Lab Week 3 – Nervous System- Spinal cord, PNS and reflexes

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Lab Week 3 – Nervous System- Spinal cord, PNS and reflexes

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Myriam Thomas

Dr. H

Anatomy and Physiology II

Chamberlain University

7/21/2023

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Week 3 Nervous System-Spinal cord, PNS, and reflexes

Learning Objectives:

• Locate and identify the regions and parts of the spinal cord.
• Identify the spinal contributions to cervical, brachial, lumbar, sacral and coccygeal plexuses.
• Locate and identify major peripheral nerves.
• Identify the components of a reflex arc.

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Introduction: The spinal cord is a continuation from the medulla oblongata of the brain stem. It allows communication between the brain and the rest of the body. The spinal nerves contain both sensory and motor fibers. We will see that multiple spinal cord levels can contribute to the formation of a peripheral nerve as fibers pass through the various plexuses. The protective role of a reflex arc will be examined.

Assignment:

Part 1: Complete the following activities

Anatomy.TV: Nervous System- Spinal cord, Spinal nerves, Reflexes

To access Anatomy.TV: Resources tab>Library>Library Resources-Database A-Z>Anatomy.TV>Titles(default tab): Choose Nervous system>choose assigned sections

You will then work through the material and activities by scrolling down on the right. This will allow you to see and work through all activities for that section.

Have the lab report with you as you complete the activities so you may record data.

Part 2: Complete the lab report

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Week 3 Nervous System Lab Report

1.Describe the anatomy of the spinal cord by completing the following chart: (3 points)

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# of associated segments/spinal nerve pairs

Spinal cord

Continuous from medulla oblongata, the spinal cord descends in the vertebral canal with 31 segments (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal). It displays cervical and lumbar enlargements and terminates at the cauda medullaris around L2 level.

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(31 pairs)

Cervical region

Eight pairs of spinal nerves are denoted as C1 to C8. (8 pairs)

Thoracic region

There are twelve pairs of spinal nerves represented as T1 to T12. (12 pairs)

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Lumbar region

Five pairs of spinal nerves are designated as L1 to L5. (5 pairs)

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Sacral region

There are five pairs of spinal nerves indicated as S1 to S5. (5 pairs)

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Coccygeal

A single pair of spinal nerves is identified as Co1.( 1 pair)

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2. Define the following terms: (1 point each)

Cauda equina

The cauda equina, resembling a horse’s tail, is a collection of nerve roots situated at the lower end of the spinal cord. It emerges from the lumbar and sacral areas and comprises spinal nerve roots that extend down the vertebral canal and exit the spinal column through the intervertebral foramina. This intricate network of nerve roots is responsible for transmitting nerve signals to and from the lower limbs, pelvic organs, and perineum.

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Conus medullaris

The conus medullaris is the pointed, lower extremity of the spinal cord, situated at the level of the first or second lumbar vertebra in adults. It serves as the endpoint of the main spinal cord. Below the conus medullaris, the spinal cord transitions into the cauda equina.

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Reflex

A reflex is an automatic and swift response to a stimulus that takes place without conscious thought or control from the brain. These involuntary reactions are crucial for the body’s protection and survival, enabling rapid responses to potential dangers or changes in the environment.

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4. Describe a reflex arc including the 5 components. (5 points)

1.Sensory Receptor: This element of the reflex arc detects the stimulus from the surrounding environment. It can be found in various locations such as the skin, muscles, tendons, or other sensory organs.
2.Sensory Neuron: The sensory neuron, also known as the afferent neuron, carries the sensory information from the receptor to the central nervous system (CNS), specifically the spinal cord or brain.
3.Integration Center: Within the CNS, typically situated in the spinal cord or brainstem, lies the integration center. It processes and analyzes the sensory information and determines the appropriate reflex response.
4.Motor Neuron: The motor neuron, also referred to as the efferent neuron, receives the processed information from the integration center. It then conveys the motor response signal to the effector organ.
5.Effector Organ: The effector organ is the target tissue or organ that carries out the reflex action in response to the motor neuron’s signal. It can be a muscle or a gland, and its response is typically designed to counteract or adjust to the initial stimulus.

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5. Describe the reflex response to a painful stimulus such as stepping on a nail. (2 points)

     

When a painful stimulus, like stepping on a nail, stimulates the pain receptors (receptors), the sensory neurons transmit the signal to the spinal cord (integration center). The spinal cord processes this information and triggers an instant motor response. Motor neurons are then activated to contract the muscles involved in removing the foot from the painful stimulus (effector), resulting in a swift withdrawal reflex.

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6. Discuss why a person who has a spinal cord injury at C6 is spared from needing a ventilator. In order to answer you must consider what nerve innervates the diaphragm and which spinal cord segments contribute to this nerve. (2 points)

A person with a spinal cord injury at C6 is spared from needing a ventilator because the phrenic nerve responsible for diaphragm innervation receives contributions from C3, C4, and C5 spinal cord segments, which are above the injury level. This preserved innervation allows the diaphragm to function, enabling the individual to breathe without ventilatory assistance.

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Grading Rubric for Lab Report

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Activity 

Deliverable 

Points 

Part 1

Complete lab activities

15

Part 2

Complete lab report

15

Total  

Complete all lab activities  

30

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