Overview
This lecture introduces the endocrine system, explains how it communicates via hormones compared to the nervous system's neurotransmitters, explores the link between hormones and behavior, and describes the major endocrine glands and their functions.
Nervous System vs. Endocrine System Communication
- Neurons use electrical impulses and neurotransmitters for fast, targeted cell-to-cell communication.
- Neurotransmitters act within milliseconds and only affect cells directly connected by nerve tracts.
- Endocrine glands secrete hormones into the bloodstream, broadcasting signals more slowly and throughout the body.
- Hormonal effects are slower (seconds to hours), last longer, and affect any cell with the corresponding hormone receptor.
Hormones and Behavior Interactions
- Behavioral endocrinology studies the two-way relationship between hormones and behavior.
- Hormones can influence behaviors like aggression, mating, parenting, and stress coping.
- Behaviors such as stress and social interaction can also alter hormone levels.
- Examples of behavior-influencing hormones: testosterone, estradiol, progesterone, cortisol, oxytocin, vasopressin, prolactin, and leptin.
Introduction to the Endocrine System
- The endocrine system consists of glands that release hormones directly into the blood.
- Endocrine hormones act on target cells throughout the body and can have widespread, long-lasting effects.
- Exocrine glands release substances through ducts to local body surfaces (e.g., sweat glands).
Major Endocrine Glands and Their Functions
Endocrine Glands in the Brain
- Pituitary gland: Controlled by the hypothalamus, called the "master gland", has anterior (produces own hormones) and posterior (stores/releases hypothalamus hormones) lobes.
- Hypothalamus: Regulates pituitary activity via the infundibulum.
- Pineal gland: Produces melatonin to regulate sleep-wake cycles.
Endocrine Glands in the Body
- Thyroid gland: Secretes thyroxine to control metabolism and protein synthesis.
- Thymus gland: Site for T cell maturation, important for immune response.
- Pancreas: Releases insulin and glucagon to regulate blood glucose; also secretes digestive enzymes.
- Adrenal glands: Secrete epinephrine (adrenaline) for stress response, aldosterone for mineral balance, and cortisol for stress.
- Gonads (ovaries/testes): Secrete sex hormones (testosterone, estrogen) that control sexual maturation and gamete production.
Key Terms & Definitions
- Neurotransmitter — Chemical messenger used by neurons for rapid communication.
- Hormone — Chemical messenger released by endocrine glands into the bloodstream.
- Endocrine gland — Gland that secretes hormones directly into the blood.
- Exocrine gland — Gland that releases substances via ducts to body surfaces.
- Receptor — Protein on a cell that binds specific hormones or neurotransmitters.
- Target cell — Cell with receptors for a specific hormone.
- Tropic hormone — Hormone that controls the activity of other endocrine glands.
Action Items / Next Steps
- Review the functions and locations of each major endocrine gland.
- Prepare to identify and describe at least three endocrine glands for quizzes or exams.
- Read upcoming chapters on the role of hormones in behavior and development.