Unit 3 Flash Cards

Question 1

Three types of muscle

Answer 1

skeletal, cardiac, smooth

Question 2

6 functions of skeletal muscle

Answer 2

1) produce skeletal movement
2) maintain posture
3) support soft tissues
4) guard main entrances and exists
5) maintain body temp
6) store nutrient reserves

Question 3

Muscle Organizational Terms

Answer 3

Skeletal muscles are striated. Within the msucle you have a fassicle, which is a bundle of muscle fibers. Muscle fibers are individual muscle cells. Inside of those muscle cells you have myofibrils which contain sarcomeres. Those sarcomeres are whereyou have the thick and thin myofilaments

Question 4

Skeletal Muscle is what system?

Answer 4

SOMATIC nervous system because it’s voluntary movement

Question 5

Smooth muscle is what system?

Answer 5

AUTONOMIC nervous system because it’s involuntary

Question 6

sarcolemma

Answer 6

plasma membrane of the muscle fiber

Question 7

myofibril

Answer 7

shoots of proteins that house sarcomeres

Question 8

Sarcoplasmic Reticulum (SR)

Answer 8

stores and regulates calcium and their level and also releases/reabsorbs them very fast

Question 9

Transverse Tubules (T-tubules)

Answer 9

deals w/electrical signals, AP needs to tell the SR to release calcium so that the muscle can contract, shuts off when we want the muscle to relax

Question 10

Neuromuscular Junction (NMJ)

Answer 10

the first set of steps to control skeletal muscle activity

Question 11

Steps for neuromuscular junction

Answer 11

1) AP is generated
2) Ca2+ entry via neuron (axon terminal) which stimulates
3) release of acetylcholine (ACh) from vesicles (via exocytosis)
4) Binds to receptor
5) generates AP on sarcolemma
6) runs down T-tubules
7) contraction Occurs

Question 12

Excitation-Contraction Coupling

Answer 12

basically a component of neuromuscular junction

1) EXCITATION: AP runs down the T-tubules and at the triad, stimulates calcium release into the muscle cell

2) CONTRACTION: contraction occurs– as long as calcium ions stay in the sarcoplasm and are bound to troponin

Question 13

Steps to INITIATE Muscle Contraction

Answer 13

1) ACh is released: ACh is released at NMJ and binds to ACh receptors on the sarcolemma
2) AP reaches T-Tubule: an AP is generated and spreads across the membrane of the muscle fiber and along T-tubules
3) Sarcoplasmic Reticulum releases Ca2+
4) Active sites exposed and cross-bridges form: calcium ions bind to troponin, exposing active sites on the thin filaments. Cross bridges form when myosin heads bind to those active sites
5) Contraction cycle begins

Question 14

Contraction Cycle Summarized

Answer 14

1) contraction cycle begins
2) active-site exposure
3) cross-bridge formation
4) myosin head pivoting (power-stroke)
5) cross-bridge detachment
6) myosin reactivation

Question 15

Steps that END Muscle Contraction

Answer 15

1) ACh is broken down: it’s broken down by acteylocholinesterase (AChE), ending AP generation
2) Sarcoplasmic Reticulum reaborbs Ca2+
3) Active sites covered, and cross-bridge formation ends: without calcium ions, the tropomyosin returns to its normal position and active sites are covered again
4) muscle relaxation occurs

Question 16

Muscle Relaxation

Answer 16

1) contraction duration depends on: duration of neural stimulus, and number of free calcium ions in sarcoplasm
2) Ca2+ concentrations fall (it’s pumped back into SR)
3) Ca2+ detaches from troponin
4) active sites are re-covered by tropomyosin

Question 17

Muscle Excitation Events In order

Answer 17

1) ACh is bound to the synaptic cleft
2) Muscle Fiber depolarizes
3) calcium is released from SR
4) Calcium binds to troponin
5) sarcomeres shorten

Question 18

Statement about muscle contractions that is true:

Answer 18

sarcomere length changes during all types of contractions

Question 19

Isotonic Contraction

Answer 19

think skeletal muscles changing in length, there are two different subcategories: concentric, and eccentric contractions

example: holding a barbell before doing an arm curl

Question 20

Concentric Contractions

Answer 20

when muscle tension>load

example: pulling a barbell upwards in an arm curl

Question 21

Eccentric Contractions

Answer 21

when muscle tension<load

example: extending your arm during an arm curl

Question 22

ATP used by muscles comes from:

Answer 22

1) creatine phosphate
2) aerobic metabolism
3) glycolysis

Question 23

Fast muscle fiber

Answer 23

contracts really quickly, has a large diameter and large GLYCOGEN reserves, powerful contraction/fatigues very quickly, anaerobic metabolism

Question 24

Slow muscle fiber

Answer 24

slow to contract, high oxygen supply, primarily aerobic metabolism, has a small diameter w/more mitochondria, slow to fatigue, and contains myoglobin (protein that binds to oxygen)

Question 25

Hypertrophy

Answer 25

muscle growth from muscle training activity; increases: diameter of muscle fibers, number of myofibrils (and sarcomeres), also mitochondria and glycogen reserves

Question 26

Atrophy

Answer 26

lack of muscle activity– reduces muscle size, tone, and power

Question 27

Tension

Answer 27

when muscles cells contract, they pull on the attached tendon fibers, tension is the pull; it needs energy because it’s an active force

-muscle cells use energy to shorten and generate tension through interactions between thick and thin filaments
-tension production is based on individual muscle fibers

Question 28

Fiber Resting Length

Answer 28

the time of stimulation (length-tension) relationship
-the number of pivoting cross-bridges depends on: amount of overlap between thick and thin filaments
-optimum overlap produces GREATEST amount of tension
-normal sarcomere length is 75-130% to be optimal

Question 29

Frequency of Stimulation

Answer 29

a single neural stimulation produces: single contraction twitch (lasts 7-100 msc); sustained muscular contractions (may require repeated stimuli)

Question 30

Two factors that determine amount of tension produced by whole skeletal muscle:

Answer 30

1) fiber’s resting length (#of cross bridges)
2) frequency of stimulation (how often it receives AP): this is because it determines how much calcium is in the sarcoplasm

Question 31

Motor Unit

Answer 31

all muscle fibers have 1 single neuron attached to it, but one neuron can be attached to multiple muscle fibers, which is a motor neuron, part of a neuron unit

Question 32

Relationship between motor unit size and control

Answer 32

the size of the motor dictates how fine the control movement can be
-if you want PRECISE control then you want 4-6 muscle fibers (i.e. like the eye)
-if you want GENERAL control then you want 1,000-2,000 fibers (i.e. your leg)

Question 33

Myofilaments

Answer 33

contain 2 types of filaments: thin (actin), and thick (myosin)

Question 34

Thin filaments

Answer 34

1) Actin: active sites bind on actin strands to bind onto mysosin
2) Tropomyosin: prevents actin-myosin interaction
3) Troponin: binds tropomyosin to actin, controlled by Ca2+

Question 35

Epimysium

Answer 35

an exterior collagen layer, connected to deep fascia, and it separates muscle from surrounding tissue, surrounds skeletal muscle.

Question 36

Perimysium

Answer 36

surrounds muscle fibers (fascicles), contains blood vessels,

Question 37

At the level of the sarcomere..

Answer 37

1) what initiates cross-bridge formation: calcium goes from the SR –> the sarcoplasm through ion channels

2) What is preventing myosin from forming a cross-bridge w/actin: tropomyosin bc Ca2+ is bound to troponin

3) Why don’t thin filaments slide backwards when myosin heads detach from actin: there are other myosin heads attached to hold it in place

4) What two roles does ATP play in cross-bridge cycling: it provides energy for the pivot and it causes myosin to detach

5) What must first take place before cross-bridge cycling ends: calcium needs to be removed, uses primary active transport to go up it’s concentration gradient using ATP