1. Blood Pressure Control Simplified Version

2. Blood Pressure Control
Widespread Control – Control all over the body A. Nervous System B. Hormones Local Control – Control of certain organs

3. MAP = CO x SVR CO = HR x SV SV = EDV – ESV
(EDV concerned with blood volume and ESV concerned more with inotropic effect)
SVR = ∑R₁ + R₂ + 1/R₃ + 1/R₄ …..
R = 8ŋL/∏r⁴
In order to live – the body compensates by increasing the actions of the organs not affected (homeostasis – negative feedback)

4. Nervous System Blood Pressure Control
Cardiovascular Center
Cardiac Center – Cardiac Acceleratory Center and Cardiac Inhibitory Center
Vasomotor Center – Vasoconstrictor Center and Vasodilator Center

5. Cardiovascular center

7. Vasoconstrictor
Vasodilator Center

8. Baroreceptors

9. Alpha receptors on Blood Vessels

10. Hormonal Control of Blood Pressure
Renin – Angiotensin System
Aldosterone
ADH – Antidiuretic Hormone (Vasopressin)
Epinephrine
Atrial Natriurectic Polypeptide

11. Renin Angiotensin
Angiotensinogen – is produced by the liver. We have a circulating concentration in the blood.
A hormone type enzyme produced and secreted by the kidney (Renin) converts Angiotensinogen to Angiotensin I (one). This substance does nothing.
Endothelial cells in several locations, particularly the lungs produce and secrete Angiotensin Converting Enzyme. This enzyme converts Angiotensin I to Angiotensin II.

12. Angiotensin II has several functions, some are:
Act as a powerful vasoconstrictor
Stimulate production of Aldosterone from the adrenal cortex
Stimulate production of ADH from the posterior pituitary.

15. Zona glomerulosa Zona fasciculata Zona reticularis Adrenal medulla
Capsule
Zona
glomerulosa
Zona
fasciculata
Adrenal gland
Cortex
• Medulla
• Cortex
Zona
reticularis
Kidney
Medulla
Adrenal
medulla
(a) Drawing of the histology of the
adrenal cortex and a portion of
the adrenal medulla
Figure 16.13a

16. Aldosterone Regulate electrolytes (primarily Na+ and K+) in ECF
Importance of Na+: affects ECF volume, blood volume, blood pressure, levels of other ions
Importance of K+: sets RMP of cells
Aldosterone is the most potent mineralocorticoid
Stimulates Na+ reabsorption and water retention by the kidneys

17. Hypothalamic hormones travel through the portal
Hypothalamus
When appropriately
stimulated,
hypothalamic neurons
secrete releasing and
inhibiting hormones
into the primary
capillary plexus. 1
Hypothalamic neuron
cell bodies
Superior
hypophyseal artery
Hypophyseal
portal system
Hypothalamic hormones
travel through the portal
veins to the anterior pituitary
where they stimulate or
inhibit release of hormones
from the anterior pituitary. 2
• Primary capillary
plexus
• Hypophyseal
portal veins
• Secondary
capillary
plexus
Anterior lobe
of pituitary
Anterior pituitary
hormones are secreted
into the secondary
capillary plexus. 3
TSH, FSH,
LH, ACTH,
GH, PRL
(b) Relationship between the anterior pituitary and the hypothalamus
Figure 16.5b

18. Antidiuretic Hormone (ADH)
Hypothalamic osmoreceptors respond to changes in the solute concentration of the blood
Can be stimulated to be secreted due to Angiotensin II
If solute concentration is high
Osmoreceptors depolarize and transmit impulses to hypothalamic neurons
ADH is synthesized and released, inhibiting urine formation

19. Antidiuretic Hormone (ADH)
Hypothalamic osmoreceptors respond to changes in the solute concentration of the blood
If solute concentration is high
Osmoreceptors depolarize and transmit impulses to hypothalamic neurons
ADH is synthesized and released, inhibiting urine formation

20. Epinephrine
Chromaffin cells in the adrenal medulla secrete epinephrine (80%) and norepinephrine (20%)
These hormones cause
Blood glucose levels to rise
Blood vessels to constrict
The heart to beat faster
Blood to be diverted to the brain, heart, and skeletal muscle

21. Adrenal Medulla
Epinephrine stimulates metabolic activities, bronchial dilation, and blood flow to skeletal muscles and the heart
Norepinephrine influences peripheral vasoconstriction and blood pressure

23. FFF RR
FFF – Fear, Fight & Flight RR – Rest and Recluse
Receptors for NE are alpha and beta with subtypes. The receptors for
Acetylcholine are nicotinic and muscarinic. On the heart there are
Beta 1 receptors for NE and muscarinic for acetylcholine.

24. Atrial Natriurectic Polypeptide (ANP)
Atrial natriuretic peptide (ANP) is a polypeptide hormone which reduces an expanded extracellular fluid (ECF) volume by increasing renal sodium excretion. ANP is synthesized, secreted, and released by heart muscle cells (myocytes) in the atrial wall. These cells contain volume receptors which respond to increased stretching of the atrial wall due to increased atrial blood volume. ANP is one of a family of nine natriuretic hormones: seven are atrial in origin.

25. Intrinsic mechanisms Extrinsic mechanisms (autoregulation) controls
• Maintain mean arterial pressure (MAP)
• Redistribute blood during exercise and
thermoregulation
• Distribute blood flow to individual
organs and tissues as needed
Amounts of: pH
Sympathetic
Nerves O2
a Receptors
Metabolic
controls
Epinephrine,
norepinephrine
b Receptors
Amounts of:
CO2 K+
Angiotensin II
Hormones
Prostaglandins
Adenosine
Antidiuretic
hormone (ADH)
Nitric oxide
Endothelins
Atrial
natriuretic
peptide (ANP)
Myogenic
controls
Stretch
Dilates
Constricts
Figure 19.15

26. Local Control (Autoregulation)
Paracrine/Autocrine
Myogenic Tone
Metabolites
Major organs discussed using local control are: Brain, Heart, skin, lungs

27. Paracrine/Autocrine
Paracrine and autocrine secretions are local secretions.
Vasodilation – Endothelial Derived Relaxing Factor (Nitric Oxide), Prostaglandins, Kinins Histamine
Vasoconstriction - Endothelin

28. Myogenic Controls
Myogenic responses of vascular smooth muscle keep tissue perfusion constant despite most fluctuations in systemic pressure
Passive stretch (increased intravascular pressure) promotes increased tone and vasoconstriction
Reduced stretch promotes vasodilation and increases blood flow to the tissue

29. Metabolites
H+, CO2, Adenosine, K+, O2