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Questions and Answers
What determines the precision of muscle control?
What determines the precision of muscle control?
What does the all-or-none principle state regarding muscle fibers in a motor unit?
What does the all-or-none principle state regarding muscle fibers in a motor unit?
What is a characteristic of Type I muscle fibers?
What is a characteristic of Type I muscle fibers?
What are proprioceptors responsible for during muscle activity?
What are proprioceptors responsible for during muscle activity?
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What happens when a muscle is stretched according to the function of muscle spindles?
What happens when a muscle is stretched according to the function of muscle spindles?
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What is the role of Golgi tendon organs (GTO) during intense muscle load?
What is the role of Golgi tendon organs (GTO) during intense muscle load?
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How can the force output of a muscle be varied?
How can the force output of a muscle be varied?
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What describes unfused tetanus in motor unit activity?
What describes unfused tetanus in motor unit activity?
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What is the primary function of the skeletal system?
What is the primary function of the skeletal system?
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Which type of joint allows for virtually no movement?
Which type of joint allows for virtually no movement?
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How many bones compose the adult human skeleton?
How many bones compose the adult human skeleton?
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Which part of the skeleton consists of the skull, vertebral column, ribs, and sternum?
Which part of the skeleton consists of the skull, vertebral column, ribs, and sternum?
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Which type of joint operates in two perpendicular axes?
Which type of joint operates in two perpendicular axes?
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What is the role of epimysium in the muscular system?
What is the role of epimysium in the muscular system?
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What is the characteristic feature of synovial joints?
What is the characteristic feature of synovial joints?
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How are the cervical vertebrae categorized in the vertebral column?
How are the cervical vertebrae categorized in the vertebral column?
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What is the primary function of the respiratory system?
What is the primary function of the respiratory system?
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What happens to alveolar pressure during inspiration?
What happens to alveolar pressure during inspiration?
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Which pressure controls the movement of air during breathing?
Which pressure controls the movement of air during breathing?
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What is the role of hemoglobin in red blood cells?
What is the role of hemoglobin in red blood cells?
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How does the diffusion process occur in the respiratory system?
How does the diffusion process occur in the respiratory system?
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What is the role of the inhibitory interneuron activated by the sensory neuron of the GTO?
What is the role of the inhibitory interneuron activated by the sensory neuron of the GTO?
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Which of the following is NOT a method for athletes to improve force production?
Which of the following is NOT a method for athletes to improve force production?
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How do the valves of the heart function?
How do the valves of the heart function?
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What is the main function of hemoglobin in the blood?
What is the main function of hemoglobin in the blood?
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What characterizes the conduction system of the heart?
What characterizes the conduction system of the heart?
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What best describes how blood vessels operate in the circulatory system?
What best describes how blood vessels operate in the circulatory system?
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What is the consequence of bradycardia?
What is the consequence of bradycardia?
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Which part of the heart pumps blood to the rest of the body?
Which part of the heart pumps blood to the rest of the body?
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What is the function of the epimysium in muscle tissue?
What is the function of the epimysium in muscle tissue?
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Which protein filaments are primarily responsible for the striated appearance of skeletal muscle?
Which protein filaments are primarily responsible for the striated appearance of skeletal muscle?
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During muscle contraction, what happens to the bands and zones in a myofibril?
During muscle contraction, what happens to the bands and zones in a myofibril?
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What initiates the release of calcium in muscle fibers?
What initiates the release of calcium in muscle fibers?
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Which phase in the sliding-filament theory involves the actual shortening of the muscle fiber?
Which phase in the sliding-filament theory involves the actual shortening of the muscle fiber?
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Which of the following is NOT needed for crossbridge cycling between actin and myosin?
Which of the following is NOT needed for crossbridge cycling between actin and myosin?
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What is the main role of a motor unit in muscle function?
What is the main role of a motor unit in muscle function?
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What occurs at the sarcolemma when a sufficient amount of acetylcholine is released?
What occurs at the sarcolemma when a sufficient amount of acetylcholine is released?
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Study Notes
Skeletal System
- The adult human body is composed of 206 bones.
- The skeletal system provides leverage, support, and protection.
- Muscles pull on bones to allow the body to push or pull against external objects.
Axial Versus Appendicular Skeleton
- The axial skeleton comprises the skull, vertebral column (C1-coccyx), ribs, and sternum.
- The appendicular skeleton consists of the shoulder girdle; bones of the arms, wrists, hands, and pelvic girdle; and bones of the legs, ankles, and feet.
Types of Joints
- Joints are junctions of bones.
- Fibrous joints allow virtually no movement. An example is the sutures of the skull.
- Cartilaginous joints allow limited movement. An example is the intervertebral joints.
- Synovial joints allow considerable movement. An example is the elbows and knees.
Types of Joints (continued)
- Uniaxial joints operate as a hinge, rotating about one axis. An example is the elbow.
- Biaxial joints operate in two perpendicular axes. An example is the ankle and wrist.
- Multiaxial joints allow movement in all three axes. An example is the shoulder and hip.
Vertebral Column
- Vertebral bones are separated by flexible disks that allow for movement.
- There are 7 cervical vertebrae (neck region), 12 thoracic vertebrae (upper back), 5 lumbar vertebrae (lower back), 5 sacral vertebrae (make up rear of pelvis), and 3-5 coccygeal vertebrae (form vestigial tail extending down from the pelvis).
Muscular System
- Each skeletal muscle is an organ that contains muscle tissue, connective tissue, nerves, and blood vessels.
- Fibrous connective tissue, or epimysium, covers the body’s more than 430 skeletal muscles.
- There are three types of connective tissue: epimysium, perimysium, and endomysium.
Motor Unit
- A motor unit consists of a motor neuron and the muscle fibers it innervates.
- Typically several hundred muscle fibers are contained in a single motor unit.
Myosin and Actin
- The arrangement of myosin (thick) and actin (thin) filaments gives skeletal muscle its striated appearance.
- The discharge of an action potential from a motor nerve signals the release of calcium from the sarcoplasmic reticulum into the myofibril, causing tension development in muscle.
Muscular System
- The sliding-filament theory of muscular contraction states that the actin filaments at each end of the sarcomere slide inward on myosin filaments, pulling the Z-lines toward the center of the sarcomere and thus shortening the muscle fiber.
Contraction of a Myofibril
- When muscle contracts, the I-bands and H-zone are shortened.
- With completely contracted muscle, there is low force potential due to reduced crossbridge–actin alignment.
Muscular System
- The sliding-filament theory of muscular contraction involves five phases: resting phase, excitation-contraction coupling phase, contraction phase, recharge phase, and relaxation phase.
Key Points
- The number of crossbridges formed between actin and myosin at any instant dictates the force production of a muscle.
- Calcium and ATP are necessary for crossbridge cycling with actin and myosin filaments.
Neuromuscular System
- The arrival of the action potential at the nerve terminal causes the release of acetylcholine. Once a sufficient amount of acetylcholine is released, an action potential is generated across the sarcolemma, and the fiber contracts.
Neuromuscular System (continued)
- The extent of control of a muscle depends on the number of muscle fibers within each motor unit. Muscles that function with great precision may have as few as one muscle fiber per motor neuron. Muscles that require less precision may have several hundred fibers served by one motor neuron.
Key Term
- All-or-none principle: All of the muscle fibers in the motor unit contract and develop force at the same time.
Stimulated Motor Unit
- A single twitch results from a single electrical stimulus delivered to a motor nerve.
- Twitch summation is the increase in force resulting from a summation of two twitches.
- Unfused tetanus results from repetitive stimuli that do not allow for complete muscle relaxation between stimuli.
- Fused tetanus results from a high frequency of stimulation that does not allow for any relaxation between stimuli.
Neuromuscular System
- Muscle fiber types: Type I (slow-twitch), Type IIa (fast-twitch), and Type IIx (fast-twitch).
Key Point
- Motor units are composed of muscle fibers with specific morphological and physiological characteristics that determine their functional capacity.
Neuromuscular System
- The force output of a muscle can be varied through change in the frequency of activation of individual motor units or change in the number of activated motor units.
Key Point
- The force output of a muscle can be varied through change in the frequency of activation of individual motor units or change in the number of activated motor units.
Key Point
- Proprioceptors are specialized sensory receptors that provide the central nervous system with information needed to maintain muscle tone and perform complex coordinated movements.
Proprioception
- Muscle spindles are proprioceptors located in muscle fibers that respond to changes in muscle length.
Proprioception
- When a muscle is stretched, deformation of the muscle spindle activates the sensory neuron, which sends an impulse to the spinal cord, where it synapses with a motor neuron, causing the muscle to contract.
Proprioception
- Golgi tendon organs (GTO) are proprioceptors located in tendons near the myotendinous junction that respond to changes in muscle tension.
- They occur in series with extrafusal muscle fibers.
Golgi Tendon Organ
- When an extremely heavy load is placed on the muscle, discharge of the GTO occurs, activating an inhibitory interneuron in the spinal cord which synapses with and inhibits a motor neuron serving the same muscle.
Neuromuscular System
- To improve force production incorporate phases of training that use heavier loads to optimize neural recruitment.
- Increase the cross-sectional area of muscles involved in the desired activity.
- Perform multimuscle, multijoint exercises that can be done with more explosive actions to optimize fast-twitch muscle recruitment.
Cardiovascular System
- The heart is a muscular organ made up of two interconnected but separate pumps: the right ventricle pumps blood to the lungs and the left ventricle pumps blood to the rest of the body.
Cardiovascular System
- Valves: Tricuspid valve, mitral (bicuspid) valve, aortic valve, and pulmonary valve. Valves open and close passively, depending on the pressure gradient.
- Conduction system: Controls the mechanical contraction of the heart.
Electrical Conduction System
- The electrical conduction system of the heart is a network of specialized muscle fibers that conduct electrical impulses throughout the heart.
Cardiac Conduction
- Rhythmicity and conduction properties of myocardium are influenced by the cardiovascular center of the medulla.
- Signals are transmitted through sympathetic and parasympathetic nervous systems.
- Bradycardia is a heart rate of less than 100 beats per minute.
Cardiovascular System
- Electrocardiogram is a graphic representation of the electrical activity of the heart.
Electrocardiogram
- An electrocardiogram is used to detect abnormalities in the heart's electrical activity.
Cardiovascular System
- Blood vessels operate in a closed-circuit system.
- The arterial system carries blood away from the heart.
- The venous system returns blood toward the heart.
Distribution of Blood
- The distribution of blood throughout the circulatory system at rest is about 64% in the venous system, 13% in the arterial system, and 9% in the capillaries.
Cardiovascular System
- Arteries are blood vessels that carry blood away from the heart.
- Capillaries are tiny blood vessels that connect arteries and veins.
- Veins are blood vessels that carry blood back to the heart.
Cardiovascular System
- Blood contains red blood cells, white blood cells, platelets, and plasma.
- Hemoglobin transports oxygen and serves as an acid–base buffer.
- Red blood cells facilitate carbon dioxide removal.
Key Point
- The cardiovascular system transports nutrients and removes waste products while helping to maintain the environment for all the body’s functions.
Respiratory System
- The primary function of the respiratory system is the basic exchange of oxygen and carbon dioxide.
Respiratory System (continued)
- The amount and movement of air and expired gases in and out of the lungs are controlled by expansion and recoil of the lungs.
Respiratory System (continued)
- Pleural pressure is the pressure in the narrow space between the lung pleura and the chest wall pleura.
Respiratory System (continued)
- Alveolar pressure is the pressure inside the alveoli when the glottis is open and no air is flowing into or out of the lungs.
Respiratory System (continued)
- The process of diffusion is a simple random motion of molecules moving in opposite directions through the alveolar capillary membrane.
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Description
Test your knowledge of the skeletal system, including the different types of bones and joints in the human body. Understand the differences between the axial and appendicular skeletons, as well as the classifications and functions of various joints. This quiz covers essential concepts related to human anatomy.
