Endocrine System (week 6) Flashcards
what is the endocrine system?
second controlling system of the body,
uses chemical messengers (hormones) that are released into the blood
what do several major processes do hormones control?
- reproduction
- growth and development
- mobilisation of body defences
- maintenance of homeostasis
- regulation of metabolism
how are hormones produced?
specialised cells
what do cells secrete to target sites?
hormones
what are the chemistry classifications of hormones?
- amino acid-base (proteins, peptides, amines)
- steroids
- prostaglandins
Hormones affect only certain ____ or ____?
tissues or organs (target cells or organs)
-> target cells have specific protein receptors
what are the different types of stimuli that activate endocrine glands?
- hormonal
- hum oral
- neural
what is hormonal stimuli?
where endocrine organs are activated by other hormones
* hormonal indicate various body fluids such as blood and bile
what is neural stimuli
nerve fibres stimulate hormone release
most are under the control of the sympathetic nervous system
what are the major endocrine organs?
- hypothalamus
- pituitary gland
- pineal gland
- thyroid gland
- parathyroid gland
- thymus
- adrenal glands
- pancreas
- gonads (testes and ovaries)
what are the functions of endocrine glands?
(ductless glands)
-> they create hormones that are released directly into blood or lymph
what is the pituitary gland?
-pea-sized gland that hangs by a stalk from the hypothalamus int he brain
(protected by the sella tunica of the sphenoid bone
what is the function of the hypothalamus?
produces releasing hormones and inhibiting hormones
- > these hormones are released into portal circulation, which connects hypothalamus to anterior pituitary hormones - > these hormones control the release of anterior pituitary hormones
what is the role of the posterior gland?
it doesn’t make the hormones, it releases it
- stores hormones made by the hypothalamus
what are the 2 main hormones made by the hypothalamus?
oxytocin and antidinretic hormone (ADH)
what is oxytocin?
- stimulates contractions of the uterus during labour , sexual relations and breast feeding
- causes milk ejection (let-down reflex) in a nursing woman
- only released in significant amounts during child birth and nursing
what is antidinretic hormone (ADH)?
- inhibits urine production (dieresis) by promoting water reabsorption by the kidneys
- urine volume decreases, blood volume and pressure increases
- in large amounts, ADH causes constriction of arterioles, leading to increased blood pressure (the reason why ADH is known as vasopressin)
- alcohol inhibits ADH secretion
what are the 2 anterior pituitary hormone?
- growth hormone
2. prolactin
what are the 4 types of anterior pituitary hormone?
- follicle-stimulating hormone
- Luteinizing hormone
- thyrotropic hormone
- adrenocorticotropic hormone
what is growth hormone and its functions?
- general metabolic hormone
- major effects are directed to growth of skeleton muscles and long bones
- plays a role in determining final body size
- causes fats to be broken down for a source of energy
what is prolactin (PRL) and it’s functions?
- stimulates and maintains milk production following childbirth
- functions in males is unknown
what are gonadotropic hormones functions?
regulate hormonal activity of the gonads
what are the 2 gonadotropic hormones?
- follicle-stimulating hormone (FSH)
- luteinzing hormone (LH)
what is follicle-stimulating hormone (FSH)?
- stimulates follicle development in ovaries
- stimulates sperm development in testes
what is lutenizing hormone (LH)?
triggers ovulation of an egg in females
stimulates testosterone production in males
What is thyrotopic hormone (TH)?
(also called thyroid-stimulating hormone)
influences growth and activity of the thyroid gland
what is Adrencorticotropic hormone (ACTH)?
regulates endocrine activity of the adrenal cortex
where is the pineal gland?
hangs from the roof of the third ventricle of the brain
what is the function of the pineal gland?
secretes melatonin
-> believed to trigger the body’s sleep cycle/wake cycle
where is the thyroid gland?
found at the base of the throat, inferior to the adam’s apple
what is the function of the thyroid gland?
produces 2 hormones, thyroid hormone and calcitonin
what is the function of the thyroid hormone?
controls rate of oxidation of glucose to supply body heat and chemical energy (ATP)
-> needed for growth and development
what 2 active iodine containing hormones does thyroid hormone contain?
thyroxine (T4) and triiodothyronine (T3)
what is T4 and T3?
secreted by thyroid follicles (T4)
formed from the conversation of T4 at target tissues (T3)
what is the role of calcitonin?
decreases blood calcium levels by causing calcium deposition on bone
how is calcitonin produced?
by parafollicular cells found between the follicles
- released in response to rising blood calcium levels
0 antagonistic to parathyroid hormone
what is the parathyroid gland?
tiny masses on the posterior of the thyroid gland
what is the function of the parathyroid gland?
secrete parathyroid hormone (PTH)
where is the thymus located?
in the upper thorax, posterior to the sternum
what is the role of the thymus?
produces a hormone called thymosin
what are the 2 regions of the adrenal gland?
adrenal cortex and adrenal medulla
describe the adrenal cortex
outer glandular region has 3 layers that produce corticosteroids
what are the corticosteroids secreted in the adrenal cortex
mineral corticosteroids, glucocorticoids and sex hormones
what are the hormones of the adrenal cortex?
mineralcorticoids and aldosterone
what is the role of mineral corticoids?
- regulate mineral (salt) content in blood, particularly sodium and potassium ions
- regulate water and electrolyte balance
how is production of alderosterone inhibited?
by atrial natriuretic peptide (ANP)
what is glucocorticoids?
- promote normal cell metabolism
- help resist long-term stressor by increasing blood glucose levels
- release in response to increased blood levels of ACTH
describe Sex hormones
produced in the inner layer of the adrenal cortex
- most of the hormones produced are androgens (make sex hormones) but some estrogens
which 2 hormones are processes in the adrenal gland?
- epinephrine (adrenaline)
2. norepinephrine (noradrenaline)
what does epinephrine and norepinephrine do?
prepare the body to deal with short-term stress (fight or flight)
-> results in more oxygen and glucose int he blood and faster circulation to the organs
what is the role of pancreatic islets?
produce hormones (insulin and glugacon)
what is the function of insulin?
increases the rate of glucose uptake and metabolism by body cells
-> effects hypoglycaemic
what is the role of glucagon?
released when blood glucose levels are low
- stimulates the live to release glucose to blood, thus increasing blood glucose levels
- ? effects are hyperglycaemic
what is the function of gonads?
produce sex cells or sex hormones ovaries: - estrogen -progesterone testes
what does estrogen do?
stimulate the development of secondary female characteristics
what does progesterone do?
acts with estrogen to bring about the menstrual cycle
-> helps int eh implantation of an embryo int he uterus
