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Difficulty: MediumHuman Anatomy and Body Systems

When a person accidentally touches a hot surface, an involuntary somatic reflex is triggered to quickly withdraw the hand. In what sequence does the electrical nerve impulse travel through the anatomical structures of the reflex arc from initial stimulus detection to the muscular response?

  1. 1Sensory receptor in the skin
  2. 2Afferent (sensory) neuron
  3. 3Interneuron in the spinal cord
  4. 4Efferent (motor) neuron
  5. 5Effector muscle in the arm

Answer

The correct physiological sequence is: Sensory receptor in the skin → Afferent (sensory) neuron → Interneuron in the spinal cord → Efferent (motor) neuron → Effector muscle in the arm.
In a somatic reflex arc, the signal moves unidirectionally: the sensory receptor detects the stimulus, the afferent (sensory) neuron carries the impulse inward to the spinal cord, an interneuron integrates the signal within the spinal cord gray matter, the efferent (motor) neuron conducts the motor command outward, and the effector muscle contracts to pull the body part away.

Step-by-Step Solution

1
Identify the initial anatomical structure that transduces the physical stimulus into an electrical signal.
The sensory receptor in the skin detects the thermal stimulus and initiates the impulse.
Receptors are specialized structures that convert external environmental stimuli into nerve action potentials.
2
Trace the incoming pathway traveling toward the central nervous system.
The afferent (sensory) neuron propagates the electrical impulse into the spinal cord.
Afferent fibers conduct sensory information from peripheral tissues toward the central nervous system.
3
Identify the integration center within the central nervous system.
The interneuron in the spinal cord processes the incoming signal and relays it to an outgoing motor pathway.
Interneurons in the spinal gray matter allow immediate local routing without waiting for brain processing.
4
Trace the outgoing command pathway traveling away from the central nervous system.
The efferent (motor) neuron conducts the impulse away from the spinal cord.
Efferent fibers transmit motor signals from the central nervous system to peripheral target organs.
5
Identify the responding peripheral structure that carries out the physical action.
The effector muscle in the arm contracts to complete the reflex withdrawal.
Effector organs execute the mechanical or physiological response dictated by motor signals.

Key Concept

Somatic spinal reflex arc pathway and directional flow of neural transmission
Estimated Time:1m 0s
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Topics

Human Anatomy and Body Systems

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