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BIOL 2302 Anatomy & Physiology II > CH. 19: Circulation and Blood Pressure > Flashcards

CH. 19: Circulation and Blood Pressure Flashcards

1
Q

What is the general structure of blood vessels?

A

This is a shared structure of arteries and veins

Composed of three layers (tunics) that vary between vessel types:
-Tunica intima
-Tunica media
-Tunica external

The inner space of the vessel is called a lumen

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2
Q

What is tunica intima?

A

It is the “inside” pipe that comes in contact with blood and consist of an endothelium and subendothelial layer

Endothelium - lines the lumen of all blood vessels and minimizes friction as blood flow

Subendothelial Layer - supports the endothelium and is the basement membrane and connective tissue

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3
Q

What is tunica media?

A

It is the circularly arranged middle layer of a blood vessel. It is made of smooth muscle and is responsible for vasoconstriction and vasodilation

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4
Q

What is tunica externa?

A

It is the woven layer of collagen outside of the blood vessel. It protects the vessel and anchors it to surrounding structures. It also innervated and vascularized by vasa vasorum in larger vessels

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5
Q

What is the arterial system?

A

Consist of three levels:
-Elastic arteries
-Muscular arteries
-Arterioles

-Extends from the heart to the capillaries
-Decrease in lumen diameter
-Change in the composition of the tunics (less elastic fibers and more smooth muscle)

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6
Q

What are elastic arteries?

A

They are thick-walled arteries near the heart and are also known as conducting arteries

Contain more elastin than other vessels

Serve as the pressure reservoir and is inactive in vasoconstriction

Include the aorta, pulmonary trunk, and the major aortic branches

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7
Q

What are muscular arteries?

A

Known as distributing arteries containing more muscle than elastic arteries

Thicker than tunica media with multiple layers of smooth muscle

Most active in vasoconstriction and vasodilation

Deliver blood to specific body organs

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8
Q

What are arterioles?

A

They are the smallest arteries made of smooth muscle in a slightly constricted state (vasomotor tone)

Responsible for regulating minute-to-minute blood flow to the capillaries

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9
Q

How does blood flow during exercise?

A

Exercise increases total blood flow and blood gets removed from the blood reservoirs

At rest, reconditioning organs receive blood flow in excess of their need. Blood flow to the other organs if sufficient to fulfill that organ’s metabolic need

When activity increase, less blood flow to reconditioning organs and more blood flow to active organs

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10
Q

What is the difference between vasoconstriction and vasodilation?

A

Vasoconstriction - narrowing of the blood vessel

Vasodilation - enlargement of the blood vessel

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11
Q

What is vascular tone?

A

It is the baseline arteriole resistance depends on two factors:
-Considerable self-indulged myogenic activity independent of any neural/hormonal influences
-Sympathetic fibers supplying arterioles continually release NorE to promote vascular tone

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12
Q

What are capillaries?

A

Blood vessels that are responsible for material exchange between the blood and interstitial fluid

Possesses endothelium and basement membrane of sparse connective tissue including pericytes (external smooth muscle-like cells) for stabilization

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13
Q

What are the 3 types of capillaries?

A

Continuous:
-Most common and abundant in skin and muscle
-Cells joined by tight junctions

Fenestrated:
-Similar to continuous but has small pores and is more permeable
-Found where active capillary absorption/filtration occur

Sinusoids:
-Leaky and modified to allow passage of formed elements and plasma proteins
-Possesses an incomplete basement membrane
-Found in the liver and spleen

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14
Q

What are capillary beds?

A

They are interweaving networks of capillaries where blood flow is directed from a metarteriole through the thoroughfare channels towards a post-capillary venule

Two types of vessels:
-Vascular Shunt consists of metarteriole and thoroughfare channel (deoxygenated blood)
-True capillaries (actual exchange vessels)

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15
Q

What are precapillary sphincters?

A

Segments of smooth muscle that are found at the root of the true capillaries

Function:
-Serve as a valve to regulate flow into that capillary
-Causes vasomotion (cycling between open and closed states)

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16
Q

What is the venous system?

A

Two levels: venules and veins

Extend from the capillaries to the heart (increasing in lumen diameter)

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17
Q

What are venules?

A

The smallest veins receive blood from the capillaries
-Post-Capillary Venules have endothelium
-Larger Venules have 1-2 layers of smooth muscles and all 3 tunics

Has to match inflow/outflow with arterioles

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18
Q

What are veins?

A

-Venules merged together
-Typically have all 3 tunica layers, making the external being the heaviest
-Have a high capacitance for blood (serving as blood reservoir)
-Possesses venous valves to allow blood to move toward the heart in one direction

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19
Q

What are varicose veins?

A

When the valve fails to meet properly and gravitational effects allow blood to pool creating varicosities (swelling and enlargement of veins)

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20
Q

How are veins act as a blood reservoir?

A

Due to the high distensibility of veins, it can accommodate greater volumes of fluid with only small incremental pressure increases

Therefore, blood continues to circulate and will spend more time in vein during inactivity (vasodilation)

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21
Q

What are the pathways of blood vessels?

A

Simple Pathway
-One artery, capillary bed, and vein associated with an organ/body region
-One major artery delivers blood to an organ/body region and branches into arterioles to feed a single capillary bed that drains into venules then they merge to form a single vein

Alternative Pathways
-More than one artery, capillary bed, or vein associated with an organ/body region
-Includes 3 types of anastomoses and 1 portal system

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22
Q

What is the difference between arterioles and end arteries?

A

Arterioles = Smaller vessels of an artery

End Arteries = A major artery that delivers blood to an organ or body region

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23
Q

What is arterial anastomoses?

A

2+ arteries converging to supply the same body region

Most common in areas of physical movement (joints, brains, etc.)

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24
Q

What is venous anastomoses?

A

2+ veins draining the same body region

Very common and ensure blood returns to the heart

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25
Q

What is arteriovenous anastomoses?

A

Transports blood from an artery directly to a vein, bypassing the capillary bed, and has a vascular shunt

26
Q

What are portal systems?

A

Blood flows through 2 consecutive capillary beds separated by a portal vein

The Portal vein delivers blood from the 1st capillary to another organ before delivering back to the heart to ensure direct delivery

27
Q

What is the physiology of blood circulation?

A

Blood Pressure (P)
-Force per unit area on a vessel wall that contains blood (refers to the systemic arterial pressure in the largest arteries nearest the heart)

Resistance (R)
-The opposition to blood flow and is the measure of friction blood encounters in a vessel that depends on the factor of blood viscosity, vessel length, and vessel radius

Blood Flow (F)
-Volume of blood flowing through a vessel over a given period of time (summarized by Poiseuille’s law). It is typically laminar traveling in concentric rings

28
Q

What are blood pressure gradients?

A

It is the difference in pressure between the beginning and end of the vessel. It serves as the driving force that propels blood through the vessels

Highest Pressure = Arteries, Lowest Pressure = Veins

Pressure drops along the length of a blood vessel due to frictional losses

29
Q

What is arterial blood pressure?

A

It represents arterial distensibility and the volume of blood forced into them

When blood leaves during heart contractions, more blood enters the arteries than is leaving causing arteries to expand temporarily (systolic pressure)

During heart relaxation, arteries passively recoil to ensure continuous blood flow (diastolic pressure)

30
Q

How do you measure blood flow indirectly?

A

Using a sphygmomanometer (blood pressure cuff). Greater pressure in the cuff blocks off blood flow through the artery

Korotoff sounds are used to determine blood pressure because when the pressure in the artery is greater than the pressure in the cuff, then it produces a sound (systolic). When the cuff no longer exert pressure, the sound disappears (diastolic)

31
Q

What is pulse pressure?

A

The pressure difference between systolic and diastolic pressure measuring the elasticity of the arteries

Declines with increasing distance from the heart

32
Q

What is mean arterial pressure?

A

It is the average pressure driving blood forward and is determined by cardiac output and total peripheral resistance

Provides a numerical value for how well the body tissues are perfused

Declines with increasing distance from the heart

33
Q

What is the difference between systolic pressure and diastolic pressure?

A

Systolic Pressure - Pressure exerted in the arteries when blood is ejected into them during ventricular systole (maximum pressure)

Diastolic Pressure - Pressure within the arteries when blood is draining into the rest of the vessels during ventricular diastole (minimum pressure)

34
Q

What happens in capillary blood pressure?

A

Pulsatile pressure is lost and blood flow becomes smooth and even

Blood pressure diminishes along the length of a capillary due to resistance along the vessel wall and fluid loss. It results in diminishing fluid movement out of the capillaries

A pressure gradient is also maintained due to blood exiting the capillaries to the veins

35
Q

What happens in capillary exchange?

A

Allow for the exchange of substances between the blood and surrounding tissues through the interstitial fluid as the mediary
-Exchange between cells & interstitial fluid is governed by the cell’s plasma membrane
-Exchange between blood plasma & interstitial fluid is governed by laws of diffusion

Dependent of the pressure inside and outside of the capillary through:
-Hydrostatic pressure
-Colloid osmotic pressure

3 types of exchange processes:
-Diffusion
-Vesicular transport
-Bulk flow

36
Q

What is diffusion?

A

A passive event where material/solutes move down their concentration gradients (Blood <–> IF <–> Cell)

37
Q

What is vesicular transport?

A

An active event where endothelial cells use transcytosis (wall to wall from the inside of the cell) to transport solutes incapable of passing through plasma membranes

38
Q

What is bulk flow?

A

The movement of large amounts of fluids and dissolved substances in one direction down a pressure gradient through either filtration or reabsorption

39
Q

What is filtration?

A

Movement of fluid out of the capillaries into the interstitial space occurring at the arterial end of the capillary beds (part of bulk flow)

40
Q

What is reabsorption?

A

Movement of fluid out of the interstitial space into capillaries occurring at the venule end of the capillary bed

41
Q

What is hydrostatic pressure?

A

The physical force exerted by a fluid on a structure (known as blood pressure) through capillary hydrostatic pressure (HPc) and interstitial fluid hydrostatic pressure (HPif)

Capillary hydrostatic pressure (HPc) promotes filtration depending on the amount of fluid in the vessel

Interstitial fluid hydrostatic pressure (HPif) promotes reabsorption

42
Q

What is colloid osmotic pressure?

A

The pull of water into an area by osmosis due to higher solute concentration through blood colloid osmotic pressure (COPc) and interstitial fluid colloid osmotic pressure (COPif)

Blood colloid osmotic pressure (COPc) promotes reabsorption and opposes HPc due to the presence of plasma proteins in the blood

Interstitial fluid colloid osmotic pressure (COPif) promotes filtration

43
Q

What is net filtration pressure?

A

The difference between hydrostatic pressure and osmotic pressure

NFP = (HPc - HPif) - (COPc - COPif)

+NFP = outward flow to IF
-NFP = inward flow to the capillary

44
Q

What is venous blood pressure?

A

It is blood pressure within the veins characterized as:
-Flow is smooth and even
-No pulse pressure
-Shallow pressure gradient (venules = 20mmHg, atria = 0mmHg)

45
Q

What is venous return? How does gravity affect it?

A

The movement of blood from capillaries to the heart through the vein

Blood below the heart level is subject to the pressure from the weight of the blood above it where blood tends to pool instead of returning to the heart. 3 factors help with propelling blood back into the heart:
-Valves within veins
-Skeletal muscle pump
-Respiratory pump

46
Q

What happens in the skeletal muscle pump?

A

Assists the movement of blood primarily within the limbs by pushing blood in veins toward the heart

Muscle contractions yield external venous compression and blood is forced away from the compressed veins

Blood below contracted muscle is not subjected to the full weight & pressure of the full blood column

47
Q

What happens in the respiratory pump?

A

It assists the movement of blood within the thoracic cavity

Inhalation
-Diaphragm muscle contracts and moves inferiorly, thoracic cage expands while the abdominal cavity contracts (increasing pressure in the abdomen and reducing pressure in the thoracic cavity)
-Propels blood from the abdomen to the thoracic cavity

Exhalation
-Diaphragm muscle relaxes and moves superiorly, thoracic cage contracts while the abdominal cavity expands (reducing pressure in the abdomen and increasing pressure in the thoracic cavity)
-Propels blood from the thoracic cavity in the heart and draws blood from the lower limbs into the abdomen

48
Q

What is the difference between ventricular systole and ventricular diastole?

A

Ventricular Systole
-Ventricle contracts, atrial cavity enlarges (decrease atrial pressure to 0mmHg)
-Increase venous return by increasing the pressure gradient

Ventricular Diastole
-Ventricle relaxation results in decreased ventricular pressure
-Lower pressure sucks blood from atria & veins

49
Q

What is the short and long-term of regulating blood pressure?

A

Short-Term:
-Quick response and short-lived (in seconds)
-Altering cardiac output & total peripheral resistance via the nervous system

Long-Term:
-Slow response and long-lived (minutes to days)
-Altering blood volume by restoring normal salt and water balance via hormones

50
Q

What is the cardiovascular center?

A

Two autonomic nuclei located in the medulla consisting of the cardiac center and the vasomotor center

51
Q

What is the cardiac center?

A

It regulates the heart activity through two centers:

Cardioacceleratory Center
-Sympathetic fibers to SA node & myocardium
-Increases heart rate, cardiac output, and force of contraction

Cardioinhibitory Center
-Parasympathetic fibers to SA node & AV nodes
-Decreases heart rate, cardiac output, and conduction of electrical signals

52
Q

What is the vasomotor center?

A

Regulates a degree of vasoconstriction of blood vessels by 2 types:
-Alpha receptors cause most vessels in the body to contract in response to sympathetic stimulation
-Beta receptors cause vessels to relax in response to Epi stimulation affected skeletal muscles and coronary vessel

Results in:
-Increased peripheral resistance and circulating blood volume to the skeletal muscles and heart

53
Q

What are baroreceptors?

A

They are specialized sensory nerve endings that respond to stretch in blood vessel walls

Baroreceptor reflexes (rate of firing) determine the signal response that was sent to the medulla
-Increased pressure = increased firing by afferent fiber
-Decreased pressure = decreased during by afferent fiber

54
Q

What are aortic arch baroreceptors?

A

A receptor that is located in the tunica external of the aortic arch

It transmits signals to the cardiovascular center through the vagus nerve and monitors blood pressure in the aorta (systemic blood pressure)

55
Q

What are carotid sinuses baroreceptors?

A

A receptor that is located in the tunica external of each internal carotid artery

It transmits signals to the cardiovascular center through the vagus nerve and monitors blood pressure in the head and neck (brain blood pressure)

56
Q

What are chemoreceptor reflexes?

A

A negative feedback loop that is involved in mainly regulating respiration and also blood pressure

Able to detect carbon dioxide, pH, and low oxygen levels and sends signals to the vasomotor center, resulting in increased sympathetic activity to blood vessels. It also increases peripheral resistance & shifts blood from the reservoirs to venous return

2 Main Peripheral Chemoreceptors:
-Aortic bodies (arch of the aorta)
-Carotid bodies (external carotid artery)

57
Q

What is antidiuretic hormone (ADH)?

A

A hormone (also known as vasopressin) that stimulates kidneys to conserve water and maintain blood volume

It can also cause vasoconstriction in reverse conditions (hemorrhage)

58
Q

What is angiotensin II (AT II)? What are the short-term and long-term regulations?

A

A hormone that is part of the Renin-Angiotensin system that stimulates thirst sensation

Short-Term Regulation = stimulate vasoconstriction

Long-Term Regulation = stimulates the secretion of aldosterone & ADH

59
Q

What is adrenal medulla hormones?

A

Norepinephrine (NorE) and epinephrine (Epi) enhance sympathetic response

Ex. vasoconstriction and increased blood pressure)

60
Q

What is atrial natriuretic peptide (ANP)?

A

A hormone that causes generalized vasodilation

Antagonizes aldosterones and promotes the excretion of water and salt thus decrease in blood volume

61
Q

What is renin?

A

An enzyme that is part of the Renin-Angiotensin system from the kidney

Secreted to decreases in NaCl, ECF volume, and blood pressure

Acts to activate angiotensinogen into angiotensin I (AT I) which is then converted into angiotensin II (AT II) to stimulate the secretion of aldosterone

Results in Na reabsorption and water retention

62
Q

What is aldosterone?

A

A hormone secreted by the adrenal cortex and is part of the Renin-Angiotensin system

It increases Na reabsorption in the kidneys where the more passive movement of Na out of tubules & more Na pumped into ECF

BIOL 2302 Anatomy & Physiology II (5 decks)

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