BIO-210 Exam 3 QUESTIONS
AND VERIFIED CORRECT
ANSWERS GRADED A+
Myosin binding site (muscle contraction and relaxation) - CORRECT ANSWER-
Myosin head (muscle contraction and relaxation) - CORRECT ANSWER-
Troponin (muscle contraction and relaxation) - CORRECT ANSWER-
Tropomyosin (muscle contraction and relaxation) - CORRECT ANSWER-
Calcium (muscle contraction and relaxation) - CORRECT ANSWER-
ATP (muscle contraction and relaxation) - CORRECT ANSWER-
ADP (muscle contraction and relaxation) - CORRECT ANSWER-
What happens to the sizes of the following bands/regions of sarcomere during contraction AND
relaxation?
a. Distance between Z-lines
b. I-band
c. A-band
d. H-zone
,e. length of actin and myosin filaments - CORRECT ANSWER-Z-lines: stays the same
I-band: narrow, shortens (contraction), maximum width (relaxation)
A-band: remains unchanged
H-zone: shortens (contraction), maximum width (relaxation)
Explain, in detail, the concept of a motor unit. How would the arrangement of a motor unit
differ for fine control vs. strength control? - CORRECT ANSWER-A motor unit is each
motor neuron and all the muscle fibers it innervates
Fine control uses small and few muscle fibers (ex. eye muscles)
Strength control: uses more fibers (recruitment)
Describe, in detail, all of the components of a neuromuscular junction (NMJ):
a. Synaptic knob
b. Junctional folds
c. synaptic cleft
d. basal lamina
e. acetylcholine
f. acetylcholine receptors
g. acetylcholinesterase - CORRECT ANSWER-a. Synaptic knob: swollen end of the nerve
fiber
b. Junctional folds: located on the sarcolemma, functions to increase surface area for
acetylcholine receptors and contains acetylcholinesterase to break down acetylcholine and relax
muscles
c. synaptic cleft: tiny gap between nerve and muscle cell; space for reactions to occur
d. basal lamina: thin layer of glycoprotein and collagen all over muscle fibers
e. acetylcholine (ACh): chemical component released from neuron to produce a stimulus
, f. acetylcholine receptors: sense ACh being released into synaptic gap and opens channels to
allow chemicals in for the muscle to contract
g. acetylcholinesterase: breaks down the ACh causing the muscle to relax
Briefly summarize the four actions necessary for muscle contraction and relaxation -
CORRECT ANSWER-1. Excitation: nerve action potentials lead to action potentials in
muscle fiber
2. Excitation-contraction coupling: action potentials on the sarcolemma activate myofilaments
3. Contraction: shortening of muscle fiber
4. Relaxation: return to resting length
Discuss HOW some of the neuromuscular toxins covered in class affect the NMJ. - CORRECT
ANSWER-Pesicides (cholinesterase inhibitors): bind to acetylcholinesterase and prevent it
from degrading ACh-spastic paralysis and possible suffocation)
Discuss HOW myasthenia gravis leads to progressive weakness. - CORRECT ANSWER-
autoimmune disease; antibodies attack NMJ and bind ACh receptors in clusters-become less
sensitive to ACh
Explain, in detail, why an individual becomes rigid soon after death, but then days later,
becomes floppy. Make sure to include the roles of ATP and calcium in your explanation. -
CORRECT ANSWER-Muscle cells have a massive release of Ca2+ from sarcolemma-
muscles contract and stiffen-become floppy bc there is no more ATP being produced to reset
the sarcolemma and proteins start breaking down
Explain the phenomenon of "all or none" when describing muscle contraction. - CORRECT
ANSWER-In order for contraction; muscle fibers must be stimulated or no contraction will
take place - muscle fibers fire one at a time
AND VERIFIED CORRECT
ANSWERS GRADED A+
Myosin binding site (muscle contraction and relaxation) - CORRECT ANSWER-
Myosin head (muscle contraction and relaxation) - CORRECT ANSWER-
Troponin (muscle contraction and relaxation) - CORRECT ANSWER-
Tropomyosin (muscle contraction and relaxation) - CORRECT ANSWER-
Calcium (muscle contraction and relaxation) - CORRECT ANSWER-
ATP (muscle contraction and relaxation) - CORRECT ANSWER-
ADP (muscle contraction and relaxation) - CORRECT ANSWER-
What happens to the sizes of the following bands/regions of sarcomere during contraction AND
relaxation?
a. Distance between Z-lines
b. I-band
c. A-band
d. H-zone
,e. length of actin and myosin filaments - CORRECT ANSWER-Z-lines: stays the same
I-band: narrow, shortens (contraction), maximum width (relaxation)
A-band: remains unchanged
H-zone: shortens (contraction), maximum width (relaxation)
Explain, in detail, the concept of a motor unit. How would the arrangement of a motor unit
differ for fine control vs. strength control? - CORRECT ANSWER-A motor unit is each
motor neuron and all the muscle fibers it innervates
Fine control uses small and few muscle fibers (ex. eye muscles)
Strength control: uses more fibers (recruitment)
Describe, in detail, all of the components of a neuromuscular junction (NMJ):
a. Synaptic knob
b. Junctional folds
c. synaptic cleft
d. basal lamina
e. acetylcholine
f. acetylcholine receptors
g. acetylcholinesterase - CORRECT ANSWER-a. Synaptic knob: swollen end of the nerve
fiber
b. Junctional folds: located on the sarcolemma, functions to increase surface area for
acetylcholine receptors and contains acetylcholinesterase to break down acetylcholine and relax
muscles
c. synaptic cleft: tiny gap between nerve and muscle cell; space for reactions to occur
d. basal lamina: thin layer of glycoprotein and collagen all over muscle fibers
e. acetylcholine (ACh): chemical component released from neuron to produce a stimulus
, f. acetylcholine receptors: sense ACh being released into synaptic gap and opens channels to
allow chemicals in for the muscle to contract
g. acetylcholinesterase: breaks down the ACh causing the muscle to relax
Briefly summarize the four actions necessary for muscle contraction and relaxation -
CORRECT ANSWER-1. Excitation: nerve action potentials lead to action potentials in
muscle fiber
2. Excitation-contraction coupling: action potentials on the sarcolemma activate myofilaments
3. Contraction: shortening of muscle fiber
4. Relaxation: return to resting length
Discuss HOW some of the neuromuscular toxins covered in class affect the NMJ. - CORRECT
ANSWER-Pesicides (cholinesterase inhibitors): bind to acetylcholinesterase and prevent it
from degrading ACh-spastic paralysis and possible suffocation)
Discuss HOW myasthenia gravis leads to progressive weakness. - CORRECT ANSWER-
autoimmune disease; antibodies attack NMJ and bind ACh receptors in clusters-become less
sensitive to ACh
Explain, in detail, why an individual becomes rigid soon after death, but then days later,
becomes floppy. Make sure to include the roles of ATP and calcium in your explanation. -
CORRECT ANSWER-Muscle cells have a massive release of Ca2+ from sarcolemma-
muscles contract and stiffen-become floppy bc there is no more ATP being produced to reset
the sarcolemma and proteins start breaking down
Explain the phenomenon of "all or none" when describing muscle contraction. - CORRECT
ANSWER-In order for contraction; muscle fibers must be stimulated or no contraction will
take place - muscle fibers fire one at a time
