Flashcards in Lecture 2 - ANS Deck (63):
Briefly state the 7 steps of synaptic transmission:
1.pre-synaptic membrane depolarizes due to AP
2. NT's packed in vesicles and docked at pre-synaptic v.
3. Voltage gated CA channels open w/depolarization, calcium enters pre-synaptic t.
4. increase in calcium --> fusion of vesicle with pre-synaptic membrane
5. NT released into synaptic cleft
6. NT bind to recepts in post-syn membrane
7. Post-synaptic receptors activated and trigger event
After Ca enters the pre-synaptic terminal, what occurs?
Vesicles containing NT's released into cleft
What binds the vesicles to the membrane?
Botulinum toxins and Tetanus cut what proteins and prevent the binding of the vesicle?
- prevent synaptic vesicle fusion & NT release
What kind of paralysis does Botulinum cause? Tetanus?
1. Flaccid Paralysis
2. Spastic Paralysis
Botulinum toxin affects what fibers?
TetX is taken up by inhibitory neurons where? Causing what?
- SPASTIC paralysis
NT's released from vesicles bind what kind of receptors when propagating an electrical signal?
- AChR, GABA
- allow ion influx --> Post-synaptic current = PSC
What is PSC? PSP?
Post Synaptic Current
Post Synaptic Potential
Ionototropic receptors allow ion influx leading to what 2 events?
PSC & PSP
Is the release of NT from vesicles an AP?
- it is a PSP
- graded response propagated passively
How can one get an AP from a PSP?
integration of signals
EPSP's cause what changes in the membrane? Are these AP's? What do they increase the probability of?
1. MEMBRANE DEPOLARIZATION
- influx of cautious bring membrane to zero
2. NOT APs!!! but can generate AP if strong enough
3. increase probability of AP firing
What are some inhibitory NT's? What influx do they cause?
1. GABA, Glycine
2. Influx of Cl- (IPSC)
What two events can IPSP cause? Do ESPS do the same?
1. membrane depolarization & hyper polarization
ESPS's do NOT cause hyper polarization
Which of the two stabilizes the Em at negative potential?IPSP or EPSP?
- reduce probability of AP firing
- away from AP threshold (graph is upside down)
Synaptic integration, or the effect of EPSP's and IPSP's depends on what?
Location at the neuron
Two AP's happening a the same time in different locations are called:
Sequence of AP's in the same place, close in time are called:
What are the 2 main functions of ANS?
2. Respond to external stimuli
(light, external threat --> FIGHT OR FLIGHT)
In the ANS, what controls cardiac muscle, smooth muscle & glands? What modulates organ activity and are accompanied by visceral afferents?
- EFFERENT FIBERS (motor fibers)
What are the 8 main Autonomic NT's?
1. Acethylcholine (ACh),
2. Norepinephrine (NE).
Epinephrine is a central neurotransmitter, but in the ANS its
function is mainly hormonal.
What type of post-synaptic receptor does Neuron-Viscera use?
- neuron to neuron 7 neuron to SkM both use INOTROPIC (fast)
What type of NT effect does Neuron-Viscera have?
(the other two are direct)
Which type of muscle has adventitial (outermost) perivascular varicose nerves? (around a blood vessel)
VASCULAR SMOOTH MUSCLE
- visceral smooth muscle has them all throughout
- VASCULAR ONLY AT THE TOP!!! uses coupled cells
What is the only place using NMJ?
Neuron- Skeletal Muscle
Which of the two: vascular or visceral, contains connections and highly interconnected neurons?
- ex: better coordination of heart contraction
VASCULAR has coupled cells but NOT interconnected (synapses are found on top)
Cardiac myocytes have what type of synapses?
- junctions appear partway along an axon as it extends
Describe the following for NE:
1. Where made
3. Location of degrading enzymes
1. in Vesicles, from DOPA
2. interact with adrenergic receptors
- NE action terminated by re-uptake into cytosol & degradation (MAO, COMT)
3. Cytosol, mitochondria, circulation
Describe the following for Cholinergic transmission:
1. Where made
3. Location of degrading enzymes
1. CYTOSOL from choline (transported by vesicles)
- rich in egg yolks, liver, soy beans
2. inactivated by HYDROLYSIS via acetyl cholinesterase (AChE)
3. Re-uptake into the PRESYNAPTIC TERMINAL for reuse
WMD's like sarin gas inhibit what?
- thus cannot degrade acetylcholine
- OVERSTIMULATION causes convulsion, paralysis, respiratory failure
What are the current treatments of WMD's?
1. Diazepam (sedative against seizures)
2. Atropine - block muscarinic AChR's
3. Pralidozinme - recover AChE function!!!
What is a limitation of WMD antidotes?
DO not enter brain well, do not offer long-term protection
What are the functions of the following WMD treatments?:
1. Diazepam (benzodiazepine) - sedative to prevent seizures
2. Atropine - block muscarinic AChR's
3. Pralidoxime - recover AChE function!!!
What is the term for the resting level of activity that permits both increases and decreases in ANS?
What type of innervation do target organs in ANS receive?
- sympathetic & parasympathetic (reciprocal)
All pre-ganglionic ANS neurons secrete what?
- acts on Nicotinic Receptors
(ionotropic, fast acting)
DO parasympathetic or sympathetic branch have the following:
1. located far from target organ
2. Short Pre-ganglionic fibers
3. located in C8, Thoracic and lumbar segments
4. Have ipsilateral ganglia control (same side)
- except intestine & pelvic viscera = bilateral!
short arms, long fingers
(short pre-ganglionic, long post-ganglionics)
What are paravertebral ganglia and what are prevertebral?
Paravertebral = in Sympathetic Chain
Pre-vertebral = abdominal cavity
Where does the Sympathetic Chain located?
Cervical to COccygeal
What 3 Paravertebral Ganglia are fused together? What levels do they cover?
1. superior cervical ganglion (C1 to C4) controls the head and neck;
2. middle cervical ganglion (C5 and C6)
3. stellate ganglion (C7, C8 and T1), control the heart, lungs and bronchii.
Pre-ganglionic sympathetic axons exit the Sympathetic chain where? Post-ganglionic conduit to spinal nerves travels to the target organs through what?
1. WHITE COMMUNICATING RAMUS
- enter the PARAVERTEBRAL GANGLION at same SC level usually
2. GRAY RAMUS
Splanchnic nerves synapse at paravertebral or pre-vertebral ganglia?
What do sympathetic post-ganglionic fibers secrete? Parasympathetic?
What type of receptors do sympathetic post-ganglionic fibers activate?
METABOTROPIC receptors (alpha beta)
in target organs
What are 2 exceptions of the sympathetic branch?
1. Adrenal Medulla
2. Sweat glands
Where do pre-ganglionic axons traveling to the adrenal medulla synapse? What is released directly into the blood stream?
DIRECTLY synapse with medulla
- no post-ganglionic neuron
NE & Epinephrine directly released into blood stream
(80% of E and 20% of NE released by adrenal medulla)
Why are sweat glands an exception of the sympathetic branch?
- innervated by sympathetic branch BUT activated by ACETYLCHOLINE
- binds to muscarinic *metabotropic receptors
Where are parasympathetic preganglionics located?
1. Brainstem (cranial nerves)
2. S3 and S4 sacral divisions of SC
- 3,5,7,9 have parasympathetic pre-ganglionic somas
GANGLIA CLOSE TO TARGET ORGAN
What d post-ganglionic parasympathetic fibers secrete? What Receptors do they activate?
2. Muscarinic Cholinergic
(sweat glands are exception because they act like parasym. but part of sympathetic system)
Why is the adrenal medulla an exception in the sympathetic branch?
Pre-ganglionic cholinergic activation releases NT's DIRECTLY into blood stream
= no post-ganglionics
What post -ganglionic fibers activate Adrenergic adrenergic receptors? Nicotinic (inotropic) cholinergic receptors?
1. SYMPATHETIC = slow
2. Parasympathetic= fast
What type of post ganglionic receptor agonist do sympathetic and parasympathetic systems use?
What type of receptor type at target organ do each use?
1. both use Nicotinic receptors (fast, ionotropic) for post-ganglionic cells
2. AT TARGET ORGAN:
Sympathetic - activate Adrenergic receptors
Parasympathetic - activate Muscarinic Receptors
( both slow and metabotropic)
How is homeostasis achieved in ANS?
1. Sensory afferent fibers - from perchery to SC & CNS
2. Pain receptors can be activated: distention, ischemia, obstruction
3. Pain signals travel through SYMPATHETIC nerves to SC
- TRIGGER REFLEX ARCS
What post-ganglionic fibers use NE as a NT? ACh?
Reflexes involved in baroreceptors for example use parasympathetic or sympathetic autonomics?
What NT do AFFERENT fibers use?
-used by Visceral Afferents (parasympathetic)
WHat 2 cranial nerves control BP?
9 and 10
What are the steps to decrease blood pressure?
1. Increase in BP sensed by stretching of carotid artery and Aorta - activate MECHANORECEPTORS
2.Afferent fibers of 9 and 10 end in vasomotor and cardioregulator centers of MEDULLA in brainstem
3. Increase Parasympathetic stimulation = decrease heart rate
4. Decrease Sympathetic = decrease Heart rate& contraction
5. Blood pressure back to normal
(due to vasodilation and decreased heart rate)
During increased BP, what occurs in the sympathetic system?
1. decreased input to heart (rate and contraction reduced)
2. decreased input to vascular smooth muscle = relaxation
3. Decreased input to adrenal chromaffin cells = decreased epinephrine and NE secretion to the blood stream
What are the main autonomic centers in the brain?
What are the following autonomic systems responsible for?
1. Micturition (urination), respiratory control
2. Vasomotor & vasodilator, respiratory control, water intake
3. temp reg, water intake, fight/flee, reproduction = hypothalamus
- cortex, amygdala, and stria terminalis also responsible