Answer
Nervous and muscular tissues are called "excitable tissues" because they exhibit a heightened and specialized form of excitability that goes beyond the basic excitability found in all living cells. While it is true that all living cells have some degree of excitability, which refers to their ability to respond to various stimuli, nervous and muscular tissues have evolved to be exceptionally excitable in order to perform specific functions.
Here's why these tissues are referred to as excitable:
1. **Specialized Function**: Nervous tissue, such as neurons, is designed to transmit electrical signals (action potentials) rapidly over long distances. Muscular tissue, both skeletal and cardiac, is responsible for generating mechanical force through contraction. These specialized functions require a higher degree of responsiveness to stimuli than what is typically seen in other cell types.
2. **Voltage-Gated Ion Channels**: Nervous and muscular tissues possess specialized ion channels, like voltage-gated sodium and potassium channels, which allow them to rapidly change their membrane potential in response to specific stimuli. This enables them to generate and propagate electrical signals efficiently.
3. **All-or-None Response**: Excitability in these tissues often results in an "all-or-none" response. When a stimulus reaches a threshold, a full-fledged response is triggered. In contrast, many other cell types may exhibit graded responses to stimuli.
4. **Rapid and Coordinated Responses**: Nervous tissue allows for rapid communication and coordination throughout the body, facilitating functions like perception, thought, and motor control. Muscular tissue enables quick and precise movements and contractility of the heart, crucial for circulation.
In summary, while all living cells are excitable to some extent, nervous and muscular tissues have evolved specialized mechanisms and properties that make them exceptionally excitable to perform their unique and critical functions in the body. This is why they are specifically referred to as "excitable tissues" in biology.
Work Step by Step
Nervous and muscular tissues are called "excitable tissues" because they exhibit a heightened and specialized form of excitability that goes beyond the basic excitability found in all living cells. While it is true that all living cells have some degree of excitability, which refers to their ability to respond to various stimuli, nervous and muscular tissues have evolved to be exceptionally excitable in order to perform specific functions.
Here's why these tissues are referred to as excitable:
1. **Specialized Function**: Nervous tissue, such as neurons, is designed to transmit electrical signals (action potentials) rapidly over long distances. Muscular tissue, both skeletal and cardiac, is responsible for generating mechanical force through contraction. These specialized functions require a higher degree of responsiveness to stimuli than what is typically seen in other cell types.
2. **Voltage-Gated Ion Channels**: Nervous and muscular tissues possess specialized ion channels, like voltage-gated sodium and potassium channels, which allow them to rapidly change their membrane potential in response to specific stimuli. This enables them to generate and propagate electrical signals efficiently.
3. **All-or-None Response**: Excitability in these tissues often results in an "all-or-none" response. When a stimulus reaches a threshold, a full-fledged response is triggered. In contrast, many other cell types may exhibit graded responses to stimuli.
4. **Rapid and Coordinated Responses**: Nervous tissue allows for rapid communication and coordination throughout the body, facilitating functions like perception, thought, and motor control. Muscular tissue enables quick and precise movements and contractility of the heart, crucial for circulation.
In summary, while all living cells are excitable to some extent, nervous and muscular tissues have evolved specialized mechanisms and properties that make them exceptionally excitable to perform their unique and critical functions in the body. This is why they are specifically referred to as "excitable tissues" in biology.
