Comparative Account of Nervous System of Vertebrates

Comparative Account of Nervous System of Vertebrates Dr. Poonam Rani Zoology Department B.Sc. Life Sciences 1 Year Room No. A-210, A-214 Main system of body, co-ordinate the other system of body. From lower chordates to higher chordates show the complexity. Structure built on same architectural plane, in accordance with the habit and behavior of animals. Definitionthe system which to perceive stimuli detected by the receptors to transmit these to various body parts, an to effect response to through effectors is called the nervous system. Function:1.Response to stimuli 2.Co-ordination 3.Learning. Types of Nervous System Central Peripheral Consist of brain and spinal cord 10 or 12 cranial and spinal nerves. Coordinate that impulses receives from receptor and transmit to effectors Provides connection between the receptor, CNS and effectors. Autonomic Innervates smooth, cardiac muscles and glands. Concerted with involuntary and automatic body activity. Development of Central Nervous System Histological Layers of Embryonic Neural Tubes Germinal -Consist actively deviding cells -Forms from connective tissue layer of neural tube. -Also called ependyma -Also proliferate in to mantal Mantal Consist of embryonic neurons or neuroblasts forming gray matter. Marginal -Consist of nerves fibers surrounded by fatty myelin sheath -Forms white matter. -Neurons and fibrers supported by neuroglia. General Structure of Brain  Structure built as same plane of all vertebrates.  Brain lies- within cranial cavity of skull, soft, white and somewhat flattened. VentriclesBrain is hallow from within, cavities of its various parts is called as ventricles. Cerebrospinal fluidVentricles filled with a lymph like fluid is called as cerebrospinal fluid. It is secreted by anterior and posterior choroid plexus. Meninges- Brain Covering of Three Memberans Duramater Arachnoid Piamater Inner membrane Middle layer Outer membrane Thin, soft, vascular Delicate and highly vascular Very tough Closely applied surface of brain Space Space Lies inner wall of cranium Subarchnoid Cavity Subdural cavity Histology of brain Cortex Outer part of brain and made by grey mater Consist nerve cells, nerve fibers, neuroglia and blood vessels Medulla The inner part of brain and made by white mater Consist of only nerve fibers and glial cells. rhinocoel paracoel iter metacoel Parts of brains 1.forebrain 2.midbrain 3.hindbrain Prosencephalon(forebrain) Olphactory lobe Cerebral hemisphere Diencephalon Antriormost, paired ,small cup shaped, separate each other. Paired separated by longitudinal median fissure. along with the telencephalon (cerebrum) Continous beneth the frontal lobe of cerebrum as paired olfactory lobes connect hipocample lobe. Narrow in front and broad in behind and smooth. Form 2/3 of brain and overlap to diancephalon. Main structures of the diencephalon include the hypothalamus, thalamus, epithalamus (including the pineal gland), and subthalamus. Cavity- frist venbtricalrhinocoel Function- sense of smell. Lateral sylvain fissure devides frontal and temporal lobe Ventrally rinal fissure devides from olfactory lobs shows hippocample lobe. Two hemisphere internally connect by band of nerve tissue called corpus collasum Ventrical- second-paracoel and two paracoel connect form foramen of monro. Function- though, memory, intellance, reasoing The diencephalon relays sensory information between brain regions and controls many autonomic functions of the peripheral nervous system. FunctionDirecting Sense Impulses Autonomic Function Control Endocrine Function Control Motor Function Control Homeostasis Touch Perception Dorsal view Median longitudinal fissure Olfactory tract Hippocampal lobe Rhinal fissure Olfactory lobes Frontal lobe of hemisphere Sylavin fissure Sylavian fissure Pinal body Temporal lobe corpora cordigima floccilus Corpus albicans flocculus vermis Medula oblangata Posterior choroid plexus Spinal cord Mesencephalon or midbrain  Small middle part of brain, lies below the cerebral hemisphere.  Dorsal surface has 4 rounded optic lobes called corpora cordigima.  The anterior two lobes called as superior colliculi and concer with     the slight. The posterior two lobes are smaller called inferior colliculi and associated with acute hearing. Cavity- narrow longitudinal passage-iter Its floor is thick fibres called crura cerebri, which link forebrain and hindbrain. Function- slight and acute hearing. Hindbrain or Rhombencephalon Cerebellum Very well developed and transverse elongated. Consist large median lobe called vermis and lateral lobe called as flocculus. No cavity surface is much folded to increase the grey matter. Surface folding forms elevation-gyri and groovessulci. Function- equilibrium and co-ordination of voluntory muscles. Prons Varolii Medula Oblongata Ventral surface of hindbrain has stout transverse bands of fibers Last part of brain Its connect right and left halves of the cerebrellum named prons varolli. Continous to spinal cord. Broad triangular anterior but taper in posterior Cavity- forth-metacoel The roof of metacoel is non-nervous and vascular called the posterior choroid plexus. Function- control the involuntary actions. Cephalic pigment sopot Frist cerebral nevve 1. Cephalochordata -without devide, like forebrain, midbrain and hind brain Second cerebral nevve -only consist of hallow dorsal nerve tube just above notochord. -no ganglia Anterior end slightly enlarge called brain and posterior end is spinal cord along the body. -neural tube has hallow central tube neurocoel filled with the CSF. Frist spinal nerve -Cerebral vesicles or brain consist of receptor organ pigment spot. 2. Cyclostoma Ex.Lampray diancephalon -brain is very primative, subdivision is not well marked, two olfactory lobes are prominent, cerebral hemisphere quite small. Habinulae ganglia Pineal apparatus and parapinal body is well developed but absent in myxin. -Connected to pinal apperatus is epithalamus made by two habinulae ganglia. -Optic lobs are imperfectly developed -Medulla oblongata well developed but cerebellum is small transverse band. -Well defined influndibulunm from hypothalamus of diencephalon bears a pituitary body. 3.Pises a. Elesmobranch Fish Ex. Scoliodon  Brain of fishes are more advanced than that of cyclostomes, shows subdivision.  In elasmobranches fishes the olfactory organs enlarged attached to cerebrum by short olfactory tract or peduncle.  Optic lobes are relatively mordate in size.  Midbrain cavity quite large and extend in to optic lobes. in pituitary attach small sensory organ called as saccus vasculosus.  Pinal body well developed.  Cerebellum is well developed because of the active swimming habitat.  To assist cerebellum in the maintaince of equilibrium.  Ruffle like restiform bodies are present at antero-lateral angle of medulla.  Bony fishes brain is more specialized than elasmobranches fishes.  In perch, olfactory lobes, cerebral hemisphere and diencephalon is smaller while optic lobes and cerebellum are larger.  Some bony fishes contain restiform bodies.  In bottom feeders anterior-lateral side of medulla oblongata shows unusual bulging called vagal lobs.  parapinal bodies are absent. 3. Amphibia Ex Frog  Smaller olfactory lobs and greater optic lobs indicate that greater reliance slight rather than smell.  Corpus striatum (floor of cerebrum) recives greater number of sensory fibers projected forward from thalamus than in fishes.  Cereral hemisphere are more denveloped for complex activity of locomotion, hibernation, breeding,etc.  Optic lobes are dominant in center.  Poor developed of cerebellum, a more transverse bands show relative decrease in muscular activity.  Medulla is small  Pinal body present. Reptilians Ex-lizzard •Shows advancement in size and porportion than that of amphibia because of the complete terrestrial mode of life. •Telencephalon increase the size and become largest part of brain. •Olfactory lobes connected to hemisphere and longer than amphibia. •There is greater thickness and enlargement in corpora striata. •Parapinal body more often callled the parietal eye is still found in some lizzard and sphenodon but is vestigeal or absent in other reptiles. •A pair of auditory lobes present in posterior to optic lobes. •Third ventrical is reduced. •Cerebellum is somewhat pear shaped and larger than amphibia. Lizzard Brain Olfactory bulb Olfactory peduncle Cerebral hemisphere Pinal body Optic chisma influndiblum Optic lobe Cerebellum hypophysis medulla Spinal cord Dorsal view Ventral view Birds Ex. Pigeon •Avian brain is larger than that of reptilians. •Olfactory lobes are smaller to poor sense of smell. •Hemisphere are larger smooth and project posterior over the diencephalon to meet cerebellum. •Third ventricle is narrow due to development of thalami. •Optic lobes are well developed in co-relation with keen slight but they are somewhat laterally displaced. •Cerebellum is greatly enlarged with several superficial folding, due to many activities involving muscular co-ordination and equilibrium such as flight and perching. Pigeon Brain Olfactory lobes Cerebral hemisphere Pinal body Optic lobe Optic chisma flocculus Optic tract vermis influndiblum hypophysis medulla Dorsal view Spinal cord Ventral view  Questions1. 2. 3. Give an account of comparative structure of nervous system of vertebrates. Write the functions of different parts of brain.