Stimulus for Contraction

Question 1

impulse

Answer 1

a charged transmitted through certain tissue (cells) that results in the stimulation or inhibition of physiological activity

Question 2

action potential

Answer 2

electric impulse; impulse carried by a neuron

Question 3

membrane potential

Answer 3

measured by the electrical charge inside the cell to the charge outside the cell

Question 4

resting potential

Answer 4

result of the unequal distribution of positively (cation- outside of cell) and negatively (anion- inside of cell) charged particles called ions

Question 5

Channels

Answer 5

passive - always open

active - require chemical or electrical charge to open

Question 6

sodium-potassium pump

Answer 6

actively transports sodium out across the membrane and potassium back into the cell

-removes the 3 sodium ions from cell for each 2 potassium ions it bring to the cell

Question 7

polarized

Answer 7

resting cell

-at rest there is a net loss of positive ions from the interior of the cell, making the interior negatively charged with respect to the exterior

Question 8

depolarized

Answer 8

inside of the cell is positive relative to the outside

when a sufficient is applied to the cell, sodium channels open and positive ions flow into cell

Question 9

depolarization

Answer 9

reversal of membrane polarity that occurs during the production of action potential by the nerve and muscle cells

Question 10

repolarization

Answer 10

a return to the negative charge on the inside

• restores the cells resting potential so it can depolarize again
• sodium is returned to the outside of the cell and potassium to the inside by the sodium-potassium pump, which restores the balance of ions and resting membrane potential

Question 11

action potential

Answer 11

reverse polarity or change in electrical potential across a nerve membrane that generates an electrical current

Question 12

acetylcholine

Answer 12

synthesized in the cytoplasm of the neuron and stored in the vesicles at the distal end of the motor neuron fibers

Question 13

neurotransmitter

Answer 13

a chemical contained in synaptic vesicles in nerve endings that is released into the synaptic clef

Question 14

synapse

Answer 14

the junction between 2 neurons or a neuron and its effector muscle or gland

there is no actual physical union

Question 15

synaptic clef

Answer 15

the gap between 2 cells forming a synapse

Question 16

nerve impulse or muscle impulse

Answer 16

electrical signal that travels along an axon

Question 17

impulse passes

Answer 17

all directions over the surface of the muscle fiber membrane and travels through the transverse tubules deep into the fiber and reach the sarcoplasmic reticulum

Question 18

sarcoplasmic reticulum

Answer 18

membrane network of channels and tubules of a muscle fiber, corresponding the to the endoplasmic reticulum of other cells

-contains a high concentration of calcium ions

Question 19

end plate potentials

Answer 19

inward diffusion of sodium producing depolarization of the motor end plate

• graded in magnitude
• capable of summation

Question 20

cisternae

Answer 20

enlarged portions of the sarcoplasmic reticulum near the actin and myosin filaments of a muscle fiber

Question 21

2 events lead to muscle relaxation

Answer 21

1. Acetylcholine is decomposed by enzyme acetlycholinesterase
2. When acetylcholine breaks down, the stimulus to the muscle fiber ceases
   - as result, calcium ions are actively transported back into the sarcoplasmic reticulum, decreasing the calcium ion concentration of the sarcoplasm
   - linkage breaks, actin and myosin filaments slide apart, and muscle fiber relaxed

Question 22

acetlycholinesterase

Answer 22

prevents a single nerve impulse from continuously stimulating a muscle fiber

Question 23

dopamine

Answer 23

counteracts the effects of acetylcholine

- does not act at the neuromuscular junction; only in brain