The Endocrine System (Chap 39, Sections 1 & 2) Maintaining Homeostasis 1

Introduction: What happens at puberty? The hypothalamus releases a chemical called GnRH. GnRH stimulates the pituitary gland to release two more hormones: –luteinizing hormone (LH for short) –follicle-stimulating hormone (FSH for short) Girls and boys have both of these hormones. The hormones act in different ways depending on what sex you are. Girls usually start puberty 8 – 13. Boys usually start puberty 10 – 15. 2

Boys These hormones travel through the blood & give the testes the signal to begin production of sperm & testosterone. (need sperm to reproduce) Get taller last 2 -3 years, can grow up to 4inches in a year. Gain weight Shoulders get wider, body become more muscular. Voices get deeper. Grow hair under arms, pubic areas, & face. 3

Girls Gain weight – this is NORMAL! Girls' bodies usually become curvier They gain weight on their hips Breasts develop Menstrual cycle begins Grow hair under arms & in pubic areas 4

The Endocrine System I.Function: Maintains homeostasis using hormones. 1.An endocrine (ductless) gland secretes its products (hormones) directly into the blood stream. 2.Hormones are slow working but long lasting. 3.Hormones can only effect specific target cells.  What do we call glands that release their products through ducts to the outside of the body or into body cavities?  Exocrine glands Examples: Sweat, tears, & digestive juices 5

Hypothalamus Pituitary gland Parathyroid glands Thymus Adrenal glands Thyroid Pancreas Ovary Testis Endocrine Gland Locations (Fig. 39-2) 6

II. Endocrine Gland Types & Functions A. Pituitary – Secretes 9 hormones that directly regulate many body functions, & controls the actions of several other endocrine glands. ** The pituitary gland is controlled by the hypothalamus 7

Gigantism – an excess of growth hormone Too much GH During childhood Development. 8

Pituitary Dwarfism – Too little growth hormone Too little GH During childhood Development. 9

B.Hypothalamus – Produces hormones that control the pituitary gland, & makes hormones stored in the pituitary gland. C.Parathyroid – Releases parathyroid hormone which acts to maintain homeostasis of the calcium levels in the blood and bones. D.Thymus – During childhood stimulates T cell development & proper immune response. E.Adrenal – Release epinephrine & norepinephrine which help the body respond to stress (flight or fight response). 10

F.Thyroid – Regulates the bodies metabolism by producing thyroxine (increases the rate of protein, carbohydrate & fat metabolism & also cellular respiration). G.Pancreas – produces insulin & glucagon which regulate the level of glucose in the blood. Signals liver to store or release glucose. H.Ovary – produces estrogen and progesterone. These produce primary and secondary sex characteristics and regulate the menstrual cycle and pregnancy. I.Testis – produces testosterone for sperm production and primary and secondary sex characteristics. 11

III. How do hormones work? A.Hormones belong to two groups – steroid hormones & non-steroid hormones. B. Steroid hormones 1. Made of lipids (fats) & can cross cell membranes directly into the cytoplasm and nucleus. 2. Binds to a receptor protein inside the cell. 3. This receptor activates genes that carry out the actions associated with the hormone. 12

C. Nonsteroid hormones – Cannot pass through the cell membrane. 1.Made of proteins & bind to receptors on the cell membrane surface. 2. This activates an enzyme on the inner surface of the cell membrane. 3. The enzyme activates secondary messengers to carry the signal 4. The second messenger activates or inhibits cell activities. 13

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 Steroid & Nonsteroid Hormones (fig. 39-3) 14

An Example of Endocrine Controlled Homeostasis Regulation of blood sugar levels 15

Room temperature increases Thermostat senses temperature change and switches on heating system Thermostat senses temperature change and switches off heating system Room temperature decreases Negative Feedback Example of Homeostasis (Fig. 35-4, p.895) IV.Negative feedback – your body’s response results in decreasing the effect of the stimulus, (e.g. body temperature). The effect is a relatively steady state is maintained. 16

regulates Concept Map by means of the Growth Water balance Reproduction Metabolism Calcium and glucose levels Response to stress The Endocrine System Pituitary Ovaries TestesThyroidPancreasAdrenals Parathyroids 17

PMS Symptoms Cause Unknown: 70 – 80% experience these symptoms Weight gain Breast swelling Water retention BackacheCramps!!!AcneFatigue Diarrhea, constipation, nausea Insomnia, headache, loneliness 18

19 The Endocrine System