Chemical Signals in Animals

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Chemical Signals in Animals

• Chapter 41

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Chemical Signals An Intro

• All animals exhibit coordination by chemical
  signals
• Hormones convey info between organs within the
  body
• Neurotransmitters carry info between cells of the
  nervous system

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Hormones

• Hormones are chemical signals secreted into body
  fluids (usually blood)
• Hormones cause specific responses from selected
  cells ? target cells
• There are more 50 different hormones in the body!

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Endocrine vs. Exocrine Glands

• Endocrine glands are ductless glands
• They secrete hormones into body fluids
• Exocrine glands secrete their products into ducts
  (kind of like pipes)
• These products go only to certain locations
  within the body

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Pheromones

• Pheromones are similar to hormones, with one
  important difference
• Pheromones are communication signals between
  animals of the same species
• Function as mate attractants, territorial
  markers, alarm substances

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Signal-Transduction Pathways

• A signal transduction pathway links a (mechanical
  or) chemical stimulus to a cellular response
• A hormone binds with a receptor protein in the
  target cell membrane, which then binds with a G
  protein, which binds with GTP, which binds with
• Broken telephone but not broken!! ?
• The end result the desired cellular response

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Signal-Transduction Pathway
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Major Endocrine Glands

• Hypothalamus
• Integrates the nervous and endocrine systems
• The master chief gland
• Pituitary Gland
• Obeys the hypothalamus
• Posterior and anterior pituitary glands
• ADH, GH, PRL, FSH, LH, TSH, ACTH

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Human Endocrine Glands
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Major Endocrine Glands

• Thyroid Gland
• Growth and development
• Maintenance of homeostasis
• Lowers blood calcium level
• Parathyroid Glands
• Raises blood calcium level

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Human Endocrine Glands
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Major Endocrine Glands

• Pancreas
• Produces insulin and glucagon
• Insulin lowers blood glucose level
• Glucagon raises blood glucose level
• Hmm why???

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Human Endocrine Glands
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Major Endocrine Glands

• Adrenal Glands
• Epinephrine and norepinephrine
• Constrict certain blood vessels
• Increase metabolic activities
• Gonads
• Testes ? androgens
• Ovaries ? estrogens, progesterone

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Human Endocrine Glands
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Major Endocrine Glands

• Pineal Gland
• Produces melatonin, which is involved in
  biological rhythms
• Thymus
• Stimulates T lymphocytes

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Human Endocrine Glands
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Relationship Between Endocrine and Nervous
Systems

• Structural Relationships
• Many endocrine glands are made of nervous tissue
• Chemical Relationships
• Some hormones are also used as signals by the
  nervous system
• Functional Relationships
• Nervous and hormonal components are arranged in
  series
• Each system affects the other one