Endocrine Function

1
Endocrine Function
2
Overall functions of the Endocrine System

• Regulation of energy metabolism
• Water and electrolyte balance
• Adaptation to various types of stress
• Control of growth and development
• Control of reproduction
• Regulation of RBC production
• Integrating Digestive System functions (with ANS)

3
Control of Hormone Secretion

• Direct Nervous System Stimulation
• Negative Feedback
• Hypothalamic Control
• Three levels of integration
• Hypothalamus --gt Pituitary
  --gt endocrine gland
• (releasing inhibiting factors) (tropic
  hormones) (response in target cells)

4
Hypothalamic Regulation of Endocrine Glands
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This figure is found on page 109 of your course
packet.
5
Review Chemical Classification of Cellular
Messages

• Lipid Soluble (Hydrophobic)
• Steroids derived from cholesterol and
  synthesized in smooth ER
• Thyroid hormones T3 and T4
• Nitric oxide (NO) acts both as a paracrine and
  hormone
• Water Soluble (Hydrophilic)
• Modified amines catecholamines (e.g.
  nor-epinephrine), histamine, serotonin, and
  melatonin
• Peptides/Proteins ADH, insulin
• Eicosanoids prostaglandins, leukotrienes

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Protein and Polypeptide Hormones Synthesis and
Release
Figure 7-3 Peptide hormone synthesis, packaging,
and release
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Protein and Polypeptide Hormone Receptors

• change membrane permeability
• alter the function of intracellular proteins

Figure 7-5 Membrane receptors for peptide
hormones
8
Amine Hormone Structures and Functions
Figure 7-8 Tyrosine-derived amine hormones
9
Steroid Hormone Synthesis and Release

• Synthesized from cholesterol by specific enzymes
  in smooth ER
• Produced as needed
• (i.e. not stored, although cholesterol may be
  stored)
• Diffuse out of cell passively
• (most attached to transport proteins while in the
  plasma)

10
Steroid Hormones Structure and Action
Figure 7-7 Steroid hormone action
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Steroid Hormones Structure and Action
Figure 7-6 Steroid hormones are derived from
cholesterol
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Hormone Interactions

• Synergism and Antagonism
• multiple synergistic stimuli are more than
  additive
• insulin opposes glucagon
• Is insulin a competitive inhibitor of glucagon?

• Permissiveness
• need 2nd hormone to get full expression
• e.g. reproductive development

13
Pathologies of Endocrine Function

• Too Little Hormone Activity
• Hyposecretion
• Goiter Diabetes
• Exogenous replacement
• (e.g. Cortisol)
• Secondary hyposecretion
• Increased removal from blood
• Lack of target cell receptors
• Congenital Down-regulation
• Lack of protein (enzyme) essential to target cell
  response

• Too Much Hormone Activity
• Hypersecretion
• Graves disease
• Pheochromocytoma
• Reduced binding or removal from blood plasma
• Decreased metabolic inactivation
• Liver disease
• Decreased excretion
• Kidney disease