Functional anatomy of the synapse A typical motor neuron (efferent neuron) shown under electron microscope numerous (average about 6000) small knobs spread over the surface of the dentrites (80-90%) and soma (10-20%).  These knobs are the ends of nerve fibrils that have their origin in many other neurons (usually not more than a few derived […]

Properties of Impulse and stimulus All or nothing principle The principle operates in the membrane excitation of the fibers i.e. once an action potential has been elicited at any point on the membrane of a normal fiber, the depolarization process travels over the entire membrane. This is called the all or nothing principle of membrane

The Voltage – gated Potassium channel The Voltage – gated Potassium channel has only one gate at the interior of the membrane and closes or opens to the interior of the cell.  The opening of the gate is referred to as activation. The gate operates in two stages: Resting stage During the stage the gate

The voltage-gated sodium channel Voltage-gated channels of the Cell Membrane There are two separate and specific voltage-gated channels, one for Na+ and the other for the K+. The principle operator of the stages of action potential ie. causing the depolarization and repolarization of the membrane is the so called voltage-gated Sodium channel.  However, the voltage-gated potassium

Action potential of Nerve and Muscle fibers The action potentials are the rapid changes in the resting membrane potential.  Nerve signals are transmitted by action potentials. Each action potential begins with a sudden change from the normal resting negative potential to a positive potential, and ends with an equally rapid change back again to normal

Resting potentials of nerve and muscle Fibers In the resting state of membrane i.e. the state under which the membrane of the nerve or muscle fibers is not transmitting signals, the fluid inside the nerve or muscle cells has greater concentration of K+ and the fluid outside the Na+. The potential across the membrane is a

Principles of membrane potential Basic Physics of Membrane potential In the tissue the fluid outside (interstitial fluid) and inside (intracellular fluid) are electrolytic solutions, containing 150 to 160 mEq / litre of positive ions (cations) and the same concentration of negative ions (anions).  Generally a very small excess of negative ions accumulate immediately inside the cell

Properties of nerve fibers Stimulus Nerve fibers have ability of nerve fibre to respond to stimulus. It is an external agent that brings about visual response. It can be also be from within and can elicit response which can not be visualized. Types of stimulus Electrical: this is the most common stimulus to bring about neuronal

Classification of Nerve fibers Nerve fibers are classified as Type A, Type B and Type C fibers based on the diameter, myelination and propagation speed. According to the diameter of the fiber, a physiological property of nerve fiber varies. As diameter increases, the conduction velocity increases which requires lower threshold of excitation with greater magnitude of response. Time of

Nerve fibers Nerve fibres are axons of neurons which can be either insulated or naked. Insulation is provided by sheaths which may be either myelin sheath of lipoid layer or thin tubular covering of neurilemma or schwann sheath. The nerve fibres with myelin sheath are known as myelinated and those without myelin sheath are known as unmyelinated fibres. Myelinated fibres