Somatic Reflex Arc Components

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Questions and Answers

What is the primary function of the receptor in a somatic reflex arc?

  • To transmit motor signals to the effector
  • To process sensory information in the spinal cord
  • To connect the reflex arc to the brain for higher processing
  • To detect stimuli and initiate the reflex (correct)

In which type of reflex does the signal not involve an interneuron?

  • Reciprocal inhibition reflex
  • Stretch reflex (correct)
  • Withdrawal reflex
  • Cross extensor reflex

During reciprocal inhibition, which type of muscle is actively contracting?

  • Antagonist muscle
  • Agonist muscle (correct)
  • Synergist muscle
  • Flexor muscle

What component of the somatic reflex arc carries sensory information from the receptor to the spinal cord?

<p>Dorsal root (A)</p> Signup and view all the answers

Which type of reflex results in the contraction of extensor muscles on the opposite side of the stimulus?

<p>Cross extensor reflex (D)</p> Signup and view all the answers

What is the role of the ventral root in a somatic reflex arc?

<p>Delivering motor output from the spinal cord (B)</p> Signup and view all the answers

Which structure is primarily involved in muscle stretch detection in reflexes?

<p>Muscle spindle (B)</p> Signup and view all the answers

In the integration center of a somatic reflex arc, what typically occurs in polysynaptic reflexes?

<p>Interaction with an interneuron (B)</p> Signup and view all the answers

Which of the following effects results from the activation of an effector in a reflex arc?

<p>Contraction of a muscle or gland (B)</p> Signup and view all the answers

What type of neuron carries signals away from the spinal cord to muscles in a reflex arc?

<p>Efferent neuron (A)</p> Signup and view all the answers

Flashcards

Monosynaptic reflex

A reflex arc that involves only one synapse between a sensory neuron and a motor neuron. It is a direct pathway that results in a quick and simple response.

Polysynaptic reflex

A reflex arc that involves multiple synapses, including one or more interneurons. This allows for more complex integration and coordination.

Withdrawal reflex

A reflex that occurs when a painful stimulus is applied to the skin. It causes a withdrawal response, typically involving the flexion of a limb.

Stretch reflex

A reflex that occurs in response to stretching of a muscle. It causes a contraction of the same muscle, helping to maintain muscle tone and prevent overstretching.

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Cross extensor reflex

The automatic contraction of muscles on the opposite side of the body from a painful stimulus. This aids in maintaining balance and stability during a withdrawal reflex.

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Reciprocal inhibition

The simultaneous inhibition of opposing muscle groups during a reflex. This allows for smooth and coordinated movement.

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Receptor (Sensory Input)

The receptor in a reflex arc that detects the stimulus. This could be a pain receptor, a stretch receptor, or another type of sensory receptor.

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Afferent (Sensory) Pathway

The pathway that carries sensory information from the receptor to the spinal cord. This includes the peripheral nerve, spinal nerve, ramus, and dorsal root.

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Integration Center

The central processing unit of a reflex arc, where the sensory signal is processed and a motor response is initiated. This occurs in the gray matter of the spinal cord.

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Efferent (Motor) Pathway

The pathway that carries motor output from the spinal cord to the effector muscle. This includes the ventral root, spinal nerve, ramus, possibly a plexus, and the peripheral nerve.

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Study Notes

Somatic Reflex Arc Components

  • Receptor (Sensory Input): Detects a stimulus (pain, stretch) triggering the reflex. It's located on a sensory peripheral nerve and receives afferent signals. The signal goes to the spinal cord via the dorsal root.
  • Afferent (Sensory) Pathway: Carries sensory information from the receptor to the spinal cord. Components are peripheral nerve, spinal nerve, ramus, and dorsal root.
  • Integration Center (Processing): Located in the spinal cord's gray matter. Signals are processed. Polysynaptic reflexes involve interneurons; monosynaptic reflexes involve direct connection to a motor neuron.
  • Efferent (Motor) Pathway: Carries the response signal from the spinal cord to the effector. Components include ventral root, spinal nerve, ramus, plexus (if applicable), and peripheral nerve.
  • Effector (Motor Output): The muscle or gland that responds to the stimulus. In somatic reflexes, the response is usually a muscle contraction.

Types of Reflexes

  • Withdrawal/Flexor Reflex: Polysynaptic reflex triggered by pain or touch. The response is the contraction of the flexor muscles. Example: Pain reflex.
  • Cross Extensor Reflex: Polysynaptic reflex that happens in conjunction with the withdrawal reflex. The response is the contraction of the extensor muscles on the opposite side of the stimulated area. Crucial for balance during the withdrawal reflex.
  • Stretch Reflex: Monosynaptic reflex triggered by muscle stretch. The response is muscle contraction. Example: Knee-jerk reflex.
  • Reciprocal Inhibition: When one muscle group contracts (agonist), its opposing muscle group relaxes (antagonist). This allows efficient movement.

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