3. Autonomic Nervus System (Ans)

AUTONOMIC NERVUS SYSTEM (ANS)

Zahreni HamzahRahardyan ParnaadjiLab. Fisiologi – Bag Biomedik FKG Univ. Jember

05/02/23 Free Template from www.brainybetty.com 2

How is the organization of the autonomic nervous

system (ANS) different from that of the somatic nervous

system (SNS)?


Autonomic Nervous System (ANS)

• Operates without conscious instruction• Coordinates systems functions:

– cardiovascular– respiratory– digestive– urinary– reproductive

• Sistem ini merupakan sistem saraf eferen (motorik) yang mempersarafi organ-organ dalam seperti otot-otot polos, otot jantung, dan berbagai kelenjar.

• Sistem ini juga melakukan fungsi kontrol, semisal: kontrol tekanan darah, sekresi gastrointestinal,pengosongan kandung kemih, proses berkeringat, suhu tubuh, dan beberapafungsi lain.

• Karakteristik utama SSO:• kemampuan mempengaruhi yang sangat

cepat (misal: dalam beberapa detik denyut jantung dapat meningkat, perubahan tekanan darah, berkeringat).

• Keterlibatan dengan SSP: Medulla spinalis bertanggung jawab untuk persarafan otonom yang memengaruhi sistem kardiovaskular dan respirasi

• Hipotalamus berfungsi :Mengintegrasikanpersarafan otonom, somatik, dan hormonal (endokrin) dan emosi serta tingkah laku Misal: seseorang yang marah meningkatkan denyut jantung,tekanan darah, dan laju respirasi.


ANS in the Nervous System

• Refleks visceral, sama seperti refleks somatik lainnya, terdiri atas komponen reseptor, integrasi, dan efektor.

Pembeda refleks visceral dengan refleks somatik:Informasi reseptor refleks visceral diterima secara bawah-sadar (subconscious). Misal: Pembuluh darah melebar (kulit yang kemerahan).Pupil mata melebar.

• PERJALANAN SSO DIMULAI DARI PERSARAFAN SSP:

• Neuron (orde pertama) berada di SSP (sisi lateral medullaspinalis dan di batang otak) > preganglionic fiber.

• Serabut ini bersinaps dengan badan sel neuron orde kedua yang terletak di dalam ganglion.

• Serabut pascaganglion menangkap sinyal dari serabut preganglion melalui neurotransmiter yang dilepaskan oleh serabut preganglion.

• (Ganglion: kumpulan badan sel yang terletak di luar SSP).

• Akson neuron orde kedua (postganglionic fiber) menuju organ yang akan diinervasi.

• Organ efektor menerima impuls melalui pelepasan neurotransmiter oleh serabut pascaganglion.


Comparison of Somatic and Autonomic Nervous Systems


Organization Similarities of SNS and ANS

• Are efferent divisions • Carry motor commands:

– SNS controls skeletal muscles– ANS controls visceral effectors

• Motor neurons synapse on visceral motor neurons in autonomic ganglia

• Ganglionic neurons control visceral effectors


Organization Similarities of SNS and ANS


Neurotransmitters and Receptors

• Acetylcholine (ACh) and norepinephrine (NE) are the two major neurotransmitters of the ANS

• ACh is released by all preganglionic axons and all parasympathetic postganglionic axons

• Cholinergic fibers – ACh-releasing fibers • Adrenergic fibers – sympathetic postganglionic

axons that release NE • Neurotransmitter effects can be excitatory or

inhibitory depending upon the receptor type

• Serabut preganglion parasimpatis melepaskan neurotransmitter asetilkolin (ACh) yang ditangkap oleh reseptor kolinergik nikotinik badan sel pascaganglion.

• Efek dari penangkapan ACh oleh reseptor nikotinik menyebabkan pembukaan kanal ion nonspesifik, menyebabkan influx terutama ion Na+


Pelepasan Neurotransmitter

• Setelah itu, serabut pascaganglion parasimpatis juga menghasilan asetilkolin yang ditangkap oleh reseptor kolinergik muskarinik yang terdapat di semua organ efektor parasimpatis.

• Penempelan Ach dapat menginhibisi atau mengeksitasi organ efektor.


• Serabut preganglion simpatis melepaskan neurotransmitter ACh yang ditangkap oleh reseptor nikotinik yang berada di badan sel neuronpascaganglion.

• Serabut pascaganglion melepaskan noradrenalin (atau norepinefrin) dan ditangkap oleh reseptor adrenergik.


Pelepasan Neurotransmitter


Differences between SANS and PANS


What are the divisions and functions of the ANS?


• Sympathetic Division :– “Kicks in” only during exertion, stress, or

emergency• Parasympathetic Division :

– Controls during resting conditions

• 2 divisions may work independently:– some structures innervated by only 1 division

• 2 divisions may work together:– each controlling one stage of a complex

process

• Divisi parasimpatis cenderung mengatur organ efektor dalam keadaan rest-and-digest, yakni ketika tubuh berada dalam keadaan tenang,relaks, kondisi yang tidak mengancam, atau dalam keadaan “pembersihan dan pemulihan tubuh” ( general housekeeping).





Parasympathetic Division OutflowCranial Outflow

Cranial Nerve Ganglion Effector Organ(s)

Occulomotor (III) Hypothalamic Control

Ciliary Eye

Facial (VII) PterygopalatinSubmandibular

Salivary, nasal, and lacrimal glands

Glossopharyngeal (IX)

Otic Parotid salivary glands

Vagus (X) Located within the walls of target organs

Heart, lungs, and most visceral organs

Sacral Outflow

S2-S4 Located within the walls of the target organs

Large intestine, urinary bladder, ureters, and reproductive organs



Visceral Reflexes

What are the mechanisms of neurotransmitter

release in the sympathetic division?


SANS


Sympathetic Receptors• Sympathetic Receptors

– Alpha receptors– Beta receptors

• Norepinephrine stimulates alpha receptors to greater degree than beta receptors

• Epinephrine stimulates both classes of receptors.

• Sympathetic postganglionic Fibers– Mostly adrenergic (release NE)– A few cholinergic (release ACh)


Alpha (α) Receptors (activated by enzymes on inside of cell membrane)

Reseptor α-1• More common type of

alpha receptor• Releases intracellular

calcium ions from reserves in endoplasmic reticulum

• Has excitatory effect on target cell

Reseptor α-2• Lowers cAMP levels

in cytoplasm• Has inhibitory effect

on the cell• Helps coordinate

sympathetic and parasympathetic activities


Beta () Receptors• Affect membranes in many organs (skeletal muscles,

lungs, heart, and liver)• Trigger metabolic changes in target cell• Changes occur indirectly• Each is a G protein • Stimulation increases intracellular cAMP levels• Beta-1 (1) - Increases metabolic activity• Beta-2 (2)

– Causes inhibition– Triggers relaxation of smooth muscles along respiratory tract

• Beta-3 (3)– Is found in adipose tissue– Leads to lipolysis, the breakdown of triglycerides in adipocytes– Releases fatty acids into circulation


Adrenal Medulla

• Preganglionic fibers entering adrenal gland proceed to center (adrenal medulla)

• Modified sympathetic ganglion• Preganglionic fibers synapse on

neuroendocrine cells• Specialized neurons secrete hormones

into bloodstream


7 Responses to Increased Sympathetic Activity

1. Heightened mental alertness2. Increased metabolic rate3. Reduced digestive and urinary functions4. Energy reserves activated5. Increased respiratory rate and

respiratory passageways dilate6. Increased heart rate and blood pressure7. Sweat glands activated

What are the structures and functions of the

parasympathetic division of the autonomic nervous

system?



Parasympathetic Division

• Preganglionic fibers originate in brain stem and sacral segments of spinal cord

• Synapse in ganglia close to (or within) target organs

• Preganglionic fibers are long• Postganglionic fibers are short


Parasympathetic Activation

• Centers on relaxation, food processing, and energy absorption

• Localized effects, last a few seconds at most


Parasympathetic Receptors• Action of Nicotinic Receptors

– Exposure to ACh causes excitation of ganglionic neuron or muscle fiber

– Open chemically gated channels in postsynaptic membrane

• Action of Muscarinic Receptors– Can be excitatory or inhibitory– Effects are longer lasting than nicotinic

receptors


10 Effects of Parasympathetic Activation

1. Constriction of pupils:– restricts light entering eyes

2. Secretion by digestive glands:– exocrine and endocrine

3. Secretion of hormones4. Changes in blood flow and glandular activity:

– associated with sexual arousal

5. Increases smooth muscle activity:– along digestive tract


10 Effects of Parasympathetic Activation

6. Defecation:– stimulation and coordination

7. Contraction of urinary bladder:– during urination

8. Constriction of respiratory passageways9. Reduction in heart rate:

– and force of contraction10.Sexual arousal:

– stimulation of sexual glands


Parasympathetic division• The parasympathetic division release ACh• Body wall and skeletal muscles are not

innervated by parasympathetic division• Both NE and ACh needed to regulate

visceral functions


Sympathetic and Parasympathetic Responses

Structure Sympathetic Stimulation Parasympathetic Stimulation

Iris (eye muscle)

Pupil dilation Pupil constriction

Salivary Glands

Saliva production reduced

Saliva production increased

Heart Heart rate and force increased

Heart rate and force decreased

Lung Bronchial muscle relaxed Bronchial muscle contracted

Stomach Peristalsis reduced Gastric juice secreted; motility increased

Kidney Decreased urine secretion

Increased urine secretion

Bladder Wall relaxedSphincter closed

Wall contractedSphincter relaxed

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3. Autonomic Nervus System (Ans)