Endocrine System Chapter 16

Hormones Released from glands “Looking for” receptors on cells, or target cells Two types of hormones Steroid: cholesterol Non steroid: proteins,modified amino acids

Peptide and Steroid Hormones Have Different Modes of Signaling Non-Steroid (Peptide) Hormones are protein based hormones. Responses are faster but do not last as long. Steroid Hormones are lipid based These responses take longer to initiate but have a longer duration.

Hormones in Action Steroid Hormone Target cell membrane mRNA Cytoplasm Protein synthesis Altered cellular function Receptor Hormone- receptor complex Nucleus DNA Nonsteroid hormone (first messenger) Receptor Target cell membrane cAMP (second messenger) Enzyme activities Altered cellular function Cytoplasm Nucleus

Endocrine Glands Hypothalamus The hypothalamus makes hormones that control the pituitary gland. In addition, it makes hormones that are stored in the pituitary gland. Pituitary gland The pituitary gland produces hormones that regulate many of the other endocrine glands. Parathyroid glands These four glands release parathyroid hormone, which regulate the level of calcium in the blood. Thymus During childhood, the thymus releases thymosin, which stimulates Tcell development. Adrenal glands The adrenal glands release epinephrine and nonepinephrine, which help the body deal with stress. Pineal gland The pineal gland releases melatonin, which is involved in rhythmic activities, such as daily sleep-wake cycles. Thyroid The thyroid produces thyroxine, which regulates metabolism. Pancreas The pancreas produces insulin and glucagon, which regulate the level of glucose in the blood. Ovary The ovaries produce estrogen and progesterone. Estrogen is required for the development of secondary sex characteristics and for the development of eggs. Progesterone prepares the uterus for a fertilized egg. Testis The testes produce testosterone, which is responsible for sperm production and the development of male secondary sex characteristics

Animals Have Two Systems of Internal Communication and Regulation. Nervous System Movement of body parts as a quick response to sudden environmental changes. Pulling your hand a way from a hot flame. Endocrine System Longer lasting and slower response Chemical response Homeostasis depends on the overlap of the nervous and endocrine systems.

endocrine system glandsproducts body The endocrine system is made up of glands that release their products into the bloodstream. These products deliver messages throughout the body. Nervous SystemEndocrine System NeuronBloodstream FastSlow Small # of cells effected Large # of cells effected

Endocrine Glands Endocrine glands Ductless glands that secrete substances directly into the blood stream. Pancreas secretes insulin into the blood stream Exocrine Glands These glands have ducts Secrete mucus, sweat from glands through ducts Pancreatic duct secretes digestive enzymes.

Nervous System and Endocrine System are Closely Related Many endocrine organs contain nervous tissue composed of neurosecretory cells (nervous system and endocrine system working in concert) These cells secrete hormones in response to a stimulus. The suckling of an infant stimulates a nervous response which is sent to the brain. The result is the hypothalamus tells the pituitary gland to secrete oxytocin (a chemical signal) that causes the secretion of milk. Epinephrine is a hormone and a neurotransmitter. Produced by adrenal glands as the “fight or flight” hormone. Also acts as a neurotransmitter that is involved in nerve cell communication.

Positive and Negative Feedback Loops are Important in Maintaining Homeostasis. A rise in blood calcium causes calcitonin to be released from the thyroid gland which triggers calcium to be put into bone formation. (osteoblasts) A lack of blood calcium causes the parathyroid gland to release parathyroid hormone to release calcium back into blood from bones. (osteoclasts)

Calcium Balance

Goiter Thyroid enlarges due to lack of iodine, necessary for thyroid hormone production (pg. 504)

Chemical Signals Are Important in the Endocrine System Some chemicals have to travel long distances to their target cells while others act locally. The receptors on the target cells are specific and the same hormone can elicit different responses depending on the target cell and its receptor. Acetylcholine Skeletal muscle contraction Relaxation of heart muscle

Growth Factors Growth hormone (secreted by anterior pituitary somatotrophs) stimulates rapid entrance of amino acids from blood into cells by stimuating growth factors production in liver Accelerated protein anabolism within cells increases growth rate Nitric Oxide Stimulate cell destruction in the immune system Stimulate vasodilatation 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. Local Regulators

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.

Not enough GH Too much GH

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. Examples: ADH –water absorption in the kidney Oxytocin-uterine contractions and milk production in the mammary glands.

Pancreas

By mea ns of the Overview Growth Water balance ReproductionMetabolism Calcium and glucose levels Response to stress The Endocrine System Pituitary Ovaries TestesThyroidPancreasAdrenals Parathyroids regulates By means of the By means of the By means of the By means of the By means of the