Transcript Neuroscience

Chapter 2
Neuroscience and Behavior
The Neuron
Communication in the
Nervous System takes
place in the neurons
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Cells that are specialized to
receive and transmit info
(nerve cell)
Neuroscience: the study of
the Nervous System
Glial Cells: support cells
that provide structural
support, nutrition, and
discard waste for neurons.
Also produce myelin.
Types of neurons
Sensory Neurons: transmit info from
receptor cells in sensory organs (i.e. nose,
ears, tongue, eyes, and skin) and internal
organs to brain.
Motor Neurons: Transmit info from the
brain to muscles.
Interneurons: Communicate between
sensory and motor neurons.
Structures of the Neuron
Cell Body: contains
structures that
provide energy for the
cell to function. Also
contains the nucleus.
Dendrites: Receive
messages from other
neurons
Structures of the Neuron con’t
Axon: Carries info to
other neurons.
Myelin Sheath:
Protects axon from
axons of other
neurons. Formed by
glial cells
Structures of the Neuron con’t
Axons vary in size.
Axons may have branches that allow it to
communicate with more than one neuron.
Gaps in the Myelin Sheath called Nodes of
Ranvier or just nodes
Neurons with Myelin Sheath communicate
faster
Multiple Sclerosis is the degeneration of
the Myelin Sheath.
Communication Within the Neuron
Messages are gathered by the Dendrites and
passed along the Axon by a small electrical
impulse called Action Potential.
Stimulus Threshold: The minimum level of
Stimulation required for a neuron to activate.
While waiting, a neuron is polarized. Interior is
more negatively charged than exterior.
Resting charge is -70 millivolts, referred to as
resting potential.
Action Potential is All-or-None
Communication Within the Neuron
con’t
While resting, a neuron has sodium ions on the
exterior of the membrane. In the interior, the
neuron contains potassium ions.
When the action potential is sent down the axon,
channels open and the two ions briefly switch,
creating a charge of +30 millivolts. This is
depolarization.
Refractory Period: Period the neuron is unable
to fire. During this period the neuron repolarizes.
Communication Between Neurons
Primary function of a neuron is to communicate
information to other cells.
2 Types of Communication: Electrical and
Chemical
Synapse: Point of communication between two
neurons.
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Presynaptic neuron: Neuron sending the message
Postsynaptic neuron: Neuron receiving the message
Synaptic Gap: Fluid filled space separating neurons.
Axon Terminal: Located at the end of the axon.
Where the message is sent from one neuron to the
next.
Electrical Communication
Synapse extremely
narrow
Ion Channels serve
as a bridge between
neurons
Communication is
instananeous
Chemical Communication: Synaptic
Transmission
When message reaches the axon terminal,
synaptic vesicles dock with membrane and
release chemical messengers called
neurotransmitters.
Neurotransmitters cross the synaptic gap and
attach to receptor sites on the dendrites of
postsynaptic neurons.
Neurotransmitters must fit receptor sites exactly.
Reuptake: Process of neurotransmitters being
reabsorbed by presynaptic neuron. Those not
reabsorbed are dissolved by enzymes.
Synaptic
Transmission
Types of messages
Neurotransmitter gives one of two
messages. Message depends on the
receptor it attaches to.
Excitatory message: increases the
likelihood that the postsynaptic neuron will
activate action potential.
Inhibitory message: decreases the
likelihood that the postsynaptic neuron will
activate action potential.
Neurotransmitters and their effects
Acetylcholine
1st neurotransmitter discovered
Found in all motor neurons; stimulates
muscles to contract
Also found in brain; essential to memory,
learning, and general intellectual
functioning.
Alzheimer’s Disease linked to a depletion
of Acetylcholine
Dopamine
Involved in movement, attention, learning, and
pleasurable or rewarding sensations.
Addictiveness of some drugs related to
dopamine increasing properties. (i.e. cocaine,
nicotine)
Degeneration in brain linked to Parkinson’s
Disease. Symptoms include rigidity, muscles
tremors, poor balance.
Excessive levels linked to hallucinations and
Schizophrenia.
The Brain: Studying the brain
Case Studies: Monitoring behavior of people
with damage or disease. Limited
Lesions: Removing or damaging a part of the
brain.
Bipolar electrodes: Surgically implanted wires or
disks that stimulate areas of the brain
Electroencephalogram: Records the electrical
activity of the brain from millisecond to
millisecond. Recorded on an EEG.
Brain Structures: Brainstem
Brainstem: Includes the hindbrain and mid brain.
Hindbrain connects the Spinal Cord with the rest
of the brain
Made up of 3 structures:
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Medulla: Controls breathing, heart rate, etc
Pons: Relays info from forebrain to cerebellum
Cerebellum: Controls balance & coordination
Reticular Formation: Group of neurons in medulla that
project up the brain and down Spinal Cord.
Brain Structures: Brainstem con’t
Midbrain: Processes auditory and visual
information.
Substantia Nigra: Involved in motor control
and contains a large concentration of
dopamine-producing neurons.
Brain Stem
Brain Structures: Forebrain
Also called cerebrum; makes up 90% of
brain.
Outer portion called Cerebral Cortex.
Divided into 2 cerebral hemispheres that
are connected by the corpus callosum.
Each Hemisphere has 4 Lobes: Temporal,
Occipital, Parietal, and Frontal.
Brain Structures: Forebrain con’t
Temporal Lobe: Primary Auditory Cortex
Occipital Lobe: Primary Visual Cortex
Parietal Lobe: Somatosensory Cortexprocesses bodily info (i.e. touch, temp.
pressure)
Frontal Lobe: Involved in planning,
initiating, and executing voluntary
movements.
Forebrain
The Brain: The Limbic System
Form complex neural circuits that play
critical roles in learning, memory and
emotional control.
4 Key Structures:
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Hippocampus
Thalamus
Hypothalamus
Amygdala
The Brain: The Limbic System con’t
Hippocampus: Involved in forming new
memories. Neurogenesis takes place.
Thalamus: Processes and distributes sensory
and motor info to and from cerebral cortex.
Regulates awareness, attention, and motivation
Hypothalamus: Regulates both divisions of the
Autonomic Nervous System.
Amygdala: involved in a variety of emotional
responses: fear, anger, and disgust.
Limbic
System
Human
Brain
Specialization of the Hemispheres
Cerebral hemispheres work together but
have different responsibilities.
Lateralization of Function: The idea that
different hemispheres exert more control
over the other in specific functions.
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Cortical Localization: The idea that particular
areas of the brain are associated with
particular functions
Specialization of the Hemispheres
con’t
Broca’s Area: Lower left frontal loberesponsible for speech.
Wernicke’s Area: Left Temporal Loberesponsible for language comprehension
Aphasia- Partial or complete inability to
articulate ideas or understand spoken or
written language as a result of brain
damage.
Cutting the Corpus Callosum
Done to reduce severity of or eliminate epileptic
seizures.
Roger Sperry’s experiment shows that the
procedure eliminates communication between to
hemispheres. (P.74)
Left Hemisphere superior in language abilities,
speech, reading, and writing.
Right Hemisphere dominate in nonverbal
emotional expression and visual-spacial tasks.
Creative.
Plasticity
Functional Plasticity: Brain’s ability to shift
functions from damaged areas of the brain
to undamaged areas.
Structural Plasticity: Idea that the brain’s
structure is sculpted by experience.
Brain Lobes
Forebrain
Brain Stem
Limbic System
Human Brain