1. Drugs and Our Society Drugs and the Brain Part 6

2. The Nervous System 1. The nervous system can be divided into two parts: -the peripheral nervous system (PNS) and - the central nervous system (CNS) 2. The peripheral is made up of the somatic nervous system and the autonomic systems 3. Somatic nervous system -nerve cells that interact with the external environment -consciousness / voluntary reactions -it is made up of sensory nerves (eyes / ears / skin / tongue (vision / hearing / touch / taste)

3. Nervous System, cont -sends sensory information to the CNS -pinch your skin / speck of dust in the eye -sends movement information back out -twitch of the arm / blink or tearing of eye 4. Autonomic nervous system -internal environment is monitored and controlled -operates the visceral (involuntary) body functions -it is an unconscious reaction -heart rate / blood pressure / breathing

4. Nervous system, cont 6. Central nervous system -consists of the brain and spinal cord -spinal cord functions primarily as a relay station -it transmits information from sensory nerves to the brain -it carries motor commands from the brain to the muscles 7. The brain -it is a complicated structure -made up of nuclei and fiber tracts

5. Nervous system, cont -it contains 100 billion neurons -these are the messengers in the brain -they transmit information via chemical and electrical processes -they are considered neurotransmitters, such as serotonin / dopamine / nor epinephrine 8. It is capable of storing and analyzing more information than today’s supercomputers -it is not as fast, but can deal simultaneously with 1000’s of pieces of input

6. Nervous system, cont 9. The brain has a rich supply of blood from 4 major arteries -drugs circulating in the blood have a fast access to the brain 10. Blood-brain barrier -capillaries in the brain are different -the cells are tightly joined -this keeps many drugs from reaching the brain 11. For a drug to be psychoactive, the molecules must be capable of passing this barrier

7. Nervous system, cont 12. Drugs are carried to the brain by the blood supply -how do they know where to go -they don’t -drugs go everywhere 13. Certain drugs impact certain neuron cells -LSD acts on serotonin in the brain -where the psychoactive drugs are similar to the molecular structure of neuron chemicals -the drug molecules interact with the brain chemistry

8. Parts of the Brain 1. There are 3 primary parts to the brain: -the forebrain / midbrain / hindbrain 2. Hindbrain -controls breathing / heart rate (respiration) / and digestion -it is highly sensitive to opiates / alcohol / barbiturates / and depressants 3. Midbrain -sensory and motor reflexes -processing of pain information

9. Parts of the brain, cont 4. Forebrain -feeding / drinking / sexual behavior -organizing emotional behavior -visual / auditory / sensory 5. The brain is further broken-down into the: -cortex -medulla oblongata -hippocampus, and -thalmus