Body Fluids

Topics: Endocrine system, Hormone, Hypothalamus Pages: 18 (2316 words) Published: May 10, 2013
Chapter 45

Hormones and the Endocrine System
PowerPoint Lectures for Biology, Seventh Edition

Lectures by Ching-wei Luo

Hormone (from the Greek horman, to excite)

• Overview: The Body’s Long-Distance Regulators • Hormone definition: a chemical signal secreted into the circulatory system and communicates regulatory messages within the body

• Hormones may reach all parts of the body
But only certain types of cells (target cells) are equipped to respond Q

Two systems act individually and together in regulating an animal’s physiology

Endocrine system
Constituted by hormone–secreting cells and glands Secretes hormones that coordinate slower but longer-acting responses to stimuli “ductless” 升糖激素

Two systems act individually and together in regulating an animal’s physiology

Nervous system
Conveys high-speed electrical signals along specialized cells called neurons rapid messages control the movement of body parts


Secrete signal molecules

Endocrine cell


neurosecretory cells: release neurohormones into the blood
Pathway Stimulus Example Low blood glucose Receptor protein Pancreas secretes glucagon ( ) Endocrine cell Blood v essel Pathway Stimulus Example Suckling Pathway Stimulus Example Hy pothalamic neurohormone released in response to neural and hormonal signals

Sensory neuron
Hypothalamus / posterior pituitar y

Sensory neuron

Neurosecretory cell Posterior pituitary secretes oxytocin ( )

Neurosecretory cell Hy pothalamus Blood v essel secretes prolactinreleasing hormone ( )

Blood v essel Target effectors Liv er


Glycogen breakdown,
glucose release into blood

Target effectors

Smooth muscle in breast Endocrine cell

Anterior pituitary secretes prolactin ( )


Simple endocrine pathway


Milk release

Blood v essel

Homeostasis Feedback •negative •positive

Simple neurohormone pathway
Target effectors Mammary glands

Milk production Response


Simple neuroendocrine pathway

Hormone composition
Three major classes of molecules function as hormones in vertebrates •Proteins and peptides (soluble) •Amines derived from amino acids (soluble) •Steroids (insoluble)

Signaling by any of these molecules involves three key events •Reception •signal transduction •response

Water-soluble hormones act on cell-surface receptors
Receptor • embedded in the plasma membrane Signal transduction •converts an extracellular chemical signal to a intracellular response Response Cytoplasmic response Nuclear response eg: Glucagon (an 8-aa peptide) Camouflage mechanism SECRETORY CELL Hormone molecule VIA BLOOD Signal receptor TARGET CELL

Signal transduction pathway Cytoplasmic response


DNA Nuclear response NUCLEUS

(a) Receptor in plasma membrane

Intracellular Receptors for Lipid-Soluble Hormones •Steroids (estrogens, progesterone), thyroid hormones, and the SECRETORY hormonal form of vitamin D CELL Hormone molecule VIA BLOOD

Hormones: • mostly nonpolar (lipid–soluble) diffusible Receptor: • located in the nucleus or trapped in the cytoplasm

TARGET CELL Signal receptor Signal transduction and response


Signal transduction •usually perform the entire task of transducing signals within a target cell.

Synthesis of specific proteins (b) Receptor in cell nucleus

The same hormone may have different effects on target cells that have A
Response A

Response B

•Different receptors for the hormone •Different proteins for carrying out the response eg. Epinephrine (腎上腺素) : fight–or–flight hormone

Responds to short-term stress Resulting in decreased blood flow to the digestive tract and increased delivery of glucose to major skeletal muscles. Different receptors Epinephrine different cell responses Epinephrine Epinephrine

α receptor

β receptor

β receptor
Glycogen deposits

Vessel constricts

Vessel dilates

Continue Reading

Please join StudyMode to read the full document

You May Also Find These Documents Helpful

  • Fluid and Electrolytes Essay
  • 13B Distribution and constiuents of fluids P3 M2 Essay
  • Hsc Visual Arts: Artists Who Use Bodily Fluids in Their Work Essay
  • Fluids Essay
  • Fluid Mechanics Experiment : Series and Parallel Pump Essay
  • Body of Work Essay
  • The Body by Stephen King Essay
  • A Description of Fluid Mechanics Essay

Become a StudyMode Member

Sign Up - It's Free