Download The Neural Control of Behavior

The Neural Control of
Behavior
Chapter 5
Neurons
The Basic Unit of the Mind
 NEURONS: single cells in the
nervous system that are
specialized for carrying
information rapidly from
one place to another
and/or integrating
information from various
sources
 The human brain contains
~100 billion neurons and
~100 trillion synapses
The Human
Nervous System
•CENTRAL NERVOUS SYSTEM:
comprised of the brain and spinal
chord
•PERIPHERAL NERVOUS SYSTEM: the
entire set of cranial and spinal nerves
that connect the central nervous
system (brain and spinal chord) to
the body’s sensory organs, muscles,
and glands.
•NERVE: a large bundle containing
the axons of many neurons. Located
in the PNS, nerves connect the CNS
with muscles, glands and sensory
organs
Varieties of Neurons
SENSORY NEURONS: carry
messages from a sensory
organ (e.g. eyes, ears,
nose, tongue and skin),
through a nerve, into the
brain and spinal chord.
MOTOR NEURONS: carry
messages from the brain or
spinal chord, through a
nerve, to a muscle or
gland
INTERNEURONS: exist
entirely within the brain or
spinal chord and carries
messages from one set of
neurons to another
Neuronal Structures
 SOMA: or cell body, contains
the nucleus and other cellular
machinery
 DENDRITES: thin, tube-like
extensions that branch out of
the soma and are specialized
for receiving signals from other
neurons
 AXON: thin, tube-like extension
from a neuron that is
specialized to carry neural
impulses to other cells
Neuronal Structures
 AXON TERMINAL : a swelling at
the end of the axon that is
designed to release a
chemical substance onto
another neuron, muscle or
gland cell
 MYELIN SHEATH: a casing of
fatty cells wrapped tightly
around the axons of some
neurons
Action Potentials
ACTION POTENTIAL:
neural impulses; the allor-nothing electrical
bursts that begin at one
end of the axon of a
neuron and move
along the axon to the
other end
The Neuronal Membrane
CELL MEMBRANE: thin, porous outer covering of a neuron
or other cell that separates the cell’s intracellular fluid
from extracellular fluid
The Resting Potential
•The constant
electrical charge
that exists across
the membrane of
an inactive neuron
-70 millivolts
•A- and K+ inside
•Na+ and Cloutside
Depolarization and
Repolarization
DEPOLARIZATION
1.
Action potential causes channels
in the membrane to open
2.
Na+ rush into the cell, making it
more positive
3.
Once it’s more positive inside than
outside the cell, the channel closes
REPOLARIZATION
1.
Channels that permit K+ to pass
through remain open
2.
K+ is pushed out of the cell, which
reestablishes the original, resting
state of the neuron
SODIUM-POTASSIUM PUMP
Action Potential Regeneration
The action potential
regenerates itself
along the axon,
traveling down to the
axon terminals.
Saltatory Conduction
Nodes of Ranvier
The impulses
skip from node
to node, thereby
increasing the
speed of the
impulse.
Synaptic
Transmission
Excitatory and Inhibitory Synapses
• Synapse at which the neurotransmitter increases the
likelihood that an action potential will occur
• NT  open Na+ channel  depolarization
• E.g. glutamate
• Synapse at which the neurotransmitter decreases the
likelihood that an action potential will occur
• NT  open Cl- or K+ channel  hyperpolarization
• E.g. GABA (gamma-aminobutyric acid)
How Drugs Alter Synaptic Transmission
1.
Act on the presynaptic
neuron and either promote
or inhibit neurotransmitter
release
2.
Act within the synapse to
either promote or inhibit the
process that terminates the
action of the
neurotransmitter
3.
Act on postsynaptic
receptors, either producing
the same effect as the
neurotransmitter or blocking
the neurotransmitter from
producing its normal effect
The Brain
Subcortical Structures: The Brain
Stem and Thalamus
Thalamus
Cerebellum
Midbrain
Pons
Medulla
Spinal chord
The Cerebral Cortex
Frontal
lobe
Parietal
lobe
Occipital
lobe
Temporal
lobe
Somatosensory and Motor
Cortex Maps
Asymmetry of the Cerebral Cortex
 Our hemispheres behave
contralaterally
 Left hemisphere is
specialized for language
 Right hemisphere is
specialized for nonverbal,
visuospatial abilities