Neurons I bet your neurons are all fired up now!

The Nervous System NEURON = 1 cell Example : Afferent, Efferent and Interneurons  Nerve = a bundle of neurons Example: Optic Nerve, Auditory Nerve

Types of Neurons Efferent (Motor) Neurons - carry outgoing messages from the brain and spinal cord to the muscles and glands Interneurons - neurons within the brain and spinal cord that communicate internally and between sensory inputs and motor outputs Afferent (Sensory) Neurons - carry messages from tissues and sensory organs to the brain and spinal cord for processing

Neurons

Parts of a Neuron Synapse (space between the neuron where chemical messages are sent to dendrites of other cells)

Neurons

How neurons communicate Neurons use an electro-chemical process to send messages Why electrical? – Pushing information through axon is based on process of positive and negative charges of electrical atoms (ions) Potassium (K+), Sodium (Na+), Chloride (Cl-) Why chemical? – Neurotransmitters (chemicals) cross the synapse: different ones send different impulses and need to find receptors – It can either excite (fire) or inhibit (prevent firing) Messages are sent at a speed of mph Neurons are altered with use (learning) – unused neurons die (“neural sculpting)

How does a neuron fire The electrical impulse is called the action potential Step 1 - Resting potential – neuron is charged and ready to fire – Polarized – positive outside, negative inside (Na+) (Cl- & K+) – Selectively permeable – gates do not allow sodium ions to pass through the cell membrane Step 2 - Action potential – brief electrical charge that travels down the neuron – Transmits neural messages to other neurons, muscles or glands – When stimulated – depolarizes Sodium (Na+) rushes in Step 3 - Repolarization – Potassium (Ka+) flows out repolarizing the Axon. Step 4 – Refractory Period – brief period of time when neuron won’t fire no matter how much stimulation Sodium/Potassium pumps push Sodium (Na+) out and Potassium in (Ka+) bringing axon back to a resting state

Action Potential

Electrical Transmission – The Action Potential vard.edu/animations/ac tionpotential_short.swf

How to generate a neural impulse 1.Neuron is stimulated by light, heat, pressure or chemical messages (neurotransmitters) from other neurons. 2.S ignals from other neurons are either – Excitatory - tell neuron to fire (brings neuron closer to firing – Inhibitory - tell neuron not to fire (brings neuron further away from firing) – (excitatory) – (inhibitory) reach minimum threshold, (minimum energy needed for a neuron to fire) an action potential will occur 3.All or None Law – once the neuron fires the impulse moves down the action potential at the same intensity—it can’t be stopped

A brief electrical charge that travels down the axon of a neuron is called the 1.Synapse 2.Agonist 3.Action Potential 4.Resting Potential 5.Refractory period

What disease is related to degeneration of the neuron’s myelin sheath? 1.A. parkinson’s disease. 2.B. Multiple sclerosis. 3.C. Alzheimer’s disease. 4.D. schizophrenia. 5.Huntington’s Disease

The function of dendrites is to 1.receive incoming signals from other neurons. 2.release neurotransmitters into the spatial junctions between neurons. 3.coordinate the activation of the parasympathetic and sympathetic nervous systems. 4.control pain through the release of opiate-like chemicals into the brain. 5.transmit signals to other neurons

The movement of positively charged ions across the membrane of a neuron can produce a(n) 1.Action potential 2.Synapse 3.Neurotransmitter 4.Myelin sheath 5.Interneuron

The axon of a resting neuron has gates that do not allow positive sodium ions to pass through the cell membrane. What is this characteristic called? 1.Myelin sheath 2.Threshold 3.Selective permeability 4.Action potential 5.Refractory period

The minimum level of stimulation required to trigger a neural impulse is called the 1.Reflex 2.Threshold 3.Synapse 4.Action potential 5.All-or-none response

Dendrites are branching extensions of 1.Neurotransmitters 2.Endorphins 3.Neurons 4.Myelin 5.Endocrine Glands

How do neurons communicate with each other? The chemical process

How Neurons Communicate

Inhibition and Excitation Excitation – the process of making the neuron receiving neurotransmitters more likely to generate an action potential (fire) Inhibition – the process of making the neuron receiving neurotransmitters less likely to generate an action potential Excitation>Inhibition for neuron to fire Threshold – minimum stimulation for neuron to fire (-55 mV)

Synaptic Transmission du/content/addiction/rewar d/neurontalk.html

Neurotransmitters Neurotransmitters – Chemical messengers in the brain. Different types affect the brain and behavior in various ways Excitatory neurotransmitters bring the dendrite closer to threshold by allowing positive ions to rush in. (ex. Glutamate) Inhibitory neurotransmitters take the dendrite further away from threshold by allowing negative ions to rush in (ex. GABA)

Drugs can be….. Agonists- mimic neurotransmitters Antagonists- block neurotransmitters Reuptake Inhibitors- block reuptake

Acetylcholine (ACH) Deals with motor movement, memory and learning. Too much and you will…. Too little and you will… Lack of AcH has been linked to Alzheimer’s disease. Black widow – increased AcH Botox – decreased AcH Curare – decreased AcH

Dopamine Deals with motor movement and alertness/attention, emotion, rewards. Lack of dopamine - linked to Parkinson’s disease. Too much - linked to schizophrenia.

Serotonin Regulates sleep, dreaming, mood, pain, aggression, appetite and sexual arousal Depression - Lack of serotonin Anorexia = too much Bulimia – too little

Endorphins Involved in pain control. “endorphins make you happy” – runners high (emotions) Drugs that mimic =. Agonists - Heroine, morphine, codeine

Norepenephrine Fight or flight response Helps control alertness and arousal Undersupply can depress mood

GABA Major inhibitory neurotransmitter meaning it keeps the neuron from firing (slows CNS) Undersupply linked to seizures, tremors, insomnia Alcohol consumption causes an increase in Gaba

Glutamate Major excitatory neurotransmitter Meaning… It causes neurons to fire – overactive CNS Oversupply can over stimulate brain, producing migraines or seizures MSG

Drugs can be….. Agonists- mimic neurotransmitters Antagonists- block neurotransmitters Reuptake Inhibitors- block reuptake

Agonists and Antagonists i_03_m_par/i_03_m_par_cocaine.html#dro gues

Agonist and Antagonists Examples: Agonists – Opiate Drugs Heroine, Morphine (Endorphins) Black Widow Spider Venom (AcH) Antagonists – Botulin (AcH), Botox (AcH), Curare (AcH)

Reuptake refers to the 1.movement of neurotransmitter molecules across a synaptic gap. 2.release of hormones into the bloodstream. 3.inflow of positively charged ions through an axon membrane. 4.reabsorption of excess neurotransmitter molecules by a sending neuron. 5.the ending of the refractory period.

Antidepressants such as Prozac target which neurotransmitter? 1.A. serotonin. 2.B. glutamate. 3.C. GABA. 4.D. acetylcholine. 5.Dopamine

Lindsey has just played a long volleyball match after injuring her ankle in the first game, but feels little fatigue or discomfort. Her lack of pain is most likely caused by the release of 1.Glutamate 2.Dopamine 3.Acetylcholine 4.Endorphins 5.Insuline

A person with schizophrenia may have an overactive dopamine system. Drugs used to treat this disorder prevent the action of dopamine by keeping it from binding to its receptors. These drugs are 1.Agonists 2.Reuptakes 3.Action Potentials 4.Antagonists 5.Synapses

Neurotransmitters that bring a neuron closer to firing are called 1.Agonist 2.Antagonists 3.Inhibitory 4.Reuptake 5.Excitatory

The Nervous System

Central Nervous System Brain Spinal chord Interneurons

Peripheral Nervous System All nerves that are not encased in bone. Everything but the brain and spinal cord. Motor and Sensory Neurons Autonomic and Somatic

Somatic Nervous System Controls voluntary muscle movement. Uses motor (efferent) neurons.

Autonomic Nervous System Controls the automatic functions of the body. – Lungs, stomach, intestines, liver, kidney, heart sympathetic and the parasympathetic

Sympathetic Nervous System Fight or Flight Response. – Arouses and expends energy Causes: – Increase in heart rate, breathing, dilates pupils, slows down digestion, relaxes bladder

Parasympathetic Nervous System Rest and Digest Response Automatically slows the body down after a stressful event. Causes: – Heart rate and breathing slow down, pupils constrict and digestion speeds up.

The peripheral nervous system consists of: A. association areas. B. the spina chord. C. the reticular formation. D. sensory and motor neurons

As Allison reaches for a box in her garage, out jumps a big spider. Her heart immediately begins to race as she withdraws her hand, but soon she realizes that the spider is harmless, and she begins to calm down. Which part of her nervous system is responsible for brining her back to a normal state of arousal? A. sympathetic nervous system B. somatic nervous system C. parasympathetic nervous system D.skeletal nervous system

Reflexes Reflex - a simple, automatic, inborn response to a sensory stimulus – Normally, sensory (afferent) neurons take info up through spine to the brain. – Some reactions occur when sensory neurons reach just the interneurons in the spinal cord = reflex – Survival adaptation.

A Simple Reflex

A Simplified Neural Network Neurons learn to work together as a team. Neurons that fire together, wire together = learning

The Endocrine System A system of glands that secrete hormones. Hormones are similar, but work a lot slower than neurotransmitters. Neurotransmitter nervous system Speed = fraction of a second Hormones blood stream Speed = several sec to travel from gland to tissue Messages outlast neurotransmitters Neurotransmitters Hormones

Figure 3A.11 The endocrine system © 2011 by Worth Publishers Master Gland:- controls other glands Responsible for releasing growth hormones Hypoglycemia – low blood glucose/sugar Hyperglycemia -High blood glucose/suger (diabetes) Overactive = too thin Underactive = too fat Controls pituitary gland Sends info to CNS Adrenaline or epinephrine and norepinephrine Estrogen Testosterone