The 19th century marked the existence of psychology as a separate branch of science. Modern psychology has grown to the extent that any information about thoughts, emotions, and activities of human beings and other organisms can now be gathered in a scientific manager, and studies can be conducted on them. Even though it is a science which has been subjected to continuous changes, one sees a lot of difference in opinion, among the educated, about the various areas psychology handles and the idea of the human mind. There are also people who believe that the brain consists of a conscious mind, a subconscious mind, and an unconscious mind.
The Psychological Approach of Sigmund Freud
In this matter, many people tend to cite the psychological approach of Sigmund Freud, the psychiatrist who lived in the 19th century. Freud formulated his theories from his studies centered on human beings. He even included his thoughts for the study. He inferred that the thoughts, memories, and desires lying underneath the conscious understanding belong to the sub-conscious mind and that the unconscious mind is the actual reality.
The unconscious mind influences human behaviour. Freudian psychology’s position is that the dreams reveal the emotions and feelings lying in the unconscious mind of individual and psychological problems are due to the struggles within the unconscious mind.
The Behavioural Science
In the 20th century, John C. Watson and his friends said that all Freudian theories are meaningless. The branch called behavioural science, which they presented, negated all the ideas of mind, conscious experiences, and so on. According to them, the only things that can be observed are the external behavioural patterns. Human beings cannot precisely describe what is happening in their minds. So, as they say, evaluation is done for external behaviour. For almost 50 years behavioural science had a dominant control in psychiatry. The influence of behavioural sciences is quite evident in our educational system and the methods of propagation of ideas.
It is during 1960-70 that the cognitive sciences evaluated several perspectives based on behavioural sciences as somewhat immature. Here are few defects in that approach, as pointed out by cognitive psychologists like Aaron T Beck, Albert Bandura, John R. Anderson, Steven Pinker, Noam Chomsky, Howard Garner, Bruner, etc.
All the inferences in behavioural sciences are from experiments conducted on animals. The stimuli and responses of the animals are incomparable with that of the human beings with highly developed mental functions. This is because all responses of human beings have a social and cultural basis.
Advancement of Neuroscience
Neuroscience advanced significantly during the 1970-80s. A new field emerged that allowed anatomists, biomedical scientists, psychiatrists, physiologists, endocrinologists, and neurologists to work together. The new field called neuroscience found the core connections between the working of the brain and human behaviour.
The Brain Activity
The activities inside the brain cells result in our behavioural traits, memories, and all other expressions of emotions. There are more than 100 trillion neurons connections in the brain. In a specific manner, our brain stands as a collective of various parts functioning. Each part of the brain plays a significant role in a particular function and insignificant role in various others. Some of the functions are dependent only on one specific part. Injuries occurring to both sides of the brain affects certain functions. What functions are affected are identified upon which side of the brain was injured. A combined analysis becomes a necessity as the brain system and nerve functions are connected.
The advanced machines available today support the neuroscientists to observe the brain function of a person while they are thinking. Exact observation and studies are possible with the help of technologies like Positron Emission Tomography (PET), Regional Cerebral Blood Flow (RCBF), Functional Magnetic Resonance Imaging (fMRI), etc.
The human brain is the most complex of all the organs among the organisms living on the earth. It is the brain that makes the survival possible for human beings. The brain has the entire human body under its control by watching and regulating the activities of the muscles, glands, and the sensory system.
The brain coordinates all the activities happening in the human body and provides directions to the various groups of cells to perform their activities. The primary responsibility of the brain is to control the movements of various muscles in the human body. It is the brain that regulates the movements through expansion and contraction of the muscles in the hands and legs. It also moves the muscles in the stomach, and the liver to help metabolic activities and digestion and produces hormones from the glands when required.
The sensory system carries messages to the brain by receiving signals from the surroundings through skin, eyes, ears, nose, and tongue. The Autonomic Nervous System collects the information within the body.
The significant advancements in Genetics and Neuro Imaging Technology in the 21st century led to research that helped unravel the brain’s complex activities.
The human brain is not the largest one, and this might not seem convincing. Our brain weighs between 1.2-1.5kg, but an elephant’s brain weighs between 4-5kg, and the whale’s brain weighs up to 9kg. This is one of the many reasons why scientists often resort to it, saying that our brain must be extraordinary to explain our cognitive abilities. It must be unusual, an exception to the rule. Theirs may be bigger, but ours is better, and it could be better. For example, in that, it seems larger than it should be, with a much larger cerebral cortex than we should have for the size of our bodies. So that would give us the extra cortex to do more interesting things than just operating the body. That’s because the brain’s size usually follows the body’s size to say our brain is larger than it should come from comparing ourselves to great apes. Gorillas are 2-3 times larger than us, so their brains should be larger than ours; instead, it happens the other way around. The human brain is three times larger than a gorilla’s brain.
The human brain also seems unique in the amount of energy that it uses. Although it weighs only two percent of the body, it alone uses 25% of all the energy that our body requires to run per day. If we knew how many neurons each brain create, we could do the math. And it turns out that both humans and other brains cost about the same, an average of six calories per billion neurons per day. The total energy cost of a brain is a simple linear function of its number of neurons, and it turns out that the human brain costs just as much energy as you expect. The human brain cost so much energy because it has a massive number of neurons. Because we are primates with many more neurons for given body size than any other animal, the relative cost of our brain is enormous, but because we are primates, not because we are unique.
The human brain has the most neurons of any brain, regardless of its size, especially in the cerebral cortex. How many neurons does the human brain have, and how does that compare to other animals?
No one has ever counted the number of neurons in the human brain or any other brain. But we have, on average, 86 billion neurons, 16 billion of which are in the cerebral cortex. If you consider that the Cerebral Cortex is the seat of functions like awareness and logical and abstract reasoning and that 16 billion is the most neurons that any cortex has, this is the simplest explanation for our remarkable cognitive abilities. But just as important is what the 86 billion neurons mean. The relationship between brain size and the number of neurons is not something that we can explain mathematically.
The human brain is not a giant rat brain. Compared to a rat, we might seem extraordinary. Yes, but that’s not a fair comparison, given that we know that we are not rodents. We are primates, so the correct comparison is to other primates. And there, if you do the math, you find that a generic primate with 86 billion neurons would have a brain of about 1.2 kg, which seems just right, in a body of something around 66kg, if great apes are more massive than we are, why don’t they have a larger brain than we do, with more neurons? It becomes easier to reason out when we realize how expensive it is to have a lot of neurons in the brain. Apes can’t afford the energy for both a large body and a large number of neurons. The math was done. On the one hand, it was calculated how much energy a primate gets per day from eating raw foods, and on the other hand, how much energy a body of certain size costs and how much energy a brain of a certain number of neurons costs. The combinations of body size and the number of brain neurons that a primate could afford if it ate a certain number of hours per day were looked into.
It was found that, as neurons are so expensive, there is a trade-off between body size and the number of neurons. A primate that eats 8 hours per day can afford the most 53 billion neurons, but its body cannot be any bigger than 25kg.
What about us? With our 86 billion neurons and 60-70kg of body mass. We should have to spend over 9 hours per day every single day feeding, which is not feasible. If we ate like a primate, we should not be here. The human brain grew to become so large so fast in evolution.
So what is the human advantage? We have the largest number of neurons in the cerebral cortex, which is the simplest explanation for our remarkable cognitive abilities. And what is it that we do that no other animal does.
The human being has two types of nervous systems:
- Central Nervous System: The brain and the spinal cord constitute the central nervous system
- Peripheral Nervous System: The brain nerves and the nerves of the spinal cord together form the peripheral nervous system.
The entire nervous system, including the brain, has been vested with the most complex responsibility of leading the physical and mental activities of the body. The nervous system regulates the activities of the body through muscles and glands.
The brain includes the Cerebral hemispheres, the Brain Stem, and the Cerebellum. The organization structure of the brain contains the cerebral hemispheres, Cerebellum, Brain Stem, Thalamus, and Hypothalamus. The Cerebellum and the brain stem are located as a continuum to the cerebral hemispheres, while Thalamus and hypothalamus are located in the interior. The cerebral hemispheres are also called the neo-brain.
The brain can be divided into two: the upper brain and the lower brain. The two hemispheres of the brain, namely the Cerebral hemispheres are the parts of the Upper brain. The brain stem and Cerebellum, lying on both of its sides, constitute the lower brain. Middle brain, Medulla Oblongata, Pons, – these three parts together form the Brain stem. It is the lower brain that regulates the unconscious activities in the body. Breathing, heart rate, blood pressure, emotional stress, etc. are functions of the lower brain. The nervous system’s activities happen in the upper brain, lower brain, and spinal cord nerves.
The left hemisphere controls the right side, and the right hemisphere controls the human body’s left side. The nerve fibers called Corpus Callosum to connect the two hemispheres.
The left brain and right brain lie inside the cortex. The neural nerves lie below the cortex, along with the white matter that contains brain cells. The cortex analyses all information received through the sense organs—human intelligence, artistic and other abilities, memory, caution, etc. all originate from the cortex.
The Brain Lobes
The cerebral hemispheres have four lobes – frontal lobe, parietal lobe, occipital lobe, and the temporal lobe. Each of these lobes has different functions to perform.
The frontal lobe lies on the front, the parietal lobe on the rear end, and the temporal lobe lies below the central fissure on the outer surface of the brain, called the Central Sulcus. The motor cortex controls the conscious movements of the body. The Sensory Cortex lies anterior to the parietal lobe, which is located posterior to the central sulcus.
The sensory cortex accepts the sensory information from Thalamus and exchanges the same with the Brain Stem and the Spinal Cord. The Visual Cortex lies in the Occipital lobe. The Auditory Cortex and the Olfactory Cortex lies in the Temporal Lobe. These centers in the cortex accept and process the nerve impulses received through the sense organs.
Autonomic Nervous System
The nervous system, which controls the reflex actions in the body, is called the Autonomic Nervous System. This doesn’t fall under the conscious control of the brain. Yet the glands and the nerves in the blood circulation system and digestive system are under its control. Autonomic Nervous Systems regulate the breathing, metabolism, heart rate, and secretion of the endocrine glands. The two subcategories called Sympathetic Nerves and Parasympathetic Nerves, are located in the Autonomic Nervous System. The Sympathetic Nerves stimulate the breathing, heart rate, and blood pressure and contract the soft tissues. The parasympathetic nerves calm down the body. It is the Sympathetic Nervous System that prepares the body to fight emergencies.
The human body has almost ten thousand crore neurons. It is the basic unit of the organizational and moral structure of the nervous system. The cell body and the thin fiber-like structures extending from it together form a neuron. Among these fibers, the longer ones are called Axons, and the shorter ones are called Dendrites. One axon and several dendrites arise from a neuron. The stimuli from the nervous system reach the muscles and glands through electric signals called impulses. Synapse is the bridge that connects two nerve cells. The impulses flowing from the axon, after crossing the Synapse, reach the dendrite through a chemical called the neurotransmitters. The job neurotransmitters are to transmit the nerve impulses to the neighbouring nerve cells. The neurotransmitters are stored in the Synaptic bulbs. The synaptic build is the one seen in the bubble at the branching end of the axon. The motion displacement created by the electric current in the brain makes the neurotransmitters flow out of the synaptic bulb. Hundreds of neurotransmitters have been identified. Acetylcholine, Glutamate, Gamma Amino Butyric Acid, Glycine, Dopamine, Norepinephrine (noradrenalin), Epinephrine (Adrenaline), Serotonin and Histamine are some of the essential neurotransmitters. The dendrites from each nerve cell gather information from innumerable nerve fibers. One nerve cell is connected to around ten thousand other nerve cells. It has been calculated that a human brain has approximately more than 100 trillion synaptic links (1 trillion – 1 lakh crores). It is an extensive neural network that exists in the brain.
These are the other cells in the brain. The glial cells play a role in establishing the synaptic connection between the neurons and to remove any blocks in the flow of the chemical transmitters through the synaptic cleft.
The primary responsibility of the nervous system is to receive information from the surroundings and inside the body and to respond to them accurately. Several axons combine to form the nerves. Sensory Nerves carry information to the brain and Motor Nerves that carry the information from the brain to the muscles and set them into motion.
The lies between the brain and the cortex. Thalamus is the Relay center for all the Motor and Sensory messages entering and exiting the brain. Thalamus has a significant role in executing functions such as memory, consciousness, caution, and pain sensation.
Hypothalamus is the link that connects and coordinates the two essential control systems in the body – the brain and the endocrine glands. It is the small portion below the brain. The pituitary gland, which supervises all the endocrine glands, is under the control of the Hypothalamus. The Autonomic Nervous System is also under the supervision of the Hypothalamus. The center for hunger, thirst, and temperature is in the Hypothalamus.
Ganglia is a collection of nerve cells in the brain. Basal Ganglia is interconnected with the Cerebral Cortex, Thalamus, and the Spinal Cord. Basal Ganglia play a role in the functioning of complex physical and mental phenomenon like learning, cognition, and emotional expressions.
The parts of the brain on either side of the Thalamus together form the Limbic system. The limbic system is the center for emotions, smell, and long term memories.
The pituitary gland is seen in a capacity called Sella Turica found below the skill at the base of the brain. The pituitary gland has authority over all the endocrine glands in the human body.
There are 12 pairs of Cranial Nerves. The cranial nerves and their functions are:
- Olfactory: smell
- Optic: vision
- Oculomotor: movement of eyes and the pupil
- Trochlear: movement of the eyes
- Trigeminal: sensation in the face
- Abducens: movement of eyes, excreting salica
- Facial: movement of the facial muscles
- Vestibulo Cochlear: hearing, body balance
- Glosso Pharyngeal: swallow, taste
- Vagus: heart rate, digestion
- Accessory: movement of the head
- Hypoglossal: movement of the tongue.
The advancement of neuroscience helped us to understand every function of our brain, including the study of brain neurons. In fact, neuroscientific psychiatry is the new generation’s brain-based understanding of human behaviour in health and disease. This field emerged in the last 10-15 years with the help of the latest technologies such as neurogenetics, brain imaging, and a combination of medicine and cognitive neuroscience. It has swiftly replaced the view on psychiatric conditions as well as their treatment.