The World of Psychology Wood and Wood Physiological

The World of Psychology Wood and Wood Physiological Psychology Chapter 2

Some Definitions

The Neurons and the Neurotransmitters Neurons appear in many forms, but all possess the three basic structures: • a cell body • an axon (with axon terminals) • one or more dendrites.

There are Three Types of Neurons n n n Afferent (Sensory) Efferent (Motor) Interneurons

The Neuron n Dendrite Cell body Axon The Life and Death of a Neuron

The Neuron n Dendrite n Cell body n Axon

The Neural Impulse n n n Resting Potential Action Potential All or None law

Resting Potential z. The definitive reference guide to neuron potential: http: //www. biol. sc. edu/~vogt/courses/neuro. AP. html z All about the electrical properties of a cell: http: //artsandscience. concordia. ca/psychology/psyc 358/Lectures/restp otent 1. htm

Resting Potential –The whole story The potential difference that exists across the membrane of all cells is usually negative inside the cell with respect to the outside. The membrane is said to be polarized. The potential difference across the membrane at rest is called the resting potential and is approximately -70 m. V in neurons. (The negative sign indicates that the inside of the cell is negative with respect to the outside. ) The establishment of this potential difference involves several factors, most importantly the transport of ions across the cell membrane and the selective permeability of the membrane to these ions. The active transport of potassium and sodium ions into and out of the cell, respectively, is accomplished by a number of sodium-potassium pumps scattered across the cell membrane. Each pump transports two ions of potassium into the cell for every three ions of sodium pumped out. This establishes a particular distribution of positively charged ions across the cell membrane, with more sodium present outside the cell than inside, and more potassium inside the cell than outside. In some situations, the electrogenic sodium-potassium pumps make a significant contribution to the resting membrane potential, but in most cells there are special potassium channels ("leak channels") that dominate the value of the resting potential. The natural tendency of sodium and potassium ions is to diffuse across their electrochemical gradients to attempt to reach their respective equilibrium potentials, with sodium diffusing into the cell and potassium diffusing out. However, the resting cell membrane is approximately 100 times more permeable to potassium than to sodium, so that more potassium diffuses out of the cell than sodium diffuses in. This permeability to potassium is due to potassium leak channels that are always open. As a result, the dominant outward leak of potassium ions produces a hyperpolarizing current that establishes the cell's resting potential of roughly -70 m. V. From: http: //en. wikipedia. org/wiki/Action_potential#Resting_potential

Axons are like wastebaskets – well, sorta…

Action Potential The Action Potential (Top)During an action potential, positively charged particles enter the membrane through specialized ion channels, thereby momentarily eliminating the negative charge just inside the neuron’s membrane. Movement of this disturbance along the membrane constitutes the action potential. (Bottom) After a brief period, however, positively charged particles are forced outside of the neuron’s membrane via the ion channels.

Action potential in Action The impulse (red) moves along the axon.

Action Potential Details http: //people. eku. edu/ritchisong/301 notes 2. htm Source: http: //faculty. washington. edu/chudler/ap. html

All or None law • Law refers to the activity of a single neuron. • A neuron will either fire or it will not. • When it fires, it fires with the same intensity every time. • Implications for nervous system communication • Because the intensity is always the same, variability come from somewhere else. • That variability is the rate of nerve impulses.

All or None law • Law implies the central nervous system is binary. • What is binary? • Information is encoded as frequency coding. • What is Frequency Coding Additional info: http: //zadorlab. cshl. edu/PDF/deweese-zador 2002. pdf

The Synapse n Axon Terminal n Synaptic Vesicles n Synaptic Cleft http: //people. eku. edu/ritchisong/301 notes 2. htm

Neurotransmitters Acetycholine n Monoamines (Serotonin, Dopamine, epinephrine, norepinephrine) n Amino Acids n Endorphins n

Neurotransmitters: Their Basic Effects Neurotransmitters exert one of two basic effects on neurons. If the neurotransmitter is excitatory the neuron’s cell membrane becomes depolarized (the charge becomes more positive); it increases the likelihood that an action potential will occur. In contrast, if the neurotransmitter is inhibitory the cell membrane of a neuron becomes hyperpolarized (the charge becomes more negative); its effects decrease the likelihood that an action potential will occur.

Neurotransmitters: Their Specific Effects Acetycholine Found throughout the central nervous system, in the autonomic nervous system, and at all neuromuscular junctions. Involved in muscle action, learning, and memory. Norepinephrine Found in neurons in the autonomic nervous system. Primarily involved in control of alertness and wakefulness. Dopamine Produced by neurons located in a region of the brain called the substantia nigra. Involved in movement, attention, and learning. Degeneration of dopamine-producing neurons has been linked to Parkinson’s disease. Too much dopamine has been linked to schizophrenia.

Neurotransmitters: Their Specific Effects Serotonin Found in neurons in the brain and spinal cord. Plays a role in the regulation of mood and in the control of eating, sleep, and arousal. Has also been implicated in the regulation of pain and in dreaming. GABA (gamma-amino-butyric acid) Found throughout the brain and spinal cord. GABA is the major inhibitory neurotransmitter in the brain. Abnormal levels of GABA have been implicated in sleep and eating disorders.

Neurotransmitters: Endorphins were first discovered during the 1970 s by researchers studying the effects of morphine and other opiates. To their surprise, the researchers learned there were special receptor sites for such drugs within the brain (Hughes et al. , 1975). Why should such receptors exist? • Naturally occurring substances that closely resemble morphine in physical structure are produced by the brain. • These substances, known as endorphins, act as neurotransmitters, stimulating specialized receptor sites.

Neurotransmitters: More Endorphins Why should the brain produce such substances? • Endorphins are released by the body in response to • pain or • vigorous exercise • Help reduce sensations of pain • that might otherwise interfere with ongoing activity (Fields & Basbaum, 1984). • Endorphins also serve to intensify positive sensations For example, the “runner’s high” Pain Management – Value & Effects

Psychoactive Drugs How they work

They CAN effect the neurotransmitters. Psychoactive Drugs How they work 2 Psychoactive drugs exist because: • They are produced in nature OR • They are produced artificially by man • They mimic the brain’s own neurotransmitters OR • They affect the brain’s own neurotransmitters actions AND • They cross the blood brain barrier!

The Nervous System Copyright © Allyn & Bacon 2002

The Central Nervous System n Brain Cerebellum n Thalamus n Hypothalamus n Limbic System n n Neurons Cortex Spinal Cord n n links the body with the brain Brainstem Medulla n Reticular Formation n Pons n

Cerebral Hemispheres n Lobes of the Brain Frontal lobes n Parietal lobes n Occipital lobes n Temporal lobes n n Other Structures Cerebellum n Motor cortex n Frontal Lobe- reasoning, planning, parts of speech, movement, emotions, and problem solving Parietal Lobe- movement, orientation, recognition, perception of stimuli Occipital Lobe- visual processing Temporal Lobe- perception and recognition of auditory stimuli, memory, and speech

Major Structures of the Human Brain n n n n Cerebral Cortex Corpus Callosum Thalamus Cerebellum Reticular Formation Medulla Pons Pituitary Gland Hypothalamus

The Limbic System n n n Hypothalamus Amygdala Corpus Callosum Pituitary Gland Hippocampus Another View

Brain Hemispheres n Left n n Brain Language mathematics Logic Right Side Movement n Right n n n Brain Music Art Spatial Skills Creativity Intuition Emotion

Brain Waves Beta (Mental or Physical Activity) Relatively low amplitude, and are the fastest of the four different brainwaves. The frequency of beta waves ranges from 15 to 40 cycles a second. Beta waves are characteristics of a strongly engaged mind. Alpha (Deep Relaxation) Alpha represents non-arousal. Alpha brainwaves are slower, and higher in amplitude. Their frequency ranges from 9 to 14 cycles per second. A person who has completed a task and sits down to rest is often in an alpha state. Theta (Light Sleep) Even greater amplitude and slower frequency. This frequency range is normally between 5 and 8 cycles a second. A person who has taken time off from a task and begins to daydream is often in a theta brainwave state. Delta (Slow Wave Sleep) Greatest amplitude and slowest frequency, centered around a range of 1. 5 to 4 cycles per second. Deep dreamless sleep goes down to the lowest frequency - typically, 2 to 3 cycles a second.

Discovering the Brain’s Mysteries EEG n CT Scan n MRI n PET Scan n f. MRI n More on EEGs More on CT Scan More on PET Scan

Gender Differences z. MEN AND WOMEN DIFFER IN BRAIN USE DURING SAME TASKS y. A man's brain and a woman's brain really do work differently. y. New research from the University of Alberta shows that men and women utilize different parts of their brains while they perform the same tasks. http: //www. physorg. com/news 8634. html

More Gender Differences BRAIN DIFFERENCES COULD EXPLAIN WHY MALES AND FEMALES EXPERIENCE PAIN RELIEF DIFFERENTLY • Study conducted by investigators at Georgia State University and the Atlanta-based Center for Behavioral Neuroscience (CBN) • Anatomical and functional differences in the brain may explain sex differences in the experience of pain and in the effects of certain drugs on pain. Full story at http: //www. physorg. com/news 64588700. html

Age - Youth z TEENS UNDERGO FAST BRAIN MAKEOVER ya teen's brain undergoes a previously unsuspected biological makeover not complete until they're 25, and that could explain a few things. Full story at http: //www. physorg. com/news 12113. html z BRAIN CHANGES SIGNIFICANTLY AFTER 18 ystudy aimed at identifying how and when a person's brain reaches adulthood, y anatomically, significant changes in brain structure continue after age 18. Full story at http: //www. physorg. com/news 10581. html

Age - Elderly z. Exercise – body and brain y aerobics fights brain shrinkage http: //www. physorg. com/news 82922696. html y. Walking decreases apparent age in nursing home patients. y. Video Games? http: //www. boston. com/news/science/articles/2007/01/08/little_proof_tha t_brain_exercises_can_prevent_mental_decline/

Food and Training z Brain Training Can Have Lasting Benefits URL: http: //www. physorg. com/news 85769096. html z Reading Shakespeare has dramatic effect on human brain URL: http: //www. physorg. com/news 85664210. html z Eating Berries Neurobiology of Aging, Tufts psychologist Barbara Shukitt. Hale and her colleagues say a diet rich in berries improved the brain function of aging rats z DIET SEEN TO CUT ALZHEIMER'S RISK SHARPLY A Columbia University study has found that the Mediterranean diet rich in olive oil can reduce the risk of Alzheimer's disease by up to 40 percent. http: //www. physorg. com/news 64580999. html z Fish Oil[Omega 3 fatty acids] The evidence is overwhelming and may even be the cause of humans winning the “hominid wars. ”

The Peripheral Nervous System n Somatic Nervous System n n Controls skeletal muscles interacts with external environment n Autonomic Nervous System n n Sympathetic Nervous System Mobilizes Parasympathetic Nervous System Rescues

The Endocrine System n n n Pituitary Gland (Master Gland) Thyroid Glands Pancreas Adrenal Glands Ovaries and Testes

End z. That’s as far as we get.