Presentation on theme: "Chemical Signals in Animals. A hormone is a chemical secreted into the blood (or other body fluids) that communicates a regulatory message Secreted by."— Presentation transcript:
A hormone is a chemical secreted into the blood (or other body fluids) that communicates a regulatory message Secreted by endocrine glands (“ductless glands”) May affect whole body or only target cells Important for maintaining homeostasis.
Chemical Signals in Animals Nervous system and endocrine system are very closely interrelated Some hormones are secreted by nerve cells Some act as both hormones and neurotransmitters.
Homeostasis The thyroid makes thyroxin (T4), which controls metabolic rate and other functions. T4
Homeostasis Thyroid stimulating hormone (TSH) is made by the anterior pituitary. T4 TSH
Homeostasis TSH releasing hormone (TRH) is made by the hypothalamus. T4 TSH TRH
Homeostasis A buildup of T4 signals the hypothalamus to stop making TRH. T4 TSH TRH
Homeostasis A buildup of TSH does the same thing. T4 TSH TRH
Hormonal Signals Some are local and affect only neighboring cells. These are broken down within seconds Tropic hormones affect other endocrine glands Pheromones affect other organisms Receptors can be on the cell surface or intracellular.
Some Important Glands Hypothalamus & pituitary Control of other glands, Growth (GH) Menstruation & lactation Many other functions.
Some Important Glands Pineal Biological rhythms Thyroid & Parathyroid Homeostasis (calcitonin & PTH) Pancreas Blood glucose (insulin & glucagon).
Some Important Glands Adrenal Stress (epinephrine & norepinephrine) Gonadal Androgens, estrogen, progestin.