Endocrine System

• Endocrine System consists of:

  • Pineal
  • Hypothalamus
  • Pituitary gland
  • Thyroid
  • Parathyroid
  • Thymus
  • Adrenal Cortex
  • Kidney
  • Pancreas
  • Testes (male)
  • Ovary (female)
  • Uterus (female)
• Types of Endocrine Gland Stimuli

  • humoral stimulus
  • neural stimulus
  • hormonal stimulus
• Humoral stimulus

  • low concentration of calcium in the capillaries stimulates secretion of parathyroid hormone which acts to increase calcium
• Neural stimulus

  • preganglionic sympathetic fibers stimulate adrenal medulla cells to secrete catecholamines (epinephrine and norepinephrine)
• Hormonal stimulus

  • hypothalamus secretes hormones that stimulate the anterior pituitary gland to stimulate other endocrine glands to secrete hormones
• Pituitary Gland (hypophysis)

  • small bean-shaped gland at the base of the brain, located in a bony cavity in the base of the skull, the sella turcica
  • secretions control the other endocrine glands and influence growth, metabolism, and maturation

  Divided into two:

  • anterior pituitary (adenohypophysis)
  • posterior pituitary (neurohypophysis/pars nervosa)
• Cell types in Hypophysis

  • chromophobes
  • acidophils (alpha cells)
  • basophils (beta cells)
  • pituicytes
• Pars intermedia

  • part of anterior pituitary
  • thin cell layer between the pars distalis and neurohypophysis
  • thin zone of basophilic cells
• Pars Tuberalis

  • part of anterior pituitary
  • surrounds the neural stalk
  • consists of basophilic secretory cells
• Pars distalis

  • part of anterior pituitary
  • consist of secretory cells called chromophils (acidophils and basophils) and chromophobes
  • largest part of the hypophysis
• Median eminence

  • part of posterior pituitary
  • located at the base of the hypothalamus from which extends the pituitary stalk or infundibulum
• Infundibulum

  • part of posterior pituitary
  • where unmyelinated axons are located and extend from the neurons in the hypothalamus
  • connects the hypophysis with hypothalamus
• Pars nervosa

  • part of posterior pituitary
  • contains the unmyelinated axons of secretory hypothalamic neurons, their endings with hormones and the supportive cells called pituicytes
• Hypothalamus

  • main roles is to keep the body in homeostasis
  • sends signals to the pituitary to release or inhibit pituitary hormone production
  • acts as the connector between the endocrine and nervous systems
• Neurohormones

  • substances that the hypothalamus secretes to start and stop the secretion of pituitary hormones
• Anti-diuretic hormone

  • one of the primary hormones secreted by the hypothalamus
  • this hormone increases water absorption into the blood by the kidneys
• Corticotropin-releasing hormone

  • one of the primary hormones secreted by the hypothalamus
  • sends a message to the anterior pituitary gland to stimulate the adrenal glands to release corticosteroids, which help regulate metabolism and immune response
• Gonadotropin-releasing hormone

  • one of the primary hormones secreted by the hypothalamus
  • stimulates the anterior pituitary to release follicle stimulating hormone (FSH) and luteinizing hormone (LH), which work together to ensure normal functioning of the ovaries and testes
• Growth hormone-releasing/inhibiting hormone

  • one of the primary hormones secreted by the hypothalamus
  • prompts the anterior pituitary to release growth hormone or vice versa
• Oxytocin

  • one of the primary hormones secreted by hypothalamus
  • is involved in a variety of processes, such as orgasm, the ability to trust, body temperature, sleep cycles, and the release of breast milk
  • sometimes known as "cuddle hormone" or "love hormone"
• Prolactin-releasing/inhibiting hormone (dopamine)

  • one of the primary hormones secreted by hypothalamus
  • prompts the anterior pituitary to stimulate breast milk production through the production of prolactin and vise versa
• Thyrotropin releasing hormone

  • one of the primary hormones secreted by the hypothalamus
  • triggers the release of thyroid stimulating hormone (TSH), which stimulates release of thyroid hormones, which regulate metabolism, energy, and growth and development
• Adrenal Glands

  • these are endocrine glands located at the top of kidneys

  Composed of 2 structures:

  • adrenal cortex
  • adrenal medulla
• Adrenal medulla

  • inner layer of adrenal gland
  • consists of polyhedral cells arranged in cords or clumps
• Adrenal cortex

  • outer layer of adrenal gland
  • consists of cords of epithelial secretory cells arranged in 3 different patterns and layers
• Zona glomerulosa

  • tissue type in adrenal cortex
  • releases mineralcorticoids (aldosterone)
• Zona fasciculata

  • tissue area of adrenal cortex
  • releases glucocorticoids (cortisol, corticosterone, cortisone)
• Zona reticularis

  • tissue area in adrenal cortex
  • releases androgens (dehydroepiandrosterone)
• Adrenal medulla

  • tissue area in adrenal cortex
  • releases stress hormones (epinephrine, norepinephrine)
• Aldosterone

  • example of mineralcorticoids
  • help in regulation of blood pressure and electrolyte balance
• Cortisol, Corticosterone, and Cortisone

  • example of glucocorticoids
  • functions include the regulation of metabolism and immune system suppression
• Dehydroepiandrosterone

  • example of androgen
  • androgens that are converted to fully functional sex hormones in the gonads and other target organs
• Epinephrine and norepinephrine

  • example of stress hormones
  • secrete catecholamines which produce a rapid response throughout the body in stress situations
• Glucocorticoid

  • anti-inflammatory effect and widely used in ointments to relieve swelling and other signs of inflammation
• Addison's disease

  • result of hyposecretion of the adrenol cortical hormones
• Cushing's syndrome

  • result of hypersecretion of the adrenal cortex, primarily cortisol
• Stress

  • any condition that threatens homeostasis
• General Adaptation Syndrome

  • it is our body's response to stress-causing factors
• 3 Stages of GAS

  • alarm stage: perceiving the stress
  • resistance stage: body adapts and focuses resources against stressor
  • exhaustion stage: stress is beyond the body's capacity and resources are exhausted
• Pancreatic Islets

  • compact spherical or egg-shaped masses of endocrine tissue embedded within the exocrine tissue of pancreas