ENDOCRINE SYSTEM

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ENDOCRINE SYSTEM
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Homeostasis Controls

• Successful compensation
• Homeostasis reestablished
• Failure to compensate
• Pathophysiology
• Illness
• Death

Figure 1-5 Homeostasis
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ENDOCRINE SYSTEM

• Uses chemical signals for cell to cell
  communication
• Coordinates the function of cells
• Response to an endocrine signal occurs within
  minutes to hours

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Chemical Regulating Systems Overview

• Pheromones organism to organism communication
• Hormones cell to cell communication molecules
• Made in gland(s) or cells
• Transported by blood
• Distant target tissue receptors
• Activates physiological response

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Paracrines and Autocrines

• Local communication
• Signal chemicals diffuse to target
• Example Cytokines
• Autocrinereceptor on same cell
• Paracrineneighboring cells

Figure 6-1c Direct and local cell-to-cell
communication
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Long Distance Communication Hormones

• Signal Chemicals
• Made in endocrine cells
• Transported via blood
• Receptors on target cells

Figure 6-2a Long distance cell-to-cell
communication
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Figure 6-2b, c Long distance cell-to-cell
communication
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Signal Pathways

• Signal molecule (ligand)
• Receptor
• Intracellular signal
• Target protein
• Response

Figure 6-3 Signal pathways
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• Membrane associated enzymes
• External reactions
• Internal reactions
• Receptors bind specific ligand
• Example Hormones
• Cell recognition molecules

Figure 5-6 Cell membrane receptor
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Receptor locations

• Cytosolic or Nuclear
• Lipophilic ligand enters cell
• Often activates gene
• Slower response
• Cell membrane
• Lipophobic ligand can't enter cell
• Outer surface receptor
• Fast response

Figure 6-4 Target cell receptors
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• HORMONE CLASSIFICATION
• Protein and polypeptide
• Amine
• Steroid

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PEPTIDE HORMONES

• Consist of specific amino acids
• Synthesized as large precursor proteins
• Stored in membrane-enclosed compartments
• Hydrophillic

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Protein and Polypeptide Hormone Receptors

• Surface receptor
• Hormone binds
• Transduction
• Enzyme activation
• Open channels
• Second messenger systems
• Synthesis

Figure 7-5 Membrane receptors for peptide
hormones
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AMINE HORMONES

• Derived from the amino acid tyrosine
• Includes thyroid hormones and catecholamines
• Stored until secreted

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STEROID HORMONES

• Precursor Cholesterol
• Lipophillic
• Immediately released from the cell following
  synthesis

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Steroid Hormones

• Cytoplasmic or nuclear receptors (mostly)
• Activate DNA for protein synthesis
• Slower acting, longer half-life
• Examples cortisol, estrogen testosterone

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Steroid Hormones Action
Figure 7-7 Steroid hormone action
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Summary of the Endocrine System
Figure 7-2-1 ANATOMY SUMMARY Hormones
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Feedback Loops
Figure 6-26 Negative and positive feedback
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HYPOTHALAMUS

• Integrates functions that maintain chemical and
  temperature homeostasis
• Functions with the limbic system
• Controls the release of hormones from the
  anterior and posterior pituitary

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HYPOTHALAMUS

• Synthesizes hormones in cell bodies of neurons
  located in the hypothalamus
• Transports hormones down the axon and stored in
  the nerve endings
• Secretion of hormones is in pulses

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Negative Feedback Controls Long Short Loop
Reflexes
Figure 7-14 Negative feedback loops in the
hypothalamicanterior pituitary pathway
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Negative Feedback Controls Long Short Loop
Reflexes
Figure 7-15 Control pathway for cortisol
secretion
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ANTERIOR PITUITARY
MOSTLY EPITHELIAL TISSUE ORGANIZED IN BLOCKS
AROUND MANY BLOOD VESSELS SECRETES HORMONES IN
RESPONSE TO RELEASING HORMONES FROM THE
HYPOTHALAMUS CONTAINS 5 TYPES OF SECRETORY CELLS
WHICH PRODUCE, COLLECTIVELY 6 DIFFERENT HORMONES
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ANTERIOR PITUITARY
ANTERIOR PITUITARY
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ANTERIOR PITUITARY HORMONES
Growth Hormone (GH, Somatotropin) primary
hormone responsible for regulating body growth,
and is important in metabolism Thyroid-stimulatin
g Hormone (TSH) stimulates secretion of thyroid
hormone growth of thyroid gland Adrenocorticotr
opic Hormone (ACTH) stimulates cortisol
secretion by the adrenal cortex promotes growth
of adrenal cortex
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ANTERIOR PITUITARY
Follicle-stimulating Hormone (FSH) Females
stimulates growth development of ovarian
follicles, promotes secretion of estrogen by
ovaries. Males required for sperm
production Luteinizing Hormone (LH) Females
responsible for ovulation, formation of corpus
luteum in the ovary, and regulation of ovarian
secretion of female sex hormones. Males
stimulates cell in the testes to secrete
testosterone Prolactin Females stimulates
breast development and milk production. Males
involved in testicular function
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POSTERIOR PITUITARY
Hormones synthesized in the hypothalamus are
transported down the axons to the endings in the
posterior pituitary Hormones are stored in
vesicles in the posterior pituitary until release
into the circulation Principal Hormones
Antidiuritic hormone (ADH) Oxytocin (OT)
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Figure 7-12 Synthesis, storage, and release of
posterior pituitary hormones
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POSTERIOR PITUITARY
Oxytocin Action primarily on the breasts and
uterus where it stimulates contractions to aid in
childbirth and breast-feeding in women Increases
contraction of smooth muscle of Vas Deferens
in men
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POSTERIOR PITUITARY
Antidiuretic hormone (ADH) Reduces the volume of
water excreted by the kidneys Regulates water
concentration of body fluids Responds to
dehydration and causes kidneys to produce less
urine, conserving water Suppressed by alcohol
which leads to frequent urination and clear
colored urinedehydration and hangover.
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Summary of the Endocrine System
Figure 7-2-3 ANATOMY SUMMARY Hormones
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Summary of the Endocrine System
Figure 7-2-2 ANATOMY SUMMARY Hormones