The third ventricle is one of four connected fluid-filled cavities comprising the ventricular system within the mammalian brain. It is a median cleft in the diencephalon between the two thalami and is filled with cerebrospinal fluid (CSF). It is in the midline, between the left and right lateral ventricles.

Frontal lobe of cerebrum of brain is responsible for thinking, evaluation of information, judgement, decision making, and planning and response organization i.e. intellectual processes. The cardiovascular reflex center of medulla oblongata regulates the rate and force of heat beat. The thermoregulation centre is present in hypothalamus which maintains the constant human body temperature by regulation of the diameter of blood vessels (constriction or dilation), shivering and sweating mechanism. Thus, correct answer is D.

The mesencephalon is also called the midbrain. It is a small and reduced part of the brain which connects the forebrain with the brainstem. Its anterior part consists of two longitudinal myelinated nerve fibres called the cerebral peduncles or crus cerebrum or the crura cerebri. The posterior part is made of four colliculi that are called the corpora quadrigemina.

Brainstem connects the cerebrum to the spinal cord. It consists of the midbrain (mesencephelon), medulla oblongata and the pons (parts of the hind brain). It relays information between the cerebrum and the spinal cord.

The medulla oblongata is a cone shaped neuronal mass in the hindbrain which connects higher level of both brain and spinal cord. It serves in several functions of the autonomous nervous system (ANS) such as involuntary actions like heart rate, breathing, swallowing, sneezing and digestion by the sympathetic and parasympathetic response. 

Cerebrum is a part of forebrain and makes up about two third of the human brain, and consists of two cerebral hemispheres joined by a curved thick band of nerve fibres called corpus callosum whereas cerebellum is a part of hindbrain and is only 1/8th the size of the cerebrum and lies under occipital lobe, dorsal to brain stem.

It's a lot smaller than the cerebrum at only 1/8 of its size It controls balance or equilibrium of the body.

The brain stem controls the flow of messages between the brain and the rest of the body, and it also controls basic body functions such as breathing, swallowing, heart rate etc... The brainstem is divided into three sections in humans: the midbrain (mesencephalon) which governs rudimentary vision and hearing, pons varolii (metencephalon) which links the cerebellum to the cerebrum and the medulla oblongata (myelencephalon) which controls breathing, swallowing, blood pressure, and heart rate.

Broca's area is the motor speech area and Wernicke's area plays role in understanding speech and writing words.

Forebrain consists of two regions; namely cerebrum and diencephalon. A deep cleft divides the cerebrum longitudinally into two halves, which are termed as the left and right cerebral hemispheres. Each cerebral hemisphere is divided into four lobes, viz., frontal lobe, parietal lobe, occipital lobe and temporal lobe. The frontal lobe is associated with intelligence, memory, judgment, problem-solving ability and controls voluntary activities. The parietal lobe is associated with the sense of touch, temperature, pressure, and pain. The temporal lobe is associated with the sense of taste, hearing, and smell. The occipital lobe is associated with sight.

Piameter is the innermost membrane of the brain and arachnoid is the middle membrane. The space between arachnoid and piameter is caleed sub-arachnoid space. This space is filled with cerebrospinal fluid.

Pneumotaxic centre is present in the dorsal part of the pons varolii of the brain. Its function is primarily to limit inspiration.

Cerebrum is the main site of intelligence and consciousness in the body of the organism. The hypothalamus is the area of brain that is important in controlling the balance of bodily functions. It controls the release of hormones from the pituitary gland. The midbrain is responsible for controlling the vision and hearing features of the organism. Medulla oblongata is responsible for controlling the rate of the heart beat.

• Homeostasis is maintained by the action of various hormones and organs of the body
• Cerebrum is the centre of thought, intelligence etc
• Cerebellum Coordinates muscular activities
• The thalamus relays impulses

The cerebrum is that part of the brain that contains the two cerebral hemispheres and the subcortical structures and hippocampus, basal ganglia and olfactory bulbs. In most vertebrae, the neural tube of the embryo is subdivided to form the prosencephalon or forebrain, mesencephalon or midbrain, rhombencephalon or hindbrain and spinal cord. While the physical structure of the cat brain is very similar to that of humans and  have the largest percentage of its brain devoted to prosencephalon. Thus, the correct answer is option

1. The canal that passes through midbrain - canal aqueduct
   
2. The corpora quadrigemina are the four colliculi—two inferior, two superior—located on the tectum of the dorsal aspect of the midbrain.
   
3. The cerebral cortex of the human brain is highly convoluted, meaning it has many folds and creases. 
   
4. The medulla oblongata controls gastric secretion both by the parasympathetic branch of the nervous system and the endocrine system.
   

The forebrain is the part of the brain that includes cerebrum, thalamus and hypothalamus. It is involved in many functions, much of which are linked to the cerebrum. For example, intelligence or higher brain power is associated with the cerebrum. The outermost layer of the cerebrum is made up of four lobes frontal, temporal,parietal and occipital. The hearing, smelling and forming memories are functions of the temporal lobe. Vision is controlled by the occipital lobe. At the base of the forebrain-basal ganglia are found which control movement. Control and coordination are functions of nervous and endocrine systems because hypothalamus stimulates the master gland that regulates function of the other glands and brain and spinal cord (part of nervous system) directly regulates the function of other body parts.

The pia mater of the brain is the innermost of the three membranes, that cover it. It is the vascular membrane of the brain. It carries the minute branches of the two internal carotids and the two vertebral arteries. It also returns the blood to the heart. The dura mater is the most external membrane of the brain. It forms the internal periosteum of the skull. The dura mater is a dense, tough, inelastic fibrous membrane. The epidermis contains no blood vessels, and cells in the deepest layers are nourished by diffusion from blood capillaries extending to the upper layers of the dermis. So, the correct answer is option B.

Involuntary actions are those action that controlled by medulla oblongata which is a part of the autonomous nervous system where as voluntary actions are controlled by the cerebellum. The medulla oblongata directly controls heartbeat, blood pressure, breathing and digestion. It is located in the hindbrain, anterior to the cerebellum. It is a cone-shaped and contains the cardiac, respiratory, vomiting and vasomotor centers. Hence, the correct answer is option A.

The pneumotaxic center, also known as the pontine respiratory group (PRG), is a network of neurons in the rostral dorsal lateral pons. Its function is to inhibit inspiration, regulating inspiratory volume and rate.

Mid Brain of frog consists of two large optic lobes and crura cerebri. These optic lobes are centres for impulses coming to the eyes. They are hollow having cavities known as optocoel which communicates with the fourth ventricle behind a narrow cavity, iter. Hence, the correct answer is option C.

• The medulla oblongata is the part of the brainstem, that is situated between the pons and the spinal cord.
•  The medulla contains the cardiac, respiratory, vomiting and vasomotor centers and therefore deals with the autonomic (involuntary) functions of breathing, heart rate and blood pressure. 
• Thus compression of the medulla oblongata will lead to instant death.
• So, option A is correct here.

The hypothalamus and the brain stem controls the autonomic nervous system. They have control on the various functions like the respiration rate, heart rate, blood pressure, digestion, sweating, etc. The motor cortex area in the cerebrum is responsible for voluntary muscle activity. The cerebellum helps in coordinating the voluntary movements. Medulla oblongata is the brain stem which controls many involuntary activities like respiration, blood pressure, etc. The spinothalamic pathway is the tract followed by the sensation from skin to thalamus.

The midbrain is a small and contracted region of the brain. The anterior region of the midbrain is made up of two longitudinal bands of myelinated nerve fibres called the cerebral peduncles or crus cerebri or crura cerebri. The posterior part of the midbrain is made up of projected optic lobes called the colliculi.

The diencephalon is the small and posterior region of the forebrain. It is made up of the following parts:

The epiphysis or the pineal body is an endocrine gland that develops from the roof of the diencephalon. During the embryo development, it is connected with the brow spot in the embryo. The brow spot is the region between the two eyes. The cells are considered to be the modified neurological cells. It secretes a hormone called the melatonin that regulates the diurnal cycle of the body. Hence, the correct answer is 'Brow spot in embryo'

Man has solid optic lobes. In rabbit, man and mammal optic lobes are four in number and solid, optocoel is absent. In mammals, these are called as quadrigemina.
In frog two optic lobes are present and these are hollow and having optocoel. In frogs, it is called as bigemina.

The meninges are the coverings of the brain that are present interior to the cranium. The outermost layer is called the dura mater. The middle layer is the arachnoid mater. The pia mater is the innermost vascular layer. There is a space present between the dura mater and the arachnoid mater that is called the sub-dural space. It is filled with the serous fluid and provides mechanical support. The space between the arachnoid mater and the pia mater is called the sub-arachnoid space. It is filled with the cerebrospinal fluid.