Question

James put his hand on a hot iron. An involuntary muscle reaction controlled by the spinal cord and called a ____________ allowed him to remove his hand quickly from the heat before sustaining further tissue damage.

Answer 1

James experienced a reflex, which is an involuntary and rapid response to a stimulus, such as pulling a hand away from a hot object. This is controlled by a reflex arc in the spinal cord that involves sensory and motor neurons and allows for immediate action without brain input.

Step-by-step explanation:

James put his hand on a hot iron. An involuntary muscle reaction controlled by the spinal cord and called a reflex allowed him to remove his hand quickly from the heat before sustaining further tissue damage. When high temperature is sensed in the skin, a reflexive withdrawal is initiated by the muscles of the arm. Sensory neurons are activated by the stimulus, which is sent to the central nervous system, and a motor response is sent out to the skeletal muscles that control this movement.

In the scenario described, the sensory receptors in the skin respond to the sensation of heat and send a nerve impulse along a sensory nerve to the spinal cord. There, the message passes to an interneuron and then to a motor nerve, which carries the impulse to a muscle causing it to contract. This series of neuron connections form a reflex arc, which requires no input from the brain, allowing for a rapid response to the painful stimulus.

The efficiency of reflexes, such as withdrawing a hand from a hot object or the knee response, is due to the local synaptic connections involving very few synapses, sometimes just a single synapse between a sensory neuron and a motor neuron, which enables a quick reaction. Synapses with interneurons in the spinal column, meanwhile, transmit information to the brain to convey what happened.

Answer 2

A reflex arc initiated by a sensory neuron and controlled by the spinal cord is what allowed James to quickly remove his hand from the hot iron. This rapid and unconscious response to high temperature happens through a pathway that bypasses the brain, resulting in the immediate contraction of muscles to avoid injury.

Step-by-step explanation:

James put his hand on a hot iron. An involuntary muscle reaction controlled by the spinal cord and called a reflex arc allowed him to remove his hand quickly from the heat before sustaining further tissue damage. This rapid motor response is not directed by the brain but by the spinal cord. A sensory neuron is activated by the high temperature stimulus and sends a message to the spinal cord, where it is relayed through an interneuron to a motor neuron. This results in a motor response that causes the skeletal muscles to contract, pulling the hand away from the danger.

In a reflex, the sensory information travels only as far as the spinal cord and does not reach the brain, resulting in a very fast withdrawal of the hand. This is part of the somatic nervous system which controls some unconscious movements known as reflexes. The quick, unconscious withdrawal from a hot object is facilitated by local synaptic connections, including those with interneurons in the spinal column that also convey what happened to the brain.