2.3 Autonomic Nervous System Flashcards
Somatic nervous system
Perceptible and voluntary
Autonomic nervous system
Imperceptible and involuntary
Another term for parasympathetic division
Craniosacral division
Where are the preganglionic neurons located in the parasympathetic division?
Cranial nuclei and sacral region of spinal cord
Function of Parasympathetic nervous system
Digestion and energy storage… rest & digest
Another term for sympathetic division
Thoracocolumbar division
Function of sympathetic division of autonomic nervous system
Energy mobilization and distribution… Fight or flight
Where are the cell bodies of preganglionic neurons located in the sympathetic division?
Thoracic and lumbar regions of the spinal cord
SymNS and ParaNS are…
Mutually inhibitory -Increase in activity in one leads to decrease in activity of the other
What actions does the Parasympathetic division do?
-Activates digestive processes -Promotes nutrient storage (liver, muscle) -Slows heart rate and reduces blood pressure
What actions does the sympathetic division do?
-Mobilizes nutrients (glucose) into bloodstream -Increases cardiac output—-> Increase perfusion of active tissue -Dilates bronchiole tubes–> Increased ventilation -Slows digestion and other non-essential organ systems
The parasympathetic neuron has a ________ preganglionic neuron, and synapses near_______
Long Target organ
The sympathetic neuron has a ________ preganglionic neuron and synapses near_______
Short Spinal column (long postganglionic neuron)
All preganglionic neurons are…
Cholinergic, they release acetylcholine at the synapse
When ACh is released from the preganglionic neuron, it binds….
Post synaptic nicotinic ACh receptors –>Na+ ion channels (fast) –> Always EPSPs
Where does the nicotinic name of the receptor come from?
Their ability to be activated by nicotine
What does the postganglionic fiber in the parasympathetic division release?
Acetylcholine
What does the acetylcholine released from the postganglionic fibers bind to on effector target tissues?
Muscarinic receptors (sustained / slower acting GPCRs)
What does the binding of acetylcholine to muscarinic receptors in the parasympathetic division cause?
EPSPs or IPSPs depending on the tissue
Where do muscarinic receptors get their name?
They bind muscarine compound from poisonous mushrooms
Parasympathetic pathway (entire thing)
- Preganglionic fibers release acetylcholine 2. Acetylcholine binds postsynaptic nicotinic receptors 3. Binding causes influx of Na+ into postganglionic neuron 4. Postganglionic fibers release acetylcholine 5. Acetylcholine binds muscarinic receptors on effector target tissues 6. Causes EPSPs or IPSPs
The majority of post-ganglionic fibers in the sympathetic division release what?
Norepinephrine!
Two pathways for sympathetic division
Acetylcholine–>Acetylcholine Acetylcholine–> Norepinephrine
Sympathetic pathway (most common one)
- Preganglionic fibers release acetylcholine 2. Acetylcholine binds postsynaptic nicotinic receptors 3. Binding causes influx of Na+ and leads to EPSP on postganglionic neuron 4. Adrenergic neurons release norepinephrine 5. Norepinephrine binds adrenergic receptors on target cell (also GCPRs) 6. Cause EPSPs or IPSPs on target tissues (often muscles or glands)
What are target cells of the ACh pathway in the sympathetic nervous system?
Sweat glands, and blood vessels in muscle tissue
What are the target tissues of the norepinephrine pathway in the sympathetic division?
Most other tissues
Varicosites
At axon terminus of postganglionic adrenergic neurons
Enables widepread secretion of NE at synapses throughout the effector organs—> Activates adrenergic receptors that stimulate (inhibit) target tissues
“Showers” cells in norepinephrine
Where / what does preganglionic ACh activate in the sympathetic division?
Adrenal medulla (inner)
Specifically chromaffin cells
NO postganglionic neuron!!
What do chromaffin cells release?
Epinephrine (adrenaline) and norepinephrine as HORMONES which bind adrenergic receptors on tarhet tissues via the bloodstream
Global, body-wide effect that lasts longer than neurotransmitters
What do both epinephrine and norepinephrine both bind?
Alpha and beta adrenergic receptors
What are aplha and beta adrenergic receptors?
G-protein coupled receptors, not ion channels
Can be stimulatory (alpha and beta) or inhibitory (mostly beta)
Effects of both epinephrine and norepinephrine on brain
Alertness
Effects of both epinephrine and norepinephrine on liver
Glucose release
Effects of both epinephrine and norepinephrine on heart
Increased rate / strength of contraction
Other effects of norepinephrine and epinephrine
Bronchiolar dilation, increased diaphragm contraction, reduced digestion, inhibits pain perception
Difference between epinephrine and norepinephrine
Norepinephrine works better as a neurotransmitter and epinephrine is more of a hormone
What are beta blockers?
Bring down blood pressure, a lot of men take them, block beta adrenergic binding site to reduce effects of epinephrine and norepinephrine
Somatic nervous system (system)
1 neuron
Autonomic nervous system (system)
Neurotransmitters, hormones and effectors
Review slide 15!!!!
ANS functions: 3 body scenarios
- Relaxation / sleep
- Vidorous exercise
- Stress response
Relaxation / sleep
- Energy storage and tissue repair
- Parasympathetic division predominates
Vigorous Exercise
- Mobilization and distribution of energy resources
- Sympathetic division predominates
Stress response
- Anticipation of the “fight”
- Sympathetic division and CRH / ACTH / cortisol release
Digestive tract during relaxation / sleep
Increased secretion from salivary glands, gastric glands, exocrine pancreas
Increased motility of GI smooth muscle
Contraction of gall bladder smooth muscle
Increased insulin secretion pancreatic beta cells
Respiratory system during relaxation / sleep
Contraction of bronchial smooth muscle (constricts bronchi)
Cardiovascular system during relaxation / sleep
Decreased MAP (mean arterial pressure)
Decreased cardiac output
Decreased sympathetic outflow –> Relaxation of vascular smooth muscle –> Dilation of blood vessels –> Decreased resistance
–>Decreased MAP
Digestive tract during exercise
Decreased activity
Respiratory system during exercise
Increased ventilation
- Relaxation of bronchial smooth muscle (dilates bronchi)
Cardiovascular system during exercise
Increased MAP and perfusion
-Increased dilation of vascular smooth muscle in active skeletal muscles–> increased local blood flow to active muscles
Adrenal medulla during exercise
Mobilization of energy
- Release of epinephrine
- Glycogen breakdown by muscle and liver
- Fat breakdown in fat cells
Skin during exercise
Heat dissipation during vigorous and prolonged exercise
- Increased core temperature because of increased metabolic activity
- Increased activation of sweat glands (via acetylcholine at muscarinic receptors)
- Increased blood flow to skin (increased core temperature overrides constriction of vascular smooth muscle)
Stress perception in the short term elicited in the
Amygdala–> hypothalamus–>ANS increased sympathetic outflow.. medullary epinephrine and norepinephrine release
Effects of short term stress response
Increased MAP
Decreased GI motility
Increase in sweat secretion
Chronic, long term stress activates…
Adrenocorticotropic axis for more sustained, prolonged response
Hypothalamic control of the chronic stress response
CRH–>ACTH–>Cortisol (released from adrenal CORTEX)
Cortisol
Effects similar to epinephrine, but much more long term
Acute effects of cortisol (the stress hormone)
Good, help performance
- Increased breakdown of fat and protein
- Increased gluconeogenesis in liver
- Increased blood glucose levels –> Feul for performance
Chronic effects of cortisol
Bad, make you sick
Decreased immune functions (immune supression), decreased resistance to disease
Tissue “wasting” due to protein loss
May lead to depression
