lab 11

nervous system anatomy, reflex actions, and motor learning

What effects would you expect from an injury that severs the spinal cord at the fifth cervical vertebra?

• Paralysis below C5 (quadriplegia)  

• Loss of motor control in trunk and legs  

• Partial arm/shoulder movement may remain  

• Breathing impaired (diaphragm partly works via C3–C5, but weak)  

• Loss of sensation below injury  

How many spinal nerves and vertebrae are there? What is the anatomical relationship between them?

• 31 pairs of spinal nerves  

• 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal  

• 33 vertebrae  

• 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), 4 coccygeal (fused)  

Relationship: 

• Spinal nerves exit between vertebrae  

• Cervical nerves exit above corresponding vertebrae (except C8)  

• Below that, nerves exit below their vertebra 

Describe the location of the spinal cord. What are the cervical and lumbar enlargements?

• Located within the vertebral canal  

• Extends from brainstem → ~L1–L2  

Enlargements: 

• Cervical enlargement: supplies arms  

• Lumbar enlargement: supplies legs 

Define a “cranial nerve”. How are cranial nerves named and numbered?

• Nerves that arise directly from the brain  

Naming & numbering: 

• Numbered I–XII (Roman numerals)  

• Named based on function or location (e.g., optic, vagus) 

Distinguish between the direct light reflex and the consensual light reflex. What is the purpose of these reflexes?

• Direct reflex: pupil constricts in same eye exposed to light  

• Consensual reflex: opposite eye also constricts  

Purpose: 

• Protect retina from excess light  

• Improve visual clarity  

What role does the muscle spindle play in the knee jerk reflex?

Detects muscle stretch → initiates reflex 

Why would an injury to a peripheral nerve cause loss of both sensory and motor functions?

• Peripheral nerves contain both sensory and motor fibers  

• Damage interrupts both incoming and outgoing signals 
  → Loss of sensation AND movement  

What evidence is there that both negative transfer and bilateral transfer occurred during the course of your mirror-trace experiment.

• Negative transfer: initial performance worse due to reversed visual input  

• Bilateral transfer: improvement in one hand helps the other hand perform better  

Based on the results of the knowledge of results experiment that you performed in the BPK 142 lab with the linear arm positioning apparatus, what conclusions can you draw regarding the importance of knowledge of results for learning?

• Knowledge of results improves learning and accuracy  

• Provides feedback to correct errors  

• Without feedback → slower learning and poorer performance