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CHAPTER 3 OUTLINE BIOLOGICAL PROCESSES. Part 1. I. Communicating Internally: Connecting World and Brain A. Main components of the nervous system Sensory neurons – Neurons which make contact with the environment and carry signals toward the brain

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part 1

CHAPTER 3 OUTLINE

BIOLOGICAL PROCESSES

Part 1

slide2

I. Communicating Internally: Connecting World and Brain

    • A. Main components of the nervous system
      • Sensory neurons – Neurons which make contact with the environment and carry signals toward the brain
      • Interneurons – The most plentiful neurons in the nervous system. They convey information from one internal processing site to another.
      • Motor neurons –Neurons which carry messages and commands away from the central nervous system to the muscles and glands.
      • Glial cells – These cells are not directly involved in communicating signals, but help to maintain neurons. Glial cells comprise the myelin sheath, which insulates neurons and speeds neural communication
      • Reflexes– Automatic reactions that are controlled by the spinal cord pathways. Reflexes require no initial input from the brain. Reflex path:
      • sensory neurons interneurons motor neurons
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B. Anatomy of neurons

      • 1. Dendrites – Branch-like fibers that receive chemical information from other neurons
      • 2. Soma – The main body of the neuron cell that processes chemical information received from the dendrites. The soma also stores the cell’s genetic material (DNA)
      • 3. Axon – The long tail-like part of a neuron that transmits electrochemical signals from the soma
        • a. action potential – The electrochemical message that fires from the axon hillock through the axon to the terminal buttons
        • b. terminal buttons – Tiny swellings at the end of the axon which contain neurotransmitters to be released into the synaptic gap
  • 4. Synapse – the tiny fluid filled gap between neurons
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C. Neural Transmission: The Electrochemical Message

1. Flow of the electrochemical message – the electrochemical message is picked up by the dendrites,organized in the soma, released through the axon and exits through the terminal buttons

2. Resting potential – the tiny electrical charge in place between the inside and the outside of resting neurons

a. sodium & potassium ions – contain a positive charge

b. chloride ions – contain a negative charge

c. sodium-potassium pump – maintains a slight negative charge inside the neuron (- 70 mv)

3. Generating an action potential – if the charge inside the neuron becomes less negative (moving toward “0”) an all or none firing of an action potential occurs

a. excitatory messages – (depolarization) ion channels open, the charge moves toward “0” (becomes less negative) and an action potential fires through the axon

b. inhibitory messages – (hyperpolarization) the charge inside the neuron becomes more negative (moving toward resting potential) and the action potential does not fire

c. characteristics of the action potential – it fires in an “all or none” fashion through the axon like a gun with consistent intensity

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4. Neurotransmitters: The Chemical Messengers – neurotransmitters are molecules which interact chemically with the post synaptic membrane of other neurons

a. acetylcholine – a neurotransmitter which acts as a major messenger in the central and peripheral nervous system. Alzheimer's disease is related to a lack of acetylcholine production in the brain

b. dopamine – a neurotransmitter which produces mostly inhibitory effects that stabilize neural communication

(1.) schizophrenia – a disease which results from excessive dopamine levels in the brain. Drugs that decrease dopamine levels; reduce schizophrenic symptoms such as hallucinations and delusions

(2.) Parkinson’s disease – the drug Levadopa (L-Dopa) is used to increase dopamine levels in Parkinson’s patients; reducing tremors and other movement problems

c. serotonin – a neurotransmitter that affects sleep, dreaming and general arousal (awareness). Depression and OCD are related to an imbalance in serotonin levels in the brain

d. GABA – (gamma amino-butyric acid) a neurotransmitter which is involved in regulation of anxiety. Tranquilizers such as Valium are used to regulate GABA in the brains of people with anxiety disorders

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5. Drugs and the Brain

a. agonists – mimic the action of neurotransmitters

example; Nicotine mimics the action of acetylcholine

b. antagonists – block the effects of neurotransmitters

example; Blow darts tipped with curare block acetylcholine and cause

paralysis

c. endorphins – Morphine-like chemicals in the brain that are released to kill pain

example; Runner’s high occurs when a rush of endorphins is released by the brain

D. The Communication Network – Involves the operation of thousands of neurons in concert to produce thoughts, feelings, and actions.

1. pattern of activation – groups of neurons operating at the same time to produce conscious experience

2. firing rate – the number of action potentials that a neuron can produce per unit of time

3. refractory period – the unit of time it takes for a neuron to regenerate another action potential

E. Neural Networks – computer simulation models of neural communication networks in the brain to represent brain activity

part 2

CHAPTER 3 OUTLINE

BIOLOGICAL PROCESSES

Part 2

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II. Initiating and Coordinating Behavior: A Division of Labor

  • The Central and Peripheral Nervous System
  • 1. The central nervous system – includes the brain and spinal cord which act as the central executive of the body
  • (a.) nerves – bundles of axons that communicate messages throughout the body
  • 2. The peripheral nervous system – all the nerves outside the brain and spinal cord
  • (a.) afferent nerve pathways – (sensory pathways) neural information travels toward the brain and spinal cord
  • (b.) efferent nerve pathways – (motor pathways) carry messages away from the brain and spinal cord
  • (c.) somatic nervous system – carries sensory nerve information toward the brain and controls mostly voluntary muscle movement
  • (d.) autonomic nervous system – controls automatic body functions such as heart rate, blood pressure, respiration, and digestion
  • * sympathetic division – part of the autonomic system that prepares the body for emergencies by increasing heart rate, respiration etc. (fight or flight response)
  • * parasympathetic division – part of the autonomic system that calms the body down, returns it to normal after an emergency
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B. Determining Brain Function

1. Brain Damage and Lesion

(a.) Observation of characteristics – to learn about how the brain functions normally, researchers study brain damaged individuals

(b.) Broca’s Aphasia - an individual with brain damage to Broca’s area – understands spoken language but cannot accurately produce spoken language

(c.) Wernicke’s Aphasia – an individual with damage to Wernicke’s area – cannot accurately understand spoken language

(d.) Lesioning – researchers may selectively damage areas of an animal’s brain to see how it affects behavior

2. Devices to Study the Brain

(a.) EEG – (Electroencephalograph) device which records gross (general) electrical activity in regions of the brain

(b.) CT Scan – (Computerized Tomography) device which provides pictures of brain structures using X-rays

(c.) PET scan – (Positron Emission Tomography) device which looks at the active brain as it operates using a radioactive substance (dye)

(d.) MRI – (Magnetic Resonance Imaging) device which isolates the structures and functions of the brain in 3-D images using magnetism without radioactive dye

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C. Brain Structures and Their Function

1. Hindbrain – provides basic life support for the body, considered the most primitive region of the brain (Reptilian Brain)

(a.) Medulla and Pons – these areas in the hindbrain maintain basic life support functions such as heart rate, blood pressure, respiration, and certain reflexes

(b.) Reticular Formation – a network of nerves in the hindbrain that controls general arousal (sensory awareness)

(c.) Cerebellum – (little brain) the structure in the hindbrain that is involved in planning and coordination of complex motor skills

2. Midbrain – the midbrain structures serve as neural relay stations (a.) Tectumcolliculus (superior and inferior) – midbrain structure which relays auditory and visual information and coordinates sensory input

(b.) Substantianigra – midbrain structure which releases dopamine and acts as a center for motor control (area likely damaged by Parkinson’s disease)

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3. Forebrain – area of the brain involved in higher order mental processes

(a.) Cerebral cortex – forebrain area that forms the entire outer layer of the brain and makes up 80% of the brain’s overall volume (Mammalian Brain)

(b.) Thalamus – egg-shaped structure in both hemispheres of the forebrain that gathers and relays all sensory input (except smell)

(c.) Hypothalamus – tiny forebrain structure beneath the thalamus that regulates motivational activities such as eating, drinking, body temperature, and sexual arousal

(d.) Limbic system – part of the forebrain involved in emotional, defensive, and motivational responses

* amygdala – limbic structure that controls aggressive and defensive behaviors

* hippocampus – limbic structure that is important in the formation and retrieval of memories

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4. Cerebral cortex – the outermost layer of the cerebrum that is the seat of higher order mental functions, divided into the left and right hemispheres

(a.) Corpus callosum – the thick bundle of nerves that serves as the neural communication bridge between the left and right hemispheres

( b.) The hemispheres – The left cerebral hemisphere controls sensory and motor functions on the right side of the body. The right hemisphere controls the left side of the body.

* frontal lobes – area in the front of the brain that processes higher order thinking such as planning, decision-making, and personality. Also contains the motor cortex which controls voluntary muscle movements

* parietal lobes – central area of the cerebrum which contains an area called the somatosensory cortex for sensing touch, temperature, pain etc.

* temporal lobes – areas located on the left and right sides of the brain which process auditory information, speech ,and language. The left temporal lobe contains the primary speech center

* occipital lobes – area located in the back of the brain which processes visual information such as color, motion, and form