Impulse transmission

IMPULSE TRANSMISSION VIA NERVE AND SYNAPSE.

1. PRESENTATION ON TRANSMISSION OF IMPULSE THROUGH NERVES AND SYNAPSE Submitted to: Presented by: Dr.D.K Sharma Bivek Rai Dept. of Zoology M.Sc II SEM

2. Nervous system It is a complex collection of nerves and specialized cells known as neurons that transmit signals between different parts of the body. It is a system that coordinates and controls the activities of the animals. The nervous system can be broadly divided into two sections: i.C entral nervous system ( CNS): It consists of the brain and the spinal cord. It is in the CNS that all of the analysis of information takes place. ii.Peripheral nervous system (PNS): It c onsists of the neurons and parts of neurons found outside of the CNS, includes sensory neurons and motor neurons

3. Components of Nervous System BRAIN SPINAL CORD SENSE ORGAN: EYES EAR etc NERVES

4. Neuron Neuron is an electrically excitable cell that receives, processes, and transmits information through electrical and chemical signals

5. Impulse Transmission T hrough N erves Nerve impulse is the electrical signal which is transmitted by neuron around the nervous system The nerve impulse travel quickly because they are electrical impulse and ranges from approximately 1m/s to 100m/s The inside of a neuron’s cell membrane is negatively-charged while the outside is positively charged When sodium and potassium ions change places, this reverses the inner and outer charges causing the nerve impulse to travel down the membrane

6. Resting potential The state of the neuron when no nerve impulse is being conducted During resting potential there is an ion displacement between the inside and the outside of the neuron (i.e. on either side of the neuron cell membrane) as follows: There are more Na+ ions on the outside than on the inside There are more K+ ions on the inside than on the outside

7. Action Potential An action potential occurs when a neuron is conducting a nerve impulse In order for an action potential to occur, the neuron must receive sufficient stimulation to open enough Na gates to reach the threshold level If sufficient Na gates are opened to reach the threshold level, other Na and K gates will be stimulated to open Action potential can be divided into 2 phases: Depolarization Repolarization

8. Depolarization If a neuron received sufficient stimulation to reach the membrane threshold, successive Na gates along the entire neuron membrane will open The opening of the Na gates allows Na ions to move into the neuron The movement of Na ions into the neuron causes the membrane potential to change from -70mV to + 40mV As the membrane potential becomes more positive, Na gates begin to close. At the end of depolarization, the Na gates are all closed

9. Repolarization At the end of the depolarization phase, K gates begin to open, allowing K to leave the neuron These K gates are activated at the +ve membrane potential value of about + 40mV The movement of K ions out of the neuron produces a change in membrane potential such that the potential becomes more – ve

10. Graphical Representation of I mpulse Transmission

11. The junction between two communicating neurons is called a synapse ; there exists a synaptic cleft between them across which the impulse must be conveyed. Synapse

12. Synaptic Transmission The process by which the impulse in the presynaptic neuron is transmitted across the synaptic cleft to the postsynaptic neuron is called synaptic transmission. Synaptic cleft : The space between two neuron is called synaptic cleft. It is approx. 20-55nm.

13. Action potential reaches axon terminal Calcium channel open Ca 2+ causes vesicles to release neurotransmitter Neurotransmitter crosses synapse cleft Neurotransmitter bind to neuroreceptors Triggers signals in post-synaptic neuron Steps of Synaptic Transmission

14. Overview of the process