Physiology of Emotions & thoughts

On the neuronal level there's no difference between thoughts and emotions. They are both expressions of electric and chemical processes in and between the nerve cells. However, emotions and thoughts are clearly distinguishable from each other and it's the various processes in the nervous system that make up the difference between them.


The nerve cells are the units making up the nervous system, which makes our body perceive, feel and respond to the world around us. It is a complex system consisting of two main parts: a sensory and motor division.

1. Sensory division

The sensory part of the nervous system consists of nerve cells that sense the outside world. They react to impulses (vibrations) from without and transform these into electric signals via specialised organs: skin and inner organs react to mechanical pressure (touch), eyes react to light, ears react to air vibrations, nose reacts to air molecules, and tongue reacts to tastes. The 5 senses gather information from the environment and transform them into signals that run along the nerves for further processing in the spinal cord and the brain.

2. Motor division

The motor division consists of nerve cells which receive signals back from the brain and spinal cord to cause a mechanical or chemical effect in targeted organs, such as muscle contraction or relaxation, increase or decrease of heart rate, release or reduction of hormones in blood etc. The motor division makes the body move and process the orders from the brain and the spinal cord.

The motor division in turn is divided into two sub-branches: somatic and autonomic divisions.

2.1. Somatic Division

The somatic system consists of motor nerves that control our muscles and glands and which are subject to our voluntary action. It is the part that makes us move our limbs and perform various kinds of conscious actions with our bodies. It obeys our self-determined control.

2.2. Autonomic division

The autonomic system performs various vital functions which are outside our conscious control, but necessary for the survival of the organism, such as heart-beat, breathing, digestion etc. These actions are unconscious and involuntary, but they are crucial for sustaining the vitality of the body. They are so important that they function automatically without our attention directing them. The autonomic nervous system keeps us alive, leaving it to the somatic system to make the conscious decisions in our daily lives.

Nerve Cells

The units of the nervous system are the nerve cells. They receive impulses and forward them as electrical currents along the body. The nerve cells, although interconnected, don’t really touch each other. Instead, they are separated by small gaps which contain many little vesicle sacks filled with molecules of certain types. These molecules are called neurotransmitters, and there’s many different kinds, depending on their structure and the task they perform. All processes of the organism that pertain to consciousness (inner experience) are a result of the movement of the electric and chemical currents through or between the nerves.

Central system: spinal cord & brain

Any information coming in from the senses via nerve cells reaches the central nervous system which consists of the spinal cord and the brain. They process the information by integrating them into the existing nervous structures.

The spinal cord controls automatic movements which aim at protecting the body from danger. When a hand touches a hot herd, the muscles will withdraw the hand immediately to protect the hand from burning before the brain even realises what is happening. The spinal cord recognises the danger while the impulse is still on the way to the brain and sends a signal back to the hand to withdraw, while the brain is still occupied with decoding the signal. The spinal cord is the cause for all the reflexes that help our body protect itself from dangerous situations.

The brain is the centre controlling and managing the activities of the organs through electric and chemical signals via nerve cells and through hormonal molecules via glands and blood. For anything to become part of consciousness it must pass through the brain. It is in the higher regions of the brain where conscious experience is processed.

It's easy to understand the different parts of the brain by dividing it into three major parts.

We don't use only 10% of the brain. Even simple tasks make nearly every brain region lighten up. The brain requires 20% of the body’s energy.

From the evolutionary point of view the oldest parts of the brain are at the bottom and back of the head (reptilian brain) which altogether regulate vital functions and processes which don’t require thinking.

The youngest portion of the brain is the cortex (cerebrum) which makes us into human beings. This is the place where conscious thinking, learning, voluntary movements, planning, comprehension, language, concentration and consciousness take place, i.e. all the cognitive functions typical of humans.

3 parts of the brain

1. Reptilian Brain: reflexes & instincts

Human capabilities derive from brain structures that developed from older parts of the brain that can be found in primitive animals such as reptiles. Reptiles have brains responsible for survival functions, such as eating, breathing, resting etc. That brain is the inner core anchored by the brain stem. The functions here happen automatically and without any conscious effort. The thalamus of the reptilian brain takes in sensory information related to seeing, hearing, touching and tasting. There are also parts responsible for arousal such as sleeping and walking, pain, non-verbal learning, memory and coordination of movements.

2. Limbic System: emotions & feelings

More complex brain structures let higher animals anticipate, learn, remember and, above all, feel. This newer part of the brain is the limbic system which evolves around the older brain structures. Limbic system consists of the amygdala, hypothalamus, and hippocampus. Its main function is to experience emotions. Whatever passes through the limbic system is tinted with an emotion or feeling.

3. Cerebrum: reason & logic

The most advanced part of our brain, the grey matter, is what makes us human. It makes up 85% of our brain weight and provides us with the ability to speak, think, learn, remember and perceive the way we humans do. It is divided into the left and right hemispheres. In the cerebral cortex covering both hemispheres you find association areas which deal with interpreting and integrating sensory input and linking it with memories.

Integration of information

All information about the environment flows from the senses to the spinal cord and the brain where the information gets integrated into the internal structure. All the nerves are interconnected with each other building vast networks along which electric and chemical signals can flow. The nervous system re-wires itself constantly as it learns based on conscious and unconscious experience. In this way the release of certain molecules can be strengthened or inhibited which is the cause of establishing and overcoming of habits.

Every information from the environment needs to be integrated into the nervous networks of the brain, which represent the inner mental structure of our consciousness. Loose data has no meaning for us, unless it relates to other bits of information in our brain.

This connecting of information to other pieces of information on the neuronal level is the process of association, upon which all thinking and perception is based. We comprehend and understand the world around us because our inner mental structure (networks of nerve cells in the brain) can establish immediate connections between various bits of information. In this way we know what we are, what is happening and how things work.


In a nutshell

Our inner experience is a manifestation of a complex interplay of electrical and chemical molecules flowing in and between the nervous cells. Their structure defines their functions and the quality of experience that they deliver to the consciousness.