Cutaneous receptors Cutaneous receptors mediate sensation of touch, light, pressure, heat, and cold. These consist of lamellated connective tissue capsule that surrounds soft core where the axon ends. Pain sensations are mediated through the fine free nerve ending. Sensing light touch  Mediated by Meissner’s corpuscles, Merkel’s disc and basket arrangement of nerve fibers at the […]

Classification of sensory receptor Sensory receptors are classified based on- Function of the receptors, Location of receptors, Source of the stimulus and type of stimulus or modality. Function of the receptors Phasic receptors:  Produce action potential during part of stimulation hence they initiate response. It does not provide clue for duration of stimulus. Tonic receptors: 

Receptors in animals Receptors are specialized as neuronal structures to detect diverse stimuli from the internal and external environment. Receptor specificity Adequate stimulus is preferred, if large magnitude of stimuli that can provoke response from many receptors. Some receptors are designated by nature to respond to different stimuli. Example:  Nociceptors to detect pain which may be due

Synapse Neurotransmitters A transmitter cause excitation or inhibition is determined by- The transmitter released at the synaptic terminal and The nature of the receptor present in the post synaptic membrane.  A single neuron may either be excited or inhibited. When excited, a transmitter is released at the synaptic knob which acts on the post synaptic

Ionophore component There are two types of ionophores- Ion channels (chemically activated) and Second messenger system (enzymatically activated internal metabolic system). 1. Ion channels (chemically activated) Chemically activated ion channels (ligand-activated channels) are of three types- Sodium channels Allow mainly Na+ (Some K+ as well) Potassium channels Allow mainly K+ Chloride channels Allow Cl– and few other anions to

Synaptic Transmission of Impulse Structural properties common to all synaptic functions during Synaptic Transmission of Impulse. Synaptic cleft There is no continuity of the cytoplasm across  the synapse.  There is a synaptic cleft (200-300 micron width) between the pre and post synaptic membranes. Thickened and modified portions both on the synaptic knob membrane and post synaptic

Types of synapse Types of synapses is Chemical synapse and Electrical synapse. Chemical synapse All the synapses present in the central nervous system are chemical synapses.  In these, the first neuron secretes a chemical substance  called as a neurotransmitter at the synapse.  The transmitter travels and acts on receptor (protein in nature) present in the

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