1. Unit 3: Biological Bases of Behavior 3-A (The Neuron) Mr. Debes A.P. Psychology

2. The Neuron Neuron: Neuron: Nerve cell Nerve cell Basic building block of the nervous system Basic building block of the nervous system

3. The Neuron Types of Neurons Types of Neurons Sensory Neurons: Sensory Neurons: Carry incoming information from sensory receptors to the brain/spinal cord; e.g. Perceiving something as “hot” Carry incoming information from sensory receptors to the brain/spinal cord; e.g. Perceiving something as “hot” Motor Neurons: Motor Neurons: Carry outgoing information from the brain/spinal cord to the muscles/glands; e.g. Clenching a fist Carry outgoing information from the brain/spinal cord to the muscles/glands; e.g. Clenching a fist Interneurons: Interneurons: Located within the brain/spinal cord Located within the brain/spinal cord Communicate internally between sensory inputs and motor outputs; e.g. Reflexes Communicate internally between sensory inputs and motor outputs; e.g. Reflexes

4. Parts of the Neuron Cell Body Cell Body Cell’s life support center Cell’s life support center Dendrites Dendrites Bushy extensions that receives messages from outside & conducts impulses towards the cell body Bushy extensions that receives messages from outside & conducts impulses towards the cell body Axon Axon Fiber that extends from the neuron; it passes messages through it’s branches to other neurons, muscles, and/or glands Fiber that extends from the neuron; it passes messages through it’s branches to other neurons, muscles, and/or glands Terminal branches Terminal branches The ends of axon fibers, they form junctions with other cells The ends of axon fibers, they form junctions with other cells Myelin Sheath Myelin Sheath Layer of fatty tissue that encases some axons to help speed neural impulses Layer of fatty tissue that encases some axons to help speed neural impulses

5. The Firing of a Neuron Resting Potential: Resting Potential: When a neuron is not actively conducting an impulse When a neuron is not actively conducting an impulse Difference in electrical charges on the outside and inside of the cell membrane (positive charge outside & negative charge inside) Difference in electrical charges on the outside and inside of the cell membrane (positive charge outside & negative charge inside) This difference in charge is due to different numbers of potassium ions (K + ) and sodium ions (Na + ) on either side of the membrane. This difference in charge is due to different numbers of potassium ions (K + ) and sodium ions (Na + ) on either side of the membrane.

6. The Firing of a Neuron Sodium-potassium pump: Sodium-potassium pump: Cellular mechanism that actively transports (PUMPS) sodium ions outside the neuron’s cell body Cellular mechanism that actively transports (PUMPS) sodium ions outside the neuron’s cell body Simultaneously transports (PUMPS) potassium ions into the neuron’s cell body Simultaneously transports (PUMPS) potassium ions into the neuron’s cell body 3 sodium ions are pumped out for every 2 potassium ions that are pumped in 3 sodium ions are pumped out for every 2 potassium ions that are pumped in This serves to keep the inside of the neuron negatively charged, compared to the outside (3 positive ions leave, 2 positive ions enter) This serves to keep the inside of the neuron negatively charged, compared to the outside (3 positive ions leave, 2 positive ions enter) video

7. The Firing of a Neuron Threshold: Level of stimulation required to trigger an action potential Threshold: Level of stimulation required to trigger an action potential Neurons are constantly receiving hundreds of signals from other neurons. Neurons are constantly receiving hundreds of signals from other neurons. Some signals are excitatory, some signals inhibitory Some signals are excitatory, some signals inhibitory Excitatory signals “push the neuron’s accelerator,” while inhibitory signals “push the neuron’s brakes.” Excitatory signals “push the neuron’s accelerator,” while inhibitory signals “push the neuron’s brakes.” When the excitatory signals a neuron is receiving exceeds the inhibitory signals by a minimum intensity, the threshold has been achieved and a brief change in the electrical charge within the cell occurs When the excitatory signals a neuron is receiving exceeds the inhibitory signals by a minimum intensity, the threshold has been achieved and a brief change in the electrical charge within the cell occurs

8. The Firing of a Neuron Action Potential Action Potential When the threshold is achieved, the electrical charge within the cell changes-Depolarization When the threshold is achieved, the electrical charge within the cell changes-Depolarization Brief electrical charge that travels down an axon Brief electrical charge that travels down an axon As this action potential travels down the axon sections, each axon section depolarizes in turn, further moving the action potential towards the axon terminals As this action potential travels down the axon sections, each axon section depolarizes in turn, further moving the action potential towards the axon terminals “All-or-None”-action potential either occurs or does not. “All-or-None”-action potential either occurs or does not. Refractory period Refractory period After the action potential fires, the neuron pumps positively charged sodium ions back out, preparing to fire again. The action potential/refractory period process repeats hundreds (sometimes thousands) of times a second After the action potential fires, the neuron pumps positively charged sodium ions back out, preparing to fire again. The action potential/refractory period process repeats hundreds (sometimes thousands) of times a second

9. The Firing of a Neuron

16. Review What is a neuron? What is a neuron? Differentiate between the 3 types of neurons: Differentiate between the 3 types of neurons: Sensory Neurons Sensory Neurons Motor Neurons Motor Neurons Interneurons Interneurons Discuss the functions of the following parts of the neuron: Discuss the functions of the following parts of the neuron: Dendrites Dendrites Axon Axon Myelin Sheath Myelin Sheath Terminal Branches Terminal Branches What causes neurons to fire? What causes neurons to fire?

17. Neural Communication Action potential is the mechanism for communication WITHIN a single neuron Action potential is the mechanism for communication WITHIN a single neuron How do neurons communicate with other neurons? How do neurons communicate with other neurons?

18. Neural Communication Synapse: meeting point between neurons Synapse: meeting point between neurons When an action potential reaches the axis terminal, there is no direct contact When an action potential reaches the axis terminal, there is no direct contact There is a gap of 1 millionth of an inch, known as the synaptic gap or synaptic cleft There is a gap of 1 millionth of an inch, known as the synaptic gap or synaptic cleft Neurotransmitters (NTs): chemical messengers that communicate between neurons Neurotransmitters (NTs): chemical messengers that communicate between neurons When an action potential reaches the axis terminal, it triggers the release of chemical messengers When an action potential reaches the axis terminal, it triggers the release of chemical messengers These NTs cross the synaptic gap & unlock channels in the receiving neuron, allowing ions to flow in, either exciting or inhibiting this neuron’s readiness to fire These NTs cross the synaptic gap & unlock channels in the receiving neuron, allowing ions to flow in, either exciting or inhibiting this neuron’s readiness to fire Reuptake: reabsorption of NTs Reuptake: reabsorption of NTs The sending neuron reabsorbs any excess NTs The sending neuron reabsorbs any excess NTs

19. Neural Communication

24. How Neurotransmitters influence us Influence of NTs Influence of NTs Dozens of different kinds of NTs Dozens of different kinds of NTs Many different ways NTs can influence our hunger, thinking, depression, euphoria, addictions, therapy, motions, emotions, etc Many different ways NTs can influence our hunger, thinking, depression, euphoria, addictions, therapy, motions, emotions, etc **This unit, we will focus on the influence NTs have on motions/emotions**

25. Altering Neurotransmission Artificial influences Artificial influences NTs are produced INSIDE the body NTs are produced INSIDE the body Outside influences can impact brain chemistry at the synapses Outside influences can impact brain chemistry at the synapses Drugs & other chemicals Drugs & other chemicals

26. Altering Neurotransmission Agonist Agonist Molecules that are similar to NTs Molecules that are similar to NTs This similarity allows them to mimic it & bind to NT receptors in neurons, replicating it’s affect This similarity allows them to mimic it & bind to NT receptors in neurons, replicating it’s affect Opiate drugs are agonists and produce a “high” feeling by amplifying normal pleasurable sensations Opiate drugs are agonists and produce a “high” feeling by amplifying normal pleasurable sensations Antagonists Antagonists Molecules that are similar to NTs Molecules that are similar to NTs They also bind to NT receptors; instead of replicating the affect of a NT, they block that response They also bind to NT receptors; instead of replicating the affect of a NT, they block that response Botulin (botox) is an antagonists that blocks the release of a NT (ACh), that controls muscles; thus it temporarily paralyzes those muscles Botulin (botox) is an antagonists that blocks the release of a NT (ACh), that controls muscles; thus it temporarily paralyzes those muscles

27. Agonist versus Antagonists

35. Review Explain how neurons communicate with other neurons. Explain how neurons communicate with other neurons. Explain how NTs influence behavior. Explain how NTs influence behavior. Explain how drugs and other chemicals can influence neurotransmission. (make sure to differentiate between agonists & antagonists. Explain how drugs and other chemicals can influence neurotransmission. (make sure to differentiate between agonists & antagonists.