Endocrine System Functions and Glands

Study Notes

Controls and coordinates the body's response to environmental changes using hormones.
Regulates bodily functions using glands and hormones.

Hypothalamus: Maintains homeostasis, regulates temperature, heart rate, and blood pressure.
Pituitary Gland: Composed of two lobes:
- Anterior: Secretes hormones for growth and development.
- Posterior: Secretes hormones that increase water reabsorption in the kidneys.
Pineal Gland: Produces melatonin, which regulates the sleep-wake cycle.
Thyroid Gland: Produces three hormones:
- Calcitonin: Regulates calcium levels in the blood.
- Triiodothyronine (T3): Regulates metabolism and energy production.
- Thyroxine (T4): Regulates metabolism and energy production.
Parathyroid Gland: Secretes hormones essential for calcium absorption.
Thymus: Controls the production of T-cells, white blood cells crucial for fighting diseases.
Ovaries & Testes: Release hormones affecting blood circulation, mental vigor, and sex drive.
- Ovaries: Secrete estrogen and progesterone, vital for the female reproductive system.
- Testes: Secrete testosterone, essential for physical development, bone density, and libido.
Pancreas: Aids in digestion of proteins, fats, and carbohydrates. Produces insulin and glucagon, which regulate blood glucose levels.
Adrenal Gland: Produces adrenaline and cortisol, enabling the body to respond to stress.

Protein Hormones (Peptide Hormones): Bind to receptor proteins on cell membrane surfaces.
- Binding triggers chemical reactions involving "second messengers" (e.g., calcium ions (Ca2+) and cyclic AMP (cAMP)).
- Second messengers activate or inactivate enzymes, affecting cellular processes.
Steroid (Lipid) Hormones: Bind to receptor proteins in the cytoplasm or nucleus of target cells.
- Derived from cholesterol.
- Form a "hormone-receptor complex" within the cell.
- This complex acts as a transcription factor, influencing DNA expression and protein synthesis.
Amino Acid Derived Hormones: Bind to cell surface membrane receptors.
- Derived from modifications of tyrosine or tryptophan molecules.
- Binding activates secondary proteins or enzymes in the membrane (e.g., G-proteins).
- Activates second (and sometimes third) messenger systems (e.g., cAMP or Ca2+), leading to a cellular response.

Posterior Pituitary: Releases two peptide hormones:
- Oxytocin: Involved in uterine contractions and milk ejection.
- Vasopressin (ADH): Regulates water reabsorption in the kidneys.
Anterior Pituitary: Releases six hormones:
- Prolactin (PRL): Stimulates milk production.
- Thyrotropin (TSH): Stimulates the thyroid gland.
- Adrenocorticotropin (ACTH): Stimulates the adrenal gland.
- Growth Hormone (GH): Promotes growth and development.
- Follicle-stimulating hormone (FSH): Regulates egg and sperm production.
- Luteinizing hormone (LH): Regulates ovulation and testosterone production.

Synergism: Two or more hormones produce the same effects, amplifying the overall response.
Permissiveness: One hormone requires the presence of another to exert its full effect.
Antagonism: One hormone opposes or reverses the effect of another.

Type I: Simple squamous cells where gas exchange occurs.
Type II (Septal Cells): Secretes alveolar fluid containing surfactant, which reduces surface tension in the alveoli.
Alveolar Dust Cells: Macrophages that remove debris from the alveoli.

Pulmonary Ventilation: Movement of air in and out of the lungs (inhalation/inspiration and exhalation/expiration).
External Respiration: Gas exchange between the lungs and blood capillaries.
Transport of Gases: Oxygen and carbon dioxide travel to and from tissue cells.
Internal Respiration: Gas exchange between blood capillaries and tissue cells.

Ideal Gas Law: PV = nRT (describes the relationship between pressure, volume, temperature, and the number of moles of a gas).
Boyle's Gas Law: The pressure and volume of a gas are inversely related.
- Increased volume lowers pressure, allowing air to flow into the lungs.
- Decreased volume raises pressure, forcing air out of the lungs.