1 - Enodcrine System Flashcards
What are the 4 types of chemical messengers
1) Autocrine
2) Paracrine
3) Neurotransmitter
4) Endocrine
What do Autocrines do?
effect the same cell, e.g. prostaglandin
What does prostaglandin do?
They control processes such as inflammation, blood flow, the formation of blood clots and the induction of labour.
What do pancreatic messengers do?
effect local cells. e.g. somatin
What do hormones do?
Produced by endocrine system + travel to circulatory system
Define hormones
secreted via endocrine glands, travelling via the blood to target tissues.
Characteristics of hormones
1) stability: half life, water soluble (protein, epinephrine and norepinephrine)
2) Communication (with target cells)
3) Distribution (dissolve in blood plasma unbound. Unbound = distribute greatly OR Bound = distribute less (more concentrated, attaching to lipids)
3 Patterns of hormone secreition
1) Chronic: stable concerntration
2) Acute: rapid increase due to stimulus
3) Episodic: increases and decreases at a constant rate
Stimulatory Influences on hormone secretion + examples
1) Humoral
2) Neural
3) Hormonal
Describe Humoral influences
Humoral: action of a substance which isn’t a hormone or endocrine gland.
Eg. Parathyroid Hormone. Calcium levels too low> PTH release > osteoclasts > bone breakdown > increase in calcium levels.
Describe Neural Influences
Control of endocrine gland
Hormonal
Control of the secretory activity of 1 endocrine gland by a hormone / OR neurohormone secreted by another endocrine gland.
What are the major mechanisms of maintenance of blood hormone levels
FEEDBACK LOOPS
- Posivite feedback
- Negative Feedback
How do Positive feedback loops maintain blood hormone levels?
Positive Feedback Loops:
(release of an additional hormone in response to a original hormone release)
This form of feedback is exhibited during childbirth. Whereby oxytocin is secreted by the pituitary gland, stimulating the uritine muscles to contract, encouraging the fetus to move towards the cervix.
How do negative feedback loops maintain blood hormone levels?
Negative Feedback Loops: (inhibiting further hormone release due to adequate amounts of hormone)
E.g. release of glucocorticoid hormone released via the adrenal glands (stimulated via the pituitary gland and hypothalamus). As glucocorticoid levels increase in the blood, pituitary and hypothalamus reduce signaling to adrenal gland preventing overproduction of glucocorticoid)
What are 10 regulatory functions of endocrine system?
- Metabolism
- Food intake + digestion’tissue maturation
- Ion regulation
- Control of blood glucose
- Reproductive function control
- Uterine contractions
- Milk release
- Immune system regulation
What are the functions of the Posterior Pituitary gland
Posterior Pituitary
1. ADH – increased water absorption (Target – kidneys) 2. Oxytocin – increased uritine concentrations (target – uterus)
What are the functions of the Anterior Pituitary Gland?
Anterior Pituitary Glands:
1. Growth Hormone – increased growth = increased amino acid uptale, breakdown of lipids, increased glycogen synthesis, blood glucose levels)
2. Thyroid Stimulating Hormone: increased thyroid hormonal secretion (target – thyroid gland) 3. Adrenocorticotropic (ACTH): increased ACTH secretion (Target – adrenal cortex) 4. Lipotropins: Increased lipid breakdown (target – adipose tissue) 5. Prolactin: Milk production in lactating women (Target Tissue: ovaries and mammary glands)
What are the functions of the Hypothalamus?
Regulates secretions of anterior pituitary gland. Secretes and inhibits hormones directed to the anterior pituitary gland. And action potentials.
Describe the hormones released from the Pituitary gland glands and summarise their functions in the body
Post Pituitary
- ADH (water retention)
- Oxytocin (contractions + milk ejection)
Anterior:
- Growth Hormone (growth, metabolism, protein uptake)
- Thyrotropin (thyroid hormones)
- ACTH (cortisol secretion)
- FH + FSH (production of gametes + reproductive hormones)
- Prolactin (stimulates milk production)
Hormones released by Thyroid Gland
Thyroid Galnd:
- T3
- T4
What does T3 and T4 do?
Functions:
- initiate protein synthesis
- increase rate of glucose, fat and protein metabolism
- increase body temp, and normal growth of tissues.
- Both T3 and T4: synthesis in thyroid follicles, are transported in the blood, bind with nuclear receptor molecules, secretion levels are regulated via TRH (via hypothalamus) TSH (via anterior pituitary gland) > all inhibiting secretion.
What are the hormones released by the Parathyroid Gland
PTH (parathyroid hormone)
What are the functions of PTH?
- Increase blood calcium and PO4- levels
- Stimulate osteoclasts
- Promote calcium reabsorption
- Synthesis of vitamin D (increasing absorption of Ca and PO4)
What hormones are released by the Adrenal Medlulla?
Epinephrine + Norepinephrine
What are the functions of epinephrine?
Epinephrine: increasing BGL’s, increasing fat breakdown in adipose tissue, dilation of blood vessels in skeletal and cardiac muscles/
What conditions result from hyposecretion?
Hyposecretion:
> Mineralocorticoids (aldosterone). Cause: removal of gland or loss of fucntion. Sym: hypoatremia (low blood levels of Na), Hypokalemia (high blood level of K+), low blood pressure, tremors. > Glucocorticoids (Cortisol). Cause: removal of glad or loss of function. Sym: low blood glucose levels (hypoglycemia), depressed immune system, ;loss of appetite, bronzed skin, in women decreased pubic and axillary hair.
What conditions result from hypersecretion
> Mineralocorticoids (aldesterone), Causes: tumor in gland or aldosteronism. Sym: slight hypernatremia (high levels of Na), Hypokalemia (low blood levels of K), high blood pressure, weakness o skeletal muscles acidic urine)
> Glucocorticoids (cortisol). Causes: tumor in gland or cushing syndrom (high cortisol and androgens) . Symphyperlycemia (high blood glycose levels), depressed immune system, depression. > Androgens: Causes: tumor in gland or adrenogenital syndrome. Sym: Excessive facial and body hair, acne, increased sex drive, regression of breast tissue, loss of regular menses.
What are the effects of aging on the endocrine system?
Aging results in a gradual decreases in secretion rates for most, but not all hormones. Some of these decreases are related to a gradual decrease in physical activity.
Hormones decreasing:
GH, melatonin, thyroid hormones (T3 and T4 slowly decreasing), reproductive hormone, thymosin. Fewer mimmature lymphocytes mature and are functional, the immune system is less active; resulting in a increased susceptability to infection and cancer.
What hormone remains despite ones age?
Parathyroid hormone” regulates blood glucose levels
