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)