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