BRAIN ANATOMY AND FUNCTION
Is there a biological basis for behaviour? In other words, could our behaviour be primarily controlled by our brains?
Neuropsychologists believe that all human behaviour is caused by biological mechanisms and that humans have no free will. They believe that our personalities are determined by brain organisation and the genetics we inherit.. So, whether you are: clever, funny, silly, artistic, etc. It is not down to free-will, parents’ or society- it’s all about the biological processes. .
Biological causes of behaviour:
Neurotransmitters, e.g., our brain chemistry
Genetics
How our brain is structured. and wired
Hormones
If our brain gets damaged or diseased in some way.
THE BRAIN
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The brain is the most complex organ of the human body. The human brain contains about 100 billion neurons, more than 100,000 km of interconnections, and has an estimated storage capacity of 1.25 × 1012 bytes. These impressive numbers have led to the idea that our cognitive capabilities are virtually without limit.
The brain consists of areas of grey matter and areas of white matter. Grey matter is mainly made up of the cell bodies of neurons whereas white matter is mostly made up of the bundled myelinated axons of neurons (myelin is white).
The brain and spinal cord make up the central nervous system (CNS) which links to the peripheral nervous system (PNS). The PNS consists of nerve pathways outwith the CNS which relay information to and from the rest of the body (e.g. muscles, organs, endocrine glands).
The whole nervous system works as a ‘closed loop’ system:
The CNS receives information from the rest of the body via the PNS.
The CNS integrates the information received.
The CNS directs and coordinates the activity of all other parts of the body via the PN
THE THREE MAIN STRUCTURES OF THE BRAIN:
FOREBRAIN, MIDBRAIN AND HINDBRAIN
THE FOREBRAIN
The forebrain is the largest part of the brain it is located at the front (anterior). It is divided into three main parts: the cerebrum, thalamus and hypothalamus.
THE CERBRUM: The cerebrum is the largest part of the forebrain; it is also known as the telencephalon and is the largest and most highly developed part of the human brain. It encompasses about two-thirds of the brain mass and lies over and around most of the brain's structures.
The cerebrum is divided into two connected cerebral hemispheres. The cerebrum is divided into right and left hemispheres that are connected by the corpus callosum. In general, the right hemisphere relays messages to and receives messages from the left side of the body. The left hemisphere provides the same functions as the right side of the body. Each hemisphere is divided into four lobes: frontal, parietal, temporal and occipital.
THE CEREBRAL CORTEX: In the human brain, the Cerebral Cortex is the largest part of the Cerebrum which covers the two cerebral hemispheres. A cortex or cortices (plural) are the outer layers of an organ in the body. The cerebral cortex is the outer layer of the cerebrum. Other areas in the brain also have a cortex- do you remember when we did Stress and the Adrenal Cortex (literally the outer layer (skin, bark) of the adrenal gland.)? In Latin, cortex literally means “new bark.
The term is sometimes INCORRECTLY extended to refer to THE entire brain.
The Cerebral Cortex covers the whole cerebrum. It looks wrinkled surface observed in pictures of the brain. The human cerebral cortex is 2-4 mm (0.08-0.16 inches) thick and comprises six layers, labelled from the outermost inwards, I to VI. In humans, the Cerebral Cortex is involved in higher functions such as sensory perception, generation of motor commands, spatial reasoning and language, There are two types of cortex in the cerebral cortex – the true isocortex and the proisocortex.
The cerebral cortex is sometimes called "neo", because it is evolutionarily the newest part of the cereberal cortex. Some people prefer to call it the "Iso Cortex" because it sounds more neutral. The “Cerebral cortex" is almost synonymously called the neo Cortex, although the term Cerebral Cortex includes the Hippocampus and Rhinal Cortex, in addition to Neo Cortex. Just "cortex" usually means the same thing as the cerebral cortex.
The cerebral cortex is the hallmark of mammalian brains and is not present in birds or in reptiles. It is also the most divergent part across mammalian species. While the Cerebral Cortex is smooth in rats and some other small mammals, it has deep grooves (sulci) and wrinkles (gyri) in primates and several other mammals. These folds serve to increase the area of the cerebral cortex considerably. In humans, it accounts for about 76% of the brain's volume.
If you compare the brains of mice, monkeys and humans (SEE THE PICTURE BELOW), you can see that the size and outlook are very different among the three brains. Humans, dolphins and primates have been found to have the most neocortical neurons.
In dead, preserved brains, the Cerebral Cortex is grey, hence the name grey matter. Neurons form grey matter and their unmyelinated fibres. In contrast, the white matter below the grey matter of the cortex is formed predominantly by myelinated axons interconnecting different regions of the central nervous system.
THE CORTICES
Prefrontal Cortex
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The frontal lobe contains the motor cortex, which is involved in planning and coordinating movement; the prefrontal cortex, which is responsible for higher-level cognitive functioning; and Broca's area, which is essential for language production. Pre-Frontal Cortex: In mammalian brain anatomy, the prefrontal cortex (PFC) is the cerebral cortex, which covers the front part of the frontal lobe. The PFC contains *Brodmann areas” and Broca’s area, amongst many other important functions such as problem-solving, emotion and complex thought.
*The Brodmann areas are a way of mapping the cortex and its distinguished functions, pioneered by Korbinian Brodmann, from which the areas are named. Through using Brodmann's areas, the cortex of the brain can be divided into 52 areas, which are numbered sequentially.
Primary Motor Cortex
Initiation of voluntary movement
Primary Somatosensory Cortex
Receives tactile information from the body
Sensory Association Area
Processing of multisensory information
Visual Cortex
Complex processing of visual information
Visual Cortex
Detection of simple visual stimuli
THE MIDBRAIN
The midbrain, also called mesencephalon, is a region of the developing vertebrate brain that is composed of the tectum and tegmentum. The midbrain serves important functions in motor movement, particularly eye movements, and in auditory and visual processing. It is located within the brainstem and between the two other developmental regions of the brain, the forebrain and the hindbrain; compared with those regions, the midbrain is relatively small.
The brainstem connects the cerebrum and cerebellum with the spinal cord. It has three parts: midbrain, pons and medulla. In addition to containing nerve pathways to and from the rest of the brain, the brainstem has centres controlling breathing, circulation, heart rate, and wakefulness/sleep.
THE HINDBRAIN
The hindbrain is located toward the rear and lower portion of a person’s brain. It controls several important body functions and processes, including respiration and heart rate. It comprises FOUR parts: the Medulla, Reticular formation, Cerebellum and Pons.
The reticular formation is a network of nerves important to a person’s attention or focus, as well as his response to stimuli. This part of the brain helps an individual pay attention to just one important thing, even if he’s faced with several types of stimuli at once. It blocks those less important stimuli, allowing the person to focus. For example, if a person is in a potentially dangerous situation, the reticular formation blocks other stimuli, allowing him to focus solely on doing what’s needed to help him survive. Interestingly, the reticular formation slows down when a person goes to sleep. It does not, however, stop working to block some sensory messages while allowing others through. This area of the brain is why many people can stay asleep despite the sounds of passing cars or creaks and groans of a house settling, yet wake to the sound of a smoke detector.
The pons is the part of the hindbrain located above the medulla. It forms a kind of bridge between the medulla and the cerebellum. This structure relays messages between the cerebellum and the cerebrum, which is part of the forebrain. It also helps control movement and plays a role in sleep.
Cerebellum: The cerebellum, or "little brain", is similar to the cerebrum in that it has two hemispheres and has a highly folded surface or cortex. This structure is associated with regulating and coordinating movement, posture, and balance. The cerebellum is assumed to be much older than the cerebrum, evolutionarily. What do I mean by this? In other words, animals that scientists assume to have evolved prior to humans, for example, reptiles, do have developed cerebellum. However, reptiles do not have Cerebral Cortex.
THE BRAIN LOBES
Lobe: Part of an organ that appears to be separate in some way from the rest. A lobe may be demarcated from the rest of the organ by a fissure (crack), Sulcus (groove), and connective tissue or simply by its shape. For example, there are the frontal, parietal, temporal, and occipital lobes of the brain. The word "lobe" comes from the Greek lobos, meaning "a small rounded projection," which is long applied only to the familiar round projection at the base of the ear, the earlobe. The lobes of the brain, thyroid, lungs, and liver were hardly mentioned in English until the 16th century.
Frontal Lobe: front of brain
The frontal lobe is home to our cognitive thinking, and it is this process that determines and shapes an individual's personality. In human beings, the frontal lobe attains maturity when the individual is around the age of 25. This means that by the time we are 25 years of age, we have achieved a level of cognitive maturity. So don’t get a tattoo before 25 or you will regret it!! Functions of the frontal lobe include reasoning, planning, organizing thoughts, behaviour, sexual urges, emotions, problem-solving, judging, organizing parts of speech, and motor skills (movement).
The frontal lobe is extremely vulnerable to injury due to its location, as it is in front of the central cranium. Any damage to this brain lobe can lead to one or more of the following problems.
Alteration in talking habits
Reduced sexual interest or peculiar sexual habits
Impairment of risk-taking ability
Reduced or no sense of taste and/or smell
Impaired spontaneity and mental flexibility
Increased susceptibility to distractions
Judgment, that is, the ability to recognize future consequences resulting from ongoing actions.
Analytical and critical reasoning, problem-solving
Cognition and memory are mostly concentrated in the frontal lobe. Thus, any damage to this region leads to memory loss and dementia. In some people during old age, there is severe memory loss due to malfunctioning of the frontal lobe, which leads to Alzheimer's disease.
Emotional traits of a person are stored in the frontal lobe.
The frontal lobe is also responsible for storing the language skills of a person.
Inability to express language (Broca’s Aphasia).
Temporal Lobe: Side of the head above ears.
There are two temporal lobes, each of which is located on each side of the brain; left and right, at about the level of the ears. The temporal lobes contain the primary auditory cortex, and hence, are responsible for all auditory processing. These lobes also contain the hippocampus, which is responsible for the formation of long-term memory and the sorting of new information. The right lobe and left lobe control visual memory and verbal memory, respectively. Thus, temporal lobes are involved with hearing, speech and memory.
Effects of temporal lobe damage can again be classified depending on which side of the lobe is affected.
Left Temporal Lobe Damage: It leads to decreased ability to recall audio and visual content, difficulty in recognizing words and remembering verbal material.
Right Temporal Lobe damage: Damage to the right side of this lobe results in difficulty in recognizing visual content and tonal sequences, as well as recalling previously encountered music or drawings.
Difficulty in recognizing faces (Prosopagnosia).
Difficulty in understanding spoken words (Wernicke’s Aphasia).
Disturbance with selective attention to what we see and hear.
Difficulty with identification of, and verbalisation about objects. Short-term memory loss.
Interference with long-term memory
Increased or decreased interest in sexual behaviour.
Inability to categorise objects (categorisation).
Right lobe damage can cause persistent talking.
Increased aggressive behaviour.
Parietal Lobe: Near the back and top of the head.
The parietal lobe integrates sensory information from various parts of the body. The optic nerve passes through the parietal lobe to the occipital lobe. Functions of the parietal lobe include:
Spatial orientation,
Visual perception,
Recognition
The parietal lobe appreciates basic sensations, such as touch, pain, pressure, temperature (heat and cold) and various joint movements.
It is also responsible for discriminating the intensity of various stimuli, like distinguishing warm from hot, ice cold from cold, etc.
It is responsible for storing data, which helps in later fine-tuning tactile sensation, i.e., it helps in recognizing common familiar objects placed in our hand without looking at them.
The parietal lobe helps in the recognition of spatial relationships, that is, the realization of the exact point of tactile sensation, the ability to discriminate between two points of tactile stimulation, etc.
Any damage to the parietal lobes would result in abnormalities in spatial processing and body image. Below are the problems that occur after damage to a particular site of the parietal lobe.
Left Parietal Lobe Damage: Any damage to the left side of this lobe can cause Gerstmann's syndrome, aphasia (language disorder), and agnosia (abnormal perception of objects).
Right Parietal Lobe Damage: Right side damage results in difficulty in making something, impaired personal care skills and impaired drawing ability.
Bi-lateral Parietal Lobe Damage: It causes Balint's syndrome which is characterized by impaired visual attention and motor activities.
Occipital Lobe: The back of the head
The smallest of all four lobes, the Occipital lobe, is responsible for the visual perception system, as it contains the primary visual cortex. Functions of the occipital lobe include visual reception, visual-spatial processing, movement, and colour recognition. Disorders of the occipital lobe can cause visual illusions.
Because of the location, this lobe is not particularly susceptible to injury, although significant trauma can result in a few problems.
Disruption of the visual-perceptual system
Defects in vision (Visual Field Cuts).
Difficulty with locating objects in the environment. Difficulty with identifying colors (Color Agnosia).
Production of hallucinations Visual illusions - inaccurately seeing objects.
Word blindness - inability to recognize words.
Difficulty in recognizing drawn objects.
Inability to recognize the movement of an object (Movement Agnosia).
Difficulties with reading and writing.
QUESTIONS
Definition of 'Lobe': What is a lobe and what are some of the ways a lobe can be separated from the rest of an organ?
Frontal Lobe Functions: List at least three functions of the frontal lobe.
Maturity of Frontal Lobe: At what age does the frontal lobe typically reach maturity in humans?
Frontal Lobe Vulnerabilities: Name one vulnerability of the frontal lobe due to its location.
Consequences of Frontal Lobe Damage: What are some of the problems that can arise from damage to the frontal lobe?
Temporal Lobe Location and Function: Where is the temporal lobe located, and what is its primary function?
Differences in Temporal Lobe Damage: How does damage to the left temporal lobe differ from damage to the right temporal lobe?
Parietal Lobe Functions: Describe two functions of the parietal lobe.
Parietal Lobe Damage Effects: What are some effects of damage to the parietal lobe?
Occipital Lobe Responsibility: What is the primary responsibility of the occipital lobe?
Occipital Lobe Disorders: Name a disorder that can arise from problems in the occipital lobe.
Visual Perception and the Brain: Which lobe of the brain is most responsible for visual perception?
OTHER IMPORTANT BRAIN AREAS
Mesolimbic pathway
In the brain's centre sits the Mesolimbic/reward pathway, which drives our feelings of motivation, reward and behaviour. Your memory tells you that a particular behaviour will make you feel good; the brain tells the body to initiate the behaviour. Special neurons in the reward pathway release the chemical Dopamine (VTA), which gives you a sense of pleasure (NA). In addition, the reward pathway ensures you repeat the behaviour. It does this by connecting to brain regions that control memory and behaviour. This increases the likelihood that you will repeat the behaviour. When the reward pathway signals the brain’s motor centre, it strengthens the wiring for behaviours that help you achieve your reward. Research shows addictive drugs stimulate the reward circuit in the brain.
THE AMYGDALA
The amygdala is a central structure of the limbic system of the brain that is involved in producing appropriate emotional responses. It is thought that damage to this area can create violent tendencies or incapacity to feel emotion or fear.
BRAIN ANATOMY AND FUNCTION
Anatomical terms of location
Superior and inferior
In anatomical terminology, superior (from Latin, meaning "above") is used to refer to what is above something, and inferior (from Latin, meaning "below") is used to refer to what is below it. For example, in the anatomical position, the most superior part of the human body is the head, and the most inferior is the feet. As a second example, in humans, the neck is superior to the chest but inferior to the head.
Anterior and posterior
Anterior refers to what is in front (from Latin ante, meaning "before") and posterior, what is to the back of the subject (from Latin post, meaning "after"). For example, in a dog, the nose is anterior to the eyes, and the tail is considered the most posterior part; in many fish, the gill openings are posterior to the eyes but anterior to the tail.
Ventral and Dorsal
The dorsal (from Latin dorsum, meaning "back") surface of an organism refers to the back, or upper side, of an organism. If talking about the skull, the dorsal side is the top.
The ventral (from Latin venter, meaning "belly") surface refers to the front, or lower side, of an organism
For example, in a fish. The pectoral fins are dorsal to the anal fin, but ventral to the dorsal fin. These terms are not only used in anatomy but also the study of embryology.
Cranial Caudal and Rostral
Specific terms exist to describe how close or far something is to the head or tail of an animal. To describe how close to the head of an animal something is, three distinct terms are used:
Rostral, from Latin rōstrum ("beak, nose"): situated toward the oral or nasal region, or in the case of the brain, toward the tip of the frontal lobe.
Cranial, from Greek κρᾱνίον (kranion, "skull") or cephalic (κεφαλή (kephalē, "head").
Surface features of the brain:
Sulcus and Gyrus:
Note that the cerebral cortex is highly wrinkled. Essentially, this makes the brain more efficient because it can increase the surface area of the brain and the number of neurons within it. The surface of the cerebral cortex is folded in large mammals, wherein more than two-thirds of the cortical surface is buried in the grooves, called "sulci." It is shown that the development of the cortex coordinates folding with connectivity in a way that produces smaller and faster brains than otherwise would have been possible.
In neuroanatomy
A gyrus (plural: gyri) is a ridge on the cerebral cortex in the brain. It is the raised part of the convoluted brain surface, surrounded by grooves known as sulci (singular: sulcus). The human brain is characterized by a pattern of gyri and sulci, which increases the surface area of the cerebral cortex. This allows for a greater amount of neural tissue to fit within the confines of the skull, supporting more complex cognitive functions.
The gyri are an important part of the brain's anatomy and are involved in various cognitive functions, depending on their location. For example, the precentral gyrus is involved in motor control, while the postcentral gyrus is key to processing somatosensory information (like touch, pressure, and temperature).
This pattern of gyri and sulci is unique to each individual but follows a general pattern that is consistent across humans, allowing for the identification of specific regions and their functions. The intricate folding pattern is a hallmark of the mammalian brain, especially in primates, and is particularly pronounced in the human brain,
Fissure: A narrow slit or cleft, especially one of the deeper or more constant furrows separating the gyri of the brain.
