NEURO-ANATOMY
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Central nervous system
The central nervous system (CNS) consists of the brain and spinal cord. The brain is found in the cranial cavity, while the spinal cord is found in the vertebral column. Both are protected by three layers of meninges (dura, arachnoid, and pia mater).
| Cerebrum | Internal Structure
The cerebrum is comprised of two different types of tissue – grey matter and white matter:
External StructureExternally, the cerebrum has a highly convoluted appearance, consisting of sulci (grooves or depressions) and gyri (ridges or elevations). It is divided into two anatomically symmetrical hemispheres by the longitudinal fissure – a major sulcus that runs in the median sagittal plane. The two cerebral hemispheres are connected by a white matter structure, called the corpus callosum.
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Lobes of the CerebrumThe cerebral cortex is classified into four lobes, according to the name of the corresponding cranial bone that approximately overlies each part. Each lobe contains various cortical association areas – where information from different modalities are collated for processing. Together, these areas function to give us a meaningful perceptual interpretation and experience of our surrounding environment. |
Frontal LobeHigher intellect, personality, mood, social conduct and language (dominant hemisphere side only). Functional deficit if lobe affected: A diverse range of presentations, often personality and behavioural changes occur and an inability to solve problems develops. Parietal LobeControl of: language and calculation on the dominant hemisphere side, and visuospatial functions (e.g. 2-point discrimination) on the non-dominant hemisphere side. Functional deficit if lobe affected: Typically presents with attention deficits e.g. contralateral hemispatial neglect syndrome: where the patient does not pay attention to the side of the body opposite to the lesion. Temporal LobeMemory and language – this includes hearing as it is the location of the primary auditory cortex. Functional deficit if lobe affected: Presents with recognition deficits (agnosias) e.g. auditory agnosia: patient cannot recognise basic sounds, prosopagnosia: failure to recognise faces. Occipital LobeThe primary visual cortex (V1) is located within the occipital lobe and hence its cortical association area is responsible for vision. Functional deficit if lobe affected: Visual field defects: contralateral hemianopia or quadrantanopia with macular sparing.
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| A gyrus is a ridge-like elevation found on the surface of the cerebral cortex. Gyri are surrounded by depressions known as sulci, and together they form the iconic folded surface of the brain. Gyri are made up of the gray matter of the cerebral cortex, which mainly consists of nerve cell bodies and dendrites.
Precentral gyrus – Found on the lateral surface of the the frontal lobe and acts as the primary motor area of the brain. Inferior frontal gyrus – Found on the lateral surface of the frontal lobe, involved in speech production. Postcentral gyrus – Found on the lateral surface of the parietal lobe, and acts as the primary somesthetic area of the brain. Inferior parietal lobule – Found on the lateral surface of the parietal lobe, divided into the following: Superior temporal gyrus – Found on the lateral surface of the temporal lobe, contains the Wernicke’s area which allows us to compute language. |
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Subcortical structuresThe subcortical structures are a group of diverse structures found deep within the brain. They include the diencephalon (thalamus, epithalamus, subthalamus and hypothalamus), pituitary gland, limbic structures and the basal ganglia. |
The hypothalamus and pituitary gland are involved in hormone production and regulation
The limbic system (includes; hippocampal formation, fornix, amygdala, insular cortex, and others) is involved in memory, olfaction, emotional behaviour and overall physiological balance of the body (homeostasis) The basal ganglia are a functional group of nuclei which together comprise a unit of the extrapyramidal motor system, modifying motor activity |
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| Brainstem | The brainstem is the most caudal part of the brain. It consists of the midbrain (mesencephalon), pons and medulla oblongata. The cerebellum, pons and medulla oblongata are often grouped together under the name hindbrain (rhombencephalon). The importance of the brainstem lies in several of its features, together giving the brainstem the informal definition as our survival center:
It contains all cranial nerve nuclei (except CN I, CNII), providing somatic and autonomic control of the head and neck. |
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| Cerebellum | Cerebellum; Image: Paul Kim Cerebellum The cerebellum lies between the cerebrum and the medulla of the brainstem. It plays an important role in regulating motor functions; participating in the planning and modulation of motor activity, including the coordination of the body while moving.Like the cerebrum, the cerebellum has two hemispheres (left and right). They are connected by a midline mass called the vermis. It also has three lobes; anterior, posterior and flocculonodular. The cerebellar cortex forms the outermost layer of cerebellum and is comprised of grey matter. Important structures of the cerebellum include it’s many paired nuclei within its deep white matter and the cerebellar peduncles |
NEURO-ANATOMY
Word
Central nervous system
The central nervous system (CNS) consists of the brain and spinal cord. The brain is found in the cranial cavity, while the spinal cord is found in the vertebral column. Both are protected by three layers of meninges (dura, arachnoid, and pia mater).
| BRAIN | |||||
| CEREBRUM | Right Hemisphere | Left Hemisphere | |||
| Cerebrum | Internal Structure
The cerebrum is comprised of two different types of tissue – grey matter and white matter:
External StructureExternally, the cerebrum has a highly convoluted appearance, consisting of sulci (grooves or depressions) and gyri (ridges or elevations). It is divided into two anatomically symmetrical hemispheres by the longitudinal fissure – a major sulcus that runs in the median sagittal plane. The two cerebral hemispheres are connected by a white matter structure, called the corpus callosum.
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Lobes of the CerebrumThe cerebral cortex is classified into four lobes, according to the name of the corresponding cranial bone that approximately overlies each part. Each lobe contains various cortical association areas – where information from different modalities are collated for processing. Together, these areas function to give us a meaningful perceptual interpretation and experience of our surrounding environment. |
Frontal LobeHigher intellect, personality, mood, social conduct and language (dominant hemisphere side only). Functional deficit if lobe affected: A diverse range of presentations, often personality and behavioural changes occur and an inability to solve problems develops. Parietal LobeControl of: language and calculation on the dominant hemisphere side, and visuospatial functions (e.g. 2-point discrimination) on the non-dominant hemisphere side. Functional deficit if lobe affected: Typically presents with attention deficits e.g. contralateral hemispatial neglect syndrome: where the patient does not pay attention to the side of the body opposite to the lesion. Temporal LobeMemory and language – this includes hearing as it is the location of the primary auditory cortex. Functional deficit if lobe affected: Presents with recognition deficits (agnosias) e.g. auditory agnosia: patient cannot recognise basic sounds, prosopagnosia: failure to recognise faces. Occipital LobeThe primary visual cortex (V1) is located within the occipital lobe and hence its cortical association area is responsible for vision. Functional deficit if lobe affected: Visual field defects: contralateral hemianopia or quadrantanopia with macular sparing.
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| A gyrus is a ridge-like elevation found on the surface of the cerebral cortex. Gyri are surrounded by depressions known as sulci, and together they form the iconic folded surface of the brain. Gyri are made up of the gray matter of the cerebral cortex, which mainly consists of nerve cell bodies and dendrites.
Precentral gyrus – Found on the lateral surface of the the frontal lobe and acts as the primary motor area of the brain. Inferior frontal gyrus – Found on the lateral surface of the frontal lobe, involved in speech production. Postcentral gyrus – Found on the lateral surface of the parietal lobe, and acts as the primary somesthetic area of the brain. Inferior parietal lobule – Found on the lateral surface of the parietal lobe, divided into the following: Superior temporal gyrus – Found on the lateral surface of the temporal lobe, contains the Wernicke’s area which allows us to compute language. |
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Subcortical structuresThe subcortical structures are a group of diverse structures found deep within the brain. They include the diencephalon (thalamus, epithalamus, subthalamus and hypothalamus), pituitary gland, limbic structures and the basal ganglia. |
The hypothalamus and pituitary gland are involved in hormone production and regulation
The limbic system (includes; hippocampal formation, fornix, amygdala, insular cortex, and others) is involved in memory, olfaction, emotional behaviour and overall physiological balance of the body (homeostasis) The basal ganglia are a functional group of nuclei which together comprise a unit of the extrapyramidal motor system, modifying motor activity |
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| Brainstem | The brainstem is the most caudal part of the brain. It consists of the midbrain (mesencephalon), pons and medulla oblongata. The cerebellum, pons and medulla oblongata are often grouped together under the name hindbrain (rhombencephalon). The importance of the brainstem lies in several of its features, together giving the brainstem the informal definition as our survival center:
It contains all cranial nerve nuclei (except CN I, CNII), providing somatic and autonomic control of the head and neck. |
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| Cerebellum | Cerebellum; Image: Paul Kim Cerebellum The cerebellum lies between the cerebrum and the medulla of the brainstem. It plays an important role in regulating motor functions; participating in the planning and modulation of motor activity, including the coordination of the body while moving.Like the cerebrum, the cerebellum has two hemispheres (left and right). They are connected by a midline mass called the vermis. It also has three lobes; anterior, posterior and flocculonodular. The cerebellar cortex forms the outermost layer of cerebellum and is comprised of grey matter. Important structures of the cerebellum include it’s many paired nuclei within its deep white matter and the cerebellar peduncles |
Each side of your brain contains four lobes. The frontal lobe is important for cognitive functions and control of voluntary movement or activity. The parietal lobe processes information about temperature, taste, touch and movement, while the occipital lobe is primarily responsible for vision. The temporal lobe processes memories, integrating them with sensations of taste, sound, sight and touch.
| LOBES | |||||
| Frontal | Parietal | Temporal | Occipital | ||
| • Personality, behavior, emotions • Judgment, planning, problem solving • Speech: speaking and writing (Broca’s area) • Body movement (motor strip) • Intelligence, concentration, self-awareness |
• Interprets language, words • Sense of touch, pain, temperature (sensory strip) • Interprets signals from vision, hearing, motor, sensory and memory • Spatial and visual perception • Occipital lobe • Interprets vision (color, light, movement) |
• Understanding language (Wernicke’s area) • Memory • Hearing • Sequencing and organization • Language |
The occipital lobe is primarily responsible for visual processing. It contains the primary and association visual cortex | ||
| CEREBELLUM | |||||
| The Cerebellum is situated in the posterior fossa and is connected to the brain stem by three paired cerebellar peduncles. It has ‘two hemispheres that are connected by the vermis’ | Spinocerebellum strip | Vestibulocerebellum strip | Pontocerebellum strip | ||
| BRAINSTEM | |||||
| Midbrain | Pons | Medulla | |||
| The midbrain acts as a passageway for the hemispheres and the lower brain and it is also the centre for the auditory and visual reflexes. |
The pons acts as a connection between the midbrain and the medulla allowing fibres to travel through from one to the other. Within the tegmentum the spinothalamic tracts and parts of the reticular activating system (controls consciousness) are located. |
The medulla oblongata is the lower half of the brainstem. It controls autonomic functions and connects the higher levels of the brain to the spinal cord. The medulla oblongata is responsible for regulating several basic functions of the autonomic nervous system, including respiration, cardiac function, vasodilation, and reflexes like vomiting, coughing, sneezing, and swallowing. |
Language
Aphasia is a disturbance of language affecting speech production, comprehension, reading or writing, due to brain injury – most commonly from stroke or trauma. The type of aphasia depends on the brain area damaged.
• Broca’s area lies in the left frontal lobe (Fig 3). If this area is damaged, one may have difficulty moving the tongue or facial muscles to produce the sounds of speech. The person can still read and understand spoken language but has difficulty in speaking and writing (i.e. forming letters and words, does not write within lines) – called Broca’s aphasia.
• Wernicke’s area: lies in the left temporal lobe (Fig 3). Damage to this area causes Wernicke’s aphasia. The individual may speak in long sentences that have no meaning, add unnecessary words, and even create new words. They can make speech sounds, however they have difficulty understanding speech and are therefore unaware of their mistakes.
Memory
Memory is a complex process that includes three phases: encoding (deciding what information is important), storing, and recalling
• Short-term memory, also called working memory, occurs in the prefrontal cortex. It stores information for about one minute and its capacity is limited to about 7 items. For example, it enables you to dial a phone number someone just told you. It also intervenes during reading, to memorize the sentence you have just read, so that the next one makes sense.
• Long-term memory is processed in the hippocampus of the temporal lobe and is activated when you want to memorize something for a longer time. This memory has unlimited content and duration capacity. It contains personal memories as well as facts and figures.
• Skill memory is processed in the cerebellum, which relays information to the basal ganglia. It stores automatic learned memories like tying a shoe, playing an instrument, or riding a bike.
CRANIAL NERVES
Mnemonics:
Old Olympus Occasionally Tries Trigonometry And Feels Very Gloomy, Vague And Hypoactive.
The cranial nerves: The locations of the cranial nerves within the brain.
• The olfactory nerve (I): This is instrumental for the sense of smell, it is one of the few nerves that are capable of regeneration.
• The optic nerve (II): This nerve carries visual information from the retina of the eye to the brain.
• The oculomotor nerve (III): This controls most of the eye’s movements, the constriction of the pupil, and maintains an open eyelid.
• The trochlear nerve (IV): A motor nerve that innervates the superior oblique muscle of the eye, which controls rotational movement.
• The trigeminal nerve (V): This is responsible for sensation and motor function in the face and mouth.
• The abducens nerve (VI): A motor nerve that innervates the lateral rectus muscle of the eye, which controls lateral movement.
• The facial nerve (VII): This controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity.
• The vestibulocochlear nerve (VIII): This is responsible for transmitting sound and equilibrium (balance) information from the inner ear to the brain.
• The glossopharyngeal nerve (IX): This nerve receives sensory information from the tonsils, the pharynx, the middle ear, and the rest of the tongue.
• The vagus nerve (X): This is responsible for many tasks, including heart rate, gastrointestinal peristalsis, sweating, and muscle movements in the mouth, including speech and keeping the larynx open for breathing.
• The spinal accessory (XI): This nerve controls specific muscles of the shoulder and neck.
• The hypoglossal nerve (XII): This nerve controls the tongue movements of speech, food manipulation, and swallowing.
Some say marry money but my brother says big brains matter more
• S: sensory (olfactory nerve – CN I)
• S: sensory (optic nerve – CN II)
• M: motor (oculomotor nerve – CN III)
• M: motor (trochlear nerve – CN IV)
• B: both (trigeminal nerve – CN V)
• M: motor (abducens nerve – CN VI)
• B: both (facial nerve – CN VII)
• S: sensory (vestibulocochlear nerve – CN VIII)
• B: both (glossopharyngeal nerve CN IX)
• B: both (vagus nerve – CN X)
• M: motor (spinal accessory nerve – CN XI)
• M: motor (hypoglossal nerve – CN XII)
References:
https://teachmeanatomy.info/neuroanatomy/structures/cerebrum/
https://www.kenhub.com/en/library/anatomy/neuroanatomy
https://mayfieldclinic.com/pe-anatbrain.html
https://courses.lumenlearning.com/boundless-ap/chapter/cranial-nerves/
https://www.uhs.nhs.uk/Media/suhtideal/Informationforstudents/StudentandLearnerInformation/Neuroanatomyandphysiologicalworkbook.pdf
https://www.mayoclinic.org/brain-lobes/img-20008887
