nervouse system

7/29/2019 nervouse system

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The Nervous

System

CHAPTER 3:


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Overview

The Nervous System controls andcoordinates all the functions of the body.

The Nervous System consists of two mainsub-divisions:

Central Nervous System (CNS)

Peripheral Nervous System (PNS)

The Peripheral Nervous System is dividedinto two sub-divisions:

Somatic

Autonomic


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Organization

of the

NervousSystem

Figure 7.2


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Functions of the Nervous System

Sensory inputgathering information

To monitor changes occurring inside and

outside the body

Changes = stimuli

Integration

To process and interpret sensory input and

decide if action is needed

Motor output

A response to integrated stimuli

The response activates muscles or glands


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Functions of the Nervous System

Figure 7.1


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Nervous Tissue: Neurons

Neurons = nerve cells

Cells specialized to transmit messages

Major regions of neurons

Cell body - nucleus and metabolic center of thecell

Dendrites Branched parts of a neuron that

receive impulses from other neurons.

Axon single, long fiber that carries impulsesaway form the cell body


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Figure 7.8a

Structural Classification of

Neurons

Multipolar neuronsmany extensions from

the cell body


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Neurons

Bipolar neuronsone axon and one dendrite

Figure 7.8b


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Neurons

Unipolar neuronshave a short single

process leaving the cell body

Figure 7.8c


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Functional Classification of

Neurons

Sensory (afferent) neurons

Carry impulses from the sensory receptors to

the CNS

Cutaneous sense organs Proprioceptorsdetect stretch or tension

Motor (efferent) neurons

Carry impulses from the central nervous

system to viscera, muscles, or glands


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Types of neurons

sensory neuron(from senses)

interneuron(brain & spinal chord)

motor neuron(to muscle)


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Neuron Classification

Figure 7.6


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Functional Classification of

Neurons

Figure 7.7


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How neuron sends a message

To send message, a neuron becomes

excited.

There are two molecules involved

potassium and sodium, move in and out fromneuron.


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Sodium and Potassium cause an electrical

current to form in the area between the

neurons cell body and axon.

If enough sodium and potassium move, theelectrical current is sent all the way down to

the end of the neurons axon.


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When the electrical current reaches the endof axon, it is an area of axon called synapticend bulb.

In the synaptic end bulb, there are small sacscalled vesicles.

The electrical current stimulated the vesiclesto release a molecule called neurotransmitter.

The neurotransmitter will jump to from thesynaptic end bulb across synapse to thedendrite of the next neuron.


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There are receptor molecules on the dendrite

of the second and these receptors are waiting

for the neurotransmitters.

When the neurotransmitter attach to thesereceptors, another electrical signal is

produced.


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Transmission of a Signal at

Synapses

Figure 7.10, step 1

Axonterminal

Vesicles

Synapticcleft

Actionpotential

arrives

Synapse

Axon oftransmitting

neuron

Receivingneuron


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Axon

terminal

Vesicles

Synaptic

cleft

Action

potential

arrives

Axon of

transmitting

neuron

Neurotrans-mitter is re-leased intosynaptic cleft

Neurotrans-mitter bindsto receptoron receivingneuronsmembrane

Vesiclefuses withplasmamembrane

Synaptic cleft Neurotransmittermolecules

Ion channelsReceiving neuron

Transmitting neuron

Receptor

Neurotransmitter

Na+

Na+

Neurotransmitter

broken downand released

Ion channel opens Ion channel closes


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The Reflex Arc

Reflexrapid, predictable, and involuntary

response to a stimulus

Occurs over pathways called reflex arcs

Reflex arcdirect route from a sensoryneuron, to an interneuron, to an effector

Stimulus at distalend of neuron

Skin Spinal cord(in cross section)

Interneuron

Receptor

Effector

Sensory neuron

Motor neuron

Integrationcenter

(a)


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Figure 7.11bc

Spinal cord

Sensory (afferent)

neuron

Inter-neuron

Motor(efferent)neuron

Motor(efferent)neuron

Sensory receptors(stretch receptors

in the quadricepsmuscle)

Sensory (afferent)neuron

Sensory receptors

(pain receptors inthe skin)

Effector(quadricepsmuscle ofthigh)

Effector(bicepsbrachiimuscle)

Synapse in

ventral horngray matter

(c)

(b)


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Types of Reflexes and Regulation

Somatic reflexes

Activation of skeletal muscles

Example: When you move your hand away

from a hot stove


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Autonomic reflexes

Smooth muscle regulation

Heart and blood pressure regulation

Regulation of glands

Digestive system regulation


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Patellar, or knee-jerk, reflex is an example of

a two-neuron reflex arc

Figure 7.11d


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CNS

Central Nervous System is brain & spinal cord


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The Brain

The brain protected by the skull and tough

connective tissue layer.

The average adult human brain weighs 1.3 to

1.4 kg. The brain contains about 100 billion nerve

cells (neurons) and trillons of "support cells"

called glia.
http://faculty.washington.edu/chudler/cells.htmlhttp://faculty.washington.edu/chudler/cells.htmlhttp://faculty.washington.edu/chudler/glia.htmlhttp://faculty.washington.edu/chudler/glia.htmlhttp://faculty.washington.edu/chudler/cells.htmlhttp://faculty.washington.edu/chudler/cells.html


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Human brain


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Cerebrum

The biggest region of the brain

Conscious thought occurs aware of your

thinking

Interpreting Information face recognition

Feeling emotion happiness

The cerebrum divided into separates area -

lobes


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Lobes

The frontal lobes controls motor (skeletal

muscle) activity.

The Temporal lobe memory & interprets

message comes from ears. The Parental Lobe Sensory Information that

comes from the skin and internal organs.

The occipital lobe Interpreting informationthat you see.


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The Brain

Temporal Lobe

Frontal Lobe

Parietal Lobe

Occipital LobeCerebrum

Cerebellum


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Regions of the Brain: Cerebrum


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The Cerebellum

The cerebellum isimportant in maintainingbalance.

The cerebellum receives

messages about yourbody s muscle positions.

After interpreting thosemessage, itcommunicates with the

frontal lobe of thecerebrum to help you tomake decisions aboutmovement.


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The Diencephalons

Thalamus

Hypothalamus

Pituitary gland

Pineal gland

Hypothalamus

Thalamus

Pituitary gland

Pineal gland


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The Thalamus

Functions:

Sensory processing

Movement

Relay station for sensory message arriving

from all over the body

When the sensory message is from ear, the

thalamus makes sure it goes to the part of thetemporal lobe that interprets what you hear.


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The Hypothalamus

Functions:

Body Temperature

Emotions

Hunger Thirst

Circadian Rhythms

- For example, if you are too hot, the hypothalamusdetects this and then sends a signal to expand thecapillaries in your skin. This causes blood to be

cooled faster.


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Pituitary Gland

Growth Hormone (control bone growth)

Produce hormones that regulate other glands

(for examples: thyroid, ovaries, testes,

adrenal)


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Pineal Gland

Thought to maintain the bodys awareness of

the passage of time (body clock)

Produce hormone called melatonin regulate

bodys sense of time.


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The Brainstem

Midbrain

Pons

Medulla oblongata

Midbrain

Pons

Medulla

oblongata


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The Midbrain

The midbrain controls reflexes relating to

sight and hearing

For instance if someone throws a ball at

your face, you blink your eyes.


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The Pons

Make sure your breathe very smoothly


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Medulla Oblongata

The lowest part of the brain stem

Merges into the spinal cord

Includes important fiber tracts

Contains important control centers Heart rate control

Blood pressure regulation

Breathing

Swallowing

Vomiting


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Protection of the Central Nervous

System

Figure 7.17a


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CNS: Spinal Cord

The Spinal cord extends from the back of

your head all the way to your tailbone.


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The Spinal cord

If the spinal cord is damaged, a person can

be paralyzed because message wont be able

to sent from the spinal cord to the rest of the

body The function of spinal cord is

Freeway message travel from body to brain

and brain to body.

Reflect


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The Spinal cord


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Figure 7.22


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Peripheral Nervous System

Connects body to brain & spinal cord

12 pairs of nerves from your brain (cranialnerves)

31 pairs from your spinal cord (spinal nerves) Bundles of sensory and motor neurons held

together by connective tissue


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Nerve

Neurons are organized into larger structure

called nerves.

Nerve form the connection between sensory

receptors (for example: finger tip) the centralnervous system and organs.

There are two major categories of nerves in

the PNS:

Cranial Nerves

Spinal Nerve


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Cranial Nerve

Cranial nerve travel between the brain and

other areas in the head.

There are twelve pair of cranial nerve and

can be classified into three different type ofnerve:

Sensory nerves Carry impulses toward the CNS

Motor nerves - Carry impulses away from the CNS

Mixed Nerves - Both sensory and motor fibers


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PNS: Cranial Nerves

I Olfactory nervesensory for smell

II Optic nervesensory for vision

III Oculomotor nervemotor fibers to eye

muscles IV Trochlearmotor fiber to eye muscles


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PNS: Cranial Nerves

V Trigeminal nervesensory for the face;

motor fibers to chewing muscles

VI Abducens nervemotor fibers to eye

muscles VII Facial nervesensory for taste; motor

fibers to the face

VIII Vestibulocochlear nervesensory for

balance and hearing


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PNS: Cranial Nerves

IX Glossopharyngeal nervesensory for

taste; motor fibers to the pharynx

X Vagus nervessensory and motor fibers

for pharynx, larynx, and viscera XI Accessory nervemotor fibers to neck

and upper back

XII Hypoglossal nervemotor fibers to

tongue


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Figure 7.24


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Spinal Nerve

Spinal nerve travel between spinal cord and

the rest of the body.

There are 31 pairs of spinal nerve that attach

to the spinal cord. Spinal nerve is always mixed nerve.

The spinal nerve carries message from the

specific area of the body to the spinal cord.

It also carries message from the spinal cord

to the muscle in that area of the body.


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The CNS and PNS: A story

One day a man named Joe was cooking when his

hand accidentally touched the stove. Ouch! he

yelled. The sensory receptor in Joes finger felt pain

and heat. These sensory receptor sent a message

along to Joes spinal cord. The spinal cord interpretedthe message to mean: Joes hand felt pain and

heat. The spinal cord them made a decision for Joe

to move hand and arm, making those muscle

contract. Joe had already moved his hand beforegetting realizing he was getting burned.


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The CNS and PNS: A story

The experience on pain of heat made Joe

think about what was happened. That was

dumb. Ill be more careful next time. The

decision to be more careful was made by thebrain.

Automatic movement come from spinal cord

and the ideas produced by the brain


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Joes Story (The Reflex)

Sensory receptor in his hand felt heat and pain (PNS)

A message was sent along nerves (PNS) to the

spinal cord (CNS)

The Spinal cord (CNS) interpreted the message

about the heat and pain in his hand and decided what

to do.

After the spinal cord decided what to do, it sent a

message a long nerve (PNS) to his hand and arm.

Muscle in his hand and arm contracted to move away

from the stove


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The Brain

The message from the Joes pain went at

least two places in the brain, the memory

center ( to remember not to touch the hot

stove again) and a speech center ( to directhim to say ouch!)


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PNS

PNS divided into two major parts: the somatic

nervous system and the autonomic nervous

system.
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Somatic Nervous System

Controls voluntary actions

Made up of the cranial and spinal nerves that

go from the central nervous system to your

skeletal muscles


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Autonomic Nervous System

Controls involuntary actions-those not under

conscious control-such as your heart rate,

breathing, digestion, and glandular functions


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The Sympathetic Division


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Response to fight and flight (scary)

situation.

Example: Ladies saw the rat, either run from

it (flight) or hit it (fight). Task: A woman sees a mouse and is

frightened. How does the body response?



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Sensory receptor in her eyes detect the stimulus. A message is sent along sensory (afferent) neuron to

the CNS.

The message interpreted in the CNS.

The Spinal cord make a decision for the woman tojump on a chair (reflex response)

Brain make decision for her to scream and toincrease her heart rate, breathing rate, and bloodpressure.

Message from CNS are sent along efferent (motor)neurons to different organ needed to response to themouse.

The Organ carry out the response.

A d i f i h d H d


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A woman sees a mouse and is frightened. How does

the body response?

Heart muscle beats faster

Blood vessels constrict (get smaller)

Breathing muscles contract faster

Her leg muscle cause her to jump on herchair

Muscle in her face cause her to scream.


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Mouse

(Stimulus)

Sensory

Receptor

(eye)

Optic Nerve

(Afferent)

Brain

(CNS)

Motor Nerve

(Efferent)

Heart


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Parasympathetic Division

Response on rest and digest

No stress environment

Body is relaxing

Example: has just eaten a meal or sleeping

Slower heart and breathing rate

Decreased blood pressure

Dilation (widening) of pupils Increased activity in the digestive system


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Task

Grandfather just finished eating his dinner. He isrelaxing in his chair. How does the body response?


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Sensory receptor in the stomach detect the presenceof food.

Other sensory receptor in his muscles detect lack of

muscle activity

Message about grandfathers relaxed condition andthe food in his stomach are sent along sensory

(afferent) neurons to the spinal cord and brain

The CNS interpret the message. The spinal cord and

brain decide to prepare the digestive system to digestthe food.


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CNS decide to slow the heart and breathingrate.

Message are sent from the CNS along

efferent neurons to the digestive organ, heartand breathing muscles.

The organ carry out the response.

The heart is slow down, breathing muscles

slow down and muscles and glands in the

digestive system are activated.

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