Phys. Ch.10
blood pressure
4 things force systolic pressure diastolic pressure puse difference
Local (intrinsic) control of arteriolar resistance
Ability of organs to alter their own arteriolar resistance to adjust pressure and blood flow according to their momentary needs Organs can Decrease resistance increase flow Each control valve represents smooth muscle
Intrinsic control of arteriolar radius
Increased metabolic activity changes the cellular concentrations of various chemicals Active hyperemia - increased blood flow in response to increased metabolic demands (hyper = above normal, -emia = blood) Decreased O2 Increased CO2 Increased acid Decreased ATP If cell/organ has extra metabolism going on it will release chmicals that will go to blood vessels, flow to tissue will be increased Increase in blood flow due to increase in metabolic demands=active hyperemia If tube gets bigger, blood flow goes up and resistance decreases
capillaries
the smallest vessels across which all exchanges are made every cell in body has to be in contact with 1 capillary
mean arterial pressure
Average pressure over the length of one cardiac cycle Cardiac cycle = diastole + systole MAP is the driving pressure propelling blood forward into tissues **MAP = diastolic pressure + 1/3 pulse pressure For a BP of 120/80, MAP = 80 + 1/3 (120-80) = 93.3 mmHg MAP describes pressure over entire cycle Systole followed by disatole Driving force for blood flow Diastole lasts about 2/3 of the time Systole lasts about 1/3 of entire cycle
starling forces explained
BEG. Of cap- hydrostatic pressir high blood pressure, as we move along cap, pressure drops, a lot of resistance in cap. From arteriole to venule end it drops blood pressure is very low in venule Osmotic-plasma proteins can never leave cap, pores too small fOR PRO, this pressure will never change Drivng force moving out is stronger than force moving in=filtration Continue until halfway pt.= osmotic is greater than hydrost. Force moving in is greater than force moving out so its reabsorption On venule side its reabsorption Filtration-driving fluid out of cap
Distribution of cardiac output at rest
Blood pumped by left heart is distributed in parallel Large percentage of blood at rest sent to organs to "recondition" blood Digestive, kidney, skin Smaller percentage of blood sent to organs that only need blood for metabolic needs Blood flow can be adjusted as needed according to metabolic needs Parallel- fractions of blood from heart go to diff areas of body Fifth of blood is going to kidneys and digestive system
Bulk flow (aka "Starling forces")
Bulk flow: movement of water AND solutes TOGETHER as a result of a pressure difference Filtration: fluid leaves capillary Reabsorption: fluid re-enters capillary What pressure are we talking about above? It's the sum of the: Hydrostatic pressure: pressure exerted by fluid on capillary wall (blood pressure) and Osmotic pressure: pressure exerted by osmotically active proteins inside blood Filtration- leave cap move into surroudning tissues Reabsorp. Entering cap Driven by pressures Hydrostatic-blood pressure Osmotic pressure- drives fluid into cap created by presence of PRO in blood
monitoring mean arterial pressure
Constantly monitored by baroreceptors within the circulatory system Short-term control adjustments Initiated by the baroreceptor reflex Effects can be measured within seconds Adjustments made by alterations in CO and TPR Long-term control adjustments Effects not measured for minutes to days Involve adjusting total blood volume by restoring normal salt and water balance through mechanisms that regulate urine production and thirst Baroreceptors monitor pressure Short term- initated by baroreceptors change in blood pressure within seconds Long term- days weeks, months, years Changing how much blood is in circulatory system Hormones involved wont go into detail rn
pulse difference
Difference between systolic and diastolic pressures Averages 40 mmHg pulse pressure: systolic minus diastolic
Pressure gradient
Difference in pressure between the beginning and end of a vessel Blood flows from areas of high pressure to low pressure Contraction of the heart main driving force for flow through a vessel Due to resistance, pressure drops along vessel's length Drives blood flow High pressure at beg of tube and then loses pressure Vessel 2 will have a higher flow rate Pressure gets reduced as it moves along vessel bc u lose pressure due to resistance
Arterioles
Distribute cardiac output by adjusting their radius to alter blood flow to individual organs Largely determine MAP Thick layer of smooth muscle Innervated by sympathetic nerve fibers (extrinsic) Sensitive to local chemical (intrinsic) and hormonal changes (extrinsic) Main controller of how much blood gets distrubuted to each organ Contracting and relaxing the middle smooth muscle Smooth muscle contracts muscle gets smaller When it relaxes the muscle gets bigger Vessel controlled by nervous system-extrinsic Rings are smooth muscle (in pic)
starling forces
Drive bulk flow into cap or out of cap High pressure to low -hydro.. Pushed fluid out of cap thru pores of cell that make up lining of cap Osmotic-created by osmotically active partic. Which are PRO Pulls water into CAP=REABSOPR. Capillary hydrostatic pressure (PC) favors movement of water out of the capillary (filtration) Capillary osmotic pressure (πC) favors movement of water into the capillary (reabsorption)
cont
Endothelial cells are the inner lining of blood vessels Release chemicals that affect arteriolar radius Nitric oxide (NO) prevents phosphorylation of myosin light chain in vascular smooth muscle Injury causes local release of chemicals Histamine (from WBC) causes vasodilation Increase in blood flow results in redness and swelling Endothelin (from endothelium) causes vasoconstriction Response to damaged vessels Nitric oxide dialates blood vessels makes the flow increase Want vasoconstriction with a messed up vessel so that you don't lose blood
Extrinsic (sympathetic) control of arteriolar radius
Extrinsic factors concerned with whole body BP regulation, rather than local changes Accomplished primarily by sympathetic NS Regulates HR and SV (as we saw in Chapter 9) Regulates total peripheral resistance Always refer back to this equation Increasing any one of the three things listed above increases MAP
Factors affecting flow through a vessel
Flow rate through a vessel is directly proportional to the pressure gradient and inversely proportional to the vascular resistance Ml/min or L/min As flow rate goes up, the pressure gradient will also go up Resistance goes up, flow rate goes down
lymph drainage
Lympth vessels take fluid to lymph nodes where it gets cleaned and thengets put back to veins and then goes to the right side of the heart 20 L of fluid a day leaking out of caps 17 L fluid a day going back to caps 3 left over goes to lymphatic vessels where they will be cleaned and back to blood
Regulation of arterial blood pressure
Mean systemic arterial pressure is product of cardiac output and total peripheral resistance (TPR; sum of all the resistances in the systemic vessels) Any changes in pressure must be result of changes in these factors Intrinsic and extrinsic control of resistance Remember F = ΔP/R? It can be rearranged to ΔP = F x R ...or: This equation is importat Anytime blood pressure changes, it's a result of a change in CO or TPR
resistance
Measure of the opposition to blood flow in a vessel Caused by friction To maintain constant flow when ΔP decreases, R must also decrease Depends on three things Blood viscosity Vessel length Vessel radius Small changes in vessel radius brings large changes in flow Resists flow of blood Vessel with small radius is small With large/wide radius is large Changing radius results in massive differences in flow bc its to the 4th power
measuring blood pressure
Measured indirectly using a sphygmomanometer Korotkoff sounds Sounds heard when determining blood pressure Not the same sounds produced by valve closure when listening to the heart
baroreceptor reflex
Mechanoreceptors (receptors) located in the walls of the aortic arch and carotid sinus Stretching of vessel wall increases firing rate of action potentials (afferent) to cardiovascular control center (integration) Results in alteration of autonomic activity (efferent) to cardiovascular system (effector organs) Detecting how much blood vessels stretch.. Think about water balloon ex. Increase pressure, stretching As pressure increases wall of arteries will stretch and barorecept. Can tell how much the wall is stretching Heart rate increases and increased stretch and barorecp. Will signal AP'S which will go to brain Barorecept. Will reduce number of AP's it sends when we decrease pressure Might lower resistance by decreasing pressure in blood vessels
diastolic pressure
Minimum pressure exerted by ejected blood during ventricular diastole(ventricular filling) Averages 80 mmHg
arteries
Move blood away from heart Large radius makes for little resistance to blood flow Elasticity drives flow when heart is relaxing = pressure reservoir Connective tissue layer Collagen fibers for strength Elastic fibers for elasticity Substantial energy required to stretch walls (left ventricle) Distension provides energy for elastic recoil Top vessel has the most resistance so not a lot of flow within it Elastin fibers- stretchy proteins, snap back into place Elasticity when vessel snaps back into place Distension adds a little more to get the blood flowing?
cont
No parasympathetic innervation of arterioles Exception: erectile tissues of penis and clitoris Cardiovascular control center in medulla controls sympathetic output Sympathetic nervous system Norepinephrine released from sympathetic postganglionic nerves Norepinephrine and epinephrine released from adrenal gland NE and Epi initiate vasoconstriction in most blood vessels Most vessels will constrict in response to NE and eprinephrine
Sympathetic activity alters arteriolar radius cont
On arterioles supplying skeletal/cardiac muscle: Sympathetic neurons release norepinephrine on arteriolar smooth muscle NE binds to β2 receptor on smooth muscle ->dilation (increased flow) Dialate and increase blood flow to heart and skeletal muscle during sympathetic nerves
calculating net exchange pressure
Outward pressure-water out of cap Inward pressure-water in cap Cant have all the fluid get into interstitial fluid Greater pressure for fluid to leave then for it to come back in near venule side Net exchange pressure = PC - πc PC=outward pressure other one: inward pressure
systolic pressure
Peak pressure exerted by ejected blood during ventricular systole Averages 120 mmHg Minimum of 70 mmHg for perfusion of brain, kidneys Systolic pressure- experienced in blood vessels while heart is contracting normally 120 mmHg** If it falls below 70 mmHg everything in your body will start to die and shut down Normal blood pressure: 120/80
pulse pressure
Pressure difference between systolic and diastolic pressure Felt in arteries close to skin surface Example: If blood pressure is 120/80, pulse pressure is 40 mmHg (120 - 80 = 40)
factors enhancing venous return respiratory pump
Pressure in thoracic cavity always 5 mmHg less than rest of body; lower pressure Creates pressure gradient between veins in lower extremities and veins in chest Respiratory pump acts as a vacuum, promoting VR Low pressure... "vacumn" Low pressure areas will suck things towards them When u breathe in, lots of low pressure in thorax, help suck blood thru veins to heart
factors enhancing venous return
Skeletal muscle pump - squeezing of veins by actively contracting skeletal muscle in the legs Similar physics to vasoconstriction Venous valves - ensures unidirectionality of blood flow in veins Pump- when muscles contract they'll squeeze veins/contract muscles and blood will wanna shoot in both directions, larger veins in lower extrem. Have valves.. 1 way valves... vasoconstrict vein and valves prevent blood from going backwards have to take blood against gravity & (foot and ankle etc.)
capillaries
Smallest of the blood vessels (8-10 um diameter) All cells must be in contact with at least one capillary Most capillaries are continuous Narrow, water-filled pores between cells Routes of capillary permeability Through endothelial cells via direct diffusion (lipid-soluble molecules = O2, CO2) Through pores (small molecules = ions, glucose, AAs; no proteins) Through cytoplasmic vesicles (large molecules, small proteins) Two types of passive exchange Diffusion Bulk flow through pores Um=microns Have to pass thru caps 1 at a time, blood flow will be slow enough so diffusion will fully occur; if blood happened too fast, o2 would'nt be able to get in Pores are goood for things to get out of caps Direct diffusion- anything nonpolar and fatty and get thru Proteins are too large to fit thru pores Proteins get in and out of blood by wrapping around membrne and getting out on other side (exo and phago cytosis)
Sympathetic activity alters arteriolar radius
Sympathetic neurons release norepinephrine on arteriolar smooth muscle NE binds to α1 receptor on smooth muscle -> contraction Removal of norepinephrine (MAOs) results in relaxation of arteriolar smooth muscle Causes vasoconstriction as a result of NE binding to a1 Shut off signal from nerve with NE and then vessel will dialate Wanna increase blood flow during sypmathetic nerves they still release NE but it binds to b2 receptor and not a1! Different receptor makes a different response
cont.
To hear heart sounds requires: Blood flow Turbulent blood flow Make sure pressure inside of cuff is more than in the blood vessel Listen to beat in artery in arm that you put cuff on. The arteries were stopped and you wanna hear no sound When u get to 120 you start to hear something in stethoscope Korotkoff sounds are the heartbeats in the arteries Don't hear blood flow when it lamina flow
blood vessel anatomy
Three layers Slippery endothelium (inside) Smooth muscle (middle) Strong, flexible connective tissue (outside) Endothesium-group of cells that are very slipper try to reduce amount of friction Middle layer is smooth muscle makes vessel bigger when relaxed and constricts when its not relaxed Connective tissue- a lot of collagen- stronger than steel
lymphatic system
Under normal circumstances, more fluid leaks (filtered) out of the capillaries than is put back (reabsorbed) Lymph - interstitial fluid that enters a lymphatic vessel to be returned to the blood Lymph vessels - empty into venous system near where blood enters right atrium Lymph nodes - nodules containing lymphocytes (a type of white blood cell) through which lymph passes Interstitial fluid left over that enters lympatic syst. Is lymph! Take any extra fluid left over-the whole system and it cleans fluid as it passes the fluid back to circulatory system
Adjusting arteriolar radius
Vasoconstriction refers to narrowing a vessel's radius ↑ resistance; ↓ blood flow Results from activation of sympathetic NS Vasodilation refers to lengthening a vessel's radius ↓ resistance; ↑ blood flow Results from inactivation of sympathetic NS Constricting vessel-vasoconstriction If it gets narrower it increases resistance Dilation- gets fatter/wider decreases resistance, and blood flow goes up Inactivate sympathetic nerv system to get wider vessel, activate it to constrict vessel
venous circulation
Venous return (VR) - volume of blood entering right atrium per minute What does ↑VR do to EDV? SV? CO? Factors that enhance VR Sympathetically-induced venous vasoconstriction (increases pressure gradient for VR) *Arterial vasoconstriction results in ↓ flow (↑ resistance) *Venous vasoconstriction results in ↑ flow (↓ capacity) Skeletal muscle pump Effect of venous valves Respiratory activity End diastolic volume will increase if VR increases, stroke volume will increase as well and the CO will also increase venous return=CO! Can constrict veins Blood flow goes up! Veins are at low pressure which helps push blood to heart... like a concentration gradient
veins
Venous system *transports blood back to the right side of the heart Capillaries drain into venules that converge to form small veins that exit organs Smaller veins merge to form larger veins that drain into the right atrium Larger veins serve as blood reservoir ("capacitance vessels") Large compliance (easily distended) Larger lumen that arteries of comparable size 60% of blood in veins at any one time Veins like to store blood Veins can be stretched Pressure in veins is very low
veins
formed when venules merge to return blood to the heart
arteries
carry blood away from heart to tissues
force
exerted by blood against a vessel wall Depends on: Volume of blood contained in the vessel Compliance (distensibility) of vessel wall
Distribution of CO during maximal exercise
increase CO when exercising bc theres more of a demand for blood throughout your body heart rate gets higher and stroke volume gets higher as well 25 L goes to most of skeletal muscle*
venules
small veins formed when capillaries rejoin
arterioles
smaller branches of arteries within organs
