Component 3.5 - Nerve Nets And Neurones Flashcards
What are the two types of cells which a nerve net contain?
- Ganglion cells provide short extensions to other nerve cells
- Sensory cells to detect stimuli
What can the nerve net do?
- It can sense light, physical contact and chemicals (limited number of stimuli)
- This means it can: contract, hunt and feed (number of effectors is small)
What is a vital thing that the nerve net cannot do?
It cannot detect the direction of a stimulus BUT a large stimulus can stimulate a larger response
Compare the hydra nerve net (1) and the human nervous system (2):
- Nervous system type
- Number of cell types in nervous system
- Regeneration
- Myelin sheath
- Conduction speed
- Ability to regenerate neurones
1: Nerve net, 2 types of cells, Rapid regeneration, No myelin sheath, Slow conduction speed, There is an ability to regenerate neurones
2: CNS, Many types of cells, Very slow regeneration (maybe none), There is a myelin sheath, Fast conduction speed, No ability to regenerate neurones
What do relay neurones do?
Receive impulses from sensory neurones or other relay neurones and transmit them to motor neurones or other relay neurones
Function of dendrite
Thin fibre carrying impulses towards cell body
Function of Axon
Thin fibre carrying impulses away from the cell body
Function of the nodes of ranvier
Gaps in myelin sheath where Schwann cells meet and where axon membrane is exposed - this means impulses can be transmitted rapidly
Function of Schwann cells
Surround and support nerve fibres
Functions of the cell body
Contains a nucleus and a granular cytoplasm
Function of nucleus
Holds DNA
Function of myelin sheath
Electrical insulator; speeds up transmission of impulses
Function of axon ending
Secretes neurotransmitter, which transmits impulse to adjacent neurone
Function of synaptic end bulb
Swelling at end of axon, in which neurotransmitter is synthesised
