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Chapter 45: Hormones & The Endocrine System . Steph Jones AP Biology Ms. Loughnane. Basics. Hormone: a chemical signal that is secreted into the circulatory system (usually the blood) and communicates regulatory messages within a body

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chapter 45 hormones the endocrine system

Chapter 45: Hormones &The Endocrine System

Steph Jones

AP Biology

Ms. Loughnane

  • Hormone: a chemical signal that is secreted into the circulatory system (usually the blood) and communicates regulatory messages within a body
  • Target cells are the cells that contain the specific receptor that only activates when that specific hormone is secreted
  • Two main systems involved are:

Nervous System & Endocrine System

control pathways
Control Pathways
  • Three major hormonal control pathways:

Endocrine, Neurohormone, Neuroendocrine.

  • Regulation by hormones:
  • Receptor detects stimulus and sends info to control center
  • After comparing the desired set point, the control center sends signal to an effector
  • The effectorresponds and sends a changing signal into the control pathways
  • After the effector sends out a changing signal into the pathways, it becomes either:
  • Negative feedback, where the effector response reduces the initial stimulus, and eventually the response stops


  • Positive Feedback, which reinforces the stimulus and leads to a greater response
  • Feedback regulates hormonal pathways used to maintain homeostasis
classes of hormones
Classes of Hormones
  • Proteins and Peptides - small polypeptide containing up to 30 amino acids (both are water-soluble)
  • Amines that come from Amino Acids (water-soluble)
  • Steroids (lipid-soluble)
  • Three Key Events:
  • Reception – occurs when the signal molecule binds to a specific receptor protein in or on target cell
  • Signal Transduction – events within target cell
  • Response – a change in cell behavior as a response to the stimulus and to maintain homeostasis
cell surface receptors for water soluble hormones
Cell-Surface Receptors for Water-Soluble Hormones
  • Most peptide/protein hormones that come from amino acids bind to receptors that are located inside the plasma membrane
  • Signal Transduction Pathway: a series of changes in cellular proteins that converts an extracellular chemical signal to specific intracellular response
cell surface receptors for water soluble hormones cont d
Cell-Surface Receptors for Water-Soluble Hormones (cont’d)
  • Binding causes a signal transduction pathway that leads to a response in cytoplasm or changes in gene expression

* Remember: the same hormone can have different effects on target cells that have:

  • Different receptors
  • Different signal transduction pathways
  • Different effector proteins
intracellular receptors for lipid soluble hormones
Intracellular Receptors for Lipid-Soluble Hormones
  • Intracellular receptors of steroid hormones transduce a signal within a target cell
  • The chemical signal activates the receptor which leads to the cell’s response
paracrine signaling
Paracrine Signaling
  • Paracrine Signaling: local regulators convey messages between neighboring cells
  • Faster than the long-distance endocrine signaling
paracrine signaling cont d
Paracrine Signaling (cont’d)
  • Local regulators greatly help maintain homeostasis

ex: nitric oxide (NO) is released by by blood vessels when blood oxygen level falls. NO activates an enzyme that relaxes smooth muscle cells, which dilates vessels and improves blood flow to tissues

  • Hypothalamus: a region of the lower brain that contains different sets of nuerosecretory cells
pituitary gland
Pituitary Gland
  • Pituitary Gland: At the base of

the Hypothalamus; has two parts:

- Posterior Pituitary: stores and secretes 2 hormones that are made by neurosecretory cells located in the hypothalamus

- Anterior Pituitary: make and secrete at least 6 hormones into the blood

tropic hormones
Tropic Hormones
  • Regulate the function of endocrine organs, and coordinate endocrine signaling throughout the body
posterior pituitary hormones
Posterior Pituitary Hormones
  • Releases 2 hormones:
  • ADH (antidiuretic hormone): kidney tubules
  • Oxytocin: mammary glands, uterine muscles
anterior pituitary hormones tropic effects only
Anterior Pituitary Hormones: Tropic Effects Only
  • thyroid-stimulating hormone (TSH): Thyroid
  • follicle-stimulating hormone (FSH): testes & ovaries
  • luteinizing hormone (LH): testes & ovaries
  • adrenocorticotropic hormone (ACTH): Adrenal cortex
anterior pituitary hormones nontropic effects only
Anterior Pituitary Hormones: Nontropic Effects Only
  • Prolactin: mammary glands
  • Endorphin: pain receptors in brain
  • Melanocyte-stimulating hormone (MSH): melanocytes
nonpituitary hormones
Nonpituitary Hormones
  • Help regulate metabolism, homeostasis, development, and behavior
  • There are 6 types: Thyroid, Parathyroid & Calcitonin, Insulin & Glucagon, Adrenal, Gonadal, Melatonin & Biorhythms
thyroid hormones
Thyroid Hormones
  • Thyroid Gland: two lobes on the ventral surface of the trachea, produce 2 hormones produced by the amino acid tyrosine: Triiodothyronine (T3) and Thyroxine (T4).
  • They stimulate metabolism, influence development and maturation
parathyroid hormone pth calcitonin
Parathyroid Hormone (PTH) & Calcitonin
  • Play the major role in calcium (Ca2+) homeostasis, control blood calcium levels
  • PTH raises blood Ca2+ levels when they drop and Calcitonin lowers Ca2+ levels when they rise
insulin glucagon
Insulin & Glucagon
  • Help maintain glucose homeostasis, the pancreas synthesizes them
  • Insulin lowers blood glucose levels and glucagon raises them
adrenal hormones adrenal medulla
Adrenal Hormones: Adrenal Medulla
  • Secreted by the Adrenal glands, two glands, adrenal cortex, outer portion and adrenal medulla, central portion
  • Epinephrine and norepinephrine are releasedbynuerosecretory cells in the adrenal medulla in response to stress or danger.

Adrenal Medulla

adrenal hormones adrenal cortex
Adrenal Hormones: Adrenal Cortex
  • The adrenal cortex releases glucocorticoids (influence glucose metabolism & immune system), mineralocorticoids (salt and water balance), and small amounts of sex hormones

Adrenal Cortex

gonadal sex hormones
Gonadal Sex Hormones
  • There are three sex hormones: androgens (ex. Testosterone), estrogens, and progestins

-Androgens stimulate development/maintenance of male reproductive system

- Estrogen maintain female reproductive system and female secondary sex characteristics

- Progestinsprepare/maintain uterus

  • Produced by the gonads, or testes and ovaries
  • Produced in both males and females, just in different amounts
melatonin and biorhythms
Melatonin and Biorhythms
  • Pineal gland in the brain secretes melatonin
  • The secretion of Melatonin is regulated by light/dark cycles and is related to biological rhythms with reproduction
  • They also contain endocrine system and nervous system interactions
  • Varied hormones regulate many different aspects of homeostasis
    • Molting in insects includes 3 different hormones
      • Brain hormone
      • Ecdysone
      • Juvenile Hormone
picture citations respectively
Picture Citations(respectively)