Nerve Organisation
• Central Nervous System (CNS): Made up of the brain and spinal cord
• Peripheral Nervous System (PNS) Made up of the pairs of nerves that originate from either the brain or the spinal chord
o Sensory Neurons: Carry nerve impulses from receptors CNS
o Motor Neurons: Carry nerve impulses away from CNS Effectors
• The motor Neuron system can be divided into:
o Voluntary Nervous system: Nerve impulses to body muscles is with conscious
o Autonomic Nervous system: Nerve impulses to glands, smooth muscles and cardiac muscles and is without conscious
Spinal Cord
• The spinal cord is a column of nervous tissue that runs along the back and lies inside the vertebral column for protection
• At regular intervals do pair of nerves separate off of the cord
Reflex Arc
Step |
Stage |
Example: Heat |
1 |
Stimulus |
Heat from hot object |
2 |
Receptor |
Temperature receptors in skin create nerve impulse to sensory neuron |
3 |
Sensory Neuron |
Passes nerve impulse to spinal cord |
4 |
Intermediate Neuron |
Links the sensory neurone to the motor neuron found in spinal cord |
5 |
Motor Neuron |
Carries nerve impulse from spinal cord to muscle in the upper arm |
6 |
Effector |
Muscle in upper arm, which is stimulated to contract |
7 |
Response |
Hand is pulled away from hot object |
Importance of the Reflex Arc
• The reflex arc is an involuntary response which allows for an instant reaction to a danger
• The reflex arc being involuntary frees up the brain to carry out more complex tasks
• The reflex arc does not have to be learnt and therefore is effective since birth
• The response is fast as the neurone pathway is short from spinal cord to receptor this is further increased by few synapses.