Chapter 12 - Section 12.2 - Study Guide - Assess Your Learning Outcomes - Page 471: 3

A generalized multipolar neuron is one of the most common types of neurons found in the nervous system. It consists of several distinct parts, each with specific functions. Here are the main parts of a generalized multipolar neuron and their functions: 1. **Cell Body (Soma):** - **Function:** The cell body contains the nucleus and most of the cell's organelles, including the endoplasmic reticulum and Golgi apparatus. It is responsible for metabolic processes and protein synthesis necessary to maintain the neuron's structure and function. 2. **Dendrites:** - **Function:** Dendrites are short, branched extensions that protrude from the cell body. They serve as the primary site for receiving incoming signals from other neurons or sensory receptors. Dendrites contain receptors and synaptic terminals where neurotransmitters from other neurons can bind and initiate electrical changes in the neuron. 3. **Axon:** - **Function:** The axon is a long, slender projection that extends away from the cell body. It is responsible for transmitting electrical signals (action potentials) away from the cell body and toward other neurons, muscles, or glands. The axon is covered by a myelin sheath in many cases, which helps increase the speed of signal conduction. 4. **Axon Hillock:** - **Function:** The axon hillock is a specialized region at the base of the axon, adjacent to the cell body. It plays a crucial role in determining whether an action potential is generated in response to incoming signals. If the electrical signals from the dendrites and cell body reach a threshold level at the axon hillock, an action potential is initiated. 5. **Axon Terminal (Synaptic Terminal or Bouton):** - **Function:** At the end of the axon, there are numerous axon terminals that form synapses with other neurons or effector cells, such as muscles or glands. These terminals release neurotransmitters when an action potential reaches them, transmitting signals to the postsynaptic cell. 6. **Myelin Sheath (in some neurons):** - **Function:** In many neurons, the axon is insulated by a myelin sheath, which is formed by glial cells (oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system). The myelin sheath acts as an insulator, allowing for faster conduction of action potentials by jumping between nodes of Ranvier along the axon. 7. **Nodes of Ranvier:** - **Function:** Nodes of Ranvier are small gaps in the myelin sheath along the axon. Action potentials "jump" from one node to another, which speeds up the propagation of electrical signals down the axon. 8. **Synaptic Cleft:** - **Function:** The synaptic cleft is the tiny gap between the axon terminal of one neuron and the dendrites or cell body of another neuron or target cell (e.g., muscle or gland). Neurotransmitters are released into this gap to transmit signals from one neuron to the next. In summary, a generalized multipolar neuron consists of a cell body that contains the nucleus and organelles, dendrites for receiving signals, an axon for transmitting signals, axon hillock for action potential initiation, axon terminals for synaptic transmission, and often a myelin sheath for insulation and faster signal conduction. These components work together to enable the neuron to receive, process, and transmit information within the nervous system.

A generalized multipolar neuron is one of the most common types of neurons found in the nervous system. It consists of several distinct parts, each with specific functions. Here are the main parts of a generalized multipolar neuron and their functions: 1. **Cell Body (Soma):** - **Function:** The cell body contains the nucleus and most of the cell's organelles, including the endoplasmic reticulum and Golgi apparatus. It is responsible for metabolic processes and protein synthesis necessary to maintain the neuron's structure and function. 2. **Dendrites:** - **Function:** Dendrites are short, branched extensions that protrude from the cell body. They serve as the primary site for receiving incoming signals from other neurons or sensory receptors. Dendrites contain receptors and synaptic terminals where neurotransmitters from other neurons can bind and initiate electrical changes in the neuron. 3. **Axon:** - **Function:** The axon is a long, slender projection that extends away from the cell body. It is responsible for transmitting electrical signals (action potentials) away from the cell body and toward other neurons, muscles, or glands. The axon is covered by a myelin sheath in many cases, which helps increase the speed of signal conduction. 4. **Axon Hillock:** - **Function:** The axon hillock is a specialized region at the base of the axon, adjacent to the cell body. It plays a crucial role in determining whether an action potential is generated in response to incoming signals. If the electrical signals from the dendrites and cell body reach a threshold level at the axon hillock, an action potential is initiated. 5. **Axon Terminal (Synaptic Terminal or Bouton):** - **Function:** At the end of the axon, there are numerous axon terminals that form synapses with other neurons or effector cells, such as muscles or glands. These terminals release neurotransmitters when an action potential reaches them, transmitting signals to the postsynaptic cell. 6. **Myelin Sheath (in some neurons):** - **Function:** In many neurons, the axon is insulated by a myelin sheath, which is formed by glial cells (oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system). The myelin sheath acts as an insulator, allowing for faster conduction of action potentials by jumping between nodes of Ranvier along the axon. 7. **Nodes of Ranvier:** - **Function:** Nodes of Ranvier are small gaps in the myelin sheath along the axon. Action potentials "jump" from one node to another, which speeds up the propagation of electrical signals down the axon. 8. **Synaptic Cleft:** - **Function:** The synaptic cleft is the tiny gap between the axon terminal of one neuron and the dendrites or cell body of another neuron or target cell (e.g., muscle or gland). Neurotransmitters are released into this gap to transmit signals from one neuron to the next. In summary, a generalized multipolar neuron consists of a cell body that contains the nucleus and organelles, dendrites for receiving signals, an axon for transmitting signals, axon hillock for action potential initiation, axon terminals for synaptic transmission, and often a myelin sheath for insulation and faster signal conduction. These components work together to enable the neuron to receive, process, and transmit information within the nervous system.