Neural Anatomy and Impulse Transmission PDF

1 Structure of a Neuron Dendrites are the short branching extensions of a neuron that receive nerve impulses from other neurons and relay impulses toward the cell body. The cell body processes the received input and relays them forward. ▹ contains the nucleus and is...

1 Structure of a Neuron Dendrites are the short branching extensions of a neuron that receive nerve impulses from other neurons and relay impulses toward the cell body. The cell body processes the received input and relays them forward. ▹ contains the nucleus and is the site of metabolic reactions in the cell The axon is the extension of a neuron, which conducts the impulse away from the cell body towards other neurons. ▹ range in length from 1mm to 1m 2  SOME neurons are enclosed in a 3 fatty insulating layer called the myelin sheath. Myelinated axons are protected and have a higher rate of nerve impulse transmission. Myelin is formed by Shwann cells, which wrap themselves around the axon. 4 CNS PNS Myelinated neurons form white Most neurons are myelinated. matter. Unmyelinated neurons form grey matter. 5 Cell Membrane Potential Resting Potential | Threshold Potential | Action Potential The nerve impulse is a weak electric current, like a wave.  1. Neuron membrane maintains 6 resting potential. 2. Threshold stimulus is received. 3. Sodium channels open. 4. Sodium ions diffuse inward, depolarizing the membrane. 5. Potassium channels open. 6. Potassium ions diffuse outward, repolarizing the membrane.  7. The resulting action potential causes a local bioelectric 7 current that stimulates the membrane. 8. Wave of action potentials travel the length of the axon as a nerve impulse. 8 Ions inside and outside of the cell create positive and negative sides, which produces an electric current. 9 Depolarization Depolarization results when there is a loss of the difference in charge between the inside and outside of the plasma membrane of a muscle or nerve cell due to a change in permeability and migration of sodium ions to the interior. 10 Check-in Question Sketch and label the following action potential curve with the following terms: repolarization, refractory period, depolarization, resting potential 5 4  Action Potential! 11 Check-in Question (answer) depolarization repolarization Sketch and label the following action potential curve with the following terms: repolarization, refractory period, depolarization, resting potential resting 5 potential resting 4 potential refractory period 12 13 14 Nerve Impulse Speed is proportional to the size of the axon. ▹ Greater diameter = faster impulse Remember, myelinated axons conduct impulses faster than unmyelinated ones. 15 Nerve Pathway To communicate with adjacent neurons, glands, or muscles, the axon terminals release chemical signals into the space between them and the dendrites of nearby cells. ▹ The connections between two neurons, or a neuron and an effector is called a synapse. ▹ The gap between two neurons is called a synaptic cleft.