Practice free Zoology NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
Ca+2 bind ________ in the skeletal muscles and leads to exposure of the binding site for ________ on the filament _______:
Increase in Ca++ level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin.
(page-307)
ATP provides energy for muscle contraction by allowing for:
The myosin, releasing the ADP and P1 goes back to its relaxed state. A new ATP binds and the cross-bridge is broken. The ATP is again hydrolysed by the myosin head and the cycle of cross bridge formation and breakage is repeated causing further sliding. In this way, ATP provides energy for muscle contraction.
(page-307,308)
A motor unit is best described as:
A motor unit consists of one somatic efferent motor neuron and all of the muscle fibres that it innervates. Groups of motor units work together to coordinate the contractions of a single muscle.
(page-307)
Electrical excitation in a muscle fibre most directly causes:
A neural signal reaching this junction releases a neurotransmitter- acetylcholine which generates an action potential in the sarcolemma. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm from sarcoplasmic reticulum.
The energy for muscle contraction is most directly obtained from:
The energy for muscle contraction is directly utilised from ATP hydrolysis after which the myosin head binds to the exposed active sites on actin to form a cross bridge.
(page-307)
Put the following phrases in proper order to describe what occurs at the neuromuscular junction to trigger muscle contraction:
I. Receptor sites on sarcolemma.
II. Nerve impulse.
III. Release of Ca+2 from sarcoplasmic reticulum
IV. The neurotransmitter acetylcholine is released
V. Sarcomere shortern
VI. Synaptic cleft
VII. Spread of impulses over sarcolemma on T-tubules
II. Nerve impulse : Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron.
IV. A neural signal reaching this junction releases a neurotransmitter (Acetylcholine) which generates an action potential in the sarcolemma.
VI. Electrical signal reaches synaptic cleft which is converted to chemical signal to diffuse it to postsynaptic cell.
I. Receptor sites on sarcolemma receives the signal.
VII. This spreads through the muscle fibre.
III. This causes the release of calcium ions into the sarcoplasm.
V. Sarcomere shortens.
(page-307)
The muscle band that remains unchanged during muscle contraction and relaxation of the skeletal muscle is:
A-bands, the anisotropic bands of sarcomere which appears dark has constant length during muscle contraction.
The compound or pigment acting as an oxygen store in skeletal muscles is:
Muscle contains a red coloured oxygen storing pigment called myoglobin.
Myoglobin content is high in some of the muscles which gives a reddish
appearance. Such muscles are called the Red fibres. These muscles also
contain plenty of mitochondria which can utilise the large amount of
oxygen stored in them for ATP production.
(page-308)
How many bones make up the human skeleton?
In human beings, skeletal system is made up of 206 bones and a few cartilages. It is grouped into two principal divisions – the axial and the appendicular skeleton.
(page-309)
Number of bones in human axial skeleton is:
Axial skeleton comprises 80 bones distributed along the main axis of the body. The skull, vertebral column, sternum and ribs constitute axial skeleton.
(page-309)
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