Chapter 16 - Section 16.4 - Study Guide - Assess Your Learning Outcomes - Page 625: 10

The spiral organ, also known as the organ of Corti, is a crucial structure located within the cochlea of the inner ear. It plays a central role in the process of hearing by converting mechanical sound vibrations into electrical signals that the brain can interpret. The spiral organ contains specialized hair cells and the tectorial membrane, which are key components in this sensory transduction. **Hair Cells:** Hair cells are the sensory receptors of the spiral organ responsible for detecting sound vibrations and initiating the auditory signal. There are two types of hair cells within the organ of Corti: inner hair cells (IHCs) and outer hair cells (OHCs). 1. **Inner Hair Cells (IHCs):** IHCs are the primary sensory receptors responsible for transmitting auditory signals to the brain. They are arranged in a single row along the length of the organ of Corti and are positioned closer to the central axis of the cochlea. Each IHC is equipped with specialized hair-like protrusions called stereocilia, which are embedded in the tectorial membrane above them. 2. **Outer Hair Cells (OHCs):** OHCs are situated in multiple rows and are positioned on the outer side of the IHCs. These cells play a role in amplifying and fine-tuning sound vibrations in the cochlea. OHCs also have stereocilia that are connected to the tectorial membrane. The stereocilia of OHCs are arranged in a unique "W" or "V"-shaped pattern. **Tectorial Membrane:** The tectorial membrane is a gel-like structure that extends above the hair cells within the organ of Corti. It rests on the stereocilia of both the inner and outer hair cells. The tectorial membrane is essential for the transduction of sound vibrations into electrical signals. When sound vibrations cause the basilar membrane to move, the hair cells' stereocilia bend against the tectorial membrane. This mechanical movement leads to the opening of ion channels in the hair cells, resulting in the generation of electrical signals that are transmitted to the brain via the auditory nerve. **Differences Between Inner and Outer Hair Cells:** Inner and outer hair cells have distinct roles in the auditory process: - **IHCs:** Inner hair cells are primarily responsible for transmitting auditory information to the brain. They play a critical role in the initial transduction of sound vibrations into electrical signals. IHCs have fewer stereocilia compared to OHCs and are more directly involved in sound detection. - **OHCs:** Outer hair cells are involved in amplifying and fine-tuning sound vibrations within the cochlea. They play a role in enhancing the sensitivity of the cochlea to a wide range of frequencies and improving the detection of soft sounds. OHCs are more numerous than IHCs and have specialized structures that allow them to actively change their length in response to electrical signals, further enhancing their role in sound processing. In summary, the structure of the spiral organ, including the inner and outer hair cells and the tectorial membrane, is essential for the conversion of sound vibrations into electrical signals, which are then transmitted to the brain for auditory perception.

The spiral organ, also known as the organ of Corti, is a crucial structure located within the cochlea of the inner ear. It plays a central role in the process of hearing by converting mechanical sound vibrations into electrical signals that the brain can interpret. The spiral organ contains specialized hair cells and the tectorial membrane, which are key components in this sensory transduction. **Hair Cells:** Hair cells are the sensory receptors of the spiral organ responsible for detecting sound vibrations and initiating the auditory signal. There are two types of hair cells within the organ of Corti: inner hair cells (IHCs) and outer hair cells (OHCs). 1. **Inner Hair Cells (IHCs):** IHCs are the primary sensory receptors responsible for transmitting auditory signals to the brain. They are arranged in a single row along the length of the organ of Corti and are positioned closer to the central axis of the cochlea. Each IHC is equipped with specialized hair-like protrusions called stereocilia, which are embedded in the tectorial membrane above them. 2. **Outer Hair Cells (OHCs):** OHCs are situated in multiple rows and are positioned on the outer side of the IHCs. These cells play a role in amplifying and fine-tuning sound vibrations in the cochlea. OHCs also have stereocilia that are connected to the tectorial membrane. The stereocilia of OHCs are arranged in a unique "W" or "V"-shaped pattern. **Tectorial Membrane:** The tectorial membrane is a gel-like structure that extends above the hair cells within the organ of Corti. It rests on the stereocilia of both the inner and outer hair cells. The tectorial membrane is essential for the transduction of sound vibrations into electrical signals. When sound vibrations cause the basilar membrane to move, the hair cells' stereocilia bend against the tectorial membrane. This mechanical movement leads to the opening of ion channels in the hair cells, resulting in the generation of electrical signals that are transmitted to the brain via the auditory nerve. **Differences Between Inner and Outer Hair Cells:** Inner and outer hair cells have distinct roles in the auditory process: - **IHCs:** Inner hair cells are primarily responsible for transmitting auditory information to the brain. They play a critical role in the initial transduction of sound vibrations into electrical signals. IHCs have fewer stereocilia compared to OHCs and are more directly involved in sound detection. - **OHCs:** Outer hair cells are involved in amplifying and fine-tuning sound vibrations within the cochlea. They play a role in enhancing the sensitivity of the cochlea to a wide range of frequencies and improving the detection of soft sounds. OHCs are more numerous than IHCs and have specialized structures that allow them to actively change their length in response to electrical signals, further enhancing their role in sound processing. In summary, the structure of the spiral organ, including the inner and outer hair cells and the tectorial membrane, is essential for the conversion of sound vibrations into electrical signals, which are then transmitted to the brain for auditory perception.