BIO 004 · Human Anatomy
The Brain
Block 5 · Module 3: The Central Nervous System, the Brain
A reference for the brain video and lab. This page covers the development of the brain, the cerebrum with its lobes, white matter tracts, and basal ganglia, the functional areas of the cortex, the diencephalon, the cerebellum, the limbic system, and the arterial supply of the brain. The focus is on the structures and the job each one does.
How to use this sheet Toggle the toolbar above. Notes prints the full reference for review. Study prints as a fill-in-the-blank worksheet. Print it, then write each definition while you watch the video or read your book. Quiz me is on-screen typing practice: type the term, click Reveal to check yourself. The comparison grids respond to Study and Quiz too, with a Reveal button on each row.
The Foundations video gives you a complete foundational understanding of this topic, enough on its own for a foundational course. Learn it first, then move on to the Deep dive, which adds the majors-level depth for this course.
- Trace the development of the brain from the neural tube vesicles.
- Identify the cerebrum, its lobes, white matter tracts, and basal ganglia.
- Map the functional areas of the cerebral cortex.
- Name the parts of the diencephalon, the cerebellum, the limbic system, and the arteries that supply the brain.
Your pre-work
Work through these the evening before class. None of it is turned in. It is how you learn the material and build your spaced recall.
This is more than a checklist. Ticking these boxes is the start, not the finish. Committing this material to memory and being able to apply it takes considerable time and repeated effort. You are not done when the boxes are checked. Put in the real hours, and keep coming back for frequent recall and review until the material is genuinely yours.
The brain regions
Add a labeled midsagittal section showing the cerebrum, diencephalon, brainstem, and cerebellum.
The lobes of the cerebrum
Add a labeled lateral view of the five cerebral lobes.
The Circle of Willis
Add a labeled inferior view of the cerebral arterial circle and its thirteen arteries.
The Brain, an Overview
The brain sits within the cranial cavity and holds roughly 85 billion neurons. It is the body's master control and integration center. The brain has four major parts.
- Brainthe organ within the cranial cavity, the control and integration center of the body
- Cerebrumthe largest brain part, the seat of conscious thought, sensation, and voluntary movement
- Diencephalonthe deep brain region between the cerebrum and the brainstem
- Brainstemthe stalk connecting the brain to the spinal cord, covered on its own sheet
- Cerebellumthe structure behind the brainstem that coordinates movement
- Gray matterneuron cell bodies, dendrites, and unmyelinated fibers; on the outside of the brain
- White matterbundles of myelinated axons; on the inside of the brain
Development of the Brain
The brain and spinal cord develop from the ectodermal neural tube. The tube swells at its anterior end into a series of vesicles that mature into the adult brain.
- Neural tubethe ectodermal tube from which the entire central nervous system develops
- Primary brain vesiclesthe first three swellings: the prosencephalon (forebrain), the mesencephalon (midbrain), and the rhombencephalon (hindbrain)
- Secondary brain vesiclesthe prosencephalon divides into the telencephalon and diencephalon; the rhombencephalon divides into the metencephalon and myelencephalon
Each secondary vesicle matures into specific adult structures. Compare them.
| Secondary vesicle | Adult structures |
|---|---|
| Telencephalon | the cerebrum and the lateral ventricles |
| Diencephalon | the thalamus, hypothalamus, epithalamus, and third ventricle |
| Mesencephalon | the midbrain and the cerebral aqueduct |
| Metencephalon | the pons, the cerebellum, and the upper fourth ventricle |
| Myelencephalon | the medulla oblongata and the lower fourth ventricle |
The Cerebrum
The cerebrum is the largest region of the brain. Its surface is folded to pack more cortex into the skull, and a thick core of white matter lies beneath.
- Cerebral hemispheresthe right and left halves of the cerebrum, joined by the corpus callosum, each with five lobes
- Cerebral cortexthe outer layer of gray matter, 2 to 4 mm thick, holding billions of neuron cell bodies
- Cerebral white matterthe myelinated axons beneath the cortex that connect cortical areas to each other and to lower regions
- Gyrithe raised ridges of the folded cortex
- Sulcithe shallow grooves between the gyri
- Fissuresthe deepest grooves, which divide major regions of the brain
Specific named sulci and fissures mark the boundaries on the cerebral surface. Compare them.
| Structure | What it separates |
|---|---|
| Central sulcus | the frontal lobe from the parietal lobe; it divides the primary motor cortex in front from the primary somatosensory cortex behind |
| Lateral sulcus | the frontal and parietal lobes from the temporal lobe |
| Parieto-occipital sulcus | the parietal lobe from the occipital lobe |
| Longitudinal fissure | the left and right cerebral hemispheres |
| Transverse fissure | the cerebrum from the cerebellum |
The Cerebral Lobes
Each hemisphere has five lobes. Four are named for the cranial bone above them; the fifth, the insula, lies hidden deep in the lateral sulcus. Compare them.
| Lobe | Location | Primary roles |
|---|---|---|
| Frontal lobe | the front of the cerebrum | voluntary movement at the precentral gyrus, motor planning, speech production at Broca's area, judgment, and personality |
| Parietal lobe | behind the central sulcus | somatic sensation at the postcentral gyrus and spatial orientation |
| Temporal lobe | the lower side of the cerebrum | hearing, language comprehension at Wernicke's area, and memory |
| Occipital lobe | the back of the cerebrum | visual processing |
| Insula | deep within the lateral sulcus | taste, visceral sensation, and emotion |
Cerebral White Matter Tracts
The white matter beneath the cortex is sorted into three classes of fiber, grouped by where each tract begins and ends. Compare them.
| Fiber class | What it connects | Examples |
|---|---|---|
| Association fibers | gyri within the same hemisphere, allowing communication across one side | the arcuate fasciculus, which links Broca's and Wernicke's areas |
| Commissural fibers | matching gyri between the two hemispheres | the corpus callosum, the largest; also the anterior and posterior commissures |
| Projection fibers | the cortex with lower brain regions and the spinal cord, as ascending or descending tracts | the internal capsule, the major projection pathway beside the basal ganglia |
The Basal Ganglia
The basal ganglia, also called the cerebral nuclei, are deep masses of gray matter buried within the cerebral white matter. They help regulate movement.
- Basal gangliathe cerebral nuclei, deep gray matter masses that control semi-voluntary movement, such as the arm swing of walking
- Caudate nucleusa long, curved nucleus, one of the core components
- Putamena core component lying lateral to the globus pallidus
- Globus pallidusa core component lying medial to the putamen
- Substantia nigraa midbrain nucleus grouped with the basal ganglia by function
- Subthalamic nucleusa diencephalic nucleus grouped with the basal ganglia by function
- Rolesinitiating and regulating movement, suppressing unwanted movement, and modulating muscle tone
Functional Areas of the Cerebral Cortex
The cortex is mapped into specialized areas of three kinds: motor areas that issue commands, sensory areas that receive input, and association areas that interpret and integrate.
- Motor areasissue the commands for voluntary movement; found mainly in the frontal lobe
- Sensory areasreceive and begin to process input from the body's receptors
- Association areasintegrate sensory input with memory and reasoning to plan a response
Each named area has a fixed location and a specific job. Compare them.
| Area | Location | Role |
|---|---|---|
| Primary motor cortex | precentral gyrus of the frontal lobe | initiates voluntary movement |
| Premotor cortex | anterior to the primary motor cortex | plans learned, patterned movements |
| Supplementary motor area | medial frontal lobe | coordinates complex bilateral movements |
| Frontal eye field | middle frontal gyrus | controls voluntary eye movement |
| Broca's area | inferior frontal gyrus, usually the left | controls the motor production of speech |
| Primary somatosensory cortex | postcentral gyrus of the parietal lobe | receives conscious touch, pressure, and proprioception |
| Primary visual cortex | occipital lobe, at the calcarine sulcus | receives raw visual input |
| Primary auditory cortex | superior temporal gyrus | receives auditory input |
| Primary gustatory cortex | insula and inferior postcentral gyrus | receives taste input |
| Primary olfactory cortex | medial temporal lobe, at the uncus | receives smell input |
| Vestibular cortex | posterior insula and the parietal cortex | receives input for balance and spatial orientation |
| Prefrontal cortex | anterior frontal lobe | executive function: judgment, planning, and personality |
| Wernicke's area | the temporal and parietal junction, usually the left | comprehension of spoken and written language |
| Somatosensory association area | posterior to the postcentral gyrus | interprets texture, shape, and spatial orientation |
| Visual association area | surrounding the primary visual cortex | recognizes faces and objects |
| Auditory association area | adjacent to the primary auditory cortex | interprets speech and music |
The Diencephalon
The diencephalon links the cerebral hemispheres to the brainstem and surrounds the third ventricle. It has three parts: the thalamus, the hypothalamus, and the epithalamus.
- Thalamuspaired oval masses of gray matter that form about 80 percent of the diencephalon; the main sensory relay station to the cortex
- Massa intermediathe interthalamic adhesion, a bridge joining the right and left thalami
- Thalamic nucleithe individual nuclei of the thalamus, each one relaying a specific sensory or motor modality
- Hypothalamusthe region below the thalamus; the master control center for homeostasis
- Hypothalamic rolescontrolling the autonomic nervous system, endocrine function through the pituitary, body temperature, hunger and thirst, and sleep-wake rhythms
- Epithalamusthe small posterior part of the diencephalon
- Pineal glandthe endocrine gland of the epithalamus that secretes melatonin
- Habenular nucleinuclei of the epithalamus involved in emotional and visceral responses to smell
- Third ventriclethe midline fluid-filled cavity enclosed by the diencephalon
The Cerebellum
The cerebellum is the second largest brain region, sitting in the posterior cranial fossa below the occipital lobes. It coordinates movement, posture, and balance.
- Cerebellar hemispheresthe two lateral halves of the cerebellum
- Vermisthe narrow midline band connecting the two hemispheres
- Cerebellar lobeseach hemisphere has an anterior, a posterior, and a flocculonodular lobe
- Foliathe fine, leaf-like folds of the cerebellar surface
- Cerebellar cortexthe outer gray matter of the cerebellum
- Arbor vitaethe branching, tree-like pattern of cerebellar white matter
- Deep cerebellar nucleigray matter nuclei embedded in the white matter, such as the dentate nucleus
Three pairs of cerebellar peduncles, stalks of white matter, connect the cerebellum to the brainstem. Compare them.
| Peduncle | What it connects |
|---|---|
| Superior cerebellar peduncle | connects to the midbrain; carries mostly output from the cerebellum |
| Middle cerebellar peduncle | connects to the pons; carries input from the pontine nuclei |
| Inferior cerebellar peduncle | connects to the medulla; carries input from the spinal cord and vestibular system |
The Limbic System
The limbic system is a functional system, not a single structure. Its parts ring the diencephalon and reach into the cerebrum. It sets emotional state and supports memory.
- Limbic systema functional system spanning the cerebrum and diencephalon that sets emotional state and supports memory
- Amygdalathe limbic structure for fear and aggression, linking emotion to memory
- Hippocampusthe limbic structure essential for forming new long-term memories
- Cingulate gyrusthe limbic gyrus arching above the corpus callosum, involved in expressing emotion
- Limbic rolesestablishing emotional states and drives, linking conscious thought to brainstem responses, and supporting long-term memory
Cerebral Arterial Supply: The Circle of Willis
The brain is fed by two arterial systems that join in a ring at the base of the brain, the cerebral arterial circle, also called the Circle of Willis. The ring lets blood cross from one source to another if a vessel narrows or is blocked.
- Anterior circulationthe blood supply from the internal carotid arteries; it feeds most of the cerebrum
- Posterior circulationthe blood supply from the vertebral and basilar arteries; it feeds the brainstem, cerebellum, and occipital lobe
- Cerebral arterial circlethe Circle of Willis, the ring of arteries at the base of the brain that joins the anterior and posterior circulations
- Anastomosisa connection between two arteries that gives blood an alternate route if one path is blocked
The thirteen named arteries of the cerebral arterial supply. Compare what each one feeds.
| Artery | What it supplies |
|---|---|
| Anterior cerebral artery | the medial surface of the frontal and parietal lobes |
| Anterior communicating artery | a short bridge joining the right and left anterior cerebral arteries; it closes the front of the ring |
| Internal carotid artery | the main feed of the anterior circulation; it enters the skull and divides into the anterior and middle cerebral arteries |
| Middle cerebral artery | the lateral surface of the cerebrum, including the motor and sensory cortex for the body; the largest branch of the internal carotid |
| Posterior communicating artery | joins the internal carotid to the posterior cerebral artery on each side, linking the anterior and posterior circulations |
| Posterior cerebral artery | the occipital lobe and the inferior surface of the temporal lobe |
| Basilar artery | formed by the union of the two vertebral arteries; it runs up the front of the pons and supplies the brainstem |
| Superior cerebellar artery | a branch of the basilar artery to the superior surface of the cerebellum |
| Anterior inferior cerebellar artery (AICA) | a branch of the basilar artery to the anterior and inferior cerebellum |
| Vertebral arteries | the paired arteries that enter through the foramen magnum and unite to form the basilar artery |
| Posterior inferior cerebellar artery (PICA) | a branch of the vertebral artery to the inferior cerebellum and the lateral medulla |
| Anterior spinal artery | a single midline artery formed from both vertebral arteries; it runs down the front of the spinal cord |
| Posterior spinal arteries | paired arteries from the vertebral arteries that run down the back of the spinal cord |
See also: The Brainstem and The Spinal Cord for the rest of the central nervous system, and The Meninges and Cerebrospinal Fluid.
Study questions
Work on answering these in writing, in your own words. They are the questions to bring to class, and good practice for the reasoning the exams ask for.
- Name the lobes of the cerebrum and one function associated with each.
- Compare the three types of white matter tracts, association, commissural, and projection, by what each connects.
- Name the parts of the diencephalon and the job of each.
- Explain what the basal ganglia and the cerebellum each contribute to movement.
Step 2 . Retrieval check
Now explain it back, in your own words.
In 60 words or more, pull together what the video just taught you. Include the key concepts. This is the point where the learning actually sticks. After you submit, your spaced-recall cards for this topic unlock.