Question

need to know a, b, c and, d

A. decribe the various types of cells of the nervous system and their functions.

B. describe the components of a typical neuron. why are there so many dendrites but typically only one axon?

C. describe the components of the reflux arc. are they all "simple"

D. describe what is meant by an action potiental and show me how it works in the nervous conduction

Answer 1

A. The nervous system have two types of cells : glial cells and neurons or nerve cells.

The neurons helps in transmission of signal through it, while the glial cells helps in providing structural support to the neurons, insulating neurons, nourishes neurons and removal of waste products from neurons.

B. A typical neuron has dendron, cell body and axon as its main components. Besides it, the neuron also has Nissl's granules, Schwann cells, myelin sheath and node of Ranvier.

The dendron of the neuron branches to form dendrites which receives the signals from from other neurons through synapse formation or from the sensory receptors. The cell body contains nucleus and hence controls all the functions of the neuron. It also receives signal from the dendron and transmit it through the axon. The cell body has Nissl's granules which synthesizes proteins, these proteins maintain the structure of the neuron by replacing the broken out proteins of the neuron. The axon carries signal away from the neuron towards other neurons. The axon terminal (branch of axon) forms synapse with other neurons and transmit signal from one neuron to another. The Schwann cells helps in maintaining the physical integrity of the synapse by strengthening them. The Myelin sheath helps in transmission of signal at High speed in a neuron. It insulates the flow of ions in the axon and hence ion exchange takes place at the node of Ranvier and the presence of myelin sheath increase the rate of transmission of signal in a neuron.

C. The reflex arc has components like, the receptor organ ( which receives the signals), the sensory neuron ( which carry out the signals to the CNS) , the inter neuron ( joints the sensory neuron with the motor neuron), the motor neuron ( carry the signals from CNS to the effector organs) and the effector organs ( which carry out the required action against the stimulus).

Some reflex arc gets completed in the spinal cord of the CNS which are simple, but some gets completed in the brain of the CNS, which are generally not of simple type.

D. Generally the nerve membrane is more permeable to Sodium ions than potassium ions. Hence the sodium ions flows outside the membrane making a charge difference across the membrane known as resting membrane potential. When the neuron gets any signal, the permeability of the membrane changes at the site where the signal has been given and makes the inner side of neuron positive. This changes the potentiality of the membrane from-70mV to +30 mV and is called as action potential. Than the positive charge inside the membrane flows to the nearby area away from the cell body and the nearby becomes depolarised and it is called as transmission of signal. While the previous area becomes depolarised. In this way the nerve signal transmit along a neuron.