The H-zone in the skeletal muscle fibre is due to
the central gap between actin filaments extending through myosin filaments in the A-band
extension of myosin filaments in the central portion ofthe A-band
the absence of myofibrils in the central portion of A-band
the central gap between myosin filaments in the A-band.
A.
the central gap between actin filaments extending through myosin filaments in the A-band
Each muscle fibre has many parallely arranged myofibrils. Each myofibril contains many serially arranged units called sarcomere which are the functiorial units. Each sarcomere has a central 'A' band made of thick myosin filaments, and two half 'T' bands made of thin actin filaments on either side of it marked by Z' lines. In a resting state, the edges of thin filaments on either side of the thick filaments partially overlap the free ends of the thick filaments leaving the central part of the thick filaments. This central part of thick filament, not overlapped by thin filaments is called the 'H' zone.
Assertion: On stimulation, a muscle cell releases calcium ions (Ca2+) from sarcoplasmic
reticulum.
Reason: By reacting with a protein complex, Ca uncover active sites on the actin filaments
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
Which one of the following is not a mammalian character?
Presence of milk producing glands
Skin is unique in possessing hair
Presence of external ears called pinnae
Homodont type of dentition
Which of the following pairs is correctly matched?
Cartilaginous joint - Skull bones
Hinge joint - Between vertebrae
Fibrous joint - Between phalanges
Gliding joint - Between zygapophyses of the successive vertebrae
An example of stretch reflex triggered by passive muscle movement is the
tendon reflex
ipsilateral reflex
flexor reflex
patellar reflex
The thin filaments of a muscle fibre are made up of
actin, troponin, tropomyosin
actin, troponin
myosin, troponin
actin, tropomyosin
Select the correct option regarding A, B and C.
A-Tropomyosin-runs close to F-actin throughout its length
B-Troponin-complex protein distributed at regular interval of tropomyosin
C-F actin-polymer of monomeric G-actin helically bound to each other
None of these
Which of the following is a transparent tissue
Tendon
Hyaline cartilage
Fibrous cartilage
All of these
Achondroplasia is a disease related with the defect in the formation of
membrane
cartilage
mucosa
none of these
