Cell Specialisation and Body System Functions

Specialisation of Cells

To allow cells to perform specific functions efficiently. For example: Muscle cells contract for movement. Neurons transmit electrical signals. Red blood cells transport oxygen.

Organisation of Biological Systems

Cells → form Tissues (e.g., muscle, epithelial); Tissues → form Organs (e.g., heart, liver); Organs → form Organ Systems (e.g., digestive, endocrine); Systems work together for survival and homeostasis.

Overall Digestive Function

To break down food into absorbable nutrients and eliminate undigested waste.

Digestive System Organs and Functions

Mouth: Mechanical digestion (teeth), chemical digestion (saliva); Esophagus: Transports food to stomach via peristalsis; Stomach: Churns food; secretes acid and enzymes; Small intestine: Major site of nutrient absorption; Liver: Produces bile to emulsify fats; Gallbladder: Stores and releases bile; Pancreas: Secretes digestive enzymes and bicarbonate; Large intestine: Absorbs water and forms feces; Rectum/Anus: Stores and eliminates feces.

Endocrine System Overview

A system of glands that secrete hormones to regulate body processes like metabolism, growth, and homeostasis.

Major Endocrine Glands and Their Hormones

Pituitary gland: 'Master gland', regulates other glands; Hypothalamus: Links nervous and endocrine systems, controls pituitary; Thyroid: Produces thyroxine (metabolism); Parathyroid: Regulates calcium levels; Pancreas: Produces insulin and glucagon for glucose regulation; Adrenal glands: Secrete adrenaline (stress response) and cortisol; Ovaries/Testes: Produce sex hormones (estrogen, testosterone).

Excretory System Function

Removes metabolic waste and maintains water, salt, and pH balance.

Kidneys

Filter blood, remove urea, regulate water/salt balance

Ureters

Transport urine from kidneys to bladder

Bladder

Stores urine

Urethra

Releases urine from the body

Skin

Excretes salt and water via sweat

Lungs

Excrete carbon dioxide

Homeostasis

Maintenance of internal balance using feedback loops

Negative feedback

Reverses a change (e.g., blood sugar)

Positive feedback

Enhances a change (e.g., childbirth)

Body Temperature Regulation

Involves thermoreceptors, hypothalamus, and effectors like sweating and shivering

Blood Glucose Regulation

Involves pancreatic cells, insulin, and glucagon to maintain blood sugar levels

Water Balance Regulation

Maintained by hypothalamus and kidneys via ADH in response to dehydration or excess water

Type 1 Diabetes

Autoimmune destruction of insulin-producing pancreatic cells → blood glucose remains high

Hypoglycaemia

Abnormally low blood glucose caused by too much insulin, not eating, or overexertion

Symptoms of Hypoglycaemia

Confusion, tremors, sweating, weakness, dizziness, fainting

Hyperthyroidism

Overproduction of thyroid hormone → increased metabolism, heat production, heart rate

Symptoms of Hyperthyroidism

Weight loss, heat intolerance, anxiety, fatigue, palpitations, goiter (enlarged thyroid)