Endocrine system

• Oxytocin causes uterine contractions during childbirth and milk ejection from mammary glands.
• Exocrine Glands:

  • Act locally
  • Secrete products through ducts
• Endocrine Glands:

  • Act from a distance
  • Secrete products directly into bloodstream
• Hormones:

  • Signaling molecules secreted into the bloodstream
• Tropic Hormones:

  • Act on other endocrine glands and stimulate the release of another endocrine hormone
• Non-Tropic Hormones:

  • Act on target tissues and cause direct physiological effect
• Peptide Hormones:

  • One or multiple chains of amino acids
  • Hydrophilic
  • Diffuse freely in the bloodstream
  • CANNOT pass freely through cell membrane
  • Rapid, short-term changes
  • Typically use secondary messengers
• Steroid Hormones:

  • Four-ring structure
  • Hydrophobic
  • Must use carrier proteins to travel in bloodstream
  • Can pass freely through cell membrane
  • Typically cause translational changes
• Negative Feedback Loops:

  • Downstream product inhibits earlier point in the pathway
• Positive Feedback Loops:

  • Downstream product stimulates its own production
• Anterior Pituitary Hormones:

  • Follicle-Stimulating Hormone (FSH)
  • Luteinizing Hormone (LH)
  • Adrenocorticotropic Hormone (ACTH)
  • Thyroid-stimulating hormone (TSH)
  • Prolactin
  • Endorphins
  • Growth hormone
• Posterior Pituitary Hormones:

  • Oxytocin
  • Anti-diuretic hormone (ADH or “vasopressin”)
• Prolactin:

  • Acts on mammary glands to stimulate milk production
• Endorphins:

  • Reduce perception of pain
• Thyroid-Stimulating Hormone (TSH):

  • Hypothalamus releases thyrotropin-releasing hormone (TRH)
  • Anterior pituitary secretes TSH
  • TSH acts on thyroid to stimulate production of T3 and T4
• Adrenocorticotropic Hormone (ACTH):

  • Hypothalamus releases corticotropin-releasing hormone (CRH)
  • Anterior pituitary secretes ACTH
  • ACTH acts on adrenal gland to stimulate production of glucocorticoids
• Growth Hormone:

  • Hypothalamus releases growth hormone-releasing hormone (GHRH)
  • Anterior pituitary secretes growth hormone
  • Growth hormone is involved in cell growth
• Oxytocin:

  • Facilitates lactation, childbirth, and plays a role in social bonding
• Antidiuretic Hormone (ADH):

  • Inhibits diuresis and promotes water reabsorption in kidneys
  • Released when blood volume is low
• Thyroid Gland:

  • Secretes T3 & T4
  • T3 and T4 increase metabolic rate
  • Secretes calcitonin
  • Calcitonin reduces blood calcium levels
• Adrenal Cortex:

  • Secretes corticosteroids:
  • Glucocorticoids: Cortisol increases blood glucose levels
  • Mineralocorticoids: Aldosterone promotes fluid retention
  • Sex hormones (e.g., androgens)
• Adrenal Medulla:

  • Secretes epinephrine and norepinephrine
  • Mediate “fight-or-flight” response
• Pancreas:

  • Alpha cells secrete glucagon
  • Glucagon raises blood glucose
  • Beta cells secrete insulin
  • Insulin reduces blood glucose
  • Delta cells secrete somatostatin
  • Somatostatin inhibits gastrointestinal activity
• Reproductive Organs:

  • Testes secrete testosterone
  • Ovaries secrete estrogen
• Pineal Gland:

  • Secretes melatonin
  • Melatonin helps regulate circadian rhythms
• Heart:

  • Secretes atrial natriuretic peptide (ANP)
  • ANP promotes fluid loss
• Hormones secreted to RAISE blood glucose when it is low:

  • Glucagon
  • Cortisol
  • Epinephrine
  • Growth hormone
• Hormones secreted to LOWER blood glucose when it is high:

  • Insulin
• Hormones secreted to RAISE blood calcium when it is low:

  • Parathyroid hormone (PTH)
  • Vitamin D (calcitriol)
• Hormones secreted to LOWER blood calcium when it is high:

  • Calcitonin
• In chronic stress:

  • Cortisol increases blood glucose levels
• In acute stress:

  • Epinephrine & norepinephrine increase blood glucose levels
• Epinephrine & norepinephrine increase blood glucose levels
• Hormones secreted to LOWER blood pressure when it is high:

  • Atrial natriuretic peptide (ANP)
• Hormones secreted to RAISE blood pressure when it is low:

  • Aldosterone
  • Anti-diuretic hormone (ADH)
• Renin is released when fluid levels are low and cleaves angiotensinogen to make angiotensin I
• Angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II
• Angiotensin II travels to the adrenal cortex and stimulates release of aldosterone
• Aldosterone promotes sodium reabsorption
• T3 and T4 are related to metabolic rate