Autonomic Nervous System Flashcards
(36 cards)
What does the autonomic nervous system innervate
Innervate organs whose functions are not usually under voluntary control
Autonomic means self governed so it is involuntary
Reflexes are important for autonomic control because
May involve sensory info causing changes in autonomic output in order to return to a set point (negative feedback)
May elicit feedforward responses
What are effectors of the autonomic nervous system
Visceral organs and blood vessels
Sensory info of the autonomic nervous system may be processed within …
Hypothalamus
Limbic system
Or even at the spinal cord level
Most visceral effectors do not NEED the ANS to function only to do what?
Example?
Only to adjust their activity to match the body’s needs to maintain homeostasis
Ie) heart rate
What is the general autonomic nerve pathway
Extends from CNS to an innervated organ
Two neuron chain
- preganglionic fibre
- postganglionic fibre
What are pre and post ganglionic fibres
Pre= synapses with cell body of second neuron
Post= innervates effector organ or tissue
What’s a ganglion
Mass or group of neuronal cell bodies knot-like mass of tissue
The sympathetic nervous system cell bodies and axons of preganglionics originate where?
The thoracic and lumbar regions of the spinal cord
Sympathetic nervous system pre and post ganglionic differences
Pre = mostly are short
Post= long
What are the three things axons do after exiting the spinal cord in the sympathetic
1) make a synapse in a sympathetic chain ganglion
2) pass thru SCG and synapse in the Adrenal Medulla
3) pass thru SCG and synapse in a collateral ganglion
What do preganglionic fibres release in the sympathetic
ACh
What do postganglionic fibres release in the sympathetic
NE
Parasympathetic nervous system fibres originate from
Cranial and sacral areas of CNS
What are parasympathetic pre and post ganglionic fibres differences
Pre = are longer
Post = VERY short
What do preganglionic fibres release in the parasympathetic
ACh
What do postganglionic fibres release in the parasympathetic
ACh
Note difference!
Each postganglionic neuron receives synapses from many _____
This means convergence!!
Preganglionics
Nervous system each preganglionic neuron branches many times to synapse on many different postganglionic neurons this called
What’s the ratio of pre:post neurons
Divergence
In SNS
- 1:10 to 1:30
In PNS
- 1:4 (LOWER THEN SNS)
The four cranial nerves that have parasympathetic function are
Oculomotor = controls the lens and pupil of the eye
Facial nerve = tear glands, salivary glands and nasal glands
Glossopharyngeal = salivary glands
Vagus = 70-90% of allPNS fibres and innervates the viscera
What cranial never is the vagus nerve and what organs does it innervate
Known as wandering 10 (many branches)
Innervate all organs except adrenal medulla and some parts of the colon
The vagus nerve is part of a reflex arc what are the 3 steps
1) vagus nerve carries sensory info from most of the viscera. Many of these sensory afferents project topographically to Nucleus of the Solitary Tract (NST or NTS) in the brainstem
2) the sensory info is processed within the NTS
3) vagus nerve carries efferent information to regulate organ function
The SNS tends to have a longer lasting effect the the PNS on target organs because ..
1) ACh quickly broken down by acetylcholinesterase
2) NE more persistent than ACh. Breakdown mechanisms are slower for ACh
- Ne transported back into the neuron
- NE degraded by catechol-O-methyl transferase and monoamine oxidase
- Ne picked up by blood
What are the receptors on target organs for the ANS
SNS (NE)
-a1, a2, b1, b2, b3
PNS (ACh)
- nicotinic AChR
- muscarinic AChR (m1, m2, m3)
