Muscular Tissue Flashcards
What is the structure of muscular tissue?
Muscle tissue consists of elongagted cells; muscle cells/fibres/myocytes
that use energy from
the hydrolysis of ATP (adenosine
triphosphate) to generate force.
What are muscle tissues purpose?
As a result of contraction, muscle tissue produces body
movements, maintains posture and generates heat.
How many types of muscle tissue are there?
3
skeletal Muscle
Cardiac Muscle
Smooth Muscle
(comprimises 50% of the body tissue mass)
How many named skeletal muscle tissues are there in the body?
650
What do the attachment of skeletal muscles look like?
Usually attached to bones via tendons.
What is the appearance of muscle tissues under a microscope?
Appears striated.
Is skeletal muscle usually under voluntary or involuntary control?
Contraction is under conscious control (voluntary; sometimes not always - posture)
What is the appearance of skeletal muscle tissue fibres (=cells)?
long striated cells; cylindrical cells
Multinucleate (many
peripheral nuclei pushed
to side)
What is the smallest skeletal muscle (its size + function)?
Stapedius (1.25 mm)
(stabilizes the smallest
human bone the stapes in the ear; prevents “hyperacusis*”;
tympanic reflex; Bell’s Palsy; facial n)
What is the largest skeletal muscle (its size + function)?
Sartorius (upto 60 cm)
(“Checking for
gum!”; hip: flexor, abductor, lateral rotator; knee: flexor) .
What is the function of skeletal muscle?
Motion, Posture, Heat, Protection
What causes the striation of skeletal muscle fibres?
The striations of skeletal muscle fibres (cells) are due to the
highly organised arrangement of myofibrils within the cells
What are myofibrils role in muscle fibre cells?
Myofibrils (2 μm diam) more or less fill the cytoplasm (sarcoplasm)
of the muscle fibre and extend its entire length within the cell
What are the two types of filaments (myofilaments) in the myofibril called?
Thin fillaments; mostly composed of actin; 8 nm diam; 1-2 μm long
Thick filaments ; made up of myosin; 16 nm diam; 1-2 μm long
Do myofilaments extend the length of the muscle fibre like myofibrils do?
No, Myofilaments do not extend the length of the muscle fibre, but
are arranged in compartments called sarcomeres.
What is a sacromere?
the basic functional unit of a myofibril
What seperates the sacromere?
Z dics/z lines
What are the 5 main components of muscle tissue of skeletal muscle?
Epimysium
Perimysium
Endomysium
Sarcolemma
Sarcoplasm
What does the Epimysium surround?
The anatomy of the muscle
What does the Perimysium surround?
The entire fascicle
What does the Endomysium surround?
around
muscle fibers (“cell”) –
(layer for capillaries/nerves)
What is the Sacrolemma?
The actual cell plasma membrane
What is the Sarcoplasm?
The cell cytoplasm
What causes the striations in the myofibril?
The thin and thick myofilaments overlap causing the striations in the myofibril.
What does the A band do?
dark, middle part ; contains all the thick filaments
WHat does the I band do?
Contains all the thin filaments but no thick filaments
WHat does the H zone do?
thick filaments, but no thin filaments
What does the M line do?
Holds all the thick filaments together in the middle of the sacromere
WHat does the Z disc do?
passes through centre of I band (between sarcomeres) made up of
“actinins” – that link filaments of adjacent sarcomeres
WHat does titin do?
links Z disc to M line; provides
resting tension in I band, molecular spring
What is the structure of Cardiac muscle?
Striated and branched
Single central nucleus
How do fibres join in cardiac muscle?
Fibres join end-to-end through intercalated discs.
What junctions are intercalated discs composed of?
Desmosomes which allow for adhesion in contraction and binding of intermediate filaments
Gap Junctions which allow for communication- coordinated rapid conduction
Do cardiac muscles also have actin and myosin like skeletal muscle?
yes
What are “Purkinje fibres” role in cardiac muscles?
specialised muscle cells that conduct electrical activity around the heart. They have less myofibrils and more specialised “connexins” (gap junctions).
Where are cardiac muscles located?
Heart
Are cardiac muscles under voluntary or involuntary control?
Involuntary
Which of the 3 muscle tissues do not have striations? Cardiac, Skeletal or Smooth Muscle
Smooth Muscle
What is the location of Smooth Muscle?
walls of hollow internal structures
e.g. intestines (peristalsis); blood vessel walls (constriction);
also : Iris of eye, reproductive; digestive; respiratory; urinary; skin
erector pili
What is the structure of Smooth Muscle?
Short & small spindle shaped
about 30-200 μm long; 3-8 μm
thickest in the middle
SIngle central nucleus
Which of the muscle tissues does not have a single central nucleus?
Skeletal
Is smooth muscle invoulntary or voluntary?
Involuntary
Do smooth muscle also have actin(thin) & myosin (thick)
Yes have bundles of it
How do thin filaments attach in smooth muscle?
attach to “dense bodies”, functionally
similar to Z discs. (Dense body: a major protein is Actinin)
DO intermediate filaments (non contractile elements) also connect to dense bodies?
Yes
What happens during smooth muscle contraction?
During contraction tension is
transmitted to the
intermediate filaments (don’t
contract), and the cell twists
as it contracts about these
stable “rods”.
Relaxed is more long, Contracted is a squished up shorter and wider beehive
