1. Nervous System
Chapter 9

2. What are the major functions of the nervous system? (9.1)
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

3. 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)

4. 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)

5. 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

6. 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)

7. 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.

8. Sympathetic (9.5) “ Fight or flight” response
CENTRAL NERVOUS SYSTEM
Brain
Spinal
cord
SYMPATHETIC
Dilates pupil
Stimulates salivation
Relaxes bronchi
Accelerates heartbeat
Inhibits activity
Stimulates glucose
Secretion of adrenaline,
nonadrenaline
Relaxes bladder
Stimulates ejaculation
in male
Sympathetic
ganglia
Salivary
glands
Lungs
Heart
Stomach
Pancreas
Liver
Adrenal
gland
Kidney
“ Fight or flight” response
Release adrenaline and noradrenaline
Increases heart rate and blood pressure
Increases blood flow to skeletal muscles
Inhibits digestive functions

9. Parasympathetic (9.5) “ Rest and digest ” system
CENTRAL NERVOUS SYSTEM
Brain
PARASYMPATHETIC
Spinal
cord
Stimulates salivation
Constricts bronchi
Slows heartbeat
Stimulates activity
Contracts bladder
Stimulates erection
of sex organs
Stimulates gallbladder
Gallbladder
Contracts pupil
“ Rest and digest ” system
Calms body to conserve and maintain energy
Lowers heartbeat, breathing rate, blood pressure

10. Summary of differences (9.5)
Autonomic nervous system controls physiological arousal
Sympathetic
division (Exciting)
Parasympathetic
division (calming)
Pupils dilate EYES Pupils contract
Increases SALIVATION decreases
Perspires SKIN Dries
Increases RESPIRATION Decreases
Accelerates HEART Slows
Inhibits DIGESTION Activates
Secrete stress
hormones
ADRENAL
GLANDS
Decrease secretion
of stress hormones

11. Figure 8-1 1 of 7 CENTRAL NERVOUS SYSTEM PERIPHERAL NERVOUS SYSTEM
Information
Processing
PERIPHERAL
NERVOUS
SYSTEM
Sensory information
within
afferent division
Motor commands
within
efferent division
includes
Somatic
nervous
system
Autonomic
nervous system
Parasympathetic
division
Sympathetic
division
Receptors
Effectors
Smooth
muscle
Somatic sensory
receptors (monitor
the outside world
and our position
in it)
Visceral sensory
receptors (monitor
internal conditions
and the status
of other organ
systems)
Skeletal
muscle
Cardiac
muscle
Glands
Adipose
tissue
Figure 8-1
1 of 7
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

12. Types of Neuroglial cells (9.6)
Astrocytes-star shaped cells that connect neurons together and to their blood supply.
Microglia- function as phagocytes by engulfing foreign invaders.
Ependymal- (epithelial-like) provide a barrier between brain and spinal fluid.
Oligodendrocytes- connect thick neuronal fibers and produce an important insulating material called the myelin sheath.

14. 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.

15. 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)

17. Nerve Fiber Coverings (9.7/9.8)
Schwann cells – produce myelin sheaths in jelly-roll like fashion
Nodes of Ranvier – gaps in myelin sheath along the axon
Figure 7.5
Slide 7.12
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

18. The Reflex Arc (9.9)
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
Slide 7.23
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

19. Simple Reflex Arc (9.9) Video
Figure 7.11b, c
Slide 7.24
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

20. 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)

21. 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
Nerve Impulse Transmission (9.10)

22. (9.11)

23. 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.
What is saltatory conduction? (9.12)

24. Saltatory conduction

25. Rates of AP Conduction
Which do you think has a faster rate of AP conduction – myelinated or unmyelinated axons?
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?

26. 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.