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 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