Glands, Enzymes, and Hormones

Glands

• Definition: Glands are specialized organs that secrete substances such as enzymes, hormones, or other fluids for specific functions.
• Types of Glands:
  1. Exocrine Glands:
     • Secrete substances through ducts onto surfaces or into cavities.
     • Examples: Salivary glands, sweat glands, pancreas (exocrine part).
  2. Endocrine Glands:
     • Ductless glands that release hormones directly into the bloodstream.
     • Examples: Pituitary gland, thyroid gland, adrenal gland.
  3. Mixed Glands:
     • Have both exocrine and endocrine functions.
     • Example: Pancreas.

Type	Secretion	Examples
Exocrine Glands	Enzymes, sweat, mucus	Salivary, Sweat glands
Endocrine Glands	Hormones	Thyroid, Pituitary
Mixed Glands	Enzymes and hormones	Pancreas

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Major Glands and Their Secretions

1. Pituitary Gland (Master Gland):

   • Located at the base of the brain.
   • Divided into:
     • Anterior Pituitary: Secretes growth hormone (GH), prolactin, and others.
     • Posterior Pituitary: Secretes oxytocin and antidiuretic hormone (ADH).

2. Thyroid Gland:

   • Located in the neck.
   • Produces thyroxine (T4) and triiodothyronine (T3), which regulate metabolism.

3. Adrenal Glands:

   • Located above the kidneys.
   • Divided into:
     • Cortex: Secretes cortisol, aldosterone.
     • Medulla: Produces adrenaline (epinephrine) and noradrenaline.

4. Pancreas:

   • Functions as both an endocrine and exocrine gland.
   • Secretes:
     • Insulin: Lowers blood glucose levels.
     • Glucagon: Raises blood glucose levels.
     • Digestive enzymes like amylase, lipase.

5. Gonads:

   • Testes (males): Produce testosterone.
   • Ovaries (females): Produce estrogen and progesterone.

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Enzymes

• Definition: Enzymes are biological catalysts that speed up chemical reactions in the body without being consumed.
• Characteristics:
  1. Specific to substrates.
  2. Work best at optimal temperature and pH.
  3. Activity can be inhibited or enhanced.

Enzyme	Source	Function	Example Reaction
Amylase	Salivary glands, pancreas	Breaks down starch into maltose	Starch → Maltose
Lipase	Pancreas	Breaks down fats into fatty acids and glycerol	Lipids → Fatty acids + Glycerol
Protease (Trypsin)	Pancreas	Breaks down proteins into peptides	Proteins → Peptides
Lactase	Small intestine	Breaks down lactose into glucose and galactose	Lactose → Glucose + Galactose

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Hormones

• Definition: Hormones are chemical messengers secreted by endocrine glands directly into the bloodstream to regulate body functions.
• Types of Hormones:
  1. Peptide Hormones:
     • Made of amino acids.
     • Examples: Insulin, glucagon, oxytocin.
  2. Steroid Hormones:
     • Derived from cholesterol.
     • Examples: Testosterone, estrogen, cortisol.
  3. Amine Hormones:
     • Derived from amino acids like tyrosine.
     • Examples: Adrenaline, thyroxine.

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Major Hormones and Their Functions

1. Pituitary Gland Hormones:
   • Anterior Pituitary:
     • Growth Hormone (GH): Stimulates growth and cell regeneration.
     • Prolactin: Promotes milk production.
     • Adrenocorticotropic Hormone (ACTH): Stimulates adrenal cortex to release cortisol.
     • Thyroid-Stimulating Hormone (TSH): Stimulates thyroid gland to produce thyroxine.
     • Gonadotropins (FSH and LH):
       • FSH: Stimulates gamete production.
       • LH: Stimulates ovulation in females, testosterone production in males.
   • Posterior Pituitary:
     • Oxytocin: Stimulates uterine contractions during childbirth and milk ejection.
     • Antidiuretic Hormone (ADH): Promotes water reabsorption in the kidneys.

Hormone	Source	Function
Growth Hormone (GH)	Anterior Pituitary	Stimulates growth
Prolactin	Anterior Pituitary	Milk production
Oxytocin	Posterior Pituitary	Uterine contraction, milk ejection
ADH	Posterior Pituitary	Water reabsorption

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2. Thyroid Gland Hormones:

   • Thyroxine (T4) and Triiodothyronine (T3):
     • Regulate metabolism, energy production, and growth.
   • Calcitonin:
     • Reduces blood calcium levels by promoting calcium storage in bones.

3. Parathyroid Gland Hormone:

   • Parathyroid Hormone (PTH):
     • Increases blood calcium levels by stimulating bone resorption and calcium absorption in intestines.

4. Adrenal Gland Hormones:

   • Adrenal Cortex:
     • Cortisol: Manages stress, regulates metabolism, and reduces inflammation.
     • Aldosterone: Regulates sodium and potassium balance.
   • Adrenal Medulla:
     • Adrenaline (Epinephrine): Prepares the body for fight-or-flight response.
     • Noradrenaline (Norepinephrine): Increases heart rate and blood pressure.

Hormone	Source	Function
Thyroxine (T4)	Thyroid Gland	Regulates metabolism
Cortisol	Adrenal Cortex	Manages stress, reduces inflammation
Adrenaline	Adrenal Medulla	Fight-or-flight response
PTH	Parathyroid Gland	Increases blood calcium levels

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5. Pancreatic Hormones:

   • Insulin:
     • Lowers blood glucose levels by promoting glucose uptake by cells.
   • Glucagon:
     • Raises blood glucose levels by stimulating glycogen breakdown in the liver.

6. Reproductive Hormones:

   • Testosterone (Testes):
     • Develops male secondary sexual characteristics and promotes sperm production.
   • Estrogen (Ovaries):
     • Develops female secondary sexual characteristics and regulates menstrual cycle.
   • Progesterone (Ovaries):
     • Prepares the uterus for pregnancy and supports early pregnancy.

Hormone	Source	Function
Insulin	Pancreas	Lowers blood glucose
Glucagon	Pancreas	Raises blood glucose
Testosterone	Testes	Male sexual characteristics
Estrogen	Ovaries	Female sexual characteristics
Progesterone	Ovaries	Maintains pregnancy

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Enzyme Action

1. Mechanism of Enzyme Action:

   • Lock and Key Model:
     • The enzyme's active site has a specific shape that fits the substrate exactly.
   • Induced Fit Model:
     • The enzyme adjusts its shape slightly to fit the substrate more snugly.

2. Factors Affecting Enzyme Activity:

   • Temperature:
     • Enzymes have an optimal temperature; high temperatures can denature enzymes.
   • pH:
     • Enzymes have an optimal pH range (e.g., pepsin works best in acidic pH).
   • Substrate Concentration:
     • Higher substrate concentration increases enzyme activity up to a saturation point.
   • Inhibitors:
     • Competitive Inhibitors: Compete with the substrate for the active site.
     • Non-Competitive Inhibitors: Bind elsewhere on the enzyme, altering its shape.

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Feedback Mechanism in Hormonal Regulation

1. Negative Feedback:
   • Ensures hormone levels remain balanced.
   • Example: Regulation of blood glucose by insulin and glucagon.
     • High glucose → Insulin secretion → Glucose decreases → Insulin secretion stops.
2. Positive Feedback:
   • Amplifies a process until a specific outcome is achieved.
   • Example: Oxytocin during childbirth.
     • Uterine contraction → Oxytocin release → Stronger contraction → Cycle continues until delivery.

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Disorders Related to Glands, Enzymes, and Hormones

1. Hormonal Disorders:

   • Hyperthyroidism:

     • Cause: Excess thyroid hormone production.
     • Symptoms: Weight loss, increased appetite, sweating, rapid heartbeat.
     • Treatment: Antithyroid drugs, radioactive iodine therapy.

   • Hypothyroidism:

     • Cause: Insufficient thyroid hormone production.
     • Symptoms: Fatigue, weight gain, cold intolerance.
     • Treatment: Thyroid hormone replacement.

   • Diabetes Mellitus:

     • Cause: Insufficient insulin production or utilization.
     • Types:
       • Type 1: Autoimmune destruction of insulin-producing cells.
       • Type 2: Insulin resistance.
     • Symptoms: High blood sugar, frequent urination, excessive thirst.
     • Treatment: Insulin injections (Type 1), oral medications (Type 2).

2. Enzyme Disorders:

   • Lactose Intolerance:
     • Cause: Deficiency of lactase enzyme.
     • Symptoms: Bloating, diarrhea, abdominal pain after consuming dairy.
     • Treatment: Lactase supplements, avoiding lactose-rich foods.
   • Phenylketonuria (PKU):
     • Cause: Deficiency of phenylalanine hydroxylase enzyme.
     • Symptoms: Intellectual disability, developmental delay.
     • Treatment: Low-phenylalanine diet.

Disorder	Cause	Symptoms	Treatment
Hyperthyroidism	Excess thyroid hormone	Weight loss, sweating	Antithyroid drugs
Hypothyroidism	Low thyroid hormone	Fatigue, weight gain	Thyroid replacement therapy
Diabetes Mellitus	Insulin issues	High blood sugar	Insulin, oral drugs
Lactose Intolerance	Lack of lactase	Bloating, diarrhea	Lactase supplements
Phenylketonuria (PKU)	Enzyme deficiency	Developmental delay	Dietary management

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Importance of Glands, Enzymes, and Hormones

1. Glands:
   • Coordinate and regulate body functions through secretion of enzymes and hormones.
2. Enzymes:
   • Catalyze metabolic reactions, ensuring efficiency and speed in bodily processes.
3. Hormones:
   • Act as messengers to maintain homeostasis, support growth, and respond to environmental changes.

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