Download Endocrine System

The Endocrine System
 Chemical messengers
 hormones: biochemical coordination of the body
o steroids (insoluble in water), peptides and amino acid
derivatives (water soluble)
o produced in one location (gland); act on another target
area
o growth factors: developmental signals
 pheromones: communication between animals of same species
o mating, territory, alarms
 neurotransmitters: transmit nerve impulses
o between nerve cells
o between nerve cells and muscles
 We will focus on hormones (& some neurotransmitters now and
more later)
The nervous system and the endocrine system work in
conjunction to control cellular communication and homeostasis
 Nervous system = uses fast acting/short term electrical
signals in response to environmental changes.
- Neurosecretory cells releases neurohormones into
interstitial fluid
circulatory system (blood)
 The endocrine system = releases hormones that are
slower/long term responses.
- Hormones are secreted into interstitial fluid
circulatory system (blood)
 Some chemicals function in both systems
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 Regulation
1. Cells signaling – via cell receptors located on membrane or
inside the cell
2. Negative feedback – the response reduces the stimulus and
the response eventually stops
 Mechanisms of Action (Cell signaling ~ PLEASE REVIEW!)
 steroid hormones:
 enters cell via membrane diffusion (lipid soluble)
 binds to specific receptor protein [intracellular] (only
found in target cells)
- receptor protein inside cell = transcription factor
 enters nucleus = activates genes
- transcription factor
• binds to promoter region (TATA box) of DNA
• RNA Pol II can now bind to DNA and start to
unwind it
• Transcription initiated!
 Ex. estrogens, testosterone, progesterone, & cortisol
 Peptide (protein) hormones: second messenger model
 hormone binds to specific receptor on membrane
 initiation of signal transduction pathway
- series of proteins within the cell for a specific cellular
response
 activates adenylate cyclase in cytoplasm
 converts ATP to cyclic AMP (the second messenger)
– initiates cascade of reactions activating enzymes
- these activated enzymes can phosphorylate proteins
(like protein pumps)
 Ex. TSH, LH, FSH, growth factors (hormones)
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 Major Glands and Hormones (vertebrates)
 Controlling most of the endocrine system = hypothalamus &
pituitary gland (in brain).
 Hypothalamus (in brain/ part of nervous system):
- Integrates the endocrine system and nervous systems
- Specifically, the hypothalamus (nervous) controls the
pituitary (endocrine)
 Pituitary (in brain at base of hypothalamus/part of endocrine
system): “master gland”
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 Posterior Pituitary and Hypothalamus
• Hypothalamus connects to Post. Pit by nerve stimulation
• Effects = Post. Pit. releases hormones
 Hormones of Posterior Pituitary:
 antidiuretic hormone (ADH):
**target tissue = kidneys
– regulates osmolarity of blood by increasing water
retention in body; decreasing water in urine by …
– increasing the permeability of the epithelial lining of the
nephron tubule
– water will leave nephron via osmosis through collecting
duct
blood (circ. system)
– When homeostasis is reached = stop production of ADH
= = = NEGATIVE FEEDBACK
– See fig 44.16, pg. 937
 Oxytocin (OCT):
** target tissue = mammary & uterine
– regulates lactation (milk expression) and uterine
contractions
– POSITIVE FEEDBACK
 Anterior Pituitary & Hypothalamus:
• Stimulation of neurons in the hypothalamus cause the
hypothalamus to release neurohormones
- HRH = Hormone Releasing Hormones or tropic
hormones
• HRHs are released into capillaries that drain into
tubes = portals
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• Portals direct HRHs to the correct location of the
Ant. Pit.
• HRH stimulates (or inhibit) the Ant. Pit to release
hormone
circ. System (blood)
• Ant. Pit. hormones in blood will target specific glands
to release hormone
circulatory system (blood)
• To specific cells for desired response
 Hormones of Anterior Pituitary:
 thyroid–stimulating hormone (TSH):
** target tissue = thyroid
– stimulates thyroid to produce hormones (Thyroxin)
for metabolism
 adrenocorticotropin (ACTH):
** target tissue = cortex of adrenal glands
– stimulates adrenal cortex to release steroid hormones
= cortisol
– A key factor in many functions in the body's
metabolism of fats, carbohydrates, sodium,
potassium, and protein as well as blood pressure
control.
 follicle–stimulating hormone (FSH):
** target tissue – ovaries & testes
– stimulates follicle production, estrogen production, &
egg maturation
– stimulates sperm maturation & testosterone
production
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 luteinizing hormone (LH):
** target tissue – ovaries & testes
– ovulation in females/secretion of estrogen
– stimulates testosterone secretion by testes
 growth hormone (GH): growth
** target tissue – bones, cartilage, muscle, organs
- bone and cartilage = skeletal system
• Hypersecretion = gigantism
• Hyposecretion = pituitary dwarfism
Endocrine glands (some of mentioned “target tissues”):
 Thyroid (neck region; top of larynx): metabolism,
development and maturation
 thyroxine: [stimulated by TSH]
– stimulates metabolism
• of thyroxine = inhibits hypothalamus to release HRH Ant. Pit from releasing TSH (NEGATIVE FEEDBACK)
• of thyroxine = stimulates hypothalamus to release HRH
- Ant. Pit to release TSH (POSITIVE FEEDBACK)
 FEEDBACK
of TSH/Thyroxine
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 Thymus (lays of top of heart):
– Stimulated by antigen presentation of macrophage
– development of T lymphocytes
 Adrenal (top of kidneys):
o medulla of adrenal gland
 epinephrine:
– stress, scared, excited = stimulus
– increases blood sugar by
1. increasing the rate of hydrolysis of glycogen,
from liver & muscle
2. increases glucose released by liver
– increases heart rate
– dilates bronchioles
– [also part of nervous system = neurotransmitter]
 norepinephrine:
– increases heart rate
– [also part of nervous system = neurotransmitter]
o cortex of adrenal gland [stimulated by ACTH]
– stress = hypothalamus stimulus
HRH
release ACTH
– adrenal gland releases corticosteroids (cortisol)
• cortisol promotes synthesis of glucose (from
muscle protein etc.) & suppresses immune system
 Homeostasis = extra fuel when not enough blood sugar or
glycogen storage
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– additional source of sex hormones production
(mostly testosterone)
• females = sex drive
• males = not fully understood
 Pancreas: control of blood sugar (in addition to digestive
functions)
- insulin: lowers blood sugar level [glucose into cells]
- glucagon: breakdown of glycogen = raises blood sugar
[glucose]
 Gonads: [stimulated by FSH & LH]
o ovaries
- estrogens: initiate uterine lining buildup, secondary
sex female characteristics
- progesterone: growth of and maintain uterine lining
for and during pregnancy
o testis
- testosterone: spermatogenesis, male secondary sex
characteristics
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