hello all this is dr alsup and this is the first video in our skeletal muscle tissue
series so we've talked about uh bone tissue some we've talked about the basics of joints and now
let's finish off the musculoskeletal system before we get into the actual
structures with skeletal muscle tissue so we're going to start with the discussion of
the properties and functions of all muscular tissue and while the focus of this particular
series will be skeletal muscle as that plays the biggest role in the musculoskeletal system
throughout this course you will be learning about the other main types of muscle which
include cardiac and smooth muscle but since i have the honor of being the first lecturer
in this course i get to introduce some of the overarching concepts for all muscles
so that's what i'll be describing here properties and functions of all types of muscular tissue
muscle will have four properties that allow it to fulfill the functions we will discuss later in
this video and this first one is pretty darn cool if you ask me and that is electrical excitability
and yes i said electrical this is the ability to respond so the muscle's ability to respond
to certain stimuli by producing electrical signals all right and in the case of muscle
these are called muscle action potentials often you will see action potentials abbreviated with ap
electrical ex excitability is actually a property that muscle shares with nerve cells so there is a
property shared with the nervous system here which i think is pretty super cool and you'll
be talking about that in a lot more detail in the neurology or neuroanatomy portion of the course
these action potentials will actually travel along the muscle um the muscle cells plasma membrane
which you can see here and we'll talk a bit more about that in subsequent videos
and um this is this is possible due to these ion channels in these regions
now there are two main means of stimuli that can trigger action potentials in muscle cells you'll
have electrical which are particularly important in cardiac autorhythmic muscle and chemical which
are mostly or most commonly neurotransmitters released by neurons and this is particularly
important in skeletal muscle tissue so you will have acetylcholine that will be released and that
will lead to the action potential and we'll talk a bit more we won't get into the full physiology
here because this isn't a physiology course but we'll get a little into some of the specifics here
the last three properties intuitively go together so you'll have contractility which is exactly what
it sounds like it's a muscle's ability to contract when stimulated by those action potentials and
with contraction of a muscle this generates tension while pulling on attachment points
and we will talk about the different types of contraction which you can see here in this image
in another video but these will actually there will actually be some contractions
that will produce tension but no movement so there would be no muscle shortening
uh occurring and then in certain contractions you'll also actually have the muscle elongating
extensibility which is the ability of a muscle to stretch without sustaining damage and all muscle
can stretch to a certain extent and some muscle types can actually stretch quite a bit more than
others for example smooth muscle can stretch notably more than cardiac or skeletal muscle
in certain areas and lastly elasticity is going to be the fourth property and this is the ability
of muscle tissue to return to its original shape and length after extension or contraction so you
really need this last one in order for these to work efficiently there are four main functions
of muscle that are allowable based on those those muscle properties that we just discussed the first
is producing body movements all right and that one i think we all kind of know this is all body
movement so not just the obvious ones like walking or running but it'll play a role in things like
talking and even things like urination and many more functions of the body that involve movement
of some form a second function is stabilizing body position and this involves skeletal muscle in
particular we'll talk quite a bit about postural muscles which contract continuously to allow
for standing or sitting upright so those play a big role in terms of stabilizing body positions
next we will have storing and moving substances within the body and this is an important function
of cardiac muscle which will move blood throughout the body and smooth muscle in particular it will
move all types of substances throughout the body like food or bile sperm oocytes to name a few
skeletal muscle does play indirect roles in terms of
directing flow of lymph as well as deoxygenated blood through lower limb veins so
skeletal muscle will play a role here just not as large as the cardiac and smooth
and lastly and importantly a last function of muscular tissue will be that contracting muscle
will produce heat and this is a process called thermogenesis and you have likely experiences
particularly those of us that live in michigan in the winter through shivering which is involuntary
contraction of skeletal muscles shivering will dramatically increase the rate of heat production
so those are the four main functions of muscle that go along with the four
main properties of muscles so four plus four equals the function and properties of muscle
all right let's finish this video by reviewing a concept through assessment
so the question i'm going to ask you is which property of muscular tissue is shared with
nerve cells is it contractility b elasticity c electrical excitability or d extensibility pause
the video to think through this and review your notes if needed and when ready i want you to shout
out your answer it's fine you're probably doing this not around other people and even if you are
it will be fun to yell out c electrical excitability and that is the correct answer
the other answer choices are very much properties of muscle tissue but they are not properties
of nerve cells so contractility elasticity and extensibility are not correct but c electrical
excitability is all right that should be it for our discussion of the properties and functions of
muscle in the next video we will discuss some of the specifics of the three types of muscle tissue
thank you for your time and attention here and have a great rest of your day