• The   endocrine   system   and   how   it   functions   in   communication   in   multicellular   organisms.
• Homeostasis   and   sugar   levels
• How   hormones   regulate   the   fight ‐ or ‐ flight   response
• Reproduction   and   hormonal   control
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All   Multicellular   Organisms   Must
Coordinate   Their   Functions
• The   animal   body   needs   to   communicate   so   that   the   whole   organism   can   develop   and   function   effectively
• The   endocrine   system   consists of   different   glands   that   release   a   variety   of   signaling   molecules   called   hormones
• Animal   hormones   are   produced   by   specialized   cells   organized   into   discrete   organs   called   endocrine   glands
• Endocrine   glands   release   hormones   into   body   fluids,   which   then   carry   these   chemical   messengers   throughout   the   body
• The   hypothalamus   is   responsible   for   coordinating   the   endocrine   system   and   integrating   it   with   the   nervous   system
• The   hypothalamus   contains   both   neurons   that   interact   with   the   brain   and   also   endocrine   cells   that   produce   hormones
• The   hypothalamus   makes   hormones   that   tells   the   pituitary   to   release   hormones
• These   hormones   from   the   pituitary   will   travel   through   the   circulatory   system   to   regulate   the   various   endocrine   glands.
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The   Endocrine   System
• Hormones   are   often   distributed   through   the   body   by   the   circulatory   system   and   therefore   move   only   as   fast   as   blood   is   circulated
• Hormones   are   effective   in   small   amounts   because   they   bind   to   target   cells   with   great   specificity
• A   single   hormone   can   produce   a   diversity   of   effects   in   a   variety   of   potential   target   cells
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• A   hormone   released   by   one   cell   causes   one   or   more   specific   responses   in   the   target   cells,   which   may   lie   in   more   than   one   type   of   tissue
• Hormones   can   act   on   target   cells   by   binding   to   plasma   membrane   receptors   or   intracellular   receptors
Hormonal   Signals   to   the   Cell
• Hormonal   signals   are   amplified   inside   the   target   cell   and   alter   key   cellular   processes
• There   are   four   main   categories   of   cellular   responses   produces   by   a   hormonal   signal:
– Changes   in   protein   production
– Changes   in   metabolism
– Changes   in   the   activity   of   the   cytoskeleton
– Changes   in   plasma   membrane   transport
Hormonal   Signals   to   the   Cell
• Animals   usually   produce   hormones   in   tiny   amounts   measured   in   micrograms
• Signal   Transduction ‐ When   hormone   molecules   bind   to   receptors   in   the   target   cell,   they   set   in   motion   a   chain   of   events   that   may   activate   thousands   of   protein   molecules   in   that   cell
• Through   signal   amplification,   just   a   few   hormone   molecules   can   have   a   substantial   impact   on   the   whole   body
Hormonal   Signals   to   the   Cell
• Notice   the   amplification   of   the   signal
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Hormonal   Signals   to   the   Cell
• Some   hormones   bind   to   receptors   on   the   plasma   membrane
• Others,   like   steroids,   are   able   to   cross   the   plasma   membrane   and   deliver   the   hormonal   message   within   the   cell
• Glucose   homeostasis   is   controlled   by   the   pancreas
• The   pancreas   functions   as   endocrine   glands   and   also   as   exocrine   glands
• The   pancreas   contains   clusters   of   endocrine   cells   called   islet   cells that   produce   and   release   insulin   and   glucagon
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Specific   Hormonal   Processes   we   will   Cover
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Glucose   Homeostasis
• Insulin   and   glucagon   are   hormones   that   act   in   opposite   ways   to   maintain   homeostasis   in   blood   glucose   levels
• Insulin   acts   on   target   cells   throughout   the   body,   but   especially   in   the   liver,   fat   tissue,   and   skeletal   muscles,   signaling   these   cells   to   increase   their   uptake   of   glucose   from   the   blood
• Insulin=   into   cell   out   of   blood
• Causes   decrease   blood   sugar
• Glucagon=   gone   from   cell   into   blood
• Causes   increased   blood   sugar
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Disruption   in   Glucose   Homeostasis:
Diabetes
• Too   much   glucose   in   the   blood   results   in   diabetes
• Most   cases   of   type   1   diabetes   result   from:
– autoimmune damage   to   the   islet   cells   preventing   insulin   production   or
– production   of   a   defective   form   of   insulin   by   the   pancreas
• Type   2   diabetes   occurs   when:
– too   little   insulin   is   produced   or
– the   receptors   on   target   cells   respond   poorly   to   insulin
Short   Term   Control:
Fight ‐ or ‐ Flight   Response
• The   adrenals   regulate   the   fight ‐ or ‐ flight   response
• The   adrenal   glands   are   a   pair   of   endocrine   glands   that   sit   on   top   of   the   kidneys   and   release   epinephrine   and   norepinephrine ,   which   coordinate   our   response   to   sudden   stress
Short   Term   Control:
Fight ‐ or ‐ Flight   Response
• Epinephrine   stimulates   glycogen   breakdown   in   liver   and   skeletal   muscle   cells,   which   raises   blood   glucose   levels   and   in   turn   increases   the   speed   and   force   with   which   the   heart   contracts
Regulating   Long ‐ Term
Processes:   Reproduction
• Animals   rely   on   hormones   to   regulate   nearly   all   aspects   of   reproduction
• In   humans,   hormones   influence   nearly   all   aspects   of   sexual   development   and   reproduction,   including   sperm   production   in   males   and   the   menstrual   cycle   of   women
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Sex   Hormones   Play   a   Role   in
Sexual   Development   before   Birth
• It   is   through   the   action   of   the   hormones   that   a   fetus   develops   into   a   male   or   a   female
• By   the   seventh   week   of   the   fetus’s   development,   the   sex   glands,   or gonads, are   producing   the   sex   hormones
• These   sex   hormones   signal   genes   in   their   target   cells   to   begin   the   process   of   sexual   development
• The   gonads   of   both   sexes   produce   estrogens,   progestogens,   and   androgens   in   varying   amounts
Sex   Hormones   Play   a   Role   in
Sexual   Development   before   Birth
• Estrogen produces   female   characteristics,   while   progestogens ,   including   progesterone ,   create   a   suitable   environment   for   a   developing   fetus
• Androgens, such   as   testosterone ,   stimulate   cells   to   develop   the   characteristics   of   maleness
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Sex   Hormones   Coordinate
Sexual   Maturation   at   Puberty
• During   puberty,   the   hypothalamus   makes
Gonadotropin   Releasing
Hormone   (GnRH)   that    activates   the   production   of   gonadatropins made   in   the   pituitary   gland
• These   gonadatropins,
Luteinizing   hormone   (LH)   and   follicle ‐ stimulating   hormone
(FSH)   coordinate   the   development   of   sperm   in   males   and   play   a   role   in   regulating   the   menstrual   cycle   in   females
GnRH
Sex   Hormones   Coordinate   the   Menstrual   Cycle
• In   humans   females,   individual   eggs   mature   and   are   released   in   a   hormone ‐ driven   sequence   of   events   known   as   the   menstrual   cycle
• The   menstrual   cycle   is   marked   by   a   succession   of   hormones   that:
– stimulate   the   release   of   an   egg
– prepare   the   uterine   lining   for   a   potential   pregnancy
Sex   Hormones   Coordinate   the   Menstrual   Cycle
• The   menstrual   cycle   is   marked   by   a   succession   of   hormones   that   stimulate   the   release   of   an   egg   and   prepare   the   uterine   lining   to   grow   and   thicken   in   preparation   for   a   potential   pregnancy
Sex   Hormones   Coordinate   the   Menstrual   Cycle
• Between   40   and   50   years   of   age,   a   drop   in   the   levels   of   estrogen   and   progesterone   results   in   menopause,   in   which   the   menstrual   cycle   ceases   permanently
• practice   with   closed   note:
– Flow   chart   for   sugar   regulation
– Flow   chart   for   the   fight ‐ or ‐ flight   response
– Paragraph   description   of   reproduction   and   hormonal   control
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