Muscles

Question 1

What are the three types of muscle tissue?

Answer 1

1) skeletal muscle
2) cardiac muscle
3) smooth muscle

Question 2

what functions does muscle contraction have?

Answer 2

1) body movement
2) stabilization of body position
3) movement of substances through the body
4) generating heat to maintain body temperature

Question 3

what type of muscle is skeletal muscle?

Answer 3

voluntary - control it consciously

- it connects one bone to another . muscle is not att directly to the bone, its att via a tendon

Question 4

How do muscles work in groups?

Answer 4

agonist (muscle resp for movement) contracts while the antagonist stretches.
when the antagonist contracts, the bone move into opp direction , stretching the agonist!

there are also synergistic muscles- assist the agonist by stabilizing the original bone

Question 5

what else can contraction of skeletal muscle cause?

Answer 5

• squeeze blood and lymph vessels aiding in circulation

- also produces heat

Question 6

what is the smallest functional unit of skeletal muscle?

Answer 6

sarcomere

Question 7

what is a sarcomere made of?

Answer 7

many strands of two protein filaments (thick and thin filaments)
sarcomere are laid side-side to form myofibril. each myofibril is surrounded by specialized endoplasmic reticulum of the muscle cell called the sarcoplasmic reticulum. a modified mem called sarcolemma wraps several myofibrils together to form muscle cell or muscle fibre.

Question 8

Sarcoplasmic reticulum..

Answer 8

lumen is filled with calcium ions .

Question 9

skeletal muscle is ____ nucleate

Answer 9

multi

Question 10

what is the thick filament of a sarcomere made of ?

Answer 10

protein myosin

Question 11

What is the thin filament composed of?

Answer 11

actin (globular protein)- attatched to the actin are proteins troponin and tropomyosin

Question 12

How does contraction of the skeletal muscle occur?

Answer 12

myosin and actin work together sliding alongside each other to create the contractile force of skeletal muscle.
each myosin head crawls along the actin in a 5 stage cycle.

Question 13

what are the 5 stages of contraction?

Answer 13

1) tropomyosin covers an active site on actin - that prevents myosin head from binding. the myosin head remains cocked in a high energy position with a phosphate and ADP group att
2) in presence of ca2+, troponin pulls tropomyosin back , exposing active site, allows myosin head to bind to the actin
3) the myosin heads expels the phosphate and ADP and it bends into a low energy position , dragging the actin along with it ( this is called the power stroke bc it causes shortening of sarcomere and muscle contraction)
4) ATP attaches to the myosin head, this releases myosin head from the active sire, which is covered immediately by the tropomyosin
5) ATP splits into inorganic phosphate and ADP causing myosin head to cock into high energy position .

Question 14

what does the muscle contraction begin with?

Answer 14

action potential
- a neuron attaches to a muscle cell forming a neuromuscular synapse. the action potential of a neuron will release acetylcholine- which activate ion channels in sarcolemma of muscle cells , creating an action potential.
which moves deep into muscle via small tunnels called t tubules.

Question 15

what do the t tubules allow?

Answer 15

uniform contraction of muscle by allowing the action potential to spread through the muscle cell more rapidly
the action potential is spread through the muscle cell more rapidly. The action potential is transferred to the sarcoplasmic reticulum, which suddenly becomes permeable to calcium ions. the calcium ions begin 5 stage cycle . at the end of the cycle, calcium is actively pumped back into sarcoplasm reticulum

Question 16

what is a motor unit?

Answer 16

a motor unit consists of a nerve and all muscle fibres that synapse with the nerve

• motor units are independent of each other .
• force of contracting muscle depends upon number and size of active motor units and the freq of action potentials in each neuron of motor units
• smaller motor units work faster compared to bigger ones

Question 17

what are the THREE type of skeletal muscle fibres?

Answer 17

1) slow oxidative type (type 1)
2) fast oxidative type (type 2 a)
3) fast glycolytic type (type 2 b) fibers

Question 18

type 1 - slow oxidative type

Answer 18

red from large amount of myoglobin - which an oxygen storing protein (myoglobin has 1 subunit)
- therefore have large amounts of mitochondria- they split ATP at a slow rate- so they are slow to fatgiue, but also have a slow contraction speed

Question 19

type 2 a - fast oxidative fibers

Answer 19

also red ! but they split ATP at a higher rate! these contract rapidly, these are resistance to fatigue but not as resistance then type 1

Question 20

type 2 b - fast glycolytic fibers

Answer 20

low myoglobin content, appear WHITE ! contract very rapidly

they have large amount of glycogen

Question 21

do muscle cells undergo mitosis?

Answer 21

human muscle cells are very speacilized - lost ability to undergo mitosis

Question 22

what does myoglobin do?

Answer 22

stores oxygen inside muscle cells. - its one subunit ! - so stores one oxygen molecule

Question 23

cardiac muscle is started like…

Answer 23

skeletal muscle

Question 24

started muscles (cardiac and skeletal ) are striated bc …

Answer 24

they have sarcomeres!

Question 25

cardiac muscle unlike skeletal muscle has…

Answer 25

one nucleus.. and is separated from its neighbour by an intercalated disc

Question 26

what do the intercalated discs have?

Answer 26

gap junctions- which allow action potential to spread from one cardiac cell to the other via electrical synapses

Question 27

cardiac muscle is…

Answer 27

involuntary

Question 28

the action potential of cardiac muscle exhibits a plateau after …

Answer 28

depolarization ! this plateau is created by slow voltage gated Ca channels which allow calcium to enter and hold the inside of the membrane at a positive potential difference. the plateau lengthens the time of contraction

Question 29

without the calcium …

Answer 29

heart would beat too fast and we would die

Question 30

Smooth muscle is involuntary therefore its innervated by the …

Answer 30

autonomic nervous system

Question 31

smooth muscle has one nucleus like…

Answer 31

cardiac muscle! skeletal muscle has many nuclei

Question 32

smooth muscle also has thick and thin filaments ..

Answer 32

but they are not organized into sarcomeres.

Question 33

smooth muscle has intermediate filaments… what do the intermediate filaments do?

Answer 33

intermediate filaments are attatched to dense bodies spread through the cell. the thick and thin filaments are attatched to the intermediate filaments and when they contract the intermediate filaments will pull the dense bodies together.

Question 34

what are the two types of smooth muscles?

Answer 34

1) single unit

2) multi unit

Question 35

what is the single unit smooth muscle called?

Answer 35

visceral- most common type! - found in small arteries and veins, the stomach, intestines, uterus, urinary bladder

Question 36

in addition to responding to neural stimulus , smooth muscle also contracts or relaxes in presence of…

Answer 36

hormones, changes in ph, O2, CO2 levels, temperature and ion concentrations