9/26b ANS & Neural Control of CVP Function (Biomedical Sciences) Flashcards
Central autonomic network
- systems working in parallel, but controlled by the -central autonomic network.
- Receives input from multiple different brain regions
- function is deduced from its connections
- Receives afferent and efferent information
Afferent information in the central autonomic network
- Cerebral cortex
- Cingulate cortex and Amygdala - regulate emotions, parts of the limbic system, helps regulate your mechanisms that could be influenced by all the different systems
- Basal forebrain - at the base of the forebrain, that helps in general arousal
- Midbrain - nucleus of tractus solitaries (helps get information about the blood pressure or the blood pH), periaqueductal grey matter
- Nucleus of tractus solitaries, periaqueductal grey matter
- Spinal cord
- Hippocampus - part that helps process memories
- Retina
Efferent information in the central autonomic network
Hypothalamic nuclei
- cingulate cortex and amygdala
- basal forebrain
- midbrain
- hippocampus
- spinal cord
Hypothalamus
control/transit center that regulates multiple physiologic, emotional/limbic, memory, conscious control, and decision making systems to essentially help your action
Deficits in the central autonomic nervous system
patient with TBI may be able to do all physical ADLs, but may not be able to come back to their everyday life (mentally)
How does the ANS work?
- Controls BP and HR
- Controls body temperature
- Controls glucose and energy
Role of cardiovascular and respiratory systems?
- maintain oxygen supply to the viral organs, through:
- -maintaining oxygen saturation of the blood
- -maintaining perfusion (blood flow) to the organs
Regulation of BP
-Cardiac Output = stroke volume x HR
-TPR/perfusion
-Maintenance is done through complex reflexes with:
afferent input to processing centers then get an efferent response
Efferent control/supply to the heart
- Sympathetic stimulation
- Parasympathetic stimulaton
- higher autonomic levels of cardiac regulation
- control of peripheral vasculature
what is the effect of efferent sympathetic stimulation on the heart?
- T1-T4 go to heart SA node and AV Node (preganglionic neurons > paravertebral chain > post gang neuron supplies heart)
- Activation of the sympathetic nerves to the heart yields:
- -increases HR (positive chronotropy)
- -increases contractility (positive chronotropy)
- -> thus increasing SV
what does efferent activation of the parasympathetic nerves do to the heart?
- Craniosacral region in the brainstem (medulla - dorsal motor nucleus of vagus) to parasympathetic ganglia (very close to the heart) and then goes to supply the SA node and AV node
- Activation of dorsal nucleus of vagus yields:
- -decrease HR
- -decrease SV
- -decrease BP
Cardiac accelerator center
- sits in the medulla
- facilitates/activates SNS through spinal cord
Cardiac inhibitory center
- sits in the medulla
- activates PNS and calms heart down through brainstem
control of peripheral vasculature
- No PNS innervating the peripheral vasculature, in general (there are a few exceptions)
- If we want to vasoconstrict, increase SNS
- If we want to vasodilate, decrease SNS
afferent control of the heart
sensory receptors:
- baroreceptors
- chemoreceptors
baroreceptors
- sense pressure changes
- in aortic arch and carotid bodies
- relationship between receptor firing rate and MAP (as receptor firing rate increases, BP increases)
chemoreceptors
sense changes in PO2 and PCo2
MAP
mean arterial pressure: 1/3(sbp - dbp) + dbp
change in integrated receptor firing rate means:
they have detected a change in bp that then stimulates the autonomic NS to act based on the change
-basic reflexes for involuntary control
input for aortic arch in afferent control of the heart
from vagus cranial nerve
input for carotid body in afferent control of the heart
glossopharyngeal cranial nerve
cardiac process when blood pressure is decreased
SNS Stim
- BP is decreased
- Baroreceptors reduce firing
3a. Cardiac accelerator center gets triggered
4a. increased SNS activity from spinal cord to blood vessel
5a. blood vessel constriction and increase HR
PNS drop
- BP is decreased
- Baroreceptors reduce firing
3b. cardiac inhibitory center gets triggered
4b. decrease parasympathetic NS in brainstem (medulla)
5b. increase HR
cardiac process when blood pressure is increased
SNS Stim
- BP is increased
- Baroreceptors increase firing
3a. Cardiac accelerator center gets triggered
4a. decreased SNS activity from spinal cord to blood vessel
5a. blood vessel dilation and decrease HR
PNS drop
- BP is increased
- Baroreceptors reduce firing
3b. cardiac inhibitory center gets triggered
4b. increase parasympathetic NS in brainstem (medulla)
5b. decrease HR
why does the ANS part of control of body temperature
the body is an electrochemical system and requires an optimal temperature that is important for the body
ex: fever, exercise, response in cold temperatures
what is the ANS control of body temperature important for?
Health and Disease
What is the overall process of temperature regulation through the ANS?
- Hypothalamus has a set point and controls how heat can be dissipated
- Hypothalamus has temperature sensitive neurons that sense the change in body temperature
- warm sensitive neurons
- cold sensitive neurons
- other temperature insensitive neurons
What is shivering an example of?
activates skeletal muscles to produce heat
Fever’s purpose on temperature regulation
body is unable to get balance back because of certain pathogens, sensitivity to warm sensitive neurons is lost *(pyrogenic factors). Pyrogens change the sensitivity of the warm sensitive neurons so they can’t sense that they need to act
Control of glucose and energy
important for expenditure systems and is dependent on both autonomic system, behavioral and psychosocial aspects
NEUROHUMORAL
Peripheral mechanisms of blood glucose creation
Glycogenolysis - breakdown of glycogen into glucose
Gluconeogenesis - creation of glucose from amino acids
warm sensitive neurons
- leads to activation of PNS that primarily activates sweat glands
- leads to relaxation of SNS that leads to vasodilation activities leading to dissipation of heat
cold sensitive neurons
lead to activation of sympathetic system leading to vasoconstriction minimizing overall heat loss from skin surfaces
other temperature insensitive neurons
play in important supportive role in the hypothalamus
is insulin important in blood glucose?
YES, it has a really complicated and important role
insulin release reduces glucose production
Historic view of food intake
controlled by glucoreceptors (a-v comparison)/glucose was the primary driver
Hypothalamus: lateral feeding center, medial safety center
Current view of food intake
Viewed more as an energy balance
- arcuate nucleus has metabolic sensing neurons
- some of the neurons help feeding behavior and some suppress feeding behavior
- Arcuate nucleus activates on the dorsal vagus nerve and on intermediate lateral thoracic spine (thoracolumbar outflow)
Process of arcuate nucleus stimulation for feeding behaviors
two competing systems that activate on dorsal vagus nerve (increase PNS control for food intake) and on intermediate lateral thoracic spine (IML - Thoracolumbar spine) increasing energy expenditure
- Orexigenic Neurons: neurons that secrete neuropeptide Y (NPY) and agouti-related peptides (AgRP) and INCREASE APPETITE
- Anorexigenic Neurons: Propriomelanocort (POMC) and SUPPRESS APPETITE
what controls NPY-AgRP and POMC?
Hormones act on the NPY and POMC, exact nature is not clearly understood. Think of it as multiple controls on the two groups of neurons
- Leptin: suppress feeding behavior
- Ghrelin: activate feeding behavior
- PYY: suppress feeding behavior
- Insulin: beta cells of pancreas produce insulin
Leptin
- released from adipose tissue
- acts to reduce feeding behavior
- facilitates memory and reduces neurodegeneration
- acts to inhibit obesity
PYY
- secreted from small intestine
- suppresses feeding behavior
Ghrelin
- Increases feeding behavior
- from the stomach
Insulin
- peripheral and central, action depends on what is there
- Beta cells of pancreas produce insulin
- Action peripherally and centrally
- action on the brain is dependent on multiple factors including but not restricted to blood glucose, leptin, levels of insulin, and body weight
abnormalities of glucose and energy metabolism
- obesity: progressive metabolic disorder of energy homeostasis
- type 2 diabetes mellitus: progressive metabolic disorder of glucose homeostasis
what is the problem of producing a leptin drug to sell as an appetite suppressant?
only leptin won’t work because it is just one aspect of the systems.
Glucose is an important driver of this!
Exercise’s influence on the brain and hormones
- acute exercise: exercise does not acutely increase appetite and vigorous exercise may lead to a temporary suppression of appetite
- May be different in men and women
- Exercise effects the brain by improving satiety
Importance of acute exercise
- decrease in acylated ghrelin during an hour after acute aerobic exercise and resistance training
- increase in PYY up to ~5 hrs after acute exercise
reasons why exercise’s influence on the brain varies between men and women?
- Some studies - exercise training more effective for fat loss in men
- Disparities are huge in male and female healthcare research and you have to be careful on how you apply this info to your patients
Exercise effects on the brain
- Exercise – Improves satiety, Weight/Fat loss
- *Increased in fasting plasma PYY & fat loss after 12, 32 wks or 1 year – children, adolescents, adults
- *Conflicting findings about Ghrelin
- Exercise – Does not induce a strong drive to increase food intake
- Exercise – change in insulin resistance – Upregulation of neurotransmitter activity
- altered cerebral metabolism and cortisol levels
- increases in brain-derived neurotrophic factor (BDNF): important role on neuroplasticity and memory
