Lecture 5

• type of secreting cell
• route taken by the signal in reaching its target

cell produces signal, which travels through the blood, makes it to target cells, and those with receptor can respond

signals released to neighboring cells, only those with receptors can respond

specialized neurosecretory cells secrete neurohormones that travel to target cells via the bloodstream

the same cell that produces the signal also has a receptor for that signal

when tissues close to each other need to interact

tumor, produces signal for the tumor itself to keep growing

• Neuroendocrine- cell that secretes signal is a neuron
• In endocrine/paracrine- regular cell secretes the signal

chemicals that allow members of the same species to send signals to each other

• marking trails leading to food
• defining territories
• warning of predators
• attracting potential mates

• endocrine- secretes stuff inside the body, secrete hormones directly into surrounding fluid
• exocrine- secretes stuff outside the body, have ducts which secrete substances onto body surfaces or into cavities

• polypeptides
• amines
• steroid hormones

• Water — can easily travel through bloodstream but has harder time entering/exiting the membrane
• Lipid — no problem exiting the membrane of producing cel, but cannot easily travel through the blood by itself

• Leaves membrane
• Binds to carrier protein in the blood to travel through bloodstream
• Can easily cross membrane when it reaches target cell
• Receptor is more likely to be inside (intracellular) because it can cross the membrane
• Receptor usually tells the cell what to do because it is already inside

• actively secreted through a vesicle
• easily travels through bloodstream on its own
• stays outside membrane because it cannot pass through
• needs a receptor on the membrane
• Receptor activates signal transduction pathway to deliver signal to the nucleus

inhibits a response by reducing the initial stimulus, thus preventing excessive pathway activity

reinforces a stimulus to produce an even greater response

receives info from the nervous system and initiates response through the endocrine system

Attached to the hypothalamus

• Oxytocin- regulates milk secretion by the mammary glands
• Antidiuretic hormone- regulates physiology and behavior

kidney tubules

Neuroendocrine signaling because neuron releases information into the bloodstream

• neurosecretory cells of the hypothalamus send signals to anterior pituitary
• Which travels through bloodstream for some distance and target the anterior pituitary, which responds by making more hormones

a hormone can stimulate the release of a series of other hormones, the last of which activates a non endocrine target cell

Hypothalamus secretes a hormone, which causes anterior pituitary to produce another hormone, which causes thyroid gland to make another hormone and fix the problem

• Hypothyroidism: too little thyroid function, can produce symptoms such as weight gain, lethargy, cold intolerance
• Hyperthyroidism: excessive production of thyroid hormone, can lead to high temperate, sweating, weight loss, irritability, and high blood pressure

insufficient dietary iodine leads to an enlarged thyroid gland (goiter)

adjacent to the kidneys

• adrenal medulla (inner portion)
• adrenal cortex (outer portion)

• (catecholamines)
• epinephrine (adrenaline)
• norepinephrine (noradrenaline)

• in response to stress-activated impulses from the nervous system
• They mediate various fight or flight responses

• Secretes adrenaline
• which generates sugar, increasing blood pressure and increasing metabolic rate
• gets you ready to make response

• trigger release of glucose and fatty acids
• increase oxygen delivery to body cells
• direct blood towards heart, brain, and muscles
• direct blood away from skin, digestive system, and kidneys

involuntary nerve signals

a family of steroids called corticosteroids

glucocorticoids and mineralocorticoids

by a hormone cascade pathway via the hypothalamus and anterior pituitary

• influence glucose metabolism and the immune system
• example: cortisol

• affect salt and water balance
• example: aldosterone

water and solute balance

Hypothalamus releases hormone (ACTH), goes through blood, targets adrenal gland, which secretes mineralocorticoids and glucocorticoids that can respond to the stress

Hypothalamus signals adrenal medulla through nerve impulses, which then in turn secretes epinephrine and norepinephrine

• Negative feedback loop is broke
• blood glucose level doesn’t drop, it stays high

because blood glucose levels are very high and glucose makes the urine sweet

hormone cascade pathway.

tropic hormones

• regulates bioenergetics
• helps maintain normal blood pressure, heart rate, and muscle tone
• and regulates digestive and reproductive functions.

• If the level of thyroid hormone in the blood drops, the hypothalamus responds by initiating a hormone cascade pathway
• The hypothalamus secretes thyrotropin-releasing hormone (TRH), causing the anterior pituitary to secrete a tropic hormone known as either thyroid-stimulating hormone (TSH) or thyrotropin
• TSH stimulates release of thyroid hormone by the thyroid gland, an organ in the neck consisting of two lobes on the ventral surface of the trachea.
• As thyroid hormone accumulates, it increases metabolic rate, while also initiating negative feedback that prevents its overproduction.