Reflex Arc

Reflexes

  • Rapid, automatic responses to a change in external/internal environment

  • Protects the body from injury

 

Properties

  • Stimulus -> Required to trigger a reflex (Not spontaneous)

  • Involuntary -> occurs without any conscious thought

  • Rapid -> only a small number of neurons are involved

  • Stereotyped -> occurs in the same way each time it happens

 

Most reflexes are coordinate by the spinal cord -> Spinal Reflex

The message is not carried to the brain, however, it can be made aware after the response has been carried out

Some reflexes involve the unconscious parts of the brain -> reflex

The pathways a nerve impulse following in travelling from receptor to effector is known as a reflex arc

 

Reflex Arc

  1. Receptor -> Ending of a sensory neuron, which reacts to a change in internal/external environment, initiates a nerve impulse

  2. Sensory neuron -> carries impulses from receptors to the CNS

  3. Synapse with an interneuron -> at least one, can be passed directly to a motor neuron or may be one or more interneurons (direct impulse to correct motor neuron)

  4. Motor neuron -> carries a nerve impulse to an effector

  5. Effector -> Part of the body that receives nerve impulse, carrying out appropriate responses

  6. Response -> Usually a muscle/secretory cell (what the effector does)

 

Learnt/Acquired reflexes are when complex motor patterns are learned through constant repetition

 

Innate reflexes appear during a baby's development, and are determined genetically.