module 4 incredible nervous system. genes & evolution genetic information –brain and body...

Module 4

Incredible Nervous System

GENES & EVOLUTION

• Genetic information– brain and body developed according to complex

chemical instructions that were written in a human cell no larger than a grain of sand

GENES & EVOLUTION (CONT.)

• Fertilization– human life has its beginnings when a father’s sperm,

which contains 23 chromosomes, penetrates a mother’s egg, which contains 23 chromosomes


• Zygote– the largest human cell, about the size of a grain of

sand– a zygote is a cell that results when an egg is fertilized– a zygote contains 46 chromosomes arranged in 23

pairs


• Chromosomes– a short, rodlike, microscopic structure that contains a

tightly coiled strand of the chemical DNA, which is an abbreviation for deoxyribonucleic acid


• Chemical alphabet– each chromosome contains a long, coiled

strand of DNA, which resembles a ladder that has been twisted over and over upon itself

– each rung of the DNA ladder is made up of four chemicals

– the order in which the four different chemicals combine to form rungs creates a microscopic alphabet


• Genes and proteins– Gene

• a specific segment on the long strand of DNA that contains instructions for making proteins

– Proteins• chemical building blocks from which all the parts of

the brain and body are constructed


• Genome– The Human Genome Project– began in 1995 and cost over $2.7 billion– reached its first goal in 2003 of mapping all the

human genes– researchers found only about 30,000 human genes

instead of the estimated 100,000– It is a blue print of genes


• Genetic factors– researchers are discovering how genetic factors

interact with the environment to result in the development of mental retardation, emotional and personality traits, mental disorders, and various cognitive abilities

EVOLUTION OF THE HUMAN BRAIN

• Evolution of the human brain– 1859 Charles Darwin published the Origin of Species

• Theory of Evolution– says that different species arose from a common

ancestor and that those species that survived were best adapted to meet the demands of their environment

– humans and chimpanzees share at least 98% of their DNA


• Australopithecus (Lucy)– 3-4 million years ago– brain weight 500 grams (size of a chimp)

• no tools, no language, no fire

• Homo erectus– 1.5 million years ago– brain weight 1,000 grams

• Stone tools (possibly language)

• Homo sapiens– 400,000 years ago– brain weight 1350 grams or 3 pounds

STUDYING THE LIVING BRAIN

• Brain scans– techniques that can look through the thick skull and

picture the brain with astonishing clarity yet cause no damage to the extremely delicate brain cells

– researchers are mapping a variety of cognitive functions:

– attention, language, memory, motor skills

STUDYING THE LIVING BRAIN (CONT.)

• MRI– magnetic resonance imagery– involves passing nonharmful radio frequencies

through the brain• fMRI

– functional magnetic resonance imaging– measures the activity of specific neurons that are

functioning during cognitive tasks, such as thinking, listening


• Brain scans and Cognitive Neuroscience– PET scan– positron emission tomography– involves injecting a slightly radioactive solution into

the blood and then measuring the amount of radiation absorbed by brain cells called neurons


• Brain scans and Cognitive Neuroscience– Neuroimaging

• PET and fMRI scans are used to identify and map the living brain’s neural activity as a person performs complex behavioral and cognitive tasks, such as:

– seeing– moving– thinking– speaking– empathizing– trusting– even reacting to TV violence


• Tools versus Animals– naming animals– naming tools

ORGANIZATION OF THE BRAIN

• Divisions of the Nervous System• Major divisions of the nervous system

– central nervous system - CNS– peripheral nervous system - PNS

ORGANIZATION OF THE BRAIN (CONT.)

• Central nervous system - CNS– made up of the brain and spinal cord


• Peripheral nervous system - PNS– includes all the nerves that extend from the spinal

cord and carry messages to and from various muscles, glands, and sense organs located throughout the body

• Subdivisions of the PNS– somatic nervous system– autonomic nervous system - ANS– sympathetic division– parasympathetic division


• Somatic nervous system– network of nerves that connect either to sensory

receptors or to muscles that you can move voluntarily, such as muscles in your limbs, back, neck, and chest

– nerves contain two kinds of fibers• Afferent

– sensory fibers; carry information to the brain• Efferent

– motor fibers; carry information from brain or spinal cord to the muscles


• Autonomic nervous system - ANS– regulates heart rate, breathing, blood pressure,

digestion, hormone secretion, and other functions• Sympathetic division

– triggered by threatening or challenging physical or psychological stimuli, increases physiological arousal and prepares the body for action (epinephrine)

• Parasympathetic division– returns the body to a calmer, relaxed state and is

involved in digestion (norepinephrine) = Homeostasis

LIMBIC SYSTEM: OLD BRAIN (CONT.)


• Forebrain– largest part of the brain– has right and left sides called hemispheres– hemispheres are responsible for a number of

functions, including learning and memory, speaking and language, emotional responses, experiencing sensations, initiating voluntary movements, planning, and making decisions


• Midbrain– has a reward or pleasure center, which stimulated by

food, sex, money, music, looking at attractive faces, and some drugs (cocaine)

– has areas for visual and auditory reflexes– contains the reticular formation, which arouses the

forebrain so that it is ready to process information from the senses


• Hindbrain– Has three distinct structures:

• Pons• Medulla• Cerebellum


• Pons– functions as a bridge to interconnect messages

between the spinal cord and brain• Medulla

– located on top of the spinal cord– includes a group of cells that control vital reflexes,

such as respiration, heart rate, and blood pressure• Cerebellum

– located in the very back and underneath the brain– involved in coordinating motor movements but not in

initiating voluntary movements

CONTROL CENTERS: FOUR LOBES

• Wrinkled cortex– a thin layer of cells that essentially covers the entire

surface of the forebrain

CONTROL CENTERS: FOUR LOBES (CONT.)


• Four lobes– Frontal lobe– Parietal lobe– Occipital lobe– Temporal lobe


• Frontal lobe– involved with personality, emotions, and motor

behaviors, decision making• Parietal lobe

– involved with perception and sensory experiences• Occipital lobe

– involved with visual processing• Temporal lobe

– involved with hearing and speaking


• Frontal lobe: functions– Phineas Gage

• http://www.youtube.com/watch?v=MvpIRN9D4D4• Frontal Lobotomy

– A surgical procedure in which about one-third of the front part of the frontal lobe was cut away from the rest of the brain

– 18,000 were performed during the 1940s and 1950s

http://www.youtube.com/watch?v=MvpIRN9D4D4


• Frontal lobe: functions– motor cortex– narrow strip of cortex that is located on the back edge

of the frontal lobe and extends down its side– involved in the initiation of all voluntary movements– right side controls left– left side controls right– organization and function of motor cortex


• Other functions of frontal lobe– much knowledge of other frontal lobe functions comes

from individuals who had damage to that area– frontal lobes are involved in paying attention,

organizing, planning, deciding, and carrying out various cognitive tasks and social-emotional behaviors

– executive function


• Parietal lobe: function– location of somatosensory cortex– narrow strip of cortex that is located on the front edge

of the parietal lobe and extends down its side


• Other functions of parietal lobe– involved in several cognitive functions, including

recognizing objects, remembering items, and perceiving and analyzing objects in space


• Temporal lobe: functions– primary auditory cortex– located on top edge of each temporal lobe, receives

electrical signals from receptors in the ears and transforms these signals into meaningful sound sensations, such as vowels and consonants


• Temporal lobe: functions– auditory association area– located directly below the primary auditory cortex– transforms basic sensory information, such as noises

or sounds, into recognizable auditory information, such as words or music


• Temporal lobe: functions– Broca’s area - frontal lobe

• located in left frontal lobe• necessary for combining sounds into words and

arranging words into meaningful sentences• damage: Broca’s aphasia

– person cannot speak in fluent sentences but can understand written and spoken words


– Wernicke’s area• located in the left temporal lobe• necessary for speaking in coherent sentences and

for understanding speech• Damage: Wernicke’s aphasia

– difficulty in understanding spoken or written words and a difficulty in putting words into meaningful sentences


• Occipital lobe: functions– vision– primary visual cortex– located at the very back of the occipital lobe– receives electrical signals from receptors in the eyes

and transforms these signals into meaningless basic visual sensations, such as lights, lines, shadows, colors, and textures


• Occipital lobe: functions– visual association area– transforms basic sensations, such as lights, lines,

colors, and textures, into complete, meaningful visual perceptions, such as persons, objects, or animals

LIMBIC SYSTEM: OLD BRAIN

• group of about half a dozen interconnected structures that make up the core of the forebrain

• involved with regulating many motivational behaviors such as obtaining food, drink, and sex

• organizing emotional behaviors such as fear, anger, and aggression; storing memories

• Structures and functions– Hypothalamus– Amygdala– Thalamus– Hippocampus


• Hypothalamus– regulates many motivational behaviors, including

eating, drinking, and sexual responses; emotional behaviors such as arousing the body when fighting or fleeing, and secretion of hormones, such as occurs at puberty

• Amygdala– located in the tip of the temporal lobe– receives input from all the senses– evaluates the emotional significance of stimuli and

facial expressions, especially those involving fear, distress, or threat


• Thalamus– gathers and processes information from the senses– involved in receiving sensory information, doing some

initial processing, and then relaying the sensory information to areas of the cortex

• Hippocampus– curved structure inside the temporal lobe– Involved in saving many kinds of fleeting memories by

putting them into permanent storage in various parts of the brain

module 4 incredible nervous system. genes & evolution genetic information –brain and body...

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