Chapter 10 Study Guide

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• Chapter 10 Study Guide
• The Endocrine System

By Sarah Genet
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Endocrine System

• Controls body functions via hormones.
• So lets say theres too much glucose in your
  blood. Your pancreatic islets cells send insulin
  into the blood which tells your cells to start
  absorbing all the glucose, thereby decreasing the
  concentration of glucose in your blood. The
  hormone in this situation is insulin, and you can
  deduce how it is affecting bodily functions.
• Pretty big deal, no? If a patients pancreatic
  islet cells stop making insulin, or if they can
  no longer act on their target cells, that patient
  has diabetes mellitus. Do you know someone with
  diabetes?

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Two types of Glands

• The endocrine system secretes hormones using
  endocrine glands (kind of makes sense, no?)
  These are glands which lack ducts. Ducts are
  like tubes which carry hormones into the blood so
  they can be circulated around the body and
  distributed.
• So what is the other possible type of gland?
• Not endocrine, but
  exocrine.

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Hormone Types

• Nonsteroid Hormones Proteins, short chain amino
  acids or single amino acids
• Proteins are water soluble and therefore cannot
  pass through the cell membrane. Therefore
  nonsteroid hormones affect the activity of the
  cell via a secondary messenger system (see lock
  and key model and cyclic AMP)
• Steroid Hormone Lipid soluble steroid hormone
• Can pass through a cells cell membrane, travel
  through the cytoplasm, enter the nucleus and act
  on DNA (see hormone receptor complex)

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Prostaglandins

• Not actually hormones.hormones are produced in
  one location (for example, insulin is made only
  in the pancreas) but prostaglandins are produced
  in many places, throughout the body
• Prostaglandins are frequently produced in tissues
  and act locally. In other words, they are
  produced in a tissue and diffuse a short distance
  to act on cells within that tissue

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Regulation of Hormone Secretion

• Negative feedback the output of a system acts to
  oppose changes to the input of the system
• Ex) During periods of high blood sugar pancreatic
  islet cells secrete insulin in order to decrease
  blood sugar levels and bring them back to normal.
  
• Positive feedback amplify changes to the system
• Ex) Oxytocin increases the force of contractions
  during labor

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Endocrine Glands

• Hypothalamus
• Pituitary
• Pineal
• Thyroid
• Parathyroid
• Thymus
• Adrenal
• Pancreas
• Ovaries (female), Testes (male)

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Pituitary Gland

• Located in sella turcica of the Sphenoid bone
• Two parts
• Anterior pituitary,aka adenohypophysis
• Posterior pituitary, aka neurohypophysis

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Pituitary Hormones

• Anterior Pituitary
• FLAT (all tropic hormones)
• FSH
• LH
• ACTH
• TSH
• PG
• Prolactin
• GH

• Posterior Pituitary
• ADH
• Oxytocin

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Pituitary Disorders

• Hyperglycemia too much sugar in blood. One
  cause is too much GH
• Diabetes Insipidus dehydration and electrolyte
  imbalance due to hyposecretion of ADH

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Hypothalamus

• Nervous and endocrine function
• Nervous Specialized neurons produce ADH and
  oxytocin (to posterior pit.)
• Endocrine - Releases releasing and inhibiting
  hormones. These travel to the anterior pituitary
  and cause the ant. Pit. to release or inhibit the
  production/release of hormones.

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Thyroid Gland

• Located in neck below the larynx
• Secretes T3 (thyroxine) and T4 (triiodothyronine).
  T3 has 3 molecules of iodine and T4 has 4
  molecules of iodine.
• Stores T3 and T4 in the follicle. Most endocrine
  organs do not store hormones, so this function is
  unique!
• Secretes calcitonin decreases concentration of
  calcium in the body. This hormone is used to
  prevent an excess of calcium in the blood, a
  condition known as hypercalcemia.

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Example of negative feedback

• In this diagram T3 and T4 perform negative
  feedback on the anterior pituitary and the
  hypothalamus, causing them to decrease their
  release of TSH and TRH.

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Thyroid Hormone Abnormalities

• Hyperthyroidism over secretion of thyroid
  hormone
• Hypothyroidism under secretion of thyroid
  hormone
• Simple Goiter enlargement of thyroid gland
  caused by low dietary intake of iodine
• Cretinism hyopsecretion of thyroid hormone
  during formative years
• Myxedema hyposecretion of thyroid hormone later
  in life.

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Parathyroid Gland

• Located on the back of the thyroid
• Secretes parathyroid hormone (PTH) increases
  blood calcium levels.
• What hormone decreases blood calcium levels?

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Adrenal Gland

• Composed of two endocrine glands the adrenal
  cortex and the adrenal medulla

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Adrenal Gland

• Adrenal Cortex - secretes corticoids
• mineralocorticoids (MC). ex) aldosterone
• Glucocorticoids (GC) ex) cortisol aka
  hydrocortisone
• Sex hormones ex)androgens

• Adrenal Medulla
• Epinephrine and norepinephrine

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Adrenal Medulla Abnormalities

• Cushings Syndrome overproduction of adrenal
  cortex hormones. Symptoms include moon-face,
  buffalo hump on upper back, elevated blood sugar
  and frequent infections (Seen in photo below)
• Addisons Disease hyposecretion of adrenal
  cortex hormones. Results in muscle weakness,
  reduced blood sugar, nausea, loss of appetite and
  weight loss

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Pancreatic Islet

• Located in exocrine pancreas.
• Two types alpha and beta cells. Alpha release
  glucagon and beta release insulin.
• Glucagon ? increased blood glucose concentration
  via liver glycogenolysis
• Insulin ? decreased blood glucose concentration
• Secrete pancreatic enzyme juice.

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Diabetes Mellitus

• Type I diabetes increase in blood glucose
  levels due to hyposecretion of insulin
• Type II diabetes increase in blood glucose due
  to an abnormality of insulin receptors.
  Sometimes accompanies by hyposecretion of
  insulin.
• Diabetes Mellitus results in glycosuria - glucose
  in the urine. Doctors can diagnose diabetes by
  checking the blood for urine.

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Sex Glands - Female

• Female Sex Glands two ovaries
• Composed of two parts
• the follicle secretes estrogen and the egg or
  ova developes here
• Estrogen involved in development and maturation
  of breast and external genitalia, development of
  adult female contours (hips, curves) and
  initiation of the menstrual cycle
• Corpus Luteum secretes
• progesterone and some estrogen.

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Sex Glands - Male

• The testes are made of many cell types. One cell
  type, the interstitial cell, makes testosterone
  which is the male sex hormone.
• Testosterone masculinizing hormone
  maturation of external genitalia, beard growth,
  changes in voice at puberty, muscular development
  and male contour.

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Thymus

• Located in the mediastinum (adults) or may extend
  up into the neck as far as the bottom of the
  thyroid gland (infants)
• Composed of a cortex and medulla. What other
  organ contains a cortex and medulla?
• Both parts are composed of lymphocytes the
  thymus plays a critical role in defense against
  infections
• Produces thymosin

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Placenta

• Temporary endocrine
• structure present during pregnancy
• Produces chorionic gonadotropins
• (tropic hormones produce by the chorion),
  estrogen and progesterone
• During the earlier weeks of pregnancy the kidneys
  excrete large amounts of chorionic gonadotropins
  into the urine. So, when a woman takes a
  pregnancy test the test is looking for the
  presence of this hormone ?

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Pineal Gland

• Located near the roof of the third ventricle in
  the brain.
• Easily located in a child but not in an adult.
  This is because the gland becomes encrusted with
  calcium deposits as a person ages.
• Makes many hormones, the most important one being
  melatonin.
• Melatonin inhibits the tropic hormones which
  affect the ovaries and is through to be involved
  in regulating the onset of puberty and the
  menstruation in women. The release of melatonin
  is increased during the night and decreased
  during the day.

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Additional Endocrine Structures

• Atrial Natriuretic Hormone secreted by cells
  in the hearts atria (upper chambers of the
  heart). Regulates fluid and electrolytes in the
  body and is an antagonist to aldoesterone.
  (Aldosterone causes the body to hold on to sodium
  and water while ANH stimulates the loss of sodium
  and water.
• Leptin secreted by fat storing cells.
  Regulates how hungry/full we feel and how fat is
  metabolized by the body.