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Summary WJEC (England) Eduqas A-Level Biology 3. Requirements for life - 5. Nervous System CA$5.53   Add to cart
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Summary WJEC (England) Eduqas A-Level Biology 3. Requirements for life - 5. Nervous System
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  • 3. Requirements for life
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I achieved a high A* Grade in my final A-Level exams using these notes!!! I believe you can achieve an A* if you can memorise these notes! Simply use blurting, a method of active recall, to write everything you remember from the notes, then identify the parts you couldn’t remember, then repeat ...

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Document information

  • May 2, 2023
  • 4
  • 2021/2022
  • Summary

Subjects

  • spinal cord
  • nervous system
  • nerve net
  • motor neurone
  • nerve impulse
  • action potential
  • synapse
  • synaptic transmission

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  • A/AS Level
  • WJEC
  • Biology
  • 3. Requirements for life
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a. nervous response
1. Receptor – detect internal/external stimuli & convert energy to electrical impulse
2. Coordinator: CNS
3. Effector: muscle/gland – response

Human nervous system
 Central Nervous System = brain & spinal cord
 Peripheral Nervous System: connect CNS to receptors & effectors
o Somatic: nerve pairs originating from CNS – contain sensory & motor neurones
o Autonomic: unconscious control of internal organ function


b. spinal cord
- White matter: myelinated nerve fibres
- Dorsal root (back): where sensory neurones enters
o Dorsal root ganglion (swelling): collection of sensory neurone cell bodies
- Grey matter: less myelin (relay neurones & motor cell bodies)
- Ventral root (front): where motor neurones leave
- central fluid-filled canal
- meninges: 3 tough protective membranes surrounding CNS


c. neurones (cell that bundle into nerve)
 Sensory: receptor → CNS
 Relay in CNS: sensory → motor
 Motor: CNS → effector

d. reflex arc – basis for rapid/protective/involuntary actions
Stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response


e. nerve net: simple nervous system in Cnidaria – Hydra
- Sensory cells: photoreceptors & touch receptors in body wall & tentacles
(few receptors = respond to limited number of stimuli)
- Ganglion cells: provide short connections to branch neurones in different directions
Cnidaria phylum Mammals
- 1 simple neurone type - 3 neurone types
- Unmyelinated - Myelinated
- Short & branched - Long & unbranched
- Impulse in both directions - Impulse in 1 direction
- Slow impulse transmission - Fast impulse transmission
- No brain - Brain

f. motor neurone
- Dendrites: carry impulse towards cell body
- Cell body: nucleus (DNA) & granular cytoplasm (organelles – ribosomes to make enzymes for NT synthesis)
- Axon: impulse away from cell body
o Axon endings: secrete neurotransmitter
o Synaptic end bulbs (swelling): neurotransmitter synthesis
- Myelin sheath (vertebrates): electrical insulator
o formed by Schwann cells: extends & wraps around neurone
o Nodes of Ranvier: 1um: gaps (between Schwann cells) – expose axon

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