Chapter%209:%20Endocrine%20System%20and%20Hormone%20Activity

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Chapter 9 Endocrine System and Hormone Activity

• Homeostatic Control through Hormone Release

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Overview

• Coordinates and directs the activity of cells.
• Interacts with the nervous system.
• Uses chemical messengers called hormones.
• Controls a variety of necessary biological
  functions such as
• Reproduction
• Growth and Development
• Defense
• Balance of fluids and
  electrolytes

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Mechanism of Action

• Hormones only affect certain tissues or organs
• Hormones bind only to specific sites on the
  plasma membrane of those Target cells
• The Target cell becomes active once the hormone
  is bound to its specific receptor.

Targets
Receptors
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Classifications

• Amine/Peptide
• Chemical base is a SINGLE Amino Acid.
• Acts by activating an enzyme through
  receptor-binding on the cell membrane.
• Does NOT enter the cell remains on the outside
  of the cell membrane.

• Lipid/Steroid
• Chemical base is cholesterol.
• Acts by directing gene activation in the nucleus.
• Enters the cell membrane and nucleus of the
  Target cell because it is lipid-soluble.

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Hormone Action What can hormones do?

• Change the permeability or electrical state of
  the cell membrane.
• Synthesize molecules in the cell.
• Activate/Inactive enzymes.
• Stimulating, slowing or stopping mitosis

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Control of Hormone Release

• Negative Feedback Mechanisms regulate the blood
  levels of most hormones in 3 ways
• Hormonal stimuli
• Humoral stimuli
• Neural stimuli

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Hormonal Stimulation

• One hormone triggers the release of another
  hormone.
• These trigger hormones are TROPHIC HORMONES.
• Released by the Pituitary Gland in the brain.

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Humoral Stimulation

• Blood levels of chemicals triggers the release of
  specific hormones.

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Neural Stimulation

• Nerve fibers (Autonomic Sensory Receptors)
  trigger the release of specific hormones.

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Major Endocrine Organs
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Pituitary GlandThe Master Gland

• 2 Functional Lobes
• Anterior Lobe
• Posterior Lobe
• Interacts closely with the Nervous System through
  the hypothalamus.
• Protected by what structure?

Sphenoid Bone
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Anterior Pituitary

• Regulated through humoral stimulation from the
  hypothalamus.
• Many of the hormones released are Trophic
  Hormones.

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Anterior Pituitary Hormones

• Growth Hormone (GH)
• Thyroid Stimulating Hormone (TSH)
• Adrenocorticotropin Hormone (ACTH)
• Follicle Stimulating Hormone (FSH)
• Luteinizing Hormone (LH)
• Melanocyte Stimulating Hormone (MSH)
• Endorphins

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Too Much Growth Hormone

• Acromegaly is caused by too much growth hormone
  AFTER puberty has completed.

• Gigantism is caused by too much growth hormone
  during adolescence and puberty.

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Too Little Growth Hormone

• The girl below is pictured with her father at the
  age of 5 years.

• The man on the left is 25 years old. The man on
  the right is 22 years old.

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Abnormal TSH secretion

• Exopthalmosis (bulging eyes) due to Graves
  Disease.

• Goiter formation due to inadequate iodine
  consumption.

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Posterior Pituitary

• Regulated through neural stimulation from the
  hypothalamus.
• Produces 2 hormones in response to nervous system
  stimulation.
• Antidiuretic hormone (ADH)
• Oxytocin

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Thyroid Gland

• Located in the anterior portion of the neck, just
  below the throat.
• Releases hormones that act on the metabolic rate.
• T4 thyroxine
• T3 triiodothyronine
• Also produces the calcitonin.

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Parathyroid Gland

• Located on the posterior surface of the Thyroid
  gland.
• Secretes Parathyroid Hormone (PTH)
• The MOST important regulator of blood calcium
  levels.

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Adrenal Glands

• Located on the superior aspect of each kidney.
• 2 functional parts
• Cortex
• Medulla
• Each part secretes a specific type of hormone.

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Adrenal Gland Divisions

• CORTEX
• Produces hormones that control fluid and
  electrolyte balance.
• Produces sex hormones.

• MEDULLA
• Produces hormones for sympathetic/
• parasympathetic nervous system.

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Pancreas

• Located in
• abdominal cavity
• close to stomach.
• Produces hormones for the use and storage of
  glucose
• Insulin
• Glucagon

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Pineal Gland

• Pineal gland is very close to the optic nerve in
  the brain.
• Produces Melatonin that activates sleep-wake
  cycles.

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Thymus Gland

• Located behind the sternum.
• Decrease in size as you age.
• Produces Thymosin needed for the production of
  T-lymphocytes.
• T-cells are needed for protection against viral
  infections.

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Ovaries and Testes

• Hormone producing glands (Gonads) of the female
  and male reproductive systems.
• Controls fertility, reproduction, and gestation.

• Testes produce testosterone and androgens

• Ovaries produce and release estrogen and
  progesterone

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Other Hormone-Producing Organs

• Placenta
• Stomach
• Intestines
• Heart
• Striated muscles

• Skin
• Adipose/Fat
• Liver
• Kidneys
• Uterus