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Brain structures

Figure 1: The major structures of the human brain

Sources: The major source for this entire article is Marieb's Anatomy & Physiology 9th edition[1]

The human brain is a very complex structure with various different components. It is what processes information for us and gives us our thoughts, our beliefs, our fears, our personality, etc.

There are four major, distinct anatomical regions: the cerebrum, the diencephalon, the cerebellum and the brain stem.


CerebrumEdit

Lobes of the cerebrum

Figure 2: The lobes of the cerebrum

The cerebrum is the largest of these brain regions, comprising of 85% of the brain, by mass, and is covered by the cerebral cortex, which is the so called "gray matter" of the brain.[1]:431, 432 This gray matter layer is 2-4 mm thick and comprises about 40% of the human brain by mass. It is involved in:[1]:431, 432

  • Memory
  • Learning
  • Our concept of ourselves and the universe
  • Our senses
  • Communication
  • Voluntary movements

The cerebrum is also comprised of two hemispheres, the left and right hemispheres.[1]:431 They control the contralateral side of the body (that is, the opposite side: the left hemisphere controls the right side of the body; the right hemisphere controls the left side of the body).[1]:433

The frontal lobe includes the prefrontal cortex (PFC) which is considered the most complex part of the cerebral cortex and is involved in working memory, executive function (like decision making and planning), problem solving, attention and impulse control. The primary motor cortex is also contained in the frontal lobe and is involved in voluntary movements of skeletal muscle. Broca's area is also found in the frontal lobe and is required for speech control. 

The parietal lobe contains primary somatosensory cortex (PSC) which is required for spatial perception and processing. Other parts of the parietal lobe are involved in sensory (especially one's sense of touch) perception, processing and the hearing.

The temporal lobe is involved in hearing and equilibrium (sense of balance).

The occipital lobe which is involved in the processing of visual information (that is, sight) and our understanding of the written word.

The insula is the final lobe that is found under lateral sulcus (or sylvian fissure in figure 2). It processes information regarding hearing and equilibrium, similarly to the temporal lobe. 

Between the two hemispheres is the corpus collasum that connects the two. 

DiencephalonEdit

Diencephalon

Figure 3: The diencephalon

The diencephalon is comprised of two individual components: the hypothalamus and thalamus. The hypothalamus is required for various house-keeping functions, mostly related to hormone production, but also those related to involuntary muscle movement (like those in the digestive tract, heart, glands, etc.). It also regulates body temperature, alertness, thirst, physical responses to emotions (like high heart rate in response to fear), appetite, feeding, emotions and behaviour. The thalamus, on the other hand, regulates voluntary muscle movement, arousal, and relays sensory information; and has roles in learning and memory.

CerebellumEdit

The cerebellum is a cauliflower-shaped structure that is second only to the cerebrum in size, at about 11% of the mass of the brain, as a whole. It has two hemispheres, similarly to the cerebrum, it processes information from the cerebral motor cortex (in the cerebrum), the brain stem and sensory receptors in the rest of the body. It is required for smooth coordinated muscle movements, like those in typing, driving and sports.

Limbic systemEdit

The limbic system consists of six major structures that are in close proximity to each other: the corpus collasum, hippocampus (involved in the conversion of short-term memories to long-term memories), hypothalamus, the olfactory bulb (required for one's sense of smell), septum pellucidum and thalamus.

Brain stemEdit

The brain stem includes the medulla oblongata (MO), midbrain, pons and reticular formation (RF). The MO relays ascending (from nerves in the rest of the body) sensory information and controls heart rate, blood vessel diameter, breathing rate, vomiting, coughing, etc. Whereas the midbrain contains the substantia nigra which is required for voluntary movement control and is the major brain region destroyed by Parkinson's disease. The pons relays information from the cerebrum to the cerebellum, cooperates with the medulla to control breathing rate and depth. The RF helps regulate voluntary muscle activity and the activity of muscles within the major internal organs like the stomach, intestines, etc.

Reference listEdit

  1. 1.0 1.1 1.2 1.3 1.4 Marieb, EN; Hoehn, K (2013). Human Anatomy & Physiology (9th ed. ed.). Boston, USA: Pearson. ISBN 978-0-321-74326-8. 

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