Practice free Zoology NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
The globular head of the myosin filament has active site/s for binding to:
I. ATP
II. binding site for actin filament
III. Calcium
NCERT Page 306
Scapula is a large triangular flat bone situated in the dorsal part of the thorax between:
Page 311, XI NCERT
Scapula also called shoulder bladeis a thin, curve large triangular flat bone which extends on the backside of the thorax between second and the seventh ribs.
Which of the following is a hinge point?
Factual
The neurotransmitter released by the nerve cell at the neuromuscular junction is:
Page 307, XI NCERT
1. Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (and humans) as a neurotransmitter—a chemical message released by nerve cells to send signals to other cells, such as neurons, muscle cells, and gland cells.
The pivot joint between atlas and axis is a type of
(c) The joint between atlas and axis is a type of synovial joint. A considerable movement is allowed at all synovial joints. They are surrounded by tubular articular capsule. The capsule consists of two layers, i.e. outer fibrous capsule and inner synovial membrane, which secretes synovial fluid lubricates and providing nourishment to articular cartilage.
Concept enhancer
Fibrous joint They do not allow movement because the bones are held firmly by bundles of white fibrous tissue. e.g. joint between the bones of skull.
Cartilaginous joints They allow slight movement; because of the elastic pads of fibrocartilage present between the ends of the bones taking part in the joints, e.g. public symphysis of pubis.
Saddle joints This is the type of synovial joints. This type of joint is like ball and socket joint, but not developed fully, e.g. joint between carpal of hand.
Name the ion responsible for unmasking of active sites for myosin for cross-bridge activity during muscle contraction.
(a) : Ca++ icons bind with Tpc unit of troponin which is responsible for masking of active sites for myosin through tropomyosin. The event initiates cross-bridge activity during muscle contraction mechanism.
Lack of relaxation between successive stimuli in sustained muscle contraction is known as
(b) Sustained muscle contraction due to repeated stimulus is known as tetanus. This results due to muscle fatigue
Sliding filament theory can be best explained as
The sliding filament theory explains the mechanism of muscle contraction based on muscle proteins that slide past each other to generate movement.
According to the sliding filament theory, the myosin (thick) filaments of muscle fibers slide past the actin (thin) filaments during muscle contraction, while the two groups of filaments remain at relatively constant length.
The process by which most of the cartilaginous tissue is transformed into bones is
(a): Ossification is the formation of bone substance or conversion of other tissues to bone. It may be endochondral ossification and intermembraneous ossification. Endochondral ossification is the formation of bone in cartilage, as in formation of long bones. It involves the destruction and removal of cartilage and the formation of osseous tissue in space occupied by the cartilage. Intramembranous ossification is the formation of bone in or underneath a fibrous membrane.
If a stimulus, several times greater than the threshold stimulus is provided to a muscle fibre, it will
(c): A muscle fibre would contract only when it recieves stimulation of certain intensity called threshold stimulus. Response of a muscle fibre to a stimulus is not proportional to its intensity. It is absent when the intensity is subliminal. Muscle fibre contracts to the maximum whether the stimulus has threshold value or supraliminal value.
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