Animals possess nerve networks or nervous systems to respond to their environment. But
the single celled Amoeba does not possesses any nerve cell, so, how it come to know
whether a particle it encounters is a grain of sand and not its dinner?

(1) By chemotaxis

(2) By skin

(3) By hormones

(4) All of these

Assertion   :       Circular smooth muscles of iris contract when bright light falls on the eye.

Reason      :       Pupil gets constricted by the contraction of circular smooth muscles of iris.

Assertion :      Tongue is a gustatoreceptor.

Reason    :       Receptors for gustatory sensations are located in the taste bund.

Assertion    :       All of the cranial nerves are said to be mixed nerves.

Reason      :       All cranial nerves carry both sensory and motor nerve fibres simultaneously.

Assertion   :       The chemical stored in the synaptic vesicles are termed as neurotransmitters.

Reason      :       Synaptic vesicles release these chemicals in the synaptic cleft.

Assertion    :       Nerve impulse can never be transmitted from dendrite or cell body of one neuron to the axon of the next neuron, across a synapse.

Reason      :       This happens because of the synaptic delay at each synapse.

Assertion   :       Nerve conduction is the one way conduction.

Reason      :       Nerve impulse is transmitted from dendrite terminals to axon terminals.

Assertion    :       After hearing a sound, nerve impulse passes from neurons to the brain.

Reason      :       The neurons which pass nerve impulses from the body organ to the brain is called afferent neuron.

Assertion   :       Cerebrospinal fluid is present throughout the central nervous system.

Reason      :       CSF has no such function.

Assertion  :       A person has lost most of its intelligence, memory and judgement.

Reason     :       A person has operated a tumour located in the cerebrum.