Thursday, Mar 24 Part III of course Regulation of Internal States

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Thursday, Mar 24 Part III of
courseRegulation of Internal States
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• Types of Hormones
• Reproductive hormones control the menstrual
  cycle, child birth, breast feeding (activational
  effects). Organizational effects instruct the
  body to develop as male or female.
• Homeostatic hormones maintain internal bodily
  environment relevant to life itself the balance
  of sugars, proteins, carbohydrates, fats, salt
  and water in the bloodstream and all body cells
  (activational effects that cells can respond to
  from early life)
• Stress Hormones control behavioral and
  physiological responses to stress (best
  understood re. activational effects)

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Brain must regulate 3 primary internal states-
temperature- water balance- nutrient and energy
supply (food)Homeostatic control - maintains at
relatively constant values within an optimal
range
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• Body has a particular weight at which it
  functions best.
• Homeostatic control mechanisms are designed to
  keep us there.
• Our size depends on stored energy levels.
• Energy from food intake energy burned energy
  stored.
• 8 needed for digestion 55 for maintaining
  body heat and other vital functions
• Remainder needs to be active behavior

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Homeostatic control - maintains at relatively
constant values within an optimal rangeIdeal
values - the set pointsMaintained by-
negative feedback systems- redundant controls-
behavioral actions
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• Food intake
• proteins broken down into amino acids
• fats broken down into simpler fats (lipids)
• carbohydrates, starches and sugars broken down
  into glucose
• Much debate about ideal ratios for consumption!

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Food intake ? Digestion ? delivery of energy and
nutrients to the body for use and
storage Immediate use Glucose, amino acids,
nutrientsStored forms Glycogen (quick use
stored form of glucose)ProteinsFats (primary
mode of energy storage) - 1 gram of fat can
store twice as much energy as glycogen. -
Glycogen holds too much water and weighs more.
If we stored as glycogen instead of fat we
would weigh 3-4 times more)
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Glucose- the brains primary source of energy-
primary source for cells of body- in body cells
(not brain), insulin is necessary for glucose to
enter cellLiver is the primary reservoir for
glucose and its stored form, glycogen.Liver is
the short-term carbohydrate reservoir.Adipose
tissue (fat) is the long term energy reservoir.
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Energy utilization is controlled by 2 hormones
from the pancreas Insulin Glucagon
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Role of insulin 1) aids use of glucose -
movement from blood into cells 2) promotes
conversion of blood-borne useable fuels to
stored forms (glucose to glycogen and fat amino
acids to protein) 3) aids storage of glycogen in
liver and muscle fat in adipose tissue
proteins in muscle
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Nobel prize for Insulin discovery 1923 Banting
and Macleod - Canadian
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Role of Glucagon 1) stimulates conversion of
glycogen into glucose 2) promotes release of
fatty acids from storage in adipose tissue 3)
aids in conversion of fatty acids to useable
energy (ketones) for muscles
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Feedback system for control of glucose and
glycogen levelsFood in digestive tract--gt
available glucose--gt glucose in blood --gt brain
reads levelsdirectly and gets info. from the
vagus nerve from liverTells pancreas to secrete
insulin--gt tells liver to convert glucose to
glycogen
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Food in digestive tract--gt available glucose--gt
glucose in blood --gt brain reads levelsTells
pancreas to secrete insulin--gt tells liver to
convert glucose to glycogenGlucose levels in
blood fall --gt brains reads and tells pancreas to
secrete glucagonTells liver to convert glycogen
to glucose
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Glucostat - feedback control system for glucose
Brain centers that contain glucose
detectors1. Brainstem - medulla and pons -
process information from vagus nerve coming from
the liver analyze the glucose levels in the
surrounding tissue2. Hypothalamus
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Brain centers that contain glucose detectors1.
Brainstem - medulla and pons - process
information from vagus nerve coming from the
liver analyze the glucose levels in the
surrounding tissue2. Hypothalamus - several
areas contain glucose detectors and other
relevant detectors also process information from
other sources3. Circumventricular organs
(lining of ventricles)
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Information about body status is signalled by
1) stomach and gut (cholecystokinin) 2) liver -
vagus nerve 3) blood - glucose and several
hormones4) fat cells - leptin
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Diseases related to glucose regulation1.
Diabetes mellitus (type 1 diabetes) early
childhood onsetPancreas stop producing
insulin.Brain can use glucose from diet but body
cannot.Excess glucose in blood cannot be stored
goes to kidneys for removal increases thirst
to help, but dehydration may result.Excess
glucose can damage tissues like kidneys, retina,
peripheral nerves also results from decreased
blood flow acidosis.
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Diseases related to glucose regulation1. Type
2 Diabetes loss of response to insulin (insulin
resistance) as well as reduced insulin
releasemajority of cases occur in overweight or
obese individualsSimilar complications.Dietary
change and exercise can reverse the condition.
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• Pancreatic hormones and fat
• insulin promotes storage of glucose into
  glycogen and fatty acids into fat
• glucagon promotes conversion of glycogen to
  glucose and fat to fatty acids for use
• Regulatory systems are quite complex with respect
  to energy utilization, storage , and
  appetite/satiation signals.