Neurobiology and the Brain

The human brain is the control center for all physical and psychological processes. A basic knowledge of brain structures and biochemical processes is helpful for understanding mental disorders such as borderline personality disorder.

Neural Networks Structure and function of nerve cells, synapses and how memories are formed

Brain Biochemistry Neurotransmitters, hormones and nutrients for the brain

Stress Response The HPA axis and effects of chronic stress

The Human Brain - Structure and Components

Cortex (Neocortex)

The cerebrum is the seat of logic, reason, motor association areas and projection fields. It is the center of all sensory perceptions.

Hypothalamus

Part of the limbic system, which consists of the hypothalamus, thalamus, hippocampus and amygdala - the seat of feelings and emotions. The hypothalamus is part of the diencephalon and the highest center of the autonomic (vegetative) nervous system.

Here the coordination and integration of all vegetative body functions and the hormone balance takes place:

• Carbohydrate metabolism
• Water and salt balance
• Thermal equilibrium
• Sexual functions
• Motivational reinforcement (hunger, sexuality)

Heart rate and respiration are also indirectly influenced via the nuclei of the medulla.

Pituitary Gland (Hypophysis)

The pituitary gland is approximately bean-sized and an endogenous gland. It is directly connected to the hypothalamus and forms a functional unit - the central interface between neural and hormonal regulatory processes.

Important hormones of the pituitary gland:

Anterior Lobe	Posterior Lobe
Growth hormone (STH)	Oxytocin
Follicle-stimulating hormone (FSH)	Vasopressin
Luteinizing hormone (LH)
Prolactin (HPr)
Thyrotropin (TSH)
Adrenocorticotropin (ACTH)

Thalamus

Part of the limbic system. The thalamus comes from the Greek and means “chamber, cavity.” It is the dorsal nuclear region of the diencephalon. All sensory pathways converge here, where they are emotionally colored before becoming conscious experience (anger, warmth, etc.) in the cerebrum.

The electrical activity of the cerebrum and thus the attention and wakefulness functions are controlled by the thalamus.

Prefrontal Cortex

The prefrontal cortex contains the frontal lobe, which is divided into left and right. Responsible for:

• Cognitive activities such as planning
• Decision-making
• Goal-setting
• Connecting present and future through planful action

The executive functions of the prefrontal cortex

It communicates closely with the limbic system via the dopamine pathways. Damage to the prefrontal cortex can have devastating psychological effects.

Hippocampus

Parts of the hippocampus also belong to the limbic system. It plays a central role in memory consolidation - specifically for:

• Encoding and transferring information from short-term to long-term memory
• Retaining spatial orientations

Important

An elevated long-term release of glucocorticoids (stress hormones) leads to the destruction of hippocampal neurons. The hippocampus, when fully functional, has a braking influence on the release of Corticotropin Releasing Hormone (CRH).

Amygdala (Almond-Shaped Body)

The amygdala is the decisive guardian in controlling emotions and has a decisive influence on emotional memory.

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The Limbic System - Seat of Emotions

The limbic system is the central structure for our emotions. It consists of:

• Hypothalamus
• Thalamus
• Hippocampus
• Amygdala
• Nucleus accumbens

The Reward System

In 1954, the American neuroscientists James Olds and Peter Milner discovered the reward system in the brain. In experiments with rats, they showed that the animals pressed a lever to administer electrical stimulation to the reward system - even accepting painful electric shocks to do so.

The reward system essentially consists of three elements:

1. Nucleus accumbens - part of the limbic system
2. Ventral tegmental area in the midbrain
3. Prefrontal regions of the cerebral cortex

Key Role of Dopamine

The nucleus accumbens is the central switching station of the reward system. It contains nerve cells that use the neurotransmitter dopamine for signal transmission. Dopamine is the chemical master switch of desire and an important element in the development of addiction.

Neurotransmitters and Addiction Development

The dopamine system receives support from other messenger substances:

• Endogenous opioids (endorphins)
• Cannabinoids (anandamides)

Both opiate drugs and endogenous opioids bind to opiate receptors in the nucleus accumbens. Studies on bungee jumpers showed a 200-fold increase in beta-endorphins during and immediately after the jump.

Addictive substances such as cocaine, amphetamines, or heroin release increased amounts of dopamine in the reward system.

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Neural Networks

How Memories Work

A specific face corresponds in the brain to a very specific combination of many nerve cells - a network structure that fires together in response to a signal (trigger). This can be triggered by someone who walks, smells, or looks similar, without it needing to be consciously perceived.

Structure of a Nerve Cell

A biological nerve cell consists of:

Component	Function
Soma	Cell body
Dendrites	Short conductors (approx. 0.4 mm), through which stimuli enter the nerve cell
Axon	Conductor for transmitting cell activity to other cells (mm to several meters)
Synapses	Contact points between axons and dendrites

When the soma is stimulated beyond a certain threshold, the cell generates a brief electrical impulse (spike), which is transmitted by the axon to other cells.

Synapses and Neurotransmitters

Synapses are chemical contacts that respond to a spike by releasing certain ions (neurotransmitters):

• Acetylcholine
• Serotonin
• Dopamine
• Adrenaline
• Noradrenaline

These are released from synaptic vesicles into the synaptic cleft and taken up by the subsequent neuron. They dock at corresponding receptors and in turn trigger electrical activity.

Medication Effects

Serotonin reuptake inhibitors (SSRIs), MAO inhibitors and other psychotropic medications intervene in the synaptic cleft and delay the reuptake of certain transmitters. These are thus available longer and counteract depression.

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Biochemistry and Stress Response

The Three Happiness Messengers

Three substances are primarily responsible for your well-being:

1. Serotonin
2. Dopamine
3. Noradrenaline

During stress, the two main substances adrenaline and cortisol are released, with cortisol having a regulatory function on adrenaline.

The Stress Axis (HPA Axis)

In danger, the thalamus activates the amygdala (emotional guardian). This activates CRH (Corticotropin-Releasing Hormone) via the hypothalamus:

HPA Axis: Hypothalamus (CRH) → Pituitary (ACTH) → Adrenal glands (Glucocorticoids/Cortisol)

Effects of Chronic Stress

The body’s stress response - From the hypothalamic-pituitary-adrenal axis to the organs

The body’s stress response - Effects on the immune system

During prolonged dis-stress, the following are activated:

• Adrenaline, noradrenaline
• Rise in blood sugar levels
• Cortisol
• Increase in blood pressure
• Activation of the sympathetic nervous system
• Increase in thyroid function
• Immune system with phagocytes

Warning: Chronic Stress

During prolonged dis-stress, the immune system can collapse. An excessively prolonged elevated cortisol level damages the hippocampus, which can lead to memory gaps, sleep disturbances and uncontrolled flashbacks - similar to post-traumatic stress disorder.

Consequences of Chronic Dis-Stress on the Body

Organ	Effect
Brain	Certain cytokines destroy nerve cells. Elevated cortisol damages the hippocampus
Pancreas	Cortisol reduces insulin effectiveness, can lead to diabetes
Stomach	Noradrenaline constricts blood vessels of digestive organs (ulcers, inflammation)
Muscles	Increasingly consume muscle protein, muscles shrink
Blood vessels	Chronically elevated blood pressure damages vessels (arteriosclerosis, heart attacks)
Reproductive organs	Cortisol inhibits hormone synthesis (impotence, menstrual disorders)

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Nutrition for the Brain

Important Nutrients

The raw material for positive feelings are three amino acids:

• Phenylalanine - precursor of tyrosine, dopamine, noradrenaline
• Tyrosine - converted into dopamine
• Methionine - involved in conversion to noradrenaline

Recommendations During Stress

To avoid:

• Pasta, polished rice, pizza
• Sugar and sweet drinks
• Alcohol
• Potatoes

To prefer:

• Complex carbohydrates during the day (whole grain products, fruit, vegetables)
• Protein with vitamin C in the evening
• B vitamins (especially in brewer’s yeast)
• Magnesium, zinc, manganese, calcium

Tip for Better Sleep

Tryptophan is the raw material for serotonin and melatonin (sleep hormone). Tryptophan-rich foods: milk, eggs, nuts, cheese, peas.