21) Most CNS neurons lack centrioles. This observation explains A) why CNS neurons cannot regenerate. 8) why CNS neurons grow such long axons. C) the ability of neurons to generate an action potential. D) the ability of neurons to produce a resting potential. E) the ability of neurons to communicate with each other. 22) Damage to ependymal cells would most likely affect the A) formation of ganglia. B) formation of myelin sheaths. C) formation of cerebrospinal fluid. D) transport of neurotransmitters within axons. E) repair of axons.
The Correct Answer and Explanation is :
21) The correct answer is A) why CNS neurons cannot regenerate.
Explanation:
Centrioles are essential for cell division, as they play a key role in organizing the mitotic spindle during mitosis. In most neurons of the central nervous system (CNS), centrioles are absent, and these neurons typically do not undergo mitosis after they have differentiated. This lack of centrioles in CNS neurons means that they are unable to divide and proliferate. When neurons in the CNS are damaged, they generally cannot regenerate, unlike neurons in the peripheral nervous system (PNS), which have the capacity to regenerate to some extent.
The inability of CNS neurons to regenerate after injury is one of the major reasons for the limited ability of the CNS to recover from damage. While peripheral neurons can repair themselves to some degree, CNS neurons do not possess the necessary machinery for regeneration due to the absence of centrioles, which prevents them from dividing and forming new functional neurons in response to injury. This limitation contributes to conditions such as spinal cord injuries or neurodegenerative diseases, where the CNS’s inability to regenerate results in permanent deficits.
22) The correct answer is C) formation of cerebrospinal fluid.
Explanation:
Ependymal cells are specialized glial cells that line the ventricles of the brain and the central canal of the spinal cord. Their primary function is to produce and circulate cerebrospinal fluid (CSF), which serves as a protective cushion for the brain and spinal cord. CSF also helps to remove metabolic waste from the CNS and maintains the chemical stability of the environment.
If ependymal cells were damaged, the production of CSF could be compromised, leading to conditions like hydrocephalus, where the flow of cerebrospinal fluid is blocked or impaired. This can result in an accumulation of CSF, causing increased pressure on the brain, which can lead to damage and neurological deficits. The other options are incorrect because ependymal cells do not participate in the formation of ganglia, myelin sheaths, or the transport of neurotransmitters.