STD 11 - 18. Neural control and coordination — NEET STD 11 Science — Question

According to one of the most widely accepted theories the earth's atmosphere, before any life had originated on this planet, consisted of a mixture of

Assertion: Sickle-cell anaemia is caused due to change of one amino acid in ẞ-chain of haemoglobin.
Reason: It is a point mutation and occurs due to change of a single base pair in DNA.

The cerebral cortex is referred to as the grey matter due to its greyish appearance. The ........... are concentrated here giving the colour.

Normal activities of the heart are regulated intrinsically, i.e., auto regulated by specialised muscles (nodal tissue), hence the heart is called myogenic. Read following statement and choose correct option for right statements ?
(i) Mass of this tissue is seen in the lower left corner of the right atrium close to the atrio-ventricular septum called the sino-atrial node (SAN).
(ii) A bundle of nodal fibres, atrioventricular bundle (AV bundle) continues from the AVN which passes through the atrio ventricular septum is known as bundle of His.
(iii) Bundle of His immediately divides into a right and left bundle which form Purkinje fibres.
(iv) The nodal musculature has the ability to generate action potentials without any external stimuli, i.e., it is autoexcitable.
(v) The SAN can generate the maximum number of action potentials, i.e., 90-95 min.
(vi) Our heart normally beats 70-75 times in a minute (average 72 beats min).

Pressure gradient is determined by

Which of the following belongs to Phylum Arthropoda

Select incorrect sentence for down's syndrome

The law of segregation of characters is also called the law of purity of gametes because

Which option is correct for conduction of nerve impulse along chemical synapse ?
(i) At synapse the membranes of the pre and post- synaptic neurons are separated by a fluid-filled space called synaptic cleft.
(ii) Chemicals called neurotransmitters are involved in the transmission of impulses at these synapses.
(iii) The axon terminals contain vesicles filled with these neurotransmitters.
(iv) When an impulse arrives at the axon terminal, synaptic vesicles release their neurotransmitters in the synaptic cleft.
(v) The released neurotransmitters bind to their specific receptors, present on the pre-synaptic membrane.
(vi) Opens ion channels allowing the entry of ions which can generate a new potential in the post- synaptic neuron.
(vii) The new potential developed is only excitatory.