Transcript General Psychology Chapter 2 - Sarah Rach

General Psychology
Chapter 2
Neuroscience & Behavior
Sarah Rach
• Everything psychological – every idea, every
mood, every urge – is simultaneously
biological
“To think, feel, or act without a body
would be like running without legs.”
Neural Communication
• The reason we can study other
animals
• Human brain = monkey brain
• Our brains are more complex
than a rat’s but both follow the
same principles
Neurons
• Neuron: a nerve cell – the building block of
the nervous system
• Dendrite: bushy, branching extensions of a
neuron that receive messages and conduct
impulses toward the cell body (LISTENS)
• Axon: the extension of a neuron, ending in
branching terminal fibers, through which
messages pass to other neurons or to
muscles or glands (SPEAKS)
• Can be very long (several feet)
• Neuron carrying orders to a leg muscle =
basketball attached to a rope 4 miles long
A Motor Neuron
Neurons continued…
• Action Potential: a neural impulse; a brief electrical charge
that travels down an axon
• 2 miles per hour – 200 miles per hour
• Excitatory signals: like pushing a neuron’s accelerator
• Inhibitory: like pushing its break
• Threshold: the minimum intensity of a neuron
• If the excitatory signals minus inhibitory signals exceeds the
threshold – the signals combined trigger an action potential
• All-or-None: increasing the level of stimulation above the
threshold will not increase the neural impulse’s intensity
• More can be fired
• They can fire more often
• So we can differentiate between gentle or hard sensations
How Neurons Communicate
• Synapse: the junction between the
axon tip of the sending neuron and the
dendrite or cell body of the receiving
neuron
• The tiny gap at this junction is called
the synaptic gap or cleft
• Less than one millionth of an inch
wide
How Neurons Communicate
How Neurons Communicate
• Dendrites and axons don’t quite touch…so
how do they communicate?
• Neurotransmitters: chemical messengers that
traverse the synaptic gaps between neurons
• When released by the sending neuron,
neurotransmitters travel across the synapse and
bind to receptor sites on the receiving neuron,
thereby influencing whether that neuron will
generate an impulse
• Reuptake: the sending neuron normally reabsorbs
excess neurotransmitter molecules
Neurotransmitters
• Acetylcholine (Ach): one of the best-understood
neurotransmitters
• Is the messenger at every junction between a motor neuron
and skeleton muscle
• When Ach is released to our muscle cells, the muscle
contracts
• Endorphins (endogenous produced within morphine)
• Natural opiates released in response to pain and vigorous
exercise
• “runner’s high”
• Painkilling effects of acupuncture
• Indifference to pain in some severely injured people
Drugs & Chemicals Affect
on Neurotransmitters
• Agonists: Excite
• similar enough to a neurotransmitter to mimic its effects or it
may block the neurotransmitter’s reuptake
• Antagonists: inhibit
• Inhibit a neurotransmitter’s release from the sending neuron
• Others are enough like the neurotransmitter to occupy its
receptor site and block its effect, but are not similar enough
to stimulate the receptor
• Foreign coins that fit into, but won’t operate, a pop or candy
machine
• Blood-Brain Barrier: fences out unwanted chemicals
circulating in the blood
• Makes it difficult to create new drugs to be used to treat
disorders because they can’t cross the barrier
The Nervous System
• Central Nervous System
(CNS)
• Brain and spinal cord
• Peripheral Nervous System
(PNS)
• Links the central nervous
system with the body’s
sensory receptors, muscles,
and glands
• Nerves
• Neural “cables” containing
many axons
Information travels in the nervous system
through three types of neurons
• Sensory Neurons – carry messages from
the body’s tissues and sensory organs
inward to the brain and spinal cord, for
processing
• Motor Neurons – neurons that carry
outgoing information from the central
nervous system to the muscles and glands
• Interneurons – central nervous system
neurons that internally communicate and
intervene between the sensory inputs and
motor outputs
Peripheral Nervous System
Peripheral Nervous System
• Somatic Nervous System
• Enables voluntary control of our skeletal
• Autonomic Nervous System
• Controls our glands and the muscles of our internal organs
(glandular activity, heartbeat, digestion)
• Automatic pilot (autonomously) – but may be consciously
overridden
• Sympathetic: arouses and expends energy – gets your ready
for action
• Accelerate your heartbeat, raise your blood pressure, slow your
digestion, raise you blood sugar, cool you with perspiration
• Parasympathetic: conserves energy as it calms you
• Decreasing your heartbeat, lowering your blood sugar, etc.
• Work together to keep us in a steady internal state
Central Nervous System
• Neural networks
• neurons cluster into work groups
• So they can have fast, short connections
• Reflexes
• Simple, automatic response to a sensory
stimulus, such as the knee-jerk response
• Pain reflex – hand will jerk from a flame before
your brain receives and responds to the
information that causes you to feel pain
Endocrine System
• The body’s “slow”
chemical
communication
system; a set of glands
that secrete hormones
into the bloodstream
• Hormones
• Travel through the
bloodstream and affect
other tissues, including
the brain
• Influence our interest in
sex, food, and
aggression
Influential Glands
• Adrenal Glands:
• Epinephrine (adrenaline)
• Norepinephrine (noradrenaline)
• Increase heart rate, blood pressure, blood sugar – create a
surge of excitement that can linger a while
• Pituitary Gland:
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•
•
•
•
Most influential gland
Pea-sized structure located in the core of the brain
Controlled by an adjacent brain area (hypothalamus)
Releases hormones that influence growth
Also influence the release of hormones by other endocrine
glands
The Brain
• When we’re thinking about our brain,
we’re thinking with our brain
• The mind is what the brain does
Older Brain Structures
• Brainstem
• The brain’s basement
• Oldest and innermost region
• Medulla
• Where the spinal cord enters
the skull and swells slightly
• Controls your heartbeat and
breathing
• Pons
• Just above the medulla
• Helps coordinate movements
More older brain structures…
• Thalamus
• A joined pair of egg-shaped structures
• Receives information from all the senses except smell and routes it
to the brain regions that deal with seeing, hearing, tasting, and
touching
• Receives some of the higher brain’s replies, which it then directs to
the medulla and to the cerebellum
• Reticular Formation
• Inside the brainstem, between your ears
• Finger shaped network of neurons that extends from the spinal
cord right up to the thalamus
• Filters incoming stimuli and relays important information to other
areas of the brain
• Is involved in arousal
Older brain structures
• Cerebellum
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•
•
Means “little brain”
Extends from the rear of the brainstem
Base-ball sized
Enables one type of nonverbal learning
and memory
• Helps us judge time, modulate our
emotions, and discriminate sounds and
textures
• Coordinates voluntary movement
• Note: the older brain functions all
occur without any conscious effort
• Our brain processes most
information outside of our
awareness
Limbic System
• Doughnut-shaped
• Links to emotions (fear and anger)
and to basic motives (food and
sex)
• Amygdala
• Two lima bean-sized neural
clusters
• Influence aggression and fear
• Removed in an ill-tempered
monkey
• Turned very mellow
• Stimulated in a domestic cat
• Hissing, prepares to attack
• Moved a bit – cowers from a
mouse
• Hypothalamus
• Hypo = below (the thalamus)
• Some parts influence hunger,
thirst, body temperature, sexual
behavior
• Reward centers
• Reward deficiency syndrome
Cerebral Cortex
• Thin surface layer of interconnected
neural cells
• Your body’s ultimate control and
information-processing center
• Contains 20-23 billion nerve cells
• 300 trillion synaptic connections
“being human takes a lot of nerve”
Functions of the Cortex
• Motor Functions
• Motor cortex – runs from ear-to-ear across the top
of the head
• Stimulating parts of the brain in the left or right
hemisphere caused movements of specific body
parts on the opposite side of the body
• Areas of the body requiring precise control
(fingers, mouth) occupy the greatest amount of
cortical space
Functions of the Cortex
• Sensory Functions
• Parallel to the motor cortex & just behind
the front of the parietal lobes
• Specializes in receiving information from
the skin senses and from the movement of
body parts
Association Areas
• Three-fourths of the think wrinkled
layer of the cerebral cortex
• Neurons in this area integrate
information, linking sensory inputs with
stored memories
• Association areas are found in all four
lobes
Association Areas
• More intelligent animals have increased
“uncommitted” or association areas of
the cortex
Language:
Specialization & Integration
• Aphasia
• Impaired use of language
• Some people with this can speak fluently but cannot read
• Some can write but not read, read but not write, read
numbers but not letters
• Broca’s Area
• A specific area of the left frontal lobe, where if damage
occurs, muscle movements involved in speech are impacted
• Struggle to form words, yet could often sing familiar songs
with ease
• Wenicke’s Area
• A specific area of the left temporal lob, where if damage
occurs, people could only speak meaningless words and
were unable to comprehend others’ words
The Brain’s Plasticity
• Plasticity – its ability to modify itself after some types
of damage
• Some neural tissue can reorganize in response to
damage
• Most plastic when we are young children
• If a blind person uses one finger to read Braille, the
brain area dedicated to that finger expands as the
sense of touch invades the visual cortex that
normally helps people see
• Lose a finger and the sensory cortex that received its
input will begin to receive input from the adjacent
fingers, which then become more sensitive
• Adult mice and humans can also generate new brain
cells
Splitting the Brain
• The brain’s two sides serve differing functions
• Lateralization – hemispheric specialization
• Corpus callosum – wide band of axon fibers connecting
the two hemispheres and carrying messages between
them
• Split brained people are surprisingly normal – their
personality and intellect hardly affected
Left Hemisphere
Right Hemisphere
Information
from the right
visual field
comes here
Information from
the left visual field
comes here
Speech is controlled
here – they will say
what they saw in the
right visual field
Controls the left
hand – will point to
the word that they
saw in their left
visual field
Hemispheric Differences
• Right Hemisphere
• Perceptual tasks performed will cause brain waves, blood
flow, and glucose consumption to increase, which shows
activity in the right hemisphere
• Excels in making inferences based on language
• Left Hemisphere
• Speaking or calculating – will increase activity in the left
hemisphere
• Adept to making quick, literal interpretations of language
• Deaf people are enabled to process sign language here
• Just as hearing people use the left hemisphere to process
speech, deaf people use the left hemisphere to read signs
• To the brain, language is language, whether it is spoken or signed
Which way is she spinning?
• If you see her
spinning to the
right, then your
right brain is
working and if you
see her spinning to
the left, then your
left brain is
working
Just for fun…