Chapter 39 Sections 1 and 2 ONLY Concept 39.1: The physical interaction of protein filaments is required for muscle function

Muscle Bundle of muscle fibers Nuclei Single muscle fiber (cell) Figure 39.2 Muscle Bundle of muscle fibers Nuclei Single muscle fiber (cell) Plasma membrane Myofibril Z lines Sarcomere Figure 39.2 The structure of skeletal muscle TEM Thick filaments (myosin) M line 0.5 m Thin filaments (actin) Z line Z line Sarcomere 2

Muscle Bundle of muscle fibers Nuclei Single muscle fiber (cell) Figure 39.2a Muscle Bundle of muscle fibers Nuclei Single muscle fiber (cell) Plasma membrane Myofibril Figure 39.2a The structure of skeletal muscle (part 1: muscle fibers) Z lines Sarcomere 3

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energy configuration) 5 2 Figure 39.4 Thin filaments 1 Thick filament Thin filament Myosin head (low energy configuration) ATP 5 ATP 2 Thick filament Myosin- binding sites Thin filament moves toward center of sarcomere. Actin Myosin head (low energy configuration) ADP Myosin head (high energy configuration) P i Figure 39.4 Myosin-actin interactions underlying muscle fiber contraction ADP 3 ADP P i P i Cross-bridge 4 6

Figure 39.3 Sarcomere Relaxed muscle Z M Z Z M Z Contracting muscle 0.5 m Fully contracted muscle Figure 39.3 The sliding-filament model of muscle contraction Contracted sarcomere http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__sarcomere_contraction.html 7

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Synaptic terminal Axon of motor neuron T tubule Sarcoplasmic Figure 39.6a Synaptic terminal Axon of motor neuron T tubule Sarcoplasmic reticulum (SR) Mitochondrion Myofibril Plasma membrane of muscle fiber Figure 39.6a Exploring the regulation of skeletal muscle contraction (part 1: detail of synaptic terminal) Ca2 released from SR Sarcomere 9

Synaptic terminal of motor neuron Plasma membrane Synaptic cleft Figure 39.6b 1 Synaptic terminal of motor neuron Plasma membrane Synaptic cleft T tubule Sarcoplasmic reticulum (SR) 2 ACh Ca2 pump 3 Ca2 ATP 4 CYTOSOL 7 Figure 39.6b Exploring the regulation of skeletal muscle contraction (part 2: steps of process) Ca2 6 5 10

Nervous Control of Muscle Tension Contraction of a whole muscle is GRADED, which means that the extent and strength of its contraction can be VOLUNTARILY altered There are two basic mechanisms by which the nervous system produces graded contractions Varying the number of fibers that contract Varying the rate at which fibers are stimulated 11

Spinal cord Motor unit 1 Motor unit 2 Synaptic terminals Nerve Figure 39.7 Spinal cord Motor unit 1 Motor unit 2 Synaptic terminals Nerve Motor neuron cell body Motor neuron axon Figure 3.7 Motor units in a vertebrate skeletal muscle Muscle Muscle fibers Tendon 12

Tetanus Summation of two twitches Tension Single twitch Time Action Figure 39.8 Tetanus Summation of two twitches Tension Single twitch Figure 39.8 Summation of twitches Time Action potential Pair of action potentials Series of action potentials at high frequency 13

Table 39.1 Table 39.1 Types of skeletal muscle fibers 14

Types of Muscle Fibers Skeletal muscle fibers can be divided on the basis of their contraction speed. Type I - Slow twitch fibers Contract more slowlysustain LONGER contractions OXIDATIVE Type II - Fast twitch fibers Contract more rapidly  sustain SHORTER contractions GYLCOLYTIC or OXIDATIVE

Comparing Cardiac & Smooth Muscles Cardiac Muscle is composed of shorter, branched cells that interconnect with one another at intercalated discs. No neural input needed. Smooth Muscle surrounds walls of hollow internal organs (digestive tract, bladder, etc.). Contractions are slower-can be initiated by the muscles themselves or by neurons of the autonomic nervous system

Concept 39.2: Skeletal systems transform muscle contraction into locomotion Skeletal muscles are attached in ANTAGONISTIC pairs…nervous system coordinates its actions! Purpose of the skeleton? 17

Human forearm (internal skeleton) Grasshopper tibia Figure 39.10 Human forearm (internal skeleton) Grasshopper tibia (external skeleton) Extensor muscle Biceps Flexion Flexor muscle Triceps Biceps Extensor muscle Figure 39.10 The interaction of muscles and skeletons in movement Extension Flexor muscle Triceps Key Contracting muscle Relaxing muscle 18

Types of Skeletal Systems The three main types of skeletons are __________________ skeletons (lack hard parts) __________________ (external hard parts) __________________ (internal hard parts) 19

Longitudinal muscle relaxed (extended) Circular muscle contracted Figure 39.11 Longitudinal muscle relaxed (extended) Circular muscle contracted Circular muscle relaxed Longitudinal muscle contracted Bristles Head end 1 Head end Figure 39.11 Crawling by peristalsis 2 Head end 3 20

Types of joints Skull Ball-and-socket Clavicle joint Shoulder girdle Figure 39.12 Types of joints Skull Clavicle Ball-and-socket joint Shoulder girdle Scapula Sternum Rib Humerus Hinge joint Vertebra Pivot joint Radius Ulna Pelvic girdle Carpals Phalanges Metacarpals Figure 39.12 Bones and joints of the human skeleton Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges 21

Ball-and-socket joint Head of humerus Figure 39.13 Ball-and-socket joint Head of humerus Scapula Hinge joint Humerus Ulna Figure 39.13 Types of joints Pivot joint Ulna Radius 22

Types of Locomotion Most animals are capable of locomotion, or active travel from place to place In locomotion, energy is expended to overcome friction and gravity Flying Locomotion on Land Swimming 23