Transcript 02biologya
Biology and Behavior Chapter 2 Part I The Biological Perspective • Psychological approach that emphasizes bodily events and changes associated with actions, feelings and thoughts. • This perspective involves such topics as: – – – – – – The nervous system Neurons & neurotransmitters Hormones Brain chemistry Heredity Evolutionary influences The Nervous System • Two parts of a nervous system – Central nervous system • The brain and the spinal cord – Peripheral nervous system • Connects the central nervous system to all other parts of the body The Central Nervous System • Brain. • Spinal cord. – A collection of neurons and supportive tissue running from the base of the brain down the center of the back – Protected by spinal column. Central Nervous System Peripheral Nervous System • Peripheral nervous system (PNS) – The nerves connecting the central nervous system to the rest of the body – Contains two subdivisions • Somatic division • Autonomic division – contains two divisions – Sympathetic division – Parasympathetic division Peripheral Nervous System Peripheral Nervous System • Somatic – Includes the nerves that are connected to sensory receptors and skeletal muscles. • Autonomic – The sympathetic nervous system mobilizes bodily resources and increases the output of energy during emotion and stress. – The parasympathetic nervous system operates during relaxed states and that conserves energy. Neurons and the Neurotransmitters • Neuron – A specialized cell that conducts impulses through the nervous system and contains three major parts—a cell body, dendrites, and an axon Structure of a Neuron • Dendrites – receive information from other neurons and transmit towards the cell body • Cell body – keeps the neuron alive and determines whether it will fire. • Axon – extending fiber that conducts impulses away from the cell body and transmits to other cells. Structure of a Neuron • Myelin Sheath – Fatty insulation that may surround the axon of a neuron. How Neurons Communicate • Axon terminals release neurotransmitter. • Neurotransmitter enters synaptic gap. • Neurotransmitter binds to receptors that it fits. Neurons and the Neurotransmitters • Glial cells – Cells that help to make the brain more efficient by holding neurons together, removing waste products such as dead neurons, making the myelin coating for the axons, and performing other manufacturing, nourishing, and cleanup tasks – Synapse – The junction where the axon of a sending neuron communicates with a receiving neuron across the synaptic cleft Action Potential • A brief change in electrical voltage which occurs between the inside and outside of an axon when a neuron is stimulated. It produces an electrical impulse. Action Potential Neurotransmitters • Neurotransmitter – A chemical that is released into the synaptic cleft from the axon terminal of a sending neuron, crosses a synapse, and binds to appropriate receptor sites on the dendrites or cell body of a receiving neuron, influencing the cell either to fire or not to fire • Receptors – Protein molecules on the dendrite or cell body of a neuron that will interact only with specific neurotransmitters Neurotransmitters • A chemical substance that is released by a transmitting neuron at the synapse and that alters the activity of a receiving neuron. Neurotransmitters • Action of neurotransmitters – Excitatory • Influencing the neurons to fire – Inhibitory • Influencing neurons not to fire Major Neurotransmitters • Serotonin – A neurotransmitter that plays an important role in regulating mood, sleep, aggression, and appetite • Dopamine – A neurotransmitter that plays a role in learning, attention, and movement • Acetylcholine (ACh) – A neurotransmitter that plays a role in learning, memory, and rapid eye movement (REM) sleep and causes the skeletal muscle fibers to contract – Glutamate – Primary excitatory neurotransmitter in the brain Major Neurotransmitters • Epinephrine – A neurotransmitter that affects the metabolism of glucose and energy stored in muscles to be released during exercise • Norepinephrine – A neurotransmitter affecting eating and sleep Major Neurotransmitters • Glutamate – Main excitatory neurotransmitter in the brain • Gamma amino butryic acid (GABA) – Main inhibitory neurotransmitter in the brain • Endorphins – Chemicals produced naturally by the brain that reduce pain and positively affect mood – “Runner’s high” is attributed to the release of endorphins