Select the incorrect statement regarding synapses. [2022]
The membranes of presynaptic and postsynaptic neurons are in close proximity in an electrical synapse.
Electrical current can flow directly from one neuron into the other across the electrical synapse.
Chemical synapses use neurotransmitters.
Impulse transmission across a chemical synapse is always faster than that across an electrical synapse.
(4)
Impulse transmission across an electrical synapse is always faster than that across chemical synapse.
Nissl’s bodies are mainly composed of [2018]
proteins and lipids
DNA and RNA
nucleic acids and SER
free ribosomes and RER
(4)
Nissl’s bodies, also known as Nissl’s granules are irregular masses of rough endoplasmic reticulum (RER) with numerous as well as free ribosomes and polysomes, found in cell body or cyton of a neuron. These probably synthesise proteins for the nerve cell.
Myelin sheath is produced by [2017]
astrocytes and Schwann cells
oligodendrocytes and osteoclasts
osteoclasts and astrocytes
Schwann cells and oligodendrocytes
(4)
Schwann cells and oligodendrocytes form myelin sheath around the axon. Myelin sheath serves as an insulating layer, preventing loss of energy of the nerve impulse during its passage along the fibre.
Receptor sites for neurotransmitters are present on [2017]
pre-synaptic membrane
tips of axons
post-synaptic membrane
membranes of synaptic vesicles
(3)
Neurotransmitter is a chemical substance responsible for transmission of nerve impulse across synapse. It is released by synaptic vesicle into the synaptic cleft. Neurotransmitter binds with protein receptor molecule present on post synaptic membrane causing its depolarisation and generation of action potential.
