CelltoCell Signaling: Hormones and Receptors

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Cell-to-Cell Signaling Hormones and Receptors

• By Jen Haller
• Katie Stokes

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Introduction to Hormones

• Hormones are messengers.
• They derive from amino acids, fatty acids or
  proteins.
• They exist in a dilute concentration.
• Our bodies must monitor and control hormone
  levels.
• Hormones have a very short life span.

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Cell Communication System

• No cell is alone
• Cell signaling regulates nearly every function
  that our body undergoes.
• Without this simple communication system, humans
  would not be able to exist.

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How Hormones Work

• Hormones bond onto receptors.
• A G-protein inside the cell is activated.
• There are several different kinds of G-proteins.
  Target cells transform shape when they accept
  hormones.
• The G-protein can then activate important
  functions two different ways.
• There are several different signaling methods

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ary/Cell-Cell_Communication/default.htm
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Endocrine Signaling

• Endocrine signaling releases hormones into the
  blood stream.
• The hormones are carried to the appropriate
  target cells.
• Every target cell has a receptor.
• Endocrine signaling is used when the
  transportation distance exceeds the ability of
  diffusion.
• In large multi-cellular organisms endocrine
  signaling is preferable.

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Endocrine Communication
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Science/Cell_Signaling/Scientific_Resources/Pathwa
y_Slides___Charts/Cell_Signaling_in_Lipids.html
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Paracrine Signaling

• Paracrine signaling uses local mediators to
  send messages from the signaling cell to the
  target cell.
• The hormones are released into the surrounding
  fluids and then diffuse into nearby cells.
• Autocrine signaling is a type of paracrine
  signaling in which the hormones effect the cells
  that created them.
• Synaptic signaling is the most advanced type of
  paracrine signaling. An example of synaptic
  signaling occurs between the CNS and muscle cells
  allowing the cells to communicate and carry out
  certain actions.

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Paracrine Communication
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y_Slides___Charts/Cell_Signaling_in_Lipids.html
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Neuronal Signaling

• Connect to each other through synapses
• Synapses are small gaps between neurons.
• Chemical substances are released from the
  pre-synaptic neuron to affect the post synaptic
  neuron.
• Post synaptic neurons have receptors that these
  chemical substances bind to.
• A neuron can connect to a muscle cell as well as
  to other neurons.

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Neuronal Communication
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y_Slides___Charts/Cell_Signaling_in_Lipids.html
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Contact-Dependant Signaling

• Contact dependant signaling is direct contact
  between the signaling cell and the receptor.
• This is only used for close vicinity signaling.

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Contact Dependant Communication
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Science/Cell_Signaling/Scientific_Resources/Pathwa
y_Slides___Charts/Cell_Signaling_in_Lipids.html
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Cell Feedback

• When enough hormone has been produced, it is sent
  back to the signaling cell.
• This stops the signaling cell from sending
  chemicals.
• This is called a feedback loop.
• Without this, serious imbalances can result,
  which can cause serious diseases.

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Steroid hormones

• There are two kinds of hormones.
• Steroids include Sex hormones and adrenaline
• Relatively small and diffuse in and out of cells
  easily
• The cells affected contain receptor proteins in
  the cytoplasm
• Hormone receptor complex moves into the nucleus.
  The complex binds to the DNA and it starts
  protein synthesis
• Full effect of the hormone takes hours to days

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Non-steroid hormones

• Includes Amines, peptides, growth hormone and
  insulin
• Do not diffuse into cells
• The target cells have receptors on cell surface
• The hormone binds to the receptor and a second
  messenger is released in the cell
• This causes rapid response to hormones within
  minutes or seconds.

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Important Hormones

• Insulin
• Adrenaline
• Thyroxine
• Estrogen
• Testosterone
• Progesterone

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Insulin

• One of the early hormones that was discovered.
• It is produced in the pancreas
• It is a life dependent function. It keeps glucose
  levels in a homeostasis level.
• If cell receptors do not accept insulin or there
  is no insulin, this is a cause of diabetes

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Adrenaline

• Is produced in the adrenal glands near the
  kidneys
• It is secreted in response to stress and fear.
• Stimulates heart action, increases blood
  pressure, increases metabolism, and increases
  blood sugar

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Thyroxine

• Is produced in the thyroid gland.
• Helps control metabolism, caloric requirements,
  oxygen consumption, growth and development, brain
  functions, and the nervous system activities.

http//www.mabot.com/brain/index.html
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Sex Dependant Hormones

• Sex dependant hormones are steroidal hormones.
  They include estrogen, progesterone, and
  testosterone.
• These hormones regulate specific sex
  characteristics for male and female humans.

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Estrogen

• Estrogen is a steroid hormone produced in the
  ovaries. It controls female sex characteristics
  such as the development of breasts and the
  thickening of thighs
• It causes the storing of fat beneath the skin.
• It makes women's skin smoother and thinner.
• Counteracts the lengthening of limb bones.
• Causes pelvic bones to become wider.

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Progesterone

• Progesterone is produced in the ovaries.
• Progesterone prepares the uterus for growing a
  baby.
• It maintains the cells of the uterine wall.
• Causes menstruation.
• Is also used as a birth control and to help
  prevent miscarriages.

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Testosterone

• Testosterone is produced in the testes.
• Testosterone increases size of male reproductive
  system.
• It thickens the skin, causes facial hair, and
  decreases head hair growth.
• Increased muscular strength, strengthened bones,
  and increased aggressiveness are also caused.

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Hormonal and Receptor Imbalances

• Because receptors and hormones are sensitive, it
  is easy for them to become imbalanced. These
  imbalances can lead to many serious diseases and
  bodily malfunctions. These include

• Diabetes
• Parkinsons
• Alzheimer's
• Gigantism/Dwarfism
• Leukemia
• Obesity
• Heart attacks

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Imbalances

• Receptor and hormonal imbalances are caused
  several different ways
• If the signaling cells do not produce enough of a
  specific hormone.
• If the targeting cell cannot receive the hormone,
  for various reasons.
• Or, if the targeting cell cannot carry out the
  desired function.

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Tumor Cells

• When tumors cells are formed, they dont respond
  to the feedback cell.
• This results in the tumor cells not being
  regulated and therefore grow excessively
• They can then produce hormones or other chemicals
  in excess.

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Diabetes

• Diabetes is cause by an abnormality of blood
  glucose levels.
• Common symptoms include excessive urination and
  excessive thirst.
• Complications are abnormalities in blood vessels
  that can cause heart failure, blindness, and
  podiatry problems. This is caused by weaknesses
  in vessels of organs.
• Insulin injections are helpful to prevent
  diabetes from becoming worse.
• There is no cure at this time, however research
  into transplant activities continues.

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Alzheimer's

• Caused by a change in the distribution of
  neurotransmitter receptors
• Symptoms include gradual decline in daily
  routines, change in behavior, personality,
  memory, and understanding.
• Most common cause of dementia in people over the
  age of 65.

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Parkinson's

• Dopamine neurostransmitter that is formed in the
  brain that controls central nervous system and
  unconscious automatic movements.
• Parkinsons is caused by damage or loss of
  dopamine cells.
• Syndrome that decreases movement, increases
  muscle rigidity, and impairs reflexes.
• The onset is gradual and insidious
• Symptoms may include Tremors, limping, difficult
  swallowing, bradykinesia
• Bradykinesia loss of automatic movements
  drooling, slouching posture, little facial
  expression, difficulty initiating movements.
• Severe case symptoms include Orthostatic
  hypotension, dizziness, falling, oily skin,
  dandruff, conjunctivitis, difficulty in reading,
  insomnia

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Gigantism

• Gigantism is caused by an over secretion of
  growth hormones. Meaning that the pituitary sends
  out excessive growth hormones and causes
  excessive growth

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Dwarfism

• Dwarfism is not enough growth hormone which
  stunts growth of a person.

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Conclusion

• Cell signaling is essential for life. It
  controls all hormone levels, and nearly all
  bodily functions. Part of the cycle includes cell
  feedback. If the feedback is blocked, the
  hormones will continue to be produced in excess
  which can lead to serious illnesses.

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Sources

• Young, John K. Hormones Molecular Messengers.
  Franklin Watts. New York. 1994.
• Lewis and Heitkemper. 2000 Medical Surgical
  Nursing. Mosby. New York.
• Alberts, et al. 1998Forms of Cell Signaling.
  Garland Publishing. Available http//wwwaccessexc
  ellence.org/RC/VL/GG/cellSignals.html February
  14, 2005
• Hormones and Cell to Cell Signaling. Online
  Available http//www.esf.edu/efb/course/EFB325/le
  ctures/hormone.htm February 17, 2005
• Cell Signaling online Available
  http//darwin.nmsu.edu/molbio/mcb520/lecture10.ht
  ml February 15, 2005
• Types of Hormones. Online Available
  http//e.hormone.tulane.edu/learning/typesofhormon
  es.html February 17, 2005
• Cell Communication. Online Available
  http//facultyweb.maconstate.edu/clee/2107/Lecture
  /chapter_11.htm February 15, 2005
• Dr. Jeffrey Haller, Personal Interview, February
  18, 2005.

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Jeopardy