Endocrine System

• Functions of the endocrine system:

  • Controls growth and development
  • Regulates metabolism
  • Regulates chemical composition in internal and external environments
  • Regulates the operation of reproductive systems
  • Regulates some immune function
  • Helps establish circadian rhythms
• Exocrine vs Endocrine:

  • Exocrine glands secrete substances into a duct system
  • Endocrine glands secrete substances directly into the bloodstream as hormones
  • Hormones have specific receptors on target organs
• Types of chemical messengers:

  • Autocrine: Stimulate cells that originally secreted it
  • Paracrine: Act locally on neighboring cells
  • Neurotransmitters: Secreted by neurons that activate an adjacent cell
  • Endocrine: Hormones that travel through general circulation
• Types of Hormones:

  • Non-steroid Hormones:
  • Water soluble
  • Whole proteins or amino acids
  • Use second messengers
  • Steroid Hormones:
  • Lipid soluble
  • Can pass through the membrane of the target cell
  • Typically slower working, due to going into the cell themselves
• Hormone effects:

  • Permissive effect
  • -a target cell is made more responsive to a second hormone when the first has opened receptor sites
  • Synergistic Effect
  • -two hormones acting together has a greater effect than the sum of each individual one
  • Antagonistic Effect
  • -one hormone opposes the action of another
• Hormone secretions:

  • Hypothalamus regulates both divisions of the pituitary (Anterior- Adenohypophysis) and (Posterior- Neurohypophysis)
  • Anterior- hypothalamic control through blood vessel network
  • Posterior- hypothalamic control through direct connection
  • Anterior pituitary hormones:
  • FSH: Follicle Growth/Sperm Production
  • LH: Ovulation/Testosterone Formation
  • ACTH: Directs the adrenal cortex
  • TSH: Directs the thyroid
  • Prolactin: Breast development and milk production
  • Growth Hormone: Stimulates growth in most tissues and plays a role in height
  • Tropic Hormones: Direct other endocrine glands
• Hypothalamus & Posterior Pituitary

  -Antidiuretic Hormone (ADH)/ Vasopressin- water conservation

  -Oxytocin- uterine contractions during labor and milk let-down
• Thyroid Gland:

  • Thyroid hormone (T3 and T4): Controls metabolism, regulates growth of bone, hair, teeth, and nervous tissue, and maturation of organs
  • Calcitonin: Lowers blood calcium by putting calcium into bones
• Parathyroid Gland:

  • Parathyroid Hormone: Controls blood calcium levels by putting calcium into the blood
• Adrenal Glands:

  • Adrenal medulla releases Norepinephrine and Epinephrine (adrenaline) to prepare the body for activity
  • Adrenal cortex:
  • Mineralocorticoids (e.g., Aldosterone): Sodium reabsorption
  • Glucocorticoids (e.g., Cortisol): Inhibits inflammation, dampens immune response, and increases gluconeogenesis
  • Adrenal androgens: Weak androgens affecting female development
• Pancreas:

  • Insulin (Beta cells): Lowers blood glucose levels
  • Glucagon (Alpha cells): Raises blood glucose levels
• Sex glands:

  • Female (ovaries): Estrogen and progesterone
  • Male (testicles): Testosterone
  • Controlled by FSH and LH
• Pineal gland:

  • Melatonin: Controls the body's internal clock and sleep patterns
• Homeostatic Imbalances:

  • Growth hormone abnormalities:
  • Dwarfism: Low levels of growth hormone leading to slow growth
  • Giantism: Hypersecretion of growth hormone during childhood
  • Acromegaly: Hypersecretion of growth hormone during adulthood
  • Diabetes insipidus: Large urine volumes and constant thirst due to insufficient ADH production or receptor issues
  • Diabetes Type I: Too little insulin production leading to hyperglycemia
  • Diabetes Type II: Insulin resistance with abnormal insulin receptors
• Thyroid Disorders

  Hypothyroidism

  -hyposecretion of thyroid hormone

  -"Cretinism"

  -Symptoms: slower metabolism, always cold, tendency to gain weight, constipation

  
  

  Hyperthyroidism

  -hypersecretion of thyroid hormone

  -"Grave's Disease

  -Symptoms: bulging eyes, faster metabolism, always hot, tendency to be skinny, and dirahea
• Hormone Regulation

  Negative Feedback

  -Hormones are used to reverse the environment or if levels get out of balance

  Positive Feedback

  -used to amplify changes

  -released for muscle contractions during labors, continues to release to increase contractions
• Parathyroid Disorders

  Hypoparathyroidism

  -too little PTH

  -Symptoms: low blood calcium, muscle twitches and spasms

  
  

  Hyperparathyroidism

  -too much PTH

  -Symptoms: high PTH levels, bone weakness, and kidney stones
• Suprarenal Gland Disorder

  Cushing's Syndrome

  -hypersecretion of cortisol

  -"Moon face" and "Buffalo Hump"

  -Symptoms: easy bruising, poor wound healing, hypertension

  Addison's Disease

  -hyposecretion of glucocorticoid and aldosterone

  -"Bronze" skin

  -Symptoms: lethargy, anorexia and/ or weight loss, muscle weakness