Overview
This lecture explains the withdrawal (flexor) reflex, covering its mechanism, characteristics, and functional significance in protecting the body from harm.
Withdrawal (Flexor) Reflex Mechanism
- The withdrawal reflex is a rapid, automatic response to painful stimuli that causes the affected limb to pull away.
- Sensory neurons detect a harmful stimulus (like touching something hot or sharp) and send signals to the spinal cord.
- In the spinal cord, sensory neurons synapse with interneurons, which then activate motor neurons.
- Motor neurons stimulate flexor muscles, causing contraction and withdrawal of the limb from the stimulus.
Characteristics of the Reflex
- The withdrawal reflex is polysynaptic, meaning it involves multiple synapses with interneurons in the spinal cord.
- The response occurs on the same side of the body as the stimulus, making it ipsilateral.
- This reflex allows for a fast reaction without needing to send the signal all the way to the brain first.
- The brain can override or modify the withdrawal reflex if necessary.
Functional Importance
- The main function of the withdrawal reflex is to protect the body from damage by responding quickly to potentially harmful stimuli.
- This reflex is essential for survival as it minimizes injury by promoting rapid withdrawal from danger.
Key Terms & Definitions
- Withdrawal (flexor) reflex — An automatic response in which a limb is pulled away from a painful stimulus.
- Polysynaptic — Involving more than one synapse between neurons in a reflex pathway.
- Ipsilateral — Occurring on the same side of the body as the stimulus.
- Interneurons — Nerve cells in the spinal cord that relay signals between sensory and motor neurons.
Action Items / Next Steps
- Review diagrams or images illustrating the withdrawal reflex pathway.
- Study how the withdrawal reflex differs from other reflexes (e.g., stretch reflex).
- Prepare for any quiz or discussion on reflex pathways and their functional relevance.