99. Autonomic nervous system. Functional organization of the autonomic nervous system. Characteristics of the sympathetic and parasympathetic division. Neurotransmitters and receptors
Covers the ANS as an involuntary, reflex-driven system and its sympathetic and parasympathetic divisions, with their two-neuron efferent pathways. A comparison table sets out origin, ganglion location and axon lengths for each division. It then describes afferent input from exteroceptors and interoceptors, myelination of the axons, and the neurotransmitters and receptors at each division, ending with recap questions.
Topic 98 of 104 in the MU Sofia syllabus for Physiology (Medicine, Year 2). The free AceMed note covers it in 10 sections, about 512 words (4 min of reading), with 26 flashcards.
In this note
Autonomic nervous system. Functional organization of the autonomic nervous system. Characteristics of the sympathetic and parasympathetic division. Neurotransmitters and receptors.
Autonomic Nervous System (ANS)
Functional Organization
Efferent Pathways (Motor Output)
Characteristics of Sympathetic and Parasympathetic Divisions
Afferent Pathway (Somatosensory Input):
Efferent Pathway (Motor Output):
Motor Response Regulation:
Neurotransmitters and Receptors
Recap Questions
Autonomic Nervous System (ANS)
The ANS is a division of the nervous system that controls involuntary functions, including those of the visceral organs. It plays a crucial role in maintaining homeostasis, regulating processes like heart rate, blood pressure, digestion, and respiration.
The autonomic NS:
♦ Regulates internal organ functions.
♦ Not under voluntary control.
♦ Performs homeostatic control via reflex mechanisms.
Functional Organization
The ANS has two main divisions:
Sympathetic Nervous System: "Fight or flight" response. Prepares the body for action and stress.
Parasympathetic Nervous System: "Rest and digest" response. Conserves energy and promotes relaxation.
Both divisions work together in a coordinated, often reciprocal, manner to control organ function.
Efferent Pathways (Motor Output)
The efferent pathways in both divisions typically involve two neurons:
1. Preganglionic Neuron: Cell body located in the CNS (brainstem or spinal cord). Axon synapses with the postganglionic neuron in an autonomic ganglion.
2. Postganglionic Neuron: Cell body located in an autonomic ganglion. Axon extends to the effector organ.
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