Neurons Outline

10 Pages
Unlock Document

Psychological & Brain Sciences
PSY-P 101
Lisa Thomassen

Neurophysiology Neurons We begin with cells… Neurons are identified by direction of transmitted information:  sensory (direction) neurons: from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) torward the central nervous system.  Motor (efferent) neurons: away from the central nervous system to muscles or glands. SAME  Sensory Afferent Motor Efferent  Interneurons all the rest, greatest number, between sensory neurons and motor neurons, mostly in the CNS No Brainer: the Reflex Action Exception to the standard pathway: Reflexes processed in spinal cord not the brain  Reflex pathway: Afferent system afferent system neuron) →interneuron pathway → spinal cord → Efferent system (motor neuron) →muscle contracts Exp. Burn hand, yank it away Dendrites  Receives information o 1000s of branches o Enable receiving information from many sources Soma  Main “body” of the cell  Metabolic center  Genetic material stored here  Information is processed here Neurons do NOT go through cell division (no centrioles, so no mitosis) Axon  Transmits information  Action potential travels down the axon in a chemical chain reaction  Terminal buttons are part of the axon on the end or tip  Vesicles here release chemical neurotransmitters into the synapse (gap)  Bundles of long axons make up nerves  (Axons may be several feet long) Neural Transmission Synapse: Super-tiny gap between the terminal buttons of one neuron and the dendrite of the next one Neurotransmitters flow into the synapse from the terminal buttons (boutons) Neural transmission: Synapse ->Dendrites->Soma->Axon->Terminal Buttons-> Synapse etc.etc.etc. “presynaptic” refers to axon-related phenomenon (transmission) “postsynaptic” refers to dendrite-related phenomenon (receiving) Glial cells (“glue”) – CNS support cells -- 10x more plentiful than neurons 10% of the brain myth? -- Involved in recycling neurotransmitters -- Myelin sheath (Axons are White Matter) 100 billion brain cells (neurons) 1 trillion support cells (glia) We lose ~9,000 neurons a day BRAIN CELL DEATH Some drugs are very damaging:  Ketamine  Nitrous oxide (laughing gas)  Huffing volatile inhalants (glue, gasoline, paint thinner) Cause brain cell death THIRTY TIMES normal rates - almost 300,000 neurons a day! Alcohol also increases the rate of brain cell death Chemistry: the Resting Potential Tiny negative electrical charge between inside and outside of neuron Created by electrically charged particles (ions) Some concentrated outside the cell Sodium + and chloride - ions Some concentrated inside the cell Potassium + ions, proteins - Cell membrane has ion channels for Potassium + and Sodium +: pumps out sodium Some potassium can “leak out” permeable membrane Net effect is neg. as positive ions leave Action Potential: Excitatory Message  1 : Neuron receives stimulation (mechanically, or via neurotransmitter)  2 : Sodium channel opens, sodium rushes in, so more positive charge  3 : When threshold voltage is reached, action potential occurs Excitatory messages  Depolarization Cell becomes less negative, to threshold wave of depolarization (chain reaction) Resting Potential: Hyperpolarization  Inhibitory messages  Hyperpolarization  Cell becomes more negatively charged, when some neurotransmitters (such as GABA) inhibit neuron from firing by opening channels that let– chloride in, and +K out (adds -, lets out +)  larger stimulus is required to reach threshold for action potential The Action Potential “All or nothing” when triggered at depolarization  Does not vary in strength or intensity  Travel down the axon between 2 and 200 m.p.h.  Speed increased if neuron is myelinated.  Nodes of Ranvier, site of saltatory conduction  Essentially a chain reaction of depolarization, as each site reaches the threshold Demonstration with Dominos and Sticks Action Potential Saltatory Conduction Neurotransmitters  Dopamine When action potential reaches the end of the axon, it triggers vesicles (sacs) in the terminal buttons (boutons) to release chemicals called neurotransmitters.  These activate receptors in the postsynaptic membrane in the next neuron  Communication is all about chemicals and receptors How Drugs affect the Brain: Agonists:  bind to the receptors for the neurotransmitter  directly stimulate the receptors  Mimic the action of neurotransmitters  Nicotine mimics AcH (nicotinic ACH receptor)  L-dopa mimics the effects of dopamine (Parkinson’s)  Valium mimics GABA  Heroin mimics the endorphins (endogenous morphine) Antagonists:  bind to the receptors  prevent neurotransmitter from acting  Block the action of neurotransmitters. o Curare blocks AcH o Hallucinogens attaching to seratonin receptor sites, block perceptual pathway transmission. Neuromodulators: Modulat
More Less

Related notes for PSY-P 101

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.