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Aims. Blood clotting (cont.). Coagulation cascade Regulation of blood pressure. Regulation of blood volume. Reading; Sherwood, Chapters 10 &11, Chapter 15 pages 569-570 ; Robbins, pages 84-90. Coagulation Cascade. Very complex >50 substances effect coagulation procoagulants

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slide1
Aims
  • Blood clotting (cont.).
    • Coagulation cascade
  • Regulation of blood pressure.
  • Regulation of blood volume.
  • Reading; Sherwood, Chapters 10 &11, Chapter 15 pages 569-570 ; Robbins, pages 84-90
coagulation cascade
Coagulation Cascade
  • Very complex
    • >50 substances effect coagulation
    • procoagulants
    • anticoagulants
  • Key Steps
    • Formation and/or Activation of prothrombin activator/s (Factor X)
    • Conversion of prothrombin to _________________
    • Conversion of fibrinogen to ___________________.
coagulation cascade1
Coagulation Cascade

Activation of Prothrombin activator/s is the

rate limiting step.

Sherwood’s Human Physiology 11-12

intrinsic pathway
Intrinsic Pathway

Guyton’s Textbook of Medical Physiology 36-4

extrinsic pathway
Extrinsic Pathway

Guyton’s Textbook of Medical Physiology 36-3

summary
Summary

Sherwood’s Human Physiology 11-13

fibrinolytic system
Fibrinolytic System
  • Limits the size of the clot.
  • Plasminogen is a plasma protein trapped in the clot.
  • It is cleaved into plasmin by tPA.
  • Plasmin breaks down __________________ and interferes with its polymerization.

Robbins’ Basic Pathology 4-12

leukocytes
Leukocytes
  • White blood cells (WBC’s) that serve in the immune system.
  • Primary functions:
    • Defend against pathogens via phagocytosis.
    • Identify and destroy cancer cells.
    • Phagocytose debris resulting from dead or injured cells.
factors involved in blood pressure
Factors Involved in Blood Pressure
  • mean arterial pressure = cardiac output X total peripheral resistance

Sherwood’s Human Physiology 10-35 (10-34 6th Edition)

factors involved in blood pressure1
Factors Involved in Blood Pressure
  • There are both short term and long term adjustments made to normalize blood pressure.
  • Short Term (within seconds to minutes)
    • Alterations in cardiac output and total peripheral resistance (______________________________)
  • Long Term (minutes to days)
    • Adjusting total blood volume

Sherwood’s Human Physiology 10-35 (10-35 6th Edition)

arterial baroreceptors
Arterial Baroreceptors
  • Constantly monitor mean arterial pressure and pulse pressure.
  • Mechano-receptors in the walls of several large arteries.

Sherwood’s Human Physiology 10-36 (10-36 6th Edition)

arterial baroreceptors1
Arterial Baroreceptors
  • Cardiovascular Control Center
  • Located in the __________________
  • Autonomic nervous system “feedback”

Guyton’s Textbook of Medical Physiology 18-5

arterial baroreceptor
Arterial Baroreceptor
  • Increased arterial pressure => Increased CNS signal.
  • Decreased arterial pressure => decreased CNS signal.

Guyton’s Textbook of Medical Physiology 18-6

arterial baroreceptor1
Arterial Baroreceptor

Sherwood’s Human Physiology 10-37 (10-36 6th Edition)

baroreceptor reflex
Baroreceptor Reflex
  • Increased CNS signal (increased BP)
    • Inhibit vasoconstrictor center of medulla.
      • Vasodilation of veins and arteries => decreasing peripheral resistance.
    • Excite vagal parasympathetic center.

Sherwood’s Human Physiology 10-38 (10-37 6th Edition)

baroreceptor reflex1
Baroreceptor Reflex
  • Decreased CNS signal (decreased BP)
    • Excite vasoconstrictor center of medulla.
      • Vasoconstriction of veins and arteries => increasing peripheral resistance.
    • Excite vagal _____________________________________ center.

Sherwood’s Human Physiology 10-38 (10-37 6th Edition)

effects of changing body position on the arterial baroreceptor
Effects of changing body position on the arterial baroreceptor

Standing from a supine position (lying down)

-BP in upper body and head decreases and can cause a loss of consciousness.

-Decreased pressure elicits a an immediate reflex resulting in a strong sympathetic response.

arterial baroreceptor as a pressure buffer system
Arterial baroreceptor as a pressure buffer system
  • Important in maintaining pressure during changes in body position.
  • Functions as a “pressure buffer system” since without an arterial baroreceptor there is an increase in pressure variability.

Guyton’s Textbook of Medical Physiology 18-8

arterial baroreceptor is a short term regulator
Arterial baroreceptor is a short term regulator
  • Arterial baroreceptors are responsible for reducing the minute by minute variations in arterial pressure by 1/2-1/3.
  • ____________ Term Regulation

Guyton’s Textbook of Medical Physiology 18-9

summary of baroreceptor reflex
Summary of Baroreceptor Reflex

Increased BP

Sherwood’s Human Physiology 10-39 (10-38 6th Edition)

summary of baroreceptor reflex1
Summary of Baroreceptor Reflex

Decreased BP

Sherwood’s Human Physiology 10-39 (10-38 6th Edition)

chemoreceptor reflex
Chemoreceptor Reflex
  • Located in the ______________________ and adjacent to the aorta.
  • Sensitive to:
    • Decreased O2
    • Excess CO2
    • Excess H+ (low pH)

Guyton’s Textbook of Medical Physiology 18-5

chemoreceptor reflex1
Chemoreceptor Reflex
  • Excite nerve fibers in the vasomotor center of the brain stem.
  • Decreased pressure => decreased O2, increased CO2, increased H+ => stimulates chemoreceptors => maintain vasoconstrictor tone => increased pressure back to normal.
  • Not a powerful reflex
    • Because it is only activated at pressures below 80mm Hg.
blood pressure control mechanisms
Blood Pressure Control Mechanisms

Guyton’s Textbook of Medical Physiology 19-15

cns ischemic response last ditch stand
CNS Ischemic Response“Last ditch stand”
  • Control of arterial pressure in response to diminished brain blood flow.
  • Neurons in the vasomotor center respond directly and strongly.
  • Their stimulation results in systemic arterial pressure as high as the heart can pump.
    • Due to elevated level of CO2 stimulating sympathetic nervous system in medulla.
    • One of the most powerful activators of the sympathetic vasoconstrictor system.
blood pressure control mechanisms1
Blood Pressure Control Mechanisms

Guyton’s Textbook of Medical Physiology 19-15

cushing reaction
Cushing Reaction
  • In response to elevated cerebrospinal fluid pressure.
  • When cerebrospinal fluid pressure>arterial pressure, the brain’s vessels collapse and blood flow stops.
  • This initiates the CNS ischemic response and the elevation of arterial pressure > than the cerebrospinal fluid pressure.
volume reflex
Volume Reflex
  • Left atrial volume receptors and osmoreceptors are involved in H2O and NaCl balance.
  • They play a role in ___________________ Term regulation of BP by increasing blood volume & vasoconstriction.

Sherwood’s Human Physiology 15-4

renal body fluid system for arterial pressure control
Renal-Body Fluid System for Arterial Pressure Control
  • Primitive: dates back to the hag fish.
  • Long Termregulation of BP.
  • Pressure diuresis is the increase in output volume as arterial pressure rises.
renal body fluid system for arterial pressure control1
Renal-Body Fluid System for Arterial Pressure Control

Guyton’s Textbook of Medical Physiology 19-1

blood pressure control mechanisms2
Blood Pressure Control Mechanisms

Guyton’s Textbook of Medical Physiology 19-15

water and salt intake vs renal output

More output than input

More input than output

Water and Salt Intake vs. Renal Output

Renal output of water and salt

8

4

Intake or output (fold)

Equilibrium point

Water and salt intake

1

50

100

150

Arterial pressure

blood volume increases
Blood Volume Increases
  • If you increase the volume of blood there is an immediate response to increase CO, Urine out flow, and arterial pressure.

Guyton’s Textbook of Medical Physiology 19-2

renin angiotensin system
Renin-Angiotensin System
  • When the Kidneys experience ________________ arterial pressure their Juxtaglomerular cells release a small protein,Renin.
  • Renin is not a vasoactive substance it is an enzyme which cleaves a plasma protein angiotensinogen to angtensin I which is a mild vasoconstrictor.
  • Angiotensin I is cleaved in the lungs into Angiotensin II which is a strong vasoconstrictor and decreases renal excretion of both water and salt.
renin angiotensin system1
Renin-Angiotensin System

Decreased arterial pressure

Renin release from Kidneys

Angiotensinogen

Angiotensin I (mild vasoconstriction)

Converting enzyme (in lung)

Angotensinase

Angiotensin II

(inactive)

Renal retention of

salt and water

Strong vasoconstriction

next time
Next Time
  • Cardiovascular pathology
    • Hypertension
    • Atherosclerosis

Readings; Robbins, Atherosclerosis 328-338, Hypertension 338-341.

objectives
Objectives
  • Describe the coagulation cascade.
  • Describe how blood pressure is regulated (short term vs long term).
      • Baroreceptors and baroreceptor reflex
      • Chemoreceptors and chemoreceptor reflex
      • Ischemic response
      • Volume reflex and the role of the kidney (renin-angiotensin system)
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