CH 2 - BIOLOGY AND BEHAVIOR

CH 2 - BIOLOGY AND BEHAVIOR - BIOLOGY AND BEHAVIOR CHAPTER...

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BIOLOGY AND BEHAVIOR CHAPTER TWO Neuroscience The brain and the nervous system guide our interaction with the world around us, move the body through the world, and direct our adaptation to our environment. Those who study the brain and the nervous system are called Neuroscientists. NEURON A specialized cell that conducts impulses through the nervous system and contains three major parts: 1. Cell body Contains nucleus and carries out metabolic functions of the neuron 2. Dendrites Branchlike extensions of the cell body Receive and send messages from other neurons 3. Axon Slender, tail-like extension of the neuron Transmits signal to dendrites or cell body of other neurons, to muscles, glands, and other body parts NEURONS STRUCTURE OF A NEURON Glial cells Specialized cells in the brain and spinal cord Hold neurons together Remove waste (dead neurons) and do clean-up tasks 1
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Perform manufacturing and nourishing activities Synapse Junction where axon terminal of a sending neuron communicates with a receiving neuron across the synaptic cleft Synaptic cleft Tiny, fluid-like gaps separating axon terminals from receiving neurons NEURONS TYPES OF NEURONS Afferent neurons (sensory) Relay information from the senses to the brain and spinal cord Eyes, ears, nose, mouth, and skin Efferent neurons (motor) Send information from the central nervous system to the glands and muscles Enables the body to move Interneurons Carry information between neurons In the brain In the spinal cord Reflexes Inborn automatic responses to a sensory stimuli. Knee-jerk reflex Tap on the knee sends sensory signal to spinal cord Sends motor signal to muscle
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Tap, kick! Withdrawal reflex Touch hot or prickly object, hand will immediately pull away. Sensory and motor neurons linked by an interneuron. COMMUNICATION BETWEEN NEURONS Neurotransmitters Chemical substances released into the synaptic cleft from the axon terminal of a sending neuron Cross a synapse, Bind to appropriate receptor sites on dendrites or cell body of a receiving neuron Influence a cell to either fire or not fire COMMUNICATION BETWEEN NEURONS Receptors Protein molecules on surface of dendrites and cell bodies Have distinctive shapes Only interact with specific neurotransmitters Reuptake Neurotransmitters taken from the synaptic cleft back into the axon terminal for later use Terminates the excitatory or inhibitory effect on the receiving neuron COMMUNICATION BETWEEN NEURONS The Rate of Neural Firing and the Speed of the Impulse A weak stimulus may cause few neurons to fire and at a slow rate 3
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A strong stimulus may cause thousands of neurons to fire at the same time and at hundreds of times per second Impulses travel at speeds from about 1 meter per second to approximately 100 meters per second
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CH 2 - BIOLOGY AND BEHAVIOR - BIOLOGY AND BEHAVIOR CHAPTER...

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