topic 1 pt 2

• What does the endocrine system consist of?

  Cells that secrete hormones
• How are the cells in the endocrine system organized?

  They are either isolated cells scattered in tissue or grouped into glands
• What are the different types of communication in the endocrine system?

  • Autocrine: affects the same cells that secrete them
  • Paracrine: affects nearby cells (local)
  • Endocrine: affects cells some distance from the source (target cells/tissue)

  
• What is the characteristic of endocrine glands?


  They are ductless
• How do endocrine glands secrete hormones?

  They secrete hormones into the interstitial fluid, which diffuse into capillaries and travel in the blood
• Can you name examples of endocrine glands?

  Pituitary, thyroid, ovaries, testis
• What distinguishes exocrine glands from endocrine glands?

  Exocrine glands have ducts and secrete non-hormonal products
• What is the length of the pancreas?

  12-15 cm long
• What are the functions of the pancreas?

  • Exocrine function: Acini cells secrete enzymes for digestion, transported to the duodenum
  • Endocrine function: Pancreatic islets secrete hormones into the bloodstream
• What hormones are secreted by the pancreatic islets?

  Insulin and glucagon
• What is the role of insulin?

  It increases the uptake of glucose and amino acids into cells
• What does glucagon do?

  It controls the release of glucose into the blood and increases the breakdown of glycogen
• What are the adrenal glands also called?

  Suprarenal glands
• What hormones are secreted by the adrenal cortex?

  Mineralcorticoids, glucocorticoids, androgens
• What is the function of aldosterone?

  Retention of sodium by kidneys
• What does cortisol do?

  It increases blood glucose levels
• What hormones are secreted by the adrenal medulla?

  Epinephrine and norepinephrine
• Where are the parathyroid glands located?

  Posterior to the thyroid gland
• What is the function of parathyroid hormone (PTH)?

  It regulates calcium homeostasis
• How does PTH increase blood calcium levels?

  By stimulating osteoclasts, decreasing renal calcium excretion, and increasing calcium absorption in the GIT
• What is the location of the thyroid gland?

  In the neck, anterior to the trachea/larynx
• What are the functional units of the thyroid gland?

  • Follicles surrounded by follicular cells
  • Contain thyroglobulin
• What do follicular cells synthesize?

  T3 (Triiodothyronine) and T4 (Thyroxine)
• What condition is caused by a lack of T3 and T4?

  Hypothyroidism
• What do parafollicular cells synthesize?

  Calcitonin
• How does calcitonin affect blood calcium levels?

  It decreases blood calcium levels
• What are the two main chemical classes of hormones?

  • Amino acid based: water soluble, made from amino acids, peptides, or proteins
  • Steroid based: lipid soluble, made from cholesterol or fatty acids
• How does the chemical composition of hormones affect their function?

  It determines how they are transported in the blood and how they affect their target tissue
• What are the mechanisms of hormone action based on membrane solubility?

  1. Direct method: for lipid soluble hormones (e.g., testosterone, cortisol)
  2. Indirect method: for water soluble hormones (e.g., ACTH, TSH)
• What are the steps for the direct method of hormone action?

  1. Hormone travels in the bloodstream attached to a protein
  2. Diffuses through the plasma membrane of the target cell
  3. Attaches to a receptor inside the cell
  4. Hormone/receptor complex moves to nucleus
  5. Activates specific genes

  
• What are the steps for the indirect method of hormone action?

  1. Hormone travels free in the bloodstream
  2. Attaches to a receptor on the surface of the target cell
  3. Activates a G protein complex
  4. Alters the rate of cAMP formation
  5. cAMP activates protein-kinases

  
• What is the role of cyclic AMP (cAMP) in hormone action?

  • Acts as a second messenger
  • Changes cell permeability
  • Activates enzymes
  • Increases protein synthesis
  • Stimulates secretion
• What is the negative feedback system in hormone regulation?

  It maintains homeostasis by adjusting hormone levels in the opposite direction to the stimulus
• What are the types of stimuli that control hormone release?

  • Humoral stimulus: in response to changing blood levels
  • Neural stimulus: direct stimulation by nerves
  • Hormonal stimulus: in response to hormones from other endocrine organs

  
• What is the difference between negative feedback and positive feedback in hormone regulation?

  • Negative Feedback: Most common, adjusts hormone levels in the opposite direction to the stimulus
  • Positive Feedback: Not as common, amplifies the response in the same direction as the stimulus

  
• Can you give an example of positive feedback in the endocrine system?

  Childbirth and milk ejection
• What is an example of negative feedback in the endocrine system?

  Insulin secretion when blood glucose levels are too high
• How does the hypothalamus regulate hormone secretion?

  It uses releasing/inhibiting factors to indirectly control hormone release
• What is the role of the pituitary gland in hormone regulation?

  It releases hormones that alter cell processes affecting the concentration of other hormones in the blood
• How does the pancreas monitor blood glucose levels?

  It directly monitors blood glucose and secretes insulin when levels are too high