Autonomic Nervous System: Divisions, Functions, Anatomy, Function, Disorders

What Is The Autonomic Nervous System (ANS)?

The autonomic nervous system is one of the crucial subdivisions of the PNS. It governs such involuntary activities as heartbeat, blood pressure, digestion rate, and respiratory rate. It runs beneath conscious awareness to maintain homeostasis and to respond to stress.

Two main branches that constitute the ANS are the sympathetic nervous system, which prepares the body for situations concerning 'fight or flight', and the parasympathetic nervous system, leading to 'rest and digest'. These two systems ensure that the body adjusts to various demands but stays balanced within itself.

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The autonomic nervous system plays an essential role in homeostasis because it controls most of the fundamental, vital activities in the body subconsciously. It provides prompt responses to stressors and thus maintains survival and optimal organ functions by distributing energy to sustain life processes like circulation, respiration, and digestion.

Structure Of The Autonomic Nervous System

The ANS is complex in terms of the anatomical basis of its multiple components and pathways through which it exercises its control over bodily functions. There are two main divisions, along with various neurons and ganglia, that function together to transmit signals.

Division Of The ANS

• Sympathetic nervous system: This prepares the body for intense physical activity and stress.

• Parasympathetic Nervous System: Anabolic predominance for rest and recovery.

The Components Of The ANS

• Preganglionic Neurons: Those originating in the central nervous system that conveys the signal to the autonomic ganglia.

• Postganglionic Neurons: Receives signals from preganglionic neurons and innervates target organs.

Anatomy Of Autonomic Ganglia

• Found in various parts of the body; serve as relay stations for nerve impulses.

• Enable nerve impulses from the CNS to reach the target organs.

Diagram: Autonomic Nervous System

Autonomic Nervous System Functions

The ANS is responsible for maintaining homeostasis and bringing about an appropriate response to stimuli.

Homeostasis And Body Regulation

• Heart Rate: the cardiac output is regulated.

• Respiratory Rate: breathing is controlled

• Digestive Processes: the gastrointestinal motility and secretion are controlled.

• Metabolic Functions: influence energy production and use.

Fight Or Flight Response

• Mobilises energy stores and prepares the body to fight or flee threats.

Rest And Digest Response

• Conserves energy and facilitates digestion when at rest.

Autonomic Nervous System Neurotransmitters

Neurotransmitters are chemicals involved in ANS transmission that alter various physiological responses.

Neurotransmitters Types

• Acetylcholine: Used by both sympathetic and parasympathetic systems in the transmission process.

• Norepinephrine: Primarily used by the sympathetic nervous system.

Neurotransmitters In ANS Signaling

• Transmit signals between neurons and from neurons to target tissues.

Receptors In ANS

• Cholinergic Receptors: Bind acetylcholine.

• Adrenergic Receptors: Bind norepinephrine and epinephrine.

Mechanisms Of Autonomic Nervous System Control

The ANS is controlled through central and peripheral mechanisms that act to provide for the precise control of bodily functions.

Central Control

• Hypothalamus: Integrates autonomic functions and maintains homeostasis.

• Brainstem: Controls basic life functions such as heart rate and respiration.

Peripheral Control

• Autonomic Reflexes: Quick, involuntary responses to stimuli.

Feedback Mechanisms

• The continual monitoring and adjustments of physiological processes to maintain homeostasis.

Disorders Of The Autonomic Nervous System

Several disorders and diseases are associated with the ANS; they cause severe health complications.

Dysautonomia

• Genetic inheritance, autoimmune diseases, or injury; major symptoms: fainting, unstable blood pressure, and digestive problems

• Diagnosed by autonomic function tests; medicines and changes in lifestyle for treatment.

Other Disorders Of The ANS

• Postural Orthostatic Tachycardia Syndrome (POTS): Rapid heartbeat upon standing.

Autonomic Neuropathy: It is the damage to autonomic nerves and it is usually seen in the case of Diabetes.

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