Ch35: Chemical Signaling w/i Animals w/ Hormones A hormone is a chemical signal produced to send messages around the body it typically acts a distant.

Ch35: Chemical Signaling w/i Animals w/ Hormones

• A hormone is a chemical signal produced to send messages around the body it typically acts a distant site, carried by blood

• hormones are produced in called the endocrine glands

Figure 35.1 Majors glands of the human endocrine system

35.1 Hormones

• The glands that produce hormones are generally controlled by the nervous system

• the two are so closely linked that they are often considered a single system—neuroendocrine system

the hypothalamus (part of the brain) is the main switchboard of the neuroendocrine system for controlling the body.

35.1 Hormones

• The CNS regulates the body’s hormones through a chain of command for example, the hypothalamus controls the

pituitary gland with a hormone (thyrotropic-releasing hormone/TRH)

• this causes the pituitary to release a hormone which controls an endocrine gland. (thyroid-stimulating hormone/TSH)

the hypothalamus also secretes inhibiting hormones that keep the pituitary from secreting specific hormones

35.1 Hormones

• Hormones are effective messengers because they travel in the blood to a specific target cell

cells that respond to a particular hormone have receptor proteins shaped to fit that hormone and no others

35.1 Hormones

• Hormones secreted by endocrine glands belong to four different chemical categories polypeptides glycoproteins amines steroids

35.1 Hormones• Homones signal their communication by a series of

simple steps

1. issue the command • the hypothalamus controls the release of many hormones

2. transport the signal• most hormones are transported by the bloodstream

3. hit the target cell(s)• the hormone binds to a receptor

4. have an effect• the hormone bound receptor triggers a change in cell activity

How hormonal communication works

1. The young teenager sees an attractive teen, so the hypothalamus secretes a releasing hormone GnRH

2. GnRH stimulates the anterior pituitary to release its hormones FSH & LH

3. FSH & LH stimulates the gonads to secrete testosterone in boys and estrogen in girls

4. Testosterone or estrogen bind to cell receptors, changing the cell, in brain cells it results in a crazy teen behavior!

35.2 How Hormones Target Cells

• Steroid hormones bind to protein receptors located in the cytoplasm or nucleus of the target cell

Testosterone, estrogen, and progesterone are steroid hormones

steroids are lipid-soluble so they can pass across cell or nuclear membrane

35.2 How Hormones Target Cells

• The steroid hormone-receptor complex move in the nucleus and bind to DNA

this activates transcription of a gene subsequently making a protein and changing the behavior of a cell

Figure 35.3 How steroid hormones work

35.2 How Hormones Target Cells

• peptide hormones binds to receptors within the plasma membrane the hormone binding to the receptor triggers

changes in the receptor protein causes changes in the cell

• second messengers usually amplifying this change by activating enzymes

• cyclic AMP (cAMP) & Ca+2 are second messengers

Figure 35.4 How peptide hormones work

Figure 35.5 How second messengers work

Marie, I showed this slide but did not go over it. John

35.3 The Hypothalamus and the Pituitary

• The pituitary gland is located beneath the hypothalamus and is the location where nine hormones are produced the pituitary is actually two glands

• posterior lobe regulates water conservation and, in women, milk letdown and uterine contraction

• anterior lobe regulates other endocrine glands

35.3 The Hypothalamus and the Pituitary

• The posterior pituitary is under the control of the hypothalamus and they are connected by a tract of neurons Two hormones are produced by the

hypothalamus and transported/stored in the posterior pituitary

• vasopressin or antidiuretic hormone (ADH) regulates the kidney’s conservation of water

• oxytocin initiates uterine contractions during childbirth and milk release in mothers

Figure 35.6 The posterior pituitary contains hormones that originate in the hypothalamus

35.3 The Hypothalamus and the Pituitary

• The Hypothalamus controls the anterior pituitary by secreting “releasing hormones” that cause the anterior pituitary to release its hormones

• The anterior pituitary is a complete gland that produces and secretes seven hormones

1. thyroid-stimulating hormone (TSH) stimulates the thyroid gland to produce thyroxine

2. adrenocorticotropic hormone (ACTH) stimulates the adrenal gland to produce hormones

35.3 The Hypothalamus and the Pituitary

3. growth hormone (GH) simulates the growth of muscle and bone throughout the body

4. Follicle-stimulating hormone (FSH) 1. in females, triggers the maturation of egg cells and

stimulates the release of estrogen2. in males, it regulates sperm development

5. Luteinizing hormone (LH) in females, it triggers ovulation of an egg in males, it stimulates the gonads to produce

testosterone

35.3 The Hypothalamus and the Pituitary

6. Prolactin (PRL) hormone stimulates the breasts to produce milk

7. Melanocyte-stimulating hormone (MSH)

its function in humans is poorly understood in reptiles and amphibians it stimulates skin

color changes

Figure 35.7 The role of the pituitary

35.3 The Hypothalamus and the Pituitary

• The hypothalamus controls the production and secretion of the anterior pituitary hormones by secreting both: releasing hormones (stimulate the production

& release of an anterior pituitary hormone) and inhibiting hormones (inhibit production &

release an anterior pituitary hormone)

35.3 The Hypothalamus and the Pituitary

• Negative feedback (feedback inhibition) also controls how many hormones in the anterior pituitary are produced

when enough of the target hormone has been produced, the hormone itself feeds back to the hypothalamus and inhibits the release of the releasing hormones from the hypothalamus and also directly inhibits the anterior pituitary

Figure 35.9 Negative feedback

35.4 The Pancreas

• The pancreas has both exocrine and endocrine functions, secreting digestive enzymes and hormones

• the hormones, produced in the islets of Langerhans, are insulin and glucagon

– insulin promotes the uptake of blood glucose (glycogen in the liver and triglycerides in fat cells)

– glucagon causes liver cells to release stored glucose and fat cells to break down triglycerides

Figure 35.10 Insulin and glucagon secreted by the pancreas regulate blood glucose levels

35.4 The Pancreas

• Diabetes mellitus is a serious disorder in which affected individuals’ are unable to take up glucose from the blood there are two kind of diabetes mellitus

• Type I is a hereditary autoimmune disease that attacks the islets of Langerhans, resulting in abnormally low insulin secretion (treat w/ shots)

• Type II is an abnormally low number of insulin receptors in the target tissue (treat w/ diet)

35.5 The Thyroid, Parathyroid, and Adrenal Glands

• The thyroid gland makes several hormones

calcitonin stimulates the bones to absorb calcium from the blood

thyroxine increases the bodies metabolic rate and promotes growth

• thyroxine contains iodine and if a diet is low in iodine, the thyroid cannot make enough thyroxine to inhibit the hypothalamus

– as a result, the hypothalamus stimulates the thyroid to grow producing a goiter

Figure 35.11 The thyroid gland secretes thyroxine

35.5 The Thyroid, Parathyroid, and Adrenal Glands

• The parathyroid glands are four small glands attached to the thyroid

these glands produce parathyroid hormone (PTH), a hormone that is essential for survival because it releases calcium out of the bones (calcitonin causes bones to absorb calcium)

this regulates calcium blood levels, which is necessary for muscle & heart contractions

Figure 35.12 Maintenance of proper calcium levels in the blood

35.5 The Thyroid, Parathyroid, and Adrenal Glands

• The adrenal glands are just above the kidneys and has two parts

medulla is the inner core and produces epinephrine and norepinephrine

cortex is the outer region and produces the steroid hormones cortisol and aldosterone

35.5 The Thyroid, Parathyroid, and Adrenal Glands

• The medulla releases epinephrine (adrenaline) and norepinephrine in times of stress act as emergency signals stimulating rapid

deployment of body fuel

• The cortex secretes cortisol, which acts to maintain nutritional well-being

• The cortex secretes also secretes aldosterone which is essential for survival it affects water and sodium reabsorption in the

kidneys