8.1.10Unit 6: Practical Skills in Biology II
Central and Peripheral Nervous System — IAL Edexcel Linear Revision Notes & Topical Questions
5 min read 5 parts Lesson 35 of 48 Unit quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5Divisions of the Nervous System
The human nervous system is divided according to where its parts are found.
Central nervous system
- Central nervous system The CNS is the brain and spinal cord, which act as the main coordinating centre.
Peripheral nervous system
- Peripheral nervous system The PNS includes all nerves outside the CNS, extending to the rest of the body.
Role of the PNS
- Role of the PNS It carries impulses from receptors to the CNS and from the CNS out to the effectors.
Nerve
- Nerve A bundle of neurones, usually wrapped together, that carries impulses around the body.
Part 2 of 5Types of Neurone
Three types of neurone form the pathway through the nervous system.
Types of Neurone
Sensory neurone
- Sensory neurone Carries impulses from a receptor towards the central nervous system.
Relay neurone
- Relay neurone Lies within the CNS and connects sensory neurones to motor neurones.
Motor neurone
- Motor neurone Carries impulses from the CNS to an effector such as a muscle or gland.
Part 3 of 5From Stimulus to Response
Information always passes along the same sequence of components.
1
A stimulus, a change in the surroundings, is detected by a receptor cell, which is often part of a sense organ.
2
The receptor generates impulses that pass along a sensory neurone to the CNS.
3
The CNS coordinates the information, and impulses are sent along a motor neurone to an effector.
4
The effector, a muscle or a gland, carries out the response.
Part 4 of 5Receptors and Effectors
Receptors are gathered into sense organs, while effectors are muscles or glands.
Photoreceptors
- Photoreceptors These respond to light and are found in the retina of the eye.
Chemoreceptors
- Chemoreceptors These respond to chemicals and are found, for example, on the tongue.
Pressure receptors
- Pressure receptors These respond to pressure and are found in the skin and in blood vessels.
Effectors
- Effectors Muscles respond by contracting, and glands respond by secreting a substance.
| Component | Example | Role |
|---|---|---|
| Stimulus | Pressure on the skin | Change that is detected |
| Receptor | Pressure receptor | Converts the stimulus into impulses |
| Coordinator | Spinal cord | Processes information and sends output |
| Effector | Muscle | Produces the response |
Part 5 of 5Exam Checklist & Tips
8.1.10 – Key Points for the Exam
- CNS The central nervous system, made up of the brain and the spinal cord.
- PNS The peripheral nervous system, comprising the nerves outside the brain and spinal cord.
- Receptor A cell that detects a stimulus and generates an electrical impulse.
- Effector A muscle or gland that carries out the response.
- Relay neurone A neurone in the CNS that links sensory and motor neurones.
Common Mistakes
- Thinking the spinal cord belongs to the PNS; the brain and spinal cord together form the CNS.
- Mixing up the direction of sensory and motor neurones: sensory goes to the CNS and motor comes from it.
- Calling the receptor the effector; the receptor detects the stimulus and the effector produces the response.
- Writing that a nerve is a single neurone; a nerve is a bundle of neurones.
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