Nervous system-Key points for competitive exams

• Tela choroidea is the term used for epithalamus and piamater fused.
•  Tela choroidea is made up of epithelium and blood vessels.
• Ataxia mean tacks of muscle coordination. Damage to cerebellum is characterized by ataxia.
•  Dyslexia involves an inability of an individual to comprehend written language.
•  Multiple sclerosis is the destruction of myelin sheath of neurons of CNS.
•  An American scientist Roger Sperry got Nobel Prize in 1981 for his outstanding work on split brain theory.
•  Parkinson's disease or Paralysis agitans is a defect of brain.
•  Parkinsonism is characterised by tremors and progressive rigidity of limbs caused by a degeneration of brain neurons and a neurotransmitter called dopamine.
•  Avian brain has large sized optic lobes to see the objects on the earth while flying so is called eye brain, while fish brain has large sized olfactory lobes to smell the prey from a distance so is called nose brain.
•  In fishes : Cerebrum is not differentiated in two cerebral hemispheres.
•  Hypothalamus has additional lobes to note pressure changes.
•  In reptilian brain, pineal eye (parietal body) present in front of pineal body.
• In birds, instinctive behaviour is well developed so corpora striata are well developed.
• Grey matter of spinal cord of frog is rectangular while it is butterfly-shaped in mammals.
• Central canal : Cavity of spinal cord.
•  Optic bigemina : Two optic lobes in brain and are found from fishes to birds.
•  Optic lobes of man are solid and have no optocoel but those of frog have optocoel.
•  Optic tectum : Dorsal thick wall of optic lobe.
•  Cerebellum is also called little brain.
•  Thalami of diencephalon act as relay centres as well as gate keepers of brain.
•  Optic chiasma is meant for binocular vision.
• Olfactory lobes of human brain have no rhinocoel while those of frog have rhinocoel.
• Man and birds are less dependent upon smell so olfactory lobes are small sized but are large sized in cartilage fishes (dog fish), dogs and reptiles as are more dependent upon smell.
• Cerebellum is large sized in fishes, birds and rabbit due to their multidirectional movements and in-creased dependency on balance.
• Stimulus for hunger : In February 1998, an American scientist Dr. Masashi Yanagisawa reported that a drop of sugar level in blood stimulates the appetite centres of lateral hypothalamus to release oraxin hormone (Gr. Oraxis = hunger) which stimulates hunger.
• Nervous disorders
•         Agnosia     :     Failure to recognize;
•      Alexia     :     Failure to read;
•           Agraphia      :     Failure to write;
•       Aphasia      :      Failure to speak (due to injury to Broca's area)
•      Analgesia     :      Loss of sensation of pain;
•     Anesthesia     :        Loss of feeling;
•    Insomnia     :           Inability to sleep;
•    Amnesia      :     Partial or complete loss of memory;
•    Coma     :      Complete loss of consciousness.
•    Aproxia      :      Inability to carry out purposeful movements.
• Multiple sclerosis : Progressive degenerative disease of CNS and is characterized by many hard scar tissues.
•  Caudal equamma Bundle of roots in last segment of spinal cord.
•  Brain stem : Diencephalon + mid brain + pons + medulla oblongata.
•  Cerebra vascular accident (C.V.A) or stroke : Blocking of blood supply of a part of brain.
•  Alzheimer : It is the disease appearing usually after 65 year. It is characterized by dementia usually. Usually in this disease is ACH producing neurons of cerebral cortex and hippocampal lobe are degenerated. It is also seen that a amyloid protein is accumulated in the brain. It is the matter of research.
•  Comissure : The band of nerve fibers between two similar ganglia.
•  Connective : The band of nerve fibers between two different ganglia.
•  Associate fibres : If joining fiber are joining two similar structure in same halves then, they are called associate fiber.
• The rate of conduction in myelinated fibre of a mammal is very high because action potential jumps from node to node.
• The jumping of action potential from node to node (of Ranvier) in a fiber is called saltatory conduction.
• Nissl's or trigoid granules are present in the neuron and are made up of RNA, ribosome and RER. These granules help in excretion and nutrition.
•  Intelligence quotient (I.Q.) is the ratio of mental age to chronological age multiplied by 100.
•  Corpora striata, genu and splenium is found in cerebrum.
• Neurons stops dividing after birth.
• Optocoel is not found in mammalian brain.
•  The pneumotaxic centre is found in pons.
•  Transmission of nerve impulse can be recorded with the help of oscilloscope.
•  The ramus communicans of the spinal nerve joins the sympathetic chain.
•  Autonomous nervous system has paired chain ganglia.
•  Paralysis of jaw muscles is due to loss of function of Vth cranial nerve.
•  Bipolar nerve cell and ganglia cell are found in the retina.
•  Lateral funiculi have motor type of ganglia.
•  Six separate layers of neurons present in cerebral cortex.
•  Arbor vitae are composed of white matter.
•  IlIrd, lVth and VIth cranial nerves control eye-ball movement.
• A cavity in the ventricle of a brain is known as cerebral aqua.
•  VII, IX, X, XI and XlIth cranial nerve originating from medulla oblongata.
•  Cycling is an example of conditioned reflex.
•  The ganglia of sympathetic and central nervous system in frog develops from the neural crest cells.
• Cerebellum of post brain involved in loss of control when a person drinks alcohol.
•  The maximum current required to stimulate a nerve is called rheobase or threshold current or firing level of impulse. It is about 15 mv.
•  A fibres is the largest mammalian fiber.
•  Hyperpolarization of a dendrite is due to presynaptic inhibition.
• Amygaloid nucleus, hippocampus and fornix is the part of limbic system.
•  Posterioplegia is the paralysis of both lower limb due to damage of spinal cord.
•  Earthworm has both sensory and motor neurons.
•  The glial cells that form the blood brain barrier by lining brain capillaries are the            
•   astrocytes.
•  Axo-axentic is the condition when direction of nerve impulse is reversed.
•  Neurocyton is located in cortex of the brain.
•  Cervical swelling is the anterior enlargement of spinal cord.
•  Hydra has false nervous, system but not brain.
• Unipolar nerve cells are found in vertebrates embryo.
•  Saltatory conduction is found in all vertebrates.
•  In frog, the nerve impulses for hearing start from lagena basilaris.
• Corpus callosum is absent in the brain of prototherians and metatherians both.
•  Degeneration or imperfect development of corpus callosum in human brain results in a neurological disorder called schizophrenia.
• γ amino butyric acid is a neurotransmitter.
•  Acetylcholine is the cardiac inhibitor,
• 5-Hydroxy tryptamine is a chemical transmitter.
• Spike phase of action potential is 2 m. sec.
•  Sylvian fissure divides the brain of rabbit into frontal lobe and temporal lobe.
•  Dorsal root has the ganglion made of pseudounipolar neurons.
• All cell bodies of afferent fibres lie in the dorsal root ganglion.
•  EEG - Electro-Encephalogram:  Electrical tracing of the cerebral cortex is call EEG Berger in 1929 was first to record EEG. Instrument for the recording is Electroencephalograph or cathode ray oscilloscope.
•  It is record of brain wave. Brain waves are of following type
• (i) α—wave : These are rhythmic waves (8-13 cycles per second. These are produced in
•      normal awaking condition. These disappear in sleep.
• (ii) β—wave; 14-30 cycle per second. These are produced when nervous system is active   
•       e.g. Mental work             
• (iii) θ—wave: 5-8 cycle per second. Produced in children.
• (iv) δ—wave: 1-5 cycle per second. In normal condition these are produced in awake
•        infants. These are produced in deep sleep, in damage condition of the brain waves
•        may produce in awaking condition in adults.
• The sensation of sight in human brain is perceived by occipital lobe.
•  The sensation from skin one perceived in the cerebrum in parietal lobe.
•  Fundamental character of chordates is the presence of dorsal hollow nerve chord.
•  Somesthatic & taste area present in parietal lobe of cerebrum
•  Epilepsy : Is second common neurological disorder is characterized by short, recurrent, periodic attacks of motor, sensory, or psychological malfunction. The attacks called epileptic seizures are initiated by abnormal, synchronus electrical discharge from millions of Neurons in brain. Due to this, a person undergoing an attack may contract skeletal muscles involuntarily, light, noise, smells may be sensed when eyes, ears, nose have not been stimulated. Epilepsy has causes, including brain damage at birth (Most common cause), hypoglycemia, hypocalcemia, hyoxia, uremia, encephalitis, meningitis, and tumorn.
• Nystagmus —An uncontrolled oscillation of the eyes, is one of the symptoms of an inner-ear disease called Meniere's disease (from Prosper Meniere, French physician, 1799-1862).
•  Cones are absent in noctural animals like shrews, hedge hogs, rodents and bats.
•  During night the eyes of carnivores like cat, dog, lion, seal glow. It is due to tapetum lucidum a reflecting layer next to retina, which is made of crystaline layer with zinc, cysteine and guanin
•  Bees can see ultraviolet light.
•  The normal eye is known as emmetropic.
•  Deer has biggest eyes in proportion to body size.
•  Except rabbit and man, harderian glands are found in whale, mice, shrews and in reptiles.
• Nocturnal animals have more rods than cones in their eye. The image formed has no colour but is black or grey, the edges are not sharp.
• Colour blindness — It is known as daltonism. It is in between red and green colour. It is  genetic defect.
• Colour vision is due to presence of specialise cone cell in Retina which value the sensitivity for different pi)lours.
• Night blindness — During this rhodopsin is not resynthesized or regenerate in dim light.
• Monocular vision found in frog, rabbit and horse.
•  Binocular vision formed in primates, ape, monkey.
•  Colour vision found in fishes, reptiles, amphibia.
•  Sty Sebaceous gland infection leading to its inflamination.
• Iridian part of Retina — It is also thin and is like we composed only of a layer of    pigmented cells. It lies in contact with the iris.
• There are only four basic modalities of taste, which are sensed most acutely in particular regions of the tongue. These are sweet (tip of the tongue), sour (sides of the tongue), bitter (back of the tongue) and salty (over most of the tongue.)
• Iris is the third portion of the vascular tunic.
•  Atropine is a chemical used by doctors of dilate the pupil before testing.
•  Photopic vision is associated with cones
•  Cornea grafting : Cornea can be removed from a dead man's eys, stored and grafted on another persons's eye to restore vision, cornea transplantation is successful because it lacks blood vessels. Eye donation is a noble act.