Endocrine system Flashcards
Nervous System
- Uses electrical or chemical signalling
- Neurotransmitters act locally and rapidly
- Response of the target is rapid
- Involved with responding to external environment.
Endocrine System
- Uses chemical signal
- Uses hormones transported vis bloodstream
- Target cells can respond quickly or slowly
- Less specific. One hormone may play a role in a variety of
different physiological processes - Involved with targeting internal environment of body.
Autocrines
chemicals that elicits a response in the same
cell that secreted it
Paracrines
are a chemical that is released that induces a
response in a neighbouring cells
Systemic signalling
involves hormones in bloodstream
2 major hormone groups based on chemical
structure.
- Those derived from amino acids and those derived from
lipids.
Hormone receptors have specificity, meaning?
only bind to
cells that express receptors for that hormone.
Binding of Lipid-Soluble Hormones
- A steroid hormone
directly initiates the production of proteins within a target cell. Steroid hormones and thyroid
hormones easily diffuse through the cell membrane.
The steroid hormones bind…..
to its receptor in the cytosol, forming a receptor–hormone complex. The receptor–
hormone complex then enters the nucleus and binds to the target gene on the DNA.
Lipid soluble hormones -Thyroid hormones and Steroid hormones both..
trigger the transcription of the gene and creates a messenger RNA that is translated into the desired protein
within the cytoplasm.
Water-Soluble Hormones.
are unable to diffuse through lipid bilayer of the cell membranes and must therefore
pass on their message to a receptor located at the surface of the cell.
All amino acids derived hormones (except thyroid hormones)…
Bind to cell membrane receptors that are located at least in
part on the extracellular surface of the cell membrane.
amplification.
the phosphorylation cascade significantly increases the efficiency,
speed, and specificity of the hormonal response, as thousands of signaling
events can be initiated simultaneously in response to a very low concentration
of hormone in the bloodstream.
Down regulation:
: if there is a significant level of a hormone
circulating in the bloodstream it can cause its target cells to
decrease their number of receptors for that hormone. It allows
cells to become less reactive to the excessive hormone levels.
Upregulation
when hormone levels are chronically reduced
target cells increase their number of receptors. This process
allows cells to be more sensitive to the hormone that is present.
the command centre of the endocrine system?
hypothalamus-pituitary complex
Posterior Lobe of Pituitary Gland
is directly connected to the hypothalamus via
neurons
does not produce hormones but stores
and secretes hormones produced by the hypothalamus?
The posterior pituitary gland
The cell bodies of the posterior pituitary gland are located?
in the hypothalamus but their axons descend as the
hypothalamic-hypophyseal tract within the infundibulum, and end in
axon terminals that compromise the posterior pituitary.
POSTERIOR PITUITARY: OXYTOCIN.
Oxytocin stimulates uterine contractions and dilation of the
cervix when fetal development is complete (labour).
Oxytocin is also needed for milk ejection reflex in
breastfeeding women.
POSTERIOR PITUITARY: ANTIDIURETIC HORMONE (ADH)
ADH effects is to increase epithelial permeability to water, allowing
increased water reabsorption
HYPOTHALAMIC HORMONES
- Growth Hormone Releasing Hormone (GHRH)
- Growth Hormone Inhibiting Hormone (GHIH) also known as
somatostatin - Prolactin Releasing Hormone (PRH)
- Prolactin Inhibiting Hormone (PIH) also known as dopamine
- Gonadotropin Releasing Hormone (GRH)
- Corticotropin Releasing Hormone (CRH)
- Thyrotropin Releasing Hormone (TRH)
HYPOTHALAMUS-ANTERIOR PITUITARY PORTAL SYSTEM, Within the infundibulum.
Within the infundibulum is a bridge of capillaries that
connects hypothalamus to the anterior pituitary. It is called
the hypophyseal portal system, which allows hypothalamic
hormones to be transported to the anterior pituitary without
entering systemic circulation.
CELLS IN THE ANTERIOR PITUITARY
Somatotrophs: they produce and secrete growth hormone
* Lactotrophs: they produce and secrete prolactin
* Gonadotrophs: they produce and secrete follicle stimulating
hormone and luteinizing hormone.
* Corticotrophs: they produce and secrete adrenocorticotropic
hormone
* Thyrotrophs: they produce and secrete thyroid stimulating
hormone.
Somatotrophs:
they produce and secrete growth hormone
Lactotrophs:
produce and secrete prolactin
Gonadotrophs:
they produce and secrete follicle stimulating
hormone and luteinizing hormone.
Corticotrophs:
they produce and secrete adrenocorticotropic
hormone
Thyrotrophs
they produce and secrete thyroid stimulating
hormone
Growth hormone (GH)
directly accelerates the rate of protein synthesis in
skeletal muscle and bones.
is involved/regulates growth of the human
body, tissue building, protein synthesis and cellular
respiration.
Growth hormone
THYROID STIMULATING HORMONE (TSH)
TSH regulates activity of thyroid gland
ADRENOCORTICOTROPIC HORMONE (ACTH)
- ACTH stimulates the adrenal cortex (outside layer of adrenal
gland) to secrete corticosteroids hormones such as cortisol
FOLLICLE STIMULATING HORMONE (FSH)
stimulates the production and maturation of sex cells, or
gametes including ova and sperm
LUTEINIZING HORMONE (LH)
LH triggers ovulation in women as well as the production of
estrogen and progesterone by ovaries. LH stimulates
production of testosterone in men
PROLACTIN
promotes lactation in women. During pregnancy it
contributes to development of mammary glands and after
birth it stimulates glands to produce breast milk
INTERMEDIATE PITUITARY: MELANOCYTE
STIMULATING HORMONE (MSH)
Local production of MSH in skin is responsible for melanin
production from melanocytes in response to UV light
exposure.
Thyroid hormone production is dependent on
iodine.
T3 and T4
bind to intracellular receptors located on the
mitochondria, and they cause an increase in nutrient
breakdown and the use of O2 to produce ATP.
Protein syntheses requires?
Thyroid hormones
THYROID GLAND: CALCITONIN
s released in response to a rise in blood Ca2+
levels. It reduces blood Ca2+
Calcitonin reduces blood Ca2+ levels by:
- Inhibiting the activity of osteoclasts
- Increasing osteoblastic activity
- Decrease Ca2+ absorption in intestines
- Increases Ca2+ loss in urine
PARATHYROID GLAND
secrete parathyroid hormone
(PTH)
PTH
the major hormone involved in the regulation of blood
Ca2+ levels
Chief cells secrete
PTH in response to low blood Ca2+ levels
PTH causes the release of
Ca2+ from the bones by stimulating
osteoclasts and inhibiting osteoblasts
PTH causes increased
reabsorption of Ca2+ in kidney tubules from urine filtrate.
ADRENAL GLAND Cortex is divided into 3 zones superficial to deep:
zona
glomerulosa, zona fasciculata, zona reticularis.
ADRENAL CORTEX: ZONA GLOMERULOSA
produces a group of hormones called
mineralocorticoids,
the major mineralocorticoids.
aldosterone
Aldosterone is released in response to
elevated blood K+,
low blood Na+, low blood pressure, or low blood volume.
Aldosterone increases the excretion of
K+
Aldosterone increases
retention of
Na+ (water is retained with Na+) which in turn increases
blood volume and pressure.
ADRENAL CORTEX: ZONA FASCICULATA
produces hormones called glucocorticoids and the
most important one is cortisol.
glucocorticoids and cortisol are involved in
glucose metabolism
The effects of glucocorticoids is to
inhibit tissue building
while stimulating the breakdown of stored nutrients to
maintain adequate fuel supplies.
Cortisol promotes catabolism of
glycogen, triglycerides and
even muscle proteins to amino acids to make ATP/glucose.
Cortisol also downregulates
the immune system which
inhibits the inflammatory response.
ADRENAL CORTEX: ZONA RETICULARIS
the deepest region of the adrenal cortex
which produces steroid sex hormones called androgens
ADRENAL CORTEX: ZONA RETICULARIS
androgens from the zona reticularis
supplement gonadal androgens.
releases its hormones epinephrine and
norepinephrine in response to acute, short-term stress mediated
by the sympathetic nervous system.
ADRENAL MEDULLA
The body’s 3 stage response pattern to short and long-term
stress: alarm reaction, stage of resistance and stage of
exhaustion.
GENERAL ADAPTATION SYNDROME (GAS)
GENERAL ADAPTATION SYNDROME (GAS)
Body does not attempt to maintain a homeostatic state but
instead attempts to temporarily establish different set
points so stresses can be managed
Alarm reaction is for short-term stress, the fight or flight
response, mediated by
hormones epinephrine and
norepinephrine from the adrenal medulla.
Stage of Resistance is a long-term reaction to chronic
stress. Initiated by hypothalamic releasing hormones
corticotropin, growth hormone & thyrotropin releasing
hormones
GENERAL ADAPTATION SYNDROME RESULTS
- increased secretion of aldosterone
- increased secretion of cortisol
- increase thyroid hormones (T3/T4)
Stage of Exhaustion:
Resources of the body have become
depleted
PINEAL GLAND
made up of Pinealocyte cells.
Pinealocyte cells
are known to produce
and secrete melatonin which is derived from serotonin.
Secretion of melatonin varies according to
the level of light
received from environment.
Ovaries produce
estrogens
Progesterone
produced by ovaries
Pancreas
The pancreatic exocrine function involves the acinar cells
acinar cells
secreting digestive enzymes that
are transported into the small intestine by the pancreatic duct
Pancreas endocrine function
involves the secretion of insulin (produced by beta cells) and glucagon (produced by alpha
cells) within the pancreatic islets
Alpha cells OF PANCREATIC ISLETS produce the hormone?
glucagon
Glucagon is released when
blood glucose levels are low.
Beta cells produce
insulin
insulin
Elevated blood glucose levels stimulate the release
Glucagon
- Receptors on the pancreas can sense the decline in blood glucose
levels and in response alpha cells of pancreas secrete glucagon. - Glucagon stimulates the liver to convert its stores of glycogen back
into glucose. The glucose is then released into circulation for use
by body cells. - Glucagon stimulates the liver to take up amino acids from the
blood and convert them into glucose. - Glucagon stimulates lipolysis, the breakdown of stored
triglycerides into fatty acids and glycerol. Some of the free glycerol
released into bloodstream travels to the liver, which converts into
glucose
Insulin
- Insulin facilitates the uptake of glucose into body cells.
- RBCs, brain, liver, kidneys, and the lining of the small intestine do not
have insulin receptors on their cell membranes and do not require insulin
for glucose uptake. - Although all other body cells do require insulin if they are to take up
glucose from the bloodstream, skeletal muscle cells and adipose cells are
the primary targets of insulin. - Presence of food in the intestine triggers the release of GI tract hormones
such as glucose dependent insulinotropic peptide which is the initial
trigger for insulin production and secretion by beta cells of pancreas. - Once nutrient absorption occurs, the resulting surge of blood glucose
levels further stimulates insulin secretion. - Insulin appears to activate a tyrosine kinase receptors triggering the
phosphorylation of many substrates within the cell. These multiple
biochemical reactions converge to support the movement of intracellular
vesicles containing facilitative glucose transporters to the cell membrane.
Insulin
- In absence of insulin these transport proteins are normally recycled
slowly b/w the cell membrane and cell interior. - Insulin triggers the rapid movement of a pool of glucose transporter
vesicles to the cell membrane, where they fuse and expose
glucose transporters to the extracellular fluid. The transporters
then move glucose by facilitated diffusion in to cell interior. - Insulin also reduces blood glucose levels by stimulating glycolysis.
- It also stimulates the liver to convert excess glucose into glycogen
for storage and it inhibits enzymes involved in glycogenolysis and
gluconeogenesis. - Finally insulin promotes triglycerides and protein synthesis.
- Blood glucose concentration is tightly
maintained between 70 mg/dL and
110 mg/dL. - If blood glucose concentration
rises above this range
insulin is
released, which stimulates body
cells to remove glucose from the
blood.
If blood glucose concentration
drops below this range, (7-mg/dL and 110 mg/dL)
glucagon
is released, which stimulates body
cells to release glucose into the
blood.
EICOSANOIDS
Derived from cell membrane fatty acids – arachidonic acid
EICOSANOIDS
Forms a few different molecules – prostaglandins and leukotrienes
prostaglandins and leukotrienes
very important in
regulating and modulating inflammation
Oxytocin is a hormone stored and secreted by the posterior pituitary. T or F
True
hormone that acts on the somatotroph cells of the Anterior Pituitary gland?
growth hormone releasing hormone
The anatomical site where the nervous system and endocrine system interact is the:
Hypothalamus-pituitary complex
increases water retention in the body?
aldosterone
lactotrophs of the anterior pituitary secrete which hormone
prolactin
he outermost layer of the adrenal cortex is called? and secretes?
zona glomerulosa/mineralcorticoids
hormone is secreted in response to decreased levels of blood calcium?
parathyroid hormone
part of the pituitary gland is directly connected to the hypothalamus via neurons?
the posterior pituitary gland
Insulin is produced by which cells of the pancreas?
beta cells
A chemical that a cell that releases that acts on that same cell
autocrine
Epinephrine and norepinephrine are secreted by which endocrine gland?
adrenal medulla
hormone is produced by the pineal gland?
melatonin
Which endocrine gland can be classified as both an endocrine and an exocrine gland?
pancreas
Hormones that are formed by removing a fatty acid chain from the phospholipid bilayer of a cell membrane are called:
eicosanoids
Which thyroid hormones are involved in synthesis of proteins, breakdown of fats, and increasing metabolism?
T3 and T4
resistance reaction
During the phenomena referred to as the general adaptation syndrome the resistance reaction stage is the result of alterations in hormone secretion by the hypothalamus.
Corticotropin releasing hormone (CRH) is secreted by:
the hypothalamus
How is the anterior pituitary gland connected to the hypothalamus?
via a portal system
Glucagon is secreted by which cells of the pancreas.
alpha cells
Hormones influence the activity of target cells by:
binding to hormone specific receptors on the target cells
