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Chapter 9
*Nervous System
– Sensory input – monitoring stimuli occurring inside and outside the body
– Integration (processing) – interpretation of sensory input
– Motor output – response to stimuli by activating effector organs
What are the major functions of the nervous system? (9.1)
*Central Nervous System (CNS): includes the brain and spinal cord – this is where information processing occurs.*Emotions, intelligence, memory
*Peripheral Nervous System (PNS): includes the neural tissue of the rest of the body that contains receptors to detect sensory information. (9.2)
*Afferent (sensory) neurons – carry to the brain (CNS) for analysis that are activated by external stimuli
*Efferent (motor) neurons – carry away from CNS to muscles, glands, and tissue.
(9.3)
*Neural Tissue Organization*Three Functional Classes of Neurons
1. Sensory neurons
*Deliver information to CNS
2. Motor neurons
*Stimulate or inhibit peripheral tissues
3. Interneurons (association neurons)
*Located between sensory and motor neurons
*Analyze inputs, coordinate outputs
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
*Somatic nervous system (SNS) – controls muscle contractions
*Autonomic nervous system (ANS) – provides involuntary regulation of smooth muscle, cardiac muscle, and tissues.
*Examples: breathing, heart beat, digestion, and saliva production
(9.4)
*Autonomic NS(9.5)
*Can be divided into:*Sympathetic
Nervous System
*“Fight or Flight”
*Parasympathetic Nervous System
*“Rest and Digest”These 2 systems are antagonistic.Typically, we balance these 2 to
keep ourselves in a state of dynamic balance.
*Sympathetic (9.5)
*“ Fight or flight” response
*Release adrenaline and noradrenaline
*Increases heart rate and blood pressure
*Increases blood flow to skeletal muscles
*Inhibits digestive functions
CENTRAL NERVOUS SYSTEMBrain
Spinalcord
SYMPATHETIC
Dilates pupil
Stimulates salivation
Relaxes bronchi
Accelerates heartbeat
Inhibits activity
Stimulates glucose
Secretion of adrenaline,nonadrenaline
Relaxes bladder
Stimulates ejaculationin male
Sympatheticganglia
Salivaryglands
Lungs
Heart
Stomach
Pancreas Liver
Adrenalgland
Kidney
*Parasympathetic (9.5)
*“ Rest and digest ” system
*Calms body to conserve and maintain energy
*Lowers heartbeat, breathing rate, blood pressure
CENTRAL NERVOUS SYSTEMBrain
PARASYMPATHETIC
Spinalcord
Stimulates salivation
Constricts bronchi
Slows heartbeat
Stimulates activity
Contracts bladder
Stimulates erectionof sex organs
Stimulates gallbladder
Gallbladder
Contracts pupil
*Summary of differences (9.5)
Autonomic nervous system controls physiological arousal
Sympatheticdivision (Exciting)
Parasympatheticdivision (calming)
Pupils dilate EYES Pupils contract
Increases SALIVATION decreases
Perspires SKIN Dries
Increases RESPIRATION Decreases
Accelerates HEART Slows
Inhibits DIGESTION Activates
Secrete stresshormones
ADRENALGLANDS
Decrease secretionof stress hormones
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 8-11 of 7
CENTRAL NERVOUS SYSTEM
PERIPHERALNERVOUSSYSTEM
Receptors
InformationProcessing
Sensory informationwithin
afferent division
Motor commandswithin
efferent division
includes
Somaticnervoussystem
Autonomicnervous system
Parasympatheticdivision
Sympatheticdivision
Skeletalmuscle
Effectors
Smoothmuscle
Cardiacmuscle
Adiposetissue
Glands
Somatic sensoryreceptors (monitorthe outside worldand our position
in it)
Visceral sensoryreceptors (monitorinternal conditions
and the statusof other organ
systems)
*Types of Neuroglial cells (9.6)
1.Astrocytes-star shaped cells that connect neurons together and to their blood supply.
2.Microglia- function as phagocytes by engulfing foreign invaders.
3.Ependymal- (epithelial-like) provide a barrier between brain and spinal fluid.
4.Oligodendrocytes- connect thick neuronal fibers and produce an important insulating material called the myelin sheath.
*Neurons
*Basic unit of the nervous system allowing for functional electric system.
*All neural functions involve the communication of neurons with one another and other cells.
*Neuron Structure (9.7)*Dendrites (branches) –
receive incoming signals
*Axon (trunk) – carries outward signal toward synaptic terminals.
*Synaptic terminal – space between two different neurons (dendrite and axon)
Nerve Fiber Coverings (9.7/9.8)
Slide 7.12Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Schwann cells – produce myelin sheaths in jelly-roll like fashion
· Nodes of Ranvier – gaps in myelin sheath along the axon
Figure 7.5
The Reflex Arc (9.9)
Slide 7.23Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Reflex – rapid, predictable, and involuntary responses to stimuli
· Reflex arc – direct route from a affector neuron, to an interneuron, to an effector
Figure 7.11a
Simple Reflex Arc (9.9) Video
Slide 7.24Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 7.11b, c
Nerve Impulse Transmission (9.10)
*Resting potential: A nerve cell at rest, or inactive has more positive charges outside the cell giving the neuron a slightly negative charge (-70mv)
*Threshold potential: a change (stimulus) in the charge of the resting neuron changes to at least -55mv allowing for an action potential to occur.
*Action potential: the electrical change allows sodium to flow into the cell causing the cell to be depolarized (the neuron changes it’s electrical charge to become positive)
* Nerve Impulse Transmission (9.10)
*Within the neuron’s membrane, there are sodium-potassium pumps allowing for chemical exchange.
*When a threshold potential is applied to the neuron, an action potential (nerve impulse) travels down the neuron.
*The nerve impulse will jump from the axon to the dendrite of another neuron across a synapse by the use of neurotransmitters
(9.11)
*What is saltatory conduction? (9.12)
*Myelin sheath found on the axon insulates and doesn’t allow the depolarization of the membrane.
*The action potential must jump from one node of Ranvier to the next. This makes the action potential move faster down the axon.
*Some can reach speeds of 100 m/s.
*Unmyelinated neurons propagate slow action potentials that must move from one site to the next. This is called continuous conduction.
Saltatory conduction
*Rates of AP Conduction
1. Which do you think has a faster rate of AP conduction – myelinated or unmyelinated axons?
2. Which do you think would conduct an AP faster – an axon with a large diameter or an axon with a small diameter?The answer to #1 is a myelinated axon. If you can’t see why, then
answer this question: could you move 100ft faster if you walked heel to toe or if you bounded in a way that there were 3ft in between your feet with each step?
The answer to #2 is an axon with a large diameter. If you can’t see why, then answer this question: could you move faster if you walked through a hallway that was 6ft wide or if you walked through a hallway that was 1ft wide?
*Synapse Review
*Synapses are gaps between neurons*Exists between the axon of one neuron and the dendrite of another.*Neurons can connect to a large number of other neurons to transmit signals (This accounts for the complexity of the nervous system)*When an action potential reaches the end of an axon, neurotransmitters are stimulated to flood the gap and bond to ion channels on the post synaptic neuron. *This causes an action potential to be produced.
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