Week 1 Chapter 1 1. What is the basic difference between anatomy and physiology? (p. 2) ANSWER: Anatomy (a-NAT-o-me; ana- = up; -tomy = process of cutting) is the science of structure and the relationships among structures. Physiology (fiz? -e-OL-o-je; physio- = nature, -logy = study of) is the science of body functions, that is, how the body parts work. 2. Define each of the following terms: atom, molecule, cell, tissue, organ, system, and organism. (p. 6) ANSWER: AtomUnit of matter that makes up a chemical element; consists of a nucleus (containing positively charged protons and uncharged neutrons) and negatively charged electrons that orbit the nucleus. Molecule (MOL-e-kul)The chemical combination of two or more atoms covalently bonded together.
CellThe basic structural and functional unit of all organisms; the smallest structure capable of performing all the activities vital to life. TissueA group of similar cells and their intercellular substance joined together to perform a specific function. OrganA structure composed of two or more different kinds of tissues with a specific function and usually a recognizable shape. SystemAn association of organs that have a common function. Organism (OR-ga-nizm)A total living form; one individual 3. How are negative and positive feedback systems similar? How are they different? (p. 9) ANSWER: A negative feedback system reverses a change in a controlled condition.
Consider one negative feedback system that helps regulate blood pressure. Blood pressure (BP) is the force exerted by blood as it presses against the walls of blood vessels.
When the heart beats faster or harder, BP increases. If a stimulus causes BP (controlled condition) to rise, the following sequence of events occurs (Figure 1-3). 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 over 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 negative 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 through the midline of the body or organ and divides it into equal right and left 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. (p. 29) ANSWER: The atomic number, the number of protons, distinguishes the atoms of one element from those of another element. The combined total of protons and neutrons in an atom is its mass number. An atom that gives up or gains electrons becomes an ion—an atom that has a positive or negative charge due to having unequal numbers of protons and electrons. A molecule is a substance that consists of two or more chemically combined atoms. The molecular formula indicates the number and type of atoms that make up a molecule. 7. What functions does water perform in the body? (p. 40) ANSWER: 1. Water is an excellent solvent. 2. Water participates in chemical reactions. 3. Water absorbs and releases heat very slowly. . Water requires a large amount of heat to change from a liquid to a gas. 5. Water serves as a lubricant.
Water is the most abundant substance in the body. It is an excellent solvent, participates in chemical reactions, absorbs and releases heat slowly, requires a large amount of heat to change from a liquid to a gas, and serves as a lubricant. 8. Why is ATP important? (p. 40) ANSWER: Adenosine triphosphate (ATP) (a-DEN-o-sen tri-FOS-fat)The main energy currency in living cells; used to transfer the chemical energy needed for metabolic reactions. ATP consists of the purine base adenine and the five-carbon sugar ribose, to which are added, in linear array, three phosphate groups. Chapter 22 9. What are the functions of electrolytes in the body? (p. 550) ANSWER: Electrolytes control the osmosis of water between fluid compartments, help maintain acid–base balance, carry electrical current, and act as enzyme cofactors. 10. What are the major physiological effects of acidosis and alkalosis? (p. 552) ANSWER: The major physiological effect of acidosis is depression of the central nervous system through depression of synaptic transmission. If the systemic arterial blood pH falls below 7, depression of the nervous system is so severe that the individual becomes disoriented, then becomes comatose, and may die. A major physiological effect of alkalosis is overexcitability in both the central nervous system and peripheral nerves. Neurons conduct impulses repetitively, even when not stimulated; the results are nervousness, muscle spasms, and even convulsions and death. Week 2 Chapter 3 11. What is meant by selective permeability? (p. 47) ANSWER: Selective permeability (per? me-a-BIL-i-te)The property of a membrane by which it permits the passage of certain substances but restricts the passage of others. 12. What is the key difference between passive and active transport? (p. 52) ANSWER: Active Processes Movement of substances against a concentration gradient; requires cellular energy in the form of ATP. Active Transport Transport in which cell expends energy to move a substance across the membrane against its concentration gradient aided by membrane proteins that act as pumps; these integral membrane proteins use energy supplied by ATP. Passive Processes Movement of substances down a concentration gradient until equilibrium is reached; do not require cellular energy in the form of ATP. Movement of a substance by kinetic energy down a concentration gradient until equilibrium is reached. 13. How does diffusion through membrane channels compare to facilitated diffusion? (p. 52) ANSWER: Simple diffusion Passive movement of a substance through the lipid bilayer of the plasma membrane. Facilitated diffusion Passive movement of a substance down its concentration gradient aided by ion channels and carriers. In simple diffusion, lipid-soluble substances move through the lipid bilayer. In facilitated diffusion, substances cross the membrane with the assistance of ion channels and carriers. 14. Why is the nucleus so important in the life of a cell? (p. 58) ANSWER: 1. Controls cellular structure. 2. Directs cellular activities. 3. Produces ribosomes in nucleoli.
The nucleus contains most of a cell’s genes, which are located on chromosomes Nucleus Consists of nuclear envelope with pores, nucleoli, and chromatin (or chromosomes). Contains genes, which control cellular structure and direct most cellular activities. Chapter 4 15. Define a tissue.
What are the four basic types of body tissues? (p. 73) ANSWER: A tissue is a group of similar cells, usually with a common embryonic origin, that function together to carry out specialized activities. 1. Epithelial tissue (ep? -i-THE-le-al) covers body surfaces; lines body cavities, hollow organs, and ducts (tubes); and forms glands. 2. Connective tissue protects and supports the body and its organs, binds organs together, stores energy reserves as fat, and provides immunity. 3. Muscular tissue generates the physical force needed to make body structures move. . Nervous tissue detects changes inside and outside the body and initiates and transmits nerve impulses (action potentials) that coordinate body activities to help maintain homeostasis. 16. What are the functions of muscular tissue? (p. 90) ANSWER: muscular tissue produces motion, maintains posture, and generates heat. 17. Name the three types of muscular tissue. (p. 90) ANSWER: skeletal, cardiac, and smooth. Chapter 5 18. What structures are included in the integumentary system? (p. 101) ANSWER: Skin and structures associated with it, such as hair, nails, and sweat and oil glands. 9. What are the three pigments found in the skin, and how do they contribute to skin color? (p. 101) ANSWER: Skin color is due to the pigments melanin, carotene, and hemoglobin. Melanin, hemoglobin, and carotene are three pigments that impart a wide variety of colors to skin. The amount of melanin causes the skin’s color to vary from pale yellow to reddish-brown to black.
Melanocytes are most plentiful in the epidermis of the penis, nipples of the breasts, the area just around the nipples (areolae), face, and limbs. They are also present in mucous membranes. Because the number of melanocytes is about the same in all people, differences in skin color are due mainly to the amount of pigment the melanocytes produce and transfer to keratinocytes. In some people, melanin accumulates in patches called freckles. As a person grows older, age (liver) spots may develop. These flat blemishes look like freckles and range in color from light brown to black. Like freckles, age spots are accumulations of melanin. A round, flat, or raised area that represents a benign localized overgrowth of melanocytes and usually develops in childhood or adolescence is called a nevus (NE-vus), or a mole.
Exposure to UV light stimulates melanin production. Both the amount and darkness of melanin increase, which gives the skin a tanned appearance and further protects the body against UV radiation. Thus, within limits, melanin serves a protective function. Nevertheless, repeatedly exposing the skin to UV light causes skin cancer. A tan is lost when the melanin-containing keratinocytes are shed from the stratum corneum.
Albinism (AL-bin-izm; albin- = white) is the inherited inability of an individual to produce melanin. Most albinos (al-BI-nos), people affected by albinism, do not have melanin in their hair, eyes, and skin. In another condition, called vitiligo (vit-i-LI-go), the partial or complete loss of melanocytes from patches of skin produces irregular white spots. The loss of melanocytes may be related to an immune system malfunction in which antibodies attack the melanocytes. Dark-skinned individuals have large amounts of melanin in the epidermis. Consequently, the epidermis has a dark pigmentation and skin color ranges from yellow to red to tan to black.
Light-skinned individuals have little melanin in the epidermis. Thus, the epidermis appears translucent and skin color ranges from pink to red depending on the amount and oxygen content of the blood moving through capillaries in the dermis.
The red color is due to hemoglobin, the oxygen-carrying pigment in red blood cells. Carotene (KAR-o-ten; carot = carrot) is a yellow-orange pigment that gives egg yolk and carrots their color. This precursor of vitamin A, which is used to synthesize pigments needed for vision, accumulates in the stratum corneum and fatty areas of the dermis and subcutaneous layer in response to excessive dietary intake. In fact, so much carotene may be deposited in the skin after eating large amounts of carotene-rich foods that the skin color actually turns orange, which is especially apparent in light-skinned individuals. Decreasing carotene intake eliminates the problem. 20. In what two ways does the skin help regulate body temperature? (p. 106) ANSWER: Body temperature regulation.
The skin contributes to the homeostatic regulation of body temperature by liberating sweat at its surface and by adjusting the flow of blood in the dermis. In response to high environmental temperature or heat produced by exercise, sweat production from eccrine sweat glands increases; the evaporation of sweat from the skin surface helps lower body temperature. In addition, blood vessels in the dermis of the skin dilate (become wider); consequently, more blood flows through the dermis, which increases the amount of heat loss from the body. In response to low environmental temperature, production of sweat from eccrine sweat glands is decreased, which helps conserve heat. Also, the blood vessels in the dermis f the skin constrict (become narrow), which decreases blood flow through the skin and reduces heat loss from the body. 21. In what ways does the skin serve as a protective barrier? (p. 106) ANSWER: Protection. Keratin in the skin protects underlying tissues from microbes, abrasion, heat, and chemicals, and the tightly interlocked keratinocytes resist invasion by microbes. Lipids released by lamellar granules inhibit evaporation of water from the skin surface, thus protecting the body from dehydration. Oily sebum prevents hairs from drying out and contains bactericidal chemicals that kill surface bacteria.
The acidic pH of perspiration retards the growth of some microbes. Melanin provides some protection against the damaging effects of UV light. Hair and nails also have protective functions. Week 3 Chapter 6 22. Give several examples of long, short, flat, and irregular bones. (p. 114) ANSWER: Long bones have greater length than width and consist of a shaft and a variable number of ends.
They are usually somewhat curved for strength. Long bones include those in the thigh (femur), leg (tibia and fibula), arm (humerus), forearm (ulna and radius), and fingers and toes (phalanges). Short bones are somewhat cube-shaped and nearly equal in length and width. Examples of short bones include most wrist and ankle bones. Flat bones are generally thin, afford considerable protection, and provide extensive surfaces for muscle attachment. Bones classified as flat bones include the cranial bones, which protect the brain; the sternum (breastbone) and ribs, which protect organs in the thorax; and the scapulae (shoulder blades). Irregular bones have complex shapes and cannot be grouped into any of the previous categories.
Such bones include the vertebrae and some facial bones. 3. What are the four types of cells in bone tissue? (p. 118) ANSWER: 1. Osteogenic cells (os-te-o-JEN-ik; -genic = producing) are unspecialized stem cells derived from mesenchyme, the tissue from which almost all connective tissues are formed. They are the only bone cells to undergo cell division; the resulting cells develop into osteoblasts.
Osteogenic cells are found along the inner portion of the periosteum, in the endosteum, and in the canals within bone that contain blood vessels. 2. Osteoblasts (OS-te-o-blasts? ; -blasts = buds or sprouts) are bone-building cells. They synthesize and secrete collagen fibers and other organic components needed to build the extracellular matrix of bone tissue. As osteoblasts surround themselves with extracellular matrix, they become trapped in their secretions and become osteocytes. (Note: Blasts in bone or any other connective tissue secrete extracellular matrix. ) 3. Osteocytes (OS-te-o-sits? ; -cytes = cells), mature bone cells, are the main cells in bone tissue and maintain its daily metabolism, such as the exchange of nutrients and wastes with the blood. Like osteoblasts, osteocytes do not undergo cell division. Note: Cytes in bone or any other tissue maintain the tissue. ) 4. Osteoclasts (OS-te-o-clasts? ; -clast = break) are huge cells derived from the fusion of as many as 50 monocytes (a type of white blood cell) and are concentrated in the endosteum.
They release powerful lysosomal enzymes and acids that digest the protein and mineral components of the bone extracellular matrix. This breakdown of bone extracellular matrix, termed resorption, is part of the normal development, growth, maintenance, and repair of bone. (Note: Clasts in bone break down extracellular matrix. ) 24. What is bone remodeling? Why is it important? (p. 123) ANSWER: Bone remodeling is the ongoing replacement of old bone tissue by new bone tissue. It involves bone resorption, the removal of minerals and collagen fibers from bone by osteoclasts, and bone deposition, the addition of minerals and collagen fibers to bone by osteoblasts. Thus, bone resorption results in the destruction of bone extracellular matrix, while bone deposition results in the formation of bone extracellular matrix. Remodeling takes place at different rates in different regions of the body. Even after bones have reached their adult shapes and sizes, old bone is continually destroyed and new bone is formed in its place.
Remodeling also removes injured bone, replacing it with new bone tissue. Remodeling may be triggered by factors such as exercise, sedentary lifestyle, and changes in diet. Old bone is constantly destroyed by osteoclasts, while new bone is constructed by osteoblasts. This process is called remodeling. 25. What are some of the important functions of calcium in the body? (p. 123) ANSWER: In addition, most functions of nerve cells depend on just the right level of Ca2+, many enzymes require Ca2+ as a cofactor, and blood clotting requires Ca2+. The role of bone in calcium homeostasis is to “buffer” the blood calcium level, releasing Ca2+ to the blood when the blood calcium level falls (using osteoclasts) and depositing Ca2+ back in bone when the blood level rises (using osteoblasts). 26. What types of mechanical stress may be used to strengthen bone tissue? (p. 124) ANSWER: Weight-bearing activities, such as walking or moderate weightlifting, help build and retain bone mass.
Adolescents and young adults should engage in regular weight-bearing exercise prior to the closure of the epiphyseal plates to help build total mass before its inevitable reduction with aging. However, the benefits of exercise do not end in young adulthood. Even elderly people can strengthen their bones by engaging in weight-bearing exercise. 27. How does aging affect the brittleness of bone and the loss of bone mass? (p. 147) ANSWER: Bone brittleness results from a decrease in the rate of protein synthesis and in the production of human growth hormone, which diminishes the production of the collagen fibers that give bone its strength and flexibility. As a result, inorganic minerals gradually constitute a greater proportion of the bone extracellular matrix. Loss of bone mass results from demineralization Chapter 7 28. What factors determine movement at joints? (p. 157) ANSWER: The functional classification of joints relates to the degree of movement they permit. Functionally, joints are classified as one of the following types: Synarthrosis (sin? -ar-THRO-sis; syn- = together): An immovable joint.
The plural is synarthroses. Amphiarthrosis (am? -fe-ar-THRO-sis; amphi- = on both sides): A slightly movable joint.
The plural is amphiarthroses. Diarthrosis (di? -ar-THRO-sis = movable joint): A freely movable joint. The plural is diarthroses. All diarthroses are synovial joints.
They have a variety of shapes and permit several different types of movements 29. Define each of the movements at synovial joints and give an example of each. (p. 163) ANSWER: 1. In a gliding movement, the nearly flat surfaces of bones move back-and-forth and side-to-side. This can be illustrated between the clavicle and acromion of the scapula by placing your upper limb at your side, raising it above your head, and lowering it again. 2. In angular movements, there is a change in the angle between bones. Examples are flexion–extension, hyperextension, abduction–adduction, and circumduction. Examples of flexion include bending the head toward the chest (Figure 7-4a); moving the humerus forward at the shoulder joint as in swinging the arms forward while walking (Figure 7-4b); moving the forearm toward the arm (Figure 7-4c); moving the palm toward the forearm (Figure 7-4d); moving the femur forward, as in walking (Figure 7-4e); and bending the knee (Figure 7-4f). Extension is simply the reverse of these movements. 3. In rotation, a bone moves around its own longitudinal axis. An example is turning the head from side to side 4. Special movements occur at specific synovial joints in the body. Examples are as follows: elevation–depression, protractionretraction, inversion–eversion, dorsiflexion–plantar flexion, and supination–pronation Elevation (el? -e-VA-shun = to lift up) is the upward movement of a part of the body, such as closing the mouth to elevate the mandible (Figure 7-8a) or shrugging the shoulders to elevate the scapula.
Depression (de-PRESH-un = to press down) is the downward movement of a part of the body, such as opening the mouth to depress the mandible (Figure 7-8b) or returning shrugged shoulders to the anatomical position to depress the scapula. Protraction (pro-TRAK-shun = to draw forth) is the movement of a part of the body forward. You can protract your mandible by thrusting it outward (Figure 7-8c) or protract your clavicles by crossing your arms. Retraction (re-TRAK-shun = to draw back) is the movement of a protracted part of the body back to the anatomical position (Figure 7-8d). Inversion (in-VER-zhun = to turn inward) is movement of the soles medially so that they face each other (Figure 7-8e). Eversion (e-VER-zhun = to turn outward) is movement of the soles laterally so that they face away from each other (Figure 7-8f). Dorsiflexion (dor? -si-FLEK-shun) is bending of the foot in the direction of the dorsum (superior surface), as when you stand on your heels (Figure 7-8g). Plantar flexion involves bending of the foot in the direction of the plantar surface (Figure 7-8g), as when standing on your toes.
Supination (soo? -pi-NA-shun) is movement of the forearm so that the palm is turned forward (Figure 7-8h). Supination of the palms is one of the defining features of the anatomical position (see Figure 1-4). Pronation (pro-NA-shun) is movement of the forearm so that the palm is turned backward (Figure 7-8h). Opposition (op-o-ZISH-un) is the movement of the thumb at the carpometacarpal joint (between the trapezium and metacarpal of the thumb) in which the thumb moves across the palm to touch the tips of the fingers on the same hand (Figure 7-8i). This is the distinctive digital movement that gives humans and other primates the ability to grasp and manipulate objects very precisely. 30. Which joints show evidence of degeneration in nearly all individuals as aging progresses? (p. 167) ANSWER: knees, elbows, hips, and shoulders. It is also common for elderly individuals to develop degenerative changes in the vertebral column Chapter 8 31. Which features distinguish the three types of muscular tissue? (p. 173) ANSWER: Skeletal muscle tissue is mostly attached to bones. It is striated and voluntary. Cardiac muscle tissue forms most of the wall of the heart. It is striated and involuntary. Smooth muscle tissue is located in viscera. It is nonstriated and involuntary. 32. What are the general functions of muscular tissue? (p. 173) ANSWER: Producing body movements. Stabilizing body positions. Storing and moving substances within the body.
Producing heat. 33. What is a sarcomere? What does a sarcomere contain? p. 175) ANSWER: Sarcomere (SAR-ko-mer)A contractile unit in a striated muscle fiber (cell) extending from one Z disc to the next Z disc. A bands 34. Explain how a skeletal muscle contracts and relaxes. (p. 180) ANSWER: Muscle contraction occurs when myosin heads attach to and “walk” along the thin filaments at both ends of a sarcomere, progressively pulling the thin filaments toward the center of a sarcomere. As the thin filaments slide inward, the Z discs come closer together, and the sarcomere shortens. Two changes permit a muscle fiber to relax after it has contracted.
First, the neurotransmitter acetylcholine is rapidly broken down by the enzyme acetylcholinesterase (AChE). When nerve action potentials cease, release of ACh stops, and AChE rapidly breaks down the ACh already present in the synaptic cleft. This ends the generation of muscle action potentials, and the Ca2+ release channels in the sarcoplasmic reticulum membrane close. Second, calcium ions are rapidly transported from the sarcoplasm into the sarcoplasmic reticulum. As the level of Ca2+ in the sarcoplasm falls, tropomyosin slides back over the myosin-binding sites on actin. Once the myosin-binding sites are covered, the thin filaments slip back to their relaxed positions.
Figure 8-7 summarizes the events of contraction and relaxation in a muscle fiber. 35. What is the importance of the neuromuscular junction? (p. 180) ANSWER: At the NMJ, a motor neuron excites a skeletal muscle fiber in the following way Release of acetylcholine. Activation of ACh receptors. Generation of muscle action potential. Breakdown of ACh. The neuromuscular junction (NMJ) is the synapse between a motor neuron and a skeletal muscle fiber. It is where the axons of motor nerves meet the muscle & transmit messages from the brain which cause the muscle to contract & relax. 36. Define the following terms: myogram, twitch contraction, wave summation, unfused tetanus, and fused tetanus. (p. 185) ANSWER: A record of a contraction is called a myogram. It consists of a latent period, a contraction period, and a relaxation period. A twitch contraction is a brief contraction of all the muscle fibers in a motor unit in response to a single action potential. Wave summation is the increased strength of a contraction that occurs when a second stimulus arrives before the muscle has completely relaxed after a previous stimulus.
When a skeletal muscle fiber is stimulated at a rate of 20 to 30 times per second, it can only partially relax between stimuli. The result is a sustained but wavering contraction called unfused (incomplete) tetanus (tetan- = rigid, tense; Figure 8-10c). When a skeletal muscle fiber is stimulated at a higher rate of 80 to 100 times per second, it does not relax at all. The result is fused (complete) tetanus, a sustained contraction in which individual twiches cannot be detected (Figure 8-10d). 37. What characteristics distinguish the three types of skeletal muscle fibers? (p. 185) ANSWER: Slow oxidative (SO) fibers or red fibers are small in diameter and appear dark red because they contain a large amount of myoglobin. Because they have many large mitochondria, SO fibers generate ATP mainly by aerobic cellular respiration, which is why they are called oxidative fibers.
These fibers are said to be “slow” because the contraction cycle proceeds at a slower pace than in “fast” fibers. SO fibers are very resistant to fatigue and are capable of prolonged, sustained contractions. Fast oxidative–glycolytic (FOG) fibers are intermediate in diameter between the other two types. Like slow oxidative fibers, they contain a large amount of myoglobin, and thus appear dark red. FOG fibers can generate considerable ATP by aerobic cellular respiration, which gives them a moderately high resistance to fatigue. Because their glycogen content is high, they also generate ATP by anaerobic glycolysis. These fibers are “fast” because they contract and relax more quickly than SO fibers.
Fast glycolytic (FG) fibers or white fibers are largest in diameter, contain the most myofibrils, and generate the most powerful and most rapid contractions. They have a low myoglobin content and few mitochondria. FG fibers contain large amounts of glycogen and generate ATP mainly by anaerobic glycolysis.
They are used for intense movements of short duration, but they fatigue quickly. Strength-training programs that engage a person in activities requiring great strength for short times produce increases in the size, strength, and glycogen content of FG fibers. 38. Explain how the characteristics of skeletal muscle fibers may change with exercise. (p. 186) ANSWER: Although the total number of skeletal muscle fibers usually does not increase, the characteristics of those present can change to some extent. Various types of exercises can induce changes in the fibers in a skeletal muscle. Endurance-type (aerobic) exercises, such as running or swimming, cause a gradual transformation of some FG fibers into fast oxidative–glycolytic (FOG) fibers.
The transformed muscle fibers show slight increases in diameter, number of mitochondria, blood supply, and strength. Endurance exercises also result in cardiovascular and respiratory changes that cause skeletal muscles to receive better supplies of oxygen and nutrients but do not increase muscle mass. By contrast, exercises that require great strength for short periods produce an increase in the size and strength of FG fibers. The increase in size is due to increased synthesis of thick and thin filaments. The overall result is muscle enlargement (hypertrophy), as evidenced by the bulging muscles of body builders. 39. Why does muscle strength decrease with aging? p. 188) ANSWER: due to decreased levels of physical activity. Week 4 Chapter 9 40. What are the functions of the dendrites, cell body, axon, and synaptic end bulbs of a neuron? (p. 230) ANSWER: Dendrite (DEN-drit)A neuronal process that carries electrical signals toward the cell body.
The cell body contains a nucleus surrounded by cytoplasm that includes typical organelles such as rough endoplasmic reticulum, lysosomes, mitochondria, and a Golgi complex. Most cellular molecules needed for a neuron’s operation are synthesized in the cell body. Axon (AK-son)The usually single, long process of a nerve cell that propagates a nerve impulse toward the axon terminals. Synapse (SYN-aps)The functional junction between two neurons or between a neuron and an effector, such as a muscle or gland; may be electrical or chemical. 41. Which cells produce myelin in nervous tissue, and what is the function of a myelin sheath? (p. 230) ANSWER: formed by Schwann cells and oligodendrocytes Like insulation covering an electrical wire, the myelin sheath insulates the axon of a neuron and increases the speed of nerve impulse conduction. 2. What are the meanings of the terms: resting membrane potential, depolarization, repolarization, nerve impulse, and refractory period? (p. 234) ANSWER: Resting membrane potentialThe voltage difference between the inside and outside of a cell membrane when the cell is not responding to a stimulus; in many neurons and muscle fibers it is –70 to –90 mV, with the inside of the cell negative relative to the outside. depolarizing phase, the negative membrane potential becomes less negative, reaches zero, and then becomes positive. epolarizing phase, the membrane polarization is restored to its resting state of -70 mV. Nerve impulse is a wave of physical and chemical excitation along a nerve fiber in response to a stimulus, accompanied by a transient change in electric potential in the membrane of the fiber.
During the refractory period, another action potential cannot be generated. For a brief time after an action potential begins, a muscle fiber or neuron cannot generate another action potential. This time is called the refractory period. Chapter 10 43. What is the significance of the blood-brain barrier? (p. 254) ANSWER: The blood–brain barrier (BBB) limits the passage of certain material from the blood into the brain. 44. Why is the hypothalamus considered part of both the nervous system and the endocrine system? (p. 263) ANSWER: The hypothalamus controls the release of several hormones from the pituitary gland and thus serves as a primary connection between the nervous system and endocrine system. 45. Where are the primary somatosensory area and primary motor area located in the brain? What are their functions? (p. 263) ANSWER: Cerebral Cortex The primary somatosensory area (so? -mat-o-SEN-so-re) is posterior to the central sulcus of each cerebral hemisphere in the postcentral gyrus of the parietal lobe (Figure 10-13). It receives nerve impulses for touch, proprioception (joint and muscle position), pain, itching, tickle, and temperature and is involved in the perception of these sensations. The primary somatosensory area allows you to pinpoint where sensations originate, so that you know exactly where on your body to swat that mosquito.
The primary visual area, located in the occipital lobe, receives visual information and is involved in visual perception. The primary auditory area, located in the temporal lobe, receives information for sound and is involved in auditory perception.
The primary gustatory area, located at the base of the postcentral gyrus, receives impulses for taste and is involved in gustatory perception. The primary olfactory area, located on the medial aspect of the temporal lobe (and thus is not visible in Figure 10-13), receives impulses for smell and is involved in olfactory perception. Chapter 11 46. What happens during the fight-or-flight response? (p. 280) ANSWER: 1. The pupils of the eyes dilate. 2. Heart rate, force of heart contraction, and blood pressure increase. 3. The airways dilate, allowing faster movement of air into and out of the lungs. 4. The blood vessels that supply nonessential organs such as the kidneys and gastrointestinal tract constrict, which reduces blood flow through these tissues. The result is a slowing of urine formation and digestive activities, which are not essential during exercise. 5. Blood vessels that supply organs involved in exercise or fighting off danger—skeletal muscles, cardiac muscle, liver, and adipose tissue—dilate, which allows greater blood flow through these tissues. 6. Liver cells break down glycogen to glucose, and adipose cells break down triglycerides to fatty acids and glycerol, providing molecules that can be used by body cells for ATP production. 7. Release of glucose by the liver increases blood glucose level. 8. Processes that are not essential for meeting the stressful situation are inhibited.
For example, muscular movements of the gastrointestinal tract and digestive secretions decrease or even stop. 47. Why is the parasympathetic division of the ANS considered the rest-and-digest division? (p. 280) ANSWER: the parasympathetic division enhances “rest-and-digest” activities. Parasympathetic responses support body functions that conserve and restore body energy during times of rest and recovery. In the quiet intervals between periods of exercise, parasympathetic impulses to the digestive glands and the smooth muscle of the gastrointestinal tract predominate over ympathetic impulses. This allows energy-supplying food to be digested and absorbed. At the same time, parasympathetic responses reduce body functions that support physical activity Chapter 12 48. Which senses are “special senses”? (p. 286) ANSWER: special senses, which include smell, taste, vision, hearing, and equilibrium (balance). 49. Why is it beneficial to your well-being that nociceptors and proprioceptors exhibit very little adaptation? (p. 290) ANSWER: The lack of adaptation of nociceptors serves a protective function: If there were adaptation to painful stimuli, irreparable tissue damage could result. Proprioceptive sensations also allow us to estimate the weight of objects and determine the muscular effort necessary to perform a task. Because proprioceptors adapt slowly and only slightly, the brain continually receives nerve impulses related to the position of different body parts and makes adjustments to ensure coordination. 50. What is referred pain, and how is it useful in diagnosing internal disorders? (p. 290) ANSWER: In many instances of visceral pain, the pain is felt in or just deep to the skin that overlies the stimulated organ, or in a surface area far from the stimulated organ.
This phenomenon is called referred pain (Figure 12-2). In general, the visceral organ involved and the area in which the pain is referred are served by the same segment of the spinal cord. For example, sensory neurons from the heart, the skin over the heart, and the skin along the medial aspect of the left arm enter spinal cord segments T1 to T5. Thus, the pain of a heart attack typically is felt in the skin over the heart and along the left arm.
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