I. Neurons/nerve cells A neuron is a cell specialized to conduct electrochemical impulses called nerve impulses or action potentials. Neuron is the main cellular component of the nervous system, a specialized type of cell that integrates electrochemical activity of the other neurons that are connected to it and that propagates that integrated activity to other neurons. They are the basic information processing structures in the CNS. There are as many as 10,000 specific types of neurons in the human brain, A. Types of Neurons a. Motor neurons >These transmit impulses from the central nervous system to the * muscles and * glands that carry out the response. >Most motor neurons are stimulated by interneurons, although some are stimulated directly by sensory neurons. b. Sensory neurons These run from the various types of stimulus receptors, e.g., to the central nervous system (CNS), the brain and spinal cord. * touch * odor * taste * sound * vision c. Interneurons Interneurons >are found exclusively within the spinal cord and brain. They are stimulated by signals reaching them from * sensory neurons * other interneurons or * both. > also called association neurons. B. Structure of Neurons a. Processes 1. Dendrite Dendritic connections are the basic receiving stations by which neurons form the signaling networks that constitute the brain's circuitry. 2. AxonsAll neurons outside the central nervous system (and many within it) conduct impulses along hairlike cytoplasmic extensions, the nerve fibers or axons. The axons connecting your spinal cord to your foot can be as much as 1 m long C. Development of Neurons A. life span D. Kinds of Neurons II. Nerve impulse ConductionFirst, an action potential is generated near the cell body portion of the axon III. Nerve impulse transmission A. Neurotransmitters a. Excitatory AcH b. Inhibitory AcH B. Synaptic transmission A. Synapse A synapse is where two neurons communicate electrically or chemically. A synapse is the junction point between two neurons.| | | | | |
Nerve cells consist of a body, with branches at one end. The branches are called axons. The axons are positioned near an adjacent nerve or a muscle. Nerve impulses pass from the axons of one nerve to the next nerve or muscle. The impulse transmission speed can be reduced in damaged nerves. Surrounding a nerve is a tough protective coat of a material called myelin. Nerve damage can involve damage or loss of myelin, damage to the nerve body, or damage to the axon region. The nerve conduction study, which was devised in the 1960s, can detect the loss of nerve function due to these injuries, and, from the nature of the nerve signal pattern that is produced, offer clues as to the nature of the problem. Depending on the nature of the nerve damage, the pattern of signal transmission can be different. For example, in a normal nerve cell, sensors placed at either end of the cell will register the same signal pattern. But, in a nerve cell that is blocked somewhere along its length, these sensors will register different signal patterns. In another example, in a nerve cell in which transmission is not completely blocked, the signal pattern at the axon may be similar in shape, but reduced in intensity, to that of the originating signal, because not as much of the signal is completing the journey...