Download Lecture 9: Chemical signals in animals

Chemical signals in animals
Keywords
Reading Ch. 45
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Endocrine system
Hormone
Target cell
Neurosecretory cell
Steroid
Amino acid derived
hormone
• Surface receptors
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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