Distribution of blood in the body 211

1
Distribution of blood in the body 2/11

• How does gravity affect blood pressure and
  delivery in the body?
• What are three ways to regulate cardiac output?
• How do inotropic and chronotropic agents modify
  cardiac function?
• What is the clinical significance of venous
  return?
• What are the structural features of arteries and
  veins?
• How do precapillary sphincters control the entry
  of blood into a capillary bed?
• If blood does not enter a capilllary bed can
  oxygen delivery to tissue occur?

2
This or something like it will be on the next
lecture exam and quizWhat letter would represent
AV valve closure? A, B, C, D, E, F or GWhat
letter would represent the start of the atrial
kick into the ventricles? A, B, C, D, E, F or
GWhat is the cardiac output of this ventricle?
Show Math.
3
Three ways to regulate cardiac output Intrinsic,
Local and Neural. They work to maintain O2
delivery to heart/brain/body!

• 1) Intrinsic Regulation Frank-Starling Law of
  the heart where EDV (preload) determines SV and
  cardiac output.
• 2) Local conditions in tissues (including heart)
  determine blood/oxygen supply and available
  workload.
• Hyperemia (warmth/CO2)?Vasodilation/Increased O2
  delivery
• Cold reflexes?Vasoconstriction less O2 delivery
• Angiogenesis? More blood vessels created when
  heart exercised
• Bohr Effect on Hb-oxygen saturation based on
  local conditions in tissues pH, CO2, and heat
  all increase/decrease O2 dumping
• 3) Neural (non-local) Regulation Info comes to
  cardiac center in medulla which regulates
  circulation
• Regulation of conditions at scale of body!
• A) Proprioceptors-
• B) Chemoreceptors-
• C) Baroreceptors-
• Cardiac Center of Medulla increases/decreases
  output of sympathetic/parasympathetic nervous
  systems to modify C.O.

4
WHAT ARE THREE WAYS THE BRAIN CAN REGULATE BLOOD
PRESSURE AND FLOW?

• 1)Proprioceptive Reflexes exercise stimulates
  SNS activity and increases contractility and rate
  ? ??CO
• 2) Baroreceptor Reflexes Stretch receptors in
  aorta and carotid sinuses detect low blood
  pressure and stimulate SNS/heart ? ??CO
• Golden Rule of Body When in doubtRaise the
  blood pressure.
• 3) Chemoreceptor Reflexes Chemoreceptors in
  Aortic Bodies, Carotid Bodies, Medulla Oblongata
  detect changes in blood pCO2/pH and pO2
• -They increase heart rate to drive more blood
  through lung (pick up oxygen on Hb) and deliver
  oxygen to the brain.
• -High pCO2 or low pH (slightly acidic pH)? ?? CO
  (very sensitive)
• -Low Blood pO2 causes increased ??CO (very
  strong stimulus)
• Hormonal Control of BP by the heart (ANF)
  also exists and will be discussed more in the
  Renal Unit.

5
Review of baroreceptors and chemoreceptors their
location and importance.
6
MATCHING BLOOD FLOW/SUPPLY (CARDIAC OUTPUT) TO
METABOLIC NEEDS IS DIFFICULT, BUT HOMEOSTASIS IS
MAINTAINED BY LOCAL AND (if needed) NEURAL
METHODS.

• Sympathetic NS increases heart rate and
  contractility (?CO)
• Parasympathetic NS decreases the heart rate (?CO)
• How do agents in body modify heart rate and
  contractility? Chronotropic vs.
  Inotropic Agents
• SA Node (rate) vs. Force of Vent.
  Contraction (SV)
• Positive CSNS vs. Positive I Digitalis to
  ?cellular Ca
• Negative CPNS vs. Negative I Myocardial
  Hypoxia
• Cardiac Reserve represents extra work your heart
  could do if you needed to do more (i.e. increase
  CO during exercise)
• On the Frank Starling Curve, a failing heart is
  past its reserve

7
Frank Starling Curve Shifts Up when the heart
needs to work harder ( Add Epinephrine) and
Shifts Down when the heart starts to fail (add
Hypoxia or have an Infarct). If Preload Changes
on a Single Curve? Stroke volume changes.
8
When your body is resting increased
parasympathetic nervous system activity
distributes blood to areas needed for growth and
maintenance.
9
Preparation for Fight or Flight is associated wit
ha change in blood flow due to the sympathetic
nervous system and local autoregulation! Tissues
that are heavily used generate heat and CO2 which
cause local dilation and greater blood flow TO
these tissues. NOTE Cardiac Output has changed
from 5L/min?15 L/min
10
Review of Systemic and Pulmonary Circuits in
addition to portal systems (hepatic) and
anastomoses (V.I.P. cardiac collateral flow)
11
BASIC VESSEL CROSS-SECTION The Three Layers of a
Blood Vessel larger than a capillary.

• 1) Tunica Externa (adventitia)-outer layer
  Protection
• Composed of tough collagen, elastic elastin and
  nerves
• 2) Tunica Media-middle layer Vasoactivity/Changin
  g blood flow
• 2 smooth muscle cell layers inner-circular
  outer-longitudinal
• SMC contractions narrow vessel and increase
  resistance
• SMC contractions squeeze blood towards heart
• SMC Dilation (relaxation) decreases
  resistance/pressure
• 3)Tunica Intima-inner layer Communication
• Composed of a thin elastic later
• Single layer of endothelial cells (SSEC) that is
  very fragile
• Cells signal health Nitric oxide and
  prostacyclin
• Cells signal injury Prostaglandins and
  serotonin
• SYSTEMIC FLOWAorta?Artery?Arteriole?Capillary?Ven
  ule?
• Vein?VenaCava?Rt Atrium?Rt.Vent?Lung?Lt
  Vent.?Aorta
• Arteries Resistance/High Pressure Veins
  Capacitance/Low Pressure

12
Arteries thick tunica media Veins thin
tunica media.
13
There are Three Types of Blood Vessel Artery,
Capillary and Vein

• Arteries high pressure/thick wall to maintain
  pressure
• Resistance Vessels of Body Blood pressure
  conserved!
• Smooth muscle can help maintain pressure and
  determines
• resistance/blood flow in/out! Arteriole and
  metarteriole smallest
• Conducting(high elastin)?Distributing?Resistance(h
  igh SCM)
• Capillary has a thin wall consisting of only one
  endothelial cell for quick diffusion of
  materials. Plural Capillary Bed
• Exchange Vessels of Body things exchanged
  here! Oxygen Delivery!
• If you have two capillary beds in a row its a
  portal
• Gut/Liver Hypothalmus/Pituitary
  (also in kidney)
• Capilaries have a high surface area and
  Surprisingly tiny total volume!
• Veins low pressure/thin wall to store blood
• Capacitance Vessels of Body Blood reserve!
• Venule smallest?Vein?VenaCava
• Smooth muscle contraction to help speed venous
  return!
• Valves help prevent blood from moving backwards!
  
• Faulty valves result in VARICOSE VEINS!
• Muscular contraction help pump blood towards the
  heart!

14
Blood cant enter capillaries and deliver its
oxygen if the smooth muscle cell at the
pre-capillary sphincter is contracted. In this
case it bypasses capillaries and returns to heart
(this can cause angina). Alternately, collateral
flow can permit small blood vessels to deliver
blood and oxygen to other regions of the heart
not normally supplied.
Gas Exchange Occurs Only In Capillaries With
Blood Flow