Neuroscience Week 5: Autonomic Reflexes and Integration Flashcards
Objectives
“Fight or flight” and “Rest and digest”
are limited
Simple muscle reflex
Examples of Autonomic Reflexes and Disorders
4 listed
Baroreceptor Reflexes: monitoring of blood pressure
monitoring of bp: aortic arch and carotid sinus
Baroreceptors: Carotid Sinus sensory nerves
Baroreceptors: Aortic arch sensory nerves
Baroreceptors: Control center
information integrated in the medulla
Baroreceptor activity
- as blood pressure drops, baroreceptor firing frequency decreases
- as blood pressure rises, baroreceptor firing frequency increases
Baroreceptor Reflex loop
Baroreceptor effector responses: In response to inappropriate decreased blood pressure
Sympathetic response:
- Norepinephrine acting on α1-receptor causing ↑ PLC and β1 causing adenylate cyclase ↑
- also sympathetics through chromaffin cells in the adrenal medulla
Baroreceptor effector responses: In response to inappropriate increased blood pressure
Parasympathetic response:
- Acetylcholine on M2 receptors
- and
- reduced sympathetic activation
to ↓Heart rate and ↓peripheral resistance
Baroreceptor Reflex Summary
Complexities of predicting effects of adrenergic drugs
Baroreceptor Reflex response to Pentolamine
- α1-adrenergic receptor
- baroreceptor reflex response causes strong increases in heart rate and cardiac output
- (activate strong sympathetic to vasculature activation but it won’t do anything because it is blocked)
but not blocking
- (activate strong sympathetic to the heart β1 and adrenals release epinephrine)
Baroreceptor reflex parasympathetic effectors
Baroreceptor reflex sympathetic effectors
Bladder Filling and Emptying: Reflex contraction of the external sphincter
Spinal reflex with a somatic motor neuron - not autonomics
as the fundus gets more full there are stretch receptors which will then increase the amount of force of contraction of the external sphincter closure
Bladder Filling and Emptying: Bladder Sympathetics
Coordinated Bladder Filling and Emptying:
spinal reflex integrates with (ascending dorsal interneuron pathway) to turn on sympathetic activation of bladder control based on how full the bladder is
Bladder Filling and Emptying: urination control system
parasympathetics
Urinary parasympathetic pathway location and effects
Coordinated Bladder Filling and Emptying: Urination control
- parasympathetics are also connected to the spinal nerve reflex
- the degree of force to expel when full or moderately full is different based on information from the spinal nerve root
Coordinated Bladder Filling and Emptying: Complete
Coordinated Bladder Filling and Emptying: Main control when deciding to urinate name & location
micturation center in the rostral pons
Coordinated Bladder Filling and Emptying: Main control when deciding to urinate mechanism
4 steps
First: ascending input to the micturition center signals bladder distension
Coordinated Bladder Filling and Emptying: Summary
Thermoregulation: Sensors
- Hypothalamus (blood bathing)
- thermosensitive fibers in the trunk sending information to the hypothalamus
Thermoregulation: Heat conservation center effector responses
4 listed
Thermoregulation: Heat conservation center effector responses (Control)
Thermoregulation: Heat loss center effector responses
4 listed
Thermoregulation: Heat loss center effector responses (control)
Sympathetic effectors and receptors
Thermoregulation: Hypothalamus nuclei
Identify and function
Hypothalamus Nuclei for cooling
Anterior hypothalamic area
Hypothalamus Nuclei for heating
Posterior hypothalamic area
Thermoregulation Summary
What happens if anterior hypothalamic nuclei is damaged?
What happens if posterior hypothalamic nuclei is damaged?
What is this
inappropriate spasmodic vasoconstriction
Nifedipine MOA
α1 blocker
What autonomic system is involved here?
too much α1 activation
Raynaud’s disease Clinical Presentation
Raynaud’s disease Treatment
- α1 blocker useful
- Smooth muscle blockers (nifedipine) can also be useful
- Sympathectomy may reduce the frequency and duration of attacks, but usually reserved for very serious cases
Sympathectomy
- not very common but has been done
- takes out a lump of the sympathetic chain
- T1 - T4 ganglia removal
- A few patients developed Horner’s Syndrome
Horner’s Syndrome: Which side is affected?
The side with the
- pseudoptosis
- Miosis
- Enopthalmis
- Anhidrosis
- Dilation of the arterioles of the skin
Horner’s Syndrome: What is the effect of the lesion
Decreased sympathetic and unopposed parasympathetic
Autonomic innervation of the eye
Parasympathetics innervation of the eye
Horner’s Syndrome: Clinical Presentation
ipsilateral to the lesion
What autonomic system can cause inappropriate pupil dilation
too much sympathetics and/or too little parasympathetics
Horners Syndrome: What is the lesion and where is the lesion
Preganglionic or postganglionic
would use a CT to try to figure it out or determine which nerves are affected and where?
Horners Syndrome: Preganglionic common causes?
- Aortic Dissection
- trauma
- carotid dissection
- tuberculosis
- Pancoast tumor
Horners Syndrome: Postganglionic common causes?
- trauma
- cluster headache
- neck or thyroid surgery
Test for Horners Syndrome: in the eye
- if preganglionic is damaged but postganglionic is viable can test with drugs ectopically in the eye then can get a response
- If the postganglionic neuron is damaged then no response to drugs because there is no epinephrine at the target neuron
Integration and reflexes Summary
ALSO, APPLY SIMILAR REASONING TO OTHER ORGAN SYSTEMS
Carotid baroreceptors travel with this nerve
Glosspharyngeal
Aortic arch baroreceptors travel with this nerve
Vagus
Nifedipine Therapeutic use
Raynaud’s Disease
