Substance abuse/ Chapter 3- Brain structure and function

Norepinephrine

A neurotransmitter whose abnormal activity is linked to panic disorder and depression. Similar to epinephrine. Stimulates CNS Ex: amphetamines & cocaine increase the amount of norepinephrine, give a feeling of mental alertness.

Serotonin

Aka 5-hydroxytryptamine (5-HT). Affects mood, sleep, controls body Temperature & appetite, regulates hormones. There are at least 14 different serotonin receptors that scientist know of they have different functions. Ex: LSD mimic the serotonin effect on other cells, slow their activity, resulting in psychedelic visual & emotional effect that is the drug known for.

Drugs & the midbrain

Almost all psychoactive drugs affect the midbrain. this is the region where many types of addiction take place. Human brain is engineered to seek pleasure. Cocaine, amphetamines, and other drugs stimulate the pleasure center in the brain & provide a feeling of euphoria. These drugs also target nucleus accumbens- the reward center. The result is pleasure reward cycle, followed by craving, the person instinctively seeks more causes addiction.

How is the mind made?

At birth, the brain has about one hundred billion neurons (1,000,000,000). Some will die off or languish, others continue to grow. When learning takes place, the connection between neurons strengthens. By age 10, each neuron, on average, will establish 1,000 connections with other neurons; some neurons may have as many as 200,000 connections with other neurons. Total number of interconnections, possible signals= hundred trillion (100,000,000,000,000)= human mind!

Brain- 3 main parts

Brainstem- lowest, most primitive part Midbrain- small part in the middle Cortex- highest, most advanced part

Some examples of neurotransmitters

Close to 100 different neurotransmitters have been discovered. more & more are discovered every day. Psychoactive drugs often resemble neurotransmitters. those that mimic excitatory neurotransmitters are known as stimulants. Those that involve inhibitory neurotransmitters are known as depressants. Other psychoactive drugs do not resemble neurotransmitters directly, but produce their effect by increasing or blocking the release of natural neurotransmitters.

Dopamine

Control appetites for food & sex More dopamine in the system, happier you feel Too much dopamine is believed to be a feature of schizophrenia. May cause disturbance in judgment, aggression, reward seeking behavior, etc. Loss of dopamine is linked to Parkinson's disease. Psychoactive drugs affect dopamine levels in the limbic cortex & the frontal cortex of the brain.

Opioids & Endorphins

Endorphins body's natural opiods. Released during heavy exercise, sex, meditation, prayer, traumatic painful experiences to help body cope. Ex: opioid drugs flood the opioids receptors, produce an exaggerated effect - euphoria, no pain. There are a number of different opioid receptors to which endorphins & opiods can bind.

Drugs & cortex

Ex: LSD and other hallucinogenic drugs seem to affect visual cortex, located at the back of the brain. Addictive drugs affect frontal cortex responsible for insightful judgement. Cause cravings Pleasure seeking behavior. Result poor judgement & irrational behavior.

Gaba & Glutamate

Gaba, gamma- aminobutyric acid, has an inhibitory function; affect memory, relieve pain. Ex: GHB (an illegal depressant drug) imitate GABA, bind to GABA receptors, cause numbness & memory loss. Glutamate- excitatory neurotransmitters, has many functions, including formation of memory. Ex: PCP targets glutamate receptors, causing excitement & memory loss. Together, the most common neurotransmitters in the brain. Both are amino acids ( make up proteins building blocks of life).

Midbrain

Located above the brainstem, midway between the brainstem & the large brain cortex. Referred to an evolutionary extension of the brain. Present in reptiles, aka "reptilian brain" Controls basic functions: survival, instinct, emotions, drives for food & sex. Responsible for regulating emotions (limbic systems), temperature & pain regulation (the thalamus), hormones (hypothalamus), memory (hippocampus), & the sense of reward (nucleus accumbens).

Cerebellum

Located behind the brainstem. Also considered a primitive part of the brain. Present in primordial animals, ex: dinosaurs. Coordinates muscle activity, balance, and vision. Stumbling behavior & jerky eyes seen after use of many Drugs are typical symptoms of these drugs on cerebellum.

Neuron

Nerve cells, aka neurons. Neurons are responsible for all thoughts, sensations, and stimulations in the body. soma, dendrites, axon, myelin sheath, terminal button. Brain is made of massive collection of neurons; they pass signals among themselves. Neurons are alive, constantly undergo changes. The body has neurons reaching to almost every tissue. Pass signals from one to the other. Send & receive signals from the brain.

How do neurons communicate with each other?

Neurons send electrical signals. Action potential: the electrical impulse along the axon is produced by the flow of charged particles, ions through channels in the membrane that cover the axon. When neuron is at rest, it has a negative electrical charge, maintained by high concentration of potassium ions inside the cell. When neuron is stimulated, ion channels open, positively charged sodium ions enter the axon. this flood of positive ions causes the interior of the neuron to flip from negative to positive, forming an electric current. When electrical current reaches the terminal, it stimulates neurotransmitters to be released into the synapse.

Neurons & neurotransmitters

Neurons typically produce one type of neurotransmitter. However, some release more than one type- cascade effect. Ex: serotonin, enkephalin, dopamine= feeling of wellbeing. After sending a signal, each neuron resets itself. the sodium ions are pumped out & the potassium ions dominate the axon, restoring its normal negative charge. Each neuron manufactures its own supply of neurotransmitters. Each neuron can send an electrical signal, reset itself & send another signal up to 400 times/ second.

Excitement & inhibition

Neurons= excitatory+ inhibitory. Excitatory neurons release excitatory type of neurotransmitters, stimulate other neurons. Inhibitory neurons release inhibitory types of neurons, stop transmission of signals.

Brain & neurotransmitters

Nicotine activates dopamine transmission Basal ganglia prefrontal cortex Ventral tegmental area Nucleus accumbens Amygdala Dopamine Gaba Glutamate Nicotinic acetylcholine receptors

Drugs & the brain

Once in the brain, drugs effect different areas. Frontal lobe: Executive functions, thinking, planning, organizing and problem solving, emotions and behavioural control, personality. Motor cortex: movement Sensory cortex: sensations Parietal lobe: perception, making sense of the world, arithmetic, spelling. Temporal Lobe: memory, understanding, language. Occipital Lobe: Vision

Epinephrine

Produced by adrenal gland, located above the kidneys. Responsible for fight or flight response. Increases heart rate, blood moves from digestive organs to muscles, lungs open to breath faster, appetite is suppressed. Ex: amphetamines mimic epinephrine functions.

Acetylcholine

Stimulates muscles & glands. Responsible for production of saliva, tears, sweat & other secretions. Ex: nicotine stimulates one type of acetylcholine receptors.

Cortex

The highest, most developed part of the brain. Folds & folds of gray matter. Makes up the bulk of the volume. Distinguishes us from other animals. Responsible for language, reasoning & judgment intellect.

Synaptic cleft

The tiny space between the surface of one neuron terminal and the surface of the next neuron is called a synapse or synaptic cleft. 1/1,00th the width of a human hair.

Brain

Ventricles ( Fluid filled spaces) Cerebrum Meninges Skull Cerebellum Brainstem (pons, medulla) Spinal cord Five main structures of the brain: midbrain, cerebellum, cortex, spinal cord, medulla.

Brainstem

located at the bottom and extending into the spinal cord. Most primitive. Present in fish & lower animals. Serves to regulate basic bodily functions, ex: breathing & sleep. Opiates are believed to have an effect on brainstem. If overdoses occurs, may interfere with breathing, may potentially be fatal.