Sistem Saraf (Nervous System)

8/2/2019 Sistem Saraf (Nervous System)

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The Nervous System


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Divisions of the Nervous System


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Nerve Cells

(Electron microscopy x2,250).


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A nerve cell or neuron.


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Transmission of impulse across synapse


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How impulse travels along a neuron to the nextneuron.


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A synapse


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Areas of the brain


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Nerves coming out from the Spinal Cord


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Autonomic nervous system (ANS)

The ANS is a subdivision of the motor division ofthe peripheral nervous system (PNS), whichcontrols involuntary, unconscious body functions

through effector organs that include cardiacmuscle, smooth muscle, and exocrine glands.Some functions of the ANS include contraction ofthe heart and blood vessels, ejaculation, saliva

secretion, and release of glucose from the liver. The autonomic nervous systemis made of two

components, the sympatheticandparasympatheticbranches.


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Sympathetic system The sympathetic system has its origin in thethoraco-lumbar part of the spinal cord. The sympathetic system isalso called the adrenergic system, because the main neurotransmitterreleased at effector organs is adrenaline (epinephrine) andnoradrenaline ( norepinephrine ).

How does the sympathetic nervous system function?

Signals are sent from the hypothalamus and brain stem (medulla and

pons) through the spinal cord to the sympathetic chain ganglia. Thesympathetic ganglia are only a short distance from the spinal cord.Acetycholine is the neurotransmitter.

Postganglionic fibers send signals from the ganglia to effector organs.Norepinephrine (with a few exceptions) is the neurotransmitter.

The adrenal medulla cells are postganglionic neurons. The adrenalmedulla secretes large amounts of norepinephrine and epinephrinedirectly into the blood when stimulated by acetylcholine fromsympathetic preganglionic neurons. This causes a massivegeneralized systemic effect (i.e. fight-or-flight response) in emergency

situations.


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Parasympathetic system The parasympathetic system hasits origins in the sacral part of the spinal cord and cranial

nerves. The parasympathetic system is also called thecholinergic system, because acetylcholine is the mainneurotransmitter.

How does the parasympathetic nervous system function?

Signals arise in the hypothalamus and brainstem and passthrough certain cranial nerves. Most signals pass through thevagus nerve (X or tenth cranial nerve) via preganglionicfibers, which terminate by synapsing with postganglionic

fibers at effector organs. A few fibers originate in the sacralpart of the spinal cord.

Postganglionic fibers are very short and secrete acetylcholineat their terminal synapses.


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THE PERIPHERAL NERVOUS SYSTEM

1. ALL OF THE NERVOUS SYSTEM OUTSIDE THE SPINAL CORD ANDBRAIN IS KNOWN AS THE PERIPHERAL NERVOUS SYSTEM (PNS)(Figure 49-8).

2. THE PERIPHERAL NERVOUS SYSTEM CAN BE DIVIDED INTO TWODIVISION:

A. THE SENSORY DIVISION (AFFERENT)

B. THE MOTOR DIVISION (EFFERENT)

3. THE SENSORY DIVISION TRANSMITS IMPULSES FROM SENSEORGANS - SUCH AS THE EARS AND TASTE BUDS- TO THECENTRAL NERVOUS SYSTEM.

4. THE MOTOR DIVISION TRANSMITS IMPULSES FROM THE CENTRALNERVOUS SYSTEM TO THE MUSCLES OR GLANDS (EFFECTORS).

5. THE MOTOR DIVISION IS FURTHER INTO:

A. THE SOMATIC NERVOUS SYSTEM

B. THE AUTONOMIC NERVOUS SYSTEM.


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THE SOMATIC NERVOUS SYSTEM

1. The Somatic Nervous System regulates activities that ARE UNDER CONSCIOUSCONTROL, movement of skeletal muscles.

2. Every time you lift your finger or wiggle your toes, you are using the MotorNeurons of the Somatic Nervous System.

3. Many Nerves within this system are part of reflexes and can act automatically.

4. A Reflex Sample:

A. Step on a tack with your bare foot.

B. Receptors in the skin stimulated.

C. The Sensory Neurons carry the impulse to Spinal Cord.

D. A group of Neurons in the Spinal Cord AUTOMATICALLY ACTIVATES MotorNeurons.

E. These Motor Neurons cause the Muscles (effectors) in your leg to contract, pullingyou foot away.

5. Notice that this message did not go to the Brain, but was completed in the SpinalCord. (REFLEX)

6. THE RECEPTOR, SENSORY NEURON, MOTOR NEURON, AND EFFECTORTHAT ARE INVOLVED IN THIS QUICK RESPONSE ARE TOGETHER KNOWNAS A REFLEX ARC.


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THE AUTONOMIC NERVOUS SYSTEM

1. THE AUTONOMIC NERVOUS SYSTEM REGULATES ACTIVITIES THAT ARE AUTOMATIC,OR INVOLUNTARY.

2. The Nerves of the Autonomic Nervous System CONTROL Functions of the body that are NOTUNDER CONSCIOUS CONTROL.

3. The Autonomic Nervous system seems to be concerned with striking a balance orMAINTAINING HOMEOSTASIS IN THE FUNCTIONING OF MANY ORGANS OF THEBODY.

EXAMPLES: CONTRACTION IN THE HEART, DIGESTION, HEART RATE, BREATHING,

SALIVATION, AND BLADDER.4. THE AUTONOMIC NERVOUS SYSTEM IS FURTHER SUBDIVIDED INTO TWO PARTS:

A. THE SYMPATHETIC DIVISION

B. THE PARASYMPATHETIC DIVISION

5. The TWO parts have OPPOSITE EFFECTS on the ORGANS they control(See Table 49-1).

6. Most organs controlled by the Autonomic Division are under control of both Sympathetic and

Parasympathetic Neurons.EXAMPLE: Heart Rate is SPEEDED UP by the Sympathetic Nervous System, and it is

SLOWED DOWN by the Parasympathetic Nervous System.

7. The Sympathetic Division generally ACTIVATES ORGANS or SPEEDS UP.

8. The Parasympathetic Division generally RETARDS ORGANS or SLOWS DOWN.


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ParasympatheticSympathetic Response


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Organ Response"Rest and Digest"

Sympathetic Response"Fight or Flight"

Heart(baroreceptor reflex)

Decreased heartrateCardiac outputdecreases

Increased rate and strength of contractionCardiac output increases

Lung Bronchioles Constriction Dilation

Liver Glycogen No effectGlycogen breakdown

Blood glucose increases

Fat Tissue No effectBreakdown of fatBlood fatty acids increase

Basal Metabolism No effect Increases ~ 2X

Stomach

Increasedsecretion of HCl &digestive enzymes

Increased motility

Decreased secretionDecreased motility

Intestine

Increasedsecretion of HCl &digestive enzymesIncreased motility

Decreased secretionDecreased motility

Urinary bladder

Relaxes sphincterDetrusor musclecontractsUrination promoted

Constricts sphincterRelaxes detrusorUrination inhibited

Rectum

Relaxes sphincterContracts wallmusclesDefecationpromoted

Constricts sphincterRelaxes wall musclesDefecation inhibited

EyeIris constricts

Adjusts for nearvision

Iris dilatesAdjusts for far vision

Male Sex Organs Promoteserection Promotes ejaculation
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The thalamusdirects sensory messages to appropriate highercenters. The hypothalamusis involved in emotion and in drives

associated with survival. It also controls the operations of theautonomic nervous system and sends out chemicals that tell thepituitary glandwhen to "talk" to other endocrine glands.


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Sistem Saraf (Nervous System)

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