Transcript Chapter 2: Brain and Behavior

Chapter 2: Brain
and Behavior
Neuron and Its Parts
• Neuron: Individual nerve cell; 100
billion in brain
– Dendrites: Receive messages from
other neurons
– Soma: Cell body; body of the neuron
– Axon: Carries information away from
the cell body
– Axon Terminals: Branches that link
the dendrites and soma of other
Figure 2.1
Main Parts of the Neuron
Figure 2.2
The Nerve Impulse
• Resting Potential: Electrical charge
of an inactive neuron
• Threshold: Trigger point for a
neuron’s firing
• Action Potential: Nerve impulse
More on Nerves
• Ion Channels: Tiny holes through
the axon membrane
• Negative After-Potential: When a
neuron is less willing to fire
• Synapse: Microscopic space
between two neurons over which
messages pass
Figure 2.3
Figure 2.4
Neuron and Neural
Impulse
Windows
Mac OS 8-9
Mac OS X
Neurotransmitters
• Chemicals that alter activity in
neurons; brain chemicals
– Acetylcholine: Activates muscles
– Dopamine: Muscle control
– Serotonin: Mood and appetite control
• Receptor Site: Areas on the surface
of neurons and other cells that are
sensitive to neurotransmitters or
Normal Synaptic
Transmission of Dopamine
Synaptic Transmission
Windows
Mac OS 8-9
Mac OS X
Figure 2.6
Neural Regulators
• Neuropeptides: Brain chemicals
that regulate activity of other
neurons
– Enkephalins: Relieve pain and stress;
similar to endorphins
– Endorphins: Released by pituitary
gland; also help to relieve pain
• Placebos raise endorphin levels
Interaction of Endorphins &
Opiates
Nerves and Neurons
• Nerves: Large bundles of axons
and dendrites
• Myelin: Fatty layer of tissue that
coats axons
– Multiple Sclerosis (MS) occurs when
myelin layer is destroyed; numbness,
weakness, and paralysis occur
Nerves and Neurons (cont.)
• Neurilemma: Thin layer of cells
wrapped around axons outside
brain and spinal cord; forms a
tunnel that damaged fibers can
follow as they repair themselves
• Neurogenesis: Production of new
brain cells; brain loses thousands
of cells each day and grows new
Neural Networks
• Central Nervous System (CNS):
Brain and spinal cord
• Peripheral Nervous System: All
parts of the nervous system
outside of the brain and spinal cord
Two Divisions of the
Peripheral
Nervous
System
• Somatic System: Links spinal cord
with body and sense organs;
controls voluntary behavior
• Autonomic System: Serves internal
organs and glands; controls
automatic functions such as heart
rate and blood pressure
Two Divisions of the
Autonomic Nervous
• Sympathetic:System
Arouses body;
emergency system
• Parasympathetic: Quiets body;
most active after an emotional
event
Figure 2.7
Figure 2.8
Figure 2.9
The Spinal Cord
• Spinal Nerves: 31 of them; carry
sensory and motor messages to
and from the spinal cord
• Cranial Nerves: 12 pairs that leave
the brain directly without passing
through the spinal cord; also work
to communicate messages
The Spinal Cord and
Behavior
• Reflex Arc: Simplest behavior in
which a stimulus provokes an
automatic response
• Sensory Neuron: Nerve cell that
carries messages from the senses
toward the CNS
• Motor Neuron: Cell that carries
commands from the CNS to the
Researching the Brain
• Ablation: Surgical removal of
tissue
• Deep Lesioning: A thin wire
electrode is lowered into a
specific area inside the brain;
Electrical current is then used to
destroy a small amount of brain
tissue
Figure 2.10
Brain Imaging Techniques
• Computed Tomographic Scanning
(CT): Computer-enhanced X-ray of
the brain or body
• Magnetic Resonance Imaging
(MRI): Uses a strong magnetic field,
not an X-ray, to produce an image
of the brain and body
More Brain Imaging
Techniques
• Functional MRI (fMRI): MRI that
makes brain activity visible
• Positron Emission Tomography
(PET): Computer-generated color
image of brain activity, based on
glucose consumption in the brain
Figure 2.11
Figure 2.16
Cerebral Cortex
• Outer layer of the cerebrum
• Cerebrum: Two large
hemispheres that cover upper
part of the brain
• Corticalization: Increase in size
and wrinkling of the cortex
• Cerebral Hemispheres: Right and
left halves of the cerebrum
Split Brains
• Corpus Callosum: Bundle of fibers
connecting cerebral hemispheres
• In Split Brains, Corpus Callosum is
cut; done to control severe epilepsy
(seizure disorder)
• Result: The person now has two
brains in one body
• This operation is rare and is often
Figure 2.21
The Corpus Callosum
Figure 2.18
Right Brain/Left Brain
• Humans use 95 percent of our left
brain for language
The Left Hemisphere
• Left hemisphere is better at math,
judging time and rhythm, and
coordinating order of complex
movements
– Processes information sequentially
The Right Hemisphere
• Right hemisphere is good at
perceptual skills, and at expressing
and detecting other’s emotions
– Processes information simultaneously
Figure 2.20
Figure 2.30
Central Cortex Lobes
• Areas bordered by major grooves
or fissures or defined by their
functions
• Occipital Lobe: Back of brain; vision
center
• Parietal Lobe: Just above occipital;
bodily sensations such as touch,
pain, and temperature
The Occipital Lobe
The Parietal Lobe
The Last Two Lobes
• Temporal Lobe: Each side of the
brain; auditory and language
centers
• Frontal Lobe: Movement, sense of
smell, higher mental functions
– Contains motor cortex; controls motor
movement
Figure 2.23
The Temporal Lobe
The Frontal Lobe
Figure 2.24
When the Brain Fails to
Function Properly
• Association Cortex: All areas of the
cerebral cortex that are not
primarily sensory or motor in
function
• Aphasia: Speech disturbance
resulting from brain damage
Broca’s Area
• Language area related to grammar
and pronunciation
– If damaged, person knows what s/he
wants to say but can’t say the words
Wernicke’s Area
• Wernicke’s Area: Related to
language comprehension; in left
temporal lobe
– If damaged, person has problems
with meanings of words, NOT
pronunciation
Figure 2.28
Subcortex
• All brain structures below cerebral
cortex; immediately below cerebral
hemispheres
• Hindbrain (Brainstem)
• Medulla: Connects brain with the
spinal cord and controls vital life
functions such as heart rate and
breathing
More Subcortex Structures
• Pons (Bridge): Acts as a bridge
between brainstem and other
structures; influences sleep and
arousal
• Cerebellum: Located at base of
brain; regulates posture, muscle
tone, and muscular coordination
The Brainstem
Subcortex: Reticular
Formation (RF)
• Reticular Formation: Inside medulla
and brainstem
– Associated with alertness, attention,
and some reflexes (breathing,
coughing, sneezing, vomiting)
• Reticular Activating System (RAS):
Part of RF that activates cerebral
cortex
– Its alarm clock
Forebrain
• Structures are part of Limbic
System: System within forebrain
closely linked to emotional
response and motivating behavior
• Thalamus: Relays sensory
information on to the cortex;
switchboard
• Hypothalamus: Regulates
More Forebrain Structures
• Amygdala: Associated with fear
responses
• Hippocampus: Associated with
storing permanent memories; helps
us navigate through space
The Limbic System
Figure 2.27
Figure 2.26
Endocrine System
• Glands that pour chemicals
(hormones) directly into the
bloodstream or lymph system
• Pituitary Gland: Regulates growth
via growth hormone
Pituitary Problems
• Too little means person will be
smaller than average
– Hypopituitary Dwarfs: As adults,
perfectly proportioned but tiny
– Treatable by using growth hormone;
will add a few inches
– Treatment is long and expensive
Endocrine System (cont.)
• Too much growth hormone leads to
giantism (excessive body growth)
• Acromegaly: Enlargement of arms,
hands, feet, and facial bones; due
to too much growth hormone
released late in growth period
– Andre the Giant
• Pituitary also governs functioning of
Figure 2.29
The Pineal Gland
• Regulates body rhythms and sleep
cycles
– Releases hormone melatonin, which
responds to daily variations in light
The Thyroid Gland
• Thyroid: In neck; regulates
metabolism
– Hyperthyroidism: Overactive thyroid;
person tends to be thin, tense,
excitable, nervous
– Hypothyroidism: Underactive thyroid;
person tends to be inactive, sleepy,
slow, obese
The Adrenal Glands
• Adrenals: Arouse body, regulate
salt balance, adjust body to stress,
regulate sexual functioning; located
on top of kidneys
– Releases epinephrine and
norepinephrine (also known as
adrenaline and noradrenalin)
The Adrenal Glands (cont.)
• Adrenal Medulla: Source of
epinephrine and norepinephrine
• Adrenal Cortex: Produces
hormones known as corticoids
– Regulate salt balance
– Deficiency in some types will cause
powerful salt cravings in humans
Adrenal Hormones
• Epinephrine arouses body; is
associated with fear
• Norepinephrine arouses body; is
linked with anger
Adrenal Problems
• Oversecretion of adrenal sex
hormones can cause virilism:
exaggerated male characteristics
(Bearded woman)
– May also cause premature puberty if
occurs early in life
Figure 2.31
Handedness
• Preference for right or left hand in
most activities
• Dominant Hemisphere: Term
usually applied to the side of the
human brain that produces
language
• Lateralization: Specialization in
abilities of brain hemispheres