Tag: plant and animal tissues

A neuron is an electrically excitable cell. It is the functional and structural unit of the nervous system. It processes and transmits information through electrical and chemical signals. These signals between neurons occur via synapses, specialized connections with other cells. Neurons can connect to each other to form neural networks. Neurons are the core components of the nervous system.

A centriole is a small set of microtubules arranged in a specific way. There are nine groups of microtubules. When two centrioles are found next to each other, they are usually at right angles. The centrioles are found in pairs and move towards the poles (opposite ends) of the nucleus when it is time for cell division. Neurons cannot divide because they lack centrioles.
Because centrioles function in cell division, the fact that neurons lack these organelles is consistent with the amitotic nature of the cell.

Sensory neurons receive sensory inputs from the internal and external environment by sensory nerves and transmit it to CNS (brain and spinal cord) for processing. This makes option A incorrect. 

A nerve is composed of nerve fiber bundles. A nerve fiber is a threadlike extension of a nerve cell and consists of an axon and myelin sheath (if present) in the nervous system. There are nerve fibers in the central nervous system and peripheral nervous system. A nerve fiber may be myelinated and/or unmyelinated. In the central nervous system (CNS), myelin is produced by oligodendroglia cells.
Muscle tissue is a soft tissue that composes muscles in animal bodies and gives rise to muscles ability to contract. This is opposed to other components or tissues in muscle such as tendons or perimysium.
Bundle sheath cells is a layer of cells in plant leaves and stem that forms a sheath surrounding the vascular bundles.

Dendrites are the small extension of nerve cells that receive signals from sensory receptors or other neurons. The nerve impulse is not conducted by them. The long extension of the cell body of the nerve cell is called as axon that serves to conduct the nerve impulse away from the cell body. The increased diameter of axon results in reduced resistance to local current flow which in turn causes the action potential at its one site to activate the adjacent site. Soma is the metabolic center of the nerve cell where the metabolic contents are manufactured. It is not involved in nerve impulse conduction. Thus, the correct answer is option B.

Schwann/Schwarm cells of peripheral nervous system form the myelin sheath around the myelinated fibers. Gaps between two Schwann cells form nodes of Ranvier which are the unmyelinated areas. Dendrites are the small extension of nerve cells that receive signals from sensory receptors or other neurons and brings them towards the cell body. The synaptic knob is the small button like structure present at the end of the axonal branch at the synapse and serves to store the neurotransmitters which are released in the synaptic cleft. The correct answer is A.

Dendrites are the small extension of nerve cells that receives signals from sensory receptors or other neurons through axon and brings them towards the cell body. Thus, the correct answer is option A.

Neurotransmitters are endogenous chemicals that enable the process of neurotransmission. They transmit signals across a chemical synapse from one neuron (nerve cell) to another "target" neuron, muscle cell, or gland cell. 

• The different cells in the body can regenerate in order to replace the damaged or the worn-out cells. 
• The neurons are one of the brain cells. The cells divide during the embryonal stage. After the birth of a child, the cells lose their capacity to divide. 
• These cells have the least capacity of regeneration. 
• Thus, the correct answer is option C. 

The axon can be defined as the long cytoplasmic process of the cell body, which transmits the impulse from the cell body to other neurons. The axon of the neuron is covered by a lipid-rich membrane, called myelin sheath. The myelin sheath is formed by Schwann cells and each Schwann cell covers a part of the axon.
Thus, the correct answer is the option D.