L7 Autonomic nervous system Flashcards
What are the two major efferent pathways of the Autonomic Nervous System (ANS)?
Sympathetic and Parasympathetic pathways
The sympathetic pathway is associated with ‘fight or flight’ responses, while the parasympathetic pathway is related to ‘rest and digest’ functions.
What is the main function of the sympathetic pathway?
Fight or flight response
Activated during exercise, excitement, emergency, and embarrassment.
What is the main function of the parasympathetic pathway?
Rest and digest
Activated during digestion, defecation, and diuresis.
How do sympathetic and parasympathetic pathways generally interact?
They have opposing effects but work synergistically (together)
This allows for rapid, precise control of tissue function.
What type of neurons are always cholinergic in the ANS?
Preganglionic neurons
They release acetylcholine (ACh) as their primary neurotransmitter.
What are the target tissue receptors for the sympathetic pathway?
α- and β- adrenergic receptors
These receptors are activated by norepinephrine released from postganglionic neurons.
What type of neurons does the parasympathetic pathway utilize?:
Long, cholinergic preganglionic neurons from brainstem and lumbar spinal cord
Short ,cholinergic postganglionic neurons
The target tissue expresses muscarinic ACh receptors.
What is the role of the vagus nerve in the parasympathetic system?
Carries ~80% of total parasympathetic outflow
The vagus nerve is also responsible for conveying visceral afferents.
Which areas of the Central Nervous System (CNS) regulate ANS output?
Brainstem nuclei and hypothalamus
The brainstem mediates autonomic reflexes, while the hypothalamus integrates various autonomic functions.
True or False: The autonomic nervous system is largely under voluntary control.
False
The ANS operates largely outside of voluntary control.
Fill in the blank: The sympathetic pathway is activated by _______.
exercise, excitement, emergency, embarrassment
The 4 E’s
Fill in the blank: The parasympathetic pathway is activated by _______.
digestion, defecation, and diuresis
3 D’s (para- die)
What type of sensory input takes priority over cortical functions in the ANS?
Visceral afferents
For example, bladder distension can override conscious thought.
What is the primary neurotransmitter released by cholinergic neurons?
Acetylcholine (ACh)
ACh activates nicotinic ACh receptors on the postsynaptic cell.
List the main functions regulated by the hypothalamus in the ANS. (6)
- Feeding
- Thermoregulation
- Circadian Rhythms
- Water Balance
- Sexual drive
- Reproduction
How does the sympathetic pathway differ anatomically from the parasympathetic pathway?
Sympathetic: short preganglionic, long postganglionic; Parasympathetic: long preganglionic, short postganglionic
Sympathetic neurons originate from the thoracic and lumbar spinal cord
Parasympathetic neurons originate from the brainstem and sacral spinal cord.
What does ANS stand for?
Autonomic nervous system
Motor part of the Peripheral Nervous System
What 5 things does the sympathetic stimulation impact?
Heart, blood vessels, lungs, eyes, liver
Heart rate increases, blood vessels becoome constricted, relaxes airway muscles in lungs (increased oxygen intake), pupils dilate (improve vision), stimulate breakdown of glycogen into glucose in liver to provide energy
What is the general organisation of ANS?
Central nervous system (Preganglionic neuron) –> Peripheral ganglion (Postganglionic neuron) —> Target cell
Both sympathetic and parasympathetic pathways have this organisation
What do ACh activate on the post synaptic cell?
Nicotinic ACh receptors (ligand gated - excitatory)
Muscarinic ACh receptors (G protein - excitatory / inhibitory, relates to PNS)
What type of neurons does the sympathetic pathway utilise?
Short, cholinergic preganglionic neurons from the thoracic and lumbar spinal cord
Long, adrenergic postganglionic neurons
What are the target tissue for the parasympathetic system?
Muscarinic ACh receptors
Where are the essential central components of the ANS located?
The brianstem nuclei and the spinal cord
