BIOLOGICAL PROCESSES

Transcription

1 BIOLOGICAL PROCESSES CHAPTER 3 1 LEARNING GOALS Discuss how the nervous system communicates internally. Describe the structure and function of neurons Describe how the neuron transmits information Describe the action potential, the neurotransmitters, and the synapse Describe how drugs and other substances affect transmission and alter behavior Discuss how the nervous system initiates and coordinates behavior efficiently Describe the basic organization of the nervous system Describe the major structures of the brain and their related functions Discuss how growth and internal functions are regulated in the body through the endocrine system (book) 2 1

2 BIOPSYCHOLOGY/ NEUROSCIENCE Biopsychology interaction between behavior, brain, and environment Neuroscience several sciences interested in brain function 3 OUTLINE Genetics Communication in the nervous system Resting Potential Action Potential The Synapse Neuroanatomy Studying the Brain 4 2

3 GENETICS AND THE BRAIN How did we get these brains? Brain is the product of a biological heritage Evolution Environmental pressure (changes in the environment) Competition (for resources) Selection of fittest phenotype (from among a variety of phenotypes) Reproductive success (genotype corresponding to fittest Phenotypes passed to next generation) Frequency of that genotype increases (in next generation) 5 GENETICS IN PSYCHOLOGY Behavioral genetics Intelligence, personality, abnormal behavior schizophrenia Very complex, with multiple factors that interact 6 3

4 OUTLINE Genetics Communication in the nervous system Resting Potential Action Potential The Synapse Neuroanatomy Studying the Brain 7 FUNCTION OF A NEURON Reception - take info from neighboring neurons Conduction (integrate signals) Transmission (pass on to other neurons) 8 4

5 ANATOMY OF A NEURON Cell body: (Gray) 9 ANATOMY OF A NEURON Dendrites 10 5

6 ANATOMY OF A NEURON Axon (White) 11 ANATOMY OF A NEURON Myelin 12 6

7 ANATOMY OF A NEURON Synapse 13 4 COMMON COMPONENTS OF A NEURON Dendrites input, receives neurotransmitters Soma processing Axon transmits signal Terminal Buttons output, release neurotransmitters to target Myelin Sheath insulates axon Synapse - junction between neuron and target 7

8 INPUT and OVERVIEW OF NEURON PROCESSING COMMUNICATON Transmitter-gated receptor channels EPSP / IPSP produced by ion entry & exit Temporal & Spatial summation occurs in the soma TRANSMISSION and Neurotransmitter RELEASE COMMUNICATION IN THE NERVOUS SYSTEM Electrical Signals Discrete on/off signal Fast over long distances Caused by movement of positive (Na +, K + ) or negative (Cl - ) salt ions in or out of the neuron 2 types: synaptic potentials action potentials Chemical Signals between neurons: Neurotransmitters Slower but only used for short distance (synapse) Chemicals provide selectivity that electricity does not have due to lock and key binding as hormones: Sustained effects throughout body 8

9 ANATOMY OF A NEURON Nodes of Ranvier Salutatory Action video

10 STRUCTURE OF THE AXON Semi-permeable cell membrane: 10nm thick Ion channels are selectively permeable Ions inside and outside membrane OUTLINE Genetics Communication in the nervous system Resting Potential Action Potential The Synapse Neuroanatomy Studying the Brain 20 10

11 RESTING POTENTIAL -70mV Outside positive (+) relative to inside Primary ions involved Na + K + Cl - Ca ++ (axon terminals) RESTING POTENTIAL Resting potential (charge inside the cell) is maintained at -70mV (this makes for an easy and quick response) This in an active process with Na+ and K+ pumps in the cell wall constantly moving ions to maintain the concentration imbalance 22 11

12 RESTING POTENTIAL OUTLINE Genetics Communication in the nervous system Resting Potential Action Potential The Synapse Neuroanatomy Studying the Brain 24 12

13 ACTION POTENTIAL: ALL OR NONE SELF-PROPAGATING Nodes of Ranvier /Hyperpolarization 13

14 FACTORS THAT PRODUCE THE RESTING POTENTIAL Ion channels with voltage-sensitive gates ION FLOW DURING THE ACTION POTENTIAL -55 mv Threshold Sodium channels open Threshold passed? Depolarization: Moves from 70mV to +50 mv Potassium channels open Sodium channels close Potassium channels close 14

15 ACTION POTENTIAL OUTLINE Genetics Communication in the nervous system Resting Potential Action Potential The Synapse Neuroanatomy Studying the Brain 30 15

16 SYNAPSE NEUROTRANSMITTER RELEASE 32 16

17 SYNAPTIC EVENTS CHEMICAL SIGNALING Chemical messengers lock and key Action depends on the lock Allows: Two neurons to send different signals to the same target (heart muscle under NE and ACh). Two synapses can be very close and not interfere with each other (no cross-talk) Different neurotransmitters are used in different locations for different purposes 34 17

18 COMMUNICATION AT THE SYNAPSE NEUROTRANSMITTER Acetylcholine (ACh): Parasympathetic nervous system. Induces calm, stimulates muscles, involved in Alzheimer s dementia GABA: main brakes in the brain. Involved in anxiety (low levels associated with panic-like feelings, higher levels involved in relaxation). Dopamine (DA): Involved in movement and attention. Low levels in Parkinson s disease, higher levels associated with schizophrenic like behaviors. Serotonin (5-HT): Mood and arousal. High levels with sedation, low levels with depression Glutamate (GLU): Memory Endorphins: Pain and pleasure 36 18

19 COMMON DRUG ACTIONS Agonist increases the effect of a neurotransmitter Antagonist decreases the effect of a neurotransmitter Ways drugs can be Agonists: Mimic the neurotransmitter and artificially activate the receptors Increase the production of neurotransmitter Inhibit metabolism or enzymatic breakdown of neurotransmitter Inhibit or block neurotransmitter reuptake from synapse Increase the release or amount of neurotransmitter in vesicles Ways drugs can be Antagonists Block access to the receptor Inhibit production of the neurotransmitter Breakdown or inactive neurotransmitter (speed metabolism) Cause neurotransmitter leakage from vesicles DRUGS WORKING AT DOPAMINE SYNAPSE 19

20 POST-SYNAPTIC MEMBRANE EFFECTS Presynaptic Neuron Postsynaptic Neuron 39 EPSP VS IPSP

21 OUTLINE Genetics Communication in the nervous system Resting Potential Action Potential The Synapse Overview Neuroanatomy Studying the Brain 41 INPUT and OVERVIEW OF NEURON PROCESSING COMMUNICATION Transmitter-gated receptor channels EPSP / IPSP produced by ion entry & exit Temporal & Spatial summation occurs in the soma TRANSMISSION and NT RELEASE 21

22 SYNAPTIC POTENTIAL (INPUT) Function: Turns a chemical signal (neurotransmitter) into an electrical signal Location: Primarily in the dendrites Resting potential (charge inside the cell) is maintained at -70mV (this makes for an easy and quick response) This in an active process with Na+ and K+ pumps in the cell wall constantly moving ions to maintain the concentration imbalance Excitatory post synaptic potential = more positive, depolarization Inhibitory post synaptic potential = more negative, hyperpolarization 43 SIGNAL PROCESSING (PROCESSING) Function: Decision to send an action potential or not based on strength of synaptic potential Location: Axon soma (axonal hillock) The decision is based on whether the synaptic potential reaches -50mV Temporal summation: enough signals arrive in short time that it leads to a decrease in the synaptic potential (move faster than the pump) Spatial summation: enough signals arrive from different neurons that the sum exceeds the threshold 44 22

23 ACTION POTENTIAL (TRANSMISSION) Function: Output transmission Location: Axon to terminal buttons All-or-nothing, like a gun Unlike the synaptic potential that is regulated by chemicals, the action potential is voltage regulated Na+ opens and enters K+ opens and enters Na+ closes and K+ stays open Pump works 45 OUTLINE Genetics Communication in the nervous system Resting Potential Action Potential The Synapse Neuroanatomy Studying the Brain 46 23

24 PARTS OF THE NERVOUS SYSTEM 47 HINDBRAIN & MIDBRAIN 48 24

25 FOREBRAIN 49 CEREBRAL CORTEX 50 25

26 CEREBRAL CORTEX 51 CLINICAL OBSERVATIONS Paul Broca Observed brain lesion in left hemisphere of patient with aphasia Carl Wernicke Observed man whose language made no sense 52 26

27 CLINICAL OBSERVATIONS Phineas Gage Famous case Railroad worker Localized brain damage Inappropriate social and moral behaviors Attention and memory fine 53 EVIDENCE OF LATERALIZATION SPLIT BRAIN PATIENTS Some types of epilepsy start in one area of the brain (focus) and spread to other areas. Today, 90% of epilepsy cases are treated with drug therapy. Surgery to remove the epileptic focus or cutting the corpus callosum is rarely used as a last resort. 27

28 OUTLINE Genetics Communication in the nervous system Resting Potential Action Potential The Synapse Neuroanatomy Studying the Brain 55 STUDYING THE BRAIN Neurosurgery Epilepsy Wilder Penfield Split brain - Sperry EEG 56 28

29 IMAGING MRI PET 57 29