NEET Biology Solved Question Paper 2012

All or none law or Bowditch's law is a principle which states that response of a muscle nerve to a stimulus is not proportionate to the intensity of stimulus but is either present in full strength or completely absent. This law is applicable to single muscle fibre but entire muscle does not follow this law.

Coronary arteries are the blood vessels that supply the heart muscle (cardiac tissue) with blood rich in oxygen.

Coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the heart muscle. It carries less oxygenated blood to the right atrium as do the superior and inferior vena cavae.

Pulmonary veins are the veins that transfer oxygenated blood from the lungs to the heart. The largest pulmonary veins are the four main pulmonary veins, two from each lung that drain into the left atrium of the heart.

Enzymes or biocatalysts are exclusively proteinaceous substances capable of catalysing chemical reactions of biological systems without themselves undergoing any change. There are certain factors that affect enzymatic activity:

1. Temperature
2. pH
3. Enzyme concentration
4. Substrate concentration
5. Presence of inhibitors or activators

When living cells are placed in isotonic solution, they retain their shape and size as such because no osmotic movement of water molecules takes place.

If a plant cell is placed in hypertonic solution, the cell gets plasmolysed due to exosmosis. On the other hand, if a plasmolysed cell is placed in hypotonic solution, endosmosis occurs and the cell gets deplasmolysed.

The connecting passage between III ventricle (diocoel), IV ventricle and optocoels (cavities of optic lobes) is called aqueduct of sylvius. Foramen of Monro connects lateral ventricles with III ventricle or diocoel.

Vagus nerve is the tenth cranial nerve of mixed nature. It innervates to the chest, abdomen and heart.

Cohort is a formal taxonomic category in between infra- class and super- order in plant kingdom but not in animals.

Class $\to$Sub Class $\to$Infra Class $\to$Cohort $\to$Super Order $\to$Order

Numerical aperture is the multiple of refractive index of medium (n) and sine of angle subtended by optical axis and outer ray covered by objective (sin $\mathrm{\theta }$).

Numerical aperture (NA) = n sin $\mathrm{\theta }$

The complete cell cycle contains a sequence of phases which are

(a) Interphase which is further subdivided into G₁-phase or postmitotic gap, S-phase or synthesis phase and G₂-phase or premitotic gap respectively 

(b) Dividing phase or M-phase (mitotic or meiotic phase) which comprises karyokinesis and cytokinesis.

So, the correct sequence of phases in cell cycle is

G₁ $\to$S $\to$G₂ $\to$M

Man has 31 pairs of spinal nerves. These are

(a) Cervical 8 pairs in neck
(b) Thoracic- 12 pairs in thorax
(c) Lumbar- 5 pairs in upper part of abdomen
(d) Sacral 5 pairs in lower part of abdomen
(e) Coccygeal tail nerve.

Frog has 10 pairs of spinal nerves, while rabbit has 37 pairs of spinal nerves.