Circulation: Components and Control

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Circulation Components and Control

• Vessels, Blood, Blood Pressure, Regulation, Heart
  Disease, Clotting

AP Biology Unit 6
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Blood Flow through Vessels

• Arteries (and arterioles)
• Thick, muscular walls
• Walls also contain collagen and elastic fibers
  (make them stretchable)
• Can be constricted or dilated

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Blood Flow through Vessels

• Veins (and venules)
• Thinner walls
• one-way valves to prevent blood from flowing
  backwards
• Blood in veins is moved by the contractions of
  skeletal muscles around them (milking)

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Blood Flow through Vessels

• Capillaries
• Thin walls (usually one cell layer thick)
• Permeable to water, ions, other small molecules
• Blood flows slowly through them (red blood cells
  often have to travel single file)
• Every cell in the body is close to at least 1
  capillary

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Capillaries

• Capillaries must exchange materials between the
  blood and the interstitial fluid
• Blood pressure and osmotic pressure drive the
  movement of molecules into and out of capillaries
  
• Blood pressure forces water and solutes out (on
  the artery side)
• Osmotic pressure (due to the proteins left in the
  capillaries) causes water to flow back into the
  capillaries by osmosis

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Question

• How does the structure of each type of vessel
  support its function?
• Arteries thick walls can withstand pressure from
  heart pumping blood
• Veins- valves help prevent backflow since the
  heart is too far away to provide forward pressure
  (to push the blood back to the heart)
• Capillaries- very thin walls allow for easy
  exchange with the interstitial fluid

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Blood Pressure

• Blood pressure the force being applied to the
  blood vessel walls (from blood).
• 2 phases of the cardiac cycle
• Systole when the heart muscle is contracting
• Diastole when the heart muscle is relaxed
  (between contractions)

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Blood Pressure

• Systolic Pressure pressure in arteries when
  heart contracts
• Diastolic Pressure pressure in arteries between
  contractions

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Question

• Giraffes need higher blood pressure. Why?
• Since they are taller, they need more pressure to
  get the blood all the way to the top of their
  bodies

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Control of Circulation

• Heart rate is controlled by
• Nerve impulses sent to SA and AV Nodes
• Hormones (adrenaline/epinephrine)
• Body temperature
• Oxygen requirements due to exercise

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Control of circulation

• The opening of sphincters leading to capillary
  beds is controlled by
• Nerve impulses
• Hormones
• By controlling these sphincters, blood can be
  directed to specific parts of the body under
  stressful conditions

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Control of Circulation

• The Lymphatic System also plays a role in
  controlling circulation
• Maintains fluid levels so blood pressure can
  remain constant
• Lymph fluid (like interstitial fluid, high in
  water and other nutrients)
• Filters body fluids before allowing them to flow
  back into the circulatory system
• Fluids flow out and into capillaries via blood
  pressure and osmotic pressure

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Question

• From what part of the Digestive System did lymph
  flow from?
• Small intestines (lacteals in the villi)

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Components of blood

• Plasma
• Water, nutrients, proteins, ions, etc.
• Cellular Components
• Red blood cells (carry oxygen)
• White blood cells (immune function)
• Platelets (clotting)

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Differentiation of Blood Cells

• Blood cells (RBC, WBC and platelets) all develop
  from stem cells in the red bone marrow.
• Erythropoietin (EPO) is a hormone that promotes
  the production of erythrocytes (RBC)
• Synthesized in the kidneys

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Questions

• When the body is not receiving enough O2, what
  will happen to EPO levels?
• They increase to create more RBC to carry O2
• If a patient is anemic (low iron levels in the
  blood), why might the doctor prescribe synthetic
  EPO?
• Iron is the central part of hemoglobin that
  carries oxygen in RBC

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Question

• How would taking synthetic EPO help with athletic
  performance?
• Having more red blood cells would improve oxygen
  transport abilities ? more endurance

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Blood clotting

• Platelets begin the clotting reaction
• damage in the blood vessel wall exposed collagen
  fibers
• Platelets stick the collagen release substances
  to make other platelets sticky
• Clotting factors released by platelets to
  activate enzymes needed for clotting

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Blood Clotting

• STEPS
• Platelets adhere to the damaged region and become
  sticky? release clotting factors
• Clotting factors cause Prothrombin (inactive) to
  become Thrombin (active)
• Thrombin causes Fibrinogen (plasma protein) to
  become fibrin (active form)
• Fibrin forms threads that help seal the damaged
  area up

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Cardiovascular Disease

• Atherosclerosis narrowing of arteries due to
  plaque build up
• plaque deposits as a result damage to the vessel
  lining
• Plaque desposits narrow the pathway for blood to
  flow
• If the plaque is ruptured it will also cause
  clotting to occur blocks pathway of blood

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Cardiovascular t Disease

• Atherosclerosis can lead to heart attack or
  stroke
• Heart attack blockage in the arteries that
  supply the heart with blood
• Stroke blockage in an artery in the brain

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Heart Disease and Cholesterol

• Cholesterol travels in the blood (plasma)
• Low Density Lipoproteins (LDLs) are associated
  with cholesterol deposits in arteries bad
  cholesterol
• High Density Lipoproteins (HDLs) appear to reduce
  cholesterol deposition good cholesterol
• What seems to matter is the ratio of HDL to LDLs
  in your blood

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Cholesterol and lifestyle choices

• While there is a genetic component to cholesterol
  levels, lifestyle choices also influence it
• Exercise increases HDL levels
• Smoking increases LDL and lowers HDL levels

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