Edexcel A Level (IAL) Biology -8.2 How a Response is Generated by Effectors- Study Notes- New Syllabus
Edexcel A Level (IAL) Biology -8.2 How a Response is Generated by Effectors- Study Notes- New syllabus
Edexcel A Level (IAL) Biology -8.2 How a Response is Generated by Effectors- Study Notes -Edexcel A level Biology – per latest Syllabus.
Key Concepts:
- 8.2 understand how the nervous system of organisms can cause effectors to respond to a stimulus
How the Nervous System Triggers Responses
🌱 Introduction
The nervous system detects changes in the environment (stimuli) and coordinates responses by sending electrical impulses to effectors (muscles or glands).
🔍 Step-by-Step Process
1. Stimulus Detection
- A receptor detects a change (e.g., light, heat, pressure).
- Converts stimulus into an electrical impulse.
2. Transmission to CNS
- Impulse travels along a sensory neurone to the CNS (brain/spinal cord).
3. Processing in CNS
- Relay (inter) neurones connect sensory and motor neurones.
- CNS interprets the signal and decides the response.
4. Impulse to Effector
- Motor neurone carries impulse from CNS to effector.
5. Effector Response
- Muscles contract → movement.
- Glands secrete hormones or enzymes → chemical response.
🔁 Reflex vs Voluntary Responses
| Type | Speed | Pathway | Example |
|---|---|---|---|
| Reflex | Very fast | Sensory → Relay → Motor (spinal cord) | Pulling hand from hot object |
| Voluntary | Slower | Sensory → Brain → Motor | Picking up a pen |
📌 Key Points
- Receptors detect stimuli and convert them into electrical impulses.
- Neurones transmit impulses rapidly.
- Effectors respond appropriately (muscle contraction or gland secretion).
- Nervous system enables quick, coordinated responses to environmental changes.
📦 Quick Recap
Receptor detects → Sensory neurone → CNS (relay/inter neurone) → Motor neurone → Effector → Response
Muscles = movement, glands = secretion.
Reflex arcs are faster, voluntary responses involve the brain.
Receptor detects → Sensory neurone → CNS (relay/inter neurone) → Motor neurone → Effector → Response
Muscles = movement, glands = secretion.
Reflex arcs are faster, voluntary responses involve the brain.