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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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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 baroreceptor

  • 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 baroreceptor

  • 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 baroreceptor

Increased BP

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


Summary of baroreceptor reflex1
Summary of Baroreceptor Reflex baroreceptor

Decreased BP

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


Chemoreceptor reflex
Chemoreceptor Reflex baroreceptor

  • 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 baroreceptor

  • 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 baroreceptor

Guyton’s Textbook of Medical Physiology 19-15


Cns ischemic response last ditch stand
CNS Ischemic Response baroreceptor“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 baroreceptor

Guyton’s Textbook of Medical Physiology 19-15


Cushing reaction
Cushing Reaction baroreceptor

  • 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 baroreceptor

  • 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 baroreceptor

  • 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 baroreceptor

Guyton’s Textbook of Medical Physiology 19-1


Blood pressure control mechanisms2
Blood Pressure Control Mechanisms baroreceptor

Guyton’s Textbook of Medical Physiology 19-15


Water and salt intake vs renal output

More output than input baroreceptor

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 baroreceptor

  • 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 baroreceptor

  • 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 baroreceptor

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 baroreceptor

  • Cardiovascular pathology

    • Hypertension

    • Atherosclerosis

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


Objectives
Objectives baroreceptor

  • 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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