Exam #1: Physiology of the ANS III Flashcards
What is a homotropic interaction? What is the typical effect of a homotrophic interaction?
When the neurotransmitter, by binding to presynaptic autoreceptors, affects the nerve terminals from which it is being released.
- Typically this interaction leads to an autoinhibitory effect
To achieve an inhibitory effect in the SNS, what class of receptor must the pre-synaptic autoreceptor be? What about for the PNS?
Sympathetic= alpha-2 PNS= M2
What is alpha-methyl DOPA? What is the mechanism of action?
An anti-hypertensive drug that targets alpha-2 autoreceptors in the SNS, leading to a decrease in the amount of NE released from the nerve terminal & consequently, lower blood pressure.
What is a heterotrophic interaction?
One neurotransmitter affects the release of another neurotransmitter, via stimulation of a “heteroreceptor”
Heteroreceptor= presynaptic receptors whose ligand is not the same as the neurotransmitter released by that nerve terminal
What is denervation supersensitivity?
- Also called withdrawal rebound hyperactivity & disuse hyperactivity
- If a nerve is cut & its terminal degenerate, the structure supplied by that nerve becomes super-sensitive to the neurotransmitter released by the terminals
What is the mechanism of denervation supersensitivity?
- Proliferation of receptors
- Loss of mechanism for removal of transmitter
- Increased postjunctional responsiveness
What is a clinical correlation of denervation supersensitivity?
Rebound hypertension seen following the abrupt cessation of adrenoceptor blockers
E.g. abrupt beta-blocker cessation can lead to potentially dangerous rebound hypertension
What is cotransmission?
Neurons release multiple neurotransmitters, each of which interacts with specific receptors & produces effects both pre & post-synaptically
What are the main functions of the ANS?
- Assist the body in maintaining constant internal environment i.e homeostasis
- Accommodate coordinated responses to external stimuli e.g. fight or flight
What is the ergotropphic effect?
- Flight or fight
- All the responses of the sympathetic nervous system combined
List the ergotropic effects.
- Heart rate & BP increase
- Bronchioles dilate
- Intestinal motility & secretion are inhibited
- Glucose metabolism increases
- Pupils dilate
- Hairs become erect
- Cutaneous & splanchnic (organ) BV constrict
- Skeletal muscle BV dilate
What is the Trophotropic effect?
- Rest & Digest
- All of the effects to parasympathetic activation combined
List all of the Trophotrophic effects.
- Pupil constriction
- Decrease heart rate & blood pressure
- Bronchiole constriction
- Increased GI tone, secretion, & peristalsis
- Decreased sphincter tone & increased contraction of the detrusor m.
What is the definition of blood pressure (equation)?
- BP= TPR x CO
- CO= HR x SV
Thus, BP= TPR x CO x SV
Blood pressure is the product of Total Peripheral Resistance & Cardiac Output. Cardiac Output is defined as the product of Heart Rate & Stroke Volume.
What is the definition of CO (equation)?
HR x SV
