Neurons I bet your neurons are all fired up now!

The Nervous System NEURON = 1 cell  Nerve = a bundle of neurons

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 cross 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 – 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 don 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 - Return to Resting Potential Sodium/Potassium pumps push Sodium (Na+) out and Potassium in (Ka+) bringing axon back to a resting state Step 5 - Refactory period – Brief period of time when neuron won’t fire no matter how much stimulation

Action Potential

Electrical Transmission – The Action Potential cb.harvard.edu/ animations/actio npotential.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) or – inhibitory (tell neuron not to fire) – (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

How do neurons communicate with each other? The chemical process

How Neurons Communicate

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

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

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. Inhibitory neurotransmitters take the dendrite further away from threshold by allowing negative ions to rush in

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. Too little - depression

Serotonin Involved in mood control, hunger, sleep and arousal. Lack of serotonin has been linked to clinical depression Linked with anorexia = too much serotonin Sleep disorders

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

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

GABA Major inhibitory neurotransmitter (inhibits CNS) Hunger and Sleep Undersupply linked to seizures, tremors, insomnia Alcohol consumption causes an increase in Gaba

Glutamate Major excitatory neurotransmitter Involved in memory and learning Oversupply can over stimulate brain, producing migraines or seizures MSG

The Nervous System

Central Nervous System The Brain and spinal cord CNS

Peripheral Nervous System All nerves that are not encased in bone. Everything but the brain and spinal cord. Is divided into two categories….somatic and autonomic.

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

Autonomic Nervous System Controls the automatic functions of the body. Divided into two categories…the sympathetic and the parasympathetic

Sympathetic Nervous System Fight or Flight Response. Automatically accelerates heart rate, breathing, dilates pupils, slows down digestion.

Parasympathetic Nervous System Automatically slows the body down after a stressful event. 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 that learn to work together as a team.

The Endocrine System A system of glands that secrete hormones. Similar to nervous system, except hormones work a lot slower than neurotransmitters. Neurotransmitters Hormones

The Major Endocrine Glands