4BI1
Coordination & Response
Structures and Functions in Living Organisms · 7 question types
Exam Frequency Analysis
Past paper frequency (2018 to 2024)
This topic accounts for approximately 14% of your exam marks.
stable
High
Stable14%
Nervous system structure, reflex arcs, and hormones are all commonly examined.
The human nervous system is built from two parts:
- The central nervous system (CNS): the brain and spinal cord. This is where the decisions are made.
- The peripheral nervous system (PNS): every nerve outside the CNS. These connect the CNS to the receptors and effectors all over the body.
A nerve is a bundle of long thin cells called neurones. Each neurone carries electrical impulses along its length.
Three types of neurone
| Neurone | Carries impulses... | Found in... |
|---|---|---|
| Sensory neurone | From a receptor to the CNS | The PNS |
| Relay neurone | Within the CNS, from one neurone to another | The CNS only |
| Motor neurone | From the CNS to an effector | The PNS |
The standard pathway through the nervous system, in summary form:
receptor → sensory neurone → (relay neurones) → motor neurone →