NTID HONORS ANATOMY & PHYSIOLOTY – Mr. Barnett Honors
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NTID HONORS ANATOMY & PHYSIOLOTY – Mr. Barnett Honors Anatomy & Physiology: Wednesday – Friday Read pp. 463 – 466 concerning Equilibrium and the corresponding notes attached Complete the Coloring Sheet over the Inner Ear attached (due Test day) **There is no Multiple Choice set of questions as was first indicated Book assignment and Multiple Choice review is due Monday HONORS ANATOMY & PHYSIOLOGY I. Equilibrium A. Equilibrium is primarily centered in the inner ear (vestibule and semicircular canals) B. Equilibrium is also regulated by vision 1. We use information that we see to determine much of our equilibrium—such as the sensation of “down” and “up” 2. Sometimes, conflicting information from our inner ear and eyes can result in our body thinking we’ve been poisoned, which activates the nausea centers of the medulla oblongata: motion sicKness a. Imagine riding in a car on a straight, smooth highway and you are looKing out the side window at the rushing trees passing by: i. Your inner ear detects no major changes in your inertial movement and thus thinKs you are motionless ii. Your eyes, however, see that you are moving iii. This discrepancy between the senses results in motion sicKness b. Imagine riding in a car on a winding, bumpy road as you try to read a book: i. Your inner ear detects your movements as you sway bacK and forth ii. Your eyes focused upon a single page, gives the sensation that you are motionless iii. This discrepancy between the senses results in motion sicKness C. Two types of Equilibrium: static and dynamic D. Static equilibrium 1. Static equilibrium involves knowing the position of the head, directions, body posture, balance when the body is relatively still 2. Point of sensation is the vestibule of the inner ear 3. Vestibule structure a. Vestibule is divided into 2 chambers: utricle and saccule b. Each chamber has a patch of sensory hair cells called the macula (See Fig. 12.18) i. The Utricle has hair cells that are arranged vertically ii. The Saccule has hair cells that are arranged horizontally c. Each macula is associated with a thicK, gelatinous membrane called the otolithic membrane that contains crystals of calcium carbonate (otoliths: “ear stones”) 4. Sensation of static equilibrium a. When your head is upright and facing forward i. The utricle hair cells are not bent, thus no sensory input ii. The saccule hair cells bend downward as the otolithic membrane “oozes” downward due to gravity; this bending sends a signal to the brain where it is interpreted b. Changing orientation of head alters the movements of the hair cells of the utricle and saccule; this sends different combinations of signals to the brain where they are interpreted E. Dynamic equilibrium 1. Dynamic equilibrium occurs when the body is in motion 2. Site of function are the semicircular canals 3. Structure of the semicircular canals a. We have 3 semicircular canals—oriented to the x (lateral canal), y (anterior canal), and z (posterior canal) axes b. Each semicircular canal is filled with perilymph and ends in an enlarged area called an ampulla c. Within each ampulla is a crista ampullaris that contains sensory hair cells that extend into a gelatinous cupula (see Fig. 12.20) 4. Sensation of dynamic equilibrium a. When quicKly shifting the head or position of the body, perilymph and the gelatinous cupula move the hair cells, bending them b. The brain interprets this information to get a sense of equilibrium F. As we age, all gelatinous materials gradually become more viscous and are less liKely to move quicKly Figure 1. Action of the macula during changing positions of the head. Notice that the orientation of hair cells in each head position. This Figure 2. The cupula action during occurs in both the horizontal dynamic equilibrium(saccule) and vertical (utricle) planes. Figure 2. Action of the cupula during dynamic equilibrium. .