Types and Properties of Muscles
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Questions and Answers

Which property of muscle refers to its ability to return to its original shape after being stretched?

  • Contractibility
  • Excitability
  • Extensibility
  • Elasticity (correct)
  • Osteoarthritis is characterized by the progressive loss of cartilage in the joints.

    True

    What is the main function of synovial fluid in synovial joints?

    To lubricate and reduce friction between joint surfaces

    The muscle that opposes the action of another muscle is called the ______.

    <p>antagonist</p> Signup and view all the answers

    Match the following types of joints with their characteristics:

    <p>Fibrous = Joints with no movement Cartilaginous = Joints that allow limited movement Synovial = Joints allowing free movement Hinge = A type of synovial joint that permits bending and straightening</p> Signup and view all the answers

    Which of the following can lead to changes in DNA methylation patterns?

    <p>Chronic stress</p> Signup and view all the answers

    Maternal nutrition during pregnancy does not influence the epigenetic changes in the developing fetus.

    <p>False</p> Signup and view all the answers

    What kind of environmental factors can cause epigenetic modifications?

    <p>Nutrition and toxin exposure</p> Signup and view all the answers

    Exposure to environmental toxins can alter DNA _____ patterns associated with diseases.

    <p>methylation</p> Signup and view all the answers

    Match the environmental factor with its effect on epigenetics:

    <p>Maternal Nutrition = Metabolic health in offspring Chronic Stress = Changes in histone acetylation Heavy Metal Exposure = Altered DNA methylation patterns Endocrine Disruptors = Association with cancer risks</p> Signup and view all the answers

    Which of the following statements about the epigenome is true?

    <p>Some epigenetic changes can be stably inherited.</p> Signup and view all the answers

    All epigenetic modifications occur irreversibly and cannot be changed.

    <p>False</p> Signup and view all the answers

    How does the epigenome respond to environmental changes?

    <p>It responds dynamically, allowing organisms to adapt.</p> Signup and view all the answers

    Environmental factors such as _____ can influence stress-related gene expression.

    <p>chronic stress</p> Signup and view all the answers

    Which of the following aspects is influenced by maternal nutrition during pregnancy?

    <p>Epigenetic changes in the fetus</p> Signup and view all the answers

    What is the primary function of tRNA in protein synthesis?

    <p>To transfer specific amino acids to the ribosome</p> Signup and view all the answers

    What component of a nucleotide is responsible for forming the backbone of DNA?

    <p>Phosphate group</p> Signup and view all the answers

    The start codon AUG signals the termination of protein synthesis.

    <p>False</p> Signup and view all the answers

    What role does RNA polymerase play in transcription?

    <p>RNA polymerase synthesizes RNA by transcribing the bases on a DNA template.</p> Signup and view all the answers

    DNA consists of a single strand of nucleotides.

    <p>False</p> Signup and view all the answers

    What is the role of histones in the packaging of DNA into chromosomes?

    <p>Histones organize DNA into a compact structure.</p> Signup and view all the answers

    The genetic code is stored in sequences of nucleotides in DNA, grouped into _____ which correspond to specific amino acids.

    <p>codons</p> Signup and view all the answers

    During DNA replication, the enzyme __________ unwinds the DNA strands.

    <p>DNA helicase</p> Signup and view all the answers

    Match the following molecules with their roles in translation:

    <p>tRNA = Transfers amino acids to ribosomes rRNA = Forms ribosomes mRNA = Carries genetic information from DNA anticodon = Pairs with codons on mRNA</p> Signup and view all the answers

    Which of the following modifications to histones usually enhances gene expression?

    <p>Acetylation</p> Signup and view all the answers

    Match the following types of RNA with their roles in protein synthesis:

    <p>mRNA = Carries genetic information from DNA to ribosome tRNA = Transports amino acids to the ribosome rRNA = Forms the structural component of ribosomes</p> Signup and view all the answers

    Which nitrogenous base is found in RNA but not in DNA?

    <p>Uracil</p> Signup and view all the answers

    Epigenetics involves changes to DNA sequences that affect gene expression.

    <p>False</p> Signup and view all the answers

    The two strands of DNA run in the same direction.

    <p>False</p> Signup and view all the answers

    How does tightly packed chromatin affect transcription?

    <p>It restricts access to the transcription machinery.</p> Signup and view all the answers

    What is the purpose of DNA ligase in DNA replication?

    <p>DNA ligase seals gaps between sections of newly synthesized DNA.</p> Signup and view all the answers

    Changes in protein shape can affect their _____ and activity.

    <p>function</p> Signup and view all the answers

    In a chromosome, sister chromatids are joined at a region called the __________.

    <p>centromere</p> Signup and view all the answers

    What influences gene expression according to environmental factors?

    <p>Environmental conditions and histone modifications</p> Signup and view all the answers

    What is the main function of messenger RNA (mRNA)?

    <p>Carries genetic information from DNA to the ribosome</p> Signup and view all the answers

    Study Notes

    Types of Muscles

    • Skeletal muscle (striated): Voluntary, attached to bones, responsible for movement
    • Smooth muscle: Involuntary, found in internal organs, responsible for organ function
    • Cardiac muscle: Involuntary, found in the heart, rhythmic contractions for blood circulation

    Properties of Muscle

    • Elasticity: Ability to return to original shape after stretching
    • Extensibility: Ability to stretch beyond resting length
    • Contractibility: Ability to shorten and generate force
    • Excitability: Ability to respond to stimuli, such as nerve impulses

    Structure of Skeletal Muscle and Skeletal Muscle Fibres

    • Skeletal muscle is composed of bundles of muscle fibres
    • Muscle fibres are long, cylindrical cells containing myofibrils
    • Myofibrils are made up of actin (thin filaments) and myosin (thick filaments)

    Structure of Myofibrils

    • Sarcomere: Basic unit of muscle contraction
    • Actin and myosin filaments are arranged in repeating units called sarcomeres
    • Z-lines: Mark the boundaries of each sarcomere
    • A-band: Region containing both actin and myosin filaments
    • I-band: Region containing only actin filaments
    • H-zone: Region containing only myosin filaments

    Sliding Filament Theory

    • Muscle contraction: Occurs when myosin filaments slide past actin filaments
    • Myosin heads: Pull on actin filaments, shortening the sarcomere
    • ATP: Required for the sliding process and muscle contraction

    How Muscles and Bones Work Together

    • Muscles contract and pull on bones, causing movement
    • Joints: Allow movement between bones
    • Tendons: Connect muscles to bones

    Antagonist and Agonist Pairings and Synergists

    • Agonist: Muscle responsible for the main movement
    • Antagonist: Muscle that opposes the movement of the agonist
    • Synergist: Muscle that helps the agonist perform the movement

    Origin and Insertion Points

    • Origin: Point where a muscle is attached to a stationary bone
    • Insertion: Point where a muscle is attached to a moving bone
    • Muscle contraction: Causes the insertion point to move toward the origin

    Muscle Tone

    • Muscle tone: State of slight tension in muscles even at rest
    • Helps maintain posture, stability, and readiness for action

    Functions of Skeleton

    • Support: Provides framework for the body
    • Protection: Protects vital organs
    • Movement: Provides attachment points for muscles
    • Mineral storage: Stores calcium and phosphorus
    • Blood cell production: Red bone marrow produces blood cells

    Types of Bone

    • Compact bone: Dense, hard outer layer
    • Spongy bone: Porous, lighter inner layer
    • Cartilage: Flexible, connective tissue: hyaline cartilage (found in joints), elastic cartilage (found in ears), fibrocartilage (found in intervertebral discs)

    Bones of the Skeleton

    • Axial skeleton: Skull, vertebral column, ribs, sternum
    • Appendicular skeleton: Bones of the limbs, shoulder girdle, and pelvic girdle

    Macroscopic Structure of Long Bones

    • Diaphysis: Shaft of the bone
    • Epiphysis: Ends of the bone
    • Periosteum: Outer membrane covering the bone
    • Medullary cavity: Hollow space within the diaphysis
    • Endosteum: Membrane lining the medullary cavity

    Structure of Compact Bone

    • Osteons: Basic units of compact bone
    • Central canal: Contains blood vessels and nerves
    • Concentric lamellae: Rings of bone tissue surrounding the central canal
    • Lacunae: Small spaces that house osteocytes (bone cells)
    • Canaliculi: Tiny channels that connect lacunae, allowing for nutrient and waste exchange

    Structure of Spongy Bone

    • Trabeculae**: Interconnecting plates of bone tissue
    • Red bone marrow: Found within trabeculae, produces blood cells

    Joints

    • Fibrous joints: Immovable, united by fibrous connective tissue (e.g., sutures in skull)
    • Cartilaginous joints: Slightly movable, united by cartilage (e.g., intervertebral discs)
    • Synovial joints: Freely movable, characterized by joint capsule, synovial fluid and articular cartilage

    Structure of Synovial Joint

    • Articular cartilage: Smooth, slippery layer covering the ends of bones
    • Joint capsule: Fibrous sac that encloses the joint
    • Synovial membrane: Inner lining of the joint capsule, secretes synovial fluid
    • Synovial fluid: Lubricates the joint and reduces friction

    Types of Synovial Joints

    • Ball and socket: One bone fits into a cup-like socket, allows for all types of movement (e.g., shoulder, hip)
    • Hinge: Allows for movement in one plane (e.g., elbow, knee)
    • Pivot: Allows for rotation around a central axis (e.g., between radius and ulna)
    • Saddle: Allows for movement in two planes (e.g., thumb joint)
    • Condyloid: Allows for movement in two planes, but with limited rotation (e.g., wrist)
    • Gliding: Allows for sliding movement (e.g., between carpal bones)

    Flexion/Extension, Abduction/Adduction, Rotation

    • Flexion: Decreases the angle at a joint
    • Extension: Increases the angle at a joint
    • Abduction: Moves a limb away from the midline
    • Adduction: Moves a limb towards the midline
    • Rotation: Turning movement around an axis

    Osteoporosis

    • Weakening of bones: Due to loss of bone density
    • Increased risk of fractures
    • Risk factors: Age, female sex, family history, lack of calcium, vitamin D deficiency, smoking, alcohol abuse

    Osteoarthritis

    • Degenerative joint disease: Caused by wear and tear on joint cartilage
    • Joint pain, stiffness, and swelling
    • Risk factors: Age, obesity, injury, overuse, genetics

    DNA Structure

    • DNA is a double helix composed of two strands running in opposite directions (antiparallel).
    • Each strand is made up of nucleotides, which consist of a phosphate group, a deoxyribose sugar, and a nitrogenous base.
    • Four nitrogenous bases are present: adenine (A), guanine (G), cytosine (C), and thymine (T).
    • Bases pair specifically: A with T, and C with G, forming the steps of the DNA ladder through hydrogen bonds.

    Chromosomes

    • DNA is packaged into chromosomes through chromatin formation, where DNA wraps around histone proteins.
    • This creates nucleosomes, further coiled into the compact structure of chromosomes.
    • During mitosis and meiosis, chromosomes condense, becoming visible under a microscope.
    • Each chromosome consists of two identical sister chromatids joined at the centromere, crucial for proper chromosome segregation during cell division.

    DNA Replication

    • DNA replication involves the separation of the two strands by DNA helicase, breaking hydrogen bonds.
    • DNA polymerase then adds complementary nucleotides to the template strands, creating new strands.
    • DNA ligase seals any gaps between sections, resulting in two identical DNA molecules.
    • DNA polymerase has proofreading capabilities, correcting errors during replication.

    RNA and Its Types

    • RNA differs from DNA in being single-stranded, containing ribose sugar instead of deoxyribose, and having uracil (U) in place of thymine (T).
    • Three main types of RNA:
      • mRNA (messenger RNA): carries genetic information from DNA to the ribosome for protein synthesis.
      • tRNA (transfer RNA): carries specific amino acids to the ribosome, recognizing codons through its anticodons.
      • rRNA (ribosomal RNA): combines with proteins to form ribosomes, facilitating translation.
    • RNA polymerase transcribes DNA, creating a complementary RNA molecule.

    From DNA to Proteins

    • Genetic code is stored in DNA as sequences of nucleotides grouped into codons (three-nucleotide sequences).
    • Each codon corresponds to a specific amino acid.
    • tRNA carries the appropriate amino acid to the ribosome, where anticodons pair with codons to ensure the correct amino acid sequence.
    • Start codons (AUG) initiate translation, while stop codons (UAA, UAG, UGA) signal its termination.

    Transcription

    • Transcription is triggered by chemical messengers entering the nucleus.
    • It begins with a DNA strand unzipping by helicase.
    • RNA polymerase transcribes the template strand of DNA, copying information and base pairing.
    • RNA polymerase joins complementary nucleotides of mRNA to the base pairings on the DNA.
    • When a sequence signals the end, RNA polymerase detaches.

    Translation

    • Translation decodes mRNA into a polypeptide chain by ribosomes.
    • tRNA carries specific amino acids based on their anticodons, pairing with codons on mRNA.
    • rRNA forms ribosomes, facilitating translation.
    • The ribosome ensures correct amino acids are added by matching codon-anticodon pairs.

    Gene Expression and Regulation

    • Gene expression is influenced by various factors including transcription factors, environmental conditions, and modifications to histones and DNA.
    • Protein shape changes affect their function and activity.
    • Acetylation, the addition of an acetyl group to histones, relaxes the chromatin structure, making DNA more accessible for transcription, enhancing gene expression.
    • Methylation, the addition of a methyl group to DNA or histones, can either restrict access to RNA polymerase, inhibiting gene expression, or relax the chromatin, increasing transcription.

    Epigenetics

    • Epigenetics studies environmental and non-genetic factors influencing gene expression without altering the DNA sequence.
    • Epigenetic mechanisms allow cells to respond to external stimuli and lead to phenotypic variations without modifying the genetic code.
    • DNA methylation and histone modification contribute to epigenetic regulation:
      • DNA methylation: adding methyl groups to DNA, typically at cytosine residues, can repress gene expression.
      • Histone modification: altering chromatin structure through acetylation, methylation, or phosphorylation, affecting gene expression.
    • Epigenetic changes can be inherited across generations, impacting offspring health and disease susceptibility.

    Chromatin

    • Chromatin is the complex of DNA and proteins (histones) forming chromosomes within the nucleus.
    • Chromatin packing affects DNA accessibility for transcription:
      • Tightly packed chromatin restricts access to transcription machinery.
      • Loosely packed chromatin allows for active gene expression.
    • Acetylation of histones relaxes chromatin structure, facilitating gene transcription.
    • Methylation can activate or repress gene expression depending on the histone and location.

    Environmental Impacts on the Epigenome

    • Environmental factors like diet, stress, and exposure to toxins influence the epigenome.
    • These factors can cause changes in DNA methylation and histone modifications, altering gene expression patterns.
    • Examples of environmental changes causing epigenetic modifications affecting health:
      • Maternal nutrition during pregnancy can impact metabolic health later in life.
      • Toxin exposure can alter DNA methylation patterns associated with diseases like cancer.
    • The epigenome responds dynamically to environmental changes, potentially impacting offspring traits through inheritance.

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    Description

    This quiz covers the different types of muscles including skeletal, smooth, and cardiac muscle. Additionally, it explores the properties of muscles such as elasticity, extensibility, and contractibility, as well as the structure of skeletal muscle and myofibrils. Test your knowledge on the fundamental aspects of muscular anatomy and physiology.

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