ch 11.7- endocrine system Flashcards
what are the types of hormones
peptide
steroid
amino acid
peptide hormones- how are they produced
produced in the rough ER and made of amino acids connected by peptide bonds
how do peptide hormones work
bind to cell surface receptors bc they are water soluble and cant pass through membrane
indirect stimulation- signal transmitted thorugh ligand gated ion channels or intracellular secondary messengers
ligant gated ion channel
change shape upon binding to peptide hormones allowing ions to flow across the membrane of the cell
no second messengers
second messenger systm
used for peptide hoomrones and allows for quick and immediate physiological changes
signal amplification
seconadary messengers example
cAMP
IP3
DAG
Ca2+
IP3/DAG pathway
Here, IP3 binds
to calcium channels on the endoplasmic reticulum,
triggering the activation and opening of these
calcium channels, releasing calcium ions into the
cytosol.
GPCRs
are cell
surface receptors that can initiate a secondary
messenger response after binding to a peptide
hormone extracellularly. A G protein is coupled to
the receptor and dissociates into subunits after
activation. These subunits then act upon intracellular
second messengers to propagate the signal.
steroid hormone synthesis
Produced in the smooth ER and made up
of a fused four-ring structure. All steroid hormones
are derived from cholesterol.
what are some examples of steroid hormones
All hormones produced by the adrenal
cortex (glucocorticoids, mineralocorticoids,
androgenic steroids) and reproductive organs
(progesterone, testosterone, estrogen).
how do steroid hormones work
Lipid-soluble (lipophilic). Therefore, require a
protein carrier to travel through the bloodstream, but
can freely cross the cell membrane. Bind to receptors
either in the cytoplasm or the nucleus to form
hormone-receptor complexes that bind to DNA, and
influence gene transcription. This process is known as
direct stimulation. Steroid hormones cause slow and
gradual physiological changes.
amino acid hormone synthesis
Produced in rough ER and cytosol.
Mainly derived from the amino acid tyrosine.
amino acid hormone examples
All hormones produced by the adrenal
medulla (epinephrine and norepinephrine, which
are water-soluble). Also includes charged amino-acid
derivatives T3 and T4 (lipid-soluble).
hypothalamus function
coordinates the body’s internal
environment and maintains homeostasis.
what is another name for the pituitary gland
hypophysis
posterior pituitary
It is a direct neuronal
extension of the hypothalamus.
what are the hormones produced by the hypothalamus
● Antidiuretic hormone (ADH aka vasopressin):
Decreases urination by increasing water retention.
Targets nephrons, increasing the number of
aquaporins for water reuptake.
● Oxytocin: Causes uterine contractions during
child labor and the release of milk during
breastfeeding (mammary gland). Oxytocin also
plays an important role in facilitating maternal
behavior (drive to be a good parent).
anterior pituitary
Produces its own hormones. It
is connected to the hypothalamus through a
hypophyseal portal system, which allows for
quick diffusion of hormones through a portal
vein.
hypothalamic releasing hormones
● GnRH (gonadotropin-releasing hormone):
Causes release of luteinizing hormone (LH) and
follicle stimulating hormone (FSH).
● TRH (thyrotropin-releasing hormone): Causes
release of thyroid stimulating hormone (TSH).
● CRH (corticotropin-releasing hormone):
Causes release of adrenocorticotropic hormone
(ACTH).
● GRH (growth hormone-releasing hormone):
Causes release of growth hormone (GH).
anterior pituiatry hormones
The anterior pituitary then produces its own
hormones, classified as tropic hormones and direct
hormones.
tropic hormones:
target other endocrine glands for
further hormone release.
direct hormones:
target organs directly for effects.
anterior pituitary direct homrones
Prolactin
growth hormone
anterior pituitary tropic hormones
FSH
LH
ACTH
TSH
FSH
Follicle
growth (females) and sperm maturation (males) in the gonads.
Stimulates follicle growth in ovaries, which
results in the increased production of
progesterone and estrogen.
Stimulates sperm maturation.
LH
Stimulates ovulation,
corpus luteum formation (females), and
testosterone production (males) in the gonads.
During menstrual cycle, the LH surge causes
ovulation. This results in the formation of a
corpus luteum, which produces progesterone
and estrogen.
Triggers testosterone production by Leydig
cells.
ACTH
Stimulates release of glucocorticoids from the
adrenal gland to fight stress. This also leads to an
increase in glucose levels in the body.
TSH
Stimulates
T3 and T4 production by the thyroid gland to
increase metabolism.
prolactin
Stimulates mammary gland
development and increases milk production after
childbirth.
growth hormone
Stimulates
body cells to grow and divide.
thyroid gland
largest endocrine organ and
is located in front of the trachea.
has three hormones
T3
Triiodothyronine
a hormone of the thyroid gland
Released in response to
TSH and increases metabolism in the body. Has
a negative feedback effect on TSH secretion.
T4
Thyroxine (T4): Performs the same actions as T3
above. However, T4 has one more iodine and
gets converted into T3 upon cell uptake. It is
much less potent than T3 but is more stable in
the blood.
calcitonin
Secreted by parafollicular thyroid
cells (C cells) to decrease blood calcium levels.
hypothyroidism
describes the under-secretion of T3
and T4, resulting in reduced levels of metabolism in
the body.
hyperthyroidism
describes the over-secretion of T3
and T4, resulting in increased levels of metabolism in
the body.
what does hypo and hyperthyroidism lead to
Both hypothyroidism and hyperthyroidism can lead
to goiter (physical enlargement of the thyroid
gland). Hypothyroidism causes over-secretion of TRH
to compensate for low T3 and T4, enlarging the
thyroid gland, while hyperthyroidism itself results
from a hyperactive thyroid gland.
A goiter is the irregular growth of the thyroid gland.
Iodine deficiency is the most common cause of a
goiter.
parathyroid gland and PTH
The parathyroid gland secretes parathyroid
hormone (PTH), which increases blood calcium levels.
pancreas
The pancreas is a gland that contains exocrine and
endocrine tissue.
endocrine: secretes digestive enzymes through
the pancreatic duct to the small intestine.
endocrine tissue of the pancreas
The endocrine tissue (the islets of Langerhans)
secretes glucagon and insulin. These two hormones
are each secreted by a different cell type as listed
below:
alpha cells
Secrete glucagon in response to
low blood glucose levels. Glucagon raises glucose
levels by stimulating the liver and fat tissue to
release their glucose storages.
beta cells
Secrete insulin in response to
high blood glucose levels. Insulin lowers glucose
levels by stimulating the liver, muscle, and fat
tissue to store glucose.
insulin
is a peptide hormone that triggers an
increase in the number of glucose transporters
embedded within the cell membrane. This increases
the facilitated diffusion of glucose from the
bloodstream into cells and reduces blood glucose
levels.
adrenal glands
Our body has two adrenal glands. Each adrenal
gland has an outer cortex and an inner medulla.
They mainly help the body deal with stress.
adrenal cortex functions
● Deals with longer term stress.
● Stimulated by secretion of ACTH from the
anterior pituitary.
● Releases steroid hormones.
● Produces glucocorticoids (i.e., cortisol) to raise
blood glucose levels for immediate fuel during
periods of long-term stress. However, this also
lowers our immune response.
● Produces mineralocorticoids (i.e.,
aldosterone) to increase blood volume and
blood pressure by raising reabsorption of Na+
.
Water passively gets reabsorbed with Na+
due to
osmosis.
● Produces a small amount of male sex hormones
(androgens).
adrenal medulla
● Deals with short-term stress.
● Stimulated by the sympathetic nervous system.
● Releases amino-acid derived hormones.
● Produces catecholamines (epinephrine and
norepinephrine) to initiate “fight or flight”
response by increasing heart rate and the
breakdown of glycogen into glucose. Epinephrine
can cause vasoconstriction or vasodilation.
LH and FSH
After stimulation by LH and FSH, the ovaries produce
progesterone and estrogen, while the testes produce
androgens such as testosterone.
