Chemical Coordination and Integration

Key Concepts

Endocrine System and Hormones

Hormones are non-nutrient chemicals that act as intercellular messengers, produced in trace amounts by ductless (endocrine) glands. They provide coordination and integration for cellular functions that are not directly innervated by the neural system.

Major Endocrine Glands and Hypothalamus

Hypothalamus: The basal part of the forebrain; produces releasing (e.g., GnRH) and inhibiting (e.g., somatostatin) hormones that regulate the pituitary.

Pituitary Regulation The hypothalamus regulates the anterior pituitary through a portal circulatory system, whereas the posterior pituitary is under direct neural regulation from the hypothalamus.

Pituitary Gland:
- Anterior Pituitary: Secretes GH (growth), PRL (milk), TSH (thyroid), ACTH (adrenal), LH, FSH (gonads), and MSH (melanocytes).
- Posterior Pituitary: Stores and releases oxytocin and vasopressin (ADH).
Pineal Gland: Secretes melatonin, which regulates the 24-hour diurnal rhythm (sleep-wake cycle).
Thyroid Gland: Produces T3, T4 (regulate BMR and metabolism) and thyrocalcitonin (TCT, regulates blood calcium).
Parathyroid Glands: Secrete PTH, which increases blood Ca2+ levels (hypercalcemic).
Thymus: Secretes thymosins, which play a major role in the immune system (T-lymphocyte differentiation).
Adrenal Glands:
- Medulla: Secretes emergency hormones (Adrenaline, Noradrenaline).
- Cortex: Secretes corticoids like cortisol (carbohydrate metabolism) and aldosterone (electrolyte/water balance).
Pancreas (Composite Gland):
- Alpha cells: Secretes glucagon (increases blood sugar).
- Beta cells: Secretes insulin (decreases blood sugar).

Glucose Homeostasis Insulin and Glucagon are antagonistic hormones. Insulin decreases blood glucose (hypoglycemic), while Glucagon increases it (hyperglycemic), maintaining overall sugar levels.

Gonads:
- Testis: Produces androgens (e.g., testosterone) for male sexual development and spermatogenesis.
- Ovary: Produces estrogen (female characteristics) and progesterone (supports pregnancy).

Hormones from other organs

Heart: Atrial Natriuretic Factor (ANF) decreases blood pressure.
Kidney: Erythropoietin stimulates RBC production.
G-I Tract: Gastrin, secretin, CCK, and GIP regulate digestive juices.

Mechanism of Hormone Action

Hormones bind to specific proteins called hormone receptors:

Membrane-bound receptors: Used by protein/peptide hormones; they generate second messengers (e.g., cAMP) to regulate metabolism.

Second Messengers Water-soluble hormones (like proteins) cannot cross the cell membrane. They bind to surface receptors and trigger intracellular second messengers like cAMP, $IP_3$ , or $Ca^{2+}$ to carry out their effects.

Intracellular receptors: Used by steroid hormones and iodothyronines; they interact with the genome to regulate gene expression and chromosome function.

Activities (for understanding, not part of notes)

Create a summary table matching each endocrine gland with its primary hormones and their deficiency disorders.
Investigate the physiological changes that occur during the 'Fight or Flight' response.
Compare the mechanisms of action for a peptide hormone (e.g., insulin) and a steroid hormone (e.g., testosterone).

Key Concepts

Hypothalamus: The basal part of the forebrain; produces releasing (e.g., GnRH) and inhibiting (e.g., somatostatin) hormones that regulate the pituitary.

Pituitary Gland:

Anterior Pituitary: Secretes GH (growth), PRL (milk), TSH (thyroid), ACTH (adrenal), LH, FSH (gonads), and MSH (melanocytes).
Posterior Pituitary: Stores and releases oxytocin and vasopressin (ADH).

Pineal Gland: Secretes melatonin, which regulates the 24-hour diurnal rhythm (sleep-wake cycle).

Thyroid Gland: Produces T3, T4 (regulate BMR and metabolism) and thyrocalcitonin (TCT, regulates blood calcium).

Parathyroid Glands: Secrete PTH, which increases blood Ca2+ levels (hypercalcemic).

Thymus: Secretes thymosins, which play a major role in the immune system (T-lymphocyte differentiation).

Adrenal Glands:

Medulla: Secretes emergency hormones (Adrenaline, Noradrenaline).
Cortex: Secretes corticoids like cortisol (carbohydrate metabolism) and aldosterone (electrolyte/water balance).

Pancreas (Composite Gland):

Alpha cells: Secretes glucagon (increases blood sugar).
Beta cells: Secretes insulin (decreases blood sugar).

Gonads:

Testis: Produces androgens (e.g., testosterone) for male sexual development and spermatogenesis.
Ovary: Produces estrogen (female characteristics) and progesterone (supports pregnancy).

Heart: Atrial Natriuretic Factor (ANF) decreases blood pressure.

Kidney: Erythropoietin stimulates RBC production.

G-I Tract: Gastrin, secretin, CCK, and GIP regulate digestive juices.

Hormones bind to specific proteins called hormone receptors:

Membrane-bound receptors: Used by protein/peptide hormones; they generate second messengers (e.g., cAMP) to regulate metabolism.

Intracellular receptors: Used by steroid hormones and iodothyronines; they interact with the genome to regulate gene expression and chromosome function.

Activities (for understanding, not part of notes)

Create a summary table matching each endocrine gland with its primary hormones and their deficiency disorders.

Investigate the physiological changes that occur during the 'Fight or Flight' response.

Compare the mechanisms of action for a peptide hormone (e.g., insulin) and a steroid hormone (e.g., testosterone).

Chemical Coordination and Integration

Chemical Coordination and Integration

Key Concepts

Endocrine System and Hormones

Major Endocrine Glands and Hypothalamus

Hormones from other organs

Mechanism of Hormone Action

Activities (for understanding, not part of notes)

On this page

Chemical Coordination and Integration

Chemical Coordination and Integration

Key Concepts

Endocrine System and Hormones

Major Endocrine Glands and Hypothalamus

Hormones from other organs

Mechanism of Hormone Action

Activities (for understanding, not part of notes)

On this page