Endorcrine System Flashcards
describe chemical coordination
a slow, prolonged process of communicating information throughout the body by way of chemicals called hormones
what are endocrine glands
the special glands or tissue that secrete hormones
what is the difference between the chemical and nervous coordination
chemical coordination
- brought about by the endocrine system
- influences metabolic activities of all cells by means of chemicals (hormones)
- hormones travel through the blood system
- conduction is slow
- causes a widespread response in many target organs
- the responses is slow but long lasting
Nervous coordination
- brought about by the nervous system
- regulates the activities of muscles and glands by means of electrical impulses
- impulses conducted by neurons
- conduction is very fast
- chases a specific response in one target organ (effector)
- response is rapid but only lasts a short time
what is a hormone
a chemical substance, usually a protein but sometimes a steroid, secreted by an endocrine gland and carried in the blood stream to its target organs where it regulates metabolic reactions
why don’t hormones last long in the body
because they’re broken down my enzymes
do hormones operate alone
no. they form an integrated system with other hormones as well as with the nervous system
what are some different hormones categorized by chemical structure
peptides, steroids and amines
what is a steroid and what is a amine
steroid - synthesis based on cholesterol substrate carbon atoms arranged in 4 rings
amines - biochemical modifications of a single amino acid (tyrosine)
what are some hormones that are categorized by function
the main category of interest is androgens (male hormones) which occur in both males and females but in higher levels in males.
these include:
- testosterone
- androstenedione
- dihydrotestosterone
in women’s bodies a key function of androgens is to be converted to oestrogen
what are come complications with androgen
hyperandrogenism
and androgen insensitivity
what is a target organ
the specific cells that respond to a given hormone and that have receptor sites. in some cases these are located in a single gland or organ, in other cases they’re scattered throughout the body so many areas are affected
describe an endocrine gland
a small, vascular, ductless gland that secretes hormones which are carried in the bloodstream to their target organs
endocrine glands in the body - label diagram
page 212
what is the hypothalamus and what does it control
a part of the brain, situated above the pituitary gland. it controls the functioning of the autonomic nervous system as well as the release of hormones from the pituitary gland
why is the hypothalamus considered a gland
because some of its neurons secrete the hormone anti-diuretic hormone ADH
what does ADH do
passes down nerve fibres to be stored in the posterior lobe of the pituitary
how does the hypothalamus control the release of hormones
- when hormones from the anterior lobe of the pituitary are needed. the hypothalamus secretes releasing factors that travel in the blood to the anterior lobe, stimulating it to produce and release the required hormones
- when ADH and other hormones are needed, nerve impulses from the hypothalamus stimulate the posterior lobe of the pituitary to release the stored ADH into the bloodstream
why is the pituitary gland called the “master gland”
because it is the chemical coordinator of most of the other endocrine glands
where the pituitary situated
attached stalk and is situated in a small bony cavity in the floor of the cranium called the ‘Turkish saddle’
what’s another name for the pituitary
hypophysis
how is the pituitary made up
made up of two glands
- large anterior lobe is purely glandular and made up of secretory cells
- small prosterior lobe develops from the base of the brain and mainly made up of neurons
what are 7 hormones released from the anterior pituitary lobe
- growth hormone or Somatrophic hormone STH - promotes skeletal growth and muscular growth by stimulating the synthesis of proteins
- thyroid stimulating hormone TSH - stimulates the thyroid gland to secrete its hormone, thyroxin
- adrenocorticotropic hormone ACTH - stimulates the the adrenal cortex to secrete mainly the hormones cortisone and aldosterone
- follicle stimulating hormone FSH - (in females) stimulates oogenesis in the ovary, formation of eggs. (in males) stimulates spermatogenesis in the tests, formation of sperm
- luteinizing hormone LH - (in females) stimulates ovulation, release of an egg, from the ovary
- interstitial cell stimulating hormone ICSH - chemically similar to LH but produced in males to stimulate the testes to secrete testosterone
- prolactin - stimulates the production of milk in the female mammary glands for as long as the baby suckles and it is responsible for much of the maternal instinct
what growth disorders can occur
in prepubertal children:
hyper-secretion
hypo-secretion
in adults:
hyper-secretion
explain hyper-secretion in children
hyper-secretion of growth hormone results in the overdevelopment of the skeleton (a condition known as gigantism)
caused by a tumor in the pituitary gland
is very rare
explain hypo-secretion in children
hypo-secretion of growth hormone results in underdevelopment for the skeleton (condition known as pituitary dwarfism)
caused by a disease of the anterior one pituitary gland
although height is reduced the body proportions are normal
they’re not mentally retarded but often sexually immature
they can be treated by injection of synthetic growth hormone produced genetically by engineered bacteria
explain hyper-secretion in adults
hyper-secretion results in enlarged hands, jawbone and brows ie. all terminal skeletal structures (condition known as acromegaly)
in adults bone can only thicken because the growth points in the long bones are no longer active
what are endocrine glands stimulated by
changes in the composition of blood and they respond by either secreting more or less of their hormones
what is the difference between exocrine endocrine glands
exocrine glands - their secretions are carried in ducts to where they are needed (eg. salivary glands, liver, pancreas)
endocrine glands - don’t have ducts and their secretions are carried in the blood stream to their target organs
• the hormones are bonded to the target cells (meaning they’re rapidly transported to all parts of the body)
draw a diagram or an endocrine and exocrine gland
page 212/ slide 6
when does the posterior lobe release ADH
when osmoreceptors in the hypothalamus detect an increase in the osmolarity of the blood, nerve impulses stimulate the posterior lobe to release stored ADH
what is the role of ADH
• helps to conserve water if the body is dehydrated
- it does this by causing more water to be reabsorbed back into the blood from the collecting ducts of the kidney so less water is lost in urine
what disorder can occur in relation to ADH
lack of ADH secretion causes diabetes insipidus (a condition characterized by the loss of large quantities of dilute urine 5-10 liters a day)