Skeletal muscles

Question 1

Muscle

Answer 1

Made up of multiple fascicles

Question 2

Perimysium

Answer 2

Connective tissue surrounding individual fascicle

Question 3

Fascicle

Answer 3

Bundle of myofibers

Question 4

Endomysium

Answer 4

Delicate connective tissue around each myofiber

Question 5

Myofiber

Answer 5

multi nucleated muscle cells

Question 6

Sarcolemma

Answer 6

cell membrane of myofiber

Question 7

Myofibril

Answer 7

Chain of sarcomere

Question 8

Sarcomere

Answer 8

bundle of myofilaments (actin and myosin)

Question 9

Sarcomere organization

Answer 9

Sarcolemma
T-tubules: invagination of sarcolemma
Form triad with cisternae (enlarged area of sarcoplasmic reticulum)
2 triads per sarcomere

Question 10

Sarcomere banding

Answer 10

Z discs (Z lines): anchor actin filaments, located at end of sarcomere
I band: composed entirely of actin;width changes during contraction
A band: composed of actin and myosin; do not change width
H band: composed entirely of myosin; width changes during contraction, can disappear at maximum contraction
M lines: separated H bands

Question 11

Sliding filament mechanisms

Answer 11

make sure you go through the whole process from the nerve to the end

Question 12

Preload

Answer 12

Load in the relaxed state before muscle contracts

Question 13

Afterload

Answer 13

Load the muscle works against

Question 14

Types of tension

Answer 14

Passive: produced by preload
Active: produced by cross bridge cycling
Total: sum of active and passive tension

Question 15

Cross bridge cycling

Answer 15

Starts when free calcium is available and attaches to troponin
Contraction is the continuous cycle of cross bridge
ATP not required to form the cross bridge linking to actin
ATP required to break the link with actin
Continues until withdrawal of calcium ions or ATP depletion

Question 16

Energetics of muscle contraction

Answer 16

ATP required for:
-sliding filament mechanism
-pumping calcium ions from sarcoplasm back to SR
-Pumping of sodium, potassium ions through sarcolemma to reestablish resting potential
4 mmol—> maintain contraction for 1-2 seconds

Question 17

Energy for rephosphorylation

Answer 17

phosphocreatine releases energy rapidly and reconstitutes ATP
ATP+phosphocreatine provides energy for 5-8 seconds contraction
Glycolysis :lactic acid build up,sustain contraction for 1 minute
Oxidative metabolism (krebs cycle, ETC)
provide more than 95% of all energy needed for long term contraction

Question 18

Types of muscle contraction

Answer 18

Isometric: increase in tension but not length
Isotonic: change in length
Eccentric—>muscle lengthens
Concentric—> muscle shortens

Question 19

Epimysium

Answer 19

Connective tissue surrounding entire muscle

Question 20

Types of myofiber

Answer 20

Dark, slow fibers (red fibers)

Light, fast fibers (white fibers)

Question 21

Characteristic of fast ( white) fibers

Answer 21

Contract rapidly but less endurance
Fewer mitochondria
Use anaerobic respiration primarily
Little myoglobin
Large concentration of ATPase

Question 22

Characteristics of slow (red ) fibers

Answer 22

Contract slowly but more endurance
More mitochondria
Use aerobic respiration---> pyruvic and lactic acids build up
More myoglobin
Smaller concentration of ATPase

Question 23

What is a motor unit?

Answer 23

Neuron and myofibers it innervates form the motor unit

A neuron may innervate from a few o several hundred myofibers

Question 24

What is summation?

Answer 24

Additional spike adding to the effects of the previous spikes due to electrical events occurring faster than mechanical events which cause an increase in the total calcium ions in the cytosol and cycling cross-bridges—>Increases muscle tension

Question 25

What is tetany?

Answer 25

Muscle is at a maximum contraction due to the frequency of spikes so fast that there is no time for relaxation

Question 26

Muscle levers

Answer 26

bone muscle system is a machine involve 2 forces
In-force or effort Fi: Force applied to the machine
Out-force or resistance F0
In lever arm= distance from the in force to the fulcrum
Out lever arm= distance from the out force to the fulcrum

Question 27

Moments of bone muscle system

Answer 27

moment= force multiply by its lever arm
2 types
Mi= FiLi
Mo= FoLo
at equilibrium Mo=Mi

Question 28

Types of lever systems

Answer 28

First class: Fulcrum in the middle
in force and out force move in opposite direction
Second class: Resistance (out force) is in the middle
in force and out force are on the same side of the fulcrum
Third class: Effort (in force) is in the middle
in force and out force on the same side of the fulcrum and move in same direction