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Neural Communication Biological Psychology
branch of psychology concerned with the links between biology and behavior
some biological psychologists call themselves behavioral neuroscientists, neuropsychologists, behavior geneticists, physiological psychologists, or biopsychologists
Phrenology (Franz Gall) Study of the bumps on your head Bumps reveal a person’s abilities and
traits
Phrenology
Popular in the 1800s, debunked after knowledge ofneural communication grew in the 1900s.
Neurons and Synapses
Types of Neurons
Sensory Motor Interneurons
Neural Communication
Dendrites Information
collectors Receive inputs from
neighboring neurons Inputs may number
in thousands If enough inputs the
cell’s AXON may generate an output
Dendritic Growth Mature neurons
generally can’t divide
But new dendrites can grow
Provides room for more connections to other neurons
New connections are basis for learning
The cell body
Round, centrally located structure
Contains DNA Controls protein
manufacturing Directs metabolism No role in neural
signaling
Contains the cell’s Nucleus
Myelin sheath
White fatty casing on axon
Acts as an electrical insulator
Not present on all cells
When present increases the speed of neural signals down the axon.
Myelin Sheath
Axon
The cell’s output structure
One axon per cell, 2 distinct parts tubelike structure
branches at end that connect to dendrites of other cells
Neural Communication
Action Potential a neural impulse; a brief electrical
charge that travels down an axon generated by the movement of
positively charged atoms in and out of channels in the axon’s membrane
Threshold the level of stimulation required to
trigger a neural impulse
Neural Communication
Cell body end of axon
Direction of neural impulse: toward axon terminals
How Neurons Communicate
Neurons communicate by means of an electrical signal called the Action Potential
Action Potentials are based on movements of ions between the outside and inside of the cell
When an Action Potential occurs, a molecular message is sent to neighboring neurons
Resting Potential
At rest, the inside of the cell is at -70 microvolts With inputs to dendrites inside becomes more positive If resting potential rises above threshold, an action
potential starts to travel from cell body down the axon Figure shows resting axon being approached by an AP
Depolarization Ahead of AP
AP opens cell membrane to allow sodium (Na+) in Inside of cell rapidly becomes more positive than outside This depolarization travels down the axon as leading edge
of the AP
Repolarization follows
After depolarization potassium (K+) moves out restoring the inside to a negative voltage
This is called repolarization The rapid depolarization and repolarization produce a
pattern called a spike discharge
Finally, Hyperpolarization
Repolarization leads to a voltage below the resting potential, called hyperpolarization
Now neuron cannot produce a new action potential
This is the refractory period
REFRACTORY PERIOD
Ion concentrations
Cell Membrane in resting state
K+
Na+ Cl-K+A-
Outside of Cell
Inside of Cell
Na+ Cl-
The Cell Membrane is Semi-Permeable
Cell Membrane at rest
Na+ Cl-K+
Na+
Cl-K+
A-
Outside of Cell
Inside of Cell
Potassium (K+) can pass through to equalize its concentration
Sodium and Chlorine cannot pass through
Result - inside is negative relative to outside
- 70 mv
Action potential
Neural Communication
Synapse [SIN-aps] junction between the axon tip of the sending
neuron and the dendrite or cell body of the receiving neuron
tiny gap at this junction is called the synaptic gap or cleft
Neurotransmitters chemical messengers that traverse the
synaptic gaps between neurons when released by the sending neuron, neuro-
transmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether it will generate a neural impulse
Some Drugs Work on Receptors
Some drugs are shaped like neurotransmitters
Antagonists: fit the receptor but poorly and block the NT e.g., beta blockers
Agonists: fit receptor well and act like the NT
e.g., nicotine
Neural Communication
Serotonin Pathways Dopamine Pathways
Excitatory and Inhibitory Messages
of neurotransmitters Excitatory message— increases
the likelihood that the postsynaptic neuron will activate
Inhibitory message— decreases the likelihood that the postsynaptic neuron will activate.
Neurons and Synapses
Types of Neurons
Sensory Motor Interneurons
SpinalCord
BrainSensoryNeuron
Sensory Neurons
INPUT From sensory organs to the brain and spinal cord
Drawing shows a somatic neuron
Also called AFFERENT NEURONS
SpinalCord
BrainSensoryNeuron
MotorNeuron
Motor Neurons
OUTPUT From the brain and spinal cord, to the muscles and glands
Also called
EFFERENT NEURONS
SpinalCord
BrainSensoryNeuron
MotorNeuron
Interneurons
Interneurons carry information between other neurons only found in the brain and spinal cord
The Nervous System
Central(brain and
spinal cord)
Nervoussystem
Autonomic (controlsself-regulated action of
internal organs and glands)
Skeletal (controlsvoluntary movements of
skeletal muscles)
Sympathetic (arousing)
Parasympathetic (calming)
Peripheral