Question

1. In a study of a toddler with delayed motor response, scientists detect a gene mutation that affects the efferent or motor neurons that carry impulses away from the central nervous system (CNS). Scientists discover that this mutation has caused gaps between the nodes of Ranvier and the myelin sheaths of the axons. (a) Explain how this defect in axon structure may have caused a delay of motor response in the toddler? (b) Give an example of a disease that causes a defect in axon structure.

2. The brain is the central hub of signal activity, taking in information and deciding what to do with it. (a) Discuss the ancestral history of the brain of the chordate. (b) Explain what indications an analysis of a postmortem forebrain can reveal about an individual’s cognitive ability.

Answer 1

1. a. A gap in the myelin sheath and nodes of Ranvier might have varied the length such that the transmission was not possible due to disturbed channels and transport proteins and no impulse was sent forward.

B. Multiple sclerosis

2. a the ancestral brain had notochord, neural tube and other similar structures to the embryonic brain of human. This is an indication of further development and occurence if complex processes which led to the development.

B. Neurobiological studies as a part of postmortem simply reveal different type of lesion in the forebrain which might have relation with the impairment of cognition.