Endocrine System Flashcards
Five ways the endocrine system maintains homeostasis
Alters metabolism, regulates growth and development, regulates reproduction, regulates circadian rhythm and regulates activity of muscles and glands
Where are the receptors for lipid soluble hormones located?
Within the target cell
Where are the receptors for water-soluble hormones located?
On the cell membrane
Why can water soluble hormones not be given orally?
They will be destroyed by digestion
What is the difference between autocrine and paracrine hormones?
Autocrine hormones activate the cells that produced them, paracrine activate neighboring cells.
What is the difference between endocrine and exocrine glands?
Endocrine glands secrete hormones into interstitial fluid which diffuse into the blood. Exocrine secrete into ducts which carry them to the target site.
What gland is both endocrine and exocrine?
Pancreas
How are hormones inactivated and excreted from the body?
Some are degraded by enzymes in target cells but most are inactivated by the liver, and excreted by the kidneys and in faeces
What three stimuli trigger hormone secretion?
Signals from the nervous system, chemical levels in the blood or other hormones.
Structure and location of the pituitary gland
Small pea shaped gland that sits below the hypothalamus
What 2 hormones are released from the posterior pituitary, and where are they produced?
Antidiuretic hormone (ADH) and oxytocin. Produced in the hypothalamus
What six hormones are produced by the anterior pituitary gland?
Growth hormone thyroid stimulating hormone adrenocorticotropic hormone (ACTH) follicle stimulating hormone luteinizing hormone prolactin
Stimulus, target and function of ADH
Osmoreceptors in the hypothalamus detects increase of solutes in the blood, impulses sent to pituitary to release ADH which tells the kidneys to increase blood volume and decrease urine output.
What stimulates oxytocin release and what does it do?
When a baby breast feeds signals are sent to the hypothalamus which sends action potentials to the axon terminals in posterior pituitary to release oxytocin which travels to the breast and stimulates release of milk.
What stimulates growth hormone and what does it do
Releasing hormone from hypothalamus stimulates anterior pituitary to release GH. Targets all body cells to enlarge and divide but main targets are bone and skeletal muscle.
What stimulates thyroid stimulating hormone and what does it do
Low blood levels of thyroxine or low metabolic rate (cold) causes hormone cascade. Hypothalamus releases a hormone that travels to anterior pituitary which releases TSH which then tells thyroid to release thyroxine (T3, T4). Thyroxine increases the basal metabolic rate thus producing heat
What stimulates adrenocorticotropic hormone and what does it do
Stress causes hypothalamus to release corticotropin releasing hormone which tells anterior pituitary to release ACTH which travels to adrenal gland and tells it to release cortisol.
What does follicle stimulating hormone do
From anterior pituitary. Initiates development of eggs and stimulates production of oestrogen in females. Stimulates production of sperm in males
What does luteinizing hormone do
Stimulates production of oestrogen and progesterone in the ovaries. Stimulates production of testosterone in the testes
What does prolactin do
Initiates and maintains milk production, levels rise dramatically towards end of pregnancy
What are 2 clinical conditions related to thyroxine
Hypothyroidism and hyperthyroidism
What mineral is essential in the production of thyroxine
Iodine
Location of adrenal glands
On top of the kidneys
What two areas are within the adrenal glands and what hormones do they produce
Adrenal cortex - Cortisol and aldosterone
Adrenal medulla - adrenaline and noradrenaline
What are four functions of cortisol
Increases BGL by gluconeogenesis
helps maintain sympathetic response
Raises level of fatty acids and amino acids in the blood
Has an anti-inflammatory effect that suppresses immune system
What stimulates secretion of adrenaline and noradrenaline
Stressful situations, exercise, fight or flight response
What are six functions of adrenaline
Increases HR Increases cardiac output Increase BP Increase blood flow Dilate airways Increase BGL
What is the main function of noradrenaline
Vasoconstriction to increase BP
When would glucocorticoids (cortisol) medications be prescribed?
To suppress anti-inflammatory response in organ transplant patients
What two hormones control blood calcium levels and where are they released from
Calcitonin from thyroid and parathyroid hormone (PTH) from parathyroid gland
What is the gland and hormone responsible for circadian rhythm?
Pineal gland produces melatonin
What are three functions of calcium in the body
Transmission of nerve impulses
muscle contraction
blood clotting
What are the three main functions of PTH
Stimulates osteoclasts to breakdown bone and raise blood calcium
Enhances reabsorption of calcium by the kidneys
Activates vit D to become calcitriol which is needed to absorb calcium from food
What causes release of calcitonin and what does it do
Calcitonin is released when blood calcium levels are too high. It inhibits osteoclast activity resulting in calcium being deposited in bone and less in blood
What is calcitriol also known as
Active vitamin D
What are the two functions of calcitriol
Increases absorption of calcium and phosphate from intestine
Enhances actions of PTH to resorb bone
What two hormones specifically regulate BGL and what cells secrete them?
Glucagon from alpha cells and Insulin from beta cells
Stimulus and function of Glucagon
Chemical stimulus, when BGL are too low glucagon is secreted which stimulates your liver to turn glycogen back into glucose via glycogenolysis
Stimulus and function of Insulin
Chemical stimulus when BGL is too high, insulin is released which joins glucose molecules together into glycogen to be stored via glycogenesis
What four other hormones can also raise BGL
Cortisol, adrenaline, growth hormone, thyroid hormone
Three stages of the stress response
- Initial fight or flight response
- Slower resistance reaction
- Exhaustion
What is the main hormone responsible for stage 1
Adrenaline
Three hormones responsible for stage 2
Cortisol, growth hormone, thyroxine
What are the long term effects of prolonged cortisol
Wasting of muscle
Immune system suppression
Ulceration of GI tract
Failure of insulin producing beta cells
What two risks are associated with long term stress
Chronic disease
Premature death
Four age related changes to the endocrine system
Growth hormone decreases causing muscle atrophy
Thyroid gland decreases production resulting in decrease in BMR
PTH rises resulting in osteoporosis and fractures
Adrenal cortex produces less aldosterone and cortisol
