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Chapter 31 Endocrine Control (Sections 31.1 - 31.5). 31.1 Hormones in the Balance.

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31 1 hormones in the balance
31.1 Hormones in the Balance
  • Some synthetic chemicals, such as DDT (pesticide), PCBs (used in electronic products, caulking, and solvents), and Atrazine (herbicide) are endocrine disrupters that harm the environment and threaten human health
  • endocrine disrupter
    • Synthetic chemical that adversely affects hormone production or function
costs of herbicide applications
Costs of Herbicide Applications
  • Atrazine keep cornfields nearly weed-free – it also interferes with sexual development in amphibians
31 2 vertebrate endocrine system
31.2 Vertebrate Endocrine System
  • Animal cells communicate with adjacent cells by way of gap junctions, neurotransmitters, and local signaling molecules
  • Animal hormones travel through the blood and can carry signals between cells in distant parts of the body
  • All hormone-secreting glands and cells in a body constitute the animal’s endocrine system
mechanisms of intercellular signaling
Mechanisms of Intercellular Signaling
  • Signaling molecules exert effects only when they bind to a matching receptor on or inside a “target” cell
  • Local signaling molecules diffuse a short distance through interstitial fluid and bind to nearby cells
    • Example: Prostaglandins released by injured cells activate pain receptors and increase local blood flow
  • Animal hormones circulate through the bloodstream, and exert their effects on a greater number of cells
key terms
Key Terms
  • local signaling molecule
    • Chemical signal, such as a prostaglandin, that is secreted by one cell and affects neighboring cells in an animal body
  • animal hormone
    • Intercellular signaling molecule secreted by an endocrine gland or cell
discovery of hormones
Discovery of Hormones
  • Physiologist E. Starling coined the term “hormone” to describe his discovery of secretin (the hormone that stimulates the pancreas to secrete bicarbonate)
  • Endocrine glands and other structures that secrete hormones are collectively referred to as an animal’s endocrine system
  • endocrine system
    • Hormone-producing glands and secretory cells of a vertebrate body
slide9

hypothalamus

closer view of the hypothalamus and pituitary gland

The Endocrine System

Hypothalamus

Makes and secretes releasers and inhibitors, hormones that act in the anterior lobe of the pituitary. Also makes antidiuretic hormone and oxytocin, which are stored in and released from the posterior lobe of the pituitary.

pituitary gland

Pineal gland

Makes and secretes melatonin (affects sleep/wake cycles, onset of puberty).

Pituitary gland

Anterior lobe makes and secretes

ACTH, TSH, LH, FSH (stimulate secretion by other endocrine glands), prolactin (acts on mammary glands) and growth hormone (affects overall growth). Posterior lobe secretes antidiuretic hormone (acts on kidneys) and oxytocin (acts on uterus and mammary glands). Both are made in the hypothalamus.

Thyroid gland

Makes and secretes thyroid hormone (metabolic and developmental effects) and calcitonin (lowers blood calcium).

Parathyroid glands (four)

Make and secrete parathyroid hormone (raises blood calcium level).

Adrenal glands (one pair)

Adrenal cortex makes and secretes cortisol (affects metabolism, immune response), aldosterone (acts in kidneys), small amount of sex hormones. Adrenal medulla makes and secretes norepinephrine and epinephrine, which prepare body for exciting or dangerous situations.

Thymus gland

Makes and secretes thymosins (act in maturation of T cells, a type of white blood cell).

Pancreas

Makes and secretes insulin (lowers blood glucose level) and glucagon (raises blood glucose level).

Ovaries (one pair of female gonads)

Make and secrete progesterone and estrogens (affect primary sex organs and influence secondary sexual traits).

Testes (one pair of male gonads)

Make and secrete testosterone and other androgens (affect primary sex organs and influence secondary sexual traits).

Fig. 31.2, p. 505

animation major human endocrine glands
ANIMATION: Major human endocrine glands

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neuroendocrine interactions
Neuroendocrine Interactions
  • The endocrine system and nervous system are closely linked
    • Hormones affect nervous processes such as sleep/wake cycles, emotion, mood, and memory
    • The nervous system affects hormone secretion
  • Both respond to signals from the hypothalamus, and both affect the activity of the same organs
key concepts
Key Concepts
  • The Vertebrate Endocrine System
    • Hormones and other signaling molecules regulate the pathways that control metabolism, growth, development, and reproduction
    • Nearly all vertebrates have an endocrine system composed of the same hormone-producing structures
31 3 the nature of hormone action
31.3 The Nature of Hormone Action
  • For a hormone to have an effect, it must bind to receptors on or inside a target cell
  • Hormones initiate responses in different ways, but in all cases, binding to a receptor is reversible and the response declines over time
reception transduction response
Reception, Transduction, Response
  • Signal processing is a three-step process:

Signal Reception

Signal Transduction

Cellular Response

  • A chemical signal binds to a receptor on a target cell, the signal is transduced (converted to a form that acts in the receiving cell), and the target cell makes a response
types of hormones
Types of Hormones
  • Animal hormones are chemical signals derived from either cholesterol or amino acids
  • Steroid hormones are lipid soluble and derived from cholesterol; they enter cells and bind to receptors inside them
  • steroid hormone
    • Hormone such as testosterone that is derived from cholesterol
types of hormones cont
Types of Hormones (cont.)
  • Peptide and protein hormones are derived from amino acids
  • They bind to receptors in the cell membrane
  • Binding often triggers formation of a second messenger, a molecule that elicits changes inside the cell
intracellular receptors
Intracellular Receptors
  • Steroid hormones form a hormone-receptor complex by binding to a receptor in the cytoplasm or nucleus
  • The hormone-receptor complex binds to a promoter near a hormonally regulated gene
  • Transcription and translation result in a protein product, such as an enzyme, that carries out the target cell’s response to the signal
slide20

Steroid Hormone Action

A steroid hormone molecule is moved from blood into interstitial fluid bathing a target cell.

1

Being lipid soluble, the hormone easily diffuses across the cell’s plasma membrane.

2

3

The hormone diffuses through the cytoplasm and nuclear envelope. It binds with its receptor in the nucleus.

The resulting mRNA moves into the cytoplasm and is transcribed into a protein.

receptor

5

4

The hormone– receptor complex triggers transcrip-tion of a specific gene.

hormone– receptor complex

A Example of steroid hormone action inside a target cell.

gene product

Fig. 31.3a, p. 507

animation hormones and target cell receptors
ANIMATION: Hormones and target cell receptors

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receptors at the plasma membrane
Receptors at the Plasma Membrane
  • Peptide and protein hormones bind to receptor proteins in a target cell’s plasma membrane
  • Binding causes a second messenger to form, which causes more cellular changes
  • second messenger
    • Molecule that forms inside a cell when a hormone binds at the cell surface
    • Sets in motion reactions that alter activity inside the cell
slide24

Peptide Hormone Action

A peptide hormone molecule, glucagon, diffuses from blood into interstitial fluid bathing the plasma membrane

of a liver cell.

1

unoccupied glucagon receptor at target cell’s plasma membrane

cyclic AMP

+ Pi

ATP

2

Glucagon binds with a receptor. Binding activates an enzyme that catalyzes the formation of cyclic AMP from ATP inside the cell.

3

Cyclic AMP activates another enzyme in the cell.

5

4

The enzyme activated by cyclic AMP activates another enzyme, which in turn activates another kind that catalyzes the breakdown of glycogen to its glucose monomers.

The enzyme activated by cyclic AMP

also inhibits glycogen synthesis.

B Example of peptide hormone action inside a target cell.

Fig. 31.3b, p. 507

steroid hormone receptors
Steroid Hormone Receptors
  • Some cells have receptors for steroid hormones at the plasma membrane
  • Binding a steroid hormone triggers a fast response by way of a second messenger, or by altering a property of the membrane
  • Example: When aldosterone binds to target cells in kidneys, target cells quickly become more permeable to sodium ions
receptor function and diversity
Receptor Function and Diversity
  • Hormone receptors are proteins
  • Mutations can result in receptors with a lowered capacity for binding hormone, or none at all
  • Variations in receptor structure also affect responses to hormones; different tissues often have receptor proteins that respond in different ways to binding of the same hormone
example adh receptor diversity
Example: ADHReceptor Diversity
  • ADH (antidiuretic hormone) binds to kidney cells and helps maintain solute concentrations in the internal environment
  • ADH also binds to receptors in blood vessels and helps maintain blood pressure by causing vessels to narrow
  • ADH also binds to brain cells and influences sexual and social behavior
key concepts1
Key Concepts
  • Signaling Mechanisms
    • A hormone travels through the blood and acts on any cell that has receptors for it
    • Receptor activation leads to transduction of the signal and a response in the targeted cell
    • Hormones are derived from either cholesterol or amino acids
31 4 the hypothalamus and pituitary gland
31.4 The Hypothalamus and Pituitary Gland
  • The hypothalamus and pituitary gland deep inside the brain control the activities of many other endocrine glands
  • hypothalamus
    • Forebrain region that controls processes related to homeostasis and has endocrine functions
  • pituitary gland
    • Pea-sized endocrine gland in the forebrain that interacts closely with the adjacent hypothalamus
hypothalamus and pituitary gland
Hypothalamus and Pituitary Gland
  • The hypothalamus connects structurally and functionally with the two lobes of the pituitary gland
slide31

Hypothalamus and Pituitary Gland

hypothalamus

posterior

lobe of

pituitary

anterior

lobe of

pituitary

p. 508

functions of the hypothalamus
Functions of the Hypothalamus
    • The hypothalamus is the main center for control of the internal environment
  • Axons of neurons in the hypothalamus extend into the posterior pituitary, where they release oxytocin and antidiuretic hormone
    • Releasing hormones and inhibiting hormones secreted by the hypothalamus control the secretion of hormones made by the anterior lobe of the pituitary
key terms1
Key Terms
  • releasing hormone
    • Hormone that is secreted by one endocrine gland and stimulates secretion by another
  • inhibiting hormone
    • Hormone that is secreted by one endocrine gland and discourages secretion by another
posterior pituitary hormones
Posterior Pituitary Hormones
  • The posterior pituitary secretes hormones synthesized in the hypothalamus:
    • Oxytocin targets smooth muscle in mammary glands during nursing and the uterus during birth
    • Antidiuretic hormone concentrates the urine by increasing reabsorption of water in kidney tubules
posterior pituitary function
Posterior Pituitary Function
  • Cell bodies of secretory neurons in hypothalamus synthesize ADH or oxytocin
  • ADH or oxytocin moves downward inside axons of secretory neurons and accumulates in the axon terminals
  • Action potentials trigger release of hormones, which enter blood capillaries in the posterior lobe of the pituitary
  • Blood vessels carry hormones to the general circulation
slide37

Posterior Pituitary Function

Cell bodies of secretory neurons in hypothalamus synthesize ADH or oxytocin.

1

The ADH or oxytocin moves downward inside the axons of the secretory neurons and accumulates in the axon terminals.

2

Blood vessels carry hormones to the general circulation.

4

Action potentials trigger the release of these hormones, which enter blood capillaries in the posterior lobe of the pituitary.

3

Fig. 31.4, p. 509

anterior pituitary hormones
Anterior Pituitary Hormones
  • The anterior pituitary makes hormones and secretes them in response to hormones from the hypothalamus
  • Four anterior pituitary hormones (ACTH, TSH, FSH, LH) hormones target other glands
  • Prolactin encourages milk production
  • Growth hormone (GH) secreted by the anterior pituitary acts throughout the body
growth hormone disorders
Growth Hormone Disorders
  • Pituitary gigantism and dwarfism result from mutations that affect GH secretion or GH receptors
  • Over-secretion of growth hormone in children leads to pituitary gigantism
  • Low GH secretion in childhood causes pituitary dwarfism
pituitary gigantism
Pituitary Gigantism
  • One of the world’s tallest men, Bao Xishun stands 2.36 meters (7 feet 9 inches) tall
anterior pituitary function
Anterior Pituitary Function
  • Neurons in the hypothalamus secrete inhibitors or releasers into the stalk that connects to the pituitary
  • Blood carries inhibitors or releasers to the anterior pituitary
  • Inhibitors or releasers diffuse out of capillaries in the anterior pituitary and bind to target cells
  • Encouraged by a releaser, anterior pituitary cells secrete a hormone that enters the general blood circulation
slide43

Anterior Pituitary Function

Cell bodies of secretory neurons in hypothalamus synthesize inhibitors or releasers that are secreted into the stalk that connects to the pituitary.

1

The inhibitors or releasers picked up by capillaries in the stalk get carried in blood to the anterior pituitary.

2

When encouraged by a releaser, anterior pituitary cells secrete hormone that enters blood vessels that lead into the general circulation.

4

The inhibitors or releasers diffuse out of capillaries in the anterior pituitary and bind to their target cells.

3

Fig. 31.5, p. 509

animation posterior pituitary function
ANIMATION: Posterior pituitary function

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key concepts2
Key Concepts
  • A Master Integrating Center
    • In vertebrates, the hypothalamus and pituitary gland deep inside the brain are connected structurally and functionally
    • Together, they coordinate activities of many other glands
31 5 sources and effects of other vertebrate hormones
31.5 Sources and Effects of Other Vertebrate Hormones
  • In addition to major endocrine glands, the human body has hormone-secreting cells in many organs:
    • Parts of the gut secrete secretin and other hormones that affect appetite and digestion
    • Adipose (fat) tissue makes leptin, a hormone that acts in the brain and suppresses appetite
    • Kidneys secrete erythropoietin, a hormone that stimulates maturation and production of red blood cells
    • The heart makes atrial natriuretic peptide, that stimulates the kidneys to excrete water and salt
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