6.6.2 hormones & homeostasis

Question 1

what is a hormone

Answer 1

Signaling molecules
Secreted by glands of the exocrine system
Into the bloodstream
Target distant organs
Regulate physiological processes

Question 2

3 types of hormones

Answer 2

1. Steroids (estrogen, progesterone, and testosterone)
2. Peptides (insulin, glucagon, leptin, follicle stimulating hormone (FSH), leutinizing hormone (LH), growth hormone (GH).
3. Amines (epinepherine, melatonin, thyroxine)

Question 3

homeostasis

Answer 3

Homeostasis is the tendency for an organism or cell to maintain a constant internal environment within tolerance limits
Feedback loops, that operate between the nervous or endocrine system and target organs/tissues, returns systems to equilibrium. If equilibrium cannot be met, the disease may occur.

Question 4

feedback loops

Answer 4

Negative feedback involves a response that is the reverse of the change detected (reduces)
Positive feedback involves a response that reinforces the change detected (amplifies)

Question 5

draw diagram of feedback loop of FSH+LH, estrogen+progesterone

Answer 5

slide 8

Question 6

insulin & glucagon

Answer 6

Secreted by: Pancreatic cells (beta - insulin, alpha - glucagon)

Function:
Insulin:
- Promotes glycogenesis - glucose uptake by muscles/liver and anabolic conversion to glycogen
- Blood glucose decreases
Glucagon:
- Promotes glycogenolysis - catabolic conversion of glycogen to glucose in liver & muscles
- Blood glucose increases

Question 7

thyroxine

Answer 7

Secreted by: Thyroid Gland
Target: Hypothalamus in brain
Function: Body temperature/Metabolic rate

Question 8

thyroxine: negative feedback loop

Answer 8

When thyroid hormone levels (including thyroxine) drop below a certain threshold, it triggers the release of thyroid-stimulating hormone (TSH) from the pituitary gland.

TSH stimulates the thyroid gland to produce and release more thyroxine into the bloodstream.

As thyroxine levels increase, it inhibits the release of TSH from the pituitary gland, thus reducing the stimulation of the thyroid gland.

When thyroxine levels reach a certain level, this negative feedback loop slows down the production of both TSH and thyroxine, maintaining a balance in the thyroid hormone levels in the body.

Question 9

leptin

Answer 9

Leptin is a hormone your body fat releases that helps you maintain your normal weight on a long-term basis
Secreted by: Leptin is secreted by white adipose tissue and these levels have a relationship to your body fat.
Target: The central nervous system (CNS), particularly the hypothalamus, is believed to be the main leptin target and mediates hunger
Function: Leptin’s function in the body pertains to regulating the balance between food intake and energy expenditure

Question 10

leptin: feedback loop

Answer 10

Leptin is proposed to act as an afferent signal in the negative feedback loop to hypothalamus that limiting food-intake, (The hypothalamus is an area of the brain that produces hormones that control: Body temperature. Heart rate. Hunger. Mood.) controlling energy homeostasis and regulating the mass of adipose tissue. The deficiency of or resistance to leptin causes severe obesity.

Question 11

leptin & obesity

Answer 11

Since the amount of leptin in your blood is directly proportional to the amount of (body fat), having obesity results in high levels of leptin (hyperleptinemia). This can cause a lack of sensitivity to leptin, a condition known as leptin resistance
The peptide hormone leptin regulates food intake, body mass, and reproductive function and plays a role in fetal growth, proinflammatory immune responses, angiogenesis and lipolysis. Leptin is a product of the obese (ob) gene and, following synthesis and secretion from fat cells in white adipose tissue, binds to and activates its cognate receptor, the leptin receptor (LEP-R).

Question 12

melatonin

Answer 12

hormone that your brain produces in response to darkness. It helps with the timing of your circadian rhythms (24-hour internal clock) and with sleep.

Secreted by: pineal gland (in brain)

pineal gland releases the melatonin to the bloodstream, from which it circulates throughout the body. The hormone interacts with as melatonin receptors which are found not only in the brain but also in peripheral tissues. Melatonin levels typically begin to rise in the evening, peak during the night, and decrease in the early morning hours.