Ch. 10 Muscle and Tissue Organization

Question 1

Properties of Muscular Tissue

Answer 1

electrical excitability, contractility, extensibility, elasticity

Question 2

Structure of Skeletal Muscle

Answer 2

• skeletal muscle bundle consists of a body (belly) connected by tendons to the skeleton
• tendons are nearly avascular structure, composed of a parallel arrangement of collagen fibers at the ends of the muscle
• tendon is an extension of three connective tissue layers that surrounds the different organizational levels of a skeletal muscle

Question 3

Skeletal Muscle Connective Tissue Coverings

Answer 3

• muscle bundles are surrounded by epimysium, dense irregular tissue
• muscle fascicles (bundles) are surrounded by perimysium, transmits blood vessels
• muscle fibers are surrounded by endomysium, reticular fibers, bind muscle fibers together

Question 4

Deep Fascia

Answer 4

• an expansive sheet of dense irregular connective tissue
• separates individual muscles
• binds together muscles with similar functions
• forms sheaths to help distribute nerves, blood vessels, and lymphatic vessels
• fill spaces between muscles

Question 5

Microscopic Anatomy of a Skeletal Muscle Fiber

Answer 5

• muscle fibers while very small in diameter, run the length of the muscle bundle and are usually measured in inches
• muscle fibers are multinucleate, from before birth, and last a lifetime
• muscle growth after being born is due to hypertrophy (increased cell size) rather than hyperplasia (increased cell numbers)

Question 6

Filaments and the Sarcomere

Answer 6

• myofibrils are made of thick filaments (myosin) and thin filaments (actin) which in turn are made of protein
• these filaments are arranged in special compartments called sarcomeres (the functional unit of contraction)
• the pattern of overlap of thick and thin filaments consists of zones and bands which cause the striated appearance of skeletal muscle

Question 7

Muscle Proteins

Answer 7

• myofibrils are built from 3 kinds of proteins
  Contractile Proteins: generate force during contraction by sliding past each other rather than literally shortening ex. actin and myosin
  Regulatory Proteins: help switch the contraction process on and off ex. troponin and tropmyosin (covers myosin bind receptors)
  Structural Proteins: keep thick and thin filaments in proper alignment, give the myofibril elasticity and extensibility, and link the myofibrils to the sarcolemma and extracellular matrix ex. M line (hold myosin in centre) and Z-disc (actin attaches)

Question 8

Myosin

Answer 8

• major component of thick filaments

- functions as a motor protein that achieves movement by converting the chemical energy into mechanical energy

Question 9

Actin

Answer 9

• major component of thin filaments
• also contain the regulatory proteins, tropomyosin (covers binding site for myosin) and troponin (pull tropomyosin in or out)

Question 10

Microscopic Structure of Skeletal Muscle Fiber

Answer 10

muscle fiber cell (myofibrils)
myofilaments (thick and thin- striations)
- dark A-Band, thick and thin filaments overlapping, myosin and actin, contract and relaxation
- light I-Band, contain only thin filaments, only actin, causes only muscle movement

Question 11

Nerve and Blood Supply of Skeletal

Answer 11

• most receive one nerve that supplies them with motor and sensory functions, other muscles receive multiple nerves
• nerves typically enter a muscle with blood vessels as a unit called a neuromuscular bundle
• these nerves carry both sensory and motor info

Question 12

Somatic Motor Neurons

Answer 12

• individual cells (neurons) that innervate skeletal muscle fibers are called

Question 13

Neuromuscular Junction (NMJ)

Answer 13

• is a point of near-contact between a somatic motor neuron and a skeletal muscle fiber
• each muscle fiber has one NMJ, yet the axon of a somatic motor neuron branches out and form NMJs with many different muscle fibers

Question 14

Motor Unit

Answer 14

• one somatic motor neuron plus all the skeletal muscle fibers it stimulates is called a motor unit

Question 15

Sliding Filament Mechanism Theory

Answer 15

• During contraction of a muscle fiber:
  1. distance between Z-discs shortens (holds actin)
  2. distance between A- remains the same (overlap of thick and thin, myosin doesn’t move)
  3. distance between I- band shortens (only actin)
  4. distance between H-zone shortens (only myosin)
• distance between 2 Z-discs is sacromere

Question 16

Muscle Attachment Sites: Origin and Insertion

Answer 16

• skeletal muscles cause movements by exerting force on tendons, which pulls on bones or other structures
• articulating bones usually do not move equally in response to contraction
• attachment of a tendon to the stationary bone is called the origin
• attachment of the muscle’s other tendon to the movable bone is called the insertion
• the action of a muscle are the main movements that occur during contraction (flexion or extension)

Question 17

Coordination among muscles

Answer 17

• movements usually result from several skeletal muscles acting as a group, most skeletal muscles are arranged in opposing pairs at joints (ex. flexors vs extensors)
  Agonist: (prime mover) produces specific movement when it contracts (biceps brachii)
  Antagonist: is a muscle whose action opposes that of an agonist (triceps brachii would be antagonist)
  Synergist: is a muscle that assist the agonist or prime mover

Question 18

Muscle Fascicle Arragement

Answer 18

• all muscle fibers are parallel to one another within a single fascicle
• fascicles, however, form patterns with respect to the tendons
• parallel (sternohyoid), fusiform, circular, triangular (pectoralias), pennate (uni, bi, multi)

Question 19

Cardiac Muscle Cells

Answer 19

• striated, involuntary, branched, and uninucleate
• intercellular connections points (intercalated discs) contain structural and electrical connections, called desmosomes and gap junctions
• cardiac tissue is capable of autorhythmicity, an ability to spontaneously generate impulses that trigger contraction

Question 20

Smooth Muscle Tissue

Answer 20

• composed of short muscle fibers that have a fusiform shape and single centrally located nucleus
• thick and thin filaments are not precisely aligned so no visible striations or sarcomeres are present
• Z discs are absent- thin filaments are attached to dense bodies by elements of the cytoskeleton
• sarcoplasmic reticulum is sparse
• transverse tubules are absent
• contraction is slow, resistant to fatigue, and usually sustained for an extended period of time
• takes longer than skeletal muscle to contract and relax
• contraction is under involuntary control

Question 21

Functions of Muscular Tissue

Answer 21

Body movements, body stability, storing anf moving substances, heat production

Question 22

Sacrolemma

Answer 22

plasma membrane of a skeletal muscle fiber

Question 23

T Tubles

Answer 23

extensions of the sacrolemma that tunnel throughout the muscle fiber, are open to the outside, and filled with ISF

Question 24

Sacroplasma

Answer 24

cytoplasm of a skeletal fiber