Somatic Motor Pathway and Neuromuscular Junction

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Questions and Answers

Which of the following accurately describes a somatic motor pathway?

  • It contains interneurons that modulate the signal before reaching the muscle.
  • It is comprised of a somatic motor neuron and skeletal muscle. (correct)
  • It involves a series of synapses between multiple motor neurons.
  • It consists of sensory neurons communicating directly with skeletal muscle.

What is the primary role of acetylcholinesterase (AChE) at the neuromuscular junction?

  • To break down acetylcholine (ACh), preventing continuous muscle fiber stimulation. (correct)
  • To synthesize acetylcholine (ACh) for continued neurotransmission.
  • To transport acetylcholine (ACh) across the synaptic cleft.
  • To bind with acetylcholine (ACh) receptors on the muscle fiber.

How do voltage-gated calcium channels contribute to signal transmission at the neuromuscular junction?

  • By repolarizing the muscle fiber after contraction.
  • By facilitating the reuptake of acetylcholine (ACh) from the synaptic cleft.
  • By triggering the exocytosis of vesicles containing acetylcholine (ACh). (correct)
  • By directly depolarizing the motor neuron terminal.

What is the functional significance of the motor unit?

<p>It provides a mechanism for graded muscle contractions through recruitment. (D)</p> Signup and view all the answers

Where does the sensory pathway terminate to allow conscious perception of a sensory stimulus?

<p>The cerebral cortex. (D)</p> Signup and view all the answers

How do interneurons contribute to nervous system function?

<p>By acting as a processing center and relaying information within the brain and spinal cord. (C)</p> Signup and view all the answers

What is the primary distinction between the central nervous system (CNS) and the peripheral nervous system (PNS)?

<p>The CNS consists of the brain and spinal cord, while the PNS comprises the nerves that connect these to the rest of the body. (A)</p> Signup and view all the answers

The efferent division of the peripheral nervous system is responsible for which of the following functions?

<p>Carrying motor commands from the central nervous system to muscles and glands. (A)</p> Signup and view all the answers

Which of the following best describes the role of myelin in the nervous system?

<p>It increases the speed of action potential propagation along axons. (A)</p> Signup and view all the answers

In the context of spinal cord anatomy, what is the primary function of the ascending tracts?

<p>To transmit sensory information from the body to the brain. (D)</p> Signup and view all the answers

The spinal cord primarily functions in what processes?

<p>Conduit for nerve impulses to and from the brain and spinal reflexes. (D)</p> Signup and view all the answers

What functional role do sensory neurons play in the nervous system?

<p>Carry sensory information from the body to the brain and spinal cord. (B)</p> Signup and view all the answers

What is the difference between sensory and motor neurons?

<p>Sensory neurons transmit the impulse to the brain or spinal cord, and motor neurons transmit the impulse from the brain or spinal cord. (C)</p> Signup and view all the answers

Which of the following accurately describes a reflex arc?

<p>A rapid, involuntary response to a stimulus mediated by a direct neural pathway. (D)</p> Signup and view all the answers

How does the body maintain balance and coordination during a withdrawal reflex?

<p>Interneurons work cross laterally to coordinate the motor reflexes in both sides of the body, so the body maintains its balance while the affected part experiences the reflex. (A)</p> Signup and view all the answers

A doctor taps the patellar ligament with a rubber hammer, stimulating sensory neuron responses that leads to what action?

<p>Initiating a synapse from a sensory neuron to a motor neuron. (A)</p> Signup and view all the answers

During the 'testing the water' example, the sensory neuron sends the stimulus to the thalamus. What is the next step?

<p>The sensory signal is processed in the primary cortex. (A)</p> Signup and view all the answers

How an action potential is initiated in "Testing the water" example?

<p>If the graded potential from the sensory endings is strong enough. (D)</p> Signup and view all the answers

Which of the following is true about the nervous system and its relation with the cardiovascular system?

<p>The nervous system helps control blood flow and blood pressure through nervous signals. (B)</p> Signup and view all the answers

Where does the sensory information pass through after the somatosensory cortex?

<p>Frontal cortex. (E)</p> Signup and view all the answers

Flashcards

Somatic motor pathway

A pathway comprised of a somatic motor neuron and skeletal muscle.

Neuromuscular junction

The site where a somatic motor neuron synapses with a skeletal muscle fiber.

Motor neurons

Nerves that innervate muscle fibers.

Motor unit

A single motor neuron and the muscle fibers it innervates.

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Functions of the nervous system

Receiving information, deciding what to do, and acting on those decisions.

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Sensory neurons

Conduct impulses from peripheral body parts into the brain or spinal cord.

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Interneurons

Lie within the brain or spinal cord and form links with other neurons relay information.

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Motor neurons

Conduct impulses out of the brain or spinal cord to effectors.

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CNS

The brain and spinal cord; control centers.

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PNS

Efferent and afferent nervous tissue that links the CNS with sense organs and other systems.

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ANS

Components of the CNS and PNS that control visceral functions.

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Nerve

A bundle of axons in the PNS.

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Neuron

The basic functional unit of the nervous system; a highly specialized cell; a nerve cell.

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Sensory neuron

A neuron whose axon carries sensory information from the PNS toward the CNS.

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Motor neuron

A neuron whose axon carries motor commands from the CNS toward effectors.

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Ascending tracts

The spinal tracts that conduct sensory information to the brain

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Descending tracts

The spinal tracts that conduct impulses from the brain to motor neurons reaching muscles and glands

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Monosynaptic reflex

Uses only two neurons: a sensory neuron and a motor neuron.

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Receptor

The receptor end of a dendrite or a specialized receptor cell in a sensory organ.

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Reflexes

A rapid, stereotyped response to a specific stimulus

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Study Notes

Somatic Motor Pathway

  • It includes a somatic motor neuron and skeletal muscle.

Neuromuscular Junction

  • This is where a somatic motor neuron synapses with a skeletal muscle fiber.

Signal Transmission at the Neuromuscular Junction

  • Motor neurons are nerves that control muscle fibers.
  • A motor unit consists of a motor neuron and the muscle fibers it controls.
  • A single motor unit can activate a few or thousands of muscle fibers.

General Functions of the Nervous System

  • Receiving information (sensory function).
  • Deciding what to do (integrative function).
  • Acting on those decisions (motor function).

Neuron Classification

  • Sensory neurons (afferent) transmit impulses from body parts to the brain or spinal cord.
  • Interneurons are located in the brain or spinal cord, forming connections with other neurons and relaying information.
  • Motor neurons (efferent) carry impulses from the brain or spinal cord to effectors.

Spinal Cord

  • The spinal cord is a slender column of nervous tissue continuous with the brain, extending through the vertebral canal.
  • It is composed of 31 segments, each giving rise to a pair of spinal nerves which connect to different body parts and the CNS.
  • The spinal cord serves as a center for spinal reflexes and a conduit for impulses to and from the brain.

Ascending and Descending Tracts

  • Ascending tracts carry sensory information to the brain.
  • Descending tracts carry motor impulses from the brain to muscles and glands.

Testing the Water: Neural Pathway Example

  • A sensory neuron in the skin detects a stimulus like water temperature.
  • A graded potential from the sensory endings triggers an action potential.
  • The sensory neuron's axon enters the spinal cord and synapses with another neuron.
  • An action potential travels up the sensory pathway to the thalamus in the brain.
  • The sensory pathway ends in the cerebral cortex.
  • A motor command is sent from the frontal cortex after integration in the cerebral cortex.
  • The upper motor neuron sends an action potential down to the lower motor neuron's dendrites in the spinal cord.
  • The lower motor neuron's axon exits the spinal cord and connects to a muscle via a neuromuscular junction.
  • This causes the target muscle to contract.

Patellar Reflex

  • A monosynaptic reflex uses only 2 neurons: a sensory neuron and a motor neuron.

Arc Reflex

  • The components include a receptor, a sensory neuron, an interneuron, a motor neuron, and an effector.

Withdrawal Reflex

  • Involves sensory, interneurons, and motor neurons to withdraw from a stimulus.
  • When the flexor muscle contracts on one side, the extensor muscle on the opposite side also contracts for balance.

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