Chapter 12 Flashcards
The human body has three types of muscle tissue:
skeletal
muscle, cardiac muscle, and smooth muscle
skeletal
Most skeletal
muscles are attached to the bones of the skeleton, enabling
these muscles to control body movement
cardiac
Cardiac muscle
{kardia, heart} is found only in the heart and moves blood
through the circulatory system
which muscles are classified as striated and why
Skeletal and cardiac muscles
are classified as striated muscles {stria, groove} because of their alternating light and dark bands seen under the light
microscope
soothie muscle
Smooth muscle is the primary muscle of internal organs
and tubes, such as the stomach, urinary bladder, and blood vessels. Its primary function is to influence the movement of material into, out of, and within the body
skeletal muscle fibers
s are large,
multinucleate cells that appear
striped or striated under the
microscope.
cardiac muscle fibers
are also striated but they are smaller, branched, and uninucleate. Cells are joined in series by junctions called intercalated disks.
smooth muscle fibers
are small
and lack striations
why isnt smooth muscle striated
Its lack of banding results from
the less organized arrangement of contractile fibers within the
muscle cell
Skeletal muscles are unique in that they contract only in
response to a
a signal from a somatic motor neuron. They cannot
initiate their own contraction, and their contraction is not influenced directly by hormones.
In contrast, cardiac and smooth muscle have multiple levels
of control. T- explain
Their primary extrinsic control arises through autonomic innervation, but some types of smooth and cardiac muscle
can contract spontaneously, without signals from the central nervous system. In addition, the activity of cardiac and some smooth
muscle is subject to modulation by the endocrine system. Despite
these differences, smooth and cardiac muscle share many properties with skeletal muscle
how are skeletal muscles usually attached to bones, what is an origin and an insertion of a muscle
Skeletal muscles are usually
attached to bones by tendons made of collagen [p. 80]. The
origin of a muscle is the end of the muscle that is attached closest to the trunk or to the more stationary bone. The insertion
of the muscle is the more distal {distantia, distant} or more mobile
attachment
flexor
The
muscle is called a flexor if the centers of the connected bones
are brought closer together when the muscle contracts, and the
movement is called flexion
extensor
The muscle is called an extensor if
the bones move away from each other when the muscle contracts,
and the movement is called extension
A skeletal muscle is a collection of muscle cells, or
muscle fibers, just as a nerve is a
collection of neurons
what does a skeletal muscle fiber look like
Each skeletal muscle fiber is a long, cylindrical cell with up to several hundred nuclei near the surface of the fiber. they are the largest cells in the body, created by the fusion of many individual embryonic muscle cells
myofibril
The main
intracellular structures in striated muscles are myofibrils {myo-,
muscle}, highly organized bundles of contractile and elastic proteins that carry out the work of contraction
what is the Sr wrapped around
each myofibril
terminal cisternae
The sarcoplasmic reticulum consists of longitudinal tubules with
enlarged end regions called the terminal cisternae
t-tubules
The terminal cisternae are adjacent to and closely associated
with a branching network of transverse tubules, also known as
t-tubules (FIG. 12.4). One t-tubule and its two flanking terminal
cisternae are called a triad. The membranes of t-tubules are a continuation of the muscle fiber membrane, which makes the lumen
of t-tubules continuous with the extracellular fluid