HIST: Muscle tissue 1 (3)

List the three skeletal muscle characteristics.

1. Skeletal muscle fibers have numerous cross striations. 2. These muscles are voluntary. 3. Skeletal muscles are quick, but usually get tired fast.

Microstructure of a myofibril Each myofibril exhibits striations formed by alternating dark (___-bands) and light (___-bands) regions.

A I

Terminal cisternae are running near the boundary of _______.

A-band and I-band

General characteristics of skeletal muscle fibers. 5. Sarcoplasmic reticulum is a highly specialized form of smooth endoplasmic reticulum and is used as a depot of _____. When excited, the sarcoplasmic reticulum ______ into _______ initiating the _________.

Ca++ releases Ca++ cytoplasm muscular contraction

Terminal cisternae contain high concentration of ________.

Ca++ ions

Skeletal muscle: relaxation. 1. Following the depolarization, ________ transport Ca++ back into the sarcoplasmic reticulum. Ca++ disassociates from the ________. 2. As a result the troponin complex returns to its original configuration and pulls the _______ over the myosin binding site blocking the _______ interaction. This stops the ________ unless there are new waves of ______ coming with the nerve impulses. 3. This is a rapid action that only takes ______

Ca++-activated ATPase membrane pumps troponin C tropomyosin filament actin-myosin contraction depolarization 30 msec

Name the three proteins that thin filaments are composed of.

F-actin Tropomyosin Troponin

What holds the thick filaments in register at the M-line?

Myomesin

What are the three major types of muscle tissue?

Skeletal muscle Smooth muscle Cardiac muscle

Terminal cisternae run parallel to the _____ on both sides of it, forming _____.

T-tubules triads

What are the major types of accessory proteins found in the skeletal muscle?

Titin Myomesin Alpha actin

Thick filaments are formed by hundreds of myosin molecules. Myosin II molecules consist of: a. _____ heavy chains that form _____ and two _____ that exhibit ____ and _____ activity. The globular heads contain binding sites for _____. b. ________ attach to the heads.

Two coiled α-helices globular heads ATPase motor actin and ATP Two pairs of light chains

Accessory proteins are found primarily in the ____ and in the ____. They provide attachment of filaments to the ____ and attachment of Z-disks to ____ and to the ______.

Z-disk M-line Z-disk each other sarcolemma

Nebulin is a protein that is attached to the ______ and runs parallel to ______ filaments. It helps to anchor the ______ and to regulate the _______ of thin filaments during _____.

Z-disk thin thin filaments length muscular fiber development

Microstructure of a myofibril 3. Z-disk (or Z-line) is composed of ______ and its major function is to provide _______ for _____ filaments and to support the architecture of the _____.

accessory proteins anchoring points thin myofibril

Microstructure of a myofibril 1. Most of A-band contains ________ filaments. Its central part is called the ______. a. H-zone is a ____ area in the middle of the A-band that contains _____ filaments. i. _____ is a line formed by accessory proteins, such as ______ that hold the thick filaments in _____.

both thick and thin H-zone pale thick M-line myomesin register

As the action potential travels along the membrane, it descends down into the ____ along the _____, which causes excitation of the ____ and release of ____ into ______.

cell T-tubules SR Ca++ sarcoplasm

What are the two most important characteristics of the muscle tissue?

contractility and conductivity

Thin filaments a. F-Actin that forms _________.

double-stranded helical filament

Electrophysiology of the muscle. 1. Sarcolemma is an _______. The voltage inside the cell is _____, while it is _____ outside the cell, so there is a ________ in the resting cell, which is achieved by actively pumping _____ ions out of the cell.

electric capacitor negative zero negative membrane potential Na+

Organization of skeletal muscles. 1. Named skeletal muscles (e.g. the biceps) consist of ______ or bundles of _______ surrounded by a ______. 2. Fascicles are formed by groups of ______. 3. Each skeletal muscle fiber is a ______ or ______.

fascicles skeletal muscle fibers connective tissue sheath skeletal muscle fibers multinucleated cell syncytium

Thin filaments b. Tropomyosin forms ______ that lie in the grooves between the ______. In the resting muscle tropomyosin masks the ________ on the _______.

filaments two actin monomers myosin-binding sites actin filament

General characteristics of skeletal muscle fibers. Where are nuclei of skeletal muscle found and where are they located?

found immediately beneath the sarcolemma peripheral in location

Where do skeletal muscle fibers originate?

from myoblasts that fuse with each other to form long multinucleated postmitotic myotubes.

Cardiac muscle fibers are found in the _____ and are _______. Cardiac muscle is ______.

heart striated involuntary

Microstructure of a muscular fiber. Muscular fibers are composed of _____ of myofibrils that span the ______ length of the muscle cell. Myofibrils are composed of thin filaments and thick filaments. Within the myofibril the thin (or actin) filaments are arranged in a ________ array with _______ surrounding ______.

hundreds entire hexagonal 6 thin filaments 1 thick (myosin) filament

Desmin is an _______ filament that forms a ______ that surrounds ______ and attaches them to one another and also attaches Z-disks to the ________.

intermediate lattice Z-disks plasma membrane

What is the function of titin?

keep the thick filaments in their position in the central part of the sarcomere.

General characteristics of skeletal muscle fibers. What does the sarcolemma form? Where do the t-tubules extend and what are they important for?

long processes called T-tubules extend into the cytoplasm and are important for carrying the wave of depolarization deep into the sarcoplasm

Dystrophin is a ______ that links _______ to the _______ stabilizing the _____ filaments.

membrane-associated protein complex actin cytoskeleton extracellular matrix thin

General characteristics of skeletal muscle fibers. 1. Each of the "cells" of the skeletal muscle is actually a __________ that forms a _________.

multinucleated syncytium skeletal muscle fiber

Organization of skeletal muscles. 4. Each skeletal muscle fiber is formed by many _______ that extend the whole length of the muscle fiber. What are the two principal components of the myofibril?

myofibrils thick and thin filaments

General characteristics of skeletal muscle fibers. 4. Sarcoplasm of skeletal muscle cells contains: a. Numerous ________. The arrangement of contractile filaments within the myofibrils is ______ and gives the myofibril ________ appearance. All the myofibrils are in register within the skeletal muscle fiber, so the ______ fiber exhibits characteristic _______. b. Numerous ____________ lie between myofibrils and close to the sarcolemma. They represent the source of ____ for the myofibrils. c. _______, an oxygen-binding protein, is present in skeletal muscle cells.

myofibrils regular "striated" whole transverse striations filamentous mitochondria ATP Myoglobin

What does each triad consist of?

one Ttubule two cisternae of sarcoplasmic reticulum running parallel to it

Microstructure of a myofibril 2. I-band is a _____ area formed primarily by ____ filaments. Such proteins as _______ are also found in the I-band. It is bisected by the ______.

pale thin titin and nebulin Z-line (or Z-disk)

Electrophysiology of the muscle. 3. Action potentials are brief ______ going changes in the membrane potential that are propagated along the length of the ______ at speed up to ________.

positive membrane 120 m/sec

Electrophysiology of the muscle. 2. The depolarized membrane develops a ______ when it becomes more permeable for Na+ ions. The depolarization of the membrane of the muscle cell starts a cascade of reactions that cause ___________.

positive membrane potential muscular contraction

What is the contractility in muscles due to?

presence of actin and myosin and ATP

T-tubular system (transverse tubule system) is formed by deep invaginations of the _______. T-tubules allow for the ______ to travel down into the cell and excite the ______.

sarcolemma impulse terminal cisternae of the sarcoplasmic reticulum

When referring to the specialized plasmalemma of muscle cells the term ________ is used. The cytoplasm of muscle cells is referred to as ________. The specialized smooth endoplasmic reticulum of muscle cells is called ____________

sarcolemma sarcoplasm sarcoplasmic reticulum

What are membrane triads formed by?

sarcoplasmic reticulum sarcolemma

Regeneration of skeletal muscle is due to the presence of _____, scattered between the skeletal muscle fibers. After injury satellite cells become _______,_______ and give rise to new _______, which fuse to form a new fiber. Extensive damage results in the formation of a _____. Muscles respond to aging by increasing the _____, to exercise by ______, and to disuse by _____

satellite cells activated, proliferate myoblasts connective tissue scar diameter hypertrophy atrophy

Skeletal muscle fibers are attached to the ______ and are also present in some ______. Skeletal muscles are _______. They exhibit distinctive striations that are due to the arrangement of _______ in the ______. 1. Skeletal muscles are attached to bones and used primarily for _______, ________, and other functions. 2. Visceral muscles are present in the ___________, and aid with _____________.

skeleton visceral organs voluntary filaments cytoplasm locomotion respiration tongue, pharynx, and in the upper part of esophagus swallowing and speech

Sarcoplasmic reticulum forms long chambers, called ________.

terminal cisternae

Skeletal muscle: contraction In the resting muscle cell the myosinbinding site on the actin filament is concealed by what? In the presence of high concentration of Ca++ ions, Ca++ binds to ______. This changes the _____ of the troponin molecule and causes the _______ to shift, which opens up _____ site on the actin filament. Myosin starts ______ along the actin fibers. Myosin uses _____ to slide the actin along, so myosin is an ____.

the tropomyosin filament troponin C spatial configuration tropomyosin filament myosin-binding "walking" ATP energy ATPase

Titin is a large protein that anchors the ______ to Z-disks. It extends to the ______.

thick filaments M-line

What does the conductivity allows muscle cells to do?

transmit electrical impulse to other cells and to receive impulses from nerve cells

Thin filaments c. Troponin complex is attached to _____ and includes _____ globular subunits. i. Troponin T binds to ______, anchoring the troponin complex. ii. Troponin I binds to _____ inhibiting the interaction with _____. iii. Troponin C is the ______ subunit; it binds to _____, which is an essential step in the initiation of the ______.

tropomyosin three tropomyosin actin myosin smallest Ca++ muscular contraction

Microstructure of a myofibril 4. Sarcomere is a portion of a myofibril between ______. It is the _______ of skeletal muscle. It measures _____ in relaxed muscle. The sarcomeres of individual myofibrils are in register in ______, so the entire muscle cell exhibits _____. Skeletal muscle contraction is due to the _____ which results in the ______ of the sarcomere, while the length of individual filaments ______. The length of the _____ does not change during contraction, but the ______ shrink during contraction due to the increase of overlap between thick and thin filaments.

two adjacent Z-disks basic contractile unit 2-3 µm one muscle fiber cross-striations sliding of filament shortening does not change A-band I-band and H-zone

Smooth muscle fibers are primarily found in the _______. They do not show ________ in the cytoplasm. These are _______.

walls of internal organs striations involuntary

What anchors the thin filaments into the Z-disk?

α-Actinin