Animal Hormones Flashcards
Vertebrate Endocrine Glands + Hormones
- animal hormones are often produced in specialized hormone-synthesizing glands
- hormones are the secreted from the glands into the blood stream, where they are transported throughout the body
Hypothalamus
- located in the brain
- integrates the endocrine + nervous systems
- receives input from the body and other brain areas and initiates endocrine responses to environmental changes
- synthesizes hormones stored in the pituitary gland
- Synthesizes + secretes regulatory hormones that control the endocrine cells in the anterior pituitary glands
Pituitary Gland
the body’s “master gland”, located at the base of the brain + attached to and regulated by the hypothalamus
- Anterior + Posterior Portion
Pituitary Gland: Anterior Portion
regulated by releasing or release-inhibiting hormones produced by the hypothalamus
Pituitary Gland: Posterior Portion
receives signals via neurosecretory cells to release hormones produced by the hypothalamus
Thyroid Gland
butterfly-shaped gland located in the neck; regulated by the hypothalamus-pituitary axis
- produces hormones involved in regulating metabolism + growth - thyroxine (T4) and triiodothyronine (T3)
T4 + T3
- increases the basal metabolic rate
- affect protein synthesis + other metabolic processes
- help regulate long bone growth (synergy with growth hormone)
- USED IN METAMORPHOSIS
Adrenal Glands
two glands, each located on one kidney; each producing different sets of hormones
- Adrenal Cortex (outer layer)
- Adrenal Medulla (inner layer)
Adrenal Cortex
produces mineralocorticoids (aldosterone) + glucocorticoids (cortisol)
Mineralocorticoids
increases reabsorption of sodium by kidneys to regulate water balance
Glucocorticoids
long-term stress response hormone
- Increases blood glucose levels by stimulating the synthesis of glucose and gluconeogenesis by liver cells
- promote release of fatty acids from adipose tissue
Adrenal Medulla
produces epinephrine (adrenaline), a short-term stress response hormone - “fight-or-flight”
- increases heart rate, breathing rate, cardiac muscle contractions, blood pressure, and blood glucose levels
- accelerates the breakdown of glucose in skeletal muscles + stored fats in adipose tissue
- the release of epinephrine is stimulated directly by neural impulses from the SYMPATHETIC NERVOUS SYSTEM
Pancreas
located between the stomach + proximal portion of the small intestine; regulates blood glucose levels via 2 opposing hormones
- Insulin
- Glucagon
Insulin
- produced by pancreas beta cells when blood glucose levels rise ABOVE normal levels (ex: after eating a meal)
- decreases blood glucose levels by promoting uptake of glucose by liver to convert to glycogen (sugar storage molecule)
-enhances the rate of glucose uptake + utilization by target cells which use glucose for ATP production - stimulates the conversion of glucose to fat in adipocytes + the synthesis of proteins
Glucagon
- hormone released from pancreas alpha cells when blood glucose levels fall BELOW normal levels (EX: between meals or during exercise)
- Increases blood glucose levels by promoting the breakdown of glycogen and release of glucose from the livers and muscles
- stimulates absorption of amino acids from the blood by the liver, which converts them to glucose
- stimulates adipose cells to release fatty acids into the blood
Gonads
AKA ovaries + testes; produce sex steroid hormones that promote the development of secondary sex characteristics and regulation of gonad function
Hormonal Regulation
Hormones have a wide range of effects and modulate many different body processes:
1. Blood Glucose
2. Metamorphosis
3. Stress
Glucose
primary energy source for most animal cells, distributed throughout the body via the blood stream
- after a meal, carbohydrates are broken down during digestion + absorbed into the blood stream
- the amount present is typically more than the body needs - extra glucose is removed + stored for later (the opposite occurs during fasting)
- BLOOD GLUCOSE LEVELS ARE REGULATED BY 2 HORMONES PRODUCED BY THE PANCREAS: INSULIN + GLUCAGON
- Insulin + glucagon work together to maintain homeostatic glucose levels
Insulin Feedback Loop
- causes blood glucose concentrations to fall (HYPOGLEMIC)
- “low sugar” effect that inhibits further release of insulin from beta cells
- NEGATIVE FEEDBACK LOOP
Glucagon Feedback Loop
- causes a HYPERGLYCEMIC EFFECT
- glucose is used as energy by muscle cells + released into circulation by liver cells, causing an increase in blood glucose levels to normal levels
- NEGATIVE FEEDBACK LOOP
Diabetes Mellitus
Impaired insulin function is caused by low levels of insulin production by pancreas beta cells or by reduced sensitivity of tissue cells to insulin
- prevents glucose from being absorbed by cells, causing hyperglycemia
- can cause nerve damage to the eyes + peripheral body tissues, and kidney + cardiovascular damage
Hypoglycemia
caused by over secretion of insulin; low blood glucose levels cause insufficient glucose availability to cells, often leading to muscle weakness, unconsciousness, or death
Metamorphosis
- T3
- Juvenile Hormone
- Prothoracicotropic Hormone
- Ecdysone Hormone
Metamorphosis: T3
surges initiate the development of new structures, reorganize internal organ systems, and control other metamorphosis processes
