Anatomy of the brain

BrainOverview of the brain anatomy. Major divisions of the brain. Brainstem. Ventricles
~ 8 min

In this note, we are going to discuss the anatomy of the brain and its general functions.

Brain
Brain
Brain
Brain

Divisions

The brain consists of four major divisions:

  • Cerebral hemispheres (or cerebrum)
Cerebral hemispheres (or cerebrum)
Cerebral hemispheres (or cerebrum)
  • Diencephalon
Diencephalon
Diencephalon
  • Cerebellum
Cerebellum
Cerebellum
  • Brainstem
Brainstem
Brainstem

The brainstem itself is further divided into three parts:

  • Midbrain
Midbrain
Midbrain
  • Pons Varolii
Pons Varolii
Pons Varolii
  • Medulla oblongata
Medulla oblongata
Medulla oblongata

Each of these components plays a critical role in integrating sensory and motor information, maintaining vital body functions, and providing complex cognitive processes.

Cerebral hemispheres

Let’s start with the cerebral hemispheres, there are two of them: the left and the right. The surface of the hemispheres is uneven. It consists of numerous elevations known as gyri

Gyrus
Gyrus

and depressions known as sulci.

Sulcus
Sulcus

Major sulci divide the hemispheres into lobes:

  • Frontal lobe (lobus frontalis)
Frontal lobe
Frontal lobe
  • Temporal lobe (lobus temporalis)
Temporal lobe
Temporal lobe
  • Parietal lobe (lobus parietalis)
Parietal lobe
Parietal lobe
  • Occipital lobe (lobus occipitalis)
Occipital lobe
Occipital lobe

Additionally, there’s the insular lobe (or simply insula), which is kind of hidden deep into the brain.

Insular lobe (insula)
Insular lobe (insula)

The frontal lobe is responsible for controlling skeletal muscles, i.e., our movements, as well as for complex functions such as decision-making, motor planning, and determining what is good and what is bad.

Simply put, it defines us as humans in general and as individuals in particular.

The temporal lobe contains auditory, gustatory, speech, and memory centers. The parietal lobe receives and processes sensory information, such as the sense of touch, pain, vibration, etc.

The occipital lobe is predominantly responsible for vision.

The insular lobe participates in a bit of everything: from speech formation to the control of the heartbeat and other vital functions.

The cerebral hemispheres consist of gray and white matter, just like any other part of the central nervous system. Gray matter consists of neuronal cell bodies that generate nerve impulses,

Gray matter
Gray matter

while white matter comprises neuron processes that transmit nerve impulses, thereby providing communication between different parts of the nervous system.

White matter
White matter

Gray matter is represented by the cerebral cortex, located on the surface, and the subcortical nuclei, or so-called basal ganglia, which are situated slightly deeper.

Cerebral cortex
Cerebral cortex
Basal ganglia
Basal ganglia

White matter is grouped into thick bundles of nerve fibers that ascend and descend to various parts of the nervous system, performing a communicating function.

Diagram representing neural tracts
Diagram representing neural tracts

Diencephalon

The diencephalon consists of three parts:

  • epithalamus
Epithalamus
Epithalamus
  • thalamus
Thalamus
Thalamus
  • hypothalamus
Hypothalamus
Hypothalamus

The most important part of the epithalamus is the pineal body (or pineal gland), essentially an endocrine gland producing the hormone melatonin,

Pineal body / pineal gland
Pineal body / pineal gland
Pineal body / pineal gland
Pineal body / pineal gland

which participates in regulating sleep-wake cycles and is sometimes referred to as the sleep hormone.

The thalamus is an egg-shaped structure consisting of numerous nuclei.

Thalamus
Thalamus
Thalamus
Thalamus

A huge number of neural pathways pass through the thalamus, with its nuclei acting as switches in these pathways.

They allow some signals to pass to the cerebral cortex, while other signals are blocked or slightly slowed down. In general, the thalamus serves as a sort of “bouncer” in the brain.

The hypothalamus, like the thalamus, is essentially a collection of nuclei. It plays a role in maintaining homeostasis, i.e., the constancy of the internal environment, thereby controlling such areas as water balance, thermoregulation, sleep-wake cycles, sexual behavior, and so on.

Hypothalamic nuclei
Hypothalamic nuclei

Moreover, the hypothalamus is directly connected to the pituitary gland, the most crucial endocrine gland in our body, and significantly influences the production of its hormones.

Pituitary gland
Pituitary gland
Pituitary gland
Pituitary gland

Brainstem

The brainstem, as mentioned before, consists of three major divisions:

  • Midbrain
Midbrain
Midbrain
  • Pons Varolii
Pons Varolii
Pons Varolii
  • Medulla oblongata
Medulla oblongata
Medulla oblongata

In general, it controls vital, life-sustaining functions such as breathing, heart rate, vascular resistance, and partially digestion, among others.

Moreover, numerous cranial nerve nuclei are located within the brainstem. And the cranial nerves emerge from the brain at various levels.

Cerebellum

And the last division is the cerebellum, which literally means “little brain”.

Cerebellum
Cerebellum
Cerebellum
Cerebellum

The function of the cerebellum is to coordinate our movements, maintain balance and proper posture.

Cerebellum connections
Cerebellum connections

Brain meninges

Brain meninges
Brain meninges

Since the brain is the most important structure in our body, it must be well-protected against various kinds of damage. In this regard, the cranium alone is not sufficient; so the brain is additionally covered by three meninges:

  • Pia mater
Pia mater
Pia mater
  • Arachnoid mater
Arachnoid mater
Arachnoid mater
  • Dura mater
Dura mater
Dura mater

Brain ventricles

The ventricular system inside the brain consists of cavities known as ventricles.

Brain ventricles (ventriculi cerebri) - projection; superior aspect
Brain ventricles (ventriculi cerebri) - projection; superior aspect
Brain ventricles (ventriculi cerebri) - projection; lateral aspect
Brain ventricles (ventriculi cerebri) - projection; lateral aspect

These are a direct extension of the central canal of the spinal cord and are filled with cerebrospinal fluid.

Central canal of the spinal cord
Central canal of the spinal cord
Central canal of the spinal cord
Central canal of the spinal cord
Golosary

Anatomy of the brain

brain
encephalon
cerebral hemispheres / telencephalon
hemispheria cerebri / telencephalon
diencephalon
diencephalon
cerebellum
cerebellum
brainstem
truncus encephali
midbrain
mesencephalon
pons
pons Varolii
medulla oblongata
medulla oblongata
gyri
gyri
sulci
sulci
frontal lobe
lobus frontalis
temporal lobe
lobus temporalis
parietal lobe
lobus parietalis
occipital lobe
lobus occipitalis
insular lobe / insula
lobus insularis / insula
gray matter
substantia grisea
white matter
substantia alba
cerebral cortex
cortex cerebri
basal nuclei
nuclei basales
epithalamus
epithalamus
thalamus
thalamus
hypothalamus
hypothalamus
pineal gland
corpus pineale / glandula pinealis
pia mater
pia mater
arachnoid mater
arachnoidea mater
dura mater
dura mater
ventricular system
ventriculi cerebri
central canal
canalis centralis
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