Quick answer: A reflex action is a sudden, involuntary and automatic response to a stimulus, such as pulling your foot off a sharp pin; it is often controlled by the spinal cord through a reflex arc, without thinking. Walking is a voluntary action that we decide to do; it is started by the forebrain (cerebrum), and its precision, posture and balance are controlled by the cerebellum in the hindbrain.
Reflex action
A reflex action is a quick, automatic response to a stimulus that happens without conscious thought.
- Example: jerking your foot away after stepping on a drawing pin, or pulling your hand away from a hot object.
- Purpose: to protect the body from harm quickly.
- Control: many reflexes, like these, are controlled by the spinal cord through a reflex arc. The brain receives the information too, but the response happens before you consciously think about it.
The reflex arc:
| Step | Part | Role |
|---|---|---|
| 1 | Receptor (in the skin) | Detects the stimulus |
| 2 | Sensory neuron | Carries the message to the spinal cord |
| 3 | Relay neuron (in the spinal cord) | Passes the message on |
| 4 | Motor neuron | Carries the message to the muscle |
| 5 | Effector (muscle) | Moves the foot or hand away |
Note: Not all reflexes pass only through the spinal cord. Some, such as blinking when something comes near the eye, are controlled by the brain. They are still involuntary.
Walking
Walking is a voluntary action: we decide when to walk, where to go and how fast.
- The forebrain (cerebrum) is where we think and decide; it starts the voluntary movement.
- The cerebellum, in the hindbrain, controls the precision of voluntary movements and maintains posture and balance of the body. Walking in a straight line and riding a bicycle depend on it.
- Messages travel from the brain through the spinal cord and nerves to the leg muscles.
- Walking is a learned skill: babies have to practise to stand, balance and walk.
Reflex action vs walking
| Basis | Reflex action | Walking |
|---|---|---|
| Type | Involuntary, automatic | Voluntary, under our control |
| Main control | Often the spinal cord (reflex arc) | Forebrain starts it; cerebellum coordinates balance and precision |
| Started by | A sudden external stimulus | Our own decision |
| Thinking | No conscious thinking | Involves decision and continuous adjustment |
| Speed | Very fast (a fraction of a second) | Slower, rhythmic |
| Learned or inborn | Inborn | Learned through practice |
Exam tips
- The key words are involuntary for reflex action and voluntary for walking.
- Mention the control centres: spinal cord for a typical reflex; cerebrum and cerebellum for walking.
- Give one example of a reflex action with the reflex arc.
- A two-column table with four or five points is the best format for a "difference between" question.
Common mistakes
- Saying walking is a reflex action. It is voluntary.
- Saying reflex actions are controlled by the cerebellum. Typical withdrawal reflexes are controlled by the spinal cord.
- Writing that the brain plays no part in walking. The brain starts and coordinates it.
- Claiming reflexes take "a millisecond". They are very fast, but usually take a few tens of milliseconds.
Frequently Asked Questions
What is the difference between a reflex action and walking?
A reflex action is a sudden, involuntary response to a stimulus, often controlled by the spinal cord. Walking is a voluntary action started by the brain, with balance and precision controlled by the cerebellum.
Which part of the brain controls walking?
The forebrain (cerebrum) starts the voluntary movement, and the cerebellum in the hindbrain controls the precision of movement, posture and balance.
What is a reflex arc?
A reflex arc is the pathway of a reflex action: receptor, sensory neuron, relay neuron in the spinal cord, motor neuron and effector muscle.
Why are reflex actions important?
They protect the body by producing a very quick response to harmful stimuli, before there is time to think.
Is walking a voluntary or involuntary action?
Walking is a voluntary action, because we decide when and where to walk.