Autonomic Nervous System Flashcards
Does the autonomic nervous system function inside or outside of our conscious awareness?
Functions outside of our conscious awareness
What are the main functions of the autonomic nervous system?
Makes routine adjustments in our body’s systems
- Regulates body temperature
- Coordinates cardiovascular, respiratory, digestive, excretory, and reproductive functions
Compare the somatic and autonomic nervous systems in terms of types of neurons and what is innervated.
Autonomic nervous system
- Has afferent and efferent neurons
- Efferent axons innervate the visceral organs
Somatic nervous system
- Has afferent and efferent neurons
- Efferent axons innervate the skeletal muscles
- Somatic motor neurons do not involve ganglia
What is the difference between afferent and efferent?
Afferent- Sensory
Efferent- Motor
Where do afferent pathways originate in the autonomic and somatic nervous systems?
Autonomic nervous system
- Afferent pathways originate in visceral sensory receptors
Somatic nervous system
- Afferent pathways originate in the skeletal muscles, joints, and skin
What are the two major subdivisions of the autonomic nervous system?
Sympathetic division and parasympathetic division
What is the purpose of the sympathetic division of the ANS?
Fight or flight
- Also called the thoracolumbar division
- Most active during times of exertion, stress, or emergency
What is the purpose of the parasympathetic division of the ANS?
Rest and digest
- Also called the craniosacral division
- Most active during resting conditions
Which neurotransmitters are secreted at which points. What are the comparative lengths of the preganglionic and postganglionic neurons when comparing sympathetic and parasympathetic pathways.
Sympathetic
o____ ACh O_____________ NE
Parasympathetic
o___________ACh O_____ ACh
For the sympathetic pathway, the preganglionic neuron is short. Acetylcholine is released. The postganglionic neuron is long and norepinephrine is released.
For the parasympathetic pathway, the preganglionic neuron is long. Acetylcholine is released. The postganglionic neuron is short and acetylcholine is released.
What is the other name for the sympathetic division of the ANS?
Thoracolumbar division
What is the other name for the parasympathetic division of the ANS?
Craniosacral division
What is the third division of the autonomic nervous system?
The enteric nervous system (ENS)
Where is the ENS (Enteric) located?
Neurons located in the walls of the digestive tract
- Many visceral reflexes are initiated by the ENS, but receive input from the ANS.
What does the sympathetic division of the ANS consist of?
- Preganglionic neurons between T1 and L2
The ganglionic neurons are in three locations: - Sympathetic chain ganglia
- Collateral ganglia
- Adrenal medulla
Which ganglionic neurons are innervated by postganglionic fibers?
Sympathetic chain ganglia and collateral ganglia
Which ganglionic neuron is not innervated by postganglionic fibers? What does it do instead?
Adrenal medulla. Releases hormones into bloodstream.
What is the purpose of the adrenal medulla?
Releases neurotransmitters
- Epinephrine (E) and norepinephrine (NE)
- Epinephrine is also called adrenaline
- Norepinephrine is also called noradrenaline
The circulating blood distributes these hormones throughout the body
What is the relationship of an adrenal gland to a kidney?
Adrenal glands are located on top of each kidney. They are composed of a cortex (outer portion) and medulla (inner portion). The adrenal medulla is where neurotransmitters are released.
What are the effects of sympathetic stimulation?
Fight or flight
- Increased alertness
- A feeling of energy and euphoria
- Increased cardiovascular activity
- Increased respiratory activity
- Elevation in muscle tone
- Mobilization of energy reserves
What does the parasympathetic division consist of?
- Preganglionic neurons located in the brainstem and in sacral segments of the spinal cord
- Ganglionic neurons located in peripheral ganglia within or adjacent to the target organs
What nerves do preganglionic fibers leave the brain in?
N III
N VII
N IX
N X
Sacral parasympathetic outflow
- Preganglionic fibers form distinct pelvic nerves
What are the effects of parasympathetic stimulation?
- Constriction of the pupils
- Secretion by digestive glands
- Secretion of hormone promoting nutrient absorption
- Increased smooth muscle activity along the digestive tract
- Stimulation and coordination of defecation
- Contraction of the urinary bladder during urination
- Reduction in heart rate and force of contraction
- Constriction of the respiratory passageways
- Sexual arousal
Most vital organs are innervated by both the sympathetic and parasympathetic divisions. What is this known as?
This is known as DUAL INNERVATION.
The two divisions often have opposite, or antagonistic, effects.
