Human Brain: Functions, Parts and More
What is Human Brain?
The Human Brain is the most important organ in the human body. It controls and coordinates actions and reactions, allows us to think and feel, and enables us to have memories and feelings.
The highest coordinating centre in our body is brain(human brain) which is located inside the skull. Brain is protected by a bony structure in the skull called cranium. The three membranes called meninges surround the brain and protect it. The space between meninges is filled with a cerebro spinal fluid which helps the brain from mechanical shocks. Cranial nerves arise from the brain.
The highest coordinating centre in our body is brain(human brain) which is located inside the skull. Brain is protected by a bony structure in the skull called cranium. The three membranes called meninges surround the brain and protect it. The space between meninges is filled with a cerebro spinal fluid which helps the brain from mechanical shocks. Cranial nerves arise from the brain.
The brain is situated in the cranial cavity of skull.
It shape is oval and colour is light yellow or creamish yellow.
It weighs 1200-1400gms (98% of c.N.s) and has 100 billion neurons.
Matter
The brain is composed of outer grey matter and inner white matter in the areas of cerebrum, roof of midbrain and cerebellum.
In the rest, grey matter is inner and the olfactory lobes are made up of grey matter olfactory lobes are made up of grey matter only.
Meninges
The coverings of brain are called meninges. These are three in number. These menings are internally lined by squamous epithelium.
C.S.F. (Cerebrospinal fluid)
Choroid plexus is responsible to form
C.S.F.
It is formed 20 ml /hr mainly by choroid pie:jus and ependyma of ventricles. It is slightly alkaline and has specific gravity 1.005.
Direction of movement of C.S.F in brain is from anterior to posterior.
Parts of Human Brain
Brain is divided into three parts, fore brain, mid brain and hind brain.
The forebrain consists mainly of cerebrum, midbrain doesn't have any further division and hindbrain consists of pons, cerebellum and medulla.
The forebrain plays a central role in the processing of information related to complex cognitive activities, sensory and associative functions, and voluntary motor activities.
The structures in the forebrain include the cerebrum, thalamus, hypothalamus, pituitary gland, limbic system, and the olfactory bulb.
Cerebrum:
The cerebrum is the largest part of the human brain. It is responsible for our voluntary functions and processes information from our sense organs. In Human brain, it is the uppermost region of the Central Nervous System.
Thalamus:
The thalamus is a small structure within the brain located just above the brain stem between the cerebral cortex and the midbrain and has extensive nerve connections to both. The main function of the thalamus is to relay motor and sensory signals to the cerebral cortex.
The forebrain consists mainly of cerebrum, midbrain doesn't have any further division and hindbrain consists of pons, cerebellum and medulla.
Fore Brain
The prosencephalon or forebrain is the embryonic structure from which the cerebrum develops prenatally.The forebrain plays a central role in the processing of information related to complex cognitive activities, sensory and associative functions, and voluntary motor activities.
The structures in the forebrain include the cerebrum, thalamus, hypothalamus, pituitary gland, limbic system, and the olfactory bulb.
Cerebrum:
The cerebrum is the largest part of the human brain. It is responsible for our voluntary functions and processes information from our sense organs. In Human brain, it is the uppermost region of the Central Nervous System.
Thalamus:
The thalamus is a small structure within the brain located just above the brain stem between the cerebral cortex and the midbrain and has extensive nerve connections to both. The main function of the thalamus is to relay motor and sensory signals to the cerebral cortex.
Pituitary Gland:
The pituitary gland is a part of your endocrine system. Its main function is to secrete hormones into your bloodstream. These hormones can affect other organs and glands.Limbic System:
A network of ring-shaped structures around the corpus callosum and diencephalon (on both sides of the thalamus), perched on top of the brainstem, associated with emotion and behavior especially motivation, gratification, memory, and thought.
Olfactory Bulb:
Olfactory sensory neurons detect a large variety of odor molecules and send information through their axons to the olfactory bulb, the first site for the processing of olfactory information in the brain.
Mid Brain
The midbrain is also called the mesencephalon, is the smallest portion of the brain and is located just above the brain stem.
The midbrain is located in between the forebrain and hindbrain. It is underneath the cerebral cortex, just above the brain stem, and is located toward the center of the brain.
The midbrain is located in between the forebrain and hindbrain. It is underneath the cerebral cortex, just above the brain stem, and is located toward the center of the brain.
Midbrain functions:
Mesencephalon or the midbrain has many important functions, including controlling eye movements, motor movements, and visual and auditory processing. Moreover, this part of the brain is responsible for vision control, i.e. regulating responses to sight, pupil dilation, eye movement control, the process of hearing, as well as regulating movements of muscles.
The mesencephalon is a relatively small brain segment. However, its dysfunctions can lead to serious disorders, including Parkinson’s disease. Moreover, important studies in neuroscience and neurosurgery found that the head injuries do lead to mesencephalon damage.
Hind Brain
Hind Brain or Rhombencephalon1. Cerebellum or Metencephalon:
It is a small part which lies below the posterior part of cerebrum and above the medulla oblongata.
It has a median lobe called vermis and two lateral lobes called cerebellar hemispheres.
There are three Arbor vitae or tree of life (made of white matter) in the cerebellum, of which two are present in the two lateral lobes and one is present in the median lobe.
In cerebellum flask shaped cells are purkinjels cells.
It is surrounded by cerebral cortex.
2. Medulla oblongata or Myelencephalon
It is the lower most part of the hind brain and is conical in appearance.lts lumen is called metacoel or 4th ventricle. An oval mass pons varoli lies above medulla oblongata. It connects medulla to higher brain centres. It controls respiration.
Functions:-
(i) Cardiac centre
(ii) Respiratory centre.
(iii) Regulator of vasodilation and vasoconstriction.
(iv) Regulator of peristalsis and deglutination.
(v) Regulator of glandular secretion.
Some important facts
In brain glutamic acid metabolism is common
In latimeria brain's size is smallest in ratio of body size.
In man 500 ml C.S.F. per day is absorbed.
In Brain 750 ml. blood/ minute flows.
In brain's ventricle 125 ml C.S.F. is present out of total 150 ml.
Vausois s sphinctor connects optic lobes to cerebellum.
Barr body is present in the neurons in females.
After removing cerebral hemisphere death takes place.
Amnesia is a condition in which memory is lost partially or completely.
Loss of sensation is called anaesthesia.
Neuron protein is attached to the inner surface of brain.
Brain stem - medulla, pons varolli & mid brain collectively form brain stem. A diffuse network of nerve cells extend through it. It is reticular activating system (RAS)
Amygdala is found on the ventral surface of paracoel. It is related to recent and new memory.
Medulla oblongata comes out of foramen magnum in the form of spinal cord.
Spinal Cord
Spinal cord is concerned with the spinal reflexes and conducts nerve impulses to and from the brain.
It is a part of the CNS which is 45 cms long ( in women 43 cms) and weighs 35 gms.lt originates from lower part of medulla oblongata and is present on dorsal side in the neural canal of vertebral column up to 1 st lumbar vertebra.
It is long, cylindrical, convex dorsally and flat ventrally. Its last part is conical,
i.e. conus terminalis which in the end becomes thread like, i.e. filum terminalis.
It is having brachial and lumbosacral swelling at the point of origin of fore leg and hind leg.
Meninges
The same three meninges cover the spinal cord also. Similar to brain, epidural space is also present which is filled with fat and connective tissue.
Matter
In contrast to brain, grey matter is found on the inner side and white matter is found on the outer side.
C.S.F.
Direction of circulation of C.S.F is from posterior end to anterior end.
Structure
Spinal cord is hollow, its lumen is central canal or neurocoel filled with C.S.F. Canal is lined by ependyma of ependymal cells. Grey matter is butterfly or H-shaped.
There are three pairs of cornuae or horns .
(i) dorsal
(ii) ventral
(iii) lateral horns.
Dorsal, ventral and lateral funiculi lie close to the white matter area.
Dorsal horn forms dorsal arch while ventral horn forms ventral arch.
On dorsal side dorsal sulcus with septum is present and on ventral side ventral fissure is present.
Functions:- It conducts impulses to and from the brain and controls reflex action.
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