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MIDTERM PART 3, psychology 1000, 2013.docx

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Department
Psychology
Course
Psychology 1000
Professor
John Campbell
Semester
Fall

Description
Monday, September-23-13 Psychology Neural bases of Behaviour  Brain is grapefruit sized, 3 pound of mass of tissue made up of neurons  Neurons are the building blocks of the nervous system  At birth our brains are made up of about 100 billion neurons The brain: 1. Cerebral cortex a. Outermost layer of brain that is divided into different lobes i. Frontal- complex cognition, motor cortex ii. Temporal- auditory and language iii. Occipital-visual iv. Parietal- sensory stuff Language areas of the brain  Aphasia- partial or total loss of the ability to communicate. Depending on the location of the damage, the specific issue will differ  Broca’s area- normal speech productions  Wernicke’s area- language comprehension Hemispheric lateralization  Our brains have left and right cerebral hemispheres  Left vs. right brain Lateralization- refers to the relatively greater location of a function in one hemisphere or the other. Optic nerves criss-crosses in the brain Spinning girl experiment!  Which way is she spinning, are you left brained or right brained? Neurons The parts of a neuron: 1. Cell body or Soma  Keeps the neuron alive  The nucleus contains the genetic information which determines how the cell develops and functions 2. Dendrites  Act lie antennas that collect messages from other neurons  Can receive input from 1000 or more neurons 3. Axon  Covered by myelin sheath conducts electrical impulses away from the cell body to other neurons Monday, September-23-13 -neurons  Specialized nerve cells  Send/receive nerve impulses  Sensory, motor, interneurons -Glial cells  Hold neurons in place, manufacture nutrients, form myelin sheath, remove waste  Outnumber neurons 10:1  Also make up the blood-brain barrier (protects brain from toxins) Activity of neurons Two important actions  1. They generate electricity that creates nerve impulses  2. They release chemicals that allow them to communicate with other neurons and with muscles and with glands Neural communication  Is an electrochemical process o Electrically charged particles enter the neuron o Action potential (continues down the axon)  Action potential: a flow of ions in and out through the cell membrane reverses the electrical charge of the resting potential o Chemical molecules (neurotransmitters) Action Potential  Generation of action potential depends on the existence of a membrane potential and the presence of voltage-gated channels for Na+ and K+  A typical value for the resting membrane potential (difference in electrical charge across the plasma membrane) is -70mV  A cell that exhibits a membrane potential is polarized  Levels of K+ are higher inside and levels of Na+ are higher outside, a situation that is maintained by sodium-potassium pumps (NORMAL)  Na+ moves in (depolarizes) making the cell positive inside  K+ moves out (repolarizes) making the cell negative again inside or restored back to -70mV Action Potential Cont.  Sometimes there is a hyper-polarization when the membrane potential becomes slightly more negative than the resting level  The depolarizing and repolarizing phases take about one millisecond in neurons  Voltage gated Na+ channels open and Na+ rushes into the cell depolarizing it  Voltage gated K+ channels open more slowly so by the time Na+ channels are closing these K+ channels are opening and K+ flows out of the cell repolarizing  All or nothing principle states that if a stimulus is strong enough to generate a depolarizing threshold(-55mV) then an action potential will occur and if stimulus is not strong enough it will not occur  Refractory period few milliseconds when another action potential cannot occur Monday, September-23-13 Conduction of Nerve Impulses Unmyelinated  Action potential called continuous conduction 1. The first segment of the plasma membrane depolarizes 2. This generates an action potential that depolarizes the next patch of membrane  Short nerve cells and takes longer for action potential to depolarize entire membrane Myelinated  Action potential called salutatory conduction 1. When a nerve impulse is conducted it travels through the interstitial fluid surrounding the myelin sheath through the cytosol from one node of Ranvier to the next st 2. The nerve impulse nd the 1 node generates ionic currents that open voltage gated Na+ channels at the 2 node and trigger a nerve impulse there 3. The nerve impulse at the 2 ndnode open Na+ channels at the 3 node and triggers another nerve impulse there 4. This jumping of impulses occurs along the entire membrane from one node to the next 5. Each node depolarizes then repolarizes  Large diameters are usually myelinated therefore much faster conduction of impulses  Axons that are warm also conduct impulses at a higher speed then cold axons Synapse: -Greek for gap  The site of adjacent neurons  Do not actually touch there is a synaptic cleft between o Gap between axon terminals Otto Loewi  Demonstrated that neurons release chemicals, and it was these chemicals that carried the message from one neuron to the next Neurotransmitters -chemical substances that carry messages across the synapse to either excite other neurons or inhibit them from firing -5 main stages of chemical communication 1. Synthesis a. The chemical molecules are formed inside the neuron 2. Storage a. Chemicals then stored in chambers called synaptic vessels which are in the axon terminals 3. Release a. When an action potential comes down the axon, these vesicles move to the surface of the axon terminal b. They are released into the space between the presynaptic and postsynaptic 4. Bind a. The molecules cross the synaptic space and bind to receptor sites b. These receptor sites have specific shaped surfaces that fits a specific transmitter 5. Post-Binding a. Excitatory neurotransmitters Monday, September-23-13 o Depolarize(excite) the postsynaptic neuron membrane, bringing the membrane potential closer to threshold and increasing the chance that one or more action potentials will arise (EPSP- excitatory post-synaptic potential) b. Inhibitory neurotransmitters o hyperpolarize the membrane of the postsynaptic neuron, inhibiting action potential generation (IPSP- inhibitory post synaptic potential) c. If a negative ion goes into ion channels then it will inhibit action potential 6. Deactivation a. Some of the released neurotransmitter molecules diffuse away from synaptic cleft, once out of reach it can no longer exert an effect b. Some neurotransmitters are destroyed by enzymes c. Many neurotransmitters are actively transported back into the neuron that released them (reuptake). Others are transported into neighbouring neuroglia (uptake) Specialized Neurotransmitters  Acetylcholine – muscle contraction and ANS. Can be excitatory (NMJ) or inhibitory (Parasympathetic neurons slow heart rate) o Alzheimer’s disease o Reduction in Ach weaken or deactivate neural circuitry that stores memories  Glutamate, aspartate- excitatory o CNS, and involved in the mechanisms of learning and memory  Gamma amino butyric acid (GABA)- inhibitory (drinking alcohol inhibits inhibitor) o Effects motor control and the control of anxiety o Huntington’s disease  Norepinephrine o Dopamine- inhibitor or excitatory  ability to focus extensively, Parkinson’s disease (undersupply), Schizophrenia (oversupply) o Serotonin- inhibitor  Mood, addictive behaviours, appetite, emotional responses  Neuropeptides (endorphins) –inhibits transmission of pain impulses o Insensitivity to pain (oversupply) o Pain hypersensitivity, immune problems (undersupply) Neuromodulators: do not have a specific receptor but rather have a more widespread and generalized influence on synaptic transmission 3 major types of neurons 1. Sensory neurons a. Carry input messages from the sense organ to the spinal cord and brain 2. Motor neurons a. Transmit output impulses from the brain and spinal cord to the body’s muscles and organs 3. Interneurons a. Link the input and output functions b. Outnumber sensory and motor neurons Central nervous system Monday, September-23-13  Brain and spinal cord  Thoughts, emotions, memories, sensory information Peripheral nervous system  Includes all nervous tissue outside CNS  Connects CNS with muscles, glands and sensory receptors in skin Somatic Nervous System o Carries sensory information from the sensory organs to the CNS and relays motor (movement) commands to muscles o Controls voluntary movements o Allows you to sense and respond to your environment Autonomic Nervous System o The part of the nervous system that regulates smooth muscle, cardiac muscle and certain glands o Concerned with involuntary functions such as; breathing, circulation, digestion and aspects of motivation, emotional behaviour and stress response o 2 subdivisions 1. Sympathetic nervous system  Activation function Monday, September-23-13  Acts as a total unit  Can dilate pupils, stop digestion and speed heart rate up all at once  Can be called Fight-or-flight response 2. Parasympathetic nervous system  Acts opposing towards sympathetic functions  Acts specifically instead of a unit  Slows down body process  Counteracts what has occurred in a sympathetic response (maintains homeostasis) The Central nervous system o Contains the spinal cord which connects the PNS with the brain o The brain itself 1. The Spinal Cord  Most nerves leave the CNS by way of the spinal cord  Protected by vertebrae  Contains grey (neuron bodies) and white matter (myelinated axons)  Sensory nerves enter through the back of the spinal cord  Motor nerves exit through the front side  Spinal reflexes allow sensory neurons to flash to the spinal cord which tells motor neurons how to act without going through the brain i. This happens if say for example you touched something hot ii. Your hand will move before you register what has happened 2. The Brain  brain is 3lb of tissue  Frontal lobes are associated with higher (executive) functions such as self- control, planning, reasoning, and abstract thought.  People who have little filter have small frontal lobes Unlocking the secrets to the brain  More knowledge is known about the brain know than ever before due to technology advances 1. Neuropsychological tests  Measure verbal and non-verbal behaviours that are known to be affected by particular types of brain damage  Have provided information about brain-behaviour relations 2. Destruction and Stimulation techniques  Researchers can produce lesions in the brains of animals that can help decode what happens at different locations in the brain  This is sometimes tested on humans when accident has caused a lesion or apart of the brain to be removed  Alternatively the brain can be examined by stimulating certain parts of it and observing what happens
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