Chemical Signals in Animals

Goiter

Two Primary Systems of Internal Communication and Regulation. Nervous System Quick responses to sudden environmental changes. Pulling your hand a way from a hot flame. Endocrine Longer lasting and slower response Chemical response Control of metamorphosis of a butterfly.

Endocrine Glands Endocrine glands Ductless glands that secrete substances directly into the blood stream. Exocrine Glands These glands have ducts Secrete mucus, sweat and digestive enzymes.

Nervous System and Endocrine System are Closely Related Many endocrine organs contain nervous tissue called neurosecretory cells. Secrete hormones in response to a stimulus. Epinephrine is a hormone and a neurotransmitter. Produced by adrenal glands as the “fight or flight” hormone and is a neurotransmitter that is involved in nerve cell communication.

Peptide Verse Steroid Hormones Peptide Hormones are protein based hormones. Signal Transduction Pathways. Response is faster but do not last as long. Steroid Hormones are lipid based Pass through the membrane and to a receptor in the cytoplasm that bind to a promoter and activate a gene. These responses take longer to initiate but have a longer duration.

Insects Possess Hormones that affect Metamorphosis

Local Regulators  Target Cells that are adjacent to the cells that are secreting the message.  Growth Factors  Proteins that stimulate cell proliferation –Nerve Growth Factor –Nitric Oxide  Stimulate cell destruction in the immune system  Stimulate vasodialation in the circulatory system  Functions as a neurotransmitter in the nervous system. –Prostaglandins  Modified fatty acids derived from lipids  Stimulate uterine contractions, fever, inflammation and the sensation of pain.  PGE and PGF are antagonistic and stimulate the contraction and dilation of blood vessels in the lung. –Pheromones  Chemical signals that serve as communication between animals.  Warning signals, territorial,markers.

Peptide Hormones and Second Messengers Cyclic AMP is a cytoplasmic messenger that is activated when a single hormone molecule binds to the receptor on the surface of the cell that initiates a cascade of biochemical reactions. Amplification of the response results in one hormone molecule activating the release of thousands of products. Epinephrine catalyzes glycogen hydrolysis.

Signal Transduction

Steroid Hormone Receptors

Hypothalamus and Pituitary Glands. Hypothalamus Controls the pituitary Neurosecretory cells release hormones that control the pituitary gland. Important connection between the endocrine and nervous system. Pituitary “Master Gland” Anterior and Posterior Posterior pituitary stores and releases hormones produced by the hypothalamus. Releases ADH –water absorption in the kidney Oxytocin-uterine contractions and milk production in the mamary glands.

Anterior Pituitary Produces its own hormones and releases Growth Hormone-Stimulate growth factors produced in the liver called somatomedins which stimulate cartilage and bone growth. Excessive GH production causes gigantism and acromegaly. GH deficiency causes hypopituitary dwarfism.

Midget  too little GH Giant  too much GH

Anterior Pituitary  Prolactin(PRL) –controls mammary gland growth and d the synthesis of milk in mammals. –delays metamorphosis in amphibians –regulates salt and water balance in fish.  Tropic hormones –Thyroid Stimulating Hormone (TSH)  Stimulates the release of Thyroxin –Follicle Stimulating Hormone (FSH) –Lutineizing Hormone (LH)  Involved in reproduction  Adrenocorticotropin (ACTH) –Causes the adrenal cortex to secrete steroid hormones involved in “fight or flight” responses.  Melanocyte Stimulating Hormone (MSH) –Involved in color changes in amphibians.  Endorphins and Enkephalins –Produced by certain neurons in the brain and inhibit pain reception.

Stimulation of the Anterior Pituitary Releasing factors are produced at the base of the hypothalamus and are released by capillaries in an area called the median eminence

Thyroid Gland

Calcium Balance

Pancreas

Adrenal Glands

Fight or Flight