Autonomic Nervous System Flashcards
What is the autonomic nervous system (ANS)?
The autonomic nervous system is a part of the peripheral nervous system (PNS) that provides involuntary information from the central nervous system (CNS) to peripheral organs.
What are the two main branches of the autonomic nervous system?
The two main branches of the autonomic nervous system are the sympathetic nervous system and the parasympathetic nervous system.
What functions does the ANS control?
The ANS innervates various cell types and regulates important functions such as heart rate, blood vessel contraction, glandular secretions, and smooth muscle contraction or relaxation in organs like the intestines and bladder.
How does the sympathetic nervous system affect the body?
The sympathetic nervous system increases heart rate and force, causes vascular smooth muscle contraction, dilates airways, dilates pupils, increases glucose metabolism, and triggers sweating (using acetylcholine in sweat glands).
What are the major effects of the parasympathetic nervous system?
The parasympathetic nervous system decreases heart rate and force, stimulates visceral smooth muscle contraction (in the bladder and gastrointestinal tract), promotes vascular dilation, causes pupil constriction, and increases secretions such as tears and saliva.
What neurotransmitters are released by the sympathetic and parasympathetic systems?
The parasympathetic system primarily releases acetylcholine, while the sympathetic system mainly releases noradrenaline. Notably, the sympathetic system also releases acetylcholine in the sweat glands.
Where are the nerve origins for the parasympathetic and sympathetic systems located?
The parasympathetic nerves originate in the cranial and sacral areas, while the sympathetic nerves originate in the thoracic and lumbar areas of the spinal cord.
What is an autonomic ganglion?
An autonomic ganglion is a cluster of nerve cell bodies, primarily associated with the parasympathetic nervous system.
What role do sino-atrial node cells play in the heart?
Sino-atrial node cells regulate the heart rate by generating electrical impulses that initiate each heartbeat.
How does the ANS affect smooth muscle cells?
The ANS can contract or relax smooth muscle cells in various organs, including blood vessels, airways, intestines, and the bladder, thus influencing functions like blood flow and digestion.
What is the significance of myelination in the autonomic nervous system?
In the parasympathetic system, the first nerve is lightly myelinated, which facilitates faster signal transmission. In contrast, the sympathetic system’s first nerve is mostly unmyelinated, affecting the speed and efficiency of its responses.
How does the sympathetic nervous system prepare the body for stress?
The sympathetic nervous system activates the “fight or flight” response, increasing heart rate, blood flow to muscles, and energy availability, while preparing the body to respond to perceived threats.
What is the effect of parasympathetic stimulation on digestion?
Parasympathetic stimulation enhances digestive processes by promoting visceral smooth muscle contraction and increasing secretions of digestive enzymes and acids.
How does the sympathetic nervous system affect pupil size?
The sympathetic nervous system causes pupil dilation (widening) to allow more light into the eye, which is beneficial in stressful situations.
What is the effect of the parasympathetic system on blood vessels?
The parasympathetic system primarily promotes vascular dilation through the endothelium, leading to increased blood flow in certain areas during restful states.
In what situations would the sympathetic nervous system use acetylcholine?
The sympathetic nervous system uses acetylcholine primarily in sweat glands to stimulate sweating, while other functions typically involve noradrenaline.
What is the relationship between the autonomic nervous system and glandular secretions?
The autonomic nervous system controls glandular secretions by stimulating glands to release substances such as saliva, sweat, gastric acid, insulin, and glucagon, depending on whether the sympathetic or parasympathetic system is activated.
How does the autonomic nervous system influence airway function?
The ANS regulates airway function by relaxing bronchial smooth muscles during sympathetic activation (to increase airflow) and promoting contraction during parasympathetic activation (which can narrow the airways).
What is the primary neurotransmitter involved in the parasympathetic response?
The primary neurotransmitter involved in the parasympathetic response is acetylcholine, which is released at various target organs to elicit responses such as decreased heart rate and increased glandular secretions.
How do the sympathetic and parasympathetic systems work together?
The sympathetic and parasympathetic systems work together to maintain homeostasis by balancing each other’s effects; for example, while the sympathetic system increases heart rate during stress, the parasympathetic system helps to slow it down and promote relaxation afterward.
What neurotransmitter is primarily associated with the sympathetic nervous system, and what receptors does it bind to?
Noradrenaline is primarily associated with the sympathetic nervous system. It binds to adrenoreceptors, specifically beta 1 G protein-coupled receptors, to produce various physiological effects.
How do noradrenaline and adrenaline affect heart function?
Noradrenaline and adrenaline increase the force of contraction (positive inotropy), the rate of contraction (positive chronotropy), and the rate of relaxation (positive lusitropy) of the heart by acting on beta 1 adrenoreceptors.
What role do alpha 1 adrenoreceptors play in the sympathetic nervous system?
Alpha 1 adrenoreceptors mediate vasoconstriction in blood vessels, leading to narrowed blood vessels when activated by noradrenaline or circulating adrenaline.
How does the sympathetic nervous system affect visceral smooth muscles?
The sympathetic nervous system can relax many types of visceral smooth muscles, allowing for decreased activity in organs such as the intestines and bladder, which is important during stress or “fight or flight” responses.
What is the primary effect of acetylcholine in the parasympathetic nervous system?
Acetylcholine, released from parasympathetic nerves, binds to muscarinic receptors (specifically M3 G protein-coupled receptors) to produce effects such as decreased heart rate, increased glandular secretions, and smooth muscle contraction.
How does the sympathetic nervous system uniquely innervate arterial smooth muscle?
The sympathetic nervous system innervates arterial smooth muscle in a distinctive pattern described as “bunch of grapes,” allowing for precise control over vascular responses.
What effects do noradrenaline and adrenaline have on blood vessels?
Noradrenaline and adrenaline activate alpha 1 adrenoreceptors in smooth muscle, leading to vasoconstriction (narrowing) of blood vessels, which helps redirect blood flow during stress.
What are the physiological effects of sympathetic activation on heart rate and force?
Sympathetic activation increases both the rate and force of heart contractions, enhancing cardiac output to support the body during stressful situations.
What type of receptors do noradrenaline bind to in the heart?
Noradrenaline binds to beta 1 adrenoreceptors in the heart, which mediate its effects on cardiac function.
What is positive inotropy, and how is it affected by the sympathetic nervous system?
Positive inotropy refers to an increase in the force of cardiac muscle contraction. The sympathetic nervous system enhances positive inotropy through the action of noradrenaline on beta 1 adrenoreceptors.
Describe the effects of sympathetic stimulation on the respiratory system.
Sympathetic stimulation relaxes bronchial smooth muscles, leading to airway dilation, which allows for increased airflow during stress.
What are the effects of the parasympathetic nervous system on the gastrointestinal (GI) tract?
The parasympathetic nervous system promotes increased smooth muscle contraction in the GI tract, enhancing digestive processes and secretion of digestive enzymes.
How does the sympathetic nervous system influence metabolic activity?
The sympathetic nervous system increases metabolic activity by promoting the release of glucose, providing additional energy during stressful situations.
What is the role of muscarinic receptors in the parasympathetic response?
Muscarinic receptors, specifically M3 G protein-coupled receptors, mediate the effects of acetylcholine in the parasympathetic response, leading to actions like increased glandular secretions and smooth muscle contraction.
How does the sympathetic nervous system affect blood vessel tone?
The sympathetic nervous system increases vascular tone by inducing vasoconstriction via activation of alpha 1 adrenoreceptors, thereby regulating blood flow and pressure.
What is the physiological significance of pupil dilation during sympathetic activation?
Pupil dilation during sympathetic activation allows more light to enter the eye, improving vision in low-light conditions and preparing the body for potential threats.
What is the impact of parasympathetic activation on heart rate?
arasympathetic activation decreases heart rate by promoting the effects of acetylcholine on the heart, counteracting the effects of the sympathetic nervous system.
In what ways do the sympathetic and parasympathetic systems complement each other?
The sympathetic and parasympathetic systems complement each other by balancing responses: the sympathetic system prepares the body for action (e.g., increasing heart rate), while the parasympathetic system promotes rest and recovery (e.g., slowing heart rate).
How does the sympathetic nervous system contribute to sweating?
The sympathetic nervous system stimulates sweating through the release of acetylcholine from sympathetic nerves specifically innervating sweat glands, which helps regulate body temperature.
What are the consequences of an overactive sympathetic nervous system?
An overactive sympathetic nervous system can lead to symptoms such as increased heart rate, elevated blood pressure, anxiety, and digestive issues, as it may continuously stimulate “fight or flight” responses.
