L

The Parkinson's-Reversing Breakthrough

Is There A Cure for Parkinson Disease

Get Instant Access

l cerebellum frontal lobe locus coeruleus

^ thalamus amygdala hippocampus hypothalamus dorsal raphe nucleus

CNSforum.LDm

Figure 1.1. Main function of brain areas shown:

Amygdala - An anatomically coherent subsystem within the basal forebrain. Verbal and non-verbal expressions of fear and anger are interpreted by the amygdala. Cerebellum - One of the seven parts of the brain that is responsible for muscle co-ordination and modulation of the force and range of movement. It is involved in the learning of motor skills.

Cortex - The most highly developed area in humans and divided into four main regions, namely frontal, parietal, temporal and occipital. The cortex mediates and integrates higher motor, sensory and association functions. Dorsal raphe - Main serotonin (5-HT)-containing neurons that project through the brain. Other raphe neurons project down the spinal cord where they act as a gating mechanism for pain perception from the periphery. Main activity is in the regulation of mood, anxiety, sexual behaviour, sleep.

Hippocampus - Region primarily concerned with learning and short-term memory. Hypothalamus - Part of the diencephalon comprising several nuclei where hormones such as oxytocin and antidiuretic hormone are synthesized and pass to the pituitary gland. Involved in the regulation of the peripheral autonomic system and pituitary hormones such as prolactin, growth hormone and adrenocorticotrophic hormone.

Locus coeruleus - Collection of cell bodies containing about 50% of the noradrenergic neurons. Main activity is in the regulation of mood, anxiety and attention. Noradrenergic tracts innervate most regions of the brain. Thalamus - This acts as a relay station for pain, temperature and other bodily sensations.

Coupe Longitudinale Coeur

Figure 1.2. Coronal section through the human brain.

External capsule

Internal capsule

Figure 1.2. Coronal section through the human brain.

halves of the brain to communicate. The brain is permeated by four ventricles, the two largest of which occur beneath the cerebral cortex.

More details of brain structure become evident in the coronal section through the brain (see Figure 1.2). From this figure it is evident that the basal ganglia occupies a prominent role. The basal ganglia consists of the corpus striatum (consisting of the caudate nucleus, globus pallidus and putamen) and the substantia nigra. This region is concerned primarily with the control of movement and is malfunctional in Parkinson's disease and Huntington's disease. Figure 1.2 also illustrates the highly indented features of the cerebral cortex which can be visually differentiated into the surface grey matter, consisting of the cell bodies, and the much larger area of white matter which contains the myelinated axons connecting the cells of the cortex to the subcortical regions. The cerebrum contains the largest area of the brain, namely the two cerebral hemispheres.

From this brief description, it is apparent that the brain is really an assembly of organs all of which are structurally and functionally interconnected. Undoubtedly one of the most important areas for the psychopharmacologist is the so-called limbic system which is concerned with emotion. This region consists of the hippocampus (concerned with memory

Postcentral gyrus

Parietooccipital sulcus

Occipital lobe

Right cerebellar hemisphere

Medulla oblongata

Postcentral gyrus

Central Procentral Precentral sulcus gyrus sulcus

Parietooccipital sulcus

Occipital lobe

Right cerebellar hemisphere

Lateral sulcus

Superior temporal gyrus

Middle temporal gyrus

Inferior temporal gyrus

Figure 1.3. Main functional areas of the human brain.

Central Procentral Precentral sulcus gyrus sulcus

Superior frontal gyrus

Middle frontal gyrus

Inferior frontal gyrus

Lateral sulcus

Superior temporal gyrus

Middle temporal gyrus

Inferior temporal gyrus

Figure 1.3. Main functional areas of the human brain.

processing), the thalamus and hypothalamus (concerned with the control of the endocrine system, temperature regulation, feeding, etc.), the amygdala and septum (the emotional centres of the subcortex), the fornix and the cingulate gyrus of the cortex.

The cerebral cortex is conventionally subdivided into four main regions that may be delineated by the sulci, or large clefts, termed the frontal, temporal, parietal and occipital lobes. These names are derived from the bones of the skull which overlay them. Each lobe may be further subdivided according to its cellular structure and composition. Thus Brodmann has divided the cortex into approximately 50 discrete areas according to the specific cellular structure and function. For example, electrical stimulation of the strip of cerebral cortex in front of the central sulcus (see Figure 1.3) is responsible for motor commands to the muscles. This is termed the primary motor cortex and can be further subdivided according to which muscles are controlled in different parts of the body.

Similar maps exist in other parts of the brain; for example, the areas concerned with sensory input such as the primary somatosensory cortex (see Figure 1.3). Such brain maps of the body are important because information from various organs converge on the brain in a highly organized fashion and can therefore be reflected at all levels of information processing. Such

Thalamus

Thalamus

forebraln

Amygdala

Mamillary body

Figure 1.4. Main regions of the human brain concerned with memory, emotion and intellect.

forebraln

Amygdala

Mamillary body

Figure 1.4. Main regions of the human brain concerned with memory, emotion and intellect.

integration also allows the brain to obtain a true representation of the external environment as projected by the sensory organs.

The functional importance of specific cortical and subcortical regions of the brain may also be elucidated by studying the consequences of specific neurological lesions. For example, it has been shown by imaging methods that blood flow to the hippocampus of patients with Alzheimer's disease is dramatically reduced, the reduction paralleling the degree of short-term memory impairment. In addition, blood flow to the parietotemporal association cortex is also greatly reduced. Such changes in the functional activity of these brain areas may account for the memory and cognitive deficits that are symptomatic of the disease, the main function of the parietotemporal association cortex being the integration of sensory and cognitive processes in the brain.

Figures 1.4 and 1.5 show the main structures of the human brain and the areas of the brain which are primarily affected in different types of neurological disease.

In SUMMARY, areas of the cerebral cortex can be identified according to the bodily functions which they control. For example, the motor cortex for muscle control, somatosensory cortex for sensory input, visual cortex for visual input, an area concerned with speech, etc. In addition to these specific areas, the cortex also contains highly developed association areas which are probably involved in the complex synthesis of information.

Strokes

Alzheimer's disease

Strokes

Korsakoff's syndrome

Inflammation, anoxia, surgery for epilepsy

Figure 1.5. Areas of the human brain likely to be affected in some types of neurological dementing diseases.

Was this article helpful?

0 0
Anxiety and Panic Attacks

Anxiety and Panic Attacks

Suffering from Anxiety or Panic Attacks? Discover The Secrets to Stop Attacks in Their Tracks! Your heart is racing so fast and you don’t know why, at least not at first. Then your chest tightens and you feel like you are having a heart attack. All of a sudden, you start sweating and getting jittery.

Get My Free Ebook


Post a comment