure of the blood on the
interior wall of the blood vessel