Chapter 13 Lecture Outline

Transcription

1 Chapter 13 Lecture Outline See separate PowerPoint slides for all figures and tables preinserted into PowerPoint without notes. Copyright 2016 McGraw-Hill Education. Permission required for reproduction or display. 1

2 Muscular System 2

3 Points to ponder What are the three types of muscle tissue? What are the functions of the muscular system? How are muscles named and what are the muscles of the human body? How are skeletal muscles and muscle fibers structured? How do skeletal muscles contract? How do skeletal muscle cells acquire ATP for contraction? What is rigor mortis? What are some common muscular disorders? What are some serious muscle diseases? How do the skeletal and muscular system help maintain homeostasis? How are these two systems related to other systems in maintaining homeostasis? 3

4 13.1 Overview of the Muscular System Review: Types of muscle tissue 1. Smooth involuntary muscle found in hollow organs and vessels 2. Cardiac involuntary muscle found in the heart 3. Skeletal voluntary muscle that is attached to the skeleton 4

5 13.1 Overview of the Muscular System Review: Types of muscle tissue Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Skeletal muscle has striated cells with multiple nuclei. occurs in muscles attached to skeleton. functions in voluntary movement of body. Smooth muscle has spindle-shaped cells, each with a single nucleus. cells have no striations. functions In movement of substances in lumens of body. is involuntary. is found in blood vessel walls and walls of the digestive tract. Cardiac muscle has branching, striated cells, each with a single nucleus. occurs in the wall of the heart. functions in the pumping of blood. is involuntary. 250X striation nucleus 400X 250X Smooth muscle cell nucleus Intercalated disk nucleus a. b. c. (smooth): The McGraw-Hill Companies, Inc. Dennis Strete, photographer; (cardiac, skeletal): Ed Reschke; Figure 13.1 The three classes of muscles in humans. 5

6 13.1 Overview of the Muscular System What are the functions of skeletal muscles? 1. Support the body by allowing us to stay upright 2. Allow for movement by attaching to the skeleton 3. Help maintain a constant body temperature 4. Assist in movement in the cardiovascular and lymphatic vessels 5. Protect internal organs and stabilize joints 6

7 13.1 Overview of the Muscular System How are skeletal muscles attached? Tendon connective tissue that connects muscle to bone Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. muscle fiber Origin attachment of a muscle on a stationary bone Insertion attachment of a muscle on a bone that moves tendon fascicle radius dense connective tissue Figure 13.2 Connecting muscle to bone. 7

8 13.1 Overview of the Muscular System How do skeletal muscles work? Antagonistic muscles that work in opposite pairs Synergistic muscles working in groups for a common action Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. radius ulna a. biceps brachii (relaxed) triceps brachii (contracted) tendon origin biceps brachii (contracted) triceps brachii (relaxed) humerus insertion Figure 13.3 Skeletal muscles often work in pairs. b. 8

9 13.1 Overview of the Muscular System Examples of how skeletal muscles are named Size the gluteus maximus is the largest buttock muscle Shape the deltoid is triangular (Greek letter delta is Δ) Location the frontalis overlies the frontal bone Direction of muscle fiber the rectus abdominis is longitudinal (rectus means straight) 9

10 13.1 Overview of the Muscular System Examples of how skeletal muscles are named Attachment the brachioradialis is attached to the brachium and radius Number of attachments the biceps brachii has 2 attachments Action the extensor digitorum extends the digits 10

11 13.1 Overview of the Muscular System Muscles of the human body Orbicularis oculi: blinking, winking, responsible for crow s feet Orbicularisor is: kissing muscle Pectoralis major: brings arm forward and across chest Serratus anterior: pulls the scapula (shoulder blade) forward, as in pushing or punching External oblique: compresses abdomen; rotation of trunk Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Masseter: a chewing muscle; clenches teeth Deltoid: brings arm away from the side of body; moves arm up and down in front Biceps brachii: bends forearm at elbow Rectus abdominis: Bends vertebral column; compresses abdomen Flexor carpi group: bends wrist and hand Trapezius: Raises scapula, as When shrugging shoulders; pulls head backward Latissimus dorsi: brings arm down and backward behind the body Triceps brachii: straightens forearm at elbow Extensor carpi group: straightens wrist and hand Extensor digitorum: straightens fingers and wrist Quadriceps femoris: straightens leg at knee; raises thigh Tibialis anterior: turns foot upward, as when walking on heels Extensor digitorum longus: raises toes; raises foot a. Figure 13.5 The major skeletal muscles of the human body. Adductor longus: moves thigh toward midline; raises Sartorius: raises and laterally rotates thigh; raises and rotates leg close to body; these combined actions occur when crossing legs or kicking across, as in soccer Limbs Arm: above the elbow Forearm: below the elbow Thigh: above the knee Leg: below the knee b. Gluteus maximus: extends thigh back Biceps femoris: bends leg at knee; extends thigh back Gastrocnemius: turns foot downward, as when standing on toes; bends leg at knee Achilles tendon 11

12 13.2 Skeletal Muscle Fiber Contraction Muscle fibers/cells Terminology for cell structure The plasma membrane is called the sarcolemma. The cytoplasm is called the sarcoplasm. The SER of a muscle cell is called the sarcoplasmic reticulum and stores calcium. 12

13 13.2 Skeletal Muscle Fiber Contraction Muscle fibers/cells Terminology for structure within a whole muscle Muscle fibers are arranged in bundles called fascicles. Myofibrils are bundles of myofilaments that run the length of a fiber. Myofilaments are proteins (actin and myosin) that are arranged in repeating units. Sarcomeres are the repeating units of actin and myosin found along a myofibril. 13

14 13.2 Skeletal Muscle Fiber Contraction Visualizing muscle structure A muscle contains bundles of muscle fibers, and a muscle fiber has many myofibrils. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. bundle of muscle cells (fibers) myofibril sarcolemma mitochondrion sarcoplasm one myofibril skeletal muscle cell (fiber) myofilament Z line one sarcomere Z line T tubule sarcoplasmic reticulum nucleus A myofibril has many sarcomeres. Figure 13.6 The structure of a skeletal muscle fiber. 6,000 (myofi bril): Biology Media/Photo Researchers, Inc. 14

15 13.2 Skeletal Muscle Fiber Contraction The sarcomere Made of 2 protein myofilaments A thick filament is composed of several hundred molecules of the protein myosin. Each myosin molecule is shaped like a golf club. Primarily, a thin filament consists of two intertwining strands of the protein actin. These filaments slide over one another during muscle contraction. 15

16 13.2 Skeletal Muscle Fiber Contraction The sarcomere Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. crossbridge myosin actin Sarcomeres are relaxed. H band Z line A band I band Sarcomeres are contracted. Figure 13.6 The structure of a skeletal muscle fiber. 16

17 13.2 Skeletal Muscle Fiber Contraction The beginning of muscle contraction: The sliding filament model 1. Nerve impulses travel down a motor neuron to a neuromuscular junction. 2. Acetylcholine (ACh) is released from the neuron and binds to the muscle fiber. 3. This binding stimulates the fiber causing calcium to be released from the sarcoplasmic reticulum. 17

18 13.2 Skeletal Muscle Fiber Contraction The beginning of muscle contraction Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. skeletal muscle fiber axon branch axon terminal (photo): Victor B. Eichler synaptic vesicle a. One motor axon goes to Several muscle fibers. synaptic cleft acetylcholine (ACh) axon terminal synaptic vesicle synaptic cleft sarcolemma folded sarcolemma Ach receptor b. Asynaptic cleft exists between an axon terminal and a muscle fiber. c.neurotransmitter (ACh) diffuses across synaptic cleft and binds to receptors in sarcolemma. Figure 13.7 Motor neurons and skeletal muscle fibers join neuromuscular junctions. 18

19 13.2 Skeletal Muscle Fiber Contraction Muscle contraction continued 4. Released calcium combines with troponin, a molecule associated with actin. 5. This causes the tropomyosin threads around actin to shift and expose myosin binding sites. 6. Myosin heads bind to these sites forming crossbridges. 7. ATP binds to the myosin heads and is used for energy to pull the actin filaments towards the center of the sarcomere contraction now occurs. 19

20 13.2 Skeletal Muscle Fiber Contraction Visualizing the roles of calcium and myosin in muscle contraction Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. actin filament troponin myosin-binding sites Ca 2+ Ca 2+ Function of Ca 2+ tropomyosin Troponin Ca+ complex pulls tropomyosin away, exposing myosin-binding sites. actin filament myosin filament P ADP cross-bridge myosin head 1.ATP is split when myosin head is unattached. ATP 4.Binding of fresh ATP causes myosin Head to return to resting position. 2. ADP+ P are bound to myosin asmyos in head attaches to actin. myosin heads actin b. Function of myosin 3.Upon ADP + P releases, power stroke occurs: head bends and pulls actin. Figure 13.8 The role of calcium ions and ATP during muscular contraction. 20

21 13.2 Skeletal Muscle Fiber Contraction What role does ATP play in muscle contraction and rigor mortis? ATP is needed to attach and detach the myosin heads from actin. After death, muscle cells continue to produce ATP through fermentation and muscle cells can continue to contract. When ATP runs out, some myosin heads are still attached and cannot detach, causing rigor mortis. Rigor mortis and body temperature may be used to estimate time of death. 21

22 13.3 Whole Muscle Contraction Terms to describe whole muscle contraction Motor unit a nerve fiber and all of the muscle fibers it stimulates Muscle twitch a single contraction lasting a fraction of a second Summation an increase in muscle contraction until the maximal sustained contraction is reached 22

23 13.3 Whole Muscle Contraction Terms to describe whole muscle contraction Tetanus maximal sustained contraction Muscle tone a continuous, partial contraction of alternate muscle fibers causing the muscle to look firm 23

24 Force Force 13.3 Whole Muscle Contraction Physiology of skeletal muscle contraction Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. contraction period relaxation period latent period Stimulus Time a. summation tetanus fatigue Stimuli Time b. Figure 13.9 The three phases of a single muscle twitch and how summation and tetanus increase the force of contraction. 24

25 13.3 Whole Muscle Contraction Percentage of energy expenditure Where are the fuel sources for muscle contraction? Stored in the muscle Glycogen Fat Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display muscle triglycerides plasma fatty acids blood glucose muscle glycogen In the blood Glucose Fatty acids Exercise time (hr) Figure The sources of energy for muscle contraction. 25

26 13.3 Whole Muscle Contraction What are the sources of ATP for muscle contraction? Limited amounts of ATP are stored in muscle fibers. Creatine phosphate pathway (CP) fastest way to acquire ATP but only sustains a cell for seconds; builds up when a muscle is resting Fermentation fast-acting but results in lactate build up Cellular respiration (aerobic) not an immediate source of ATP but the best long term source 26

27 13.3 Whole Muscle Contraction Acquiring ATP for muscle contraction Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anaerobic Anaerobic Aerobic creatine phosphate glycogen fermentation glycogen or fatty acids O 2 creatine lactate CO 2 + H 2 O ATP ATP ATP a. b. c. Figure The three pathways by which muscle cells produce the ATP energy needed for contraction. 27

28 13.3 Whole Muscle Contraction Muscle fibers come in 2 forms Fast-twitch fibers Rely on CP and fermentation (anaerobic) Adapted for strength Light in color Few mitochondria Little or no myoglobin Fewer blood vessels than slow-twitch 28

29 13.3 Whole Muscle Contraction Muscle fibers come in 2 forms Slow-twitch fibers Rely on aerobic respiration Adapted for endurance Dark in color Many mitochondria Myoglobin Many blood vessels 29

30 13.3 Whole Muscle Contraction Types of muscle fibers Figure Fast-twitch and slow-twitch muscle fibers differ in structure. 30

31 13.3 Whole Muscle Contraction Exercise, exercise, exercise Exercise increases muscle strength, endurance, and flexibility. It increases cardiorespiratory endurance. HDL increases thus improving cardiovascular health. The proportion of protein to fat increases favorably. 31

32 13.3 Whole Muscle Contraction Exercise, exercise, exercise Exercise may prevent certain cancers: colon, breast, cervical, uterine, and ovarian. It improves density of bones thus decreasing the likelihood of osteoporosis. Exercise enhances mood and may relieve depression. 32

33 13.4 Whole Muscle Contraction Anabolic steroids Anabolic steroids are a group of steroids that usually increase protein production. The most common side effects are high blood pressure, jaundice, acne, and greatly increased risk of cancer. Abuse of these drugs may also cause impotence and shrinking of the testicles. Anabolic steroid use may lead to increased aggressiveness and violent mood swings. Are they worth the risk? Should they be legal to use in athletics? 33

34 13.4 Muscle Disorders Common muscle disorders Spasms sudden, involuntary muscle contractions that are usually painful Convulsions (seizures) multiple spasms of skeletal muscles Cramps strong, painful spasms often of the leg and foot 34

35 13.4 Muscle Disorders Common muscle disorders Strain stretching or tearing of a muscle Sprain twisting of a joint involving muscles, ligaments, tendons, blood vessels, and nerves 35

36 13.4 Muscle Disorders Muscular diseases Myalgia achy muscles due to injury or infection Fibromyalgia chronic achy muscles; not well understood Muscular dystrophy group of genetic disorders in which muscles progressively degenerate and weaken 36

37 13.4 Muscle Disorders Muscular diseases Myasthenia gravis autoimmune disorder that attacks the ACh receptor and weakens muscles of the face, neck, and extremities Amyotrophic lateral sclerosis (ALS) commonly known as Lou Gehrig s disease; motor neurons degenerate and die leading to loss of voluntary muscle movement Sarcomas cancers that originate in muscle, or the connective tissue associated with muscle 37

38 13.5 Homeostasis Homeostasis: The skeletal and muscular systems Both systems are involved with movement that allows us to respond to stimuli, digestion of food, return of blood to the heart, and moving air in and out of the lungs. Both systems protect body parts. Bones store and release calcium needed for muscle contraction and nerve impulse conduction. Blood cells are produced in the bone. Muscles help maintain body temperature. 38

39 13.5 Homeostasis How the skeletal and muscular systems interact with other body systems Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The muscular and skeletal systems work together to maintain homeostasis. The systems listed here in particular also work with these two systems. Muscular Systems The muscular system works with the skeletal system to allow movement and support and protection for internal organs. Muscle contraction provides heat to warm the body; bones play a role in Ca 2+ balance. These systems specifically help the other systems as mentioned below. Nervous System The nervous system coordinates the activity of muscles. Muscle contraction moves eyes, permits speech, and creates facial expressions. Endocrine System Growth and sex hormones regulate muscle development. Parathyroid hormone and calcitonin regulate Ca 2+ content of bones. Cardiovascular System Muscle contraction keeps blood moving in the heart and blood vessels, particularly the veins. Respiratory System Respiration provides the oxygen needed for ATP production so muscles can contract. Muscles assists in breathing Urinary System Muscle contraction moves the fluid within ureters, bladder, and urethra. Kidneys activate vitamin D needed for Ca2+ absorption and help maintain the blood level of Ca2+ for muscle contraction. Digestive System Reproductive System Muscle contraction moves gametes in oviducts, and uterine contraction occurs during childbirth. Androgens promote muscle growth. Muscle contraction accounts for chewing of food and peristaltic movement. The digestive system absorbs ions needed for muscle contraction. Figure The muscular system s contributions to homeostasis. 39