Homeostasis Flashcards
What is the bigger risk for thermoregulation: hyperthermia or hypothermia?
hyperthermia
What is the LOCAL mechanism to avoid hyperthermia?
local temp sensors cause release of nitric oxide, which causes vasodilation and thus increases surface blood flow
blood being closer to the surface means it loses heat more readily
What is the response to body temp below 37?
vasoconstriction to reduce surface blood flow
shivering to make heat
What neurotransmitter causes sweating?
It’s ACh released form the postsynaptic sympathetic neuron (unusual)
What neurotransmitter is released to cause vasoconstriciton and decreased surface blood flow?
norepinephrine
What is unusual about thermoregulation in postmenopausal women?
their thermoregulatory zone is extremely narrow so they always feel too hot or too cold
Blood pressur is usually determined by what NT release from what type of nerves?
norepinephrine from sympathetic nerves
What receptors does NE work on to stimulate heart rate and stroke volume?
Which does NE work on to increase peripheral resistance?
beta 1 for heart rate and stroke volume
alpha1 for resistance
How do you decrease blood pressure?
through the vagus nerve you get release of ACh to interact with muscarinis receptors in the heart to slow heart rate
Where are the receptors that recognize an increase in BP?
the stretch receptors in th ecarotid bodies
An increase in carotid bocy stretch will cause an ____ in firing rate in what nerves?
increase in firing rate in CN9 and 10
Where do the glossopharyngeal and vagus nerve bring the BP information?
the NST
What do the NST neurons do in order to increase BP?
they inhibit the rostral ventrolateral medulla, which is a sympathoexcitatory area
this means you get a decrease in sympathetic release of NE, so you don’t get an increase in heart rate, stroke volume, or resistance
this leads to a decrease in BP
What NT will the vagus nerve release directly on the heart to decrease heart rate?
Ach on muscarinic receptors
When BP is low, what is the signalling pathway to increase it?
- carotid body firing decreases (no stretch)
- Decreased firing in CN9 and 10
- Dereased stimulation of the NST
- No inhibition of the rostral ventrolateral medulla
- stimulation of preganglionic sympathetics
- release of NE
- beta 1 - increase stroke volume and HR; alpha1 - increase resistance
- blood pressure increases
What two things are required for inspiration to occur?
- pacemaker to initiate breathing
- contraction of the diaphragm (and external intercostals) to generate pressure differentials
Where is the pacemaker for breathing located?
in the Pre-Boetzinger area of the ventrolateral medulla
Through what nerve does the pacemaker innervate the diaphram?
the phrenic nerve (C3-C5)
What type of nerve is the phrenic nerve? What NT on what receptor?
a somatomotor nerve under conscios control
releases ACh on nicotinic receptors
What are the inputs to the Pre-boetzinger area?
- from the parafacial respinratory center sensing CO2 (actually H+)
more CO2 - increase respiratory rate to get the CO2 out
What happens if you don’t have CO2 receptors in the parafacial nucleus?
you have Ondyne’s curse
you hypoventilate when you sleep and it’s fatal when untreated
A spinal cord transection above what level would require the patient to be on a ventilator?
above C3
their phrenic nerve wouldn’t be able to get the diaphragm to move
What part of urinary control is voluntary?
the external sphincter consists of skeletal muscle under voluntary control
What NT is involved in keeping the external sphincter contracted?
ACh on nicotinic receptors
What branch of the autonomic nervous system is involved with the involuntary control of urination?
parasympathetic nervous system on the internal sphincter and detrusor (wall)
What NT on what receptor is involved in the involuntary control of urination?
ACh on muscarinic receptors
Bladder filling sends afferent signals to what part of the brain, which usually does what?
afferent signals to to the medial prefrontal cortex
the medial prefrontal cortex usually supresses voiding, but when it receives the afferent signals, it turns off that inhibition to encourage urination
WHat brain region is normally supressed by the medial prefrontal cortex to inhibit urination?
pontine micturition center
What does the pontine mictrurition center stimulate?
it activates the sacral cord to stimulate preganglionic parasympathetic nerves to….
release ACh on the muscarinic receptors of the internal sphincter and wall, causing bladder contraction
activate an inhibitory interneuron influencing motoneurons innervating the external urethral sphincter, causing sphincter relaxation
urination
How can you pharmacologically treat the inability to initiate urine flow?
give a muscarinic agonist
