Endocrine System

1
Endocrine System

• Role of the Endocrine System
• Hormones Types
• Transport of Hormones
• Interaction of Hormones with Target Cells
• Effects of Hormones on Target
• Control Mechanisms of Endocrine Glands
• Endocrine Organs
• Pituitary (Anterior and Posterior)
• Thyroid
• Adrenals (Cortex, Medulla)
• Pancreas

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The Endocrine System

• A more broad-based and long-lasting communication
  system than the nervous system
• Uses chemical messages (hormones) that are
  released into the blood
• Hormones control several major processes
• Reproduction
• Growth and development
• Mobilization of body defenses
• Maintenance of much of homeostasis
• Regulation of metabolism

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Types of Hormones

• Protein-based hormones
• Steroid hormones
• Prostaglandins and catecholamines

Insulin
Growth hormone
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Hormones as Chemical Messengers
Endocrine gland (source) Target organs or
glands
Hormones move through the bloodstream to target
organs
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Hormone Interaction with Target Cells

• Hormones bind to receptors sticking out from the
  plasma membrane of target cells or within target
  cells

growth factor insulin
epinephrine
Hormones
Receptors
Examples of receptors found in the plasma
membrane of cells
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Effects Caused by Hormones

• Changes in electrical state of the cell,
  stimulating change
• Causes enzymes to be made, changing metabolic
  abilities of target cell
• Turn on or off enzymes that alter metabolism
  inside cell
• Stimulate cell division and multiplication
• Turn on certain genes

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Control Mechanisms of Endocrine Glands

• Hormonal Chemical stimulus (i.e. endocrine
  glands are activated by other hormones)

• Humoral/Blood-Based Changing blood levels of
  certain ions stimulate hormone release

Neural Nerve impulses stimulate hormone release
most are under control of the sympathetic nervous
system
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Location of Major Endrocrine Organs
Figure 9.3
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Pituitary Gland
Flip and enlarge
Nervous system that hormones can drip down on
blood portal system
glandular tissue nervous tissue
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Hormones of the Anterior Pituitary

• Six anterior pituitary hormones
• Two affect non-endocrine targets
• Four stimulate other endocrine glands (tropic
  hormones)
• Characteristics of all anterior pituitary
  hormones
• They are proteins (or peptides)
• They act through second-messenger systems
• They are regulated by hormonal stimuli, mostly
  negative feedback

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Hormones of the Anterior Pituitary
Causes aldosterone, glucocorticoid, or androgen
release
Increases bone and skeletal mass
Causes milk secretion in breasts
Stimulates thyroid hormone secretion
Causes follicle and sperm maturation, ovulation
and testosterone production
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Hormones of the Posterior Pituitary
Stimulates uterine muscle contraction in labor
and intercourse causes milk ejection
Inhibits diuresis (urine production) and
increases blood pressure
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Thyroid Gland

• Consists of two lobes and a connecting isthmus

Thyroid hormone Controls rate of cellular
respiration. All body cells are
targets. Calcitonin Decreases blood calcium
levels by causing bone calcium deposition. Made
by parafollicular cells.
Figure 9.6
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Thyroid Hormone

• Lack of Dietary Iodine Goiter
• Hyposecretion of thyroxine
• ( hypothyroidism in adults)
• Hyperthyroidism (Grave's disease)

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Calcitonin (Calcium deposition)

• Decreases blood calcium levels by causing its
  deposition on bone
• Antagonistic to parathyroid hormone
• Produced by C (parafollicular) cells

Figure 9.9
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Adrenal Glands

• Two parts that act as if separate glands
• Cortex outer glandular region in three layers
• Medulla inner neural tissue region
• Sits on top of the kidneys

Ad-renal both mean upon or Epi-nephros
next to the kidney

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Adrenal Hormones and Their Locations
Adrenal Cortex Outer portion produces
mineralocorticoids like aldosterone (zona
glomerulosa) Middle layer produces
glucocorticoids like cortisone and cortisol (zona
fasciulata) Innermost layer produces androgens
like estrogens and testosterone (zone
reticularis) Medulla produces catecholoamines
like epinephrine and norepineprhine
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Adrenal Cortex (Outer Portion)
Aldosterone release causes salt and water
retention, increasing blood pressure
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Hormones of the Innermost Cortex Layer

• Sex hormones (steroids)
• Produced in the inner layer of the adrenal cortex
• Androgens (male) and some estrogen (female) --
  both produced regardless of gender
• Hypersecretion causes masculinization (regardless
  of gender) - most obvious effects in females
• Hyposecretion causes Addison's disease

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Hormones of the Adrenal Medulla

• Produces two similar hormones (catecholamines)
• Epinephrine
• Norepinephrine
• These hormones prepare the body to deal with
  short-term stress
• Sympathetic system stimulates catecholamine
  release in fight or flight increased heart rate,
  blood pressure, blood gluocose, respiratory rate

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Pancreatic Islets

• The pancreas is a mixed gland
• The islets of the pancreas produce hormones
• These hormones are antagonists that maintain
  blood sugar homeostasis

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Pancreatic Islets
Insulin Allows glucose to cross plasma
membranes into cells from beta cells
(hypoglycemic hormone) Glucagon Allows
glucose to enter the blood from alpha cells
(hyperglycemic hormone)
Figure 9.13
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Pancreatic Hormones and Blood Sugar
Figure 9.14