Biological Bases of Behavior: Neural Processing and the Endocrine System

Everything Psychological is Simultaneously Biological


- Invented by Franz Gall

- An ill-fated theory claiming bumps on the skull revealed our mental abilities and character traits

- However, it did focus on the idea that various brain regions have particular functions

Neural Communication

- BIOLOGICAL PSYCHOLOGISTS study the links between biology and behavior to increase our understanding of consciousness, depression, hunger and sex, stress and disease

- Body's neural information system built from the basic building cells NEURONS - nerve cells

     *Parts of the Neuron

          ~ DENDRITE - bushy, branching extensions of a neuron that receives messages and conducts impulses toward the cell body

          ~ AXON - extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands

          ~ MYELIN SHEATH - a layer of fatty tissue segmentally encasing the fibers of many neurons that helps speed neural impulses

     *Types of Neurons

          ~ SENSORY NEURONS - neurons that carry incoming information from the sensory receptors to the brain and spinal cord

          ~ MOTOR NEURONS - neurons that carry outgoing information from the brain and spinal cord to the muscles and glands

          ~ INTERNEURONS - neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs

- Neurons transmit messages by firing an impulse called the ACTION POTENTIAL - a brief electrical charge that travels down the axon

     *To fire an impulse...

          ~ starts at a RESTING POTENTIAL state where it's a positive-outside/negative-inside sodium ion charge state

          ~ Positively charged sodium ions flood through the membrane to DEPOLARIZE each section of the axon

          ~ Neurons pumps the positively charged sodium ions back outside during the REFRACTORY PERIOD

          ~ Signals must exceed a minimum THRESHOLD, or intensity, to trigger the action potential

- Neurons meet at a point called the SYNAPSE, which is the junction between the axon tip of the sending neuron and the dendrite or the cell body of the receiving neuron

- The axon terminal of one neuron is separated from the receiving neuron by a SYNAPTIC GAP or SYNAPTIC CLEFT

- When an action potential reaches the terminals at an axon's end, it triggers the release of chemical messengers called NEUROTRANSMITTERS - influences whether or not a neuron will generate a neural impulse

- Neurotransmitters cross the synaptic gap and bind to the receptors of the receiving neuron like a key fits in a lock

- The sending neuron then reabsorbs any excess neurotransmitters in a process called REUPTAKE

- Neurotransmitters influence our motions and our emotions, as shown in the image above

- Different neurotransmitters have different effects

- Researchers found that the brain produces its own naturally occurring opiates

- These ENDORPHINS - natural, opiate-like neurotransmitters linked to pain control and to pleasure - affect our bodies in the same way neurotransmitters do and explain feelings such as the "runner's high"

- Drugs and other chemicals can alter neurotransmission

- The brain stops producing its own natural opiates if its flooded with opiate drugs, and if the drug is withdrawn, the brain is then deprived of any form of opiate, causing intense discomfort

- Drugs and other chemicals affect brain chemistry at synapses, often by either amplifying or blocking a neurotransmitter's activity

     *Agonist = molecule may be similar enough to a neurotransmitter to bind to its receptor and mimic its effects

     *Antagonist = binds to receptors but their effect is instead to block a neurotransmitter's functioning

The Nervous System

- Our NERVOUS SYSTEM - consists of all the nerve cells of the peripheral and central nervous systems - takes in information from the world and the body's tissues, to make decisions, and to send back information and orders to the body's tissues

     *PERIPHERAL NERVOUS SYSTEM - sensory and motor neurons that connect the central nervous system to the rest of the body

          ~ information travels through axons that are bundled into electrical cables known as nerves

          ~ consists of SOMATIC NERVOUS SYSTEM - division that controls the body's skeletal muscles - and AUTONOMIC NERVOUS SYSTEM - division that controls the glands and the muscles of the internal organs

               : Autonomic nervous system serves two important, basic functions

               : SYMPATHETIC NERVOUS SYSTEM - division that arouses the body, mobilizing its energy in stressful situations

               : PARASYMPATHETIC NERVOUS SYSTEM - division that calms the body, conserving its energy

     *CENTRAL NERVOUS SYSTEM - brain and spinal cord

          ~ the spinal cord is an information highway connecting the peripheral nervous system to the brain

          ~ these neural pathways govern our REFLEXES - our automatic responses to stimuli

          ~ information travels to and from the brain by way of the spinal cord

The Endocrine System

- The ENDOCRINE SYSTEM is the body's slow chemical communication system: a set of glands that secrete hormones into the bloodstream

- It secretes forms of chemical messengers called HORMONES which travel in the bloodstream

- A slow but steady system that outlasts the effects of neural messages

- The ADRENAL GLANDS secrete epinephrine and norepinephrine that help arouse the body in times of stress

- The PITUITARY GLAND - most influential gland - regulates growth and controls other endocrine systems under the control of the hypothalamus

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