Muscles Flashcards
What is a muscle?
pieces of soft tissue throughout the human body
What is the dominant tissue throughout the heart and walls of other hollow organs?
muscle
What moves and supports body organs?
muscle
How much of the body mass does muscle form?
nearly half
How many muscles are there in the human body?
over 600
what are the four properties of muscle?
excitability
contractility
elasticity
extensibility
What is electrical excitability?
The ability to respond to stimuli from neurotransmitters
What are neurotransmitters?
chemicals by which neurons translate
What can stimulation from neurotransmitters to muscles eclicit?
an action potential or nerve impulse
What is contractibility?
The ability of a muscle to shorten in response to an action potential
What is extensibility?
The ability of a muscle to stretch without injury
What is elasticity?
The ability of a muscle to recover its original shape after contracting or extending
What are the 7 functions of the muscular system?
- body movements
- stabilizing joints
- maintaining body posture
- storing substances
- movement of substances
- thermogenesis
- communication
What is thermogenesis?
The production of heat as a by-product of contraction
How does the muscular system allow body movements?
by contracting and releasing around joints
What substances does the muscle move around the body? name 3
- blood
- air
- food
What are the three types of muscle?
- cardiac muscle
- Skeletal muscle
- smooth muscle
Where is cardiac muscle found?
only in the heart
What forms the bulk of the heart wall (myocardium)?
cardiac muscle
What does the cardiac muscle do?
contracts rhythmically and continuously to provide the pumping action necessary for life
What other muscle type is cardiac muscle similar to in structure?
skeletal muscle
What are the two names for a cardiac muscle cell?
- cardiac muscle fibre
- cardiomyocyte
What is the structure of cardiac muscle?
does not taper but forms intercalated discs
What is a syncytium?
a unit of combined cardiac muscle cells
What kind of mitochondria does cardiac muscle have? why?
large mitochondria for a constant supply of energy
What are smooth muscles?
unstriated involuntary muscles found in internal organs
Where are smooth muscles found? (3)
internal organs
blood vessels
the intrinsic muscle of the eye
What do smooth muscles enable? give an example
involuntary visceral contraction such as vasoconstriction
Do smooth muscles have striations or T-tubules?
no
How are smooth muscles organised?
loosely in the sarcoplasmic reticulum
How are the thick and thin filaments in smooth muscle arranged? what happens when they contract?
they are arranged differently and when contracted pull the cell into a ball
which muscle cells can be single unit or multi unit?
smooth muscle cells
How do single-unit muscle cells contract?
as one unit
How do multi unit muscle cells contract?
they contract on the cell stimulated
Where are single unit muscle cells found?
on the walls of hollow organs
Are single or multi unit muscle cells more common?
single unit muscle cells are more common
Where are multi unit muscle cells found? (3)
around large blood vessels, in the respiratory airways and in the eyes
In the structure of a skeletal muscle, what is the endomysium?
a thin layer of delicate connective tissue that surrounds each individual muscle fiber
In the structure of a skeletal muscle, what is the perimysium?
a layer of collagenous connective tissue that separates the muscle tissue into bundles (fascicles)
In skeletal muscle structure, what is a fascicle?
a bundle of skeletal muscle fibers
In skeletal muscle structure, what is the epimysium?
a dense layer of connective tissue that surrounds the entire muscle
Where in the muscle does the tendon anchor the bone to the muscle?
at the epimysium
Instead of a tendon, what else can anchor muscle to bone?
the aponeurosis
What is the aponeurosis?
a flat sheet of connective tissue that can connect muscle to bone
what are the three general functions of skeletal muscle tissue?
- movement
- Heat production
- posture
What are the three main characteristics of skeletal muscle tissue?
- excitability or irritability
- Contractability
- Extensibility
What is excitability or irritability in skeletal muscle tissue?
the ability to respond to stimulus
What is contractibility in skeletal muscle tissue?
the ability to shorten in length
What is extensibility in skeletal muscle tissue?
the ability to extend in length
A skeletal muscle cell is an individual _______
fibre
Each muscle fibre is composed of several hundred to several thousand _________
myofibrils
What are myofibrils in skeletal muscle cells?
a contractile structure within a muscle fibre containing protein filaments called thick and thin myofilaments
What do myofilaments do in skeletal muscle cells?
they slide against each other when the muscle contracts
What is the sarcolemma of skeletal muscle cells?
the tubular sheath that encases each muscle fibre, it is plasma membrane or wall
What is the sarcoplasm of a skeletal muscle cell?
the cytoplasm
What is cytoplasm?
the gelatinous liquid that fills the inside of a cell
What are transverse tubules in skeletal muscle cells?
the entry point for action potential into the muscle cell
What is the sarcoplasmic reticulum in skeletal muscle cells?
a network of tubules and sacs involved in the storage of calcium
what are the 7 general skeletal muscle shapes?
- parallel muscles
- Convergent muscles
- Unipennate
- bipennate
- multipennate
- Fusiform muscles
- Circular muscles
What are the 3 subcategories of pennate muscles?
- unipennate
- bipennate
- multipennate
Describe the shape of parallel skeletal muscles. Give an example.
Long, strap like muscles such as the sartorius muscle (runs from thigh to knee)
Describe the shape of convergent skeletal muscles. Give an example.
fanning fibres from a narrow to a wider point, such as the pectoralis.
Describe the shape of pennate skeletal muscles. Give an example.
featherlike in appearance, eg rectus femoris
Describe the shape of fusiform skeletal muscles. Give an example.
have fibres that are parallel in the centre but taper on the ends to form one or two tendons. strap like. Such as biceps brachii.
Describe the shape of circular skeletal muscles. Give an example.
circular in shape. Also known as sphincters such as the orbicularis oris (around the mouth).
what is the origin of a muscle?
the point of attachment which does not move when the muscle contracts
what is the insertion of a muscle?
the point of attachment that moves when contracts
what is meant by the term prime mover when referring to muscles?
the muscle that directly performs movement
What is the other name of prime movers?
agonists
What is the antagonist in mucles?
the muscle that does the direct opposite of the agonist, relaxes to allow movement
What are the syngergists in muscles?
muscles that contract at the same time as the prime mover
what are fixators in muscles?
the muscles that stabilize the joint
Describe the structure of fibers in skeletal muscle?
striated, tubular and multi nucleated
Are skeletal muscles voluntary?
yes
Where are skeletal muscles usually attached in the body?
the skeleton
describe the structure of fibers in smooth muscle.
non-striated, spindle-shaped and uni(one)nucleated
Is smooth muscle voluntary or involuntary?
involuntary
where is smooth muscle usually located in the body?
covering walls of internal organs
Describe the structure of fibres in cardiac muscle? (3)
striated, branched and uni nucleated
are cardiac muscles voluntary or involuntary?
involuntary
Where are cardiac muscles found in the body?
only covering the walls of the heart
