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

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

Think Pair Share Explain which neuron’s are at work when you swat a mosquito Which neurons are at work when you pick up a fork?

Warmup Think of an example (not one we discussed in class) where you are using a)Afferent neurons b)Efferent neurons c)Interneurons

Neurons

How neurons communicate Electro-Chemical process 1.Electrical – within a neuron – Action Potential – brief electrical charge that sends a message down the neuron Information is pushed through the axon based on process of positive and negative charges of electrical atoms (ions) – Potassium (K+), Sodium (Na+), Chloride (Cl-) 2. Chemical – between neurons – Neurotransmitters (chemicals) travel across the synapse: different ones send different messages on to the next neuron Neurotransmitters can either excite (fire) or inhibit (prevent firing) Messages are sent at a speed of mph

How does a neuron fire Step 1 : Resting potential – neuron is charged and ready to fire (-70mv) – Polarized – positive outside, negative inside (Na+) (K+) – Selectively permeable – gates do not allow sodium ions to pass through the cell membrane Step 2: Threshold – the minimum energy needed to generate an action potential (-55mv) – Excitation- the process of making a neuron more likely to generate an action potential (excitatory neurotransmitters binding to receptors) must be greater than – Inhibition – the process of making the neuron less likely to generate an action potential (inhibitory neurotransmitters binding to receptors) Step 3: Action potential – brief electrical charge that travels down the neuron – Depolarizes - Sodium (Na+) rushes in creating a positive charge on the inside of the cell membrane. – All or None Response – neurons can only send message in one direction at the same speed and strength – Repolarization - Potassium (K+) flows out of the cell membrane, reversing the polarity – Step 4: Refractory period - the recharging period that must occur to ready a neuron to generate another action potential – Sodium/Potassium pumps push Sodium (Na+) out and Potassium in (K+) bringing axon back to resting potential

Action Potential

Electrical Transmission – The Action Potential b.harvard.edu/animatio ns/actionpotential_shor t.swf

Between Neuron Communication Neurotransmitters – the chemical messengers that carry information across the synapse between one neuron and then next are released from terminal buttons on the sending neuron Can be: – Excitatiatory Neurotransmitters – make the neuron receiving neuron more likely to generate an action potential Glutamate – Inhibitory Neurotransmitters – make the neuron receiving neurotransmitters less likely to generate an action potential GABA Synapse – the small gap between neurons which neurotransmitters travel across to send a message to the receiving neuron’s dendrites Reuptake – the process of the sending neuron’s terminal buttons taking back excess neurotransmitters from the synaptic gap

How do neurons communicate with each other? The chemical process

How Neurons Communicate

Synaptic Transmission content/addiction/crossingdivi de/

Think Pair Share – Resting potential – Synapse – Action potential – Repolarization – Refractory period – All-or-None – Threshold – Excitation – Inhibition – Reuptake – Depolarization 1.Put the following terms in order as they occur. 2.Identify which are part of the “electro” (E) part and which are part of the “chemical part” (C) 3.Briefly describe the electro-chemical process of neural transmission:

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 Table

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. Table

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 Table

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 Table

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 Table

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. Table

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

Acetylcholine (ACH) Motor movement, memory and learning. Too much and you will…. Too little and you will… Alzheimer’s disease – lack of AcH Black widow – increased AcH Botox – blocks AcH Curare – blocks AcH

Dopamine Motor movement and alertness/attention, emotion, rewards. Parkinson’s Disease (too little) Schizophrenia (Too much)

Serotonin Emotional State/Mood, Sleep, Depression - Lack of serotonin Anxiety OCD

Endorphins Pain control/perception, mood booster – Examples: – Allows you to continue playing in the game when you sprain your ankle – “endorphins make you happy…happy people don’t kill their husbands” – runners high

Norepenephrine Fight or flight response – increased heart rate, breathing, pupil dilation, High Blood Pressure Anxiety

GABA Inhibition of Brain Activity – Major inhibitory neurotransmitter - keeps the neuron from firing (slows CNS) Undersupply linked to seizures, tremors, insomnia Alcohol consumption causes an increase in GABA

Glutamate Excitation of Brain Activity – Major excitatory neurotransmitter - Meaning… It causes neurons to fire – overactive CNS Migrains MSG

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.Insulin Table

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 Table

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

Agonists and Antagonists i_03_m_par/i_03_m_par_cocaine.html#dro gues

Agonist and Antagonists Examples: Agonists – Opiate Drugs i.e. Heroin, Morphine (Mimic Endorphins) Black Widow Spider Venom (mimics AcH) Antagonists – Botulin (AcH), Curare (AcH) (block neurotransmitters)

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. What are two examples of you using your Somatic Nervous System

Autonomic Nervous System Controls the automatic functions of the body. – Lungs, stomach, intestines, liver, kidney, heart sympathetic and the parasympathetic What are two examples of you using your Autonomic Nervous System

Sympathetic Nervous System Fight or Flight Response. – Arouses and expends energy Causes: – Increase in heart rate, breathing, dilates pupils, slows down digestion, relaxes bladder What are two examples of you using your Sympathetic Nervous System

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. What are two examples of you using your Parasympathetic Nervous system

The peripheral nervous system consists of: 1.A. association areas. 2.B. the spina chord. 3.C. the reticular formation. 4.D. sensory and motor neurons. Table

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? 1.A. sympathetic nervous system 2.B. somatic nervous system 3.C. parasympathetic nervous system 4.skeletal nervous system Table

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

Think Pair Share Which part of your nervous system and which neurons would you rely on most heavily to cross the street? Which part of your nervous system and which type of neuron’s would you use to when Ms. Short arrives at your class and calls you out to the hall, then sends you back to class.

A Simplified Neural Network Neural Network – interconnected cluster of neurons in the CNS 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. Similar too Neurotransmitters Neurotransmitters Hormones NeurotransmittersHormones LocationNervous SystemBlood Stream/Endocrine System SpeedVery fast – fraction of a second Travel from neuron to neuron Slow – several seconds Travel from gland to tissue

Figure 3A.11 The endocrine system © 2011 by Worth Publishers Master Gland:- controls other glands Responsible for releasing (growth hormone Insulin Too Low = hyperglycemia Too high = hypoglycemia Thyroxine Overactive = skinny Underactive = fat Controls pituitary gland Sends info to CNS Adrenaline or epinephrine and norepinephrine cortisol Estrogen Testosterone Pineal Gland – controls circadian rhythm (melatonin) Parathyroid - hormone