Homeostasis – Endocrine System Chapter 8

The Endocrine System – 8.1 Hormones  chemical regulators produced by cells in one part of the body that affect cells in another part of the body. Endocrine hormones  produced in glands and secreted directly into blood. The adrenal gland, on top of the kidneys secretes the hormone adrenaline

The Endocrine System – 8.1 Hormones  chemical regulators produced by cells in one part of the body that affect cells in another part of the body. Exocrine glands  secrete substances through ducts onto the body surface or into cavity. Mucous & sweat

The Endocrine System – 8.1 Hormone Classification Nontarget hormones – affect many tissues throughout the body Growth hormone long bone growth Increases calcium retention, and strengthens and increases the mineralization of bone Increases muscle mass Increases protein synthesis Stimulates the growth of all internal organs excluding the brain Reduces liver uptake of glucose Stimulates the immune system Target hormones – affect specific cells or tissues in the body Gastrin stimulates cells of the stomach to produce digestive enzymes.

The Endocrine System Chemical Messengers – how we know what we know? 1889  von Mering and Minkowski with dog pancreases If removed  slim and tired, ants If present  normal, no ants Pancreas controlled blood sugar Radioactive tracers Where hormones go and how they are broken down.

The Endocrine System Hormones do not affect all cells Two types of hormones Steroid Hormone  made from cholesterol, include sex hormones, rings of CHO Blood  ECF  Joins with receptor molecule in cytoplasm  complex enters nucleus  Joins chromatin which activates gene to start making a specific protein

The Endocrine System Protein Hormone  made of chains of AA, include insulin and growth hormone Blood  ECF  Joins to receptor site on outside of cell  Activates adenylyl cyclase  This enzyme converts ATP to cAMP  cAMP acts as a messenger activating enzymes in the cytoplasm.

The Pituitary Gland Gland at base of brain that, with hypothalamus, functions as a control centre coordinating the endocrine and nervous system. Produces and stores hormones which are regulated by the hypothalamus Posterior and Anterior lobes Posterior  stores and releases hormones (ADH, oxytocin) Anterior  produces its own hormones (GH, prolactin)

Hormones & Blood Sugar - 8.2 Pancreas contains two types of cells Digestive enzyme producing cells Hormone producing cells – islets of Langerhans: produce insulin (beta)  released when blood sugar goes up and causes appropriate cells to become permeable to glucose. produce glucagons (alpha)  released when blood sugar goes down and promotes the conversion of glycogen to glucose

Diabetes  Insufficient production or use of insulin After a meal you would experience hyperglycemia Kidneys  high concentration of glucose in nephron pulls water out of the body Three types - mellitus Type 1 (juvenile-onset)  early degeneration of beta cells, inject insulin to live, 10% of diabetics Type 2 (adult-onset)  decrease in insulin production or efficiency, treated with sulfoamides which stimulate beta cells, 90% Type 3 (gestational)  occurs in 2-4% of pregnancies, temporary yet increases risk Banting and Best – isolated hormone (insulin) Islet Cell Transplants

Adrenal Glands Made up of two glands Adrenal Medulla – controlled by the nervous system, epinephrine and norepinephrine are produced (fight or flight response) Increase blood sugar, heart rate Adrenal Cortex – controlled by hormones Glucocorticoids – associated with blood glucose levels and assist in dealing with stress (cortisol) Mineralcorticoids – associated with regulation of salt-water balance, aldosterone increases sodium retention and therein water reabsorption.

Hormones & Metabolism - 8.3 Thyroid Gland Thyroxine (T4) and triiodothyronine (T3) regulate body metabolism and the growth and differentiation of tissues. T4 Regulates metabolic rates Sugars get oxidized faster by people with a “faster” rate of metabolism

Thyroid Gland Control of the hormones is accomplished by negative feedback Metabolic rate decreases hypothalamus gets signal thyroid releasing hormone (TRH) is released pituitary gland releases thyroid stimulating hormone (TSH) blood transports TSH to thyroid and thyroxine is released blood sugar goes up due to thyroxine stimulating increased sugar utilization. The process gets shut off when thyroxine levels get high as it inhibits the release of TRH

Parathyroid Gland Responds to immediate surroundings to help maintain homeostasis…a little different then other endocrine glands which are regulated by hormones. Low Ca2+ levels in blood cause parathyroid hormone (PTH) to be released which corrects that issue (absorb more from intestines and kidneys and break down bones)

Pituitary Gland Adrenocorticotropic hormone Melanocyte-stimulating hormone

Anterior Pituitary Gland Produces growth hormone (somatotropin) Increases growth of bones and cartilage, if growth plates have fused, other bones will respond  acromegaly Increases muscle cell size and connective tissue by promoting protein synthesis and inhibiting protein breakdown. Relationship between aging and GH. As you get older production of growth hormone decreases. Growth hormone is responsible for stimulating ribosomes to follow genetic information for protein synthesis. Cellular repair and protein replacement is compromised…protein is often replaced by fat as we age.

Stress – 8.4 Connection between long-term stress from a noxious stimulus. A general adaptation syndrome results from exposure to prolonged stress Stress Hormones  (p.388, table 1). More energy required so hormones make more glucose available in blood Increase in blood pressure and an elevated metabolic rate Problems with Long-Term Stress (p.389, table 2) Steroids – what do you think? p. 391, table 3

Stress – 8.4

Reproductive Hormones – 8.5 Male Reproductive System Sex hormones – androsterone & testosterone produced in the interstitial cells (between seminiferous cells) of the testes. Androsterone (ADT) is a steroid hormone with weak androgenic activity. It is made in the liver from the metabolism of testosterone Testosterone stimulates spermatogenesis (spermatogonia divide and mature); influences development of male secondary characteristics at puberty Hypothalamus and pituitary gland control the production of sperm and male sex hormones

Male Reproductive System Negative feedback ensures adequate numbers of sperm cells and testosterone are maintained. Pituitary produces and stores gonadotropic hormones which regulate functions of testes: Follicle stimulating (FSH)  promotes production of sperm cells Luteinizing (LH)  promotes production of testosterone Gonadotropin-releasing (GnRH)  hypothalamus secretes GnRH to the pituitary to release FSH and LH Once high levels of testosterone are detected by the hypothalamus, negative feedback is activated in that GnRH stops being released.

Female Reproductive System Oogenesis & Ovulation Ovaries contain fibrous connective tissue and small groups of cells called follicles Follicles are made up of two types of cells Primary oocyte - contain 46 chromosomes, undergoes meiosis, ovum Granulosa cell – nutrient production for oocyte 400 000 total follicles in each ovary  approximately 400 will mature in a woman’s life birth defects and older follicles?

Menstrual Cycle Flow phase – shedding of endometrium (5 days) Follicular phase – development of follicles within ovary, estrogen secreted (day 6-13) Ovulatory phase – egg bursts from ovary, estrogen and progesterone released (endometrium development). Progesterone inhibits further ovulation and prevents contractions (day 14). Luteal phase – preparation of uterus for fertilized egg. No fertilization means estrogen and progesterone decrease  weak contractions which cause endometrium to pull away from uterus.

Hormonal Control of the Female Reproductive System Hypothalamus-pituitary complex regulates estrogen and progesterone via gonadotropins FSH and LH GnRH signals puberty and allows release of FSH and LH Negative feedback  as estrogen levels increase the pituitary gland picks this up and turns off FSH Positive feedback  as estrogen levels increase the pituitary gland picks this up and releases more LH