endocrine system
DESCRIPTION
TRANSCRIPT
Greek- to excite Chemicals released in minute amount
that can elicit specific response
• Not all hormones are released by glands (e.g. Hypothalamus)
Nerves communicate faster due to impulses and structure of neurons
The endocrine system is responsible for slower biological processes (e.g. Growth)
The endocrine system and nervous system are structurally, chemically and functionally related
Presence of neurosecretory cells- specialized neurons
Chemicals that function as both hormones and neurotransmitters
Positive feedback• Nervous- opening of sodium ion gates
during the threshold potential• Endocrine- release of milk
Negative feedback
Hydra- hormone for growth and budding; prevents sexual reproduction
More complex- both are integrated in the control of reproduction and development
Aplysia- hormone for egg-laying counters feeding and locomotion
Arthropods- presence of ecdysone• Insects- secreted by prothoracic glands
Responsible for molting Favors metamorphosis Some insects- presence of brain
hormone (BH)• Promotes development by stimulating the
prothoracic glands Juvenile hormone (JH)- balances BH
and ecdysone• From corpora allata
Occurs when corpora allata stops producing JH• Regulation of production is not known
Could be nervous or neurohormonal Adult: inhibition via nervous
connection in the brain
Larvae: corpora allata is activated by neurohumoral factor from the brain during development
Inactivated by nervous inhibition before metamorphosis
Endocrine glands- ductless glands that release hormones (via the bloodstream)
Paracrine glands- like endocrine but target adjacent cells
Exocrine glands- release secretions through ducts
Holocrine- releases secretions through rupture of the plasma membrane (oil gland)
Apocrine – releases secretions through membrane-bound vesicles (mammary gland)
Merocrine- releases their secretion through exocytosis of their secretory vesicles
hormones- via the bloodstream Local regulators- targets nearby cells Pheromones- carry messages to
different individuals• Mate attraction
Secreted by cells to nearby/adjacent target cells• E.g. Interleukin, growth factor
Peptides and proteins that stimulate cell proliferation
a given growth factor can have different effects depending on the target cell• Nerve growth factor (NGF)
Speeds up development of embryonic nerve cells
Also affects developing white blood cell and other kinds of cell
A form of a non-surgical operation in treating injuries
Use of blood plasma where some growth factors are present
Highly reactive and toxic Action is rapid When secreted by neurons:
neurotransmitter WBC: kills bacteria and cancer cells Endothelial cells: dilate BVs; relax
smooth muscles
Modified fatty acid from lipids of plasma membrane
First found in semen In semen: stimulates uterine
contraction In placenta: induce labor Induce fever, inflammation and
intensify sensation of pain PGE: muscle relaxation in the lungs PGF: muscle contraction in the lungs
Signal molecule: has specific shape Reception: binding of signal to
receptor• Located at the plasma membrane or inside
the cell Signal transduction- series of events
signalled by the reception of signal mol on the plasma membrane
Response- change in a cell’s behavior
Occurs if there is a correct signal molecule
Specific receptor is present Depends on the location of the
binding site of a signal molecule
Signal transduction• Receptor is on the surface• Composed of series of events that can lead to
a response• E.g. Response is in the form of enzyme
activation Change in gene expression
• Signal molecule penetrates the cell and binds to a receptor inside
• Receptor acts as transcription factor• Change in gene expression
Darkness of skin depends on arrangement of melanocytes in the skin
Light skin: melanosome at the nuclei Dark skin: melanosome in the
cytoplasm Arrangement of melanosome is
controlled by MSH
Secreted by the pituitary gland MSH present: melanosomes disperse MSH absent: at the nuclei Direct injection does not lead to
dispersion• Why?
Signal receptor at the plasma membrane
Converts extracellular signal to intracellular response
Can amplify a signal to substantial response