Nervous System X Flashcards
What systems maintain homeostasis?
Autonomic nervous system works closely with endocrine system and behavioural systems
What initiates autonomic, endocrine, and behavioural responses?
Hypothalamus, pons, and medulla
What do autonomic pathways consist of?
Two neurons, preganglionic neuron and postganglionic neurons (both efferent), outside CNS that synapse in an autonomic ganglion
What is divergence in autonomic pathways?
1 preganglionic neuron will synapse with 8 or 9 postganglionic neurons
Where do sympathetic branches originate?
- ganglia found in two ganglion chains running along side vertebral column (paravertebral)
- preganglionic: thoracic and lumbar regions
- short preganglionic, long postganglionic
Where do parasympathetic branches originate?
- ganglia located on or near target organs
- preganglionic: in brainstem and exit via cranial nerves OR from sacral region of spinal cord
- long preganglionic, short postganglionic
What contains 75% of all parasympathetic neurons?
Cranial nerve X (vagus)
What do all preganglionic neurons contain?
Acetylcholine
Soma of postganglionic has nicotine ACh receptors
What chemical signals do sympathetic pathways use?
Acetylcholine and norepinephrine
- postganglionic releases norepinephrine to target tissue with adrenergic receptors
What chemical signals parasympathetic pathways use?
Acetylcholine
- released from preganglionic to postganglionic to target tissues with muscarinic receptor
What kind of receptors are nicotinic
Ionotropic
Ligand gated ion channels
What kind of receptors are adrenergic and muscarinic
Metabotropic
What are exceptions for sympathetic and parasympathetic neurons?
- some sympathetic are choligernic (ACh)
- some autonomic are non-adrenergic and non-cholinergic
What does the adrenal medulla secrete?
Catecholamines
What is a second pathway for the sympathetic NS
Adrenal medulla
Preganglionic go to adrenal gland to medulla to synapse on chromaffin cells and release epinephrine instance of synapsing on postganglionic
What is the adrenal medulla
Specialized neuroendocrine structure associated with sympathetic NS
- modified sympathetic ganglion
- contain chromaffin cells (modified postganglionic neurons)
What are 2 regions of adrenal medulla
Adrenal cortex (true endocrine gland, epithelial origin)
Adrenal medulla is modified sympathetic region (neuroendocrine tissue)
What does chromaffin cell release
Epinephrine is released to blood to bind adrenergic receptors
What is the neuron synapsing with target tissue called
Neuroeffector junction
What do autonomic varicosities do?
Release neurotransmitter over surface of target cell to diffuse to receptors
What can be synthesized in varicosities and recycled?
Primary neurotransmitter, acetylcholine and norepinephrine
What enzyme breaks down NE in the varicosities?
Monoamine oxidase
What enzyme breaks acetylcholine into choline and acetylcholine CoA
Acetylcholinesterase
Where does choline go after ACh is broken down
Transported back into axon terminal by cotransport with Na
Recycled choline used to make more ACh
Why are some sympathetic and parasympathetic inhibitory or excitatory
Due to multiple receptor types
What kind of receptors are sympathetic adrenergic (NE and E)
G-protein coupled (metabotropic receptors)
What are two categories of adrenergic receptors
2 alpha (most common)
3 beta
Have preference for NE or E
What kind of receptors are parasympathetic cholinergic (ACh)
G-protein coupled receptors (muscarinic)
How many subtypes of choligernic receptors
5 subtypes M1-M5
3 in body
What is first possible pathways of g-protein coupled receptors
Interaction with ion channels
- lead to opening or closing of channel depending on g-protein
What is second pathway of g-protein receptors
Interaction with membrane bound enzyme
What is first type of membrane bound enzyme
Phospholipase C signal transduction pathway
- increase in intracellular Ca mediates cellular response
- PKC also mediates
What is second type of interaction with membrane bound enzyme
Adenylyl Cyclase signal transduction pathway
- protein kinase A phosphorylation proteins to cause cellular response
