Sulci and gyri

Frontal lobe

The dorsolateral surface of the frontal lobe is divided into three regions, namelY:

  1. Precentral gyrus (motor gyrus): Immediately anterior to the central sulcus and posterior to the pre-central sulcus
  2. Premotor gyrus, anterior to the pre-central sulcus
  3. Prefrontal area anterior to the premotor sulcus

The prefrontal regon is divided into three by the superior and inferior frontal sulci.

  • Superior frontal gyrus
  • Middle frontal gyrus
  • Inferior frontal gyrus

The inferior frontal gyrus is divided into three by the anterior ascending rami of the lateral sulci into

  • Pars opercularis (1)
  • Pars triangularis (2)
  • Pars orbitales (3)
 
 

 

The inferior surface of the frontal lobe
 
  • Olfactory sulcus, contains olfactory bulb and tract.

  • Medial to the olfactory sulcus is the gyrus rectus (1)

  • Lateral to the olfactory sulcus is the orbital gyrus (2)

  • The olfactory tract posteriorly divides into medial and lateral olfactory striae.
    Caudal to this division is the olfactory trigone and anterior perforated substance.

. Name the stractures labelled 3-8.

 

Functional specialization of the frontal lobe

Area of frontal lobe
Function (s)
The pre-motor and pre-central (primary motor) areas: Regulation and coordination of fine somatic motor activity, especially of the distal muscles

The inferior frontal gyrus:

  • Pars opercularis
  • pars triangularis
Motor speech (Broca's) area: the regulation of production of speech.
The prefontal areas Higher ‘cognitive' function regulation including:
  • Intelligence
  • Initiative
  • Determination
  • Inhibition
  • Memory
  • Reasoning e.t.c.
Olfactory (olfactory striae) Olfactory function
olfactory cortex, cingulate gyrus Limbic

Parietal Lobe

Three parts of the parietal lobe are:

  • Post central gyrus, lies between the central and post central sulci. It is usually not continuous, but broken up into superior and inferior segments and

    The parts of the parietal lobe caudal to the post central gyrus are divided by a horizontally oriented sulcus, the intra-parietal sulcus into two parts i.e.:
    • Superior parietal lobule
    • Inferior parietal lobule, which consists of two gyri.
  • The supramarginal, about both banks of an ascending ramus of the lateral sulcus

  • The angular gyrus , which surrounds the ascending terminal part of the superior temporal sulcus.

 

 
 

Parietal Lobe
Area of parietal lobe
Function (s)
Supramarginal gyrus. Sensory speech (Wernicke's) area

post central gyrus

Primary somatic sensory
inferior parietal lobule Sensory association
inferior part of the parietal lobe, posterior to the general sensory areastriae) The gustatory area
cingulate gyrus Limbic

Homunculus

  • This is the inverted map of the body on the cerebral cortex

  • On both sensory and motor gyri, the body is differentially represented. More sensitive parts, and those requiring fine control have larger representation

  • In this motor homunculus the body is arranged over the surface of pre central gyrus in a coronal section of cerebral hemisphere. Note the large area devoted to the hand and face.