UNIT 2: THE BRAIN
INTRODUCTION:
True or False:
Fun Facts about the Brain:
Brains aren’t fully developed until around age 25
Brains weigh on average about 5 lbs.
No pain receptors so you cannot feel pain in your brain
Alzheimer's disease actually makes the brain shrink
People only use 10% of their brains
The brain starts to die without oxygen for two minutes
THE NERVOUS SYSTEM:
 Nervous system regulates our internal
functions
 Central Nervous System: brain and spinal
cord
 Peripheral Nervous System: nerve cells that
send messages between central nervous
system and the rest of the body
 Neurons: Nerve cells that run through our
bodies and communicate with one another
 Over 100 billion in the body, mostly in the
brain
Synapse: junction between two neurons that allows messages
to be sent from one neuron to another
Neurotransmitters: chemicals that are released to connect
two neurons during the synapse process to send messages
 Acetylcholine: Muscle contractions/control
 Endorphins: Pain control & pleasure
 Dopamine: Motor control and reward pleasure
DIFFERENT TYPES OF NERVOUS SYSTEM:
 Central Nervous System:
 Spinal Cord: extends from the brain all the way down the back
 Column of nerves protected by the spine
 Transmits messages from the brain down through the rest of the body
 Peripheral Nervous System:
 Transmits messages from central nervous system across the body
 Somatic Nervous System:
 Transmits sensory messages to the central nervous system
 Responsible for feelings of hot/cold, pain
 Autonomic Nervous System:
 Regulates body’s vital functions like breathing, heartbeat, digestion
THE BRAIN:
Left vs. Right Hemispheres:
Left Hemisphere:
 Considered to be the dominant more logical,
analytical, problem solving hemisphere
Right Hemisphere:
 Considered to be the non-dominant, more
imaginative, artistic and emotional
hemisphere
THE BRAIN:
 Parts of the Brain:
 Hind Brain: located on top of our spinal cord
 Made up of medulla, pons, and cerebellum
 Medulla: responsible for vital functions
 Heart rate, blood pressure, breathing
 Pons: located in front of medulla, responsible for
regulating body movement and alertness
 Cerebellum: responsible for balance and
coordination
 Mid Brain: located in between the hindbrain and the forebrain, involved with hearing
and vision
 reticular activating system: located in midbrain, responsible for attention, sleep and
arousal
 Forebrain:
 Thalamus: rely station for senses like pain, visuals, sounds
 Hypothalamus: responsible for behavior, body temperature regulation,
motivation/emotion, hunger/thirst, aggression
 Limbic System: involved in learning and memory, emotion, hunger, sex, aggression
 Cerebrum: 70% of the brains weight
 Cerebral Cortex: outer layer of cerebrum responsible for thinking, memory,
language
LOBES OF THE BRAIN
Frontal Lobe: lies behind the forehead
Concerned with reasoning, planning,
parts of speech and movement
Includes the motor cortex which is
responsible for muscles in the lower
body
Emotional control center, forms our
personalities and influences our
decisions
LOBES OF THE BRAIN
Parietal Lobe: Located behind
the frontal lobe
Concerned with perception of
stimuli
 Touch, temp., pain, pressure
LOBES OF THE BRAIN
Temporal Lobe:
Located below the frontal and
parietal lobes
Concerned with perception and
recognition of auditory stimuli
(hearing) and memory
 Hippocampus located in temporal lobe
Interprets written and spoken
speech
LOBES OF THE BRAIN
Occipital Lobe: located in the
back of the brain behind the
parietal lobe and temporal lobe
Concerned with aspects of
vision
Lobe
Function
Frontal Lobe
Conscious thought, behavior,
emotion, planning, problem
solving. Most human behaviors
Parietal Lobe
Sensory information like touch,
pressure, temperature.
Temporal Lobe
Senses of smell and sound, as well
processing memories and
understanding language
Occipital Lobe
Sense of sight, perception of visual
stimuli
GENETICS AND HEREDITY
GENETICS
 Heredity: the transmission of characteristics from parents to
offspring
 Transmits physical traits like height, weight, hair color, eye color
 Evidence suggests some psych. traits are inherited as well
 Shyness, leaderships skills, aggressiveness may be inherited to an extent
 It is important to remember that the environment also shapes these
traits as well
 This argument is known as the Nature vs. Nurture argument
GENES AND CHROMOSOMES
 Genes are the basic building blocks of heredity
 Traits are determined by pairs of genes, each from one parent
 Chromosomes: composed of DNA which takes to form of a double helix
 Most normal human cells contain 46 chromosomes that are organized into 23 pairs
 In each pair, one chromosome comes from each parent
 Chromosomes contain instructions that make up our traits
 22 out of 23 chromosomes are similar in males and females
 The 23rd chromosome is known as the sex chromosome
 X chromosome=male, Y chromosome=female
 An incorrect pairing of chromosomes can lead to
physical and behavioral disorders
 When there is an extra chromosome in the 21st pairing it
leads to Down Syndrome
NATURE VS. NURTURE
 Nature: we are mostly shaped by our inherited biological
makeup
 Nurture we are mostly shaped by our environment and
upbringing
 Family, education, culture, living conditions, individual
experience
 Most psychologists agree that nature and nurture both influence
us
 A person may be born with the inherited intelligence to become
a brilliant writer but may never become a writer if they are never
taught to read or write
 Some psychologists believe intelligence is mostly determined by genetics
 Controversial, our destinies may be pre-determined by our biology
 The best way to test the extent of nature/nurture is to compare kinship
 Degree of how much people are related
 Identical twins share 100% of their genes
 Parent and sibling share 50% of their genes…
 By studying traits of family members and comparing the results, psychologists
hope to discover how genes impact us
 By studying twins and adopted children psychologists test how much genetics
determine our behavior
 Twin Studies:
 If differences exist in identical twins, it must be from environmental forces
 Share 100% of their genetic makeup
 Regular siblings and even fraternal twins only share 50% of their genetic
makeup so their differences can be from both heredity and the environment
 Research shows identical twins tend to resemble each others traits more so than
typical siblings
 Personality traits tend to be more similar
 The problem here is that both twins tend to grow up with the same
environmental forces
 Adoptee studies:
 Adopted children do not share any genetics with their adopted parents
 By comparing an adopted child’s traits to their adopted parents traits
psychologists try to determine how their environment has impacted them
 Psychologists also try to compare the adopted child’s traits to their biological
parents to see how much of their biological makeup is still impacting them
 If adopted children act more like their biological parents nature is winning and
visa versa
PERCEPTION AND SENSATION
 Sensation: stimulation of sensory receptors and the transmission of sensory
information to the central nervous system
 If you stub your toe, the sensory neurons in your skin communicate to your brain
 Senses are stimulated by sources like light and sound (vision and hearing) and
chemicals (taste and smell)
 When you stub your toe, your brain perceives this pain
 Perception: psychological process in which your brain interprets sensory
information
 Perception is built from our experiences, learning and attitudes
 Absolute Threshold: weakest amount of a stimulus that can be sensed
 Taste, hearing vision, smell, touch all have different absolute thresholds
depending on the person
 Difference Threshold: minimum amount of difference that can be detected
between two stimuli
 Distinguishing colors, tastes, smells apart from others
 Signal-detection theory: perception of sensory stimuli may differ depending on
setting, your physical state, your mood/attitude
 Food may have no taste when your sick, you may not be able to hear a
conversation at a party
 We focus on whatever is important and ignore distracters
Sense
Stimulus
Receptors
Threshold
Vision
Electromagnetic energy
Rods and cones in the retina
A candle flame viewed 30
miles away on a dark night
Hearing
Sound Waves
Hair cells of the inner ear
The ticking of a watch from 20
feet away in a quiet room
Smell
Chemical substances in the air Receptor cells in the nose
About one drop of perfume
diffused throughout a house
Taste
Chemical substances in saliva
Taste buds on the tongue
About one teaspoon of vanilla
in a desert
Touch
Pressure on the skin
Nerve endings in the skin
The feeling of a fly landing on
your arm
 Sensory adaptation:
 We become more sensitive to weak stimuli and
less sensitive to unchanging stimuli
 In a dark movie theater we eventually are able
to adapt to the darkness to see the people
around us
 City dwellers become less sensitive to the
sounds of the city
 Vision:
 Light: electromagnetic energy in wavelengths
 Humans only see a small part of the light spectrum
 Colors of the spectrum in order from longest to shortest wavelengths
 Red, orange, yellow, green, blue, indigo, violet (ROY G. BIV)
 Light enters the eye and projects into the pupil
 Pupils are actually openings and they adjust depending on the amount of light entering the
eye
 Once light enters the eye it encounters the lens
 Adjusts to distance of objects by changing its thickness
 These changes project onto the retina
 Acts like the film of a camera but with neurons
 Photoreceptors are neurons that react to light
 When light reaches the photoreceptors, the optic nerve carries the
visual to the brain
 The point where the optic nerve reaches the eye is called the blind spot
 It has no photoreceptors so it does not register anything
 We all have a blind spot and it is vital, otherwise the optic nerve could
never connect to the eye and we would not see anything
Rods and Cones:
Two kinds of photoreceptors
Rods: sensitive only to the brightness of light
Allow us to see black and white
Cones: provide color vision
 Color Vision: color is determined by the wavelength of light
 Cones only see blue, red, and green
 When more than one cone is stimulated at the same time we see
other colors like yellow or violet
 Color tv’s work in this same way
 Every pixel on a TV is either red, blue or green
 Other colors only exist when these pixels combine to create other
colors
 Colorblindness:
 Malfunction or absence of certain cones cause colorblindness
 Total colorblindness means people see in black and white, this is rare
 Partial colorblindness is common
 Hearing:
 Interpretation in the brain of soundwaves
 Soundwaves come in various pitches and loudness
 Higher pitch=shorter soundwave
 Louder sound=higher amplitude of soundwaves
 The ear takes sound waves, vibrates them throughout
various parts of the ear and sends them to the brain
through the auditory nerve
 Smell:
 Important in taste
 Onions and apples taste very similar,
only differences are in their smells
 Odors are detected by neurons in the
nostril and sent to the brain through the
olfactory nerve
 Taste:
 Sweet, salty, sour, bitter are the 4 tastes
 Sensed through receptor neurons on our
taste buds