Cardiac and Smooth Muscle (Nursing)

by Jasmine Clark, PhD

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    00:01 So now let's switch gears again and discuss different types of muscles.

    00:06 So we spent a lot of time discussing the skeletal muscles, but recall there are two other muscle tissues in the body.

    00:14 The first one we'll discuss is the cardiac muscles.

    00:18 So the cardiac muscles are very similar to the skeletal muscles and that they are both striated.

    00:25 However, there are some key differences between the two.

    00:29 First, this cardiac muscles have only one nucleus, whereas, the skeletal muscle fibers can often have several nuclei per fiber.

    00:40 Also, cardiac muscle cells contain structures known as intercalated discs.

    00:46 Intercalated discs are where the two cardiac muscles are going to join.

    00:51 They are joined together by desmosome and gap junctions.

    00:56 Recall we learned about these different types of cell junctions in a previous lecture.

    01:01 These allow the muscle action potentials to spread from one muscle fiber to another.

    01:09 So speaking of gap junctions.

    01:11 The gap junctions are very interesting as they allow the heart cells to actually function as a syncytium.

    01:19 In other words, the heart is going to act like one big cell, even though it is made up of thousands of cells.

    01:29 So an interesting fact about cardiac muscle cells is that they actually have more mitochondria and their contractions last 10 to 15 times longer than that of the skeletal muscle contraction.

    01:44 So the next type of muscle tissue in the body is the smooth muscle tissue.

    01:49 Smooth muscles often line most of our visceral organs.

    01:54 Smooth muscles look very different than that of the cardiac and the skeletal muscles.

    02:01 They are shaped different, whereas thick in the middle and tapered toward the ends.

    02:06 And also, unlike skeletal muscles and cardiac muscles, smooth muscles do not contain striations.

    02:15 Also, smooth muscles can be arranged as single-units or can act as multi-unit fibers.

    02:23 Smooth muscle contractions start more slowly, but last longer than that of skeletal and cardiac muscle contractions.

    02:33 The contractile proteins found in smooth muscles are also not organized into sarcomeres like they are in skeletal and cardiac muscles.

    02:44 In these type of muscles because of the arrangement of the contractile proteins, when smooth muscles contract, they contract and a corkscrew motion instead of a shortening motion.

    02:59 Also in smooth muscles, they use different regulatory proteins.

    03:04 Whereas, in the skeletal muscles and the cardiac muscles, we're going to use troponin and tropomyosin.

    03:11 In smooth muscles, the regulatory proteins include calmodulin and myosin light chain kinase.

    03:19 Also, smooth muscles can shorten and stretch to a much greater degree than that of skeletal and cardiac muscles.

    03:28 And finally, smooth muscle fibers shorten in response to stretch.

    About the Lecture

    The lecture Cardiac and Smooth Muscle (Nursing) by Jasmine Clark, PhD is from the course Musculoskeletal System – Physiology (Nursing).

    Included Quiz Questions

    1. Cardiac muscle contains more mitochondria than skeletal muscle.
    2. The contraction of cardiac muscle lasts 10–15 times longer than that of skeletal muscle.
    3. Cardiac muscle contains intercalated discs; skeletal muscle does not.
    4. Cardiac muscle fiber contains many nuclei, whereas skeletal muscle fiber may contain only one nucleus.
    5. Cardiac muscle contains striations; skeletal muscle does not.
    1. Smooth muscle
    2. Skeletal muscle
    3. Cardiac muscle
    4. Involuntary muscle

    Author of lecture Cardiac and Smooth Muscle (Nursing)

     Jasmine Clark, PhD

    Jasmine Clark, PhD

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