Unit 2 - biological basis of behavior PDF

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Module 2b- Biological & Developmental Bases of Behaviour Genetic Principles 1. The genetic message is contained in chromosomes (which are threadlike structures found in the nucleus of every cell). Each chromosome carries many genes. Chromosomes are made of DNA (which contains the genetic blueprint for each individual). A gene is a section of a DNA. 2. Genes control the characteristics of the body, e.g. eye colour & height etc., 3. Human cells (except for sex cells (sperm and egg) consist of 23 pairs of chromosomes, half contributed by the mother's egg, half by the father's sperm 4. The 23rd pair of chromosomes which determine a person’s sex, male or female. X female; Y male is determined by the father.

I. THE NERVOUS SYSTEM Has two main branches, the Central Nervous system and the Peripheral Nervous system.

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The Central Nervous System Its Function :--receives, processes, interprets, and stores incoming information; sends out messages to muscles, glands, internal organs b. Consist of :--brain and spinal cord – The central nervous system acts as the central executive of the body; decisions are made here, and messages are communicated to the rest of the body via nerves (bundles of axons); the nerves outside the brain and spinal cord form the peripheral nervous system

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B. The Peripheral Nervous System--nervous system outside brain and spinal cord a. Its Functions i. Sensory nerves (afferent neurons)--bring input from skin, muscles, and organs ii. Motor nerves—(efferent neurons)--carry output to muscles, glands, and organs – Afferent nerve pathways move information toward the brain and spinal cord; efferent pathways carry central nervous system messages to muscles and glands. b. Divisions of the Peripheral Nervous System 1. Somatic nervous system a) Nerves connected to sensory receptors b) Nerves connected to skeletal muscles--voluntary action –

The somatic system consists of nerves that bring sensory information to the brain and nerves that connect to muscles needed to initiate movement

2. Autonomic nervous system--works automaticallyinvoluntary action e.g. breathing & digestion. Functions--regulates blood vessels, glands, organs (heart, stomach, bladder & lungs) I. Divisions of the Autonomic Nervous system (a) Sympathetic--mobilizes the bodily resources and increases the output of energy during emotion, stress and emergencies. (Increases the heart rate) (b) Parasympathetic—conserves the body’s resources and allows the body to relax and store energy (decreases the heart rate) II. COMMUNICATION IN THE NERVOUS SYSTEM A. Components of the nervous system

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Glial cells—cells that hold neurons in place; they also nourish and insulate neurons (create the myelin sheath for the neurons) Neurons--cells that communicate to, from, or within the CNS. They are the basic units of the nervous system. The structure of the neuron a) Dendrites--receive messages from other neurons, transmit to cell body b) Cell body--keeps the neuron alive, determines whether to fire c) Axon--transmits messages away from cell body to other neurons:  Ends in branches or axon terminals  Many axons are insulated by a fatty material (myelin sheath)  Bundles of axons in the peripheral nervous system form nerves

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The basic building blocks of the nervous system are neurons. There are three main types Cell i. Sensory body ons make the initial contact with the environment, carrying signals to the brain ii. Interneurons, the most plentiful type, convey information from one internal processing site to another iii. Motor neurons carry messages and commands away from the central nervous system to the muscles and glands B.

How neurons communicate Neurons communicate across Synapse = axon terminal + synaptic cleft (small space between one axon and next dendrite) + covering membrane of receiving dendrite or cell body – Many thousands of neurons may communicate at a synapse

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Wave of electric voltage, called action potential, moves down axon to end of axon terminal, called synaptic end bulb Action potentials travel more rapidly in myelinated axons than in unmyelinated axons Synaptic end bulb releases chemical neurotransmitters (transmitters) which have been stored in synaptic vesicles (sacs in the end bulb) Transmitters cross the synaptic cleft and briefly lock onto receptor sites on the receiving dendrites They can increase or decrease the likelihood that the receiving neuron will generate an action potential Receiving neuron averages the excitatory and inhibitory incoming messages to determine if it reaches firing threshold Neurons either fire or do not fire (all or none); the strength of firing does not vary

C. Chemical messengers in the nervous system (Neurotransmitters) Neurotransmitters exist throughout the body Some better understood neurotransmitters and some of their effects (1) Serotonin--sleep, mood, eating (2) Dopamine--movement, learning, memory, emotion [pleasure] (3) Acetylcholine--muscle action, memory, emotion (4) Norepinephrine--heart rate, learning, memory...