Structure and function of brain - class-X

The cerebellum is the convoluted subdivision of brain stem and is associated with coordination of muscular movement, muscle tone and balance. Medulla oblongata controls consciousness and arousal (the reticular formation) and its cardiovascular reflex centre controls heartbeat. The cerebrum is the largest and uppermost division of brain. It is the centre for higher thought processes required for learning, memory, language and speech. The correct answer is D.

The blood-brain barrier is a dynamic conduit for transport taking place between brain and blood. The blood vessels and brain are lined with endothelial cells that are wedged tightly together, creating a nearly impermeable boundary.

The nervous system of human comprises of Central Nervous System - comprises of brain and spinal cord. Peripheral Nervous System - comprises of nerves present between brain and body parts.

The brain serves as the center of the nervous system in all vertebrates and most invertebrate animals. Only a few invertebrates, such as sponges,  jellyfish, adult sea squirts and starfish do not have a brain.In such organisms, a diffuse neural tissue is present. It is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste and smell. The brain is the most complex organ in a vertebrate's body. 

Ependymal cells are the cube-shaped epithelial cells that forms the epithelial lining of the cavities in brain and central canal of spinal cord. These cells are formed from a layer of embryonic tissue known as neuroectoderm and secrete cerebrospinal fluid for mechanical protection.

Meninges are the membranes that envelop the brain and spinal cord of the central nervous system. 

The spinal cord is a part of the central nervous system. The most important structure between our body and our brain is the spinal cord. It extends from the foramen magnum, where it is continuous with the medulla to the level of the first or second lumbar vertebrae. It is a vital link not only from the brain to the body but also from the body to the brain. The spinal cord is 40 to 50 cm long and 1 cm to 1.5 cm in diameter. 

• The central nervous system (CNS) is the processing center for the nervous system. The two main organs of the CNS are the brain and spinal cord. The brain processes and interprets the sensory information sent from the spinal cord. Both the brain and spinal cord are protected by three layers of connective tissue, called meninges.
• Within the central nervous system is a system of hollow cavities, called 'ventricles'. The network of linked cavities in the brain (cerebral ventricles) is continuous with the central canal of the spinal cord. The ventricles are filled with cerebrospinal fluid, which is produced by specialized epithelium located within the ventricles, called the choroid plexus. 
• Cerebrospinal fluid surrounds, cushions and protects the brain and spinal cord from trauma. It also assists in the circulation of nutrients to the brain.

The bony structure in the head of most vertebrates (in particular, craniates) that supports the structures of the face is called as the skull. It forms a protective cavity for the brain. The cranium and the mandible are the two parts of the skull. The skull forms the anterior most portion of the skeleton and is a product of encephalization, housing the brain, many sensory structures (eyes, ears, nasal cavity) and the feeding system.

The brain is the control center of the body. It consists of three main components- forebrain, brainstem, hindbrain. The brain is important in the human body, because it allows a person to think, feel and store memories, and it controls and coordinates the body's actions and reactions. The brain is an incredibly complex organ composed of many parts, including the cranium, the cerebrum, the brain stem and the cerebellum.

Main function of central nervous system (brain and spinal cord) is to integrate the sensory inputs from internal and external environment as received by sensory neurons and process and finally transmit the nerve impulses to effectors (muscles and glands). Thus, being the centre of processing information, the brain has the maximum number of cell bodies of neurons (the grey matter). Spinal cord provides means of communication between peripheral nerves and brain. Thus, it has H-shaped grey matter (cell bodies of neurons) and white matter else everywhere (the myelinated axons that carry impulses to and from the brain). Since nerves in retina and tongue serve to conduct information along the sensory pathways; they have single axon with highly branched dendrites but no cell bodies. Thus, the correct answer is option A.

• The brain and spinal cord are the two major parts of the CNS. The brain forms the largest portion of the CNS. 
• The brain resembles a cream-colored rope made up of nerves that that relay messages.
• The spinal cord stretches from the medulla oblongata at the base of the brain to the lower back and is housed in a tunnel made by the vertebrae bones of the spinal column. 
• The spinal cord works a bit like a telephone switchboard operator, helping the brain communicate with different parts of the body and vice versa. 

• A deep furrow divides the cerebrum into two halves, known as the left and right hemispheres. 
• The two hemispheres look mostly symmetrical yet it has been shown that each side functions slightly different than the other. 
• Sometimes, the right hemisphere is associated with creativity and the left hemispheres are associated with logic abilities. 
• The corpus callosum is a bundle of axons that connects these two hemispheres. 

• The thalamus is a part of the human brain situated between the cerebral cortex and midbrain. It has a number of functions. 
• Some of its functions include the relaying of the sensory and motor functions to the cerebral cortex. It processes the sensory information as well as relay it. 

• Underneath the limbic system in the brain stem. This structure is responsible for life functions such as breathing, blood pressure, etc.
•  Scientists say that this is the "simplest" part of human brains because animals' entire brains (such as reptiles) resemble our brain stem. 
• The brain stem is made of the midbrain, pons, and medulla. 

• The brain has three divisions, i.e., forebrain, midbrain, and hindbrain. The forebrain consists of the cerebrum, thalamus, and hypothalamus. 
• The midbrain has decreased in size during vertebrate evolution and the forebrain has gradually acquired much of its function, while the hindbrain consists of medulla, cerebellum and the pons. 

Three layers of protective tissue that surround the brain and spinal cord are called meninges. These three layers are dura mater, arachnoid mater, and pia mater.

The nervous system, including the brain, is derived from the ectoderm layer during embryonic development. This is a fundamental concept in embryology.

• Superior colliculi is a part of the midbrain. There are paired structures that are responsible for controlling eye movement. 
• There are one colliculi in each side of the brain which is responsible for creating a map of the visible area. 
• The fixation of the vision and the tracking of any object is controlled and regulated by this region of the brain. 

The membrane which covers the brain and the spinal cord is called as the meninges. There are three layers of the meninges. The outermost is the Dura mater, middle one is the arachnoid mater and the innermost is the pia mater. Dura mater is the tough membrane which is present in the outermost region. The three meninges provide protection to the brain from shock and injury. 

White matter is a component of the central nervous system, in the brain and spinal cord. The white matter is placed on the grey matter in the brain while it lies outer to the grey matter in the spinal chord. It consists mostly of glial cells and myelinated axons that transmit signals from one region of the cerebrum to another and between the cerebrum and lower brain centres.

A normal human brain weighs on average about 1.5 kg (3.3 lb) with a volume of around 1130 cubic centimetres ($cm^3$) in women and 1260 $cm^3$ in men.

Afferent (sensory) nerve fibers carry impulses from sensory receptors toward the central nervous system. Efferent (motor) fibers carry impulses away from the CNS to effectors.

The human cranium consists of 8 bones: frontal (1), parietal (2), temporal (2), occipital (1), sphenoid (1), and ethmoid (1). This totals 8 bones with two pairs (parietal and temporal).

The meninges from the outermost to the innermost layer are the dura mater, the arachnoid mater, and the pia mater. This sequence provides protection to the brain.

The lateral ventricles are connected to the third ventricle via the interventricular foramen (foramen of Monro). Since this is not listed in the options, 'None of the above' is the correct choice.

The ventricles of the brain are lined by a specialized epithelial tissue called ependyma, which is involved in the production and circulation of cerebrospinal fluid.

Human brain growth is rapid in early childhood, reaching approximately 90% of its adult size by age 6. While development continues, the physical size is largely attained by this age.

The human skeleton is the internal framework of the body. It is composed of around 270 bones at birth – this total decreases to around 206 bones by adulthood after some bones get fused together. 

So, the correct option is ‘Skull’.

Different regions of the brain are responsible for specific functions. For example, the medulla oblongata is responsible for regulating heart beat and many other involuntary actions. The Broca region is responsible for speech and language etc. So, the correct answer is option A.

Retina forms the innermost layer of eyeball and mainly contains rods and cones, the photoreceptors, along with nerve fibres. 

Brain cells remain in the beginning stage of interphase of cell reproduction for their life, and never divide, and instead develop by forming new synapses with other neurons. They lack cellular machinery for cell division. So, the correct answer is option A. 

Brain cells are extremely sensitive to a lack of oxygen. Some brain cells start dying less than 5 minutes after their oxygen supply disappears. As a result, brain hypoxia can rapidly cause severe brain damage or death. 

• The limbic system often referred to as the "emotional brain", is found buried within the cerebrum. 
• Like the cerebellum, evolutionarily the structure is rather old. This system contains the thalamus, hypothalamus, amygdala, and hippocampus. 

The cerebrum or cortex is the largest part of the human brain, associated with higher brain function such as thought and action. The cerebral cortex is divided into four sections, called "lobes". The frontal lobe, parietal lobe, occipital lobe, and temporal lobe. 

• Hippocampus is the portion of the cerebral hemispheres in basal medial part of the temporal lobe. 
• This part of the brain is important for learning and memory, for converting short term memory to more permanent memory and for recalling spatial relationships in the world about us. 

• Amygdala is a part of the telencephalon, located in the temporal lobe, involved in memory, emotion, and fear. 
• The amygdala is both large and just beneath the surface of the front, medial part of the temporal lobe where it causes the bulge on the surface called the uncus. 
• This is a component of the limbic system. 

• Pons is a part of the metencephalon in the hindbrain. It is involved in motor control and sensory analysis. 
• For example, information from the ear first enters the brain in the pons. It has parts that are important for the level of consciousness and for sleep. 
• Some structures within the pons are linked to the cerebellum, thus are involved in movement. 

The meninges are the layers that are closely present around the brain. The dura mater is an outermost tough and fibrous layer. It closely lines the cranium. It is followed by the arachnoid mater that forms the middle meninx. The piamater is the innermost meninx which adheres closely to the surface of the brain. It is highly vascular due to the rich supply of the blood vessels. So, it provides oxygen and nutrients to the cells of the brain. 

The meninges are the layers that are closely present around the brain. The dura mater is an outermost tough and fibrous layer. It is followed by the arachnoid mater that forms the middle meninx. The piamater is the innermost meninx which adheres closely to the surface of the brain. It is highly vascular due to the rich supply of the blood vessels. So, it provides oxygen and nutrients to the cells of the brain.