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The Brain

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The Brain

Despite the myth of using just 10% of their total capacity, humans use nearly 100% of their brains every day. Nevertheless, the human brain is most likely one of the most complicated things on the planet. We wouldn't be able to think, feel emotions, or revel in joyful memories if we didn't have it. We'd be unable to walk, talk, see, hear, or touch. But how much do we truly know about it?

The brain is a complex organ consisting of two hemispheres, the right and the left, connected by nerve fibres known as the corpus callosum. These fibres allow the exchange of information between the hemispheres. The brain can be divided into three general regions: the forebrain, the midbrain, and the hindbrain.

The Brain Labelled brain image StudySmarter

Labelled brain image, Pixabay

These parts of the brain can be further divided into different lobes, and each lobe is responsible for specific functions, which will be the primary focus of this article. The lobes of the brain are usually divided into four sections.

The cerebrum, which includes the cerebral cortex, is the largest part of the brain.

Each hemisphere has subdivisions of lobes. Their functions differ depending on the hemisphere. Also, the two hemispheres of the brain control the opposite sides of the body, so the brain works contralaterally. Each hemisphere has a motor cortex that controls movements on the other side of the body.

The left frontal lobe is responsible for moving your left hand.

Around 86 billion neurones make up the brain.¹ Cerebrospinal fluid surrounds the brain and protects it from damage, removes waste products, and provides the brain with essential nutrients. The cerebrospinal fluid fills the brain's ventricles, which are a network that enables communication.

There are a total of four ventricles in the brain, and they consist of:

  • The lateral ventricles two, one in each half of the brain.
  • The third ventricle located in the diencephalon.
  • The fourth ventricle located in the hindbrain.

Parts of the brain

Cerebrum

The cerebrum is the largest part of the brain, composed of grey and white matter, and it contains the cerebral cortex.

Understandably, it is involved in many functions due to this, including movement coordination, language, and thinking and reasoning. It is made up of the functional aspects of the brain.

Cerebral cortex

The cerebral cortex is the outer layer of the brain's cerebrum. It is the brain's grey matter and consists of cell bodies and dendrites. It is folded and therefore has a large surface area (which is incredibly helpful because more surface area means more neurones and more neurones means more brain power).

The folds are separated into the gyri and sulci – the gyri are the ridges (bumps), and the sulci are the furrows (dips). It is then further divided into the two hemispheres.

It is responsible for:

  • Many different functions overall – It encompasses many areas of the brain and is widely interconnected.

  • It plays a significant role in memory, language, thoughts, and perceptions.

Lobes of the brain

As mentioned above, there are four lobes of the brain: frontal, parietal, occipital, and temporal lobe. Let's dive in to examine their functions.

Frontal lobe

The frontal lobe is responsible for:

  • Voluntary movements (such as moving a hand).

  • Expressive language (putting thoughts into words).

  • Managing complex or high-level executive functions (e.g., forming long-term memory, awareness, making judgements about self and others).

  • Social behaviour (this includes talking to others and initiating conversations, assessing others and the situation, and overall sexual behaviour).²

It contains crucial areas such as:

  • Broca's area in the left frontal lobe, which is involved in speech production.

Parietal lobe

The parietal lobe is responsible for:

  • Sensory perception and integration with other brain areas (interpretation of sound, touch, taste, vision and hearing, the brain is highly interconnected).

  • Spatial awareness, which perceives and helps map the world around us. As a result, you can walk from one end of the room to the other without bumping into everything.²

It contains essential areas such as:

  • The primary somatosensory cortex, a region that interprets information from different areas of the body.

Occipital lobe

The occipital lobe is responsible for:

  • Vision, the visual processing centre or visual cortex. It relays processed information to other parts of the brain for interpretation and processing.

  • Mapping the visual world (vital for spatial understanding and memory, it places objects so you can orient and remember them after scanning visual space).²

It contains essential areas such as:

  • Brodmann's area 17 (primary visual cortex), which is involved in depth perception and image placement.

Temporal lobe

The temporal lobe is responsible for:

  • Hearing, perceiving and interpreting sounds.

  • Memory acquisition, formation of memories and their embedding.

  • Categorising objects and giving them meaning (e.g., a coffee cup and a football).²

It contains essential areas such as:

  • Wernicke's area, which deals is responsible for understanding speech and converting pitches and different frequencies into intelligible pieces of information. It is responsible for the fluency of speech and ensures that it makes sense/is coherent.

The Brain Brain lobes StudySmarterBrain lobes, Katarina Gadže, StudySmarter Originals

Cerebellum and brain stem

The cerebellum is located at the base of the skull under the cerebrum and is responsible for:

  • Coordinating voluntary movements, e.g., moving a limb with dexterity.

  • Balance and equilibrium, so that you do not fall over and lose your balance.

  • Memory and reflex motor arcs

The brain stem leads to the spinal cord and is responsible for:

  • Reflexes (such as breathing, swallowing, and heart rate).

  • Sweating, blood pressure, and all types of automatic responses, not controlled voluntarily.

  • Ability to sleep.

Overall, any damage to the different parts of the brain can cause many problems. For example, water in the brain (sometimes called hydrocephalus, where water has accumulated in the brain's ventricles) can cause a rise in pressure that affects brain function.

The Brain The cerebellum 3D model StudySmarter

The cerebellum, 3D model, The Database Center for Life Science licensed under CC Attribution-Share Alike 2.1 Japan.

The Brain - Key takeaways

  • The brain is a complex organ consisting of two hemispheres, the right and the left, connected by nerve fibres called the corpus callosum.
  • The brain is composed of the forebrain, midbrain, and hindbrain.
  • It is also divided into different lobes, called the frontal lobe, parietal lobe, occipital lobe, and temporal lobe.
  • Each lobe has specific functions associated with its structure.
  • The cerebellum is located at the base of the skull, and the brain stem leads to the spinal cord. Both have their functions.

¹Frederico A.C. Azevedo et al., Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain, The Journal of comparative neurology, 28 September 2021

²Robert P. Lehr Jr., Brain Function, Centre for Neuro Skills, 28 September 2021

Frequently Asked Questions about The Brain

Humans use nearly 100% of their brain every day, despite the myth of using just 10% of their total capacity.

According to Azevedo et al., there are about 86 billion neurones in the brain.

No, the brain is an organ.

Functions are associated with regions, and there are more than fice. Five examples are visual processing, language comprehension, thought processing, emotions, and motor skills.

Final The Brain Quiz

Question

How many hemispheres are in the brain?

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Two, the right and left hemispheres.

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What connects the two hemispheres?

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Answer

Nerve fibres called the corpus callosum.

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What are the three general regions of the brain?

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The forebrain, midbrain, and hindbrain.

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The brain is composed of  _____ billion neurones.

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Answer

86 million

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Which fluid surrounds the brain?

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Cerebrospinal fluid.

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What lobes are in the brain?

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The frontal lobe, parietal lobe, occipital lobe, and temporal lobe.

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What is an important area in the frontal lobe?

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Broca’s area, involved in speech production.

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What is an important area in the parietal lobe?

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The primary somatosensory cortex.

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What are the functions of the occipital lobe?

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Vision and mapping (placing objects). It is the visual processing centre.

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What are the functions of the temporal lobe?

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Hearing, memory acquisition and categorising objects.

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What is an important area in the temporal lobe?

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Wernicke’s area, this area deals with speech comprehension

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What are the functions of the cerebellum?

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Coordination of voluntary movements, balance and equilibrium.

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What are the functions of the frontal lobe?

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Voluntary movement, expressive language, and higher cognitive functions.

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What are the functions of the parietal lobe?

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Sensory perception and integration, spatial awareness.

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What is an important area in the occipital lobe?

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Brodmann’s area 17, the primary visual cortex.

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What are the functions of the brain stem?

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Reflexes (such as breathing, swallowing, and heart rate).

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What is the localisation of function in the brain?

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Localisation is the concept that some brain regions are responsible for particular functions. They carry out and oversee the functions of behaviours and processes due to their structure and position.

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How does localisation of function in the brain contrast with the holistic view of the brain? 


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The holistic view of the brain states that functions occur across the entirety of the brain. Localisation suggests that specific functions occur in certain parts of the brain, not the whole of the brain.

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What is hemispheric lateralisation? 


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Hemispheric lateralisation is where each brain hemisphere is specialised to perform certain functions.

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What does contralateral mean? 


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Contralaterally refers to the side of the body opposite to which a function is responsible. So, the right hemisphere is responsible for the left side of the body and vice versa.

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What fold in the brain do the motor and somatosensory cortex run along? 


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The fold in the brain that the motor and somatosensory cortex run along is called the central sulcus. 

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What are the functions of the motor cortex? 


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The functions of the motor cortex are planning and executing voluntary movement, such as choosing to move a limb as well as spatial awareness and coordinating the two sides of the body.

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What happens if the motor cortex is damaged? 


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When the motor cortex is damaged, some muscles will no longer be voluntarily controlled, and in extreme cases, this can lead to total paralysis of certain parts of the body.


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What are the functions of the somatosensory cortex? What happens if it is damaged? 


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The function of the somatosensory cortex is receiving and processing sensations, such as touch and temperature. If the somatosensory cortex is damaged, people may lose sensation on the opposite side of the body.

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What are the functions of the visual cortex? 


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The visual cortex is responsible for processing visual information.

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What happens if the visual cortex is damaged?

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Damage to the visual cortex can result in partial or complete cortical blindness. 


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What are the functions of the auditory cortex? 


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The auditory cortex is responsible for perceiving sound, including pitch, tone, frequency, and determining its type.


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What are the functions of Broca’s area? What are the functions of Wernicke’s area?

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Broca’s area is responsible for speech production. Wernicke’s area is responsible for speech comprehension.

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Where are Broca’s and Wernicke’s areas located?

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Broca’s and Wernicke’s areas are both located in the left hemisphere.

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What is Broca’s aphasia? 


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In Broca’s aphasia, the damage occurs in Broca’s area in the brain, resulting in a loss of ability to form words and sentences.

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What is Wernicke’s aphasia?

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When Wernicke’s area is damaged, people struggle to understand speech. They may speak fluently, but it is meaningless and makes no sense.


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What connects the two hemispheres of the brain?

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The corpus callosum. 


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What is hemispheric lateralisation? 


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Hemispheric lateralisation is the idea that functions are divided up and performed by the different hemispheres of the brain; the hemispheres are specialised in certain functions and are not entirely alike.

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What area of the brain is a good example of a localised function? 


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Broca’s area is localised to the left hemisphere.

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What did patients suffer with before their corpus callosum was severed in Sperry's experiment? 


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Severe epilepsy.

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What three tasks did Sperry have patients do?

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The patients had to describe what they saw, tactile tests, and draw what they saw.

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What happens when the corpus callosum is severed? 


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Information is not shared between the right and left hemispheres.

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If an image was presented to the left visual field, what did patients struggle in doing? 


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Patients were unable to say what they had seen, as the language area of the brain had not been given the information of what the right hemisphere had seen through the left visual field.

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What did Sperry find?

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He found that people with split brains have two, separate visual inner worlds, each with its interpretation of visual images. There’s a lack of communication/cross-integration - one hemisphere does not know what the other is doing. There seem to be two streams of consciousness, each with its own memories, perceptions, and impulses. 

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What did Sperry conclude? 


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The conclusions indicate that the left hemisphere is dominant in speech production and language, whilst the right hemisphere is dominant in visual-motor tasks.

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Name one strength of hemispheric lateralisation? 


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It increases neural capacity, allowing for each hemisphere to specialise and attend to tasks simultaneously.

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Name a weakness of hemispheric lateralisation?

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Lateralisation decreases with age / Research carried out on animals / Split-brain procedures are rarely carried out now / Hard to generalise / Contradicting claims of the right hemisphere 

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What did Rogers et al. (2004) chicken study find? 


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Chickens with lateralisation enhanced their ability to find food and watch out for predators simultaneously. 


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What did Szaflarski et al. (2006) find?

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In fMRI studies on language lateralisation, a dominant hemisphere’s control increases from ages 5 to 20 years, plateaus (flattens out/remains steady) from ages 20 to 25 years, and decreases between 25 and 70 years.

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What did Turk et al. (2002) find?

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In the case of JW, they found that he had developed the ability to speak using the right hemisphere, so he could speak about the information given to both sides of the brain/visual fields. 


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What is plasticity in the brain?

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Plasticity is the brain’s ability to change and adapt to the environment, both in function and structure.

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What is synaptic pruning? 


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Synaptic pruning is when neuronal pathways are weakened or removed altogether due to lack of use/repetition. 


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What does synaptic pruning achieve? 


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It improves the brains communication efficiency, as it removes unnecessary or weakened pathways, but the ones remaining are stronger. 


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What is axonal sprouting? 


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This is when new connections form, with neuronal cell bodies forming additional branches and axons. 


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What did Kolb and Robinson (2004) find in their study?

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They found that addictive substances such as nicotine and morphine cause changes in the structure of dendrites and dendritic spines in brain regions, such as the nucleus accumbens and the prefrontal cortex. 


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