A & P II Unit 3 - Lesson 10 CHECK OFF

Describe the factors that can affect tissue perfusion. Which are short term? Which are long term?

( tissue perfusion is blood flow thru the tissues, carrying O2 and nutrients to tissues and organs and carrying CO2 and wastes away) Affected by: - Both *Cardiac output* & = - *Blood pressure* = auto regulation, neural mechanism (short-term) and Endocrine mechanism (long-term) - Peripheral resistance ( short-term because auto regulation?)

Describe how blood flow to the brain and lungs are regulated:

*BRAIN:* when peripheral vessels constrict, cerebral vessels dilate, normalizing blood flow during a cardiovascular crisis. *LUNGS:* regulated by O2 levels inside alveoli (air sacs in lung tissue where gas exchange occurs) - High O2 content / vessels dilate - Low O2 content / vessels constrict

Describe the age related changes to the heart and blood vessels:

*HEART:* 5 1. Reduced maximum cardiac output 2. Changes in nodal and conducting cells 3. Reduced elasticity of cardiac (fibrous) skeleton 4. Progressive atherosclerosis 5. Replacement of damaged cardiac muscle cells by scar tissue *BLOOD VESSELS:* 3 1. Arteries become less elastic - pressure change can cause aneurysm 2. Calcium deposits on vessel walls - can cause stroke or infarction 3. Thrombi can form - at atherosclerotic plaques

Explain how the cardiovascular system responds to exercise:

*Light Exercise:* - Extensive vasodilation occurs, increasing circulation. - Venous return increases with muscle contractions. - CO rises (venous return / atrial stretching) *Moderate Exercise:* - Lowers total blood cholesterol levels (helps more low-density lipoproteins (LDL's) from blood to liver) *Heavy Exercise:* - Activates sympathetic nervous system - CO increases to max. 4x resting level - Restricts blood flow to "nonessential" organs (eg. digestive sys.) - Redirects blood flow to skeletal muscles, lungs, and heart - Blood supply to brain is unaffected *Intense Exercise:* - Can cause sever physiological stress (lead to acute disorders - kidney failure, arrhythmia, MI, etc.) - No evidence that it lowers risk of cardiovascular disease

Describe the various local vasodilators and vasoconstrictors:

*local vasodilators* accelerate blood - flow at tissue level: - low O2 or high CO2 levels - low pH (lactic acid) - nitric oxide (NO) - high K+ or H+ concentrations - chemicals released by inflammation (histamine) - elevated local temperature *local vasoconstrictors* ex. prostaglandins and thromboxanes : - released by damaged tissues - constrict precapillary sphincter - affect a single capillary bed

Describe the hormones that can affect blood pressure/volume:

1. ADH - "antidiuretic hormone"; *elevates blood pressure* / *reduces* water loss at kidneys. Responds to: *low blood volume*, high plasma osmotic concentration, and circulating angiotensin II. 2. Angiotensin II - *responds to fall in renal (kidney) blood pressure*. stimulates: aldosterone production from adrenal cortex, ADH production, thirst, and cardiac output and peripheral vasoconstriction. 3. EPO - released at kidneys, responds to *low* blood pressure, low O2 content in blood, stimulates RBC production, stimulates vasoconstriction of blood vessels. 4. ANP / BNP - respond to excessive diastolic stretching (*too much blood volume* in heart chambers during relaxation), *during lower blood volume and blood pressure*: promotes H2O loss, inhibits ADH, aldosterone, NE and E.

Describe the diffusion routes taken by different molecules at capillaries:

1. Water, ions, and small molecules like glucose are diffused between adjacent endothelial cells or diffused through *fenestrated capillaries* (rapid exchange). 2. Some ions (Na+, K+, Ca2+, Cl-) diffuse through channels in plasma membranes. 3. Large, water-soluble compounds pass through *fenestrated capillaries*. 4. Lipids and lipid-soluble materials such as O2 and CO2 diffuse through endothelial plasma membranes. (continuous capillaries) 5. Plasma proteins cross endothelial lining in *sinusoids* (ex. sinusoidal capillaries in the liver)

Explain what happens at the capillaries:

Capillary pressures and capillary exchange is very vital to homeostasis. capillaries move materials across their capillary walls by diffusion, filtration, and reabsorption.

Explain how blood pressure and resistance impact blood flow:

Cardiac output (= total capillary blood flow) Capacitance (Stretch / veins) Volume of the blood Viscosity of the blood Blood vessel length and diameter

Explain the difference between filtration and reabsorption at the capillaries:

Filtration: - driven by *hydrostatic pressure* (from an area of high pressure to area of low pressure) - water and small solutes forced thru capillary wall - leaves larger solutes in bloodstream Reabsorption: - result of *osmotic pressure (OP)* -- mainly BCOP (draws fluid back into capillaries) reabsorption equals pressure required to prevent osmosis and is caused by suspended blood proteins that are too large to cross capillary walls

Explain how the mean arterial pressure is calculated:

MAP = diastolic pressure + 1/3 (pulse pressure) MAP = (minimum arterial pressure during diastole *remember 80 in 120/80) + 1/3 ( systolic - diastolic pressure)

What is the CHP, BCOP, IHP, and ICOP?

NET HYDROSTATIC PRESSURE: CHP = Capillary hydrostatic pressure IHP = Interstitial fluid hydrostatic pressure -- tends to push water and solutes out of the capillaries and into interstitial fluid NET CAPILLARY COLLOID OSMOTIC PRESSURE: BCOP = Blood colloid osmotic pressure (BCOP) ICOP = interstitial fluid colloid osmotic pressure -- which pulls water and solutes into capillary and from interstitial fluid

Explain the function of the baroreceptors:

Respond to changes in blood pressure: When blood pressure rises, CV centers: - decrease CO - cause peripheral vasodilation - results in reducing BP When blood pressure falls, CV centers: - increase CO - cause peripheral vasoconstriction - results in increasing BP

Describe the chemoreceptor reflexes:

Respond to changes in chemical composition, particularly pH and dissolved gases: *peripheral* chemoreceptors are located in carotid bodies and aortic bodies to monitor blood. *central* chemoreceptors are below medulla oblongata to: - monitor CSF - control respiratory function - control blood flow to brain *changes in pH, O2, and CO2 concentrations* produced by coordinating cardiovascular and respiratory activities.

Explain the mechanisms in the venous system that assist the movement of blood back to the heart:

Two mechanisms: 1. *Muscular compression of peripheral veins* = compression of skeletal muscle pushes blood towards the heart (one-way valves). 2. *The Respiratory Pump* = inhaling decreases thoracic pressure and pulls air into the lungs and blood into the interior vena cava. When exhaling raises, it increases thoracic pressure and pushes venous blood into the right atrium.

Explain which vessels provide the most resistance:

arterioles

Explain how you can determine if filtration is occurring or reabsorption:

filtration uses hydrostatic pressure, meaning that they take the blood FROM the capillaries, leaving the large solutes behind, and into the interstitial fluids. reabsorption tries to prevent osmosis and suspend blood proteins that are too large.

Describe how the net filtration pressure is calculated:

it is the difference between net hydrostatic pressure and net osmotic pressure: NFP = (CHP - IHP) - (BCOP - ICOP). remember: IHP and ICOP normally are equal to each other simplifying the equation to : NFP = (CHP - BCOP)

Describe how blood pressure is maintained by elastic arteries:

the arterial walls stretch during systole, rebound (recoil to original shape) during diastole, and keep blood moving during diastole. the BP is maintained by decreasing with friction, but by the time blood reaches capillary sphincter, pressure fluctuations are no longer present.

Explain where baroreceptors are located:

they have stretch receptors in walls of : 1. Carotid sinuses (maintain blood flow to brain) 2. Aortic sinuses (monitor start of systemic circuit) 3. Right atrium (monitors end of systemic circuit) - used in Bainbridge reflex to increase heart rate.