The Basic Difference Between Anatomy and Physiology
When the heart beats faster or harder, BP increases. If a stimulus causes BP The higher pressure is detected by baroreceptors, pressure-sensitive nerve cells located in the walls of certain blood vessels (the receptors). The baroreceptors send nerve impulses (input) to the brain (control center), which interprets the impulses and responds by sending nerve impulses (output) to the heart (the effector). Heart rate decreases, which causes BP to decrease (response). This sequence of events returns the controlled condition”blood pressure”to normal, and homeostasis is restored.
This is a negative feedback system because the activity of the effector produces a result, a drop in BP, that reverses the effect of the stimulus. Negative feedback systems tend to regulate conditions in the body that are held fairly stable ver long periods, such as BP, blood glucose level, and body temperature. A positive feedback system strengthens a change in a controlled condition. Normal positive feedback systems tend to reinforce conditions that don’t happen very often, such as childbirth, ovulation, and blood clotting.
Because a positive feedback system continually reinforces a change in a controlled condition, it must be shut off by some event outside the system. If the action of a positive feedback system isn’t stopped, it can “run away’ and produce life-threatening changes in the body. The basic difference between negative and positive feedback systems is that in egative feedback systems, the response reverses a change in a controlled condition, and in positive feedback systems, the response strengthens the change in a controlled condition. 4.
Describe the anatomical position and explain why it is used. (p. 15) ANSWER: The language of anatomy and physiology is very precise. In the study of anatomy, descriptions of any part of the human body assume that the body is in a specific stance called the anatomical position (an’-a-TOM-i-kal). In the anatomical position, the subject stands erect facing the observer, with the head level and the eyes facing forward. The feet are flat on the floor and directed forward, and the arms are at the sides with the palms turned forward (Figure 1-4 on page 11).
In the anatomical position, the body is upright. Descriptions of any region of the body assume the body is in the anatomical position, in which the subject stands erect facing the observer, with the head level and the eyes facing forward, the feet flat on the floor and directed forward, and the arms at the sides, with the palms turned forward. 5. What are the various planes that may be passed through the body? Explain how each divides the body. (p. 15) ANSWER: A sagittal plane (SAJ-i-tal; sagitt- = arrow) is a vertical plane that divides the body or an organ into right and left sides.
More specifically, when such a plane passes sides, it is called a midsagittal plane. If the sagittal plane does not pass through the midline but instead divides the body or an organ into unequal right and left sides, it is called a parasagittal plane (para- = near). A frontal plane or coronal plane divides the body or an organ into anterior (front) and posterior (back) portions. A transverse plane divides the body or an organ into superior (upper) and inferior (lower) portions. A transverse plane may also be called a cross-sectional or horizontal plane.
Sagittal, frontal, and transverse planes are all at right angles to one another. An oblique plane, by contrast, passes through the body or an organ at an angle between the transverse plane and a sagittal plane or between the transverse plane and the frontal plane. Chapter 2 6. Compare the meanings of atomic number, mass number, ion, and molecule.