Chapter 4 Flashcards
Muscular strength reflects the primary function of muscle: transformation of
X energy into X energy to generate force, perform work, and
produce movement
chemical
mechanical
In addition, muscle tissues:
- stabilize body position
- regulate X volume
- generate X
- propel fluids and food
matter
- provides protection
organ
heat
Muscular tissue consists of elongated cells called muscle fibers or X that
can use ATP to generate force
myocytes
Based on location and certain structural and functional features, muscular tissue
is classified into three types:
skeletal, cardiac, and smooth
Skeletan muscle tissue:
* It is striated: alternating light and dark protein bands (striations).
* Works mainly in a voluntary manner: activity consciously controlled by somatic nervous
system.
* Others skeletal muscles are controlled subconsciously. E.g. diaphragm while breathing.
ok
Cardiac muscle tissue:
* Located only in the heart wall. Ture/false?
true
Cardiac muscle tissue:
* It is non-striated, and its action is involuntary: natural pacemaker initiates each
contraction (autorhythmicity) and hormones and neurotransmitters adjust heart rate
true/false
false: it is striated
Smooth muscle tissue:
* Located in the walls of hollow internal structures (blood vessels, airways, and most
organs in the abdominopelvic cavity). Also found in the skin, attached to hair follicles.
* Nonstriated.
* Action usually involuntary (true/false?)
true, but some have autorhythmicity
Cardiac muscle and smooth muscle are regulated by autonomic/somatic nervous system and by
hormones released by endocrine glands.
autonomic
FUNCTIONS OF MUSCLE TISSUE
- producing body movements
- stabilizing body positions
- Storing and moving substances within the body. (E.g. Smooth muscle called X
prevent outflow of the contents of a hollow organ) - Generating heat
sphincters
PROPERTIES OF MUSCLE TISSUE
- Electrical excitability
ability to respond to certain stimuli by producing electrical: muscle action potentials. Two types of stimuli trigger them:
X electrical signals arising in the muscular tissue itself: heart’s
pacemaker.
X stimuli: neurotransmitters released by neurons, hormones distributed by
the blood or local changes in pH.
Autorhyhmic
Chemical
PROPERTIES OF MUSCLE TISSUE
- Contractility
- Extensibility
- Elasticity (ability of muscular tissue to return to its original length and shape)
k
ANATOMY OF A SKELETAL MUSCLE FIBER
Skeletal muscle cells or muscle fibers are single contractile muscle cells that form
skeletal muscles.
- Each skeletal muscle fiber arises during embryonic development from the fusion of
myoblasts (mesodermal cells), thus each mature skeletal muscle fiber has a X nuclei. - The plasma membrane of a muscle cell is called X.
- The cytoplasm of a muscle fiber is called Xplasm.
hundred or
more
sarcolemma
sarco
The sarcolemma contains numerous invaginations (pits) called X tubules.
* Transverse tubules (filled with interstitial fluid) tunnel in from the surface toward the
center of each muscle fiber: permits muscle action potentials quickly spreading
throughout the muscle fiber (excites all parts of the muscle fiber at essentially the
same instant).
transverse
Sarcoplasm appears stuffed with little threads (like sausages): X, the contractile organelles of
skeletal muscle.
myofibrils
The endoplasmic reticulum (called X reticulum) encircles each myofibril
sarcoplasmic
The mitochondria lie in circles throughout the muscle fiber, next to proteins that use ATP
during contraction.
true/false
false, in rows (see p.13)
- Dilated end sacs of the sarcoplasmic reticulum (x cisterns) butt against the T
tubule from both sides. - A transverse tubule and the two terminal cisterns on either side of it form a X
terminal
triad.
p.14
In a relaxed muscle fiber, the sarcoplasmic reticulum stores X ions .
Release of X from the terminal cisterns of the sarcoplasmic reticulum triggers
muscle contraction.
calcium(Ca2+)
- Within myofibrils are smaller protein structures: myo…
- Thin filaments are composed of the protein A.
- Thick filaments are composed of the protein B.
- A and B are the contractile proteins that generate force during muscle
contractions.
filaments
A actin
B myosin
There are two X filaments for every Y filament in the regions of filament
overlap.
X thin
Y thick
The filaments inside a myofibril do not extend the entire length of a muscle fiber.
Instead, they are arranged in compartments called X which are the basic
functional units of a myofibril.
sarcomeres
Narrow, plate-shaped regions of dense protein material called A separate one
sarcomere from the next. Thus, a sarcomere extends from one A to the next A
A Z discs
The components of a sarcomere are organized into a variety of bands and zones:
- A band: darker middle part of the sarcomere. It extends the X
- I band: lighter (less dense area). It contains the rest of the X filaments but no
A filaments.
Z disc passes through the center of each I band: narrow, plateshaped regions of dense protein material.
entire length of the
thick filaments.
X thin
A thick
The alternating dark A bands and light I bands create the striations that can be seen in
both myofibrils and in whole skeletal and cardiac muscle fibers.
True/false
true
Within the A band, different areas can be distinguised:
- The center of the A band is the …. zone: contains thick but not thin filaments. At the
middle of the H zone there is the …. line: contains supporting proteins that hold
the thick filaments together. - Each end of the A band is a zone of overlap between thick and thin filaments. Is this zone still part of the sarcomere?
H: hart, is het midden van de A-band met alleen dikke filaments
M: metsellijn, houdt de dikke filaments bij elkaar
* Each end of the A band is a zone of overlap between thick and thin filaments: ook dit deel is nog onderdeel van het sarcomeer
(zie p.20 of daarvoor)
thick or thin filament:
It is made up of 300 myosin molecules
thick
thick or thin filament:
It is mainly made up of actin, although it
also contains troponin and tropomyosin:
regulatory proteins that help turn
contraction on and off
thin
Each myosin molecule has a doubleheaded globular region attached to a
long double-stranded helical chain.
- The myosin tails form the axis of the
thick filament, and the myosin heads
project outward toward the surrounding
thin filaments.
thick or thin filament?
thick
Actin molecules join together to form a
filament coiled into a helix.
* On each actin molecule there is a myosin
binding site.
thick/thin?
thin
During muscle contraction, the muscle shortens but lengths of the thick and thin
filaments do not change.
true/false
true
The thick and thin filaments slide past one another: sliding filament mechanism.
- Muscle contraction occurs because myosin heads attach to and “walk” along the thin
filaments at both ends of a sarcomere, progressively pulling the thin filaments toward
the … line
M
Muscle contraction:
the thin filaments slide inward and meet at the center of a sarcomere. They
may even move so far inward that their ends overlap.
As the thin filaments slide inward, the .. band and .. zone narrow and eventually
disappear altogether when the muscle is maximally contracted.
I (alleen dunne filaments)
H (hart)
However, during contraction, the width of the …. band and the individual lengths of the thick and thin
filaments remain unchanged.
Since the thin filaments on each side of the sarcomere are
attached to …., when the thin filaments slide inward, the ….. come closer
together. Does that make the sarcomere shorter?
A
Z discs
Z discs
Yes the sarcomere shortens
Shortening of the sarcomeres causes shortening of the whole muscle fiber, which in
turn leads to shortening of the entire muscle.
true/false
true
Put in the right order of events:
- The myosin binding sites
located on the actin molecule
are “free” - The sarcoplasmic reticulum
releases Ca2+ into the
sarcoplasm. - Ca2+ binds to troponin
- The contraction
cycle begins: the repeating
sequence of events that causes
the filaments to slide. - The troponin-Ca2+ complex
binds to tropomyosin (which is
blocking the actin-myosin
binding sites), displacing it.
- 3.
- 1.
4.
very important:
A and B permits myosinactin binding (thick and thin
filament attachment, respectively).
A Ca2+
B troponin
The contraction cycle
consists of four steps. Put in right order
- Power stroke
- Detachment of
myosin from actin - ATP hydrolysis
- Attachment of
myosin to actin
- ATP hydrolysis (ATP-> ADP)
- Attachment of
myosin to actin - Power stroke
- Detachment of
myosin from actin (bc of binding ATP)
p.27
Rigor mortis:
after death, cellular
membranes become leaky. Calcium
ions leak out of the … into the sarcoplasm and
allow myosin heads to bind to actin.
ATP synthesis ceases shortly after
breathing stops, however, so the crossbridges cannot detach from actin.
sarcoplasmic
reticulum
ATP permits myosin attachment
from actin (thick and thin
filament).
true/false
false: detachment
A muscle fiber contracts in response to one or more muscle action potentials
propagating along its sarcolemma and through its system of T tubules.
- Muscle action potentials arise at the X junction: the synapse
between a somatic motor neuron and a skeletal muscle fiber. (dus waar de neuron gwn de spier raakt)
neuromuscular
Neural part: the end of the motor neuron (axon terminal) divides into a cluster of
synaptic end bulbs which contain hundreds of synaptic vesicles filled with the
neurotransmitter …..
- Muscular part: motor end plate of the muscle fiber (abundant in junctional folds)
which contain high number of …..
acetylcholine
acetylcholine receptors
