Transcript The Endocrine System

H1: Hormonal Control
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Endocrine System: a system of glands that
secrete hormones to regulate body function
HORMONES: chemical messengers or
regulators
- they are released by cells in one part of the
body and affect cells in other parts of the
body to speed up or slow down processes.
Endocrine Hormones – are produced in
endocrine glands and secreted directly in the
blood and distributed by the circulatory
system.
Makes hormones
and regulates the
pituitary gland
Pineal gland
(makes serotonin
which regulates
sleep patterns)
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Note: Hormones do not affect ALL cells
Depends on whether or not that cell has a
receptor for the particular hormone.
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(TARGET CELLS are the cells hormones act on)
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There are 2 types of hormones:
1. Steroid Hormones
2. Protein Hormones
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made from cholesterol (lipid); Complex ring
of C, H, and O
Soluble in fat but NOT water – so can dissolve
through cell membrane
Inside the cell they bind to receptor in the
cytoplasm or nucleus to form the hormonereceptor complex
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The receptor-hormone complex can then
switch certain genes on or off by promoting
or inhibiting the transcription of genes
ex: sex hormones
ex: cortisol (stimulates the conversion of
amino acids to glucose by the liver and
decreases expression of insulin)
Steroid Hormones
SECRETORY
CELL
HORMONE
TARGET CELL
RECEPTOR
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Made of chains of amino acids or modified
amino acids
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Soluble in water but insoluble in fats (can’t
dissolve through cell membrane)
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Ex: insulin, growth hormone
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The protein hormones attach to receptor sites
on the cell membrane
The hormone-receptor complex leads to the
release of a secondary messenger in the cell
that can spread throughout the cell and relay
messages
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Ex of secondary messengers: Ca2+ and cyclic
adenosine monophosphate (cyclic AMP)
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Secondary messengers then activate enzymes
in the cell.
Protein
Hormones
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The body relies on the nervous system and
the endocrine system for control of organs
and tissues
The nervous system allows the body to adjust
quickly to environmental changes
The endocrine system is designed to maintain
control over longer durations
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The hypothalamus in the brain is part of both
the nervous system and the endocrine system
As an endocrine gland it creates hormones
that either
◦ a) are stored in the (posterior) pituitary gland
◦ b) control the release of hormones from the
(anterior) pituitary gland
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“master gland” because it controls the other
endocrine glands
(However, it is controlled by the hypothalamus)
Located at the base of the brain; connected to the
hypothalamus by a stalk
The pituitary produces and
stores hormones
The hypothalamus stimulates
their release when necessary
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Stores and releases hormones that are actually made
by the neurosecretory cells of the hypothalamus
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The hormones travel from the hypothalamus to the
pituitary via specialized nerve cells
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They are stored in the pituitary and released into the
blood when necessary
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(The hypothalamus will send a nerve response to
have the hormones released)
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Ex: ADH (antidiuretic hormone), oxytocin
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Ex: ADH release
◦ Hypothalamus creates ADH and stores it in pituitary
gland
◦ Osmoreceptors in hypothalamus recognize osmotic
pressure (solute concentration of blood)
◦ Impulses are sent to pituitary to increase or inhibit
the release of ADH into blood stream accordingly
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Produces its own hormones
However, the hypothalamus regulate their release
with inhibiting or releasing hormones made by
the hypothalamus
The inhibiting and releasing hormones are
transported to the anterior lobe of the pituitary
via specialized nerve cells
This stimulates the release of pituitary hormones
which will travel through the blood to target cells
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Ex: TSH and TRH
The anterior lobe produces and stores TSH
(thyroid stimulating hormone)
TSH is released by the anterior lobe when the
hypothalamus releases TRH (thyroid releasing
hormone)
Ie cortisol
Hormone
Thyroid Stimulating
Hormone (TSH)
Target Organ
Thyroid Gland
Adrenocorticotropic Adrenal Cortex
Hormone (ACTH)
Primary Function
Releases hormones made in the
thyroid (such as thyroxine)
Stimulates the release of hormones
involved in the stress response (such
as cortisol)
Promotes growth
Somatotropin (STH)
also known as
Growth Hormone
(GH)
Follicle Stimulating
Hormone (FSH)
Most body cells
Gonads (ovaries
and testes)
Females: stimulates follicle
development in the ovaries
Males: Promotes the development of
sperm cells in the testes
Luteinizing
Hormone (LH)
Gonads (ovaries
and testes)
Females: stimulates ovulation and the
formation of the corpus luteum
Males: stimulates the production of
testosterone
Prolactin
Mammary Glands
Maintains milk production in lactating
Hormone
Antidiuretic
Hormone
(ADH)
Oxytocin
Target
Organ
kidneys
Primary Function
Increases water
reabsorption in the
kidney
Uterus,
Initiates strong uterine
mammar contractions
y glands Triggers milk release in
lactating females