Reflex Arc: Hand Pulls Away from Heat

Also called

reflex arc · reflex action · withdrawal reflex · spinal reflex · neuron · nerve cell · synapse · neurotransmitter · sensory neuron · motor neuron · relay neuron · interneuron · spinal cord · nerve impulse · control and coordination · hot object reflex

Topics

• A reflex action is a quick, automatic response to a stimulus that does not wait for thinking in the brain
• The reflex arc: receptor -> sensory neuron -> spinal cord (relay neuron) -> motor neuron -> effector muscle
• A withdrawal reflex has at least one relay neuron (interneuron) in the spinal cord, so it has two synapses in this model
• Sensory signals enter the spinal cord by the dorsal root; motor signals leave by the ventral root
• Signals travel along neurons as electrical impulses, in one direction only
• At a synapse the electrical signal stops; neurotransmitter chemicals cross a very narrow gap and start a new signal in…
• The flexor muscle is the effector: it shortens and bends the elbow, pulling the hand away
• Information also travels up the spinal cord to the brain, so you feel the heat after the hand has already moved
• If the sensory or motor nerve is cut, the reflex fails

About this model

A GLB file of about 1770 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Made for Lably. Neuron close-up: "Neuron / Nervenzelle" by Barbara Henn, Tactiles (tactiles.eu), CC BY-SA 4.0, simplified. Brain and spinal cord: HuBMAP Human Reference Atlas CCF 3D Reference Object Library (Kristen Browne et al., NIH/NIAID; NLM Visible Human Project; brain: Allen Institute), CC BY 4.0, simplified and re-placed. | CC BY-SA 4.0 (includes CC BY-SA 4.0 Tactiles neuron and CC BY 4.0 HuBMAP HRA brain and spinal cord models)

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