Muscles Flashcards
how is movement brought about in our body
Movement is brought about by the skeletal muscles applying force to the bones and joints when they contract
what are the characteristic of skeletal muscle
- forms the skeletal muscles that are attached to the bony skeleton
- have stripes called striations
- can be controlled voluntarily
what are the key functions of muscles
- movement (when they contract and relax)
- posture and stability (the muscles are always in a state of slight tension - a condition called muscle tone)
- stabilizing joints (together with ligaments)
- generating heat (when they contract)
NAME THE DIFFERENT TYPES OF MUSCLE AND RECOGNIZE THEM
- skeletal muscle - strong, quick, discontinuous voluntary contraction
- cardiac muscle - strong, quick continuous involuntary contraction
- smooth muscle - weak, slow involuntary contraction
SLIDE 2 FOR RECOGNITION
Explain the structure of skeletal muscle
- A skeletal muscle is surrounded by a connective tissue sheath called the epimysium
- a skeletal muscle is made up of hundreds, or even thousands of elongated muscle fibers (muscle cells) surrounded by connective tissue called the endomysium
- a skeletal muscle has the muscle fibers grouped together in bundles called fascicles, surrounded by a layer of connective tissue called the perimysium
what is the endomysium
a thin layer of areolar connective tissue surrounding each muscle fiber or cell and contains capillaries and nerves
how is a muscle fiber formed
from the fusion of hundreds of embryonic cells
explain the structure of a muscle fiber
- large, elongated, cylindrical muscle cell
- many nuclei
- many mitochondria under the sarcolemma (the plasma membrane)
- the sarcoplasm contains large amounts of glycogen and myoglobin (an oxygen storing protein)
- has two sets of tubules - the sarcoplasmic reticulum (surrounding myofibrils -stores and releases calcium ions) - and the T tubules (extensions of the sarcolemma)
- made up of thousands of myofibrils made up of contractile protein filaments, stacked lengthwise
what do T tubules do
they conduct impulses from an action potential generated at a neuro-muscular junction to each sarcomere
LABEL THE STRUCTURE OF A SKELETAL MUSCLE AND MUSCLE FIBRE
PAGE 69
what is a myofibril
a complex organelle composed of bundles of myofilaments
what is the difference between myo and sarco
myo - inside
sarco- outside
LABEL THE STRUCTURE OF A MYOFIBRIL
PAGE 70
LABEL THE STRUCTURE OF A MYOFIBRIL
SLIDE 8
describe a myosin molecule
it has a stalk like tail from which two ‘heads’ stick out.
what are cross bridges and why
the heads of the myosin molecule because they link the thick and thin filaments during contraction of the muscles
describe the thick filament made of myosin
it consists of many myosin molecules where the heads stick out at the opposite ends of the filament, leaving the centre of the sarcomere with no heads, just tails
describe the thin filaments made of actin
they consist of actin molecules, made up of two polypeptide strands twisted together
LABEL A DIAGRAM OF MUSCLE DIFFERENTIATION
SLIDE 6
how is a myofibril made up
each myofibril is made up of parallel filaments forming a pattern of alternating:
• Dark A bands - consisting of thick filaments made up of the protein myosin
• Light I bands - consisting of thin filaments made up of the protein actin
— the dark A bands are bisected by the H zone where there are no overlapping actin filaments
— the light I bands are bisected by the Z line, a dense area to which the actin filaments are attached
• the the filaments between the Z lines form a sarcomere (which is the functional part of a muscle, the part that actually contracts)
How do muscles contact
- actin filaments slide past myosin filaments, towards the counter of the A band (the A band is region of thick filaments with thin filaments overlapping)
- Z lines come closer to the thicker filament region (A band region)
- the H zones disappear
- A band region appears closer together while not changing the width
— all resulting in contraction
Explain the sliding filament theory
motor neuron + muscle fiber = motor unit
• Axon terminals form a neuromuscular junction with each muscle fiber
• when nerve impulses are transmitted to the muscle fibers, the following occurs:
— calcium ions are released from the sarcoplasmic reticulum (necessary to expose the active binding sites on the actin molecules)
— myosin cross bridges attach to the binding sites
— myosin heads attach and detach using energy from ATP to ADP hydrolosation
DRAW A DIAGRAM SHOWING THE SLIDING FILAMENT THEORY
SLIDE 12
how do bones act as levers
when a muscle contracts the bone is moved at a joint
bones act as levers and joints act as fulcrums for these levers
— A force of effort is used to move a resistance or load, the effort is provided by a muscular contraction and is applied at the point of insertion on the bone
what type of levers are there
class 1 (the best) - eg. see saw, your axis and atlas vertebrae when you look up
class 2 (2nd best) - eg. a wheelbarrow, your ankle and ball of foot when you walk
class 3. (least effective) - eg. lifting a shovel with dirt, working out your arms and doing a curl with a weight
why are antagonistic muscles required
in order to reverse a muscular movement
give an example of an antagonistic pair of muscles
the bicep flexor (tighten) and tricep extensor (extend)
what is an example of a muscular disorder, elaborate on it
muscular dystrophies
— a group of more than 30 genetic diseases that cause progressive weakness and degeneration of the skeletal muscles that control movement
what is the most common form of muscular dystrophy - elaborate on it
Duchenne MD
— the diseased muscle fibers lack a protein called dystrophin
— this protein is essential for keeping the sarcolemma in a healthy state
— the disease is caused by an inherited X linked recessive gene, carried by females but expressed almost exclusively in males
symptoms of duchenne MD
usually diagnosed between the ages of two and six
- the affected muscles enlarge due to deposits of fat and connective tissue
- the muscle fibers of the skeletal muscle degenerate and atrophy, causing frequent falls and difficulty running or jumping
- the disorder progresses very quickly snd many sufferers are unable to walk by the age of 12
- it progresses from the extremities upward, finally effecting the head and chest at which point a respirator is needed to breathe
- those effected rarely live beyond their early 20’s as they die from respiratory failure
what is the cure and treatment for Duchenne MD
there is no cure as it is genetic but there are medications that can slow does the progression of the disease
• various types of physical therapy, meds, surgery and devices that help walking are used to help reduce deformities
• support groups provide a place where people can share their common problems and provide support for one another
• myoblast transfer therapy which involves injecting diseased muscle cells with healthy myoblast cells (which are embryonic cells that develop into muscle cells) these cells provide the normal gene that allows the fibers to start producing dystrophin
what is a cramp and how is it caused
A cramp is a sustained spasm of an entire muscle
caused by:
• A mineral deficiency of calcium and or magnesium ions
•a lack of sodium or potassium ion both of which results in an electrolyte imbalance
•low blood sugar level
•dehydration
•irritability of the spinal-cord neurons
How do you relieve cramp pain
If you are in bed when you get a leg cramp stretch your legs straight out and bend the toes back and toward your head, hold in this position for 30 seconds, relax and repeat, until the cramp is gone. this will stretch out your calf muscle
if cramping occurs while you’re exercising follow these tips:
• keep hydrated as you lose important electrolytes when you sweat
• warm up for 10 to 15 minutes before exercising to stretch out the muscles you will be using
• take magnesium potassium and calcium supplement daily
