Muscles

Question 1

how is movement brought about in our body

Answer 1

Movement is brought about by the skeletal muscles applying force to the bones and joints when they contract

Question 2

what are the characteristic of skeletal muscle

Answer 2

• forms the skeletal muscles that are attached to the bony skeleton
• have stripes called striations
• can be controlled voluntarily

Question 3

what are the key functions of muscles

Answer 3

• 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)

Question 4

NAME THE DIFFERENT TYPES OF MUSCLE AND RECOGNIZE THEM

Answer 4

• skeletal muscle - strong, quick, discontinuous voluntary contraction
• cardiac muscle - strong, quick continuous involuntary contraction
• smooth muscle - weak, slow involuntary contraction

SLIDE 2 FOR RECOGNITION

Question 5

Explain the structure of skeletal muscle

Answer 5

• 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

Question 6

what is the endomysium

Answer 6

a thin layer of areolar connective tissue surrounding each muscle fiber or cell and contains capillaries and nerves

Question 7

how is a muscle fiber formed

Answer 7

from the fusion of hundreds of embryonic cells

Question 8

explain the structure of a muscle fiber

Answer 8

• 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

Question 9

what do T tubules do

Answer 9

they conduct impulses from an action potential generated at a neuro-muscular junction to each sarcomere

Question 11

LABEL THE STRUCTURE OF A SKELETAL MUSCLE AND MUSCLE FIBRE

Answer 11

PAGE 69

Question 12

what is a myofibril

Answer 12

a complex organelle composed of bundles of myofilaments

Question 13

what is the difference between myo and sarco

Answer 13

myo - inside

sarco- outside

Question 15

LABEL THE STRUCTURE OF A MYOFIBRIL

Answer 15

PAGE 70

Question 16

LABEL THE STRUCTURE OF A MYOFIBRIL

Answer 16

SLIDE 8

Question 17

describe a myosin molecule

Answer 17

it has a stalk like tail from which two ‘heads’ stick out.

Question 18

what are cross bridges and why

Answer 18

the heads of the myosin molecule because they link the thick and thin filaments during contraction of the muscles

Question 19

describe the thick filament made of myosin

Answer 19

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

Question 20

describe the thin filaments made of actin

Answer 20

they consist of actin molecules, made up of two polypeptide strands twisted together

Question 21

LABEL A DIAGRAM OF MUSCLE DIFFERENTIATION

Answer 21

SLIDE 6

Question 22

how is a myofibril made up

Answer 22

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)

Question 23

How do muscles contact

Answer 23

• 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

Question 24

Explain the sliding filament theory

Answer 24

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

Question 25

DRAW A DIAGRAM SHOWING THE SLIDING FILAMENT THEORY

Answer 25

SLIDE 12

Question 26

how do bones act as levers

Answer 26

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

Question 27

what type of levers are there

Answer 27

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

Question 28

why are antagonistic muscles required

Answer 28

in order to reverse a muscular movement

Question 29

give an example of an antagonistic pair of muscles

Answer 29

the bicep flexor (tighten) and tricep extensor (extend)

Question 30

what is an example of a muscular disorder, elaborate on it

Answer 30

muscular dystrophies — a group of more than 30 genetic diseases that cause progressive weakness and degeneration of the skeletal muscles that control movement

Question 31

what is the most common form of muscular dystrophy - elaborate on it

Answer 31

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

Question 32

symptoms of duchenne MD

Answer 32

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

Question 33

what is the cure and treatment for Duchenne MD

Answer 33

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

Question 34

what is a cramp and how is it caused

Answer 34

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

Question 35

How do you relieve cramp pain

Answer 35

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