chapter 13 (13.9 and 13.10) Flashcards
what is the cytoplasm of a muscle cell called
the sarcoplasm
what is the specialised/modified endoplasmic reticulum in a muscle cell called
the sarcoplasmic reticulum
what is included in the triad
the end of the t-tubule the sarcoplasmic reticulum and the start of the z line
what are the 3 types of muscle
skeletal
cardiac
smooth
which ns are skeletal muscles controlled by
the somatic ns
are skeletal muscles voluntary or in
voluntary (under conscious control
is cardiac voluntary or in
involuntary not under conscious control
which ns is cardiac muscle controlled by
autonomic ns
where is smooth muscle found
wall of hollow organs eg stomach and intestine (viscera)
walls of blood vessels
respiratory system
eyes
skin
is smooth muscle voluntary or in
involuntary not under conscious control
which ns controls smooth muscle
autonomic
what is the name of the smooth muscle that is in the skin
erector pili muscles
compare length of contraction (duration) for the 3 types of muscle
skeletal- short
cardiac- intermediate
smooth- can remain contracted for relatively long time
compare the speed of contraction for the 3 types of muscle
skeletal- rapid
cardiac- intermediate
smooth- slow
which muscles are striated
skeletal
cardiac yes but faintly
smooth nonstriated
compare the arrangement of muscle cells in each muscle and how it relates to the direction of contraction
skeletal- regularly arranged so muscle contracts in one direction
cardiac- cells branch and interconnect so simultaneous contraction occurs.
smooth- no regular arrangement- different cells can contract in different directions
compare the amount of nuclei in the cells of all 3 muscle types
skeletal- multinucleate
cardiac and smooth- uninucleate
function of cardiac muscle
allows the heart to pump blood
function of skeletal muscle
to move limbs
function of smooth muscle
to move substances through organs, blood vessels etc
which neurotransmitters are involved in all 3 muscle types
all acetylcholine
cardiac and smooth- noadrenaline
smooth- other hormones as well
which type of muscle is myogenic and what does that mean
cardiac
they contract without the need for nervous stimulation so the heart is able to beat at a regular rhythm
what connects gap junctions/the branches in cardiac muscle
intercalated discs
are there junctions between fibres in skeletal
no
in muscle what are muscle cells called
muscle fibres or myocardiocytes in cardiac muscle
they are a single muscle cell is an elongated cell that looks like a thread, this is called a muscle fibre
in skeletal muscle the fibres are ……. in origin and …… (amount of nuclei per cell
multicellular and multinucleate
skeletal muscles are tubular true or false
true
what is a sarcomere
a functional unit of muscle
one repeat of the pattern of light and dark bands
a protein stack of at least 4 AFs and one MF in the middle
A sarcomere is defined as the distance between adjacent z line son a myofibril
where is the sarcomere
it is the segment between the two adjacent z lines
what are muscle fibres like in smooth muscle (shape)
spindle shaped with a wide middle and tapering ends
which muscle cells are branched and which are tubular
branched- cardiac
tubular- skeletal
what are muscle cells like in skeletal muscle
theyre extremely long and are make up from many embryonic muscle cells fusing together to make up muscle fibres making them stronger by reducing cell junctions laterally
bundles of muscle fibres are covered by an additional plasma membrane called the
sarcolemma
the sarcolemma folds inwards to form
transverse tubules or T tubules
what are transverse tubules for
they increase the surface area of the sarcolemma, they help to spread the electrical impulse throughout the muscle to allow it to contract as a whole
there are many of which organelle to provide ATP for contraction
mitochondria
what is special about the sarcoplasmic reticulum
it contains many Ca2+ for the muscle fibre to contract
what are myofibrils
they are special organelles which allow the muscle fibre to contact longitudinally
inside a muscle fibre there are more tubular structures they are cell organelles canned myofibrils
muscle fibres contain many myofibrils
myofibrils are made up of many repeating sarcomeres
what two types of protein filaments are myofibrils made from
actin and myosin
which out of actin and myosin is thicker
myosin is thicker and actin is thinner
what is the structure of actin filament
two actin molecules twisted around each other
what is the structure of myosin filaments
many bulbous headed myosin molecules wrapped around into a bundle
to form a myosin filament one thread is bundled together with many other threads
myosin filaments are made up of myosin protein, forming 2 myosin filaments that are wrapped around each other
what type of proteins are actin and myosin and what about the head and what 2Y structure do they have
both fibrous however the myosin head is globular
beta pleated sheet
what is the appearance of myofibrils
striped with light and dark bands
what is the light band also known as
I band
isotropic band
what IS the light band
where actin and myosin filaments do not overlap
what is the dark band also known as
A band
anisotropic band
what IS the dark band
where actin and myosin filaments overlap, it contains the entire length of a myosin filament
there is a strip of lightness in the middle of which band
the dark band
why does the dark band have a light strip in the middle and what is it called
where there is no actin this is called the H zone
what do the myosin heads have on them
actin binding sites and atp binding sites
are myosin heads ATPases
yes
the myosin head it ….. and will ……. because theyre
flexible and will move because they are hinged
the tails of several hundred myosin … align to form the myosin ……
molecule
filament
what does actin have on it
binding site for mysin
the actin myosin binding sites are usually blocked by what and it is held in place by what
tropomyosin and it is held in place by troponin
what is hidden underneath tropomyosin
binding sites for myosin heads
what is tropomyosin and where is it
it is a fibrous protein chain that wraps around the actin filaments
what is the z line
the zig zaggy line
in the centre of each light band, it is made from several proteins and consists of actin filaments
the z line creates transverse ………. for the sarcomere
stability
what is the m line
a line through the middle of the sarcomere
it consists of myosin filaments
what makes up the microfibrils in the sarcomere
myosin and actin
what is the actin attached to
the z line
when a muscle contracts what happens to the I band
it gets smaller
when a muscle contracts what happens to the A band
it stays the same
when a muscle contracts what happens to theH zone and why
reduces as actin slides over myosin
when a muscle contracts what happens to the z lines
they get closer together
Within muscle, thin and thick filaments can be found in…
microfibrils
a sarcomere is made up of how many z and m lines
2 z, 1 m
why is the light band light
because actin filaments are thinner letting more light through
what are the 3 souces of atp for muscles contraction
aerobic respiration
anaerobic respiration
creatine phosphate
when is aerobic respiration used for muscle contraction
when atp demand matches glucose and o2 supply
when is anaerobic respiration used for muscle contraction
when atp demand is greater than the glucose and o2 supply
when is creatine phosphate used for muscular contraction and how
when atp demand is greater than the glucose and o2 supply
creatine phosphate phosphorylates adp to make
this process is anaerobic as it doesnt require o2
The use of phosphocreatine is triggered by anaerobic respiration. This increases the anaerobic production of ATP for muscle contraction.
what triggers the actin and myosin filaments to move
the action potential
The movement of actin and myosin is the result of a(n) …….. that is triggered inside a muscle fibre of a(n) ……….. junction.
action potential
neuromuscular junction
What are the three types of muscle found in the body?
skeletal, cardiac and smooth/involuntary muscle.
Which type of muscle is under voluntary control?
skeletal
Which type of muscle has the slowest contraction speed?
smooth
What two types of muscles are striated?
cardiacand skeletal.
Which type of muscle is branched?
cardiac
Which type of muscle is multinucleated?
skeletal
Which type of muscle is capable of remaining contracted for relatively long periods of time?
smooth
What is actin?
a molecule that forms the …….
Actin is a molecule that forms the thin protein filaments in myofibrils in muscle fibre.
what is myosin
a molecule which forms the
thick protein filaments in myofibrils in muscle fibre
What is the name of the band on a sarcomere where actin and myosin do not overlap?
i band
What is the name of the band on a sarcomere where actin and myosin do overlap?
a band
Which protein filament is present in the H zone of a sarcomere?
myosin filament
What is the neuromuscular junction?
The neuromuscular junction is where a(n) motor neurone meets a(n) skeletal muscle fibre
Which ions are released when an action potential reaches a neuromuscular junction?
calcium ions
step 1 of sft: calcium ions trigger
Calcium ions trigger tropomyosin to move away from actin binding sites.
What is the neurotransmitter found in the neuromuscular junction?
acetylcholine
Which enzyme breaks down the neurotransmitter found in the neuromuscular junction?
Acetylcholinesterase/ACh esterase, AChE, AChase, acetylhydrolase
What change occurs when an ATP molecule binds to the myosin head during muscle contraction?
The myosin head detaches from the actin filament.
What change in the myosin head takes place when energy is released by the hydrolysis of ATP?
The myosin head changes its angle or shape causing it to return to its original position.
Energy from the hydrolysis of ATP is needed for what two processes during muscle contraction?
Movement of myosin heads and active transport of calcium ions back into the sarcoplasmic reticulum
Without the presence of calcium ions, tropomyosin… (link to myosin and actin)
blocks binding sites on actin.
prevents myosin heads from attaching to actin.
With the presence of calcium ions, tropomyosin…
changes shape and moves away from binding sites on actin.
allows myosin heads to attach to actin
What is the role of creatine phosphate in muscle contraction?
To act as a reserve supply of phosphate ions to reform ATP quickly during short bursts of high activity.
what 2 things are directly responsible for the movement of actin and myosin inside a myofibril
Action potential inside the muscle fibre
Presence of calcium ions
not the Action potential inside the sarcoplasmic reticulum because
The sarcoplasmic reticulum is found outside of the myofibril.
explain why the 2 bands looks different ( I and A)
A band contains myosin/thick filaments
I band contains only actin/thin filaments
identify 3 proteins that make up the filaments labelled z (filaments in the light band)
actin
troponin
tropomyosin
use your knowledge of the sliding filament model of muscle contraction to explain why fig represents contracted muscle (3)
what does a contracted sarcomere look like
i band is smaller
a band remains the same
sarcomeres are shorter
h zone becomes smaller
there is a greater overlap between actin and myosin (filaments)
What is formed when a myosin head attaches to the binding site on actin?
an actinomyosin bridge (or actin-myosin cross bridge) is formed.
step 2 of sft
During muscle contraction, the ……….. moves along the actin, causing the actin to end up closer to the ……. of the sarcomere. This is known as the ……
myosin head
m line
power stroke
Actin filaments slide along the myosin filaments during each power stroke of a myosin head.
what triggers the power stroke of the myosin head
ADP and Pi are released
step 3 and 4 of sft
ADP and Pi are released from myosin head.
ATP binds to myosin head and myosin head detaches from actin.
step 5 of sft
ATP is hydrolysed into ADP and Pi and myosin head returns to its starting position.
