3 2 Role of Human Nervous System 2

7/31/2019 3 2 Role of Human Nervous System 2

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Made up of The central nervous system

The peripheral nervous system

Nervous system

Central nervous system

Brain Spinal Cord

Peripheral nervous system

Cranial nerve Spinal nerve

branch fromthe brainconnect brainto sensory andeffector at the

head

branch from thespinal cordconnect the spinalcord to sensory andeffector at the thorax,

abdomen, limbs


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The brain function as a coordinating andintegrating centre:

receive information from receptors

analyse information

integrate information

store information

transmit instruction to effectors


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Cerebrum

largest part

divided into right

hemisphere and lefthemisphere

in each hemisphere,contains motor area

(coordinate skeletalmuscles) and sensory area(responsible for sensation ofheat, touch etc)


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Cerebrum

Functions : control all mental activities

e.g thinking, intelligence,memory, learning, reasoning,problem solving

detect sensations e.g pain,

touch, heat, cold, sight,hearing, taste, smell

control skeletal muscles

Control and coordinate all

voluntary activities


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Cerebrellum

Functions :

coordinate the contractionof muscles

control equilibrium of thebody

maintain balance


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Medulla Oblongata

Functions :

Control and regulatesinvoluntary actions

heartbeat, peristalsis, bloodpressure, breathing

Centre for certain reflexaction e.g vomitting,coughing, sneezing,

swallowing


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Hypothalamus

Functions :

Detect changes in bodytemperature and osmoticpressure

Regulate sleep, hunger,thirst, blood pressure

Pituitary Gland

Secretes hormones (worktogether with hypothalamus)


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Thalamus

Functions :

sorting information whichgoes in and comes out

integration centre for sensoryimpulses


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Continuation of the medulla oblongata

Located in the vertebral column

Consists of a grey matter in the shapeof H in the middle and a white matteraround it.


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Spinal nerves arise from the spinal cord.

Branches into the dorsal and the ventral root

Central canal (centre of the spinal cord)

filled with cerebrospinal fluid.

Functions of spinal cord :

1. Links the brain to the peripheral nervous

system2. Controls reflex action


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Nerve cells that carry information in theform of electrical signals called nerveimpulses.


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Neurone consists of

One cell body contains anucleus and cytoplasm

Extensions

Axon carries nerve impulse

away from the cell body Dendron carries nerve

impulse towards the cellbody.

Dendron form a threadlikestructure called dendrites

Axon branches to form axonterminals with a synapticknob at its end.


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Neurone (contd) Axon is surrounded by an

insulating membrane (madefrom fats) called myelinsheath.

Has many gaps along it calles

nodes of Ranvier. Functions of myelin sheath:

1. Protect the nerve fibre

2. Supply nutrients to axon

3. Insulator to the nerveimpulse

4. Increase the speed ofimpulse impulse jump

from one node to the next


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Three types of neurones:

1. Afferent neurone (sensory neurone)

2. Efferent neurone (motor neurone)

3. Interneurone


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Afferent neurone

Links the receptors to the central nervous

system. Carry the impulse from receptors to the

central nervous system.


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Efferent neurone

Links the central nervous system to the

effectors. Carry the impulse from central nervous

system to the effectors to produce response.


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Interneurone

Located in the central nervous system.

Link afferent neurone and efferent neurone.

Transmitted the impulse from afferentneurones to the efferent neurones.


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Afferent neurone Efferent neurone Interneurone

Nerve impulse :Receptor Centralnervous system

Nerve impulse :Central nervoussystem Effector

Nerve impulse :Afferent neurone Efferent neurone

Cell body : At theganglion of the dorsalroot of the spinal cord

Cell body : At the greymatter of the spinalcord

Cell body : At the greymatter of the spinalcord

Long dendron and

axon

Long axon Short dendron and

axonDendrite begins at thereceptor

Axon terminal ends atthe effector

Dendrites and aconterminals are locatedin the central nervoussystem


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Nerve impulses is carried along theneurones in the form of electrical

impulse. Travels in one direction from dendrites to

axon terminals.

Begins at the receptors and ends at theeffectors.


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Nervoussystem

Effector

ResponseStimulus

Receptor

detected by produce

Nerve impulses

via afferent neurone via efferent neurone


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1. Receptor detects the stimulus.

2. Nerve impulses are carried by the afferentneurone to the central nervous system.

3. The central nervous system integrates andinterpret the information.

4. The central nervous system send nerveimpulses carried by the efferent neurone tothe effector.

5. Effector produce response.


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Neurones are notdirectly connectedthere is a gap called

synapse. Synapse between axon

terminal with the dendriteof another neurone. Contains a lot of

mitochondria and vesiclescontainingneurotransmitters(acetylcoline &noradrenaline)


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1. Nerve impulse arrive ataxon terminal (synapticknob)

2. Nerve impulse stimulatesthe vesicles to releaseneurotransmitters.

3. Neurotransmitters diffuseacross the synapse to the

subsequent dendrite.4. Energy required is supplied

by the mitochondria5. Dendrite is stimulated, and

will pass the impulse


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Controlled by the cerebrum of the brain.

Involves the process of integration andinterpretation of information to produceresponse.

Example : kick a ball Sight of the ball stimulates the receptor in the

eye information will be sent to the cerebrum The information about the ball is interpreted in

the motor area of the brain sent to theskeletal muscle of the leg to produce aresponse, that is to kick the ball.


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Automatic action not controlled by thewill of an individual

Controlled by medulla oblongata e.g peristalsis, heartbeat, breathing

We are not aware of the responses

Autonomic nervous system regulatesinternal body process


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Autonomic nervous system has twodivisions

Sympathethic prepare body for stressful oremergency situation (fight or flight)

Parasympathetic prepare body for ordinarysituation (rest and digest)


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Structure Sympatheticstimulation

Parasympatheticstimulation

Iris Pupil dilation Pupil constriction

Salivary Glands Saliva reduced Saliva increased

Heart Heart rate increased Heart rate reduced

Lung Bronchial musclesrelaxed

Bronchial musclescontracted

Stomach Peristalsis reduced Gastric juice increased,motility increased


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Voluntary Aspect Involuntary

Occur in the will of anindividual

Type of action Does not occur in the willof an individual

Cerebrum Integrating centre Medulla oblongataInvolves external stimuli Stimulus Involves internal stimuli

Sensory organ Receptor Special internal receptors

From the brain toskeletal muscles

Transmission of impulse From medulla oblongatato smooth muscles,cardiac muscles andglands

Effector produce avoluntary action e.g kick

a ball

Effector and Response Effector produceinvoluntary action e.g

heartbeat and peristalsis


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Reflex Action involuntary action thatoccurs automatically and spontaneouslywithout conscious control of towards a

stimulus Controlled by the spinal cord (does not

involve cerebrum)

Act as protection against injuries

Examples : Knee jerk

Withdrawal of hand from a hot object

Blinking of the eyes


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Reflex Arc pathway that a nerve impulsetravels from the receptor to the effector

Consists of receptor, afferent neurone,

interneurone in the spinal cord, efferentneurone and effector.

Examples Withdrawal of the hand from a hot object;

involves three neurones; afferent neurone,interneurone, efferent neurone

Knee jerk; involves two neurones; afferentneurone, efferent neurone


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ReceptorAfferentneurone

(dorsal root)Synapse

Interneurone

SynapseEfferentneurone

(ventral root)Effector

Spinalcord


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When the hand touch a hot object, receptors arestimulated

Impulses is generated travels along afferent neuroneto the spinal cord

Impulse travels to an interneurone then transmitted toanother synapse of the efferent neurone.

Impulse in carried to the muscle.

Also involve other neurones in the brain enable theperson to feel the sensation of heat and pain


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When the tendon below the kneecap is tapped,quadriceps muscle stretched - will trigger nerveimpulse

Impulse is transmitted to the spinal cord by afferentneuron

Nerve impulse is transferred across a synapse toefferent neurone in the spinal cord.

Nerve impulse stimulate the quadriceps muscles to


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Alzheimers disease

Neurodegenerative disease characterized byprogressive cognitive deterioration (loss of

intellectual ability and memory) Usually affects the elderly and can be inherited

Symptoms :

1. Lost of memory

2. Lack of concentration

3. Confusion and hallucination

4. Poor judgement

5. Loss of ability to speak, read, write and walk


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Parkinsons disease

Disease that affects the part of the brainwhich control the muscles.

Muscles become weak and stiff will causejerkiness

Due to the reduced level of a neurotransmittercalled dopamine in the brain.

Symptoms1. Slow movement

2. Jerkiness

3. Weak muscles

3 2 Role of Human Nervous System 2

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