Introduction Flashcards
Hormones act via receptors, where can they be located?
on the surface or within the cell
Lipid soluble hormones
- mechanism of action
- examples
- bind to receptors located within the cells
- bind to nuclear receptor –> mRNA synthesis –> ribosome –> hormone production
- process is slow
-progesterone, testosterone, aldosterone, estrogen, calcitriol
Water soluble hormones
- mechanism of action
- examples
- bind to receptors located on the cell membrane
- intracellular signaling cascade –> ATP –> cAMP –> cell response
- process is fast
-ACTH, calcitonin, epinephrine, glucagon, PTH, ADH
Control of hormone secretion is regulated by:
- Signals from nervous system
- Chemical changes in blood
- Other hormones
Hypothalamus and Pituitary
- hypothalamus secretes inhibitory and releasing hormones. They regulate the release of anterior pituitary hormones
- anterior pituitary produces 7 hormones
7 hormones that are secreted by the anterior pituitary
- Human growth hormone (hGH)
- Thyroid stimulating hormone
- Follicle stimulating hormone
- Luteinizing hormones
- Prolactin (PRL)
- Adrenocorticotropic hormone (ACTH)
- Melanocyte stimulating hormone (MSH)
- Human growth hormone (hGH) (4)
- promotes synthesis of insulin like growth factors - somatomedins
- secreted by liver, muscle, cartilage, bones cells
- regulated by: hypothalamic hormones (growth hormone releasing and inhibiting) and blood glucose levels (low blood glucose levels –> released)
- actions: stimulates protein synthesis and makes “fuel” (ATP) available for growth
- Thyroid stimulating hormone (3)
- stimulates the formation and secretion of thyroid hormones (T3, T4) by thyroid gland
- regulation of TSH (negative feedback)
- low T3/T4 –> hypothalamus –> thyrotropin releasing hormone (TRH) –> TRH stimulates release of TSH –> TSH stimulates thyroid production of T3/T4
- Follicle stimulating hormone (4)
- in females - starts follicle development
- in males - sperm production in testes
- regulated by gonadotropin releasing hormones (GnRH) from hypothalamus
- increases estrogen in females
- Luteinizing hormones (4)
- in females - stimulates formation of corpus luteum
- in males - release testosterone from tests
- regulated by gonadotropin releasing hormones (GnRH) from hypothalamus
- increases estrogen and progesterone in females
- Prolactin (PRL) (5)
- initiates and maintains milk production by mammary glands
- ejection of milk is regulated by oxytocin
- prolactin inhibiting hormone (PIH) suppresses prolactin release
- high levels of estrogens –> PRH –> prolactin release
- hypersecretion –> erectile dysfunction
- Adrenocorticotropic hormone (ACTH) (4)
- controls production and secretion of glucocorticoids from adrenal cortex
- corticotrophin releasing hormones (CRH) from hypothalamus stimulates secretion
- stress-related stimulate can also stimulate the release of it
- glucocorticoids inhibit CRH and ACTH release
- Melanocyte stimulating hormone (MSH) (2)
- small amount in blood stream
- excess amount —> skin darkening
Posterior pituitary
-release two hormones: oxytocin and antidiuretic hormone (ADH = vasopressin)
Oxytocin causes… (3)
- smooth muscle contraction of uterus during childbirth
- causes “letdown” of milk glands to ducts
- some sexual pleasure during sexual activity
Antidiuretic hormone (ADH = vasopressin) (3)
- causes kidneys to retain more water
- causes vasoconstriction –> increases BP
- dehydration, pain, stress –> increase ADH secretion
Thyroid gland (4)
- follicular cells produce hormones and store them in follicles - T3 and T4
- parafollicular cells (C-cells) produce calcitonin
- T3 and T4 - increase basal metabolic rate, protein synthesis and growth. They are controlled by TRH and TSH
- Calcitonin - inhibits osteoclasts - strengthens bones, decreased blood Ca2+
Parathyroid glands (4)
- release PTH –> increases blood Ca2+ in 3 ways:
1. increases number and activity of osteoclasts that break down bone
2. Slows loss of Ca2+ and Mg2+ in urine
3. Promotes production of calcitriol (vitamin D) –> increases rate of Ca2+, Mg2+ and HO4P-2 absorption –> increase blood Ca2+
Pancreas (3)
- exocrine and endocrine
- alpha cells –> glucagon
- beta cells –> insulin
Actions of insulin and glucagon
Low blood glucose stimulate glucagon release
Glucagon stimulates liver to release glucose –> increase blood glucose
High blood glucose levels stimulate insulin release
Insulin increases glucose transport into skeletal muscle and adipose cells –> decrease blood glucose
Insulin promotes amino acid uptake, protein synthesis and lipid storage
Adrenal glands
Adrenal cortex: 3 zones make steroids
Zona glomerulosa - Outer zone –> mineralocorticoids (aldosterone)
Zona fasciculata - Middle zone –> glucocorticoids (cortisol)
Zona reticularis - Inner zone –> androgens (testosterone)
Adrenal medulla: produces epinephrine (adrenalin) and norepinephrine
Mineralocorticoids (3)
- aldosterone
- stimulates sodium and water reabsorption from urine to blood
- stimulates excretion of potassium into urine
Renin-angiotensin-aldosterone pathway
- Decreased BP
- Release Renin from kidney
- Renin acts on Angiotensinogen to form Angiotensin I
- In lungs, angiotensin converting enzyme causes angiotensin I –> angiotensin II
- Angiotensin II stimulates aldosterone release
Glucocorticoid actions (6)
- increases rate of protein breakdown
- stimulates liver formation of glucose
- breaks down triglycerides in adipose
- anti-inflammatory effects
- depresses immune system
- regulated by negative feedback: CRH and ACTH
ex: cortisol
Androgens (2)
- at puberty: stimulate axillary and pubic hair growth, contribute to adolescent growth spurt
- in females –> contribute to libido, are converted to estrogens by other body tissues
Adrenal Medulla (3)
- part of sympathetic nervous system
- releases epinephrine and norepinephrine
- actions mimic sympathetic nerves in stress –> increases HR and BP, increases blood glucose, dilates airways
Pineal gland (4)
- small gland attached to roof of third ventricle of brain
- produces melatonin
- sets body’s biological clock
- more released in darkness, less in sunlight
Stages of stress response
When successful leads to extra physiological capacity and long-term adaptation
- Initial “fight-or-flight” response - aldosterone (raise blood pressure)
- Resistance (slower)
- Exhaustion (may occur eventually)
Aging (7)
- Loss of negative feedback sensitivity so decline in circulating thyroid hormones
- PTH levels rise –> loss of bone mass
- Less glucocorticoid production
- Slower release of insulin
- Thymus declines after puberty
- Ovarian response to gonadotropin stops
- Slow decline in testosterone production
