Dermatomes

The video tutorial by Dr. Morton explores the sensory deficits that occur when injuring a brachial plexus root compared to a peripheral nerve. It explains the concept of dermatomes, areas of skin supplied by sensory neurons from a single spinal cord level, and how these neurons are transmitted through various nerves. Using an analogy with Google Maps, the tutorial illustrates how understanding the brachial plexus is akin to mapping routes. It includes practice questions to reinforce learning about dermatomes, cutaneous fields, and nerve injuries, emphasizing the impact of injuries on sensation.

What is a dermatome?

• A type of muscle in the arm

• A type of bone in the spine

• An area of skin supplied by sensory neurons from a single spinal cord level

• A nerve that controls muscle movement

Which nerves transmit sensory neurons from the C5 dermatome to the spinal cord?

• Radial and ulnar nerves

• Ulnar and median nerves

• Axillary and radial nerves

• Musculocutaneous and median nerves

Which nerve is primarily responsible for transmitting sensory neurons from the C8 dermatome?

• Axillary nerve

• Median nerve

• Ulnar nerve

• Radial nerve

What analogy is used to understand the sensation of the brachial plexus?

• A weather map

• Google Maps

• A train map

• A treasure map

If the ventral ramis is injured, what happens to the dermatome?

• Only part of the dermatome loses sensation

• The entire dermatome loses sensation

• The dermatome gains extra sensation

• The dermatome remains unaffected

What is a cutaneous field?

• A type of bone in the arm

• An area of skin supplied by sensory neurons from a single peripheral nerve

• A type of muscle in the leg

• A nerve that controls skin temperature

Which nerve transmits sensation from the thumb and index finger?

• Axillary nerve

• Ulnar nerve

• Radial nerve

• Median nerve

What happens if a peripheral nerve is injured?

• Sensation is lost in the entire dermatome

• Sensation is lost in the entire cutaneous field

• Sensation is unaffected

• Sensation is increased in the cutaneous field

Which nerves are affected if the upper trunk of the brachial plexus is injured?

• C5 and C6

• C7 and C8

• T1 and T2

• C8 and T1

What is the result of injuring two ventral rami that make up the lower trunk?

• Loss of sensation in C5 and C6 dermatomes

• Loss of sensation in C6 and C7 dermatomes

• Loss of sensation in C8 and T1 dermatomes

• Loss of sensation in C7 and T2 dermatomes