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Anatomy and Physiology > blood vessels ii > Flashcards

blood vessels ii Flashcards

1
Q

cardiac output

A

CO = SV * HR

  • normal = 5-5.5 L/min
  • determined by venous return and neural/hormonal controls
  • resting heart rate maintained by cardioinhibitory center via parasympathetic vagus nerves
  • during stress, cardioacceleratory center increases heart rate and stroke volume via sympathetic stimulation (ESV decreases and MAP increases)
  • stroke volume controlled by venous return (EDV)
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2
Q

short term vs long term control of BP

A

Short
-neural and hormonal controls –> counteract fluctuations in BP by altering peripheral resistance and CO

Long
-renal regulation –> counteracts fluctuations in blood pressure by altering blood volume

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3
Q

Neural controls for short term BP maintanence

A
  • if low BP, vessels constrict except those to heart and brain (affects MAP)
  • alter blood distribution to organs in response to specific demands

Neural controls operate via reflex arcs, involving: baroreceptors, cardiovascular center of medulla, vasomotor fibers to heart and vascular smooth muscle, sometimes chemoreceptors and higher brain centers

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4
Q

CV center

A
  • clusters of sympathetic neurons in medulla oversee changes in CO and blood vessel diameter
  • consists of cardiac centers and vasomotor center
  • Vasomotor center sends steady impulses via sympathetic efferents to blood vessels –> moderate constriction called vasomotor tone
  • recieves input from baroreceptors, chemoreceptors, and higher brain centers
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5
Q

Baroreceptors

  • location
  • response to increased BP
A

-located in carotid sinuses, aortic arch, and walls of large arteries in neck/thorax

increased BP stimulates baroreceptors to increase input to vasomotor center

  • inhibts vasomotor and cardioacceleratory centers, causing arteriolar dilation and venodilation
  • stimulates cardioinhibitory center
  • decreases BP
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6
Q

Baroreceptor

  • response to decreased BP
  • example
A
  • Reflex vasoconstriction –> increased CO –> increased BP
  • when you stand, baroreceptors of carotid sinus reflex protect blood to brain; in systemic circuit as whole, aortic reflex maintains BP
  • Baroreceptors don’t do shit if altered blood pressure is sustained
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7
Q

Chemoreceptor reflexes (short term BP maintenance)

  • location
  • how the alter BP
A
  • in aortic arch and large arteries of neck
  • detect increase in CO2 of drop in pH/O2
  • Increased BP by signaling cardioacceleratory center to increase CO; or signaling casomotor center to increase vasoconstriction
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8
Q

Higher Brain Centers (short term maintenance of BP)
-where?
how?

A
  • reflexes in medulla
  • hypothalamus and cerebral cortex can modify arterial pressure via relays to medulla
  • hypothalamus increases BP during stress
  • Hypothalamus mediates redistribution of blood flow during exercise and changes in body temp
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9
Q 
Hormonal control (short term BP maintenance)
-how?!?!?!?!?
A

Cause increased BP

  • epinephrine and norepinephrine from adrenal gland –> increased CO and vasoconstriction
  • angiotensin II stimulates vasoconstriction
  • High ADH causes vasoconstriction

Cause lowered BP
-ANP causes decreased blood volume by antagonizing aldosterone

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10
Q

Renal regulation (long term BP maintenance)

  • why kidneys?
  • 2 methods
A
  • baroreceptors quickly adapt to chronic high or low BP so they’re ineffective
  • long term mechanisms control BP by altering blood volume via kidneys

Kidneys regulate arterial blood pressure:

  1. direct renal mechanism
  2. indirect renal (RAA) mechanism
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11
Q

Direct Renal mechanism

A

alters blood volume independently of hormones

  • increased BP or blood volume causes elimination of more urine, reducing BP
  • Decreased BP or blood volume causes kidneys to conserve water, and BP rises
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12
Q

Indirect Renal Mechanism

A

The RAA mechanism

  • low arterial BP causes kineys to release renine
  • Renin changes angiotensinogen into angiotensin I
  • ACE from lungs turnse angiotensin I into angiotensin II
  • Angiotensin II causes vasoconstriction and the release of aldosterone and ADH; and triggers thirst
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13
Q

Monitoring Circulatory efficiency

A
  1. vital signs: pulse, BP, respiratory rate, body temp
  2. Pulse: pressure wave caused by expansion and recoil of arteries
  3. radial pulse: @ wrist- routinely used
  4. Pressure points where arteries are close to body surface (can be compressed to stop blood flow)
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14
Q

Measuring systemic arterial BP

A
  • auscultatory method uses a sphygmomanometer
  • pressure increased in cuff until it exceeds systolic pressure in brachial artery
  • pressure released slowly and examiner listens for sounds of Korotkoff with a stethoscope
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15
Q

systolic pressure vs Diasolic pressure (when measuring BP)

A

Systolic: usually less than 120 mm Hg and is the first sound as blood starts to spurt through artery

Diastolic: usually less than 80 mm Hg and is last sound before artery is no longer constricted

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16
Q

what causes variation in BP?

A
  • transient elevations occur during changes in posture, physical exertion, emotional upset, and fever
  • age, sex, weight, race, mood, and posture also alter BP
17
Q

Hypertension and pre hypertension

A

Hypertension = high BP
-sustained arterial pressure of 140/90 or higher (some ppl use 135/85)

Prehypertension = elevated values, but not in hypertension range

  • may be transient adaptations
  • often persist in obese ppl
18
Q

What’s wrong with prolonged hypertension?

A
  • can cause heart failure, vascular disease, renal failure, and stroke
  • heart must work harder –> myocardium enlarges, weakens, and becomes flabby
  • also accelerates atherosclerosis
19
Q

Primary/ Essential Hypertension

A
  • 90% of hypertensive conditions
  • No underlying cause identified (risks = heredity, diet, obesity, age, diabetes mellitus, stress, and smoking)

-no cure, but can be controlled (reduce salt, fat, and cholesterol intake; increase exercise, lose weight, stop smoking; antihypertensive drugs)

20
Q

Secondary Hypertension

A
  • less common
  • due to identifiable disorders including obstructed renal arteries, kidney disease, and endocrine disorders (e.g. hyperthyroidism and Cushing’s syndrome)

-Treatment focuses on correcting underlying cause

21
Q

Hypotension

A
  • low BP
  • Blood pressure below 90/60 mm Hg
  • Usually not a concern unless it leads to inadequate blood flow to tissues
  • often associated with long life and lack of cardiovascular illness
22
Q

Tissue perfusion

A
  • Delivery of O2 and nutrients to and removal of wastes from tissue cells
  • gas exchange in lungs
  • absorption of nutrients (digestion)
  • urine formation (kidneys)

-Rate of Blood flow is just right to provide proper func.

23
Q

velocity of blood flow

A
  • changes as it travels through systemic circulation
  • inversely related to total cross-sectional area
  • fastest in aorta; slowest in capillaries; increases in veins
  • slow capillary flow allows adequate time for exchange bt blood and tissues
24
Q

Autoregulation

  • what is it?
  • how is it controlled?
  • is it associated with MAP
A
  • automatic adjustment of blood flow to each tissue relative to its varying requirements
  • controlled intrinsically by modifying diameter of local arterioles feeding capillaries (independent of MAP which is controlled as needed to maintain BP)
  • organs regulate own blood flow by varying resistance of own arterioles
25
Q

2 types of autoregulation

A

metabolic controls

myogenic controls

26
Q

Metabolic Autoregulation Controls

  • what does it do
  • what triggers it
  • what do endothelins have to do with all this?
A

-vasodilation of smooth muscle in arterioles and precapillary sphincters; release of NO and/or inflammatory chems (vasodilators) from endothelial cells

occur in response to:

  1. declining tissue O2
  2. Substances from metabolically active tissues (H+, K+, adenosine, and prostaglandins) and inflammatory chemicals

Endothelins are vasoconstrictors which are usually balanced with NO, but if blood flow is inadequate, NO wins

27
Q

Myogenic Autoregulation Controls

A

-Myogenic responses keep tissue perfusion constant depite most fluctuations in system pressure

  • vascular smooth muscle responds to stretch:
    1. Passive stretch (more intravascular pressure) promotes increased tone and vasoconstriction
    2. Reduced stretch promotes vasodilation and increases blood flow to the tissue
28
Q

long term autoregulation

A

-occurs when short term autoregulation can’t meet tissue nutritient needs

Angiogenesis

  • # of vessels to region increases and existing vessels enlarge
  • common in heart when coronary vessel occluded, or throughout body in people in high-altitude areas
29
Q

3 types of movement of substances between blood in capillary and interstitial fluid

A

diffusion
transcytosis
bulk flow

30
Q

Diffusion

A
  • most important one
  • substances move down concentration gradient (O2 and CO2)
  • Get to/from capillary thru intracellular clefts, fenestrations, or through endothelial cells

Most plasma proteins cant cross except in sinusoids
BBB is supre tight

31
Q

Transcytosis

A
  • small quantity of material
  • substances in blood plasma get pinocytized and/or leave via exocytosis
  • important for large, lipid insoluble molecules that can’t get thru any other way
32
Q

Bulk flow

A
  • passice process in which larges of ions, molecules, or particles in a fluid move together in the same direction
  • based on pressure gradient
  • diffusion is more important for solute exchange
  • bulk flow is important for regulation of relative volumes of blood and interstitial fluid
  • filtration = from capillaries into interstitial fluid
  • reabsorption = from intersitial fluid into capillaries
33
Q

Net filtration pressure

  • formula
  • components
A

-balance of 2 pressures which promote filtration:
NFP = (BHP + IFOP) - (BCOP + IFHP)

Filtration:

  • blood hydrostatic pressure (BHP) generated by pumping of heart (falls over capillary bed from 35-16 mmHg)
  • Interstitial fluid osmotic pressure (IFOP) 1 mmHg

Reabsorption

  • Blood colloid osmotic pressure (BCOP) about 36 mmHg bc blood plasma porteins wanna cross walls
  • Interstitial fluid hydrostatic pressure (IFHP) close to 0 mmHg
34
Q

Pressure at arterial end vs venous end?
How much of the fluid that’s filtered is reabsorbed?
What happens to the rest?

A

10 mmHg vs -9 mmHg
85%
-it enters lymphatic capillaries (3 L/day) and is eventually returned to blood

35
Q

Vasomotion

A
  • slow, intermittent flow

- reflects on/off opening and closing of precapillary sphincters

36
Q

Capillary exchange of respiratory gases and nutrients

A
  • diffusion down concentration gradients (O2 and CO2)
  • lipid solubles diffuse
  • water soluble pass through clefts and pores
  • Big molecules (prots) are actively transported via pinocytosis or caveolae (lipid raft)
37
Q

Blood flow in lungs

-autoregulatory mechanisms here

A

Pulmonary circuit

  • short path
  • arteries are more like veins (thin walls; big lumens)
  • arterial resistance and pressure are low (24/10 mmHg)
  • Autoregulatory mechanism opposite that in most tissues (low O2 causes vasoconstriction and vice versa)
38
Q

Circulatory shock

A
  • any condition in which blood vessels inadequately filled or blood can’t circulate normally
  • results in inadequate blood flow to meet tissue need
39
Q

Types of Circulatory shock

A

Hypovolemic shock - results from large scale blood loss

Vascular shock - results from extreme vasodilation and decreased peripheral resistance (allergies)

Cardiogenic shock - results when an inefficient heart can’t sustain adequate circulation (pump failure)

Anatomy and Physiology (50 decks)

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