Question

Nervous tissue is made up of neurons and neuroglial cells. Which of the following statements about these two cells is/are false? (i) Neuroglia make up more than one-half the volume of neural tissue in our body. (ii) Neuroglia protect and support neurons. (iii) When a neuron is suitably stimulated, an electrical disturbance is generated which swiftly travels along its cytosol. (iv) Arrival of the disturbance at the neuron's endings triggers stimulation or inhibition of adjacent neurons or other cells. (a) (i) and (iv) (b) (ii) and (iii) (c) (iii) only (d) (iv) only

Short answer

The false statement is (iii) only.

Step-by-step solution

Understanding Neuroglia

Neuroglia, or glial cells, constitute a significant portion of the nervous system and are responsible for protecting and supporting neurons. This implies that statement (ii) is true as it accurately reflects the role of neuroglia.

Assessing the Volume of Neural Tissue

Neuroglia indeed account for more than half the volume of neural tissue in the human body. This means that statement (i) is true and therefore cannot be the false statement we are seeking.

Analyzing Neuron Stimulation

When stimulated, a neuron generates an electrical signal called an action potential which travels along its axon, not cytosol. This indicates that statement (iii) contains an inaccuracy regarding the location of the electrical disturbance's travel, making it the false statement.

Propagation of the Signal

Statement (iv) correctly describes the transmission of nerve impulses and the triggering of stimulation or inhibition of adjacent cells. Therefore, (iv) is a true statement about neuronal function.

Key concepts

Neuroglia

Neuroglia, commonly known as glial cells, are the supportive and protective cells of the nervous system. Unlike neurons, neuroglia do not conduct electrical impulses but play a crucial role in maintaining homeostasis, forming myelin, and providing support and protection for neurons. They account for more than half the volume of neural tissue, which serves as an indicator of their abundance and importance.

Within the brain and spinal cord, neuroglia perform several critical functions. For instance, astrocytes maintain the blood-brain barrier, regulate nutrient and ion concentrations, and repair the nervous system after injuries. Another type, oligodendrocytes, are responsible for myelinating the axons of neurons within the central nervous system which increases the speed of electrical conduction. In the peripheral nervous system, similar myelinating duties are performed by Schwann cells. Microglia, acting as resident immune cells, protect against pathogens and clear away debris. These diverse roles highlight the essential nature of neuroglia in ensuring the proper functioning of the nervous system.

Neurons

Neurons are the fundamental working units of the nervous system, designed to quickly respond to stimuli and transmit signals throughout the body. Each neuron consists of three main parts: the cell body, dendrites, and an axon. The cell body, or soma, contains the nucleus and is the metabolic center. Dendrites extend from the cell body and receive signals from other neurons, while the axon is responsible for carrying electrical impulses away from the cell body to other neurons or effector cells.

The neuron is unique in its ability to generate an action potential, which is an essential function of the nervous system. This process is a finely tuned sequence of electrochemical events leading to the transmission of the nerve impulse. After the action potential travels down the neuron's axon, it reaches the axon terminals, which can then synapse with another neuron or effector cell, facilitating communication within the nervous system.

Action Potential

An action potential is a fundamental physiological process that allows neurons to communicate. It’s an electrical signal that forms when a neuron is sufficiently stimulated, triggering a rapid change in the electrical charge across the neuron's membrane. This begins with the opening of sodium channels and a sudden influx of sodium ions, followed by repolarization due to the efflux of potassium ions.

As the impulse travels down the axon, it maintains its strength due to the all-or-nothing principle. Essentially, once triggered, the action potential will travel the length of the neuron without losing intensity. At the synapse, the action potential causes the release of neurotransmitters into the synaptic cleft. These chemicals cross the gap to the next neuron or effector cell, thereby propagating the signal or action that the neuron was meant to convey.

Nervous System

The nervous system is an intricate network of neurons and neuroglia that governs an organism's interactions with the internal and external environments. It's primarily divided into two main parts: the central nervous system (CNS), composed of the brain and spinal cord, and the peripheral nervous system (PNS), which includes all neural tissue outside the CNS. The CNS is the control center, processing information and dictating actions, while the PNS acts as the communication lines, relaying signals between the CNS and the rest of the body.

The nervous system performs multiple functions including sensory input processing, data integration, and commanding body responses. Sensory neurons carry information to the CNS, interneurons interpret the information, and motor neurons relay commands from the CNS to muscles and glands. The neuroglia support these processes by creating an environment that allows for efficient signal transmission. Understanding the nervous system is crucial for comprehending how we interact with our surroundings, how we think, move, and experience emotions.