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Actin and myosin myofilaments form highly ordered units called ____________, which are joined end to end to form the myofibril.
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Nerve cells that carry action potentials to skeletal muscle fibers.
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Anatomy
| Question | Answer |
|---|---|
| Actin and myosin myofilaments form highly ordered units called ____________, which are joined end to end to form the myofibril. | sarcomeres |
| Nerve cells that carry action potentials to skeletal muscle fibers. | Motor neurons |
| ________ ________ occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten. When the sarcomeres shorten it causes the muscle to shorten | Muscle Contraction |
| the ability of skeletal muscle to shorten with force | Contractibility |
| the capacity of skeletal muscle to respond to a stimulus | Excitability |
| ability to be stretched | Extensibility |
| ability to recoil to their original resting length after they have been stretched | elasticity |
| Muscles help to produce heat essential for maintenance of normal _____________ | body temperature |
| Each skeletal muscle is surrounded by a connective tissue sheath called the | epimysium |
| another connective tissue located outside the epimysium. It surrounds and separates muscles | Fascia |
| A muscle is composed of numerous visible bundles called muscle fasciculi (fascicle), which are surrounded by loose connective tissue called the | perimysium |
| The fasciculi are composed of single muscle cells called | fibers. |
| Each fiber is surrounded by a connective tissue sheath called the | endomysium |
| The cytoplasm of each fiber is filled with ________- a threadlike structure that extends from one end of the fiber to the other | myofibrils |
| thin myofilaments. They resemble 2 minute strands of pearls twisted together | actin myofilaments |
| On each side of the Z line is a light area called an _ _____, it consists of actin. | I band |
| The myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called the _ _____. | M line |
| When a muscle cell is stimulated the membrane characteristics change briefly. The brief reversal back of the charge is called ____________. | action potential |
| Axons enter the muscles and branch. Each branch that connects to the muscle forms a _________ or __________ near the center of the cell. | neuromuscular junction, or synapse |
| The enlarged nerve terminal is the ________ _________. | presynaptic terminal |
| The space between the presynaptic terminal and the muscle cell is the __________ _________ | synaptic cleft |
| The muscle fiber is the ________ ________ | postsynaptic terminal |
| Synaptic vesicles secretes a neurotransmitter called ___________. It diffuses across the synaptic cleft and binds to the postsynaptic terminal causing a change in the postsynaptic cell. | acetylcholine |
| The sliding of actin myofilaments past myosin myofilaments during contraction is called ______ _______ ______ _______ of muscle contraction. The H and I bands shorten, but the A bands do not change in length | the sliding filament mechanism |
| The time between application of a stimulus to a motor neuron and the beginning of a contraction is the ____ _______ | lag phase |
| Where the muscle remains contracted without relaxing | Tetany |
| Each muscle fiber is a single cylindrical cell containing | several nuclei |
| Myofibrils consist of 2 major kinds of protein fibers: | actin myofilaments and myosin myofilaments |
| thick myofilaments. They resemble bundles of minute golf clubs. | myosin myofilaments |
| The ______________ is the basic structural and functional unit of the muscle. | sarcomere |
| Each sarcomere extends from one _______ (disc) to another ______ (disc). Each ______ is an attachment site for actin. | Z line |
| The arrangement of ______ and ______ give a banded appearance | actin and myosin |
| The _ _____ extends the length of the myosin. It is the darker central region in each sarcomere. | A band |
| In the center of each sarcomere is another light area called the _ _____, which consists of only myosin. | H zone |
| The outside of most cell membranes is positively charged compared to the inside of the cell membrane, which is negatively charged. The charge difference across the membrane is called the _____________. | resting membrane potential |
| A single motor neuron and all the skeletal muscle fibers it innervates are called a ______ ______. Many motor units form a single muscle. | motor unit |
| A __________ __________ is formed by an enlarged nerve terminal resting in an indentation of the muscle cell membrane | neuromuscular junction |
| Each presynaptic terminal contains _______ _________ | synaptic vesicles |
| A contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle fibers. | Muscle twitch |
| A muscle fiber will not respond to stimulus until that stimulus reaches a level called _________, at which point the muscle fiber will contract maximally. This phenomenon is called the ___-__-____ _______. | threshold, all-or-none response |
| The time of contraction is the ________ ________ | contraction phase |
| The time during which the muscle relaxes is the ________ _______ | relaxation phase |
| If _________ ________ are given you get successive twitches that occur so frequently the muscle doesn't have time to fully relax | successive stimuli |
| The increase in number of motor units being activated is called _____________ | recruitment |
| Occipitofrontalis | raises the eyebrows |
| orbicularis oculi | closes the eyelids and causes crows feet |
| orbicularis oris | puckers the lips |
| buccinator | flattens the cheeks. trumpeter's muscle |
| Zygomaticus | smiling muscle |
| levator labii superioris | sneering |
| depressor anguli oris | frowning |
| Mastication | chewing |
| Intrinsic Tongue muscles | change the shape of the tongue |
| extrinsic tongue muscles | move the tongue |
| Sternocleidomastoid | lateral neck muscle and prime mover. Rotates and abducts the head |
| Erector spinae | group of muscles on each side of the back. Responsible for keeping the back straight and the body erect |
| External intercostals | elevate the ribs during inspiration |
| Internal intercostals | contract during forced expiration. |
| Trapezius | rotates scapula |
| Serratus anterior | pulls scapula anteriorly |
| The arm is attached to the thorax by the | pectoralis major and latissimus dorsi muscles |
| Pectoralis major | adducts and flexes the arm |
| Latissimus dorsi | medially rotates, adducts, and powerfully extends the arm. “Swimmer muscles” |
| Deltoid | attaches the humerus to the scapula and clavicle, and is the major abductor of the upper limb. |
| Biceps brachii | flexes the forearm. Occupies the anterior compartment of the arm |
| Brachialis | flexes forearm |
| Brachioradialis | flexes and supinates the forearm. |
| Retinaculum (bracelet) | strong band of fibrous connective tissue that covers the flexor and extensor tendons and holds them in place around the wrist so that they do not “bowstring” during muscle contraction. |
| Flexor carpi | flexes the wrist |
| Extensor carpi | extends the wrist |
| Flexor digitorum | flexes the fingers |
| Extensor digitorum | extends the fingers |
| Gluteus maximus | buttocks. Contributes most of the mass of the buttocks. Gluteus medius, hip muscle and common injection site. |
| Quadriceps femoris | extends the leg; anterior thigh muscles |
| Sartorius | “tailors muscle”; flexes the thigh |
Created by:
JaKPak