Human Brain

 Excerpts from: http://www.midbrainpower.in 

Parts and functions of the human brain

Mental health conditions are complex medical conditions just like cancer and diabetes. Even though identical twins share the same genes and many of the life same events, only one may develop cancer, diabetes or any mental health condition.

The gray matter of the brain is made up of neurons which are cells in the brain that send and receive messages, glial cells that support and protect neurons and capillaries that provide blood supply. A baby is born with more neurons than he or she will need, the cells then begin the process of elimination and rewiring referred to as pruning. The environment is believed to play a major role in determining what connections are strengthened as the brain matures. Thus the important role of epigenetics.

The brain is divided into 3 parts

(Forebrain)

  1. Cerebrum
  2. Thalamus
  3. Hypothalamus

(Midbrain and Hindbrain)

  1. Cerebellum/Midbrain
  2. Pons/Hindbrain
  3. Medulla olongata/Hindbrain

The Cerebrum: The cerebrum or cortex is the largest part of the human brain, associated with higher brain function such as thought and action. The cerebral cortex is divided into four sections, called “lobes”: the frontal lobe, parietal lobe, occipital lobe, and temporal lobe.

Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem-solving

Parietal Lobe- associated with movement, orientation, recognition, perception of stimuli

Occipital Lobe- associated with visual processing

Temporal Lobe- associated with perception and recognition of auditory stimuli, memory, and speech

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.

A deep furrow divides the cerebrum into two halves, known as the left and right hemispheres. The two hemispheres look mostly symmetrical yet it has been shown that each side functions slightly different than the other. Sometimes the right hemisphere is associated with creativity and the left hemisphere is associated with logic abilities.

The corpus callosum is a bundle of axons which connects these two hemispheres. Nerve cells make up the gray surface of the cerebrum. White nerve fibers underneath carry signals between the nerve cells and other parts of the brain and body. The neocortex occupies the bulk of the cerebrum.

Hypothalamus: The hypothalamus region of the brain controls mood, thirst, hunger, and temperature. It also contains glands which control the hormonal processes throughout the body.
Thalamus: The Thalamus is located in the center of the brain. It helps to control the attention span, sensing pain and monitors input that moves in and out of the brain to keep track of the sensations the body is feeling.

Cerebellum
This is commonly referred to as “the little brain,” and is considered to be older than the cerebrum on the evolutionary scale. The cerebellum controls essential body functions such as balance, posture, and coordination, allowing humans to move properly and maintain their structure.
Limbic System: The limbic system contains glands which help relay emotions. Many hormonal responses that the body generates are initiated in this area. The limbic system includes the amygdala, hippocampus, hypothalamus, and thalamus.
Amygdala:  The amygdala helps the body responds to emotions, memories, and fear. It is a large portion of the telencephalon, located within the temporal lobe which can be seen from the surface of the brain.
Hippocampus: This portion of the brain is used for learning memory, specifically converting temporary memories into permanent memories which can be stored within the brain. The hippocampus also helps people analyze and remember spatial relationships, allowing for accurate movements. This portion of the brain is located in the cerebral hemisphere.

Brain Stem
All basic life functions originate in the brain stem, including heartbeat, blood pressure, and breathing. In humans, this area contains the medulla, midbrain, and pons. This is commonly referred to as the simplest part of the brain, as most creatures on the evolutionary scale have some form of brain creation that resembles the brain stem.

The brain stem consists of midbrain, pons, and medulla.
Midbrain: The midbrain, also known as the mesencephalon is made up of the tegmentum and tectum. These parts of the brain helps regulate body movement, vision, and hearing. The anterior portion of the midbrain contains the cerebral peduncle which contains the axons that transfer messages from the cerebral cortex down the brain stem, which allows voluntary motor function to take place.

Pons: This portion of the metencephalon is located in the hindbrain, and links to the cerebellum to help with posture and movement. It interprets information that is used in sensory analysis or motor control. The pons also creates the level of consciousness necessary for sleep.
Medulla oblongata: The medulla or medulla oblongata is an essential portion of the brain stem which maintains vital body functions such as the heart rate and breathing.

Neurotransmitters:

Excerpts from http://thebrain.mcgill.ca/

A synapse is the junction point between two neurons.

A nerve impulse can also be transmitted from a neuron to neuron, sensory receptor cell to a neuron, or from a neuron to a set of muscles to make them contract, or from a neuron to an endocrine gland to make it secrete a hormone. In these last two cases, the connection points are called neuromuscular and neuroglandular junctions.

In a typical chemical synapse between two neurons, the neuron from which the nerve impulse arrives is called the presynaptic neuron. The neuron to which the neurotransmitters (chemical messengers) bind is called the postsynaptic neuron.

A presynaptic neuron has several specialized structures that distinguish it from a postsynaptic neuron.

This terminal button also contains spherical vesicles filled with neurotransmitters. These neurotransmitters are secreted into the synaptic gap by a process called exocytosis.

This section describes a few of the best-known neurotransmitters that are involved in many functions in both the central and the peripheral nervous systems. Apart from acetylcholine, they all belong to the family of amines or amino acids.

Acetylcholine is a very widely distributed excitatory neurotransmitter that triggers muscle contraction and stimulates the excretion of certain hormones. In the central nervous system, it is involved in wakefulness, attentiveness, anger, aggression, sexuality, and thirst, among other things.

Alzheimer’s disease is associated with a lack of acetylcholine in certain regions of the brain

Dopamine is a neurotransmitter involved in controlling movement and posture. It also modulates mood and plays a central role in motivation and reward.

The loss of dopamine in certain parts of the brain causes the muscle rigidity typical of Parkinson’s disease.

The dopamine hypothesis of schizophrenia or the dopamine hypothesis of psychosis is a model that attributes symptoms of schizophrenia (like psychosis) to a disturbed and hyperactive dopaminergic signal transduction.

Glutamate is a major excitatory neurotransmitter that is associated with learning and memory.

It is also thought to be associated with Alzheimer’s disease, whose first symptoms include memory malfunctions.

Research has shown the importance of glutamate receptors, specifically N Methyl D aspartate receptors (NMDARs), in addition to dopamine in the etiology of schizophrenia.

Glutamate imbalances appear to cause abnormal functioning in dopamine.

Norepinephrine is a neurotransmitter that is important for attentiveness, emotions, sleeping, dreaming, and learning. Norepinephrine is also released as a hormone into the blood, where it causes blood vessels to contract and heart rate to increase.

Norepinephrine plays a role in mood disorders such as manic depression

Serotonin contributes to various functions, such as regulating body temperature, sleep, mood, appetite, and pain

Depression, suicide, impulsive behavior, and aggressiveness all appear to involve certain imbalances in serotonin