Endocrine System

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Chapter 45

• Endocrine System

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Endocrine System

• Made of hormones and cells that produce them
• Hormones chemical messages that have been
  activated by a stimulus
• effect target cells
• can be prolonged and irreversible
• mostly reversible

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Four classes of hormones

• Peptide hormones chains of amino acids
• Amino acid based single amino acids
• Steroid hormones resemble cholesterol
• Prostaglandins synthesized from fatty acids

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Hormone action

• carried in the blood
• target cells have specific receptors
• plasma membrane (used by peptide and amino acid
  hormones)
• utilize a secondary messenger (cAMP)
• causes signal to be amplified
• inside the cell (used by steroids)

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Hormone action inside a cell

• Bind to receptors in the nucleus
• cause gene expression to occur which produces
  proteins that activate a cell activity

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Hormone regulation

• Regulated by negative feedback cycles
• hormone action causes a response in the target
  cell to turn off secretion of the hormone
• ADH action and water retention
• some are regulated by positive feedback
• oxytocin and labor

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Types of Glands

• Exocrine secrete products into digestive tract
  or other hollow tubes
• sweat glands, tear glands, mammary glands
• Endocrine secrete hormones directly into the
  blood

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Hypothalamus and Pituitary

• Hypothalamus controls many hormone secretions
• contain neurosecretory cells
• Pituitary is associated with hypothalamus
• anterior true endocrine gland
• posterior growth from hypothalamus

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Hypothalamus and Pituitary

• Hypothalamus controls anterior pituitary
• releasing hormones or inhibiting hormones

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Anterior Pituitary

• Types of hormones released
• Hormones that regulate endocrine glands
• FSH follicle stimulating hormone
• LH leuteinizing hormone
• both stimulate production of sex cells and sex
  steroids
• TSH thyroid stimulating hormone
• causes thyroid to release hormones
• ACTH andrenocorticotropic hormone
• causes adrenal cortex to release hormones

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Anterior Pituitary cont.

• Hormones that have direct effect
• Prolactin development of mammary glands
• Endorphins inhibit pain receptors
• MSH melanocyte stimulating hormone
• stimulates synthesis of melanin
• Growth hormone regulates body growth
• stimulates protein synthesis, fat utilization,
  storage of carbohydrates

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Posterior Pituitary

• contains the endings of neurosecretory cells
• Produces
• ADH antidiuretic hormone
• oxytocin

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Thyroid and Parathyroid Glands

• Thyroid produces
• thyroxine raises metabolic rate of most cells
• helps regulate growth of nervous system in
  juvenilles
• diet low in iodine causes an increase in
  thyroxine producing cells
• causes a goiter
• calcitonin calcium metabolism

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Parathyroid

• located on the back of the thyroid
• Parathormone causes release of calcium from
  bones
• calcitonin inhibits release of calcium from
  bones

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Pancreas

• both endocrine and exocrine
• Islet cells endocrine portion
• produce insulin and glucagon
• insulin reduces blood glucose levels
• glucagon increases blood glucose levels

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Diabetes mellitus

• Condition where blood sugar levels fluctuate
  wildly
• This causes the body to rely heavily on fats,
  increasing cholesterol
• causes kidney failure, blindness, and loss of
  extremities

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Steroid Hormones

• Testes produce androgens
• testosterone
• Ovaries produce estrogen and progesterone
• important in development and menstrual cycle
• Increase in LH and FSH from Hypothalamus lead to
  increase in steroid hormones causing puberty

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Adrenal Glands

• Two glands in one
• adrenal cortex and adrenal medulla
• Adrenal medulla is connected with nervous system
• epinephrine (adrenaline)
• norepinephrine (noradrenaline)
• both prepare the body for emergencies

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Adrenal Gland cont

• Adrenal cortex
• secretes glucocorticoids and aldoseterone
• stimulated by ACTH
• Glucocorticoids
• controls glucose metabolism
• Aldosterone
• controls sodium levels by telling kidneys to
  absorb more sodium
• Cortex also release testosterone in small amounts

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Prostaglandins

• produced by most cells in the body
• causes
• artery constriction
• works with oxytocin during delivery
• inflammation

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Other sources of hormones

• Pineal gland
• located in the brain
• produces melatonin
• regulated by sunlight
• Thymus
• located in the chest cavity
• produces white blood cells
• thymosin important in T cell production

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Other sources of hormones

• Kidneys
• erythropoietin
• renin
• Heart
• produces atrial natriuretic peptide (ANP)
• causes distension in the heart
• Digestive system
• gastin, secretin, and cholecystokinin

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Other sources of hormones

• Fat
• leptin
• absence cause weight gain