The cerebral cortex, meninges, basal ganglia, and ventricular system

Last updated: April 25, 2022

Summarytoggle arrow icon

The cerebrum (telencephalon) is the largest part of the brain and comprises the cerebral cortex and subcortical structures (e.g., basal ganglia, hippocampus). The longitudinal fissure divides the brain into two hemispheres. The cortex represents the top-outer layer of the brain, which receives its convoluted appearance from a network of gyri and sulci. Sulci separate the cerebral cortex further into a frontal, temporal, parietal, and occipital lobe. The cerebrum is the key structure involved in perception, language, and coordination. The basal ganglia are situated beneath the cortex, and they are heavily involved in motor control. The cortical hemispheres contain one of the lateral ventricles each, with the smaller third and fourth ventricles being located between the two thalami in the diencephalon and between the cerebral aqueduct and obex respectively. The four ventricles form an interconnected system that produces, drains, and is filled with cerebrospinal fluid, which plays a role in waste removal and cushioning of the brain. The meninges comprise the three protective membranes that envelop the central nervous system, i.e. the brain and spinal cord.

Overview

  • The cerebral cortex receives its convoluted appearance from a network of gyri (rounded ridges on the surface of the cortex) and sulci (furrows separating the gyri).
  • The longitudinal fissure divides the brain into two hemispheres.
  • Deep sulci divide each hemisphere further into a frontal, temporal, parietal, and occipital lobe.
  • Deep sulci separate the cerebral cortex into different lobes: frontal, temporal, parietal, and occipital
  • The main sulci

Frontal lobe

Overview of the frontal lobe
Area Location Motor and cognitive functions Effect of lesion

Primary motor cortex

(Brodmann area 4)

  • Initiation of voluntary movement
  • Gives rise to axons that form the corticospinal tract
  • The cortical regions responsible for processing the motor functions of the different regions of the body can be mapped using the motor homunculus.
    • The individual parts of the body are arranged against the corresponding cortical regions proportionate in size to their degree of innervation (e.g., the hand is represented disproportionately larger than the foot).
    • Arranged medially to laterally as follows: toes, ankle, knee, hip, trunk, shoulder, elbow, wrist, hand, little finger to thumb, eye, facial expression, mouth, chin, tongue, swallowing.
    • The primary sensory cortex is mapped in the same way using the sensory homunculus.

Premotor cortex

(Brodmann area 6)

Frontal eye field

(Brodmann area 8)

  • Transient ipsilateral conjugate deviation of the eyes

Prefrontal cortex

(prefrontal association area)

  • Higher cognitive functions (e.g., goal-setting, decision-making)
  • Short term memory
  • Concentration
  • Contains Brodmann areas 8–14, 24, 25, 32, and 45–47

Broca area

(Brodmann areas 44 and 45)

The cortical regions responsible for processing the motor functions of the different regions of the body can be mapped using a motor homunculus.

Parietal lobe

Overview of the parietal lobe
Area Location Characteristics (sensory functions) Effect of lesion

Primary somatosensory cortex

  • Receives input from the ventral posterior nuclei of the thalamus
  • Contributes to the corticospinal tract
  • The cortical regions receiving sensory input of the different regions of the body can be mapped using the sensory homunculus.
    • The individual parts of the body are arranged against the corresponding cortical regions proportionate in size to their degree of innervation (e.g., the lips are represented disproportionately larger than the feet).
    • The primary motor cortex is mapped in the same way using the motor homunculus.
Somatosensory association cortex
  • Superior parietal lobule and supramarginal gyrus
  • Integrates palpatory sensory information for pattern recognition
  • Contralateral astereognosis (loss of ability to identify an object by tactile input alone)
  • Contralateral astatognosis (loss of ability to recognize the position of one's own body parts)
  • Apraxia (loss of ability to perform coordinated, purposeful, and/or learned movements when asked, even if the request is understood)
    • Most common type: facial apraxia (loss of ability to coordinate and execute facial movements, like whistling or winking)
  • Conduction aphasia (e.g., loss of ability to repeat verbal commands)
Visual association cortex
  • Integrates visual sensory information for pattern recognition
  • Injury to dominant hemisphere: Gerstmann syndrome
    • Inability to recognize right or left
    • Finger agnosia (loss of ability to distinguish or recognize one's own fingers or those of others)
    • Agraphia (loss of ability to write down thoughts)
    • Dyscalculia (loss of ability to do mathematical calculations)
  • Unilateral injury to the nondominant hemisphere: contralateral hemispatial neglect syndrome

Temporal lobe

Overview of the temporal lobe
Area Location Characteristics (hearing) Effect of lesion

Primary auditory cortex

(Brodmann areas 41 and 42)

Wernicke area

Occipital lobe

Overview of the occipital lobe
Area Location Characteristics (visual functions) Effect of lesion
Primary visual cortex
Secondary visual cortex
  • Integrates visual properties such as color, position in space, and illusory contours

Bilateral or large unilateral (esp. right-sided) lesions in the ventral occipitotemporal cortex may cause impairment of facial recognition (prosopagnosia).

Insular lobe

  • Location
  • Characteristics
  • Function
    • Processing of emotions
    • Perception of body functions (interoception)
    • Integration and perception of somatosensory stimuli
    • Perception of gustatory and olfactory stimuli
    • Modulation of autonomic functions (e.g., blood pressure, gastrointestinal motility)

Internal capsule

Meninges

Overview of the meningeal layers [1]
Meningeal layer Origin Anatomy Characteristics
Dura mater
Arachnoid mater
Pia mater

Falces of the brain

Overview of the falces of the brain
Structure Location Characteristics Sites of attachment Cerebral sinuses
Falx cerebri
  • Separates the cerebral hemispheres

Falx cerebelli

  • Site of attachment to the internal occipital crest, which contains the occipital sinus

Tentorium cerebelli

  • Separates the cranial cavity into infratentorial and supratentorial compartments

Spaces of the CNS

Overview of the spaces of the CNS
Space Description Boundaries Clinical significance
Epidural space
Subdural space
Subarachnoid space

The Subarachnoid Space extends to the S2 vertebra.

Overview

Overview of the basal ganglia
Basal ganglia Location Clinical significance
Striatum Caudate nucleus
Putamen
Lentiform nucleus Globus pallidus
Putamen
Subthalamic nucleus
Substantia nigra
  • Parkinson disease is characterized by neuronal degeneration in the substantial nigra


Cortico-basal ganglia-thalamo-cortical loop (CBGTC)

  • A neuronal circuit between the cortices of the brain, the basal ganglia, and the thalamus
  • Via this loop, the basal ganglia aid in the initiation of movement, control of skeletal muscles, and adjustment of posture.
  • Two main pathways: the direct pathway and the indirect pathway.
  • The balance of activity between the direct and indirect pathways is modulated by dopamine.

Functional anatomy of the basal ganglia

Overview of the functional anatomy of the basal ganglia
Structure Function/Characteristics Neurotransmitter Motor activity
Striatum

Motor excitatory part

  • Inhibition of the Gpi
  • Contains mainly D1 receptors, which are activated by dopamine
Motor inhibitory part
  • Inhibition of the Gpe
  • Contains mainly D2 receptors, which are inhibited by dopamine
Pallidum Globus pallidus internus (Gpi)
Globus pallidus externus (Gpe)
Subthalamic nucleus
  • Stimulation of the Gpi
  • Stimulation of the pars reticularis of the substantia nigra
Substantia nigra Pars compacta
  • Stimulation of the motor excitatory part of the striatum
  • Inhibition of the motor inhibitory part of the striatum
Pars reticularis

Direct pathway of the basal ganglia (excitatory)

Binding of dopamine to D1 Receptors stimulates the excitatory D1Rect pathway.

Indirect pathway of the basal ganglia (inhibitory)

  • Function
    • Decrease in motor activity
    • Modulation of the disinhibitory effect of the direct pathway
  • Pathway

The indirect pathway is inhibitory.

Dopaminergic pathways

Overview of dopaminergic pathways
Pathway Location Characteristics Defect
Nigrostriatal
  • Controls motor function
Tuberoinfundibular
  • From the arcuate nucleus (infundibular nucleus) to the median eminence
Mesolimbic
Mesocortical
  • Controls executive functions

Overview

Overview of the ventricular system
Ventricle Anatomy Drainage
Lateral ventricles
  • Paired (right and left)
  • Located in the cerebral hemispheres
  • Into the 3rd ventricle via the paired interventricular foramina (of Monro)

Third ventricle

Fourth ventricle
  • Single midline ventricle
  • Located dorsal to the pons and upper medulla

The foramina of Luschka are the Lateral apertures and the foramen of Magendie is the Medial aperture of the fourth ventricle.

Cerebrospinal fluid

Basal cisterns (subarachnoid cisterns)

Overview

Cortical neuroanatomy

Neocortex

Allocortex

  • Composed of three layers
  • Consists of the hippocampus and the olfactory cortex

Blood-brain barrier

Blood-cerebrospinal fluid barrier (BCSFB)

Brain metabolism [2][3][4]

  • Energy demand
    • The brain requires 15% of the cardiac output and ∼ 20% of the body's oxygen to function properly. [2]
    • Main energy-demanding functions of the brain:
      • Active transportation of ions
      • Maintenance and restoration of membrane potentials
      • Synthesis and metabolism of neurotransmitters
    • Metabolic requirements vary according to regional neuronal activity and are directly related to changes in cerebral blood flow and energy substrate utilization (see “Cerebral autoregulation”).
  • Energy sources
    • Energy is mainly derived from the aerobic oxidation of glucose.
    • The uptake of glucose by neurons is provided by the insulin-independent GLUT3 transporter.
    • Under particular circumstances, the brain has the capacity to use other energy substrates:

Brain homeostasis [5]

Impaired ability of the brain to maintain homeostasis may result in weight gain, obesity, and diabetes mellitus type 2.

Overview

Embryology of the brain

Overview of brain embryology
Primary vesicles Brain vesicle Derived parts of the brain Derived fluid-filled structure

Prosencephalon

(forebrain)

Telencephalon
Diencephalon

Mesencephalon

(midbrain)

Mesencephalon

Rhombencephalon

(hindbrain)

Metencephalon
Myelencephalon

Tell Di, Mes met My: The 1st vesicle is telencephalon, 2nd is diencephalon, 3rd is mesencephalon, 4th is metencephalon, and 5th is myelencephalon (the order of the secondary brain vesicles).

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  8. Segarra M, Aburto MR, Acker-Palmer A. Blood–Brain Barrier Dynamics to Maintain Brain Homeostasis. Trends Neurosci. 2021; 44 (5): p.393-405. doi: 10.1016/j.tins.2020.12.002 . | Open in Read by QxMD

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