Grade 9 · Ions and Our Health · Ionic Compounds and Health
Ions in the Human Body
Electrolytes, nerve signals and why sports drinks exist.
Learning objectives
- Name key electrolytes in the human body.
- Explain the role of ions in nerve and muscle function.
- Evaluate claims made about electrolyte drinks.
NGSS alignment
MS-LS1-3
Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells.
MS-PS1-1
Develop models to describe the atomic composition of simple molecules and extended structures.
HS-LS1-3
Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.
MYP criteria
- Criterion D — Reflecting on the Impacts of Science
ENGAGE
Why can a small electric signal move your muscles?
Think about it
Your nerves send signals using charged particles, not wires. Which particles, and where do they come from?
EXPLAIN
Electrolytes at work
Sodium (Na+), potassium (K+), calcium (Ca2+) and chloride (Cl-) ions are called electrolytes. Cells pump them across membranes to create tiny voltage differences.
- Nerve impulses: rapid movement of Na+ into a cell and K+ out of it.
- Muscle contraction: Ca2+ released inside muscle cells triggers contraction.
- Hydration: ion balance controls how water moves between cells and blood.
Criterion D thinking
Sports drinks replace ions lost in sweat, but most are also high in sugar. Evaluating them means weighing evidence, marketing claims and health impacts together.
Practice questions
0/1 correct
Level 1
Which pair of ions is most directly involved in transmitting nerve impulses?
MYP criterion tasks
Level 4 · Criterion D
A sports drink advertises that it "replaces vital electrolytes". Evaluate this claim for a student who has just walked home from school.
Reflect & track
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