Neural control and coordination – Multicellular animals have structurally complex body organization. Due to this, there arises a need to have a system for coordinating various metabolic and homeostatic activities of different parts, organs, organ systems in the body. This is achieved by nervous and endocrine systems present in the body. Both these systems jointly coordinate and integrate all such activities.
The photosensitive compounds (rhodopsin) in the human eye is composed of opsin (a protein) and retinal (an aldehyde of vitamin-A, i.e. retinol). They are present in the rod cell (Photoreceptors). Light induces dissociation of retinal from opsin thus changes the structure of opsin. This creates potential differences in the photoreceptors and they become hyperpolarised. However, during darkness rhodopsin is resynthesized from opsin and retinal to restore the dark vision and photoreceptors are depolarised (NEET-II 2016).
Destruction of the anterior horn cells of the spinal cord would result in loss of voluntary motor impulses. It is because the anterior horn cells (also called anterior grey column), which is the front column of grey matter in the spinal cord contains motor neurons that affect the axial muscles (CBSE AIPMT 2015).
Language comprehension includes the understanding of speech and written words. It requires an input of sensory information (from hearing and vision), processing of the information in different centers of the cerebral cortex and the coordination of motor output language comprehension is a function performed by the temporal lobe of the cerebrum (CBSE AIPMT 2015).
Vestibular apparatus of membranous labyrinth is an intricate series of interconnected and fluid-filled canals, which regulates balance and spatial orientation in the absence of vision. Thus, the movement of the body will be regulated only by vestibular apparatus. The otolith organs (utricle and saccule) regulate linear acceleration in various directions (CBSE AIPMT 2015).
The reflex arc is the arrangement of neurons in the pathway that always pass through the central nervous system.The axon of one neuron ends on the dendrites of next neuron. Such a junction is called synapse. Monosynaptic reflex arc has only two neurons, i.e. sensory and motor which forms one synapse (WBJEE 2013).
Adrenaline is equivalent to the neurotransmitter epinephrine as it is secreted in stress conditions in response to sympathetic stimulation and potentiates the conditions needed for fight or flight (OJEE 2013).
Epinephrine and norepinephrine are secreted by adrenal medulla (under the control of sympathetic nervous system) in response to the stress of any kind or during emergency situations. These are also called emergency hormones or hormones of flight, fight and fright (Triple F hormone) (CBSE AIPMT 2012).
The midbrain or mesencephalon consists of optic lobe and crura cerbri. In the frog, there are two optic lobes (corpora bigemina) which are hollow. In man, there are four solid optic lobes lying behind the diencephalon. They collectively constitute the corpora quadrigemina (AMU 2012).
The connecting passage between III ventricles (diocoel), IV ventricle and optocoels (cavities of optic lobes is called aqueduct of Sylvius) (WBJEE 2012).
Ca2+ is responsible for the release of neurotransmitter acetylcholine from axon terminal by rupturing the synaptic vesicle (WBJEE 2012).
There are two types of photoreceptor cells of the retina, namely rods and cones. The rods contain a purplish-red protein called the rhodopsin or visual purple, which contains a derivative of vitamin-A (CBSE AIPMT 2011).
Neurons are excitable cells because their membranes are in a polarized state. Different types of selectively permeable channels are present on the neural membrane. When a neuron is not conducting an impulse, i.e. resting, the axonal membrane is comparatively more permeable to potassium ion (K+) and nearly impermeable to sodium ion (Na+) (CBSE AIPMT 2011).
When a stimulus is applied, sodium-potassium pump stops operating. Sodium ions rush inside and potassium ions rush outside. This result in depolarization (action potential). After a period of the action potential, sodium-potassium pump operates (efflux of Na+ and influx of K+) and axon will get resting potential by repolarisation (UP CPMT 2011).
The nerve impulse is a wave of depolarization of the membrane of the nerve cell. The nerve impulse travels along a neuron or across a synapse. In the axon of motor nerve fiber, the nerve impulse travels away from the cell body (UP CPMT 2011).
The cerebrum is formed of one pair larges sized lobes called cerebral hemisphere. These form 80% weight of the brain. Cerebral hemisphere controls all the voluntary activities of the body. It is a seat of memory, will, intelligence, reasoning, and learning (MH CET 2011).
Jacobson’s organ is an auxiliary olfactory sense organ that is present in many animals. In mammals, the sensory neurons of Jacobson’s organ detect specific chemical compounds contained within scents that are often but not always, large non-volatile molecules. It is well-developed in snakes and lizards (WBJEE 2010).
There are ten laminae in the grey matter of spinal cord (WBJEE 2010).
The vestibular apparatus contributes to our balance and sense of special orientation. It is the sensory system that provides the dominant input about movement and equilibrium maintenance (UP CPMT 2010).
Sympathetic nervous system originates fro rami communicates of all thoracic and first three lumbar spinal nerves (AMU 2010).
The parasympathetic system is responsible for activating salivation (AMU 2010).