A&P II Exam #2 (CH 18 and 19) - Questions

The Cardiovascular System (Heart) and The Lymphatic System

name the coverings of the heart and describe the functions of the fibrous pericardium

pericardium - double-walled and surrounds the heart

• fibrous pericardium 

  • superficial layer

  • protection

  • anchors heart to surrounding structures

  • prevents overfilling

• serous pericardium

  • deep, double-layered

  • parietal layer - lines internal surface of fibrous pericardium

  • visceral later (epicardium) - external surface

  • pericardial cavity - filled with serous fluid (allows for heart to work without friction

describe the three layers of the heart wall. What is the function of the myocardium

epicardium - visceral layer of serous pericardium

myocardium - layer that actually contracts

endocardium - sheet of squamous endothelium

describe the functions of the four heart chambers

2 atria - entryways

• receives blood

• small and thin-walled (only needs to push to ventricles, gravity also helps)

• sits above ventricles

• contains auricles - small, wrinkled, protruding appendages, increases atrial volume

2 ventricles - underside

• discharging chambers - actual pumps of heart

• thicker myocardium (pump to rest of body)

• trabeculae carneae - irregular ridges of muscles that mark the internal walls

• papillary muscles - plays a role in valve function, project into the ventricular cavity 

name each chamber and provide the name and general route of its associated great vessel(s)

RA

• posterior wall is smooth

• anterior wall contains pectinate muscles

• may contain fossa ovalis

• superior vena cava, inferior vena cava, coronary sinus

LA

• mostly smooth

• pectinate muscles found only in the auricles

• may contain fossa ovalis

• four pulmonary veins - blood from the lungs to heart

RV 

• chamber closest to the surface

• pumps blood to pulmonary trunk

LV

• majority of posteroinferior surface of heart

• pumps blood to aorta

name the three veins which return blood to the RA

superior vena cava, inferior vena cava, and coronary sinus

name the heart valves and describe their location, function, and mechanism of operation

atrioventricular (AV) valves - prevents backflow to atria when ventricles contract

• tricuspid - right AV, 3 cusps

• bicuspid (mitral) left AV, 2 cusps

  • BOTH contains chordae tendineae (heart strings)

semilunar (SL) valves - prevents backflow from major arteries back to ventricles 

• pulmonary SL valve - RV to pulmonary trunk, 3 cusps

• aortic SL valve - LV to aorta, 3 cusps

what is the function of the chordae tendineae

anchors cusps of AV valves to papillary muscles

• hold valve flaps in closed position

• prevents flaps from everting back to atria

• allows unidirectional blood flow

trace the pathway of blood through the heart

pulmonary circuit

• SVC and LVC and coronary sinus → RA → tricuspid valve → RV → pulmonary semilunar valve → pulmonary trunk → pulmonary arteries → lungs

systemic circuit 

• four pulmonary veins → LA → mitral/bicuspid valve → aortic semilunar valve → aorta → body 

true or false - veins always carry oxygen-poor blood, and arteries oxygen-rich blood

false

• pulmonary arteries does not contain oxygen rich blood (away from heart, towards lungs)

• pulmonary veins contain oxygen rich blood (away from heart, towards body)

name the major branches and describe the distribution of the coronary arteries

what is their function

coronary arteries

• left coronary arteries

  • anterior interventricular artery - supplies interventricular system and septum and anterior walls of both ventricles

  • circumflex artery - supplies LA and posterior wall of LV

• right coronary arteries

  • right marginal artery - supplies myocardium of lateral right of heart

  • posterior interventricular artery - runs to apex of heart and supplies posterior interventricular walls (merges with AIA at the apex of the heart) 

coronary veins

• cardiac veins collect blood from capillary beds

• coronary sinus - empties into RA 

  • great cardiac vein - anterior interventricular sulcus

  • middle cardiac vein - posterior interventricular sulcus

  • small cardiac vein - right interior margin 

what is the result of coronary artery blockade

myocardial infarction (heart attack)

• prolonged coronary blockage

• cells die - amitotic heart cells are replaced with noncontractile scar tissue 

*angina pectoris (choked chest) 

• thoracic pain due to fleeting deficiency in blood delivery to myocardium

• weakened cells, not dead

what is the coronary sinus

returns deoxygenated blood from coronary veins, drained into the RA

how does the structure and function of cardiac muscle cells differ from skeletal muscle fibers

not in-depth explanations

some cardiac muscle cells are self-excitable

heart contracts as a unit

uses both SR and EF calcium to contract

• skeletal only uses SR to contract

NO tetanic contractions (build up) in cardiac muscles

heart relies on O2 respirations 

• can use other pathways, but NEEDS O2

what structures can you find in the intercalated discs of cardiac cells

what is their function

gap junctions

• allows ions to pass cell to cell, electrically couple adjacent cells

• allows heart to be a functional syncytium (single coordinated unit)

desmosomes

• holds cells together, prevents cells from separating from contraction 

what is a functional syncytium

which structures of the intercalated discs allow the myocardium to function as a functional syncytium

a single coordinated unit - gap junctions (passage of ions, electrically connected)

calcium is needed for muscle contraction, what is the source of calcium for skeletal and cardiac muscle fiber contraction

cardiac muscle cells use both SR and EF for contraction

• skeletal muscle does not use EF calcium for contraction 

what are the cardiac pacemaker cells and what is their function

specialized cells that have the ability to depolarize spontaneously

• unstable resting potential - continuously depolarize 

• pacemaker potential - the spontaneously changing membrane potential that initiate action potential trigger rhythmic contractions 

name the function of the SA node

name the components of the conduction system of the heart and their location trace the conduction pathway

sinoatrial node, pacemaker, sinus rhythm

• initiates action potential

why are the impulses delayed at the AV node

which modifications are responsible for this delay

due to lower number of gap junctions and small diameter of muscle fibers

• allows atria to complete their contraction before ventricles contract

draw the pacemaker and action potentials of cardiac pacemaker cells

indicate which ion channels are open/closed during:

• pacemaker potential

• depolarization

• repolarization

pacemaker potential

• slow sodium channels open, NA+ enters cell

• potassium channels are closed

• membrane potential becomes less negative

depolarization/action potential

• calcium channels open (Ca2+ enters cell) - voltage gated (sodium channels)

• membrane potential becomes less negative FASTER

repolarization

• calcium channels close

• potassium channels open, K+ leaves cell

• membrane potential becomes more negative 

define the pacemaker potential

which event causes the pacemaker potential

the spontaneously changing membrane potential that initiate action potential trigger rhythmic contractions

• opening of slow sodium channels 

draw the action potential of contractile cardiac muscle cells

indicate which ion channels are open/closed during:

• depolarization

• plateau phase

• repolarization

depolarization/action potential

• fast voltage gated sodium channels open

• Na+ enters the cell

• MP becomes less negative, more positive

• immediate depolarization

plateau

• potassium channels start opening (exits cell)

• slow calcium channels open (enters cell)

• MP SLOWLY becomes more negative 

  • allows for a longer refractory period 

  • prevents tetanic contractions 

repolarization

• inactivated Ca2+ channels

• potassium channels open up (K+ leaves the cell)

• MP becomes more negative 

describe and compare action potentials in cardiac pacemaker and contractile cell

the influx of Ca2+ that produces rising phase of action potential

• pacemaker cells → slow, Ca2+

• contractile cell → fast, Na+

compare the actions potential in cardiac and skeletal muscle fiber

skeletal - action potential is 1-2 milliseconds

cardiac - AP is >200 milliseconds 

• plateau - slow Cs2+ entering the cell 

• allows for an effective pump 

name one important consequence of the long plateau phase observed in contractile cell

cardiac muscle stays contracted longer due to Na+ channels staying in a longer inactive state

• allows for efficient ejection of blood 

• prevents tetanic contractions

• slow calcium channels also plays a role (Ca2+ flows in)

can the basic rhythm of the heart be modified

yes - changes in lifestyle (ex: exercise), medications, pacemakers, AED, caffeine, alcohol, body temperature

• autonomic nervous system - cardiac centers in medulla oblongata

  • cardioacceleratory center - sympathetic trunk to increase heart rate and force (innervates SA and AV nodes, heart muscles and coronary arteries 

  • cardioinhibitory center - parasympathetic signals via vagus nerve to decrease rate (innervate mostly the SA and AV nodes)

which parts of the conduction system are innervated by the autonomic nervous system

cardioacceleratory center

• medulla oblongata → thoracic spinal cord → sympathetic trunk → SA and AV nodes, heart muscles and coronary arteries 

• cardioinhibitory center

cardioinhibitory center

• medulla oblongata (dorsal motor nucleus of vagus) → SA and AV nodes

what is an electrocardiogram

draw a diagram of a normal electrocardiogram tracing

name the individual waves and intervals, and indicate what each represents

a graphic recording of electrical heart activity

• P wave: depolarization of SA node and atria

• QRS complex: ventricular depolarization and atrial repolarization

• T wave: ventricular repolarization

• P-R interval: beginning of atrial excitation to beginning of ventricular excitation

• S-T segment: entire ventricular myocardium depolarized

• Q-T interval: beginning of ventricular depolarization through ventricular repolarization

heart abnormalities can be detected on an ECG tracing, how would enlarged ventricles, a heart attack and an nonfunctional SA node show in an ECG tracing

enlarged ventricles - enlarges R waves

heart attack- electrical activity is disorganized

nonfunctional SA node - P waves are absent, AV node paces heart (slower bpm - 40 to 60 bpm)

true or false - the cardiac cycle includes all events associated with the blood flow through the heart during one complete heartbeat - atrial systole and diastole followed by ventricular systole and diastole

true

name the phases of the cardiac cycle and describe the events that take place during every phase

• first half of first step

ventricle filling (passive)

• the heart in the aorta is 120-80 mmHg

• pressure in the heart is low

• as the atrium and ventricle fill with blood (AV valves are open) the pressure in both chambers increases

• 80% of ventricular filling occurs 

name the phases of the cardiac cycle and describe the events that take place during every phase

• second half of first step

ventricular filling (atrial systole)

• the P wave occurs - atrial systole

• the atria depolarize and contract

• the atria pump some extra blood into the ventricles and the pressure in both chambers slightly increases

  • remaining 20% of ventricular blood is pumped here

• last part of ventricular diastole (end diastolic volume)

• atria relax for the remainder of cardiac cycle 

name the phases of the cardiac cycle and describe the events that take place during every phase

• second step

ventricular isovolumetric contraction

• the QRS complex occurs 

• the ventricle starts contracting → the pressure in the ventricle progressively increases

• a small volume of blood is pushed into the atrium, closing the AV valve temporarily increasing the pressure in the atrium

• split second phase - ventricles are completely closed, and volume in unchanged

• the pressure in the aorta is higher than the pressure in the ventricle, the blood is still not ejected into the aorta (pressure goes from high to low)

name the phases of the cardiac cycle and describe the events that take place during every phase

• first half of third step

ventricular ejection

• the ventricle pressure exceeds the aortic pressure (diastolic pressure ~ 80mmHg)

  • the semilunar valve opens

  • blood in the ventricle is ejected into the aorta

  • pressure in ventricle and aorta keeps increasing 

• as the pressure increases within aorta, the aorta distends 

name the phases of the cardiac cycle and describe the events that take place during every phase

• second half of third step

ventricular ejection

• pressure in aorta reaches maximum (systolic pressure ~ 120mmHg)

• T wave occurs, the ventricles begins to repolarize

name the phases of the cardiac cycle and describe the events that take place during every phase

• fourth step

ventricular isovolumetric relaxation

• ventricles relax - early diastole

• blood remaining in the ventricles after contraction - end systolic volume (ESV)

• ventricular pressure falls below aortic pressure → semilunar valves close

• closure of aortic valve raises aortic pressure as backflow rebounds off close valve cusps (dicrotic notch)

  • causes back flow of blood that fills the coronary arteries

• the pressure in the filling atrium keeps increasing

name the phases of the cardiac cycle and describe the events that take place during every phase

• ‘last’ step going back to first step

ventricular filling (passive)

• the pressure in the relaxing ventricle falls below the pressure in the atrium

  • AV valve opens

  • blood flows from the atrium to the ventricle

which phases of the cardiac cycle overlap with ventricular contraction and which with ventricular relaxation

isovolumetric contraction phase - AV valves close and SL valves open

• systole, first heartbeat is heard 

isovolumetric relaxation phase - SL valves open and AV valves close 

• diastole, second heartbeat is heard 

define end diastolic volume (EDV) and end systolic volume (ESV)

EDV: volume of blood in each ventricle at end of ventricular diastole

ESV: volume of blood remaining in each ventricle after systole

when do the valves open/close during the cardiac cycle? When does the dicrotic notch occur

in order of cardiac cycle:

• AV valves close when the ventricular pressure exceeds the atrial pressure

• SL valves open when the ventricular pressure exceeds the aortic pressure

• SL valves close when the ventricular pressure drops below aortic pressure 

  • slight raise in aortic pressure due to backflow rebounding off of closed valve cusps (dicrotic notch)

• AV valves open when the ventricular pressure drops below the atrial pressure

during which phase of the cardiac cycle do the heart sounds occur

first heart beat:

• isovolumetric contraction phase (systole)

• as the AV valves close

second heart beat:

• isovolumetric relaxation phase (diastole)

• as the SL valves close 

define cardiac output (CO) and stroke volume (SV)

CO: amount of blood pumped out by each ventricle in one minute

• equals heart rate (HR) times stroke volume (SV)

SV: volume of blood pumped out by one ventricle with each beat

• correlates with force of contraction

name 3 factors that influence stroke volume, explain how

1. preload (intrinsic influence)

• degree of stretch of heart muscle

• preload: degree to which cardiac muscle cells are stretched just before they contract

• high preload = higher SV

• relationship between preload and SV is called Frank-Starling law of the heart

• stretching leads to dramatic increase in contractile force 

• venous return - amount of blood returning to heart

  • slow heartbeat and exercise increase venous return

  • increased venous return distends (stretches) ventricles and increases contraction force 

  • increase in venous return → increase in EDV → increase in SV → increase in CO 

    • increase in EDV → increase in SV = Frank-Starling law of the heart

name 3 factors that influence stroke volume, explain how

2. contractibility (extrinsic influence)

• contractile strength at given muscle length

  • independent of muscle stretch and EDV

• increased contractility lowers ESV caused by:

  • sympathetic epinephrine release stimulants increased Ca2+ influx, leading to more cross bridge formations

  • sympathetic stimulation (NE/E) → more Ca2+ in the cardiac myocytes → increased force of contraction (contractility) → increased SV

name 3 factors that influence stroke volume, explain how

3. afterload

• afterload: pressure that ventricles must overcome to eject blood

  • back pressure from atrial blood pushing on SL valves

    • aortic pressure is around 80mmHg

• healthy individuals: afterload is not a major determinant of SV since remains constantly

  • hypertension increases afterload, reducing the ability of ventricles to eject blood

what is venous return and how does it influence the stroke volume

venous return: amount of blood returning to heart

• increased VR distends (stretches) ventricles and increases contraction force

• increase in venous return → increase in EDV → increase in SV → increase in CO 

  • increase in EDV → increase in SV = Frank-Starling law of the heart

which mechanism results in an increased stroke volume during exercise? (hint: increased venous return

contraction of skeletal muscles ‘milks’ blood back towards heart (muscular pump), increasing venous return, increasing preload, increasing SV

how is the contractility of the myocardium regulated (hint: sympathetic nervous system)

compare and contrast preload and contractility

sympathetic epinephrine release stimulants increased Ca2+ influx, leading to more cross bridge formations

• sympathetic stimulation (NE/E) → more Ca2+ in the cardiac myocytes → increased force of contraction (contractility) → increased SV

• preload: degree to which cardiac muscle cells are stretched just before the contract

• contractility: the intrinsic strength and ability of the myocardium to contract, independent of the initial fiber length

how does high blood pressure affect the stroke volume and why

hypertension increases afterload, reducing the ability of ventricles to eject blood

• heart has to work harder to pump blood against the elevated resistance in the arteries

how is the heart rate regulated by the sympathetic and parasympathetic division of the autonomic nervous system

• sympathetic

stress → sympathetic stimulation → release of NE → faster depolarization of the pacemaker cells (SA and AV nodes) and increased Ca2+ influx in cardiac myocytes (contractile cells) → increased HR (positive chronotropism) and increased contraction force (positive inotropism)

how is the heart rate regulated by the sympathetic and parasympathetic division of the autonomic nervous system

• parasympathetic

after the stress has passed → parasympathetic stimulation → release of ACh → pacemaker cells (SA and AV nodes) hyperpolarize (binding of ACh to its receptor initiates signaling cascade that opens K+ channels in node cells) → decreased HR (negative chronotropism)

explain the role of the autonomic nervous system in regulating cardiac output

controlling heart rate and contractility through two branches: sympathetic and parasympathetic systems

• cardioinhibitory and cardioacceleratory Center

what is coronary atherosclerosis

clogged arteries caused by fat buildup; impairs oxygen delivery to cardiac cells

t or f: a succession of heart attacks might decrease the pumping efficiency of the heart because dead heart cells are replaced by non-contractile scar tissue.

true

compare and contrast pulmonary and systemic congestion

systemic (peripheral) congestion

• right side fails

  • right side of the heart is unable to pump blood efficiently, causing it to back up into the body

• blood stagnates in body organs

• fluid leaks into tissue spaces

pulmonary congestion

• left side fails

  • LV cannot effectively pump blood into the body, causing blood and fluid back into the lungs

• pressure in blood vessels of lung increases

• fluid leaks from vessels into lung tissue

• pulmonary edema leads to suffocation (lungs fill w/fluid and not O2)

describe the three layers that typically form the wall of a blood vessel and state the function of each

tunica intima

• endothelium - simple squamous epithelium that lines lumen of all vessels

• subendothelial layer

• internal elastic membrane

• allows a slick surface that reduces friction

• continuous with the endocardial lining of the heart chambers

tunica media

• smooth muscle and elastic fibers

• plays a role in vasoconstriction and vasodilation

• bulkiest layer - responsible for maintaining blood flow and blood pressure in arteries 

tunica externa

• loose collagen fibers - protect and reinforce wall and anchor it to surrounding structures

• contains nerve fibers, lymphatic vessels and vasa vasorum

define vasoconstriction and vasodilation

vasoconstriction: decreased lumen diameter

• reduced heat loss through skin, makes blood vessels smaller → away from skin surface

• increased BP

vasodilation: increased lumen diameter

• release heat through the skin → BV are closer to the surface of skin

• decreases BP

compare and contrast the structure and function of the three types of arteries

• elastic arteries (conducting arteries)

thick-walled, largest in diameter, most elastic

near the heart (aorta and major branches)

largest in diameter: 2.5mm to 1cm

elastin found in all three tunics, mostly tunica media

contain substantial smooth muscle, but inactive in vasoconstriction

function: acts as pressure reservoirs that expand and recoil as blood ejected from heart

• allows for continuous blood flow downstream even between heartbeats

compare and contrast the structure and function of the three types of arteries

• muscular arteries

distribute blood to major organs

• aka distributing arteries

account for most of named arteries

diameter range: pinky finger to a pencil lead

has the thickest tunica media, with more smooth muscle and less elastic fibers than elastic arteries

• less capable of stretching 

function: active in vasoconstriction, deliver blood to body organs 

compare and contrast the structure and function of the three types of arteries

• arterioles

smallest of all arteries

aka resistance vessels - since changing diameters changes resistance to blood flow 

diameter range: 0.33mm to 10uM

larger arterioles contain all three tunics

• smaller arterioles are mostly single layer of smooth muscle surround endothelial cells with very little elastic fibers

function: control flow into capillary beds via vasodilation and vasoconstriction of smooth muscle

leads to capillary beds 

describe the structure and function of a capillary bed

interwoven network of capillaries between arterioles and venules

terminal arteriole: branches into 10 to 20 capillaries (exchange vessels) that form capillary beds and drain to postcapillary venules

microscopic vessels; diameter is so small only one RBC can pass through at a time

• 1mm in length and 8-10uM in diameter

pericytes: contractile stem cells, lie along the outer surface for generation of new vessels, stability and permeability control

function: exchange of gases, nutrients, wastes, and hormones

name the 3 types of capillaries

continuous capillary, fenestrated capillary, and sinusoid capillary

least permeable:

• continuous capillary

largest fenestrations and intercellular clefts:

• largest fenestrations - fenestrated capillary

• large intercellular clefts - sinusoid capillary

present in the CNS, kidneys, intestine, and bone marrow:

• CNS - continuous capillary

• kidneys, intestine - fenestrated

• bone marrow - sinusoid 

continuous capillary

least permeable and most common

abundant in skin, muscles, lungs and CNS

often have associated pericytes 

pinocytotic vesicles ferry fluid across the endothelial cell

brain capillary endothelial cells lack intercellular clefts and have tight junctions around their entire perimeter (blood brain barrier)

fenestrated capillar

large fenestrations (pores) that increase permeability

occurs in areas of active filtration (kidneys) or absorption (small intestine) and areas of endocrine hormone secretion

fenestrations - holes that tunnel through endothelial cells

sinusoid capillary

most permeable and occur in limited locations

occur in liver, bone marrow, spleen, and adrenal medulla

have large intercellular clefts as well as fenestrations

• few tight junctions

have incomplete basement membranes

allow for large molecules and even cells to pass across their walls 

is blood always flowing freely through the capillaries

what happens with the capillary beds in muscles and intestine:

• when you exercise

• after you eat

blood does not always flow freely though the capillaries

• vascular shunts for bypass

  • directly connect the terminal of arteriole to the postcapillary venules 

• precapillary sphincters

  • acts as a valve to regulate blood flow into the capillary bed 

muscles:

• when you exercise: capillary beds open → more blood flow for oxygen and nutrients

• after you eat: capillary beds less active (blood is directed to the gut instead)

intestine: 

• when you exercise: capillary beds constrict (blood diverted to muscles)

• after you eat: capillary beds open → more blood flow for digestion and absorption

describe the structure and function of veins and explain how veins differ from arteries

• venules

diameter range from 8-100uM

extremely porous, like capillaries, to allow fluid and WBC to move easily into tissues 

most have only tunica intima, with larger venules gaining a think tunica media and externa

describe the structure and function of veins and explain how veins differ from arteries

• veins

have all tunics, but thinner walls with larger lumens 

tunica media is thin, but tunica externa is thick

• tunica externa contains collagen fibers and elastic networks

large lumen and thin walls make veins good storage vessels

• called capacitance vessels (blood reservoirs) because they contain up to 65% of blood supply

explain how veins differ from arteries

arteries

• carry oxygenated blood away from heart

• thicker, more tunica media (smooth muscle) due to high pressure of blood flow

  • ratio of smooth muscle to collagenous tissue will always be greater

• does not contain valves (other than pulmonary artery)

• closer to major organs

veins

• carry deoxygenated blood towards heart

• thinner, less muscular wall, lower BP

• contains venous valves

  • prevent backflow of blood

  • formed from folds of tunica intima

  • resemble SL valves 

  • most abundant in veins of limbs 

define blood flow, blood pressure, and resistance

blood flow: volume of blood flowing through vessel, organ, or entire circulation in given period 

• ml/min

• equivalent to cardiac output for entire vascular system

• flow through individual organs may vary

blood pressure: force per unit area exerted on wall of blood vessel by blood

• mmHg

• measured as systemic arterial BP in large arteries of heart

• pressure gradient provides driving force that keeps blood moving from higher to lower pressure areas

resistance (total peripheral resistance/TPR): opposition to flow (most friction occurs in periphery)

• measurement of amount of friction blood encounters with vessel walls

• three important sources of resistance

  • blood viscosity

  • total blood vessel length

  • blood vessel diameter

explain the relationships between blood flow, blood pressure, and resistance

blood flow is directionally proportional to the difference in pressure between two points (pressure gradient)

• as difference in pressure changes, BF follows the same direction

  • more blood pumping = more blood pushing against vessels 

blood flow is inversely proportional to total peripheral resistance (TPR)

• as TPR increases, blood flow decreases

describe how blood pressure differs in the arteries, capillaries, and veins

blood is driven through the body by a pump through a closed circuit under pressure

nearer the pump, the greater the pressure

pumping action of the heart generates blood flow, while pressure is established from resistances

greatest pressure to least pressure:

• heart → aorta → arteries → arterioles → capillaries → venules → veins → venae cavae → right atrium 

name three structural adaptations that are important for maintaining venous return

1. muscular pump: contraction of skeletal muscles ‘milks’ blood back towards heart

2. respiratory pump: pressure changes during breathing, moves blood towards heart by squeezing abdominal veins (diaphragm contracts and the thoracic cavity expands - lowering pressure in chest cavity, lower pressure in chest = pushes blood from abdomen into thorax and towards heart)

3. sympathetic venoconstriction: under sympathetic control, smooth muscle constrict, pushing blood back towards heart

all methods increase venous return → increasing stroke volume and cardiac output

list and explain the factors that influence blood pressure

cardiac output

peripheral resistance (PR)

blood volume

MAP = stroke volume x heart rate x TPR

anything that increases SV (venous return), HR (medullary centers), or R (mostly vessel diameters) also increases pressure

Short-term regulation of blood pressure is mediated by _________ and _________.

Short-term regulation alters blood pressure by changing ____/______.

Long-term regulation is mediated by______/_ ____.

Long-term regulation alters blood pressure by changing ________

neural; hormonal controls

TPR; CO

renal; hormonal controls

blood volume 

where is the location and what is the function of the vasomotor center

what is the vasomotor tone

vasomotor center: controls diameter of blood vessels

• found in the medulla oblongata

• sends steady impulses via sympathetic efferent to blood vessels

vasomotor tone: continuous moderate constriction of arterioles

• helps regulate BP and BF

list the events which help to maintain the blood pressure by the baroreceptor reflex (short-term blood pressure regulation)

1. stimulus: BP rises above normal

2. baroreceptors in carotid sinuses and aortic arch are stimulated 

3. increased impulses from baroreceptors

   1. stimulate cardioinhibitory center 

   2. inhibit cardioacceletory center

   3. inhibit vasomotor center

4. decreased vasomotor impulses - causing vasodilation (causing reduced TPR) and decreased sympathetic impulses to heart cause decreased HR, contractility, and CO

5. reduced CO and TPR return blood pressure to homeostatic range 

Describe the effects (stimulatory/inhibitory) of activated baroreceptors on

• cardiovascular centers (cardioacceleratory, cardioinhibitory and vasomotor centers) in the

medulla oblongata

• stroke volume, heart rate, total peripheral resistance, and blood pressure

cardioacceletory: inhibited → causes the heart to pump less, decreasing BP (reduces the force and volume of blood circulating in the arteries)
cardioinhibitory: stimulated → slows heart rate

vasomotor center: inhibited → uses sympathetic efferent (cardioacceleratory), vasodilation of arterioles and veins

SV: decreases (less sympathetic simulation → less contractility → smaller SV)

HR: decreases

TPR: decreases (vasodilation from reduced vasomotor tone

BP: decreases to normal range

describe the direct and indirect renal/hormonal mechanisms of blood pressure regulation. Name the 4 mechanisms activated by angiotensin II in the indirect renal blood pressure regulation (long-term blood regulation)

direct: decreased arterial pressure → decreased filtration by kidneys → decreased urine formation (keeping fluid in) → increasing blood volume → increase in MAP

• natural function the kidney does - does not require a signal

indirect: decreased arterial pressure → inhibits baroreceptors → increased sympathetic nervous system activity → increased renin release from kidneys

• renin turns angiotensinogen to angiotensin I, angiotensin converting enzyme turns I into II

  • II signals adrenal cortex → release aldosterone → increase sodium reabsorption by kidneys → H2O reabsorption by kidneys → increase blood volume → increased MAP

  • II signals to increase ADH release by posterior pituitary gland → H2O reabsorption by kidneys → increase blood volume → increased MAP

  • II increases thirst via hypothalamus → increase in water intake → increase blood volume → increased MAP

  • II increases vasoconstriction = increase in TPR → increase MAP

define hypertension and describe the effects of prolonged hypertension on the heart

hypertension: high blood pressure

• damages the heart by causing the left ventricle to thicken and enlarge = strains the heart and makes it less effective at pumping blood 

• can lead to reduced blood supply to heart muscle, which can cause heart failure 

name the 2 types of intrinsic controls of blood flow

intrinsic controls (autoregulation) - within tissue or organ; uses paracrines or muscle tissue properties

• metabolic or myogenic controls

• distribute blood flow to individual organs and tissues as needed

  • vasodilators: low O2, high CO2, high H+, high K+, prostaglandins, adenosine, nitric oxide

  • vasoconstrictors: myogenic (stretch); metabolic (endothelin)

name the 2 types of extrinsic controls of blood flow that cause vasoconstriction

extrinsic controls - outside tissue or organ

• neural or hormonal controls 

• maintain MAP

• redistribute blood during exercise and thermoregulation

  • vasodilation: neural → decreases sympathetic tone; hormonal → atrial natriuretic peptide 

  • vasoconstriction: neural → increase sympathetic tone; hormonal → angiotensin !!, antidiuretic hormone, epinephrine, and norepinephrine 

how would O2, CO2 and sympathetic stimulation influence blood flow

O2 vasodilates at high levels but can cause systemic vasoconstriction under severe systemic hypoxia 

CO2 vasodilates in most tissues and sympathetic stimulation generally causes vasoconstriction, except the brain

explain how blood flow through muscles and intestine is regulated during exercise.

active or exercise hyperemia: during muscle activity, blood flow increases in direct proportion to metabolic activity

• blood flow in muscles: metabolic factors induce vasodilation

• blood flow in kidneys, intestine: inhibited by sympathetic vasoconstriction 

what is the relationship between cross-sectional area of vessels and blood flow velocity

velocity of flow changes as blood travels through systemic circulation

• velocity = flow rate/total cross-sectional area

speed is inversely related to total cross-sectional area

• capillaries have largest area so slowest flow

ex: highway system

• fewer lanes = cars move faster

  • big freeway (aorta): one or two wide lanes → all the cars (blood) funnel through a small cross-sectional area → cars move fast

• more lanes = cars slow down

  • exiting roads (venules/veins): the little roads merge back into bigger streets → fewer total lanes → cars pick up speed again, but not quite as fast as on the freeway.

why is the blood flow in the capillaries slow compared to the blood flow in the aorta?

capillaries have massive area - millions of tiny capillaries, total area of the vascular bed is much larger than the aorta, causing the blood to move slower

why is a slow blood flow in the capillaries beneficial

allows adequate time for exchange between blood and tissues

describe the four routes of transport across the endothelial cell wall of capillaries

1. diffusion through plasma membrane (lipid-soluble substances)

2. movement through intercellular clefts (water-soluble substances)

3. movement through fenestrations (pores - water-soluble substances)

4. transport via vesicles (large substances; endocytosis or exocytosis)

define bulk flow

why is it important

fluid is forced out of clefts of capillaries at arterial end, and returns to blood at venous end 

• important in determining relative fluid volumes in blood and interstitial space

• refreshes/maintains interstitial environment 

define hydrostatic pressure and osmotic pressure

hydrostatic pressure: force exerted by fluid pressing against wall

• in capillary: pushes fluid out of capillary

• in interstitial fluid: pushes fluid into capillary

osmotic pressure: sucking pressure created by nondiffusible plasma proteins (albumin) pulling water back into capillary (encouraging osmosis

• in capillary: pulls fluid into capillary

• in interstitial fluid: pulls fluid out of capillary

describe the different types of pressures that are implicated in bulk flow

explain how these pressures determine the exchange of fluid between blood and the interstitial space along the capillaries

arteriolar end of capillary:

NFP = 10mmHg out of capillary (fluid moves from capillary into the interstitial space) 

• hydrostatic pressure in capillary: 35mmHg out of capillary

• osmotic pressure in capillary: 26mmHg into capillary

• hydrostatic pressure in IF: 0mmHg into capillary

• osmotic pressure in IF: 1mmHg out of capillary

venous end of capillary:

NFP = -8mmHg (fluid moves from the interstitial space into capillary)

• hydrostatic pressure in capillary: 17mmHg out of capillary

• osmotic pressure in capillary: 26mmHg into capillary

• hydrostatic pressure in IF: 0mmHg into capillary

• osmotic pressure in IF: 1mmHg out of capillary

net filtration is occurring at the arteriolar end of the capillary, while reabsorption is taking

place at the venous end of the capillary

describe what “filtration” and” reabsorption” is

filtration: fluids are forced through capillary walls, leaving proteins and cells behind

• WBC leaves from venules, does not leave from capillaries

reabsorption: fluids move back into capillary

what happens with fluid that is lost from the capillaries

not all fluid filtered out of the capillaries gets reabsorbed at the venous end (20L of fluid from capillaries at their arteriolar end and flows through interstitial space; 17L is reabsorbed back to venous end)

• lymphatic system picks up extra fluid 

define edema

describe potential causes of an edema

edema: abnormal increase in amount of interstitial fluid

• an increase in outward pressure (driving fluid out of the capillaries)

• a decrease in inward pressure

• a decrease in drainage of interstitial fluid through lymphatic vessels

describe the general functions of the pulmonary and systemic circuit

pulmonary circuit: moves blood between heart and lungs

• turn deoxygenated blood into oxygenated blood

systemic circuit: move blood between heart and body

• deliver oxygen and nutrients into body