The brain is the center of the nervous system. In most animals the nervous system is divided into central and peripheral nervous system. The major parts of the nervous system are brain, spinal cord, ganglia, and nerves. Neurons, the basic unit of nervous tissue, send signals to all the cells in the form of electrochemical waves which travel along thin fibers called axons. These signals cause chemicals called neurotransmitters to be released at junctions called synapses. A cell that receives a signal may be excited, inhibited, or otherwise modulated.
Neurotransmitter molecules are stored in membranous sacs called vesiclesin the axon terminal. Each vesicle contains thousands of molecules of a neurotransmitter. Neurotransmitters can be Excitatory or Inhibitory.
Neurons secreting gamma - aminobutyric acids (GABA) as their primary neurotransmitter are called GABA neurons. GABA is an inhibitory neurotransmitter i.e., it inhibits whichever neurons its binds to.These neurotransmitters are binded with membrane proteins called as Receptors. Neurotransmitter binds only to a specific receptor thereby GABA neurotransmitters bind with only GABA Receptors. Subclasses of GABA neurons differ in their morphological, biochemical, and functional characteristics, indicating that they likely play distinct roles in regulating cortical circuitry.
Binding of neurotransmitters causes the opening of ion channels. This allows the flow of either negatively-charged chloride ions into the cell or positively-charged potassium ions out of the You do not have access to view this node. Usually resulting in hyperpolarization
Three general classes of GABA receptor are known: GABA A, GABA B and GABA C receptors. The GABA A and GABA C are ionotropic receptors and GABA B metabotropic receptors.
In the neurons of vertebrate, chloride ions are pumped out of the You do not have access to view this node. On activating GABA receptors chloride ions diffuse into You do not have access to view this node, hyperpolarize the membrane and decrease the excitability of the You do not have access to view this node. This inhibition is called hyperpolarizing inhibition. In some You do not have access to view this node, internal chloride concentration is higher than the equilibrium potential. In these cases, opening chloride channels caused an efflux of this anion, creating an inward current, and depolarizing the membrane. This type of inhibition is called depolarizing inhibition. Thus, activation of GABA receptors will inhibit cell activity whether it hyperpolarizes or depolarizes the You do not have access to view this node.
GABA binding to the GABA B receptor stimulates the opening of K+ channels to bring neurons to equilibrium potential of K+, hyperpolarize the neuron membrane. This stops the firing of action potentials so stops neurotransmitter release. Thus GABAB receptors are considered inhibitory receptors.
GABA C receptors :
GABA binding to the GABA C receptor results in opening of the chloride channel. Chloride ions flow into the cell is trigered when the reversal potential of chloride ions is less when compared to membrane potential. This influx of chloride ions lowers the membrane potential of the neuron. This stops the firing of action potentials.