CHAPTER 19- CHEMICAL COORDINATION AND INTEGRATION

Neural and Endocrine Coordination

The neural system coordinates quickly but effects are short-lived.
Neural coordination doesn’t reach all body cells, so continuous regulation is needed, which is done by hormones.
The neural system and endocrine system together manage body functions.

Endocrine Glands and Hormones

Endocrine glands are ductless and secrete hormones directly into the blood.
Hormones act as chemical messengers between cells and are produced in small amounts.
Invertebrates have simpler endocrine systems, while vertebrates, including humans, have complex ones.

Human Endocrine System

Includes major glands like the pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus, and gonads (testes in males, ovaries in females).
Other organs like the heart, kidney, liver, and gastrointestinal tract also produce hormones.

Key Endocrine Glands and Their Functions

Hypothalamus

Located in the forebrain and controls many body functions.
Produces releasing hormones (stimulate pituitary hormones) and inhibiting hormones (suppress pituitary hormones).
- Example: GnRH stimulates gonadotrophins, while somatostatin inhibits growth hormone.
Hormones travel to the pituitary through a portal system or direct neural regulation.

Pituitary Gland

Found in a bony cavity, connected to the hypothalamus.
Divided into:
- Adenohypophysis (anterior pituitary): Produces hormones like:
  - Growth hormone (GH)
  - Prolactin (PRL)
  - Thyroid-stimulating hormone (TSH)
  - Adrenocorticotrophic hormone (ACTH)
  - Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH)
- Neurohypophysis (posterior pituitary): Stores and releases:
  - Oxytocin (stimulates uterine contractions and milk ejection)
  - Vasopressin/ADH (reduces water loss through urine).
Disorders:
- Excess GH: Gigantism or Acromegaly.
- Low GH: Dwarfism.
- ADH deficiency: Diabetes insipidus (water loss, dehydration).

Pineal Gland

Found in the brain; secretes melatonin.
Regulates the body’s sleep-wake cycle, body temperature, and other functions.

Thyroid Gland

Located in the neck with two lobes.
Produces:
- Thyroxine (T4) and Triiodothyronine (T3): Regulate metabolism, RBC production, and electrolyte balance.
- Calcitonin (TCT): Controls blood calcium levels.
Disorders:
- Hypothyroidism: Goiter, stunted growth (cretinism), and irregular menstruation.
- Hyperthyroidism: Graves’ disease (weight loss, protruding eyes).

Parathyroid Gland

Four glands located on the thyroid’s backside.
Produces parathyroid hormone (PTH), which:
- Increases blood calcium by acting on bones, kidneys, and digestive system.
- Works with calcitonin for calcium balance.

Thymus

Location: Between lungs, behind the sternum, near the aorta.
Role: Develops the immune system by producing thymosins.
Functions of Thymosins:
- Helps T-lymphocytes mature for cell-mediated immunity.
- Encourages production of antibodies for humoral immunity.
Changes with Age: Shrinks in older people, reducing thymosin production and weakening immunity.

Adrenal Gland

Location: One gland on top of each kidney.
Structure:
- Adrenal medulla (center): Produces adrenaline and noradrenaline (catecholamines).
  - Functions: Increase alertness, heart rate, breathing, and blood sugar (fight-or-flight response).
- Adrenal cortex (outer layer): Produces corticoids, divided into:
  - Glucocorticoids (e.g., cortisol):
    - Regulate carbohydrate, protein, and fat metabolism.
    - Anti-inflammatory and immune-suppressing effects.
  - Mineralocorticoids (e.g., aldosterone):
    - Controls water and salt balance, blood pressure.
  - Androgenic steroids:
    - Influence growth of body hair during puberty.

Pancreas

Type: Mixed gland (both endocrine and exocrine).
Endocrine Function: The Islets of Langerhans contain:
- α-cells (secrete glucagon):
  - Increases blood sugar (hyperglycemia) by breaking down glycogen and creating glucose.
- β-cells (secrete insulin):
  - Decreases blood sugar (hypoglycemia) by enhancing glucose uptake and storage as glycogen.
Disorder: Prolonged high blood sugar causes diabetes mellitus, treated with insulin therapy.

Testis

Location: In scrotum (outside the abdomen).
Dual Function:
- Primary sex organ: Produces sperm.
- Endocrine gland: Produces androgens (e.g., testosterone).
  - Functions:
    - Develops male sexual organs and secondary features (e.g., facial hair, deep voice).
    - Promotes sperm production (spermatogenesis).
    - Affects male behavior (libido) and metabolism.

Ovary

Location: In the abdomen (pair in females).
Dual Function:
- Produces ova (eggs).
- Produces hormones (estrogen and progesterone):
  - Estrogen:
    - Develops female sexual organs, secondary features (e.g., high-pitched voice), and mammary glands.
    - Stimulates follicle growth and regulates sexual behavior.
  - Progesterone:
    - Maintains pregnancy.
    - Stimulates milk formation and secretion in mammary glands.

Hormones of Heart, Kidney, and Gastrointestinal Tract

Heart:
- Hormone: Atrial Natriuretic Factor (ANF).
- Function: Lowers blood pressure by dilating blood vessels when blood pressure is high.
Kidney:
- Hormone: Erythropoietin.
- Function: Stimulates the production of red blood cells (RBCs), a process called erythropoiesis.
Gastrointestinal Tract:
- Hormones:
  - Gastrin: Stimulates the gastric glands to secrete hydrochloric acid and pepsinogen.
  - Secretin: Stimulates the pancreas to release water and bicarbonate.
  - Cholecystokinin (CCK): Stimulates the pancreas to release enzymes and the gall bladder to release bile.
  - Gastric Inhibitory Peptide (GIP): Inhibits gastric secretion and motility.
Growth Factors:
- Secreted by non-endocrine tissues.
- Essential for tissue growth, repair, and regeneration.

Mechanism of Hormone Action

Hormone Receptors:
- Membrane-bound receptors: Located on the cell membrane.
- Intracellular receptors: Found inside cells, mainly in the nucleus.
Process:
- Hormones bind to specific receptors to form a hormone-receptor complex.
- This triggers biochemical changes in the target tissue, regulating metabolism and physiological functions.
Types of Hormones (Based on Chemical Nature):
- Peptides/Proteins: Insulin, glucagon, pituitary, and hypothalamic hormones.
- Steroids: Cortisol, testosterone, estrogen, progesterone.
- Iodothyronines: Thyroid hormones.
- Amino Acid Derivatives: Epinephrine.
Action:
- Membrane-bound receptors: Activate second messengers (e.g., cyclic AMP, IP3, Ca++) to regulate metabolism.
- Intracellular receptors: Influence gene expression and chromosome functions, affecting development and physiology.

Summary

Hormones coordinate body functions, including metabolism, growth, and organ activities.
Apart from endocrine glands, organs like the heart, kidneys, and gastrointestinal tract also produce hormones.
Hormones act by binding to specific receptors, causing physiological effects.
Hormones can be peptides, steroids, iodothyronines, or amino acid derivatives.

These all are the notes of chapter 19. And important questions are below HERE. *#THANKS FOR VISITING, VISIT AGAIN#* 😊

1. What is the role of the neural system in the body?

Answer: The neural system coordinates body functions quickly by transmitting electrical signals. However, its effects are short-lived and do not reach all cells in the body.

2. Why do we need hormones for body coordination?

Answer: Since the neural system doesn’t reach all body cells and has short-lived effects, hormones are needed for continuous regulation. They act as chemical messengers that help maintain long-term coordination across the body.

3. What are endocrine glands and how do they work?

Answer: Endocrine glands are ductless glands that secrete hormones directly into the bloodstream. These hormones carry messages to different body cells and are produced in small amounts.

4. How does the endocrine system differ in invertebrates and vertebrates?

Answer: Invertebrates have simpler endocrine systems, while vertebrates, including humans, have more complex systems with multiple glands and hormones.

5. Which glands are part of the human endocrine system?

Answer: The human endocrine system includes the pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus, and gonads (testes in males, ovaries in females). Other organs like the heart, kidneys, liver, and gastrointestinal tract also produce hormones.

6. What is the function of the hypothalamus?

Answer: The hypothalamus controls many body functions and produces hormones that either stimulate or inhibit the release of hormones from the pituitary gland. For example, it produces GnRH to stimulate gonadotrophins and somatostatin to inhibit growth hormone.

7. What hormones are produced by the pituitary gland?

Answer: The pituitary gland has two parts:

Anterior Pituitary produces hormones like Growth Hormone (GH), Prolactin (PRL), Thyroid-stimulating Hormone (TSH), and more.
Posterior Pituitary stores and releases Oxytocin (for uterine contractions and milk release) and Vasopressin/ADH (for water balance).

8. What is the role of the pineal gland?

Answer: The pineal gland produces melatonin, which helps regulate the sleep-wake cycle and other biological rhythms, including body temperature.

9. What does the thyroid gland do?

Answer: The thyroid gland produces Thyroxine (T4) and Triiodothyronine (T3) which regulate metabolism, red blood cell production, and electrolyte balance. It also produces Calcitonin, which helps control blood calcium levels.

10. What is the function of the parathyroid gland?

Answer: The parathyroid glands produce Parathyroid Hormone (PTH), which increases blood calcium levels by acting on bones, kidneys, and the digestive system. It works with Calcitonin to balance calcium levels in the body.

11. What does the thymus gland do?

Answer: The thymus gland is important for developing the immune system. It produces thymosins, which help T-lymphocytes mature and assist in immune responses like the production of antibodies.

12. What is the function of the adrenal glands?

Answer: The adrenal glands have two parts:

Adrenal Medulla produces adrenaline and noradrenaline, which prepare the body for the fight-or-flight response (increased heart rate, breathing, and blood sugar).
Adrenal Cortex produces hormones like cortisol (which regulates metabolism) and aldosterone (which controls salt and water balance).

13. What is the role of the pancreas in the endocrine system?

Answer: The pancreas has both endocrine and exocrine functions. The Islets of Langerhans produce hormones:

Alpha cells produce glucagon to increase blood sugar levels.
Beta cells produce insulin to decrease blood sugar levels.

14. What hormones do the testes and ovaries produce?

Answer:

The testes produce testosterone, which is responsible for male sexual characteristics and sperm production.
The ovaries produce estrogen (for female sexual characteristics and menstrual cycle regulation) and progesterone (to maintain pregnancy and stimulate milk production).

15. What hormones are produced by the heart and kidneys?