Chapter 2: Biology, Neurons, and Brain Imagery

Case Study SM: The No-Fear Woman

Why is learning to play an instrument good for the brain?

Introduction At birth have extra supply of nerve cells; stabilizes in adolescence 200,000 will die every day of your adult life you will end up with 98% of your supply by the time you’re 70

Neurons Individual cells in nervous system that receive, integrate, & transmit info

Parts of the Neuron 1. Soma: is the cell body, which contains the nucleus. 2. Dendrites: (Greek for tree) branching extensions that receive incoming messages and conduct messages toward the cell body.

Parts of A Neuron 3. Axon: extension of a neuron which takes messages from the soma to other neurons, muscles or glands Longest part of the neuron 4. Myelin Sheath: white fatty substance around axons; allows faster transmission speeds of signals Multiple sclerosis leads to deterioration Slows communication to muscles – loss of muscle control

How does a neuron communicate? Resting Potential: neuron is in its normal, resting state Ions within the cell give the axon a small negative charge, fluid outside is positive charged When the cell body becomes excited, triggers a cascade of events (like setting a little fuse on fire and keeps going until it blows up) Action potential: temporarily reverses the charge (positive) and causes an electrical signal to race along the axon. (200 mph) Happens when sense receptors feel something Chain reaction along axon to end

Your turn! Draw and label a neuron in your notes

How does a neuron communicate? Refractory Period – neuron pumps the positively charged sodium ions back outside (pausing to recharge)

How Does A Neuron Communicate? Some signals are excitatory – (pushing on accelerator); some are inhibitory (pushing on brakes) If excitatory signals exceed maximum intensity (threshold) it will trigger an action potential All or none principle: it fires or it doesn’t (doesn’t differ in intensity) Whole cycle takes less than 1/100th of a second

Neuron Communication With Other Neurons In order for one neuron to communicate with another it must pass a junction or gap called the synapse between the axon which is sending the signal and the dendrite which is receiving the signal. At the ends of the axon, the terminal buttons release neurotransmitters: which are chemical messengers that bind together neurons and influence whether another neural impulse will take place.

Neural communication Reuptake- regulates amount of NT Drugs affect neural communication at the synapse Antidepressants often act as reuptake initiators and helps regulate Insomnia is regulated by serotonin

Neuron Communication

Glial Cells Glial Cells: provide structural support, nourishment and insulation of neurons, maintains chemical environment Helps in forming new synapses New research suggests may be crucial in part of the process of learning Form a myelin sheath-fatty insulation around some axons in brain and spinal cord Helps speed up neural impulses Multiple sclerosis is a disease in which the myelin sheath degenerates-leads to loss of muscle control

Review: Can you name them all?

Schizophrenia, Parkinson’s disease Neurotransmitters Normal Function: Produces sensations of pleasure and reward; used by CNS neurons in voluntary movement Dopamine Serotonin Norepinephrine Problems with Imbalance: Schizophrenia, Parkinson’s disease Acetylcholine GABA Substances that Affect: Cocaine, amphetamines, Ritalin, alcohol Glutamine Endorphins Copyright © Allyn & Bacon 2007

Depression, certain anxiety disorders, obsessive- compulsive disorder Neurotransmitters Normal Function: Regulates sleep and dreaming, mood, pain, aggression, appetite and sexual behavior Dopamine Serotonin Norepinephrine Problems with Imbalance: Depression, certain anxiety disorders, obsessive- compulsive disorder Acetylcholine GABA Glutamine Substances that Affect: Prozac, hallucinogenics (e.g. LSD) Endorphins Copyright © Allyn & Bacon 2007

High blood pressure, depression Neurotransmitters Normal Function: Controls heart rate, sleep, sexual responsiveness, stress, vigilance and appetite Dopamine Serotonin Norepinephrine Problems with Imbalance: High blood pressure, depression Acetylcholine GABA Substances that Affect: Tricyclic antidepressants, beta blockers Glutamine Endorphins Copyright © Allyn & Bacon 2007

Certain muscular disorders, Alzheimer’s disease Neurotransmitters Normal Function: Primary transmitter used by neurons carrying messages from CNS; involved in some kinds of learning and memory Dopamine Serotonin Norepinephrine Problems with Imbalance: Certain muscular disorders, Alzheimer’s disease Acetylcholine GABA Substances that Affect: Nicotine, botulism toxin, curare, atropine Glutamine Endorphins Copyright © Allyn & Bacon 2007

Most prevalent inhibitory neurotransmitter in neurons of CNS Neurotransmitters Normal Function: Most prevalent inhibitory neurotransmitter in neurons of CNS Dopamine Serotonin Norepinephrine Problems with Imbalance: Anxiety, epilepsy Acetylcholine GABA Substances that Affect: Barbiturates, tranquilizers (e.g. Valium, Librium), alcohol Glutamine Endorphins Copyright © Allyn & Bacon 2007

Brain damage after stroke Neurotransmitters Dopamine Normal Function: Primary excitatory neurotransmitter in CNS; involved in learning and memory Serotonin Norepinephrine Acetylcholine Problems with Imbalance: Brain damage after stroke GABA Substances that Affect: PCP (“angel dust”) Glutamine Endorphins Copyright © Allyn & Bacon 2007

Pleasurable sensations and control of pain Neurotransmitters Dopamine Normal Function: Pleasurable sensations and control of pain Serotonin Norepinephrine Problems with Imbalance: Lowered levels resulting from opiate addiction Acetylcholine GABA Substances that Affect: Opiates: opium, heroin, morphine, methadone Glutamine Endorphins Copyright © Allyn & Bacon 2007

Neural communication Agonists excite neurons by mimicking natural neurotransmitters or blocking their reuptake to keep more of them in your system Antagonists inhibit neural impulses by blocking receptor sites or diminishing their release One reason it is difficult to design pharmaceutical drugs is that we have a blood brain barrier: which is a membrane that only lets certain chemicals pass through Parkinson’s suffer from a lack of dopamine, but dopamine can’t cross the barrier, therefore we can’t give them dopamine L-Dopa must be used (kind of like synthetic dopamine) because it can cross the barrier

Nervous system Reflexes: (automatic responses) are a good example of how the spinal cord works; brain not involved in simple reflexes Simple spinal pathways only involve 2 neurons sensory neuron motor neuron communication through an interneuron ex. knee-jerk ex. hand on a hot stove

Figure 2.9 A simple reflex Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

Nervous system if you become paralyzed from a spinal cord injury these reflexes still work; depending on type of damage Brain involved in voluntary movements; how paralysis occurs with spinal injury, the higher the greater extent of damage.

Nervous system Peripheral Nervous System: the sensory and motor neurons that connect the CNS to the rest of the body nerve- bundled axons of motor and sensory neurons We have 3 types of neurons 1) sensory neurons- afferent -carry info. from sense receptors toward the Brain 2) motor neurons-efferent- carry information away from the Brain to the muscles, organs, and glands 3) interneurons- the go-between-most of the neurons in the brain and spinal cord. Relay messages from sensory neurons to other interneurons or to motor neurons, sometimes in complex pathways.

Nervous system Peripheral Nervous System – has many branches 1) Somatic nervous system controls voluntary movements of skeletal muscles communications link with the outside world sensory and motor components 2) Autonomic nervous system controls the glands and muscles of our internal organs operates without us thinking about it heartbeat, breathing, digestion, etc. broken down into 2 divisions; even while sleeping and unconscious

Autonomic Nervous system 3) Sympathetic nervous system arouses the body to deal with stressful situations slows digestion, raises heartbeat and blood sugar, dilates your arteries, etc. prepares for “fight or flight” 4) Parasympathetic nervous system calms the body to bring it back into homeostasis decreases heartbeat, lowers blood sugar, etc.