Neuron Function Ch. 7b

Functional Classification of Neurons Sensory (afferent) neurons Carry impulses from the sensory receptors Cutaneous sense organs Proprioceptors – detect stretch or tension Motor (efferent) neurons Carry impulses from the central nervous system Slide 7.14a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Functional Classification of Neurons Interneurons (association neurons) Found in neural pathways in the central nervous system Connect sensory and motor neurons Slide 7.14b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Neuron Classification Figure 7.6 Slide 7.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Quick Quiz 1 of 3 What are the three functional types of neurons and what does each do?

Structural Classification of Neurons Multipolar neurons – many extensions from the cell body Figure 7.8a Slide 7.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Structural Classification of Neurons Bipolar neurons – one axon and one dendrite Figure 7.8b Slide 7.16b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Structural Classification of Neurons Unipolar neurons – have a short single process leaving the cell body Figure 7.8c Slide 7.16c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Seniors, 3 more Mondays! Get your Neuron Model out that you worked on last week. We will get materials once class begins. If you have sub work from Thursday staple it and turn it in to tray. **If you missed test, you need to make it up during a lunch period**

Challenge Problem Get out the lab from Mon- I will collect when bell rings 1. List the 5 steps of a reflex arc 2. Which organ gets skipped in a reflex arc? 3. Can you train yourself to react faster to things? 4. If you think you can, give an example 5. The reaction of the pupil to light and the knee jerk to the hammer are examples of __________.

How fast is your reaction time? Distance Time 2 in (~5 cm) 0.10 sec (100 ms) 4 in (~10 cm) 0.14 sec (140 ms) 6 in (~15 cm) 0.17 sec (170 ms) 8 in (~20 cm) 0.20 sec (200 ms) 10 in (~25.5 cm) 0.23 sec (230 ms) 12 in (~30.5 cm) 0.25 sec (250 ms) 17 in (~43 cm) 0.30 sec (300 ms) 24 in (~61 cm) 0.35 sec (350 ms) 31 in (~79 cm) 0.40 sec (400 ms) 39 in (~99 cm) 0.45 sec (450 ms) 48 in (~123 cm) 0.50 sec (500 ms) 69 in (~175 cm) 0.60 sec (600 ms)

Get Crossword puzzle You have 30 min The book may be helpful I will give a few answers 15 min

Functional Properties of Neurons Irritability ability to respond to stimuli Conductivity ability to transmit an impulse Polarized plasma membrane at rest plasma membrane is polarized Negative inside, positive outside the cell Slide 7.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Starting a Nerve Impulse Depolarization a stimulus depolarizes the neuron’s membrane A depolarized membrane allows positive ions of sodium (Na+) to flow inside the membrane The exchange of ions initiates an action potential in the neuron Figure 7.9a–c Slide 7.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

The Action Potential If the action potential (nerve impulse) starts, it propagates through the entire neuron Negative Potassium ions rush out of the neuron after positive sodium ions rush in, which repolarizes the membrane The sodium-potassium pump restores the original configuration This action requires ATP Slide 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Nerve Impulse Propagation The impulse continues to move toward the cell body Impulses travel faster when fibers have a myelin sheath Figure 7.9c–e Slide 7.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Continuation of the Nerve Impulse between Neurons Impulses are able to cross the synapse to another nerve Neurotransmitter is released from a nerve’s axon terminal The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter An action potential is started in the dendrite Slide 7.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

A Nerve Impulse: The short story Stimulus excites dendrites Cell membrane begins to depolarize Impulse travels from dendrites through cell body through axon, depolarizing the whole way. After the impulse passes a part of the neuron, the sodium-potassium pump restores the resting potential of the membrane The impulse leaves the axonal terminals via neurotransmitters, which excite the next neuron’s dendrites

How Neurons Communicate at Synapses Figure 7.10 Slide 7.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Quick Quiz 2 of 3 Explain how a nerve impulse travels through a neuron. What is the purpose of neurotransmitters?

Challenge Problem These neurons take messages from the CNS to muscles and glands. These neurons are only found in the CNS The gap between neurons is called the _______. The way cells communicate between one another is electrical or chemical? Nerve impulses enter the neuron at the _______ and exit the neuron at the _____

Get your neuron model out Make a pile of your models at your table Have the tallest person take your models to the next table according to the board Use the instruction sheet to determine if all the criteria are present on the model

Scoring Guide 1 pt for unipolar sensory neuron 11pts total for all 11 criteria 3 pts possible for neatness and creativity Total= 15pts

The Reflex Arc Reflex – rapid, predictable, and involuntary responses to stimuli Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector Skips the brain!! Figure 7.11a Slide 7.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Simple Reflex Arc Slide 7.24 Figure 7.11b, c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Types of Reflexes and Regulation Autonomic reflexes Smooth muscle regulation Heart and blood pressure regulation Regulation of glands Digestive system regulation Somatic reflexes Activation of skeletal muscles Slide 7.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Quick Quiz 3 of 3 What important organ is skipped in processing a reflex reaction? Explain the journey of a nerve impulse in a reflex arc.

Challenge Problem List the steps of a reflex arc. Which organ in the body gets skipped during a reflex arc? Why do you think it is important that this organ gets skipped? Interneurons are only found in ______ Get out the lab we began Tuesday or get one from the front

Observing Nervous Responses Read the entire lab again I will demo 3 parts You will complete lab and answer analysis questions. We will finish 7b notes beginning at 9:10

Get your Neuron Model stuff out You have ~50 min to complete When finished Get worksheet 118-121 from front to complete