Identifying Structures of the Brain - Anatomy

The cerebrum is the largest part of the brain and is responsible for the higher levels of thinking. The gyri are the folds of the brain (cerebrum) and the sulci are the grooves between the gyri. The cerebellum is the little brain and is responsible for balance and coordination.

The sulci, or folds, of the brain help to compartmentalize activity and increase surface area. The central sulcus runs along the coronal plane, from right to left across the surface of the brain. The frontal lobe is anterior to the sulcus and the parietal lobe is posterior to the sulcus.

The lateral sulcus separates the parietal lobe and temporal lobe. The parietooccipital sulcus separates the parietal and occipital lobes.

The temporal lobe is responsible for the interpretation of auditory stimuli. It also holds the hippocampus, a structure responsible for the formation and storage of memories.

The occipital lobe houses the visual cortex and the parietal lobe contains the somatosensory cortex (touch). The frontal lobe houses the motor cortex and functions in voluntary movement and conscious thought.

The meninges are responsible for protecting the brain and spinal cord. The tough dura mater is the outermost layer of the meninges, while the pia mater is the delicate inner layer that lines the brain and spinal cord.

In order from the outermost to innermost layer, the meninges are: dura mater, arachnoid mater, subarachnoid space, and pia mater. The arachnoid mater and subarachnoid space create separation and cushioning between the dura mater and pia mater.

The meninges consist of three layers of connective tissue that surround the central nervous system. Dura mater is the thick outermost layer and serves to partition the central nervous system and meninges from the rest of the body. Arachnoid mater is the loose middle layer with a web-like appearance and helps cushion and protect the central nervous system. The subarachnoid space exists between the arachnoid and pia mater and is filled with cerebrospinal fluid. Pia mater is the delicate inner layer that adheres to the surface of the brain and spinal cord, creating one final barrier.

The nervous system can be separated into the central and peripheral divisions. The central nervous system houses the brain and spinal cord, while the peripheral nervous system contains all offshoots of the spinal cord.

The brain contains several structure and serves as the point of origin for the twelve cranial nerves. The globus pallidus is a subcortical structure in the brain. The olfactory (CNI) and optic nerves (CNII) are located exclusively within the brain, never actually deviating into the periphery. These are the only cranial nerves considered to be part of the central nervous system. The meninges are the layers of connective tissue that surround the spinal cord and brain, creating the blood-brain barrier. The meninges include the dura mater, arachnoid mater, and pia mater and are considered part of the central nervous system.

The oculomotor nerve is the third cranial nerve (CNIII), and is considered part of the peripheral nervous system.

The amygdala is the center of emotions in the brain. The hippocampus is an area of learning and memory. The cerebellum is related to coordination of muscle activity. The medulla is for homeostasis of vital body functions.

The structure that connects the brain is called the corpus callosum. The medulla and cerebellum are part of the midbrain and hindbrain respectively. The infundibulum is the stalk of the pituitary gland.

The occipital lobe is devoted to vision. It is located on the posterior aspect of the brain. Compared to the other three primary lobes it has very few jobs. Similar to temporal lobe which makes sense of auditory stimuli (amongst other things) and the parietal lobe which processes touch sensations, temperature etc., the occipital lobe allows us to process what we see. The cerebellum is not a primary lobe of the brain, and it functions in coordinating motor movements such as walking and playing the guitar.

The diencephalon is the region of the brain between the cerebrum and the brain stem; it contains the epithalamus, thalamus, hypothalamus, ventral thalamus, and the third ventricle. The corpus callosum is the structure that connects right and left cerebral hemispheres. The pituitary gland is the small structure in the brain that controls the endocrine system. A ventricle is a fluid filled cavity within the brain.

The falx cerebelli is a dural fold that separates the two cerebellar hemispheres. The tentorium cerebelli is the dural fold that separates the cerebrum from the cerebellum. A ventricle is a fluid filled cavity within the cerebrum through which cerebrospinal fluid circulates. The pia mater is the deepest, thin meningeal layer that covers the surface of the brain.

The medulla (oblongata) is the lowest part of the brainstem. It controls many autonomic functions such as regulation of heart rate, respiratory rate and blood pressure. The pyramids are the two protruding columns found on the front of the medulla that contain motor nerve fibers. The olives are the round bulges found on the front and side of the medulla that relay signals to the cerebellum. The midbrain is the highest part of the brainstem.

The occipital lobe is the main area for interpreting visual stimuli. Wernicke's area is responsible for speech perception. The parietal lobe processes the sensations of touch, pressure, and temperature amongst other things. The temporal lobe processes sound mainly. Wernicke's area is located here. The olfactory lobe is involved in processing the sense of smell.

The nervous system consists of the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS can be thought of as the body's master control unit, it consist of the spinal cord, brainstem, and brain. The PNS is the body's link to the outside world, and consists of the autonomic nervous system (which branches into the sympathetic and parasympathetic nervous system) and the somatic nervous system.

The red nucleus is part of the midbrain. The vermis is part of the cerebellum and helps regulate trunk coordination, as well as vestibulo-ocular reflexes (VORs). The flocculonodular lobes, also part of the cerebellum, and work with the vermis to maintain trunk control and also help control the VORs. The dentate nucleus is a part of the cerebellum involved in motor planning in movement of the arms and legs.

The precentral gyrus is an important fold found in the frontal lobe and is a landmark for the primary motor area. The parietal lobe contains another important gyrus called the postcentral gyrus, which is the landmark for the somatosensory area of the cerebral cortex. The primary auditory area is located in the temporal lobe while the primary visual area is located in the occipital lobe. The insula is a structure that lies within the lateral fissure. It cannot be seen in the external view of the brain and plays a role in the limbic system.

The postcentral gyrus, a landmark for the somatosensory area of the cerebral cortex, is located in the parietal lobe of the cerebral cortex. The frontal lobe contains the precentral gyrus, which is a landmark for the primary motor area. The primary auditory area is located in the temporal lobe while the primary visual area is located in the occipital lobe. The insula is a fold in the cerebral cortex found within the lateral fissure.

The salivatory nucleus gives rise to the nerves that innervate the submandibular and sublingual salivary glands, as well as the lacrimal and nasal glands, and is the parasympathetic motor nucleus of the facial nerve however, it is found in the dorsal pons, not the medulla. The masticator nucleus is the trigeminal nerve motor nucleus, and is found in the pons. The mesencephalic nucleus is a sensory nucleus of the trigeminal nerve, and is found in the pons. The facial motor nucleus is found in the pons, and gives rise to the facial nerve branches that innervate the muscles of facial expression.

The Edinger-Westphal nucleus is the parasympathetic nuclues of cranial nerve III, and innervates (among other structures) the pupillary constrictors and lens ciliary muscles. The inferior salivatory nucleus is the parasympathetic nucleus of cranial nerve IX, and gives rise to the nerve that innervates the parotid gland. The superior salivatory nucleus is the parasympathetic nucleus of the facial nerve, and innvervates (among other structures) the submandibular and sublingual glands. The nucleus ambiguus has no parasympathetic function and is associated with motor functions of cranial nerves IX and X.

The brainstem consists of the midbrain, pons, and medulla oblongata. The brainstem continues inferiorly to become the spinal cord. The brainstem is responsible for basic living functions, including but not limited to: respiration, circulation (including heart rate), and digestion. As such, any injury to the brainstem would be catastrophic. Additionally ten of twelve cranial nerves pass through the brainstem, going on to provide the face and neck with motor and sensory functions. Furthermore, nerve conduction of the motor and sensory systems of the brain and body pass through the brain stem including the corticospinal tract (involved in motor activity), the posterior column-medial lemniscus pathway (involved in fine touch, vibration sensation, and proprioception), and the spinothalamic tract (involved in pain, temperature, itch, and crude touch).