At resting potential (polarized phase), the inside of the plasma membrane is negatively charged ($-70$ mV). As the stimulus reaches, it becomes positively charges ($+45$ mV, depolarized phase). As impulse passes away, it regains its original ionic distribution and again becomes negatively charged.

During the transmission of nerve impulse through a nerve fibre, the potential on the inner side of the plasma membrane is the First negative, then positive and again back to negative.

So, the correct answer is 'First negative, then positive and again back to negative'.

Myoglobin is present in 'all muscle fibres'.

Externally the body wall of earthworm is covered by a thin non cellular cuticle below which lies the epidermis two muscle layers (circular and longitudinal) and innermost coelomic  epithelium.

A new device referred as neurobridge, have been discovered that can by pass the signals from brain to the limbs with the help of electric signals. For the very first time, such device have been developed which helps to reconnect the brain directly to the muscles allowing voluntary and funcutional control of a paralyzed limb. 

For nerve impulses to be generated and carried, nerve cells should be in contact with each other. The nerve impulse is transmitted in the following sequence:  Axon end- synapse- dendrites- dendron- cyton- axon body- axon end. A nerve impulse travels in a form of electrical charge from axon end to the synapse. Here, the electrical impulse is converted to the chemical impulse in the synaptic cleft. Further this nerve impulse flows from synaptic cleft to dendritic tips, converting the chemical impulse to electrical impulse. Thus, the flow of impulse always flows from one axonal end of a neuron to another dendronal head of a neuron. So, the correct answer is option C.

For nerve impulses to be generated and carried, nerve cells should be in contact with each other. The nerve impulse is transmitted in the following sequence: 
Axon end- synapse- dendrites- dendron- cyton- axon body- axon end. A nerve impulse travels in a form of electrical charge from axon end to the synapse. Here, the electrical impulse is converted to the chemical impulse in the synaptic cleft. Further this nerve impulse flows from synaptic cleft to dendritic tips, converting the chemical impulse to electrical impulse. Thus, the flow of impulse always flows from one axonal end of a neuron to another dendronal head of a neuron. So, the correct answer is option D.

Conduction of nerve impulse is faster in myelinated fibres as myelin is an insulating layer or sheath, that forms around nerves, including those in the brain and spinal cord which protect and insulates the axons thus enhance the transmission of electrical impulses.

Axon is the long slender part of the neuron. It conducts nerve impulse from the dendron towards the synapse. So, option D is the correct answer.

The gap between 2 neurons is called synapse. This signal between two neuron is passes when this synapse is filled with neurotransmitter. The size of the synapse ranges from 2-20 nm.

Answer is option A i.e. "Na+ into the cell"
In the resting state of the nerve cell, the cytoplasm inside the axon has a high concentration of K+ and a low concentration of Na+. While, the surrounding fluid outside the axon and cytoplasm, has a low concentration of K+ and a high concentration of Na+. Thus, if diffusion occurs, then through concentration gradient the Na+ enters into the nerve cell.

Each myofibril shows dark and light bands' The dark bands of the myofibril are termed as A-bands or anisotropic bands.

During muscle fatigue due to deposition of lactic acid, cytoplasm becomes acidic thereby enzyme activity stops and food is not oxidised and as the energy is not available, muscular contraction stops.

The nerve impulses are generated at the sensory receptor and are carried towards the CNS through the sensory neuron. The The nerve impulse is transmitted through the axon of one neuron to the dendrite of the other neuron. At the axonic end, there are telodendrons which release the neurotransmitters which flow through the synapse to the dendrite of the other neuron. 

A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body.  We have 31 pairs of spinal nerves and they are named after the section of the spine they come out of.

The nervous system uses electrical impulses to transmit messages. Neurons conduct electrical impulses by generating the action potential. Action potential is generated through the flow of positively charged ions across the neuronal membrane.

A nerve impulse travels in a form of electrical charge from a neuronal axon end to the synapse. Here, the electrical impulse is converted to the chemical impulse in the synaptic cleft. Further, this nerve impulse flows from synaptic cleft to dendritic tips, converting the chemical impulse to electrical impulse. The neurotransmitters required is synthesised only by axon terminals and the receptors required to detect these chemical transmitters are only present on the dendritic ends. Thus, the impulse always flows from one axonal end of a neuron to another dendron head of a neuron. 

Dendrites are the small extension of nerve cells that receives signals from sensory receptors or other neurons.

Saltatory conduction is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.

The correct match can be represented as-

So, the correct option is '1-b-i, 2-c-iii, 3-d-iv, 4-a-ii'.

An electroencephalogram (EEG) is a test, that measures and records the electrical activity of the brain. Beta waves have a frequency of 13 to 30 cycles per second. These waves are normally found, when person is alert or have taken high doses of certain medicines, such as benzodiazepines.

There are different forms of synapse depending on the position of the synapse. When the synapse occurs in the axon, the synapse is known as the axoaxonic synapse. The nerve impulse conduction takes place from one axon to the other axon. The nerve impulse is transferred from the axon of one neuron to the axon of the other neuron. In this process, the direction of nerve impulse is reversed from axon to dendron to the axon to axon. 

A delta wave is a high amplitude brain wave. Delta waves are usually associated with the deep stage 3 of NREM sleep, also known as slow-wave sleep (SWS) and aid in characterizing the depth of sleep.

A nerve impulse is a way nerve cells (neurons) communicate with one another. Nerve impulses are mostly electrical signals along the dendrites to produce a nerve impulse or action potential. The action potential is the result of ions moving in and out of the cell.
A nerve impulse travels from the dendritic end towards the axonal end. The chemicals released from the axonal end of one neuron cross the synapse and generate a similar electrical impulse in a dendrite of another neuron. A neuron transmits electrical impulses not only to another neuron but also to muscle and gland cells.

Nerve impulses are conducted with great velocity. In mammalian nerve, the speed of conduction may be as high as 100 meters per second.

Increased axon diameter in axons leads to increase action potential velocity. As there is an increase in diameter of a fibre, its internal resistance decreases. The internal resistance decreases faster relative to the membrane resistance - therefore the distance the membrane potential can travel is increased by an increased diameter. So, the correct answer is option B.

Myelin is an insulating layer or sheath, that forms around nerves, including those in the brain and spinal cord. It is made up of protein and fatty substances. The purpose of the myelin sheath is to allow electrical impulses to transmit quickly and efficiently along the nerve cells. Nerve impulses cannot pass through the myelination, so they jump from one node of Ranvier to the next. If the whole nerve becomes myelinated then the conduction will be stopped.

The speed with which the nerve impulse is conducted by axon is known as nerve conduction velocity. The speed of nerve conduction does not depend on the diameter of axon only rather it depends on the diameter of the nerve fibre. The diameter of nerve fibre is axon, neurilemma, and myelin sheath in myelinated axons while axon and neurilemma in unmyelinated fibre. Conduction velocity is high in myelinated nerve fibre with the greater diameter. So, the given statement is false.

Neurons send messages through electrical impulses called as nerve impulses. The nerve impulse is due to the changes occurring across the cell membrane. Cell membranes contain a sodium-potassium pump. The concentration of sodium and potassium ions is different across the membrane. This difference causes a voltage difference between the inside of the neuron and its surroundings. This is called as the resting membrane potential. The membrane potential is always negative inside the cell. The sodium and potassium channels in the cells are voltage-gated, meaning they can open and close depending on the voltage across the membrane. During action potential, permeability of the nerve cell membrane changes for both sodium and potassium ions. During depolarization, there is influx of sodium ions which makes inside of the cell positive. Depolarization is followed by repolarization during which the outflux of potassium ions takes place which makes inside of the cell negative. The whole process results in the propagation of a nerve impulse.