Endocrine System

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Endocrine System
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I. Endocrine system

• A. Endocrine tissues organs are found
  throughout the body some along organs part of
  other systems others found along glands
• B. Hormones are the molecules that are secreted
  by this system into extracellular fluid,
  circulate in the blood and communicate regulatory
  messages throughout the body.
• 1. Each hormone has specific receptors in the
  body that can regulate reproduction, development,
  metabolism, growth behavior

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II. Intercellular Communication

• A. There are 2 main criteria that classify how
  signals are transmitted between cells the type
  of secreting cell the route taken by the signal
  in reaching its target.

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• 1. Endocrine Signaling hormones secreted into
  extracellular fluid by endocrine cells reach
  target by flowing through blood stream

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• 2. Local regulators secrete molecules that act
  over short distances reach target cells solely
  by diffusion.
• Ex. Paracrine signaling target cells that lie
  near secreting cell
• Autocrine signaling cells are the secreted
  cell itself

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• 3. Synaptic Neuroendocrine Signaling allow
  for signaling through nervous system by neurons
• a. Neurotransmitters signaling at synapses
• b. Neurohormones molecules that are secreted by
  special neurons into the bloodstream (Ex. ADH)

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• 4. Pheromones chemicals released into the
  external environment
• a. commination within own species

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III. Classes of Hormones

• A. Hormones vary by size chemical properties
  since there are 3 chemical classes of hormones
  including
• 1. Polypeptides 2 polypeptides chains (insulin)
• 2. Steroids composed of lipids, 4 fused carbon
  rings (cortisol)
• 3. Amines one single amino acid
  (tyrosine/trptophan)
• B. The chemical make-up of the hormone explains
  how the hormone targets the cell polypeptides
  amines are water soluble so they can not pass
  through the cell membrane unlike steroids that
  are lipid soluble

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IV. Cellular Response Pathways

• A. How a hormone causes a response are different
  between water-soluble lipid-soluble hormones.
• 1. Water-soluble hormones are secreted by
  exocytosis travel through the blood stream
  bind to cell-surface protein receptors.
• a. can cause changes in transcription by signal
  transduction (extracellular chemical causing
  intercellular response) Ex. epinephrine

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• 2. Lipid-soluble hormones diffuse out across a
  membrane of endocrine cells, they bind to
  transport proteins that keep them soluble in the
  blood stream and then diffuse into target cells
• a. change in gene expression

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V. Effects of Hormones

• A. Hormones can cause more than one type of
  response in your body since target cells can vary
  in their response to a particular molecule with
  different receptors.
• 1. Epinepherine mediating bodys response to
  stress
• Triggers glycogen breakdown in liver
• Increased blood flow to major skeletal muscles
• Decreased blood flow to digestive tract

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VI. Signaling by Local Regulators

• A. There are several chemical compounds function
  as local regulators (Paracrine Autocrine)
• 1. Growth factor stimulate cell proliferation
• 2. Nitric oxide helps regulate the oxygen
  levels by activating enzymes that relax muscles
• 3. Prostaglandins stimulate muscle contraction
  in the uterus, promote fever inflammation,
  blood clotting

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VII. Regulatory Pathways

• A. Two basic types of organization
• 1. Simple endocrine pathway endocrine cells
  respond directly to internal or environment
  stimulus by secreting a hormone into blood stream
• Ex. Stomach contents enter duodenum - pancrease
• 2. Simple neuroendocrine pathway stimulates is
  received by sensory neuron, stimulates
  neurosecretory cell then secretes a neurohormone
  which diffuses into the bloodstreamand travels to
  target cells
• Ex. Suckling stimulates hypothalamus then trigger
  oxytocin from pituitary gland

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Negative vs. Positive
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IIX. Control of Blood Glucose

• A. Controlled by 2 antagonistic hormones that
  operate in a simple endocrine pathway regulated
  by negative feedback
• 1. Insulin triggers uptake of glucose from the
  blood, slows down glycogen breakdown
• 2. Glucagon promotes the release of glucose
  into the blood from energy stores, such as liver
  glycogen,
• B. Both are released by the pancreas into the
  circulatory system
• Alpha cells make glucagon
• Beta cells make insulin
• Diabetes mellitus deficiency of insulin or a
  decreased response to insulin in target cells.
  Fat becomes main energy source acidic
  metabolites form lowering blood pH