Chemical signals in animals
Keywords
Reading Ch. 45
Endocrine system
Hormone
Target cell
Neurosecretory cell
Steroid
Amino acid derived hormone
Surface receptors
Internal receptors
Action of steroids
Glucose homeostasis
Insulin
Glucagon
Epinephrine
Norepinephrine
ACTH
Chemical signals
Inside and outside an organism
Chemical signals outside (examples)
Pheromones
Prey tracking by rattlesnakes (research of Dr. Ken Kardong Zoology WSU)
Pheromone
A small volatile chemical signal that functions in communication between animals
Codling moth (leaves holes in apples)
Controlled by spraying apples
Leaf roller moth (Pandemis sp.)
Competes with codling moth -- spraying caused leaf roller population to explode
Dr. Kemet Spence developed a way of using genetically engineered bacteria to control codling moth
Rattlesnakes
Bite prey, inject venom, prey runs away, snake can track down the prey
Follows a scent trail left by bitten prey.
Doesn’t matter if venom glands have been ligated
Don’t know what the signal is.
Will focus on chemical signals inside organisms
Two regulatory systems coordinate internal body functions
Nervous system (will deal with in a later lecture)
Endocrine system (focus of today’s lecture)
Endocrine system definition
The internal chemical communication system involving hormones
The endocrine and nervous systems often function inseparably
We’ll look at specific examples that illustrate this.
Hormone
Chemical signal secreted into body fluids (usually blood)
Effective in minute amounts
Types of hormones
Steroid
Amino acid derived
Steroid hormones
Made from cholesterol
Include sex hormones
Amino acid derived
Single amino acids
Peptides
Proteins
glycoproteins
Hormones act on specific target cells in two ways
Surface receptors
Within target cells (internal receptor)
Surface receptor
Internal receptor
Action of steroids
Two examples of hormone action
Glucose homeostasis
Stress and the adrenal gland
Glucose homeostasis
Homeostasis = The steady-state physiological condition of the body
Glucose = major fuel of cellular respiration
Normal blood glucose level = 900 mg/L
How is this regulated?
First look at when glucose levels are too high
High blood glucose causes beta cells to release insulin
Summary
Beta cells release insulin
Insulin causes body cells and liver to take up glucose
Glucose levels restored
What happens if you need to increase blood glucose?
Low blood glucose causes alpha cells to release the hormone glucagon
Glucogon stimulates the liver to break down glycogen releasing glucose
Summary
Low blood glucose causes alpha cells to release the hormone glucagon
Glucogon stimulates the liver to break down glycogen releasing glucose
Glucose homeostasis
Example of use of amino-acid derived hormones: insulin and glucagon are peptides
Surface receptors on target cells
Diabetes mellitus
Greek = copious urine, honey
Type I - autoimmune disorder - cells of pancreas are targeted - no ability to produce insulin - usually occurs during childhood
Type II (90%) - reduced responsiveness of target cells or insulin deficiency-usually occurs after age 40
Stress and the adrenal gland
Short-term response - Epinephrine (adrenaline) and norepinephrine
Long-term response - ACTH and corticosteroids
Short-term stress: medulla of the adrenal gland
Some effects of epinephrine and norepinephrine
Glycogen broken down to glucose
Increased blood pressure, breathing, metabolic rate
Example of:
Use of neurosecretory cells
Amino acid-derived hormones
Long-term stress: cortex of the adrenal gland
Corticosteroids (mineral- and gluco- corticoids) released by adrenal cortex
Some effects: increased blood volume and blood pressure, breakdown of protein and fats
Example of:
Interaction between nervous and endocrine systems
Use of steroid hormones