Structure Of human brain (Encephalon)it is soft, whitish. large sized and slightly flattened structure present inside cranial cavity of cranium of the skull. In man, it is about 1200-1400 gm in weight and has about 10,000 million . neurons. Brain is made up of 3 parts
Fore brain or Prosencephalon: It forms anterior two-third of brain and is formed of three parts
Olfactory lobes : These are one pair, small sized. club-shaped: solid: completely covered by cerebral hemisphere dorsally. Each is differentiated into two parts .
Olfactory bulb : Anterior, swollen part, and
Olfactory tract: Posterior and narrow part which ends in olfactory area of temporal lobe of cerebral hemisphere.
Function These control the smell.
(a) It is normal in frog, rabbit, and man..
(b) It is well developed in. So power of smell is more in dog.
(c) These are also well developed in dog fish and name dog fish is on the basis of well developed olfactory lobes.
The whole brain possess grey matter outside and white matter inside around ventricle.
(i) Grey matter: In cerebrum grey matter is very much developed, it is on an average 2-4 mm thick but at poles its thickness is 1.3 mm. It is thickest at pre central gyrus (4.5 mm thick). Grey matter of cerebrum is called cortex or pallium . Phyllogenetically or evolutionarily cortex is divided into 3 parts —
(a) Allocortex or paleocortex : It is the cortex of olfactory area of frontal lobe and olfactory bulbs. In lower vertebrates (cartilagenous fish) olfactory lobes occupy most of the part of cerebrum. So in these animals sense of olfection is very-very much developed. Sense of olfaction is oldest sense.
(b) Mesocortex : It is relatively not much older in development
(c) Neocortex or neopalliurm or neencephalon : It is most recent cortex and is developed maximum only in human. It is in prefrontal cortex or prefrontal region (organ of mind), precentraI and precentral gyrus etc. The neocortex is having 6 layer of neurons while remaining cortex possess only 5 layers.
The cerebral cortex is having area of about 2200 cm2 while the cranial cavity is only 1450 cm3, so to accomodate cerebrum there appears foldings in the cortex. The ridges are called gyrus (or gyri) or convolution while the depression are called sulcus (sulci in plural).
(ii)White matter: It is inner part of brain. White matter is aggregation of myelinated and unmyelinated axons of many neurons. Its fibres are divide into 3 categories :
(a) Commissural fibers : These neurons connect gyri of 2 hemispheres, such as corpus callosum. habenular commissure, anterior commissure, posterior commissure.
(b) Associate fibres : They connect gyri of same hernispnere.
(c) Projection neuron : They are infact, ascending and descending nerve tract, they connect one part of brain to another part of brain or to spinal cord. (In spinal cord they were called as columo)
Associated structures of cerebrum : Cerebrum has following specific structures.
Sub cortex : Nuclei on white matter. It is cluster of grey neurons in depth of white matter, they are formed in whole brain and are named differently.
Basal ganglia or central nucleus : These are several groups of nuclei in each cerebral hemisphere.
Corpus striatum :
Below corpus callosum there are two fused band of white neurons called fornix. There anterior part is called column and posterior part is called crura. Between column and genii a membrane is called septum lucidum or septum pallicidum. Septum lucidum encloses a space called V5 or Pseudocoel, because it is not possessing C.S.F. i.e. why it is called pseudocoel.
Limbic system : Limbic system present on inner border of cerebrum and floor of diencephalon. It is also called emotional brain or animal brain. Limbic system controlling emotion, animal behaviour like chewing, licking, sniffing, docility, tameness; affection (animals) rage, pain, pleasure, anger, sexual feelings, fear, sorrow grooming. It has following structure-
(a) Cingulate gyrus: It is a region of pre central gyrus
(b) Hippocampal gyrus : It is a region of temporal lobe near colossomarginal sulcus. These two structure are combinely called limbic lobe
(c) Amygdaioid body : It is the end of caudate nucleus.
(d) Olfactory bulb : They are on the inferior anterior surface of brain. Olfactory nerve ends in these bulb.
(e) Mammillary body : They are found in hypothalamus. Olfactory bulb and mammillary body both are centre of olfaction.
(I) Dentate gyrus ; Is in between hippocampus and parahippocampale.
(g) Anterior nucleus of thalamus is located in floor of lateral ventricle.
7.2 Diencephalon : Diencephalon cavity is called, Ill ventricle or diocoel the thin roof of this cavity is known as the epithalamus, the thick right and left sides as the thalami, and floor as the hypothalamus.
(I) Epithalamus :
it forms roof of third ventricle.
The epithalamus is not formed of nervous tissue.. It consists of piamater only Hence, it is of relatively little significance as a nerve centre. Its anterior part is vascular and folded. It is called anterior choroid plexus.
Behind this plexus, the epithalamus gives out a short stalk, the pineal stalk which bears a small, rounded body, the pineal body, at its tip, and paired right and left habemular nuclei (olfaction or smell).
(ii) Thalamus :
A pair of mass of grey matter forms the superior part of lateral walls of the third ventricle. It measures 3 cm in length and comprises 80% of diencephalon.
The thalamus is principal relay station for sensory impulses that reach the cerebral cortex from spinal cord, brain stem, cerebellum.
It also allows crude appreciation of some sensations such as pain, temperature, and pressure
Certain nuclei in the thalamus relay all sensory input to cerebral cortex. These include the - (a) Medial geniculate nucleus for hearing
Lateral geniculate nucleus for vision.
Ventral posteror nucleus for taste, touch, pressure, vibration, heat, cold, and pain.
Other nuclei are centers for synapse in somatic motor system their include.
(a) Ventral lateral nucleus and ventral anterior nucleus (voluntary motor actions).
(b) Anterior nucleus concerns with emotions and memory.
Hypothalamus
The hypothalamus is visible in the ventral view of the brain and forms the floor of diencephalon.
Hypothalamus also gives a nervous process called infundibulum (forms pars nervosa) which meets a rounded non-nervous pharyngeal outgrowth called hypophysis.
Both collectively form master gland called pituitary body.
A stalked outgrowth of infundibulum combines with a pouch-like epithelial outgrowth (Rathke's pouch) of the roof of embryonic mouth (= stomodaeum), forming a pituitary gland or hypophysis. Which secretes a number of hormones.
In front of hypothalamus, there is cross of two optic nerves called optic chiasma. Behind the hypothalamus, there is one pair of small, rounded, nipple-like bodies called mammilary bodies or corpora ma mammillares.
The hypothalamus consists of many masses of grey matter, called hypothalamic nuclei, scattered in the white matter.
In man and some other mammals, most fibres of optic nerves cross, but some fibres do not cross and innervate the eyes of their own respective sides.
This arrangement enables man and these mammals to have a binocular vision. Rabbits simply have a monocular vision.
Pineal gland is a pine cone-shaped grand.
It is located in the center of brain with which it loses all nerves connection after birth. It is innervated by sympathetic nerves.
It has a photosensory role in amphibian and primitive reptiles and is called 'Third eye'. Pinealocytes secretes melatonin
Mammalian pineal does not act as photoreceptor but it produces the hormone called melatonin which is anti FSH, and anti LH.
It inhibits reproductive function. Melatonin secretions decrease after puberty.
Functions of fore brain
Olfactory lobe : It is centre of smell.
Cerebrum : Cerebral cortex is made up of grey matter and differentiated into —
Sensory and associated area confirm, recognize and evaluate for shape, colour, sound, taste and smell for sensory cells in relation with object.
Broca's area : Known as sensory speech area or motor speech area. Translate thought into speech. Located into frontal lobe towards left side. It is associated with language area and also interpriate translation of written words into speech. Damage or injury in Broca's area (sensory or motor speech area) may result
Aphasia (inability to speak), Word deafness, Word blindness
Area Location Function
Premotor area Frontol lobe The highest centre for involuntary movements of Muscles and ANS
Motor area Frontal lobe Controls voluntary movement of specific the muscle
Broca’s area Frontal lobe Motor speech area(Translation of thought and written words into speech)
Somesthetic area Parietal lobe Perception of general sensation like pain, touch and temperature
Auditory area : Temporal lobe - Hearing (Interprets characteristics of sound such as pitch and rhythm.
Olfactory area : Temporal lobe -Sense of smell
Wernicke’s area : Temproral lobe - Understanding speech written and spoken
Gustatory area : Parietal lobe - Sense of taste
Visual area : Occipital lobe - Sensation of light
Cerebrum is a centre for — Intelligence, Emotion, Will power, Memory, Consciousness, Imagination, Experience, Knowledge, Reasoning, Voluntary controls. Weeping and laughing, Micturition, Defecation. lf cerebrum is removed animal becomes simple reflex animal
Diencephalon is a centre for:
(a) Carbohydrate metabolism
(b) Fat metabolism
(c) it relays impulses from posterior region of brain and also to posterior region of
brain
(d) Its secretes neurohormone
(e) From part of pituitary gland
(f) Secrete cerebrospinal fluid
Hypothalamus is a centre for — Hunger, Thirst, Sweating, Sleep, Fatigue, Temperature, Anger, Pleasure, love and hate,Satisfaction.
It is also centre to re!ease factors for endocrine glands
It also control A.N.S (automatic nervous system)
Centers for regulation of parasympathetic (cranio-sacral) activity. When stimulated, it causes slowing down of heart beat, contraction of the visceraL muscles.
The ventricles consist of four hollow fluid filled space inside the brain and same duct for connection between these ventricle
Olfactory lobe – Rhinocoel
Cerebrum – I and II ventricle or lateral ventricle or paracoel.
Foramen of monero : I and II ventricle communicating with III rd ventricle by foramen of monero. They are two in human and single in rabbit and frog
Diencephalon : Third ventricle or Diocoel.
Iter or cerebral aqueduct of aqueduct of Sylvius: It is very narrow cavity between III and IV ventricle.
Optic lobe : Optocoel
Cerebellum : Solid
Medulla oblongata : 4th ventricle or metacoel
Cavities of brain and spinal cord are modified neurocoel. They are lined by low columnar ciliated epithelium calledependyma
Fore brain or Prosencephalon: It forms anterior two-third of brain and is formed of three parts
Olfactory lobes : These are one pair, small sized. club-shaped: solid: completely covered by cerebral hemisphere dorsally. Each is differentiated into two parts .
Olfactory bulb : Anterior, swollen part, and
Olfactory tract: Posterior and narrow part which ends in olfactory area of temporal lobe of cerebral hemisphere.
Function These control the smell.
(a) It is normal in frog, rabbit, and man..
(b) It is well developed in. So power of smell is more in dog.
(c) These are also well developed in dog fish and name dog fish is on the basis of well developed olfactory lobes.
Cerebrum:
Cerebrum is divided into 5 lobes (a) frontal (b) parietal, (c) occipital, (d) temporal and (e) insula. A lobe called insula is hidden as it lies deep in the sylvian fissure.
The cerebral hemesphere are separated from olfactory robes by rhinal fissure.
The Median fissue divides the cerebrum into a right and 2 left cerebral hemisphere
A few sulci are well developed and form three deep and wide fisshres which divide each cerebral hemisphere into four lobes : anterior frontal lobe, middle parietal lobe, posterior occipital lobe and lateral temporal lobe e.g.
Fissure sulcus lying between the frontal and parietal lobes is central fissure or sulcus, that lying between the parietal and occipital lobes is parieto-occipital fissure and that demarcating frontal and parietal lobes from the temporal lobe is lateral or Sylvian fissure.
Each cerebral hemisphere is with fluid-filled cavity called lateral ventricle or paracoel.
Two cerebral hemispheres are interconnected by thick band of transverse nerve fibres of white matter called corpus callosum. The peripheral portion of each cerebral hemisphere is formed of grey matter and is called cerebral cortex, while deeper part is formed of white mailer and is called cerebral medulla, Cerebral. cortex is the highest centre for many sensations and activities and is with a number of sensory areas. Cerebral cortex 2-4 mm thick.
Two Cerebral hemispheres are interconnected by thick band of transverse nerve fibres of white matter called corpus callosum.
The peripheral portion of each cerebral hemisphere is formed of grey matter and is called cerebral cortex, while deeper part is formed of white matter and is called cerebral medulla
Cerebral cortex is the highest centre for many sensations and activities and is with a number of sensory areas. Cerebra cortex 2-4 mm thick.
The cerebral hemesphere are separated from olfactory robes by rhinal fissure.
The Median fissue divides the cerebrum into a right and 2 left cerebral hemisphere
A few sulci are well developed and form three deep and wide fisshres which divide each cerebral hemisphere into four lobes : anterior frontal lobe, middle parietal lobe, posterior occipital lobe and lateral temporal lobe e.g.
Fissure sulcus lying between the frontal and parietal lobes is central fissure or sulcus, that lying between the parietal and occipital lobes is parieto-occipital fissure and that demarcating frontal and parietal lobes from the temporal lobe is lateral or Sylvian fissure.
Each cerebral hemisphere is with fluid-filled cavity called lateral ventricle or paracoel.
Two cerebral hemispheres are interconnected by thick band of transverse nerve fibres of white matter called corpus callosum. The peripheral portion of each cerebral hemisphere is formed of grey matter and is called cerebral cortex, while deeper part is formed of white mailer and is called cerebral medulla, Cerebral. cortex is the highest centre for many sensations and activities and is with a number of sensory areas. Cerebral cortex 2-4 mm thick.
Two Cerebral hemispheres are interconnected by thick band of transverse nerve fibres of white matter called corpus callosum.
The peripheral portion of each cerebral hemisphere is formed of grey matter and is called cerebral cortex, while deeper part is formed of white matter and is called cerebral medulla
Cerebral cortex is the highest centre for many sensations and activities and is with a number of sensory areas. Cerebra cortex 2-4 mm thick.
The whole brain possess grey matter outside and white matter inside around ventricle.
(i) Grey matter: In cerebrum grey matter is very much developed, it is on an average 2-4 mm thick but at poles its thickness is 1.3 mm. It is thickest at pre central gyrus (4.5 mm thick). Grey matter of cerebrum is called cortex or pallium . Phyllogenetically or evolutionarily cortex is divided into 3 parts —
(a) Allocortex or paleocortex : It is the cortex of olfactory area of frontal lobe and olfactory bulbs. In lower vertebrates (cartilagenous fish) olfactory lobes occupy most of the part of cerebrum. So in these animals sense of olfection is very-very much developed. Sense of olfaction is oldest sense.
(b) Mesocortex : It is relatively not much older in development
(c) Neocortex or neopalliurm or neencephalon : It is most recent cortex and is developed maximum only in human. It is in prefrontal cortex or prefrontal region (organ of mind), precentraI and precentral gyrus etc. The neocortex is having 6 layer of neurons while remaining cortex possess only 5 layers.
The cerebral cortex is having area of about 2200 cm2 while the cranial cavity is only 1450 cm3, so to accomodate cerebrum there appears foldings in the cortex. The ridges are called gyrus (or gyri) or convolution while the depression are called sulcus (sulci in plural).
(ii)White matter: It is inner part of brain. White matter is aggregation of myelinated and unmyelinated axons of many neurons. Its fibres are divide into 3 categories :
(a) Commissural fibers : These neurons connect gyri of 2 hemispheres, such as corpus callosum. habenular commissure, anterior commissure, posterior commissure.
(b) Associate fibres : They connect gyri of same hernispnere.
(c) Projection neuron : They are infact, ascending and descending nerve tract, they connect one part of brain to another part of brain or to spinal cord. (In spinal cord they were called as columo)
Associated structures of cerebrum : Cerebrum has following specific structures.
Sub cortex : Nuclei on white matter. It is cluster of grey neurons in depth of white matter, they are formed in whole brain and are named differently.
Basal ganglia or central nucleus : These are several groups of nuclei in each cerebral hemisphere.
Corpus striatum :
Corpus striatum is the largest nucleus, consist of caudate nucleus and lenticular nucleus. The lentocular nucleus is sub-divided in putamen (outer shell) and globus pallidus (ball). Other structure, functionally linked to and some times considered part of basal ganglia are
(a) Claustrurn: It is the name given to grey matter present between insula and putamen.
(b) Epistriatum or Amygdaloid body : it is structure present at the end of caudate nucleus.
(c) Red nucleus and substantia nigra of mid brain.
(d) Sub thalamic nuclei of diencephalon.
Caudate and putame control large automatic movements of skeletal muscle like swinging of arm while walking.
Globus pailidus control muscle tone for specific body movements.
Corpus callosum : It is the band of white neurons present between both cerebral hemisphere and connect them on medial surface. It is present only mammal. it has anterior part genu, middle part trunchus and last part splenium.
(a) Claustrurn: It is the name given to grey matter present between insula and putamen.
(b) Epistriatum or Amygdaloid body : it is structure present at the end of caudate nucleus.
(c) Red nucleus and substantia nigra of mid brain.
(d) Sub thalamic nuclei of diencephalon.
Caudate and putame control large automatic movements of skeletal muscle like swinging of arm while walking.
Globus pailidus control muscle tone for specific body movements.
Corpus callosum : It is the band of white neurons present between both cerebral hemisphere and connect them on medial surface. It is present only mammal. it has anterior part genu, middle part trunchus and last part splenium.
Below corpus callosum there are two fused band of white neurons called fornix. There anterior part is called column and posterior part is called crura. Between column and genii a membrane is called septum lucidum or septum pallicidum. Septum lucidum encloses a space called V5 or Pseudocoel, because it is not possessing C.S.F. i.e. why it is called pseudocoel.
Limbic system : Limbic system present on inner border of cerebrum and floor of diencephalon. It is also called emotional brain or animal brain. Limbic system controlling emotion, animal behaviour like chewing, licking, sniffing, docility, tameness; affection (animals) rage, pain, pleasure, anger, sexual feelings, fear, sorrow grooming. It has following structure-
(a) Cingulate gyrus: It is a region of pre central gyrus
(b) Hippocampal gyrus : It is a region of temporal lobe near colossomarginal sulcus. These two structure are combinely called limbic lobe
(c) Amygdaioid body : It is the end of caudate nucleus.
(d) Olfactory bulb : They are on the inferior anterior surface of brain. Olfactory nerve ends in these bulb.
(e) Mammillary body : They are found in hypothalamus. Olfactory bulb and mammillary body both are centre of olfaction.
(I) Dentate gyrus ; Is in between hippocampus and parahippocampale.
(g) Anterior nucleus of thalamus is located in floor of lateral ventricle.
7.2 Diencephalon : Diencephalon cavity is called, Ill ventricle or diocoel the thin roof of this cavity is known as the epithalamus, the thick right and left sides as the thalami, and floor as the hypothalamus.
(I) Epithalamus :
it forms roof of third ventricle.
The epithalamus is not formed of nervous tissue.. It consists of piamater only Hence, it is of relatively little significance as a nerve centre. Its anterior part is vascular and folded. It is called anterior choroid plexus.
Behind this plexus, the epithalamus gives out a short stalk, the pineal stalk which bears a small, rounded body, the pineal body, at its tip, and paired right and left habemular nuclei (olfaction or smell).
(ii) Thalamus :
A pair of mass of grey matter forms the superior part of lateral walls of the third ventricle. It measures 3 cm in length and comprises 80% of diencephalon.
The thalamus is principal relay station for sensory impulses that reach the cerebral cortex from spinal cord, brain stem, cerebellum.
It also allows crude appreciation of some sensations such as pain, temperature, and pressure
Certain nuclei in the thalamus relay all sensory input to cerebral cortex. These include the - (a) Medial geniculate nucleus for hearing
Lateral geniculate nucleus for vision.
Ventral posteror nucleus for taste, touch, pressure, vibration, heat, cold, and pain.
Other nuclei are centers for synapse in somatic motor system their include.
(a) Ventral lateral nucleus and ventral anterior nucleus (voluntary motor actions).
(b) Anterior nucleus concerns with emotions and memory.
Hypothalamus
The hypothalamus is visible in the ventral view of the brain and forms the floor of diencephalon.
Hypothalamus also gives a nervous process called infundibulum (forms pars nervosa) which meets a rounded non-nervous pharyngeal outgrowth called hypophysis.
Both collectively form master gland called pituitary body.
A stalked outgrowth of infundibulum combines with a pouch-like epithelial outgrowth (Rathke's pouch) of the roof of embryonic mouth (= stomodaeum), forming a pituitary gland or hypophysis. Which secretes a number of hormones.
In front of hypothalamus, there is cross of two optic nerves called optic chiasma. Behind the hypothalamus, there is one pair of small, rounded, nipple-like bodies called mammilary bodies or corpora ma mammillares.
The hypothalamus consists of many masses of grey matter, called hypothalamic nuclei, scattered in the white matter.
In man and some other mammals, most fibres of optic nerves cross, but some fibres do not cross and innervate the eyes of their own respective sides.
This arrangement enables man and these mammals to have a binocular vision. Rabbits simply have a monocular vision.
Pineal gland is a pine cone-shaped grand.
It is located in the center of brain with which it loses all nerves connection after birth. It is innervated by sympathetic nerves.
It has a photosensory role in amphibian and primitive reptiles and is called 'Third eye'. Pinealocytes secretes melatonin
Mammalian pineal does not act as photoreceptor but it produces the hormone called melatonin which is anti FSH, and anti LH.
It inhibits reproductive function. Melatonin secretions decrease after puberty.
Functions of fore brain
Olfactory lobe : It is centre of smell.
Cerebrum : Cerebral cortex is made up of grey matter and differentiated into —
Sensory and associated area confirm, recognize and evaluate for shape, colour, sound, taste and smell for sensory cells in relation with object.
Broca's area : Known as sensory speech area or motor speech area. Translate thought into speech. Located into frontal lobe towards left side. It is associated with language area and also interpriate translation of written words into speech. Damage or injury in Broca's area (sensory or motor speech area) may result
Aphasia (inability to speak), Word deafness, Word blindness
Area Location Function
Premotor area Frontol lobe The highest centre for involuntary movements of Muscles and ANS
Motor area Frontal lobe Controls voluntary movement of specific the muscle
Broca’s area Frontal lobe Motor speech area(Translation of thought and written words into speech)
Somesthetic area Parietal lobe Perception of general sensation like pain, touch and temperature
Auditory area : Temporal lobe - Hearing (Interprets characteristics of sound such as pitch and rhythm.
Olfactory area : Temporal lobe -Sense of smell
Wernicke’s area : Temproral lobe - Understanding speech written and spoken
Gustatory area : Parietal lobe - Sense of taste
Visual area : Occipital lobe - Sensation of light
Cerebrum is a centre for — Intelligence, Emotion, Will power, Memory, Consciousness, Imagination, Experience, Knowledge, Reasoning, Voluntary controls. Weeping and laughing, Micturition, Defecation. lf cerebrum is removed animal becomes simple reflex animal
Diencephalon is a centre for:
(a) Carbohydrate metabolism
(b) Fat metabolism
(c) it relays impulses from posterior region of brain and also to posterior region of
brain
(d) Its secretes neurohormone
(e) From part of pituitary gland
(f) Secrete cerebrospinal fluid
Hypothalamus is a centre for — Hunger, Thirst, Sweating, Sleep, Fatigue, Temperature, Anger, Pleasure, love and hate,Satisfaction.
It is also centre to re!ease factors for endocrine glands
It also control A.N.S (automatic nervous system)
Centers for regulation of parasympathetic (cranio-sacral) activity. When stimulated, it causes slowing down of heart beat, contraction of the visceraL muscles.
Mid brain
The midbrain is located between the thalamus/hypothalamus of the forebrain. and pons of the hindbrain.
A canal called the cerebral aqueduct passess through the midbrain.
The dorsal portion of the midbrain consists mainly of four round swellings (lobes) called corpora quadrigemina.
Midbrain and hindbrain form the brain stem
it is formed of two parts —
(i) Optic lobes : These are one pair, large sized lobes present on dorsal side. Each is divided transversely into upper and larger superior coliculus and lower and smaller inferior coliculus. So there are four optic lobes, so colled optic quadrigemina (only in mammals) In frog these are known as bigemina. Valve of vieussens It joins the optic lobe with cerebellum.
(a) Superior optic lobe or superior colliculus: They are concerned with reflex action of eye, head and neck in response to visual stimulus.
(b) Inferior coIIicuIus: They are concerned with movement of head and trunk in response to hearing stimulus.
(ii) Cerebral peduncle (crura cerebri) They are the pair of thick bands of longitudinal nerve fiber present on the floor or ventral side of mid brain, The dorsal part of cerebral peduncle (white matter) is called Tagmentum while most ventral part (gray matter) is called crurra cerebrae or crus of cerebrum. Dorsal thick wall of mid brain is Known as optic tectum. Iter is between tegmentum ard tectum. Cerebral peduncle are infect possessing ascending and descending tracts, connecting upper and lower region of brain.
In white matter of cerebral peduncle these are following sub cortical structure.
(a) Red nucleus or rustrum nucleus : They are red because rich blood supply and iron containing pigment or haemoglobin. Function with basal ganglia and cerebellum to coordinate muscular movement.
(b) Substantia nigra: It. is black because of much deposition of melanin.
Occulomotor nucleus : It is origin point of 3rd cranial nerve (occulomotor) from this region 4th (Trochlear) nerve also originates
Functions of mid brain
Pair of anterior optic lobes (which are also known as superior colliculi) is related with vision
Pair of posterior optic lobe ( known as inferior colliculi) related with auditory
These act as coordination centres between hind and fore brain
A canal called the cerebral aqueduct passess through the midbrain.
The dorsal portion of the midbrain consists mainly of four round swellings (lobes) called corpora quadrigemina.
Midbrain and hindbrain form the brain stem
it is formed of two parts —
(i) Optic lobes : These are one pair, large sized lobes present on dorsal side. Each is divided transversely into upper and larger superior coliculus and lower and smaller inferior coliculus. So there are four optic lobes, so colled optic quadrigemina (only in mammals) In frog these are known as bigemina. Valve of vieussens It joins the optic lobe with cerebellum.
(a) Superior optic lobe or superior colliculus: They are concerned with reflex action of eye, head and neck in response to visual stimulus.
(b) Inferior coIIicuIus: They are concerned with movement of head and trunk in response to hearing stimulus.
(ii) Cerebral peduncle (crura cerebri) They are the pair of thick bands of longitudinal nerve fiber present on the floor or ventral side of mid brain, The dorsal part of cerebral peduncle (white matter) is called Tagmentum while most ventral part (gray matter) is called crurra cerebrae or crus of cerebrum. Dorsal thick wall of mid brain is Known as optic tectum. Iter is between tegmentum ard tectum. Cerebral peduncle are infect possessing ascending and descending tracts, connecting upper and lower region of brain.
In white matter of cerebral peduncle these are following sub cortical structure.
(a) Red nucleus or rustrum nucleus : They are red because rich blood supply and iron containing pigment or haemoglobin. Function with basal ganglia and cerebellum to coordinate muscular movement.
(b) Substantia nigra: It. is black because of much deposition of melanin.
Occulomotor nucleus : It is origin point of 3rd cranial nerve (occulomotor) from this region 4th (Trochlear) nerve also originates
Functions of mid brain
Pair of anterior optic lobes (which are also known as superior colliculi) is related with vision
Pair of posterior optic lobe ( known as inferior colliculi) related with auditory
These act as coordination centres between hind and fore brain
Hindbrain
The hindbrain comprises pons, cerebellum and medulla (also called the medulla oblongata). Pons consists of fibre tracts that interconnect different regions of the brain
Cerebellum has very convoluted surface in order to provide the additional space for many more neurons
The medulla of the brain is connected to the spinal cord. The medulla contains centres which control respiration, cardiovascular reflexes and gastric secretions
Cerebellum (Sabdwitched brain) : Cerebellum is second largest portion of brain lies posterior to medulla and pons and inferior to osterior portion of cerebrum. Cerebellum separated by cerebrum by a transverse fissure and by an extension o cranial dura matter called tentorium cerebella. Cerebellum is butter fly shape consists of a central constricted area is vermisA lateral wings or lobes called cerebellar hemispheres with anterior and posterior lobe (govern skeletal muscle movement)The flocculo nodular lobe (sense of equilibrium).
Between cerebellar hemisphere is extension of cranial dura meter called falx cerebelii. The superficial layer of cerebellum, called cerebellar cortex, consist of gray matter in series of parallel ridges called folia. Deep to gray matter are white matter free called 'Arbor vitae’ or tree of life. Cerebellum attached to brain stem by three paired cerebellar peduncles —
(i) Inferior cerebellar peduncle between cerebellum and medulla with sensory/motor fiber.
(ii) Middle cerebellar peduncle between cerebellum and pans with sensor axon.
(iii) Superior cerebellar peduncle between cerebellum and mid brain, mainly with major fiber. Cerebellum
Cerebellum has very convoluted surface in order to provide the additional space for many more neurons
The medulla of the brain is connected to the spinal cord. The medulla contains centres which control respiration, cardiovascular reflexes and gastric secretions
Cerebellum (Sabdwitched brain) : Cerebellum is second largest portion of brain lies posterior to medulla and pons and inferior to osterior portion of cerebrum. Cerebellum separated by cerebrum by a transverse fissure and by an extension o cranial dura matter called tentorium cerebella. Cerebellum is butter fly shape consists of a central constricted area is vermisA lateral wings or lobes called cerebellar hemispheres with anterior and posterior lobe (govern skeletal muscle movement)The flocculo nodular lobe (sense of equilibrium).
Between cerebellar hemisphere is extension of cranial dura meter called falx cerebelii. The superficial layer of cerebellum, called cerebellar cortex, consist of gray matter in series of parallel ridges called folia. Deep to gray matter are white matter free called 'Arbor vitae’ or tree of life. Cerebellum attached to brain stem by three paired cerebellar peduncles —
(i) Inferior cerebellar peduncle between cerebellum and medulla with sensory/motor fiber.
(ii) Middle cerebellar peduncle between cerebellum and pans with sensor axon.
(iii) Superior cerebellar peduncle between cerebellum and mid brain, mainly with major fiber. Cerebellum
receives sensory impulses from proprioceptors in muscle, joint, and tendons, coordinate skeletal muscle contractions and also regulate posture and balance.
Medulla oblongata Medulla oblongata is the hindest and posterior most part of brain. Cavity is known as IVth ventricle (metacoel). Which is continuous with central canal of spinal cord. It has a pair of lateral Foramina of Luschka and a median foramen magenide. Cerebrospinal fluid come in contact by these apertures from internal cavity of the brain to outer fluid of meninges. A arrangement on its ventral surface there are buldgings of ascending and descending tract which are called pyramids. On the ventral surface these pyramids cross each other which is called decussation of pyramids. On the dorsal side of medulla there are two nuclei which are called nucleus gracilis (long) and nucleus cuneatus. On floor of V4 there is groove called calamus scroptosious. In the medulla oblongata, most of the sensory and motor fibres cross from one side to the other. Thus, the left cerebral hemisphere controls the right side of the body and vice versa. The reason for this is not known. The lower end of medulla passes into the spinal cord. There is no demarcation between the two. However, the medulla is considered to start at the level of the foramen magnum of the cranium. Medulla contain nuclei of origin of 5 pairs of cranial nerves, VIII, IX, X, XI and XIl. VII vestioulocochiear nerve concerning with hearing and equilibrium. (There are also nuclei for vestibular branch of VIII in pons).
Pons Varolli :
Medulla oblongata Medulla oblongata is the hindest and posterior most part of brain. Cavity is known as IVth ventricle (metacoel). Which is continuous with central canal of spinal cord. It has a pair of lateral Foramina of Luschka and a median foramen magenide. Cerebrospinal fluid come in contact by these apertures from internal cavity of the brain to outer fluid of meninges. A arrangement on its ventral surface there are buldgings of ascending and descending tract which are called pyramids. On the ventral surface these pyramids cross each other which is called decussation of pyramids. On the dorsal side of medulla there are two nuclei which are called nucleus gracilis (long) and nucleus cuneatus. On floor of V4 there is groove called calamus scroptosious. In the medulla oblongata, most of the sensory and motor fibres cross from one side to the other. Thus, the left cerebral hemisphere controls the right side of the body and vice versa. The reason for this is not known. The lower end of medulla passes into the spinal cord. There is no demarcation between the two. However, the medulla is considered to start at the level of the foramen magnum of the cranium. Medulla contain nuclei of origin of 5 pairs of cranial nerves, VIII, IX, X, XI and XIl. VII vestioulocochiear nerve concerning with hearing and equilibrium. (There are also nuclei for vestibular branch of VIII in pons).
Pons Varolli :
An oval mass, of white mater called the pons varolli, lies above the medulla oblongata. It consists mainly of nerve fibres which interconnect as bridge connecting spinal cord with brain and parts of brain with each other. Pons also with pneumotexic area and apneustic area. Together with medullary rhythmicity area, they help control respiration.
Function of hind brain
Cerebellum -
Poorly developed in frog but well developed in mammal
It is centre for co-ordination of muscular rnov movement.
It is primary centre for balancing, equilibrium orientation.
Medulla oblongata contain centre for —
(i) Heart beats (ii) Respiration
(iii) Digestion (iv) Blood pressure
(v) Gut peristalsis (vi) Swallowing of food (
(vii) Secretion of gland
Involuntary function e.g. vomiting coughing vasoconstrictor, vasodilater, sneezing,
hiccouping.
(ix) It control urination, defecation.
(x) The cardiovascular center regulate rate, force of heart beats.
(xi) Medullary rhythmicity area — adjust basic rhythm of respiration.
Cavities or ventricles of the brainPoorly developed in frog but well developed in mammal
It is centre for co-ordination of muscular rnov movement.
It is primary centre for balancing, equilibrium orientation.
Medulla oblongata contain centre for —
(i) Heart beats (ii) Respiration
(iii) Digestion (iv) Blood pressure
(v) Gut peristalsis (vi) Swallowing of food (
(vii) Secretion of gland
Involuntary function e.g. vomiting coughing vasoconstrictor, vasodilater, sneezing,
hiccouping.
(ix) It control urination, defecation.
(x) The cardiovascular center regulate rate, force of heart beats.
(xi) Medullary rhythmicity area — adjust basic rhythm of respiration.
The ventricles consist of four hollow fluid filled space inside the brain and same duct for connection between these ventricle
Olfactory lobe – Rhinocoel
Cerebrum – I and II ventricle or lateral ventricle or paracoel.
Foramen of monero : I and II ventricle communicating with III rd ventricle by foramen of monero. They are two in human and single in rabbit and frog
Diencephalon : Third ventricle or Diocoel.
Iter or cerebral aqueduct of aqueduct of Sylvius: It is very narrow cavity between III and IV ventricle.
Optic lobe : Optocoel
Cerebellum : Solid
Medulla oblongata : 4th ventricle or metacoel
Cavities of brain and spinal cord are modified neurocoel. They are lined by low columnar ciliated epithelium calledependyma
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.