HORMONES QUIZ

Endocrine System

• The endocrine system is made up of glands that secrete hormones directly into the blood.

Hormones

• Hormones are chemical substances secreted directly into the blood by ductless glands.
• They can be classified into two groups:
  • Peptide Hormones: Formed from proteins, have a quick onset time, cannot pass cell membrane, and are hydrophilic. Examples include insulin and growth hormone.
  • Steroid Hormones: Formed from fats, can enter the cell membrane, are hydrophilic, and have a slower onset than peptide hormones. Examples include estrogen, progesterone, and testosterone.

Tropic Hormones

• Tropic hormones are hormones that stimulate other glands to release hormones.
• They have a far-reaching effect because they can trigger a cascade of hormonal release.
• Example: The anterior pituitary releases thyroid-stimulating hormone (TSH), which then stimulates the thyroid gland to produce thyroxine.

Hypothalamus

• The hypothalamus acts as a bridge between the endocrine and nervous systems.
• It functions both as part of the nervous system and as an endocrine gland:
  • Nervous System Function: During stress, the hypothalamus sends electrical signals to the adrenal gland to release adrenaline.
  • Endocrine Gland Function: It produces oxytocin and antidiuretic hormone, which are stored in the posterior pituitary.
  • Regulatory Function: The hypothalamus also regulates temperature, hunger, thirst, and coughing.

Pituitary Gland

• The pituitary gland releases several hormones, including FSH and LH.

Functions of Hormones

• Hormones control the body's response to stress.
• They regulate metabolism and growth and development.
• Hormones do not trigger rapid, short-term responses; this function is carried out by the nervous system.

Hormone Action

• For a hormone to work, it must reach its target cells, be produced and released, and enter the bloodstream or fluids around cells.
• Hormones do not travel through ducts.
• Hormones bind to receptor proteins on the surface of target cells, triggering a cascade of events that ultimately lead to the desired change in cell function.

Nervous System vs. Endocrine System

• Nervous signals are much faster than hormonal messages but have shorter-lasting effects.
• Nerve transmissions reach many cells at once, while hormonal messages can be more targeted.

Endocrine Glands

• All endocrine glands secrete hormones directly into the bloodstream or the fluid around cells.
• Not all hormones affect every cell near the gland.
• Hormones are not always lipid molecules.

Organs with Endocrine Function

• The brain, stomach, small intestine, and lungs all contain cells that have an endocrine function.

Prostaglandins

• Prostaglandins are hormone-like substances that accumulate in areas of tissue disturbance or injury.

Hormone Binding

• When a hormone binds to a receptor, the receptor protein changes shape, which then triggers a series of chemical reactions inside the cell, ultimately leading to a change in cell activity.
• Hormones do not enter the cell by endocytosis.

Amino-Acid-Based Hormones

• Amino-acid-based hormones bind to receptors in the cell membrane, triggering the activation of a second messenger like cyclic AMP.
• They do not pass through the cell membrane; they activate a chain reaction to cause a change inside the cell.

Steroid Hormones

• Steroid hormones are fat-soluble and can pass through the cell membranes of their target cells.
• They are not always bound to fat receptor molecules.
• They can influence gene expression in target cells.

Hormone Regulation

• The liver plays a role in feedback by removing hormones from the blood and breaking them down.

Anterior Pituitary Gland

• The anterior pituitary gland secretes several tropins, including follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyroid-stimulating hormone (TSH).
• It does not produce antidiuretic hormone (ADH).

Pituitary Gland Regulation

• Hormones produced by the pituitary gland are regulated by secretions from the hypothalamus.
• They control the activity of other endocrine glands and affect many organs and tissues.
• The pituitary gland does not primarily regulate metabolic rate; this is primarily regulated by the thyroid gland.

Hypothalamus-Pituitary Relationship

• The hypothalamus acts as the regulatory center of the endocrine system, controlling the activity of the pituitary gland.
• It does not control other glands by acting through the pituitary gland; instead, it directly controls other glands or indirectly through the pituitary.