 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 of neural communication grew in the 1900s.

Types of Neurons SensoryMotor Interneurons

 Information collectors  Receive inputs from neighboring neurons  Inputs may number in thousands  If enough inputs the cell’s AXON may generate an output

 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

 Round, centrally located structure  Contains DNA  Controls protein manufacturing  Directs metabolism  No role in neural signaling zContains the cell’s Nucleus

 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

 The cell’s output structure  One axon per cell, 2 distinct parts  tubelike structure branches at end that connect to dendrites of other cells

 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

Cell body end of axon Direction of neural impulse: toward axon terminals

 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

 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

 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

 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

 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

Cell Membrane in resting state K+ Na+ Cl- K+ A- Outside of Cell Inside of Cell Na + Cl-

Action potential

 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 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 Agonists: fit receptor well and act like the NT e.g., nicotine e.g., nicotine

Serotonin Pathways Dopamine Pathways

 Excitatory message— increases the likelihood that the postsynaptic neuron will activate  Inhibitory message— decreases the likelihood that the postsynaptic neuron will activate.

Types of Neurons SensoryMotor Interneurons

Spinal Cord Brain Sensory Neuron  INPUT From sensory organs to the brain and spinal cord Drawing shows a somatic neuron Also called AFFERENT NEURONS

Spinal Cord Brain Sensory Neuron Motor Neuron  OUTPUT From the brain and spinal cord, to the muscles and glands Also called EFFERENT NEURONS

Spinal Cord Brain Sensory Neuron Motor Neuron  Interneurons carry information between other neurons only found in the brain and spinal cord

Central (brain and spinal cord) Nervous system Autonomic (controls self-regulated action of internal organs and glands) Skeletal (controls voluntary movements of skeletal muscles) Sympathetic (arousing) Parasympathetic (calming) Peripheral