Chapter 2 The Brain or Bio Psychology 1 2 3 1
Glial Cells Surround neurons and hold them in place Make Myelin (covering for neurons) Manufacture nutrient chemicals neurons need Absorb toxins and waste materials 4 Fig. 2-1, p. 28 When you pull your finger away from a hot candle flame, it is NEURONS sending signals from the finger to the brain and back to the muscles that are responsible. NEURONS sending information from your eye to your brain, and within your brain are responsible for you being able to see and read this. When a neuron sends this information, what is really happening? 6 2
Information flows WITHIN and BETWEEN neurons. Let s first focus on what happens within a neuron. 8 Neuron at Rest Resting Potential negative 70 mvolts: a state of polarization Inside of cell is more negatively charged compared to outside 9 3
Neurons are surrounded by salty liquid with Na+, K+, Cl, and some other ions. Cell membrane is selectively permeable with gates. These gates are voltage dependent. 10 Fig. 2-3, p. 30 How does a neuron maintain this state of polarization? I.E. how does it keep the inside more negative than the outside? Sodium Potassium Pump 3 NA + pumped out for every 2 K + pumped in. Net effect: Positives are pumped out. 4
Facts Na+/K+ pump maintains 70 mvolt charge Pumps Na+ out and K+ in. Pumps 3 sodiums out for every 2 potassiums in Effect: Na+ wants in (concentration & electrical gradient) K+ wants out (concentration gradient) a little more than it wants in (electrical gradient) Net effect is more + ions are pumped out which leads to the outside being more positive (and inside more negative). 13 The Action Potential Time 1: Hyperpolarization (inside more negative) Time 3: Depolarization (inside less negative) Time 6: Action Potential 14 The Action Potential: How do we get to a positive charge inside? When the voltage level crosses a threshold, Na+ gates open and Na+ rushes in Changes voltage inside to +30 mvolts. Follows the all or nothing law All action potential amplitudes are the same Information is carried by frequency of firing 15 5
How to return to resting potential? K+ gates open and K+ moves out. Propagation of the action potential Occurs when the rush of Na+ inside the cell pushes the + ions down the cell creating (propagating) a new action potential 6
Nerve Conduction: The Action Potential What starts the action potential? Dendrites are stimulated by other neurons causing the voltage level to change and either Depolarize or create action potentials (or increase the likelihood of them) or Hyperpolarize and make action potentials LESS likely. 19 Nerve Conduction: The Myelin Sheath & Nodes of Ranvier (Rahn-vee-ay) Insulation layer covers axons in the brain and spinal cord. Allows for high-speed conduction 10 times faster than if not insulated, up to 200 mph. Multiple sclerosis occurs when immune system attacks the sheath 20 The Synapse Synapse = the gap between neurons Sherrington (1906) & Loewi (1920) credited with discovery that the synapse was a chemical thing. When an action potential reaches the end of the neuron, causes chemicals (neurotransmitters) to be released into the gap between neurons. Over 100 neurotransmitters (NTs) are known. 21 7
Diffusion to postsynaptic is quick (milliseconds?). NTs fit into receptors on the postsynaptic cell like a lock/key. NTs can excite or inhibit postsynaptic cell. After NTs do their thing they back out and are either Recycled Degraded Diffuse away 23 Excitatory and Inhibitory signals. Temporal vs. spatial summation 8
Drugs and the Synapse Drugs work by doing one or more of the following to neurotransmitters: 1. Increasing the synthesis. 2. Causing vesicles to leak. 3. Increasing release. 4. Decreasing reuptake. 5. Blocking the breakdown into inactive chemical. 6. Directly stimulating or blocking postsynaptic receptors. Major Neurotransmitters Acetylcholine (ACh) Involved in memory and muscle activity Dopamine An excitatory transmitter Too much = psychotic symptoms Too little = Parkinson s Disease Serotonin Enhances mood, eating, sleep, and sexual behavior Endorphins Reduce pain and increase feeling of well-being Norephephrine GABA 26 The Nervous System Three types of neurons: Sensory: Carry input messages from the sense organs to the spinal cord and brain Motor: Transmit impulses from the brain and spinal cord to the muscles and organs Interneurons: Perform connective or associative functions in the nervous system See also temporal or spatial summation 27 9
Sensory Neuron Fig. 2-6, p. 31 Motor Neuron Fig. 2-5, p. 30 What do we call it when the signal doesn t have to go to the brain in order for you to react to the heat? R _ A 30 10
Organization of The Nervous System Central Nervous System Brain and Spinal Cord Peripheral Nervous System Everything that isn t in the CNS Connects the CNS with the muscles, glands, and sensory receptors 31 The Peripheral Nervous System Subdivided into: Somatic nervous system: Consists of sensory neurons and neurons that control voluntary or skeletal muscles. Autonomic nervous system: Controls glands and smooth muscles in bodily organs Sympathetic nervous system: arouses the body Parasympathetic nervous system: slows down body processes 32 11
34 35 Glands make up the Endocrine System These glands secrete Hormones that travel through the blood stream Testicles secret testosterone Ovaries secret estrogen Adrenal glands secrete cortisol 12
Studying the Brain Destruction or surgical removal of neurons Stimulation of neurons By electrical current or chemicals Neuropsychological tests Electrical (EEG) recording CT Scan PET Scans and fmri. 37 38 Studying the Brain: Brain Imaging Measure Structure: CT Scans & MRI: Measure Process: Fmri and PET and EEG. 39 13
Brain Structures: The Lobes 40 Cortex 42 14
Brain Structures: Hemispheres Cerebral 43 Left hemisphere: Language and Verbal Processing, analytical thinking Right hemisphere: Non verbal Processing: (spatial skills, visual recognition, music etc) Split Brain Studies 44 He knows but doesn t know he knows 45 15