The Endocrine System (Chap 39, Sections 1

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The Endocrine System (Chap 39, Sections 1 2)

• Maintaining Homeostasis

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Introduction What happens at puberty?

• The hypothalamus releases a chemical called GnRH.
• GnRH stimulates the pituitary gland to release
  two more hormones
• luteinizing hormone (LH for short)
• follicle-stimulating hormone (FSH for short)
• Girls and boys have both of these hormones. The
  hormones act in different ways depending on what
  sex you are.
• Girls usually start puberty 8 13.
• Boys usually start puberty 10 15.

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Boys

• These hormones travel through the blood give
  the testes the signal to begin production of
  sperm testosterone. (need sperm to reproduce)
• Get taller last 2 -3 years, can grow up to
  4inches in a year.
• Gain weight
• Shoulders get wider, body become more muscular.
• Voices get deeper.
• Grow hair under arms, pubic areas, face.

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Girls

• Gain weight this is NORMAL!
• Girls' bodies usually become curvier
• They gain weight on their hips
• Breasts develop
• Menstrual cycle begins
• Grow hair under arms in pubic areas

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The Endocrine System

• Function Maintains homeostasis using hormones.
• An endocrine (ductless) gland secretes its
  products (hormones) directly into the blood
  stream.
• Hormones are slow working but long lasting.
• Hormones can only effect specific target cells.
• What do we call glands that release their
  products through ducts to the outside of the body
  or into body cavities?
• Exocrine glands Examples Sweat, tears,
  digestive juices

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Endocrine Gland Locations (Fig. 39-2)
Hypothalamus
Thyroid
Pituitary gland
Pancreas
Parathyroid glands
Ovary
Thymus
Testis
Adrenal glands
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II. Endocrine Gland Types Functions

• A. Pituitary Secretes 9 hormones that directly
  regulate many body functions, controls the
  actions of several other endocrine glands.
• The pituitary gland is controlled by the
  hypothalamus

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Gigantism an excess of growth hormone
Too much GH During childhood Development.
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Pituitary Dwarfism Too little growth hormone
Too little GH During childhood Development.
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1. Hypothalamus Produces hormones that control the
   pituitary gland, makes hormones stored in the
   pituitary gland.
2. Parathyroid Releases parathyroid hormone which
   acts to maintain homeostasis of the calcium
   levels in the blood and bones.
3. Thymus During childhood stimulates T cell
   development proper immune response.
4. Adrenal Release epinephrine norepinephrine
   which help the body respond to stress (flight or
   fight response).

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1. Thyroid Regulates the bodies metabolism by
   producing thyroxine (increases the rate of
   protein, carbohydrate fat metabolism also
   cellular respiration).
2. Pancreas produces insulin glucagon which
   regulate the level of glucose in the blood.
   Signals liver to store or release glucose.
3. Ovary produces estrogen and progesterone. These
   produce primary and secondary sex characteristics
   and regulate the menstrual cycle and pregnancy.
4. Testis produces testosterone for sperm
   production and primary and secondary sex
   characteristics.

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III. How do hormones work?

• Hormones belong to two groups steroid hormones
  non-steroid hormones.
• B. Steroid hormones
• 1. Made of lipids (fats) can cross cell
  membranes directly into the cytoplasm and
  nucleus.
• 2. Binds to a receptor protein inside the cell.
• 3. This receptor activates genes that carry out
  the actions associated with the hormone.

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C. Nonsteroid hormones Cannot pass through the
cell membrane.

• Made of proteins bind to receptors on the cell
  membrane surface.
• 2. This activates an enzyme on the inner surface
  of the cell membrane.
• 3. The enzyme activates secondary messengers to
  carry the signal
• 4. The second messenger activates or inhibits
  cell activities.

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Steroid Nonsteroid Hormones (fig. 39-3)
Nonsteroid hormone (first messenger)
Steroid Hormone
Target cell membrane
Target cell membrane
Receptor
Receptor
cAMP (second messenger)
Hormone-receptor complex
Altered cellular function
Enzyme activities
Nucleus
DNA
Altered cellular function
Protein synthesis
Nucleus
Cytoplasm
mRNA
Cytoplasm
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An Example of Endocrine Controlled Homeostasis
Regulation of blood sugar levels
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• Negative feedback your bodys response results
  in decreasing the effect of the stimulus, (e.g.
  body temperature). The effect is a relatively
  steady state is maintained.

Negative Feedback Example of Homeostasis (Fig.
35-4, p.895)
Thermostat senses temperature change and switches
off heating system
Room temperature increases
Room temperature decreases
Thermostat senses temperature change and switches
on heating system
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Concept Map
The Endocrine System
regulates
by meansof the
by meansof the
by meansof the
by meansof the
by meansof the
by meansof the
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PMS SymptomsCause Unknown 70 80 experience
these symptoms

• Weight gain
• Breast swelling
• Water retention
• Backache
• Cramps!!!
• Acne
• Fatigue
• Diarrhea, constipation, nausea
• Insomnia, headache, loneliness

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The Endocrine System