BIO201 – Topic 19: The Human Endocrine and Hormonal Coordination System
Course Code: BIO 201
Course Name: Human Biology
© Lesuyai Organic Guides 2025
(Original | Educational | Professional | Plagiarism-Free | 2025 Edition | A4 Format)
19.1 Introduction
The endocrine system is a chemical communication system that regulates long-term processes
such as growth, metabolism, reproduction, and homeostasis.
19.2 Definition of Endocrine System
The endocrine system consists of ductless glands that secrete hormones directly into the
bloodstream to influence the activity of target organs.
19.3 Major Endocrine Glands and Their Hormones
Pituitary gland – GH, TSH, FSH, LH, ADH, Prolactin
Thyroid gland – Thyroxine (T3/T4), Calcitonin
Parathyroid glands – Parathyroid hormone (PTH)
Pancreas – Insulin, Glucagon
Adrenal glands – Adrenaline, Cortisol, Aldosterone
Gonads – Testosterone, Estrogen, Progesterone
19.4 Mechanism of Hormone Action
Hormones act through:
1. Second-messenger systems (peptide hormones)
2. Direct gene activation (steroid hormones)
19.5 Interaction Between Endocrine and Nervous Systems
The hypothalamus links the two systems by producing releasing and inhibiting factors that control
the pituitary gland.
19.6 Effects of Hormonal Imbalance
Hypothyroidism – low thyroxine
Hyperthyroidism – excess thyroxine
Diabetes mellitus – low insulin or resistance
Gigantism/dwarfism – GH imbalance
19.7 Regulation of Hormone Secretion
Primarily through negative feedback loops to maintain homeostasis.
19.8 Common Disorders of the Endocrine System
Goitre
Cushing’s syndrome
Addison’s disease
Diabetes mellitus
Hyperparathyroidism
19.9 Summary
The endocrine system uses hormones to coordinate body functions, maintain homeostasis, and
support growth and reproduction.
EXAM SECTION – STRUCTURED QUESTIONS WITH ANSWERS
1. Define a hormone.
Answer: A hormone is a chemical messenger produced by endocrine glands and transported
through the bloodstream to target organs.
2. State two differences between endocrine and exocrine glands.
Answer: Endocrine glands are ductless; exocrine glands have ducts. Endocrine glands release
hormones into blood; exocrine glands release substances onto surfaces.
Course Code: BIO 201
Course Name: Human Biology
© Lesuyai Organic Guides 2025
(Original | Educational | Professional | Plagiarism-Free | 2025 Edition | A4 Format)
19.1 Introduction
The endocrine system is a chemical communication system that regulates long-term processes
such as growth, metabolism, reproduction, and homeostasis.
19.2 Definition of Endocrine System
The endocrine system consists of ductless glands that secrete hormones directly into the
bloodstream to influence the activity of target organs.
19.3 Major Endocrine Glands and Their Hormones
Pituitary gland – GH, TSH, FSH, LH, ADH, Prolactin
Thyroid gland – Thyroxine (T3/T4), Calcitonin
Parathyroid glands – Parathyroid hormone (PTH)
Pancreas – Insulin, Glucagon
Adrenal glands – Adrenaline, Cortisol, Aldosterone
Gonads – Testosterone, Estrogen, Progesterone
19.4 Mechanism of Hormone Action
Hormones act through:
1. Second-messenger systems (peptide hormones)
2. Direct gene activation (steroid hormones)
19.5 Interaction Between Endocrine and Nervous Systems
The hypothalamus links the two systems by producing releasing and inhibiting factors that control
the pituitary gland.
19.6 Effects of Hormonal Imbalance
Hypothyroidism – low thyroxine
Hyperthyroidism – excess thyroxine
Diabetes mellitus – low insulin or resistance
Gigantism/dwarfism – GH imbalance
19.7 Regulation of Hormone Secretion
Primarily through negative feedback loops to maintain homeostasis.
19.8 Common Disorders of the Endocrine System
Goitre
Cushing’s syndrome
Addison’s disease
Diabetes mellitus
Hyperparathyroidism
19.9 Summary
The endocrine system uses hormones to coordinate body functions, maintain homeostasis, and
support growth and reproduction.
EXAM SECTION – STRUCTURED QUESTIONS WITH ANSWERS
1. Define a hormone.
Answer: A hormone is a chemical messenger produced by endocrine glands and transported
through the bloodstream to target organs.
2. State two differences between endocrine and exocrine glands.
Answer: Endocrine glands are ductless; exocrine glands have ducts. Endocrine glands release
hormones into blood; exocrine glands release substances onto surfaces.
