1. (17)
Muscle physiology is the study of muscle function. A
muscle is a bundle of fibers that contract to
produce heat, posture, and motion, either of internal
organs or of the organism itself. Muscle physiology
studies the physical, mechanical, and biochemical
aspects of muscles in development, fiber structure,
muscle structure, contraction, and strength-
building. (1)
2. (17)
How do skeletal muscles provide
movement, heat, and posture.
Are all of these functions unique
to muscles?
Since skeletal muscles are attached to the
bones of the body and they are under
voluntary control. The provide movement of
the joints by contracting, also they prevent
from unwanted movement. To cause the
skeletal muscles to contract, impulses are
transmitted by a nerve signal, called a motor
neuron, which sends the impulse throughout
multiple muscle cells to contract that muscle
to produce movement.
The chemical reactions that cause muscle
contraction generate heat - energy
conversion always generates "useless"
energy; entropy increases (2)
3. The characteristics are shared with the nervous
system. The muscle impulse reaches the
sarcoplasmic reticulum, which releases calcium
ions into the sarcoplasm of the muscle
fiber;Calcium binds to troponin, moving
tropomyosin and exposing myosin binding sites on
actin filament; Cross-bridges (linkages) form
between actin and myosin; Actin filaments are
pulled inward by myosin cross-bridges;The muscle
fiber shortens as contraction occurs. (4)
4. Muscle contractions occur every time we
move. The muscle must contract in order More muscle
to move the bone that it is attached to
or to provide resistance against a force.
Isometric contractions occur when the
info!
muscle contracts but there is no
movement. Muscle contractions which (17)
result in movement are known as
isotonic contractions. There are two
types of isotonic muscle contraction
Concentric and Eccentric. Concentric
muscle contractions are the most
common form of contraction. These occur
when the muscle shortens in length in
order to make the bone move. These
contractions occur when the body is
working against gravity. Eccentric
contractions are the opposite of
concentric contractions. The muscle
contracts but increases in length. This
type of contraction occurs usually in the
direction of gravity, to control a
movement. (5)
5. (17)
3)Explain how the structure of the
myofilaments is related to their
function.
Myofilament is a term that the chains of (primarily) actin and myosin that pack a
muscle fiber. These are the force generating structures. Although there are still
gaps in what we know of the structure and functional significance of the
myofilament lattice, some of the key proteins includes myosin, actin, troponin,
titin, and nebulin. a myofilament shows several distict bands, each of which has
been given a special letter. The lightest (least electron dense) band is known as the
I band and consists mostly of actin. The wide, dark band, known as the A band, is
composed primarily of myosin. In the center of the I band is an electron dense line,
known as the Z-line. In the middle of the A band is another dense line known as
the M line. (6)
6. (17)
In cross section, under very high magnification, both A
and I bands can be seen to be hexagonal networks.
These networks are apparently ordered and fixed at the
M- and Z-lines. In the region where the A and I bands
overlap (sometimes known as the H band) the two
hexagonal networks intermesh so that each myosin
filament is surrounded by six actin filaments. These
networks appear to be anchored to (and through) the
cell membrane in two ways. At the ends of fibrils, special
structures anchor the terminal actin filaments to the
membrane. There also appear to be connections
between the Z and M lines and the cell membrane. (7)
8. (17)
5)Explain how the sliding filament theory
allows for the shortening of a muscle fiber.
Sliding filament theory in its simplest
form states that muscle fibers shorten
when actin filaments slide inward on
myosin filaments - pulling the z-lines
closer together. Actin filaments (the
light bands in the diagram above) slide
over myosin filaments (the dark bands)
the H-zone and I-band decrease.
Myosin filaments contain tiny globular
heads, called cross bridges at regular
intervals. These cross bridges attach to
the actin filaments pulling on them to
create movement. Each flexion of a
cross bridge produces only a very
small movement in the actin filament
so many cross bridges throughout the
muscle must flex repeatedly and
rapidly for any measurable movement
to occur. (9)
9. (17)
6. Compare and contrast the role of Ca++ in
excitation, contraction, and relaxation of a
muscle cell.
An action potential in the muscle cell is what
triggers muscle cell contraction. We have seen
that calcium ions regulate whether or not
contraction can occur. The action of Ca++ and
is generated by for removal and the relaxation
is taken up in 24th plate. A muscle contraction
in response to a single nerve action potential is
called a twitch contraction. A myogram, a
graph of muscle strength (tension) with time.
The latent period is the time required for the
release of Ca2+. The contraction period
represents the time during actual muscle
contraction. The relaxation period is the time
during which Ca2+ are returned to the
sarcoplasmic reticulum by active transport.
10. 10) explain the meaning of unit of
combined cells
Cardiac muscle combines as a syncytium, which is a
unit of combined cells. They are self exciting which
means they don’t need nerve impulses to contract.
(12)
(17)
12. (17)
11)What is rigor mortis
Atp binds to the myosin heads releasing it from actin
and making the muscle pliable. If no atp is available,
myosin heads remain stuck to actin and the muscle
becomes stiff. This is the rigidity of rigor mortis
following death. (13)
13. (17) 12)What are the 4 factors
that influence the
strength of muscle
contractions?
1. The number of muscle
fibers stimulated
2. The relative size of the
fibers
3. Frequency of
stimulation
4. The degree of muscle
strength(14)
13)What are the phases of a twitch contraction? What molecular events occur during each of
these phases.
muscle contraction in response to a single nerve action potential is called a twitch
contraction.
1.The latent period is the time required for the release of Ca2+.
2.The contraction period represents the time during actual muscle contraction.
(14)
14. (17)
3. The relaxation period is the time during
which Ca2+ are returned to the sarcoplasmic
reticulum by active transport.
4. The refractory period is the time
immediately following a stimulus. This is the
time period when a muscle is contracting and
therefore will not respond to a second
stimulus. Since this is occurring at the same
time as the contraction, it does not appear on
the myogram as a separate event. (15)
15. (17)
14)How does the treppe effect relate to the
warm-up exercises of athletes?
The concept or phenomenon of "Treppe"
occurs when a muscle contracts more
forcefully after it has contracted a few times
than when it first contracts. This is due to
the fact that active muscles require
Muscles of the
decreasing degrees of succeeding stimuli to
face include:
elicit maximal contractions. Returning to
deppresor,
our example of the second set of squats
temporalis,
feeling easier than the first, during the first
set there was insufficient warm-up, and the
and levators
second set felt easier because the first set
actually served as a warm-up. The
phenomenon in which the contraction
strength of a muscle increases, due to
increased Ca2+ availability and enzyme
efficiency during the warm-up. (15)
