Chemical signals in animals
Dec 27, 2015
Chemical signals in animals
KeywordsReading 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 outside of organisms
• Pheromones
• Prey tracking by rattlesnakes
Pheromone
• A small volatile chemical signal that functions in communication between animals
• Often in mate attraction
Rattlesnakes (research of Dr. Ken Kardong Zoology WSU)
• 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
• Hormone– Chemical signal secreted into body fluids
(usually blood)– Effective in minute amounts
Types of signaling in endocrine system
Hormones act on specific target cells in two ways
• Surface receptors
• Within target cells (internal receptor)
Surface receptor - often amino acid derived hormone
Internal receptor - often steroid hormones
Action of steroids
Two specific 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
P. 906
• 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
P. 909
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