Cardiovascular

Veins 4

•Factors which enhance venous return 1.Driving pressure from cardiac contraction 2.Sympathetically induced venous vasoconstriction 3.Skeletal muscle activity 4.Effect of venous valves 5.Respiratory activity 6.Effect of cardiac suction

Lymphatic System 2

•Functions 1.Return of excess filtered fluid 2.Defense against disease •Lymph nodes have phagocytes which destroy bacteria filtered from interstitial fluid 3.Transport of absorbed fat 4.Return of filtered protein

•Heart implies force -> Pressure

-The pressure is then lost due to resistance, therefore pressure drops -Pressure is initially high and this establishes the pressure gradient -The greater the pressure gradient is the greater the flow.

•Viscosity

-Viscosity (h) is the friction of the molecules of fluid as they slide over each other during flow -Increased viscosity à increased resistance -Viscosity is determined primarily by the # of RBC which is normally constant

•As resistance increases the flow decreases -Depends on 3 things:

1.Blood viscosity 2.Vessel length > surface area 3.Vessel radius

Fluid Exchange 2

1.Diffusion: concentration of the blood is carefully regulated to maintain the proper concentration of individual solutes to promote movement in the opposite direction. That is O2 CO2 • •The capillary doesn't regulate the movement of any solute except for plasma proteins. • •Therefore, the extent of diffusion is determined by the concentration gradient.

Fluid Exchange 3

2.Bulk flow •Bulk flow occurs because of the difference of hydrostatic pressure and colloid osmotic pressure - •A volume of protein-free plasma filters out of the capillary and mixes with the surrounding ECF, and then moves back in. (Reabsorbed) • •Fluid is moving in bulk à capillary wall act like a sieve à when the pressure inside is greater than the pressure outside = ultrafiltration (HYDROSTATIC) • •Most proteins are contained within the capillary and this creates and inward pressure = reabsorbtion (OSMOTIC)

Fluid Exchange 6

3.Interstitial fluid hydrostatic pressure (Pif) •pressure of the interstitial fluid to push back into the vessel. - 4.Interstitial fluid colloid osmotic pressure (pif) -Osmotic force to draw fluid out of the vessel. (Doesn't normally contribute much) -There is a small portion of protein that does leak out and is usually returned by the lymph

Arterioles 4

•Increased sympathetic tone increases resistance. -Causes a decrease in flow downstream and an increase in pressure upstream of the arterioles • •Increased SNS à Increased TPR and with CO constant there is an increase in MAP • • •Why do this? -Why, the increase in MAP (force of blood to the organ) while decrease in Flow?

Fluid Exchange 8

•Net exchange of fluid across the capillary wall -The exchange at any given point across a capillary wall can be calculated by: Outward pressure Inward pressure - •A positive net exchange pressure indicates ultrafiltration •A positive net exchange pressure indicates reabsorbtion

Arterioles 6

•Nor's influence on arteriolar smooth muscle • •Nor comes from the sympathetic nerve ending -binds to a1 receptors à vasoconstriction • •There are no cerebral a1 receptors -Therefore no SNS control of cerebral resistance. -It's almost entirely controlled by local mechanisms • •There is no parasympathetic innervation of arterioles. -Except reproductive organs.

Blood flow (F) through a vessel depends on the pressure gradient (ΔP) and the

vascular resistance (R).

Arterioles 3

•Arteriolar walls are surrounded by smooth muscle that is innervated by the sympathetic postganglionic -Smooth muscle sensitive to SNS -Sensitive to local factors -Circulating hormones -Mechanical stretch - - - •Smooth muscle runs circularly around the arteriole • •Vascular tone: A state of partial contraction that creates a baseline resistance •2 Factors determine tone; 1.Presence of Ca2+ channels that allow cytosolic Ca2+ in and contractility to occur 2.Continuous release of Nor from sympathetic endings • •Vascular tone makes it possible that you can either increase or decrease pressure on need

Arterioles 1

•Arterioles are the major resistance vessels and cause the largest drop in mean pressure -MAP = 93 mmHg entering the arterioles and 37 exiting arterioles • •Also converts the pulsatile systolic and diastolic pressure in the arteries into non-fluctuating pressure in the capillaries

Mean Arterial Pressure 2

•Average pressure driving blood forward into tissues throughout cardiac cycle It is not the halfway point between the systolic and the diastolic pressure Why, AP remains closer to diastolic than to systolic pressure for a longer period of time. •Formula for approximating mean arterial pressure MAP = diastolic + (⅓ pulse pressure) Ex; 120/80; MAP = 80 mmHg (diastolic)+ ⅓ (40 mmHg) = 93 mmHg

Blood Flow

•Blood flow is in parallel -all organs receive fresh blood • •Blood is constantly reconditioned so composition remains relatively constant • •Reconditioning organs receive more blood than needed for metabolic needs -Digestive organs, kidneys, skin -Adjust extra blood to achieve homeostasis •Blood flow to other organs can be adjusted according to metabolic needs • •Some organs can tolerate reduced blood flow better and longer than other organs. -Brain can least tolerate disrupted supply

Mean Arterial Pressure 1

•Blood pressure is monitored and regulated in the body • •Primary determinants -Cardiac output -Total peripheral resistance -Volume (remains constant) • •Mean arterial pressure = cardiac output x total peripheral resistance MAP = CO x TPR

Arterioles 7

•Cardiovascular control center -In medulla of brain stem -Integrating center for blood pressure regulation • •Other brain regions also influence blood distribution -Hypothalamus •Controls blood flow to skin to adjust heat loss to environment • •Hormones that influence arteriolar radius -Adrenal medullary hormones •Epinephrine and norepinephrine -Generally reinforce sympathetic nervous system in most organs •Vasopressin and angiotensin II Important in controlling fluid balance

Capillaries 4

•Contraction of sphincters reduces blood flowing into capillaries in an organ • •Relaxation of sphincters increases blood flow • •Metarteriole -Runs between an arteriole and a venule •Under resting conditions many capillaries are not open • •Capillaries surrounded by precapillary sphincters • •Role of the precapillary sphincter; -They are not innervated but they do have a great deal of myogenic tone and are sensitive to local and metabolic changes -Sphincters act as stopcocks to the capillary and capillaries have no smooth muscle.

Arterioles 8

•EPI and NOR -Sympathetic activation of the adrenal medulla causes the release of EPI and NOR. • a1 = constriction b2 = dilation • •NOR activates a1 receptors à vasoconstriction −a1 receptors are located on arteriolar smooth muscle in all tissue except the brain. • •EPI activates a1 and b2 with high affinity for the b2 àvasodilation • •Not all tissue have b2 receptors. -Its mainly abundant in the arteriolar smooth muscle on coronary arteries of the heart, lung and the skeletal smooth muscle and causes dilation

Capillaries 3

•Endothelial cells are closely joined with narrow water filled pores that permit the passage of small, water-soluble substances -Gaps that lie at junctions between cells • •Lipid soluble substances readily pass through endothelial cells by dissolving in lipid bilayer barrier

Vascular Tree Consists of

-Arteries •Carry blood away from heart to tissues -Arterioles •Smaller branches of arteries -Capillaries •Smaller branches of arterioles •Smallest of vessels across which all exchanges are made with surrounding cells -Venules •Formed when capillaries rejoin •Return blood to heart -Veins •Formed when venules merge Return blood to heart

•Surface Area

-Blood cells rub and bump the vessel wall and this creates resistance. -More surface area à more resistance. -Determined by the vessels length and radius -At constant radius the longer the vessel is the greater is the surface area -therefore increased resistance. -However, length is constant and therefore not a factor -Therefore, the main factor is the radius. •If the radius is large there will be low resistance and less contact against the walls.

•Flow rate through a vessel (volume of blood passing through per unit of time)

-Directly proportional to the pressure gradient -Inversely proportional to vascular resistance

R is proportional to 1/r4

-Major determinant of resistance to flow is vessel's radius (r). -Slight change in radius produces significant change in blood flow

•Diastole

-Minimum pressure in arteries when blood is draining off into vessels downstream -During diastole no more blood enters the arteries. •The elastic recoil and pressure continues to push the blood into the arterioles. -Minimum pressure in the arteries while the blood is draining into the downstream vessels is Diastolic pressure (~ 80 mmHg)

•Systole

-Peak pressure exerted by ejected blood against vessel walls during cardiac systole -During systole blood enters the arteries. Only about 1/3 is available to leave the arteries and enter the arterioles -Maximum pressure exerted into the arteries during systole is Systolic Pressure (~120 mmHg)

Arterioles 5

Ans. It allows us to shunt blood to the appropriate area of need. • •If TPR increases and à increase in MAP, you can then dilate a specific tissue and have increase flow to that specific tissue

MAP =

CO x TPR

A small change is vessel radius brings about a large change in vessel flow because resistance is inversely proportional to the 4th power of the radius.

Doubling the radius will increase the flow by 16 fold because you reduce the resistance by 1/16

Veins 5

Effect of skeletal muscle activity •Countering the effects of gravity. -Lye down and pressure is evenly distributed. Stand and pressure to the brain decreases above the heart and increases below the heart •Veins increase capacity under increased pressure and blood pools in the lower extremities -Venous return is reduced and therefore decrease in CO occurs. This leads to decreased circulation

•In regards to the circulatory system as a whole:

F = CO R = TPR DP = MAP for the System Mean pressure in aorta = 93 & mean pressure in R Atrium = 0. Therefore DP = MAP = 93)

F =ΔP R

F = flow rate of blood through a vessel ΔP = pressure gradient R = resistance of blood vessels

CO =

HR X SV

Smooth Muscle cardiovascular 1

Located mainly in the walls of hollow organs and maintains the size and shape Small spindle-shaped cells with a single nucleus vs. large multinucleated skeletal muscle. Lack a neuromuscular junction. ANS cells release neurotransmitter via varicosities and neurotransmitter diffused to the receptor site. Single-unit smooth muscle cells are connected via gap junctions. Multi-unit smooth muscle cells are not electrically connected and therefore must be activated by neurotransmitter directly

Pressures, Resistances, and Volumes in advance

Mean Arterial Pressure (MAP) = diastolic + (⅓ pulse pressure) Mean Systemic Pressure Central Venous Pressure (cardiac filling pressure) Cardiac Output Stroke Volume Total Peripheral Resistance (or Systemic Vascular Resistance) Venous Return Venous Compliance

Smooth Muscle cardiovascular 2

More actin in smooth muscle cells and no troponin and less Sarcoplasmic reticulum. Actin and myosin are not arranged in Sarcomeres, instead they are arranged in long diagonal bundles where they surround the cell. Long actin filaments attach to dense bodies that adheres them to the cell membrane.

Veins 7

Respiratory activity -Pressure in the chest cavity is about 5 mmHg lower than atmospheric. In the lower extremities there is normal pressure and this produces a driving force for blood to move up to increase the vacuous return ● Cardiac Suction -Ventricular contraction pulls on the atria and enlarges then drawing the blood in. Therefore, atrial pressure is transiently below zero.

DP =

R x F

Smooth Muscle Cardiovascular 3

Smooth muscle cells have an unstable resting membrane potential called a "slow-wave potential" in which there is a cyclic depolarization and repolarization. Pacemaker potentials; if the peak of the potential reaches threshold action potentials fire

Fluid Exchange 5

There are 4 factors that influence the movement 1.Capillary blood pressure (Pcap) •The outward fluid pressure exerted on the outside of the capillary wall and tends to push fluid out of the capillary • 2.Plasma colloid osmotic pressure (pp) •Determined by the protein concentration within the vessel it encourages movement of flow into the capillaries and retards the outward hydrostatic pressure.

Fluid Exchange 4

There are 4 factors that influence the movement 1.capillary blood pressure (Pcap) 2.plasma colloid osmotic pressure (pp) 3.Interstitial fluid hydrostatic pressure (Pif) 4.Interstitial fluid colloid osmotic pressure (pif)

Vascular Tree

Vascular tree is a "closed system of vessels" Arteries branch and diverge from the heart -> they progressively diverge into a tree of smaller and smaller vessels -> arterioles further branch into capillaries

Veins 6

Venous Valves: one-way valves assist in venous return Skeletal muscle pump "interrupts" the column of blood so that all of the blood isn't exerting pressure in the whole lower half

Poiseuille's Law;

p = 3.142 DP = Change in pressure r = radius h = viscosity l = length

Lymphatic System 1

•Normally there is a little more fluid that is filtered than reabsorbed. -This excess is picked up by the lymphatic like a "storm sewer" • •Initial lymphatic, small terminal lymph permeate almost every tissue of the body • They overlap and form a 1-way valve

Fluid Exchange 1

•Only about 20% of the ECF is plasma, the other 80% bathes cells • •Movement across the capillary is mainly passive. • •Exchanges between blood and tissue across the capillary wall are accomplished in two ways. 1.Passive diffusion down the concentration gradient Bulk Flow

Arterioles 2

•Radius supplying individual organs can be adjusted independently to 1.Distribute cardiac output among systemic organs, depending on body's momentary needs 2.Help regulate arterial blood pressure • •Mechanisms involved in adjusting arteriolar resistance -Vasoconstriction •Refers to narrowing of a vessel -Vasodilation •Refers to enlargement in circumference and radius of vessel •Results from relaxation of smooth muscle layer •Leads to decreased resistance and increased flow through that vessel

Capillaries 1

•Sites of exchange between blood and surrounding tissue cells • •The capillary walls are thin, it's a single layer of endothelia. • •2 types of passive exchanges 1.Diffusion 2.Bulk flow

Arteries

•Specialized to 1.Serve as rapid-transit passageways for blood from heart to organs •Due to large radius, arteries offer little resistance to blood flow 2.Act as pressure reservoir to provide driving force for blood when heart is relaxing •When the heart is not contracting there is no blood being pumped, however there is blood flow.

Edema

•Swelling of tissues • •Occurs when too much interstitial fluid accumulates • •Causes of edema -Reduced concentration of plasma proteins -Increased permeability of capillary wall -Increased venous pressure -Blockage of lymph vessels

Capillaries 2

•The velocity of blood at different regions varies. • •Velocity of flow is inversely proportional to the total cross-sectional surface area of the vessel • •The total cross sectional area of the capillaries is about 750X greater than the aorta. • •The same volume of blood passes through both. • •So, blood slows considerably and this allows time for diffusion of O2 C O2 and nutrients

Fluid Exchange 7

•There are two pressures that tend to push fluids out of the capillary: 1.Capillary blood pressure (Pc) 2.Intestinal fluid colloid osmotic pressure (pif, negligible) • •The two forces that tend to push fluid in are: 1.Plasma colloid osmotic pressure (pp) 2.Interstitial fluid hydrostatic pressure (Pif)

Fluid Exchange 9

•Ultrafiltration occurs at the beginning of the capillary bed as outward pressure forces the protein-free filtrate out of the capillary • •By the time the venule at the end of the capillary bed is reached the capillary blood pressure has dropped but the other pressures have remained constant and then reabsorbtion occurs • •The process of ultrafiltration and reabsorbtion is "bulk flow" • •This is a continuous and gradual process and very important in ECF distribution throughout the body. v plasma volume -> ^ capillary BP -> D bulk flow forces. No D in the inward pressure & v outward pressure -> ultrafiltration & reabsorbtion. -> Fluid is shifted from the ECF interstitial compartment to the plasma.

Veins 2

•Veins store blood, they act as capacitance vessels. -There is little myogenic tone and low elasticity, therefore, they are highly distensible and have little recoil ability • •They easily distend to accommodate large volumes of blood with only a small increase in venous pressure. -Thus, veins = blood reservoir. -Blood in this area is not stagnant, it's just in a larger volume when accommodating • •When needed, you can decrease the capacity of the venous side à increased venous return à increased CO in accordance with Starling law • •Factors that effect venous capacity -Venous capacity depends on 1.Compliance of the vein walls 2.The influence of externally applied pressure squeezing inwardly on the veins

Veins 3

•Venous return refers to the amount of blood that makes it back to the right atrium • •Sympathetic activation -> modest increase in venous pressure -> increased return Also, 1.sympathetic activation -> decreased venous capacity 2.sympathetic activation -> more blood pumped out of the heart -> more blood back to the heart • •Arteriolar vasoconstriction immediately reduces flow due to increased resistance • •Venous vasoconstriction immediately increases flow through the vessels because of the decrease in capacity

Veins 1

•Venous system transports blood back to heart • •Capillaries drain into venules • •Venules converge to form small veins that exit organs • •Smaller veins merge to form larger vessels • •Veins -Large radius offers little resistance to blood flow -Also serve as blood reservoir

Resistance

•is measure of opposition of blood flow through a vessel. • •It's caused by the friction of the moving fluid and the stationary vascular walls

Pressure gradient (ΔP)

•is pressure difference between beginning and end of a vessel -Blood flows from area of higher pressure to area of lower pressure