Biological Basis of Behavior

• Serotonin pathways are key neural networks in the brain
• Dopamine pathways are also key neural networks in the brain

Mind and Body

• For most of human history, it was thought that mind and body are separate
• This is known as mind-body dualism
• Psychological experience is actually tied to our physical being
• Materialism supports that psychological experience is completely tied to our physical being

Biological Understanding of Behavior

• Biological and biochemical processes underlie all human behavior and thought
• Biology does not solely control behavior
• Environmental forces, actions, and choices modify the brain
• Physical and chemical changes also occur in the brain when we learn, remember, feel, or act

Biological Understanding of Behavior and Mental Processes

• Enriched environments lead to rats developing more connections between neurons, contrasted to boring environments
• Rats deprived of touch in infancy grow less and have fewer neuron connections, also exhibiting higher stress hormone levels
• Premature infants who are massaged experience faster growth and improved cognitive development compared to those who aren't touched

The Nervous System

• The nervous system supplies the physical basis for psychological experience
• It is the body's speedy, electrochemical communication system
• It directs and is influenced by both behavior and thought
• Can be divided into two major subsystems
• Central Nervous System (CNS): brain and spinal cord
• Peripheral Nervous System (PNS): all other nerve cells

Peripheral Nervous System

• Somatic Nervous System: controls the body’s skeletal muscles
• Autonomic Nervous System: part of the PNS that controls glands and other muscles

Autonomic Nervous System (ANS)

• Sympathetic Nervous System: division of the ANS that arouses the body and mobilizes energy when in stressful situations
• Parasympathetic Nervous System: division of the ANS that calms the body and conserves energy in order to maintain homeostasis

Neurons

• Neurons are the nervous system's functional unit
• They are cells that communicate and organize experiences
• The human brain contains ~100,000,000,000 neurons
• There may be ~10,000 times more connections between neurons than neurons
• They form complex networks

Main Jobs of Neurons

• Relay information
• Store information (memories and data)
• Move muscles and bones
• Regulate all internal processes
• Sense information from the external world (eyes, ears, nose, etc.)
• Release neurotransmitters such as dopamine and serotonin
• Work with the Endocrine System (hormones)

Kinds of Neurons

• Sensory Neurons transmit incoming information from sense receptors to the CNS
• Motor Neurons transmit outgoing information from the CNS to muscles and glands
• Interneurons connect the sensory and motor neurons

Glial Cells

• Glial cells are important helper cells
• Functions include: nourishing neurons, moving neurons, cleaning up debris, forming myelin, repairing neurons, attacking intruders
• They have a variety of functions from nourishing neurons to attacking intruders like viruses and bacteria
• There are 10 times more glia than neurons, making the brain mostly glia

The Neuron

• It is like other cells in the body
• Consists of a cell membrane
• Consists of a nucleus with organelles
• Consists of the same genetic material
• Has specialized structures for communication
• These structures include: axons, dendrites, terminal buttons, synaptic vesicles, receptors

Basic Parts of a Neuron

• Fires an "action potential:" a small electrical impulse
• Fires completely or not at all ("all or nothing" principle)

Axons

• Single fibers extending from the neuron
• Can be microscopic to over 2 feet long
• Serve as transmitter, carrying nerve impulses away from the cell
• Many are covered with myelin sheath, a fatty substance insulating it from other neurons which help nerve signals move faster

Axons (continued)

• The area at the end of the axon fiber is the terminal button
• The inside of the terminal button contains synaptic vesicles
• These vesicles contain chemicals called neurotransmitters

Nerves vs. Neurons

• Neurons are individual nerve cells
• Nerves are neural cables containing numerous axons
• Nerves are part of the peripheral nervous system
• Nerves connect muscles, glands, and sense organs to the central nervous system

Dendrites

• Are multiple, usually shorter fibers
• Dendrites “receive” signals from the axons of other neurons

Synapses

• Axons and Dendrites of adjacent cells never touch
• The synapse is the gap between them
• Chemicals called neurotransmitters are released across the synapse
• All communication between neurons is accomplished via neurotransmitters that migrate across the synaptic gap and bind with receptors on the dendrites of adjacent neurons

Connectome

• Connectome is a modern theory about how the structure and function of the brain may make a person who they are
• Understanding the Connectome is supposed to illustrate the complexity of the minds and brains
• Understanding the Connectome is supposed to illustrate how neurons communicate
• The Connectome is a good example of how science works from theory to testable hypothesis to experiment

Biological and biochemical processes underlie all human behavior and thought. Environmental forces, actions, and choices modify the brain. Physical and chemical changes also occur in the brain when we learn, remember, feel, or act. Psychological experience is actually tied to our physical being