Muscles and Muscle Tissue Lab 7 Muscles and Muscle Tissue Gilbert R. Pitts, Ph.D., Joseph R. Schiller, Ph.D., and Amy L. Thompson, Ph.D.

Lab 7 Activities Review histology of skeletal, cardiac, and smooth muscle (macerated and intact) Identify structures of sarcomeres on electron micrographs [ultrastructure] Describe how the arrangement of fascicles in a muscle relates to power and range of motion Describe the classification of muscles into functional groups Describe the conventions used in the naming of muscles Identify the muscles and their actions on models and diagrams Use PhysioEx Exercise 2--Skeletal Muscle Physiology to learn basic concepts of muscle physiology: latent period, treppe, multiple motor unit summation/recruitment, and temporal summation (including tetany)

Some Muscle Terminology Myology: the scientific study of muscle muscle fibers = muscle cells myo, mys & sarco: word roots referring to muscle Three Types of Muscle: skeletal, cardiac, and smooth They differ in: microscopic anatomy -- location -- regulation by the endocrine system and the nervous system

Characteristics of Skeletal Muscle Attached to bones Voluntary (conscious) control (usually) Contracts quickly, tires easily (fatigable) Undergoes graded contraction

Skeletal Muscle Cells Long, cylindrical cells Striated (banded) Multinucleate

Striations /Sarcomeres Z discs (lines): the boundary between sarcomeres; proteins anchor the thin filaments A (anisotropic) band: overlap of thick (myosin) filaments & thin filaments I (isotropic) band: thin (actin) filaments only Z line: bisects each I band H zone: thick filaments only M line: proteins anchor the adjacent thick filaments

Sarcomeres Components of the muscle fiber with myofilaments arranged into contractile units The functional unit of striated muscle contraction Produce the visible banding pattern (striations) The myofilaments between two successive z discs Sliding filament mechanism for contraction

Characteristics of Cardiac Muscle Forms most of heart wall (myocardium) Involuntary (unconscious) Autorhythmicity (contracts w/out external stimuli) Fast contraction, non-fatigable Intrinsic rhythm modified by neural and hormonal signals

Cardiac Muscle Cells Striated Uninucleate Branched Intercalated discs gap junctions desmosomes

Characteristics of Smooth Muscle found in the walls of hollow internal structures (digestive, respiratory, reproductive tracts, blood vessels) Arrector pili, pupil of the eye, etc. Involuntary (unconscious) & may be autorhythmic Long, slow contractions, non-fatigable

Smooth Muscle Cells Nonstriated = smooth (no sarcomeres) Uninucleate May gap junctions

Smooth Muscle Cells Actin and Myosin contractile proteins are not organized into sarcomeres; instead the fibers attach to the dense bodies under the cell membrane

Connective Tissue Coverings of Skeletal Muscle Superficial Fascia: "hypodermis" Deep Fascia: lines body walls & extremities; binds muscle together, separating them into functional groups Epimysium: wraps an entire muscle Perimysium: subdivides each muscle into fascicles, bundles of 10-100 muscle fibers Endomysium: wraps individual muscle fibers

Arrangement of Fascicles Range of motion: depends on length of muscle fibers (fascicles); long fibers = large range of motion parallel and fusiform muscles Power: depends on total number of muscle fibers; many fibers = great power convergent, pennate, bipennate, multipennate

Attachments (to bone) Derived from connective tissue elements: insertion: the part of a muscle attached to the bone that moves (relative to a particular motion) origin: the part of a muscle attached to the stationary bone direct attachment: connective tissue coverings fused directly to periosteum indirect attachment: connective tissue coverings gathered into a tendon or aponeurosis that attaches to periosteum tendon: cord (of dense regular connective tissue) aponeurosis: sheet (of dense regular connective tissue)

The Neuromuscular Junction Structure where motor neuron communicates with skeletal muscle fiber Two parts: Axon terminal Motor end plate Separated by synaptic cleft

Summary of Muscle Structure

Muscle Functional Groups Muscles are classified into functional groups according to their role in producing a particular movement: prime mover(s) (= agonists): the muscle(s) primarily responsible for the movement antagonist(s):  the muscle(s) that oppose (or reverse) the movement caused by the prime mover. synergist(s):  the muscle(s) that assist the prime mover fixator(s): the muscle(s) that immobilize the origin of the prime mover

Naming Skeletal Muscles Location of the muscle Shape of the muscle Relative Size of the muscle Direction/Orientation of the muscle fibers/cells Number of Origins Location of the Attachments Action of the muscle Know the muscle names as described in Lab Manual Lab 7 (pp. Lab 7-1 to Lab 7-24)

Muscles Named by Location Epicranius (around cranium) Tibialis anterior (front of tibia) tibialis anterior

Naming Skeletal Muscles by Shape Trapezius Deltoid (triangle) Trapezius (trapezoid, 2 parallel sides) Serratus (saw-toothed) Rhomboideus (rhomboid, 4 parallel sides) Orbicularis and sphincters (circular) Deltoid Rhomboideus major Serratus anterior

Muscles Named by Size Psoas minor Maximus (largest) Minimis (smallest) Longus (longest) Brevis (short) Major (large) Minor (small) Psoas major

Muscles Named by Direction of Fibers Rectus (straight) - parallel to the body’s long axis Oblique rectus abdominis external oblique transversus abdominis Transverse – at right angles to the body’s long axis

Muscles Named for Number of Origins Biceps (2) Triceps (3) Quadriceps (4) biceps brachii

Muscles Named for Origin and Insertion Sternocleidomastoid originates from sternum and clavicle and inserts on mastoid process of temporal bone origins

Muscles Named for Action Flexor carpi radialis (extensor carpi radialis) –flexes wrist Abductor pollicis brevis (adductor pollicis) –flexes thumb Abductor magnus – abducts thigh Extensor digitorum – extends fingers adductor magnus

Skeletal Muscles Know the muscles, their origins and insertions as described in your Lab Manual 7.

Contraction of a Skeletal Muscle The Motor Unit = Motor Neuron + Muscle Fibers to which it connects (Synapses)  

Myogram: The Recording of Electrical Activity During Muscle Contraction Stimulus: nerve impulse or electrical charge All or none rule: all the muscle fibers of a motor unit contract all the way   Twitch: a single contraction of all the muscle fibers in a motor unit (one nerve signal)  

Components of the Myogram 1. latent period: delay between stimulus and response   2. contraction phase: tension or shortening occurs   3. relaxation phase: relaxation or lengthening   refractory period: time interval after excitation when muscle will not respond to a new stimulus

Contraction of a Skeletal Muscle Graded muscle responses - moving a load Force of muscle contraction varies depending on needs - how much tension is needed? Twitch does not provide much force Contraction force can be altered in 3 ways: 1. changing the frequency of stimulation 2. changing the force of stimulation 3. changing the muscle’s length

Graded Muscle Responses Twitch: a single contraction Wave (temporal) summation: contractions repeated before complete relaxation, leads to progressively stronger contractions

Graded Muscle Responses Unfused (incomplete) tetanus: frequency of stimulation allows only incomplete relaxation   Fused (complete) tetanus: frequency of stimulation allows no relaxation  

Graded Muscle Responses Treppe: the staircase effect “warming up” of muscle

Multiple Motor Unit Summation ( Recruitment) The stimulation of more motor units leads to more forceful muscle contraction  

Contraction of a Skeletal Muscle Isometric Contraction = Muscle does not shorten Tension increases

Contraction of a Skeletal Muscle Isotonic Contraction = tension does not change Length shortens

Force of Contraction 1. Number of muscle fibers contracting (recruitment) 2. Size of muscle 3. Series elastic elements 4. Degree of muscle stretch

PhysioEx MAP First Screen Select: Exercise 2: Skeletal Muscle Physiology

PhysioEx MAP Next Screen 5 Complete Activities 1-4 and 6;

Exercise 2: Skeletal Muscle Physiology: Activity 1-3: [The Muscle Twitch and Latent Period] We suggest you read the Overview and Introduction and take the Pre-lab Quiz before conducting the Experiment and take the Post-lab Quiz after conducting the Experiment for each of the 5 Activities. You do not need to print out or turn in any of the 5 Pre- and Post-lab quizzes.

Exercise 2: Skeletal Muscle Physiology: Activity 1-3: [The Muscle Twitch and Latent Period] Follow the detailed PhysioEx instructions on pages 7-25 to 7-32 in your manual and record data in the charts in those pages and answer the questions on the pages as you go.

Exercise 2: Skeletal Muscle Physiology: Activity 4: [The Effect of Stimulus Frequency …] Notice the frequency of the stimuli (stimuli/sec) can be adjusted as indicated by the multiple stimuli button

Exercise 2: Skeletal Muscle Physiology: Activity 6: [The Skeletal Muscle Length-Tension Relationship]

PhysioEx Homework to Turn In You will have four tables of data to print from PhysioEx: Activities 2, 3, 4, & 6 to turn in. You will have 9 questions to answer about the PhysioEx Activities on pp. 7-33 & 7-34 in the Lab Manual to turn in.

End Lab 6 Presentation

Antagonists of the Forearm

Antagonists of the Thigh

Antagonists of the Foot