Aggregate of cells and intercellular substances specialized to perform a particular function
While the size of a band changes during contraction and relaxtion does the actin and myosin length itself?
What colour is the I band? A band?
I = light
A = dark
What are 4 basic tissues?
A cyte is a _____ cell? While a blast is a _____ cell?
In skeletal muscle where do we find th enucleus almost always? Why?
On the edge of the fiber
Cause all th ebands push it there
What is a satellite cell?
sits in basement membrane essentially undifferentiated stem cell, can add nuclei to the muscle fibers and make it grow
When you excersise do your muscles grow or do you get more of them?
Describe hypertrophy in muscle cells?
Increase in size
What is a myofibril?
Bundle of actin and myosin within a cell
Differentiate between a myofibre and myofibril
Fibre is cell fibril is within a cell
Define endomysium, epimyisum, and perimysium
Endo = inbetween individual cells
Peri = inbetween bundles
Epi = on outside of muscle
Are the bands in a muscle all lined up generally evenly? Like A to A and I to I?
Yes usually to an extent
Holes on surface of the sarcolemma leading to tubes used to conduct electricity are called?
Why do T tubules make sense for skeletal muscle
Generally we want the entire muscle fibre to contract at once the myofibrils on the inside and outside so the T tubules allow penetration through the entire cell and allow the AP to stimulate everything
Generally in other kinds of muscle this perfect timing is not so important
Plasma membrane in muscles is the ? What about smooth ER?
What band disappears during contraction (or can)?
What is a motor unit?
A group of fibers to be contracted at once, 1 nerve for tonnes of fibers
What is the thin filament?
What covers the binding sites on actin?
What pulls the troponin complex off of the actin?
The tail of myosin is made of what?
2 heavy chais twisted around eachother
is myosin directly anchored itself to the Z line? What about actin?
No only through titin
A sarcomere is measured from?
Z line to Z line
Why do we see bands in the first place? What band is within the A band? What line is within that?
Cause different proteins make up different bands
which fiber type (red/white) is faster? Uses mor Oxygen? has more mitochondria? is anaerobic primarily?
What is the purpose of a muscle spindle?
TO gauge the tension on the muscle
Do skeletal muscles have gap junctions?
Nope they are all one cell why would they need it
In cardiac muscles what connects cells
Are cardiac muscle cells as long and connected as skeletal?
No they are short and autonomous
Are cardiac muscles controlle dby the brain at all?
No they are purely autonomous
How is myofilament shape in cardiac muscles? do we see striations and the same movement?
Yes it is it the exact same and you get the same movement however the shape of the cell is not the same
on a transverse cut through thecardiac muscle we happened to cut right through a nucleus and it appeard as a black dot surrounded by an empty space? What is the space for?
Storage space for glycogen and lipids
Where would we expect to see more mitochondria in cardiac muscle or smooth muscle?
Cardiac muscle cause it runs contantly and is unyielding can see as much as 20-40% of cytoplasm as mitochondria
Do we see the same level of SR in the cardiac muscle?
No it is less developed which means that we don't rely on it as much and T tubule does more Ca release
Name 4 differences between skeletal and cardiac muscle
Cardiac is not one giant long multi nucleated cell, a lot more mitochondria, not as developed SR, autonomous
Do we still the banding pattern in muscles when O 2 is lost?
No and they contract in a funny way
How many arteries does the heart have? How does gthis compare to other important organs? Describe the relevance to myocardial infarction
If it gets plugged with plaque you die
in the intercalated dsics of cardiac muscle cells what are some things we find? What do these look like?
gap junctions on the vertical part that done support any tension
Spot welds (des) and discs (gap junctions)
describe how the muscle cells in the heart communicate and how this gives a very rhythmic contaction profile of it
They are not all connected and so there is a lag while they communicate vetween the gap junctions this means cell #2 contracts some time after Cell #1 after this lag occurs causing a drawn out squezzing effect
if all the muscles contracted at once in the atrial the blood would go no where
Cardiac impulse conducting fibers are also known as?
Purkinje fibers fire because of what?
They are very leaky and so spontaneously fire at a base frequency
Where do purkinje fibers originate?
Nodes such as the AV or Sa node
Histologically what do purkinje fibers look like?
A lot larger in cross diameter than cardiac muscles
How does the action potential spread through cardiac muscle?
Through the gap junctions to the next cell
This causes orderly and sequential contraction
Do cardiac muscles have satellite cells?
Can the heart beat without the brain?
Yes it is autanomous
What determines the strength of a contraction in skeletal muscle as compared to cardiac muscle?
Skeletal muscle it is the number of fibers contracting but all fibers go full force
In cardiac muscle it is the extent the cells contract but they all contract
Is the cardiac muscle able to divide at animal maturation?
No the ability to divide is lost after birth
How does the heart grow?
Heart grows cause cells and individual fibres grow
Damage to the heart wall (infarction leads to death of myocytes. What usually fills this gap?
Connective tissue proliferation
How does smooth muscle appear? Does it have any striations? Why does it appear smooth?
Smooth and silky
Cause actin and myosin are not in any definitive arrangement like in the other muscles and therefore don't make a pattern
Which muscle type is the most efficient and has the highest amount of contracting power
What is the shape of a smooth muscle cell and what is the shape of the nucleus
Cigar shaped nucleus and a spindle shaped cell
What interconnects muscle fibers?
In the intestines how many layers of muscle are there?
Do all visceral orgajns have smooth muscle?
Yes to an extent
Does each smooth muscle need its own nerve?
No one nerve kind of dumps out and many muscle cells pick it up
Do Smooth muscles have T tubules?
No they lack that entire system they have vesicles that take in Ca and the contraction mechanism is completely different
What are dense bodies?
They are places where both actin and intermediate filamnents in smooth muscle attach to both in the cytosol and on the plasmalemma it is there anchor per say
What is a third type of filament smooth muscle cells have?
Intermediate filaments made of desmin
Smooth muscle is a very efficient contractor, describe what we see in a smooth muscles appearanbce when it contracts
It contracts so much that is essentially bundles up and kinks
What do we call a neuromuscular synapse in a muscle?
A motor end plate
What is the difference in muscle spindles in smooth muscle?
They are very prominent so w e often study them here
Describe what is inside a muscle spindle?
Modified skeletal muscles much smaller with a capsule surrounding it
Sensory nerves within it detect how much muscle is being contracted and makes the brain think about the tension