Chapter 3: The Biological Bases of Behaviour (map 1 of 2)

1. Neurons

   Nota:

   • -Neurons are individual cells in the nervous system that receive, integrate, and transmit information. -Vast majority of them communicate only with other neurons. -A small minority receive signals from outside the nervous system(from sensory organs) or carry messages from the nervous system to muscles  that move the body.
   1. Come in tremendous variety of types and shapes
      1. Parts of a Neuron
         1. Dendritic Tree(Dendrites)

            Nota:

            • -Dendrite is a Greek word for tree. -Each individual branch is a dendrite -dendrites are the parts of a neuron that are specialized to receive information. -most neurons receive information from many (thousands)of others.
            1. Soma (cell body)

               Nota:

               • Contains the cell nucleus and much of the chemical machinery common to most cells.
               1. Axon

                  Nota:

                  • - From Greek for axle. -The axon is a long, thin fibre that transmits signals away from the soma to other neurons or muscles or glands. -Axons can be over a meter long.
                  1. Myelin Sheath

                     Nota:

                     • -The myelin sheath is insulating material, derived from glial cells, that encases some axons. - myelin is a high concentration of a white fatty substance -Myelin sheath speeds up the transmission of signals that move along the axon. if an axon's myelin sheath deteriorates, its signal may not be transmitted effectively, ie Multiple Sclerosis.
                     1. Terminal Buttons

                        Nota:

                        • -The axon ends in a cluster of terminal buttons, which are small knobs that secrete chemicals called neurotransmitters. these chemicals serve as messengers that may activate neighbouring neurons.
                        1. Synapse

                           Nota:

                           • - A synapse is a junction where information is transmitted from one neuron to another. -synapse is Greek for junction.
                           1. Picture below is from pg 81 of psychology themes and variations(4th edition) showing the structure of a neuron
2. Glia
   1. Found throughout the nervous system
      1. Provide support for neurons
         1. Glia literally means glue
            1. glia cells supply nourishment to, remove waste products from neurons
               1. Glia cells play a role inthe development of the nervous system in the human embryo
                  1. New research suggests that glia may also send & receive chemical signals
3. The Neural Impulse
   1. Neuron at rest
      1. The cell membrane is semipermeable, permitting movement of some ions.
         1. The resting potential of a neuron is its stable, negative charge when the cell is inactive. About 270 millivolts.
   2. Action Potential

      Nota:

      • -Action Potential is a very brief shift in a neuron's electrical charge that travels along an axon.
      1. When the neuron is stimulated, channels in its cell membrane open, briefly allowing postively charged sodium ions to rush in, creating an action potential.
         1. Voltage change races down the axon
            1. After firing the channels in the membrane close up.Some time is needed before they are ready to open again, until that time the neuron cannot fire again. (absolute refractory period)

               Nota:

               • -Absolute refractory period is the minimum length of time after an action potential during which another action potential cannot begin. -Only 1 or 2 milliseconds.
               1. During the Relative Refractory Period. the neuron can fire, but its threshold for firing is elevated, so more intense stimulation is required to initiate an action potential.
                  1. All or None Law

                     Nota:

                     • -Neurons fire or they don't, all action potentials are all the same size, that is weaker stimuli do not produce smaller action potentials -neurons can convey information about the strength of a stimulus. -In general stronger stimulus will cause a cell to fire a more rapid volley of neural impulses than a weaker stimulus will.
4. The Synapse
   1. Depends on chemical messengers
      1. Sending Signals
         1. Neurons don't actually touch. They are seperated by the Synaptic Cleft.

            Nota:

            • -The synaptic Cleft is, a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron. -signals have to cross this gap to permit neurons to communicate.
            1. Presynaptic neuron sends the signal across the gap
            2. Postsynaptic neuron receives the signal
            3. Arrival of the action potential at the terminal buttons triggers the release of Neurotransmitters.

               Nota:

               • -Neurotransmitters are chemicals that transmit information from one neuron to another. -With in the buttons most of these chemicals are stored in small sacs called the Synaptic vesicles. -Neurotransmitters are released when a vesicle fuses with the membrane of the presynaptic cell and the contents spill into the synaptic cleft.
               1. Neurotransmitters may bind with special molecules in the postsynaptic cell membrane at various receptor sites.These sites are specifically tuned to respond to some , but not other neurotransmitters.
                  1. Picture below is from pg 83 of psychology themes and variations(4th edition) showing the synapse
      2. Receiving Signals
         1. When a neurotransmitter and a receptor molecule combine,reactions in the cell membrane cause a postsynaptic potential (PSP)

            Nota:

            • -Postsynaptic potential (PSP), a voltage change at a receptor site on a postsynaptic cell membrane. -PSP do NOT follow the all or none law.
            1. PSP are graded

               Nota:

               • -They vary in size and they increase or decrease the probability of a neural impluse in the receiving cell in proportion to the amount of voltage change.
               1. 2 types of messages can be sent from cell to cell
                  1. Excitatory PSP
                     1. increases the likelihood that the postsynaptic neuron will fire action potentials
                        1. Reuptake

                           Nota:

                           • - Reuptake is a process in which neurotransmitters are sponged up from the synaptic clef by the presynaptic membrane. - this allows for synapses to recycle their materials.
                           1. picture below is taken from pg84 od psychology themes and variations (4th edition) showingsynaptic transmission
                  2. Inhibitory PSP
                     1. decreases the likelihood that the postsynaptic neuron will fire action potentials
                        1. Reuptake
      3. Integrating Signals
         1. Neurons must integrate signals arriving at many synapses before it "decides" to fire a neural impulse.
            1. Elimination of old synapses appears to play a larger role in the sculpting of neural networks than the creation of new synapses.
               1. Synaptic pruning is a key process in the formation of the neural networks that are crucial to communication in the nervous system.
                  1. Repeated synaptic activity leads to a stregthening of the synapse
   2. Neurotransmitters & Behaviour
      1. Neurotransmitters are fundamental to behaviour, playing a key role in everything from muscle movements to moods and mental health.
         1. Agonist is a chemical that MIMICS the action of a neurotransmitter
         2. Antagonist is a chemical that OPPOSES the action of a neurotransmitter

            Nota:

            • -Key slides in the lock, but it doesn't work -temporarily block the action of the natural transmitter ny occupying its receptor sites rendering them unusable
      2. Monoamines
         1. Dopamine (DA)
            1. used by neurons that control voluntary movements

               Nota:

               • -degeneration  of such neurons in a specific area of the brain causes PARKINSON's
               1. over activity at DA synapses associated with schizophrenia
                  1. Cocaine and amphetamines elevate activity at DA synapses
         2. Norepinephrine (NE)
            1. Contributes to modulation of mood and arousal
               1. Cocaine and amphetamines elevate activity at NE synapses
         3. Serotonin
            1. Play a prominent role in the regulation of sleep & wakefulness, eating, and aggression
               1. Abnormal levels may contribute to depression and OCD
                  1. Antidepressant drugs affect serotonin circuits
      3. Acetylcholine (ACh)
         1. Only transmitter between motor neurons and voluntary muscles
            1. Appears to contribute to attention,arousal and memory
               1. Some ACh receptors stimulated by nicotine
      4. Amino Acids
         1. Glutamate
            1. Has both excitatory and inhibitory effects
               1. Implicated in learning and memory
         2. Gamma-aminobutyric Acid (GABA)
            1. Serves as widely distributed inhibitory transmitter
               1. Antianxiety drugs work at GABA synapses
      5. Endorphins
         1. Contribute to pain relief & perhaps to some pleasurable emotions
            1. Resemble opiate drugs in structure and effects

1. Consists of the brain and the spinal cord
   1. Brain
      1. Protected by enclosing sheaths called meninges. Also bathed in cerebrospinal fluid (CSF)
   2. Spinal Cord
      1. Connects the brain to the rest of the body through the peripheral nervous system

Nota:

• The peripheral nervous system ia made up of all those nerves that lie outside the the brain and spinal cord. Nerves are bundles of neuron fibres (axons) that are routed together in the peripheral nervous system.

1. Somatic Nervous System
   1. made up of nerves that connect to voluntary skeletal muscles and to sensory receptors
      1. Has afferent nerve fibres that carry information inward to the CNS.Efferent nerve fibres carry information outward from the CNS
2. Autonomic Nervous System (ANS)
   1. made up of nerves that connect to the heart, blood vessels, smooth muscles and glands.
      1. is a separate autonomous system that controls things like heart rate, digestion etc.
         1. Fight or Flight response
            1. ANS has two branches
               1. Sympathetic division mobilizes the body's resources for emergencies (go!!!)
               2. Parasympathetic division generally conserves bodily resources (stop)

1. mapping brain function requires a working brain
   1. Neuroscientists conduct research on the brain and other parts of the nervous system.

1. Electroncephalograph (EEG)
   1. Is a device that monitors the electrical activity of the brain over time by means of recording electrodes attached to the surface of the scalp.
      1. EEG recordings are translated into line tracings commonly called brain waves.
         1. EEG is often used in the clinical diagnosis of brain damage and neurological disorders.

1. Used to study the relationship between brain and behaviour more precisely, scientists sometimes observe what happens when specific brain structures in animals are purposely disabled.
   1. Lesioning involves destroying a piece of the brain.
      1. Typically done by inserting an electrode into a brain structure and passing a high frequency electric current through it to burn the tissue and disable the structure.

1. Involves sending a weak electric current into a brain structure to stimulate (activate) it.
   1. Has lead to advances in the understanding of many aspects of brain-behaviour relationships.

1. Noninvasive and permits scientists to temporarily enhance or depress activity in a specific area of the brain.
   1. Chief limitation is that it cannot be used to study areas deep within the brain.
      1. By varying the timing and duration of the magnetic pulses, a researcher can either increase or decrease the excitability of neurons in the local tissue

1. Computerized tomography (CT) scan
   1. Is a computer enhanced X-ray of brain structure
      1. Is a vivid image of a horizontal slice of the brain.
2. Positron Emission Tomography (PET)
   1. Can examine brain function, mapping actual activity in the brain over time.
      1. Uses radioactively tagged chemicals introduced into the brain. which can be monitored with X-rays.
3. Magnetic Resonance Imaging (MRI) Scan
   1. uses magnetic fields, radio waves and computerized enhancement to map brain structure
      1. Provides better images of brain structure than CT scan
         1. insightful about depressive disorders
            1. Functional Magnetic Resonance Imaging (fMRI)
               1. New variation on the MRI that monitors blood flow and oxygen in the brain to identify areas of high activity. It can map actual activity in the brain over time with greater precision