Nervous System and Neurons

Myasthenia gravis is an autoimmune disease where antibodies block or destroy acetylcholine receptors at the neuromuscular junction. This prevents muscle contraction signals from being effectively received.

Lead is a neurotoxin that accumulates both in soft tissues and the bones, damaging the nervous system and causing brain disorders.

• Spinal cord and brain control all activities of our body. Spinal cord possesses nerves, which carry messages between the brain and the body.
•  The brain sends commands for the functioning of different organs of the body via nerves. 
• Therefore, they are made of nervous tissue. Hence, option B is correct.  

Cyton or cell body of a neuron possesses cytoplasm and nucleus. It contains many organelles, including granules called Nissl granules, which are composed largely of rough endoplasmic reticulum and free polyribosomes. Therefore, option D is correct. 

• The densely packed nerve cells present in the brain, spinal cord, and sense organs are called neurons. They are specialized for the conduction of nerve impulses and they are mainly of two types, sensory neurons, and motor neurons.

• The neurons are specialized for the conduction of nerve impulses. Conduction of nerve impulses is aided by synapse. 
• Synapse is a structure that allows a neuron to pass the electrical signal or chemical signal to another neuron. Therefore, option A is correct.  

• Dendrons are short, branched parts arising from cell body or cyton. Dendrons are many in number. 
• Neurolemma is the outermost nucleated cytoplasmic layer of Schwann cells. It surrounds the axon of the nerve cell. 
• Neurofibrils are long, thin, microscopic fibrils that run in every direction in the cell body and also extend in axon and dendrites. 
• Axon is a long, thin hair-like processes coming out of the cyton of a nerve cell. 

Cyton is a cell body of the neuron containing a nucleus, cytoplasm.   
Synapse is a structure that allows a neuron to pass an electrical signal or chemical signal to another neuron. 
Axon is a long, thin, hair-like process arising from the cell body of the neuron. 
A neuron is the functional unit of nervous tissue. It contains cyton or cell body, long, thin hair like the process called axon and many short branches called dendrites. Therefore, option C is correct. 

Dendrite is a short branched extension of a nerve cell, along which impulses received from other cells at synapses are transmitted to the cell body. A neuron is an electrically excitable cell that processes and transmits information through electrical and chemical signals. These signals between neurons occur via synapses, specialized connections with other cells. An axon is a long, slender projection of a nerve cell, or neuron, that typically conducts electrical impulses away from the neuron's cell body. Myelinated axons are known as nerve fibers. The function of the axon is to transmit information to different neurons, muscles and glands. A neutrophil is a type of white blood cell, a type of granulocyte, and a type of phagocyte. 

The neurotransmitter substance found between a motor neuron and a muscle cell is acetylcholine. In the autonomic nervous system, acetylcholine (ACh) is the neurotransmitter in the preganglionic sympathetic and parasympathetic neurons. ACh is also the neurotransmitter at the adrenal medulla and serves as the neurotransmitter at all the parasympathetic innervated organs. ACh is also the neurotransmitter at the sweat glands, and at the piloerector muscle of the sympathetic ANS. 

• The axon terminals are the end of axon fiber and located close to the dendrites of another neuron, forming a connection known as a synapse and allowing them to send messages from neuron to neuron with the help of neurotransmitter. 
• So, a nerve cell transmits it's impulse to another through its axons. 

In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron. Synapsis is the fusion of chromosome pairs at the start of meiosis. A cell junction (or intercellular bridge) is a type of structure that exists within the tissue of some multicellular organisms, such as animals. Cell junctions consist of multiprotein complexes that provide contact between neighbouring cells or between a cell and the extracellular matrix. Synapticula is one of the numerous calcareous processes which extend between, and unite, the adjacent septa of certain corals.

The myelin sheath of neurons provides them with an insulating covering. It allows rapid transmission of signals from the nervous system to the body and vice-versa. Any damage to the myelin sheath will cause hindrance and slowing down of the transmission of signals to the axons.

So, the correct answer is 'Action potentials would be conducted too slowly along the neurons'.