| Question | Answer |
| Muscle Cells | Muscle Fibers |
| M -Line | A dark band that anchors the myosin myofilaments in the center of the sarcomere |
| H- zone | - Light area in the center of sacomere
- consists of only myosin |
| A-band | -extends the length of the myosin
-darker central region in each sarcomere |
| I-band | -each side of Z-line
- consists of actin |
| The arrangement of actin and myosin give a _______ appearance. | banded |
| basic structural and functional unit of the muscle | sarcomeres |
| sarcomeres | joined end to end to form the myofibril.
(Z-line to Z-line) |
| myosin myofilaments | thick myofilaments |
| actin myofilaments | thin myofilaments |
| myofilaments consist of 2 major kinds of protein fibers | -actin myofilaments
- myosin myofilaments |
| minute | small |
| four major functional characteristics | -contractility
-excitability
-extensibility
-elasticity |
| contractility | the ability of skeletal muscle to shorten with force |
| excitability | the capacity of skeletal muscle to respond to stimulus |
| extensibility | the ability to be stretched |
| elasticity | the ability to recoil to their original resting length after they have been stretched |
| epi | upon |
| epimysium | connective tissue that wraps the entire muscle |
| fascia | another connective tissue located outside the epimysium. It surrounds and separates muscles. |
| fasciculi (fascicle) | bundles of muscle |
| perimysium | surrounds the fascicle |
| muscle fibers (fibers) | single muscle cell |
| endomysium | surrounds muscle fibers |
| myofibrils | a thread-like structure that extends from one end of the fiber to the other |
| motor unit | a single motor neuron and all skeletal muscle fibers it innervates |
| presynaptic terminal | enlarged nerve terminal |
| synaptic cleft | the presynaptic terminal and the muscle cell |
| postsynaptic terminal | muscle fiber |
| synaptic vesicles | secretes neurotransmitter called acetylcholine |
| acetylcholine | a neurotransmitter |
| acetylcholinesterase | enzymes that rapidly break down neuron and muscle cells |
| sliding filament mechanism | the sliding of actin myfilaments past myosin myofilaments during contraction |
| muscle twitch | a contraction of an entire muscle in response to a stimulus |
| threshold | the point where muscle fibers contract maximally |
| all-or-none response | when threshold is reached |
| lag phase | time between application of a stimulus to a motor neuron and the beginning of a contraction |
| contraction phase | time of contraction |
| relaxation phase | the tie during which the muscle relaxes |
| tetany | the muscle remains contracted without relaxing |
| recruitment | the increase in number of motor units being activated |
| ATP | -needed for energy for muscle contraction
-produced in mitochondria
-short-lived and unstable |
| creatine phosphate | another high-energy molecule |
| anaerobic respiration | without oxygen |
| aerobic respiration | with oxygen (more efficient) |
| oxygen debt | the amount of oxygen needed in chemical reactions to convert lactic acid to glucose |
| muscle fatigue | results when ATP is used during muscle contraction faster than it can be produced in the muscle cells |
| 2 types of muscle contractions | - isometric
-isotonic |
| isometric | the length of the muscle doesn't change, but the amount of tension increases during the contraction process |
| isotonic | the amount of tension produced by the muscle is constant during contraction, but the length of the muscle changes |
| muscle tone | constant tension produced by the muscle is constant during contraction |
| fast-twitch fibers | contract quickly and fatigue quickly |
| slow-twitch fibers | contract more slowly and are more resistant to fatigue |
| the points of attachment of each muscle are its _____ and ______ | - origin
- insertion |
| origin (head) | the most stationary end of the muscle |
| insertion | the end of the muscle undergoing the greatest movement |
| neuromuscular junction | - each branch that connects to the muscle
- near the center of the cell |
| platysma | a sheet-like muscle that covers the anterolateral neck |
| sternocleidomastoid | lateral neck muscle and prime mover |
| extrinsic tongue muscles | move the tongue |
| intrinsic tongue muscle | change of shape of the tongue |
| 4 pairs of mastication | 2 pairs of pterygoids, temporalis, and masseter |
| mastication | chewing |
| depressor anguli oris | frowning |
| levator labii superioris | sneering |
| zygomaticus | smiling muscle |
| buccinator | flattens the cheeks |
| orbicularis oris | puckers the lip |
| orbicularis oculi | closes the eyelids and causes wrinkles to form |
| occipitofrontalis | raises the eyebrow |
| prime mover | one muscle playsa major role in accomplishing the desired movement |
| belly | the portion of the muscle between the origin and the insertion |
| synergists | muscles that work together to accomplish specific movements |
| antagonists | muscles that work in opposition to one another |
| muscles are named according to their ____, ____, ____, ____, ____, ____, and ____ | - location
-size
- orientation of fibers
- shape
- origin
- insertion
- function |
| motor neurons | nerve cells that carry action potentials to skeletal muscle fibers |
| action potential | the brief reversal back of the charge |
| resting membrane potential | the charge difference across the membrane |
