Presentation on theme: "Psychology’s biological roots: neurons and neural communication."— Presentation transcript:
Psychology’s biological roots: neurons and neural communication
The neuron A cell that specializes in communication A neuron: a) receives information from other neurons, through its dendrites a) receives information from other neurons, through its dendrites b) integrates those signals, and b) integrates those signals, and c) sends messages to other neurons through its terminal buttons c) sends messages to other neurons through its terminal buttons
Neural structure Three main components 1) Cell Body – contains the nucleus collects info from other cells collects info from other cells cite of genetic activity cite of genetic activity 2) Axon - long, narrow outgrowth of a neuron 2) Axon - long, narrow outgrowth of a neuron transmits messages to other neurons transmits messages to other neurons through its terminal buttons through its terminal buttons
3) Dendrites 3) Dendrites short outgrowths from the neuron’s cell body that receive signals from other neuron’s terminal buttons short outgrowths from the neuron’s cell body that receive signals from other neuron’s terminal buttons An axon’s terminal buttons communicate with another cell’s dendrites across a tiny, but empty space known as the synaptic cleft
neuronal firing Dendrites are constantly bombarded with messages from other neurons These can be excitatory, prompting the neuron to fire off its own message, or inhibitory, decreasing the probability that the neuron will fire The power to restrain is just as crucial as important as the power to engage in action
Neuronal firing ii After weighing the input it receives from other neurons, a neuron can decide to send a message to another neuron It does so through an electro-chemical process called action potential or neuronal firing
Neuronal firing iii An action potential is the transmission of the signal down the axon through a complex exchange of sodium and potassium ions When the action is over, the positive sodium is pumped back out until next time
Neuronal firing iv In this manner, the signal passes at a steady rate, like a series of dominoes and is not slowed by electrical resistance The message is sped along even faster if the axon is coated with myelin It insulates like the plastic tubing of an electric cord
Neural communication Neurons influence each other through the release of neurotransmitters – chemical substances that carry signals across the synaptic cleft substances that carry signals across the synaptic cleft When the action potential reaches the end of the axon at its terminal button the neurotransmitters are released to travel across the synaptic cleft
Neural comm. ii After passing through the empty synaptic cleft the neurotransmitters attach or bind to receptors on the postsynaptic neuron These neurotransmitters can then make the receiving neuron either more or less likely to fire It is in this infinitesimally small space that irregularities can have profound effects
neurotransmitters There are dozens (at least 60) types and each activates many types of receptors Once they contact the postsynaptic neuron they can either: a) go through reuptake (reabsorbtion) a) go through reuptake (reabsorbtion) b) be swept away through diffusion, b) be swept away through diffusion, c) or leave and then reexcite the neuron c) or leave and then reexcite the neuron
Major neurotransmitters Serotonin – while involved in many behaviors, especially important for emotional states, impulse control, and dreaming Low levels lead to sadness, anxiety, aggression, and food cravings LSD bears a close structural resemblance, when it binds to serotonin receptors involved in dreaming, hallucinations result
Ssri’s Selective Serotonin Reuptake Inhibitors Prevent serotonin from being quickly reabsorbed Introduced in prozac Now wildly popular – even with dogs with dogs Effective and relatively side effect free effect free Should we all be “better than well”?
dopamine Essential influence on motivation and motor control Many think it “tells” us what we find pleasurable Kicks in when we are hungry, thirsty, and aroused to guide us to behaviors which will satisfy our cravings Do drugs enhance its effects (addiction) ?
epinephrine Formerly called adrenaline Activated by our sympathetic nervous system when we need great bursts of energy to flee or stand and fight
endorphins Involved in the suppression of pain Kicks in when pain becomes maladaptive, helping animals feed and breed despite discomfort Administered through drugs like morphine May account for the placebo effect – we feel less pain because we convince ourselves that we should, and release it, confirming our hopes
Neuronal Firing II An Action Potential is the transmission of the signal down the axon through a complex exchange of sodium and potassium ions When the action is over, the positive sodium, is pumped back out until next time
The nervous system From the perspective of contemporary psychology Certain materials in this presentation are used under th Fair Use exemption of The US Copyright Law and should not be used without the permission of their owner.
A survey of the nervous system Within the broad heading of the Nervous System we find many component systems and subdivisions The first are: a) The Central Nervous System – the brain and the spinal cord, and a) The Central Nervous System – the brain and the spinal cord, and b) The Peripheral Nervous System – bundles of axons connecting the spinal cord and the rest of the body. b) The Peripheral Nervous System – bundles of axons connecting the spinal cord and the rest of the body.
The spinal cord A rope of neural tissue that runs inside the hollows of the vertebrae from just above the pelvis into the base of the skull Connected to both sensory ( pain, touch, and pleasure) and motor ( contract and relax muscles) neurons Facilitates reflexes - rapid, involuntary responses to stimulus
Can neurons be repaired? For decades, we thought not Now, as we begin to understand neuroplasticity, hope grows The promise and controversy of stem cells
the peripheral nervous system Divides into : Divides into : a) the Somatic Nervous System – nerves which communicate with the skin and muscles and a) the Somatic Nervous System – nerves which communicate with the skin and muscles and b) the Autonomic Nervous System – nerves which control the involuntary muscles, internal organs (heart, lungs, stomach, etc.) and glands b) the Autonomic Nervous System – nerves which control the involuntary muscles, internal organs (heart, lungs, stomach, etc.) and glands
The autonomic nervous system Two divisions: Two divisions: 1) Sympathetic – prepares your body for action, fight or flight 1) Sympathetic – prepares your body for action, fight or flight blood flows to muscles blood flows to muscles epinephrine increases heart rate epinephrine increases heart rate lungs pull in more oxygen lungs pull in more oxygen sweat forms for cooling sweat forms for cooling
The autonomic nervous system 2) Parasympathetic – returns your body to its resting state, conserves energy 2) Parasympathetic – returns your body to its resting state, conserves energy heart rate slows heart rate slows epinephrine cut off epinephrine cut off lungs relax lungs relax stomach resumes digestion stomach resumes digestion
The endocrine system A set of glands that produce and release hormones These hormones influence thoughts, behaviors and actions Transmitted through the blood Have a global effect as compared to the local effect of neurotransmitters Include the hypothalamus and pituitary