Exam 2 Review: Endocrine, Respiratory, Digestive, and Metabolic Systems

Chapter 16: The Endocrine System

Overview of Endocrine Glands and Hormones

The endocrine system is composed of glands that secrete hormones directly into the bloodstream to regulate various body functions.

• Hormone: Chemical messenger released by endocrine glands that affects target cells.

• Endocrine glands: Ductless glands that release hormones (e.g., pituitary, thyroid, adrenal).

• Exocrine glands: Glands with ducts that secrete substances onto epithelial surfaces (e.g., sweat glands).

Hormone Actions and Mechanisms

• Hormone effects: Can be stimulatory or inhibitory, affecting metabolism, growth, and homeostasis.

• Mechanisms: Hormones act via receptors on target cells, using second messengers (e.g., cAMP) or direct gene activation.

• Types of hormones: Amino acid-based (proteins, peptides, amines) and steroid hormones (derived from cholesterol).

Major Endocrine Glands and Hormones

• Anterior Pituitary gland: Releases growth hormone, TSH

• Posterior pituitary gland:, prolactin, ACTH, TSH, FSH, LH, and oxytocin.

• Thyroid gland: Produces thyroid hormones (T3, T4) and calcitonin.

• Parathyroid glands: Secrete parathyroid hormone (PTH) to regulate calcium balance.

• Adrenal glands: Cortex produces corticosteroids (cortisol, aldosterone); medulla produces catecholamines (epinephrine, norepinephrine).

• Pineal gland: Secretes melatonin, regulating circadian rhythms.

• Pancreas: Produces insulin and glucagon for blood glucose regulation.

Hormone Regulation

• Feedback mechanisms: Negative feedback is most common, maintaining homeostasis.

• Example: Blood glucose regulation by insulin and glucagon.

Chapter 22: The Respiratory System

Major Organs and Functions

The respiratory system provides oxygen to the body and removes carbon dioxide through ventilation and gas exchange.

• Major organs: Nose, pharynx, larynx, trachea, bronchi, lungs, alveoli.

• Function: Gas exchange, sound production, olfaction, and pH regulation.

Respiratory Processes

• Pulmonary ventilation: Movement of air into and out of the lungs (breathing).

• External respiration: Gas exchange between alveoli and blood.

• Transport of gases: Oxygen and carbon dioxide carried by blood.

• Internal respiration: Gas exchange between blood and tissues.

Respiratory Membrane and Gas Laws

• Respiratory membrane: Thin barrier for gas exchange in alveoli.

• Dalton’s Law: Total pressure of a gas mixture equals the sum of partial pressures of each gas.

• Henry’s Law: Amount of gas dissolved in a liquid is proportional to its partial pressure and solubility.

Control of Respiration

• Neural control: Medullary and pontine respiratory centers regulate breathing rhythm.

• Chemical control: Chemoreceptors respond to CO2, O2, and pH changes.

Chapter 23: The Digestive System

Digestive Processes and Organs

The digestive system breaks down food, absorbs nutrients, and eliminates waste.

• Major processes: Ingestion, propulsion, mechanical digestion, chemical digestion, absorption, defecation.

• Major organs: Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus.

• Accessory organs: Teeth, tongue, salivary glands, liver, gallbladder, pancreas.

Histology of the GI Tract

• Layers: Mucosa, submucosa, muscularis externa, serosa.

• Functions: Protection, secretion, absorption, movement of food.

Digestive Enzymes and Absorption

• Enzymes: Amylase (carbohydrates), proteases (proteins), lipases (fats).

• Absorption: Most nutrients absorbed in the small intestine; water and electrolytes in the large intestine.

Chapter 24: Nutrition, Metabolism, and Energy Balance

Basic Nutrients and Metabolic Pathways

Nutrition involves the intake of food and its utilization for energy, growth, and maintenance. Metabolism includes all chemical reactions in the body.

• Macronutrients: Carbohydrates, proteins, fats.

• Micronutrients: Vitamins, minerals.

• Metabolism: Catabolism (breakdown) and anabolism (synthesis) of molecules.

Carbohydrate Metabolism

• Glycolysis: Breakdown of glucose to pyruvate, producing ATP.

• Krebs cycle: Oxidation of acetyl-CoA to CO2 and ATP.

• Electron transport chain (ETC): Produces most ATP via oxidative phosphorylation.

• Overall equation for cellular respiration:

$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + 36-38 ATP$

Protein and Lipid Metabolism

• Protein metabolism: Deamination of amino acids, urea formation, and synthesis of new proteins.

• Lipid metabolism: Beta-oxidation of fatty acids, synthesis of triglycerides, cholesterol transport.

Energy Balance and Metabolic States

• Absorptive state: Nutrients are absorbed and stored.

• Postabsorptive state: Stored nutrients are mobilized for energy.

Summary Table: Major Metabolic Pathways

Pathway	Main Substrate	Major Products	Location
Glycolysis	Glucose	Pyruvate, ATP, NADH	Cytoplasm
Krebs Cycle	Acetyl-CoA	CO2, NADH, FADH2, ATP	Mitochondrial matrix
Electron Transport Chain	NADH, FADH2	ATP, H2O	Inner mitochondrial membrane
Beta-oxidation	Fatty acids	Acetyl-CoA, NADH, FADH2	Mitochondria

Additional info: This table summarizes the main metabolic pathways, their substrates, products, and cellular locations for efficient review.