Motor cortex and motor neurons
We’ll begin our exploration of movement by examining the motor cortex, where signals for voluntary movement originate, along with the types of neurons involved in generating those signals.
1) Start with these videos:
2) Then, read this article: Know Your Brain - Motor Cortex
3) Read these articles for some historical context and an interesting discussion of a particular type of neuron that might be involved in certain types of movement:
History of Neuroscience - Fritsch and Hitzig and the Motor Cortex
Know Your Brain - Mirror Neurons
4) Finally, answer these questions to test your understanding:
1. Which of the following regions corresponds to the location of the motor cortex?
- A. central sulcus
- B. precentral gyrus
- C. fusiform gyrus
- D. postcentral gyrus
Show Answer
Correct answer: B
The primary motor cortex is found in the precentral gyrus.
2. This neural pathway is the main pathway for voluntary movement. When you perform an action like picking up an object, neurons in this pathway carry signals from the motor cortex down to the spinal cord to cause muscle contractions. Which pathway is it?
- A. vestibulospinal tract
- B. spinothalamic tract
- C. dorsal columns-medial lemniscus pathway
- D. corticospinal tract
Show Answer
Correct answer: D
The corticospinal tract is the main pathway for voluntary movement.
3. What two scientists are credited with discovering the motor cortex through their work with dogs?
- A. Hodgkin and Huxley
- B. Golgi and Sherrington
- C. Hubel and Wiesel
- D. Fritsch and Hitzig
Show Answer
Correct answer: D
The discovery of the motor cortex is primarily credited to Gustav Fritsch and Eduard Hitzig. In 1870, Fritsch and Hitzig conducted experiments with dogs that demonstrated part of the cerebral cortex was directly responsible for causing movement; that region of the cortex would eventually be known as the motor cortex.
4. When motor signals are sent from the motor cortex to control movements of the head and face, which pathway do they primarily follow?
- A. corticospinal tract
- B. spinocerebellar tract
- C. vestibulospinal tract
- D. corticobulbar tract
Show Answer
Correct answer: D
The corticobulbar tract carries motor commands from the cerebral cortex to the motor nuclei of cranial nerves in the brainstem, which control muscles of the head and face. In essence, it does for the head and face what the corticospinal tract does for the rest of the body.
5. Which of the following is a typical effect of lower motor neuron damage?
- A. spasticity
- B. over-responsive reflexes (hyperreflexia)
- C. weakness or paralysis
- D. increased muscle tone (hypertonia)
Show Answer
Correct answer: C
Lower motor neuron lesions often cause weakness or paralysis due to direct damage to the neurons that innervate skeletal muscle. This is frequently accompanied by decreased muscle tone and reduced or absent reflexes.
