Endocrine System Overview Quiz

Endocrine System Overview

• The endocrine system comprises glands and tissues secreting hormones, which are chemicals influencing other glands/tissues.
• Endocrine glands lack ducts, releasing hormones directly into tissue fluid.
• The endocrine system, like the nervous system, participates in homeostasis.
• Endocrine hormones travel via blood, causing slower but often longer-lasting responses compared to the nervous system.
• Hormone production is regulated by negative feedback and antagonistic hormones.

Hormone Action

• Hormones are chemical signals, communicating between cells, body parts, or even individuals.
• Two main hormone categories exist:
  • Peptide hormones: These comprise peptides, proteins, glycoproteins, or modified amino acids.
  • Steroid hormones: These have a common four-carbon ring structure but differ in side chains.

Pheromones

• Pheromones are chemical signals influencing the behavior of individuals within the same species.

Hypothalamus and Pituitary Gland

• The hypothalamus regulates internal environment through the autonomic nervous system (e.g., heart rate, blood pressure).
• It also modulates gland secretions, including those of the pituitary gland.
• Posterior pituitary: Stores and releases hormones (ADH and oxytocin) produced by the hypothalamus.
  • ADH (antidiuretic hormone) increases water reabsorption in kidneys when blood is concentrated.
  • Oxytocin stimulates uterine contractions during childbirth and milk release during breastfeeding (positive feedback).
• Anterior pituitary: Controlled by hypothalamic-releasing and inhibiting hormones, which in turn stimulate the anterior pituitary to produce hormones like:
  • Thyroid-stimulating hormone
  • Adrenocorticotropic hormone
  • Gonadotropic hormones
  • Prolactin
  • Melanocyte-stimulating hormone
  • Growth hormone

Thyroid and Parathyroid Glands

• Thyroid gland: Located in the neck; produces hormones affecting metabolic rate and blood calcium levels.
• Parathyroid glands: Embedded in the thyroid; release parathyroid hormone, which decreases blood phosphate and increases blood calcium levels.

Adrenal Glands

• Adrenal glands: Located atop the kidneys.
• Adrenal medulla: Produces epinephrine and norepinephrine, rapidly responding to stress.
• Adrenal cortex: Releases hormones for longer-term stress responses.
  • Glucocorticoids (e.g., cortisol): Increase blood glucose and counteract inflammation.
  • Mineralocorticoids (e.g., aldosterone): Regulates blood volume and blood pressure by targeting the kidneys.

Pancreas

• Pancreas has exocrine tissue (secretes digestive juices) and endocrine islets (produce hormones).
• Pancreatic islets: Secrete insulin and glucagon (blood sugar regulation) and somatostatin (growth hormone inhibitor).

Other Endocrine Glands

• Gonads: Produce sex hormones.

  • Testes (males): Produce sperm and androgens (e.g., testosterone).
  • Ovaries (females): Produce eggs and female sex hormones (e.g., estrogen, progesterone).
  • Hypothalamus and pituitary gland control gonadal hormone secretion (puberty and secondary sex characteristics)

• Thymus: Secretes thymosins, aiding in T lymphocyte differentiation.

• Pineal gland: Produces melatonin, influencing the sleep-wake cycle.

Hormones from Other Tissues

• Some organs (not typically considered endocrine glands) still secrete hormones.
  • Leptin: Produced by adipose tissue; signals satiety (fullness).
  • Growth factors: Produced by various organs and cells.