ANS and Glucose Metabolism (9/26b) [Biomedical Sciences 1] Flashcards
Central Autonomic Network - Afferent information (sensory input)
Cerebral cortex
Cingulate cortex and Amygdala
- important in limbic system, regulates emotions
Basal forebrain
- helps with general arousal
Midbrain- Nucleus of tractus solitarius, periaqueductal grey matter
- gets info about BP, blood pH
Spinal cord
Hippocampus
- helps process memories
Retina
Central Autonomic Network - Efferent Information
Cingulate cortex and Amygdala
Basal forebrain
Midbrain- Dorsal motor nucleus of vagus, periaqueductal grey matter
Hippocampus
Spinal cord
Hypothalamus and hypothalamic nuclei
Hypothalamus - regulates multiple systems (memory, limbic, conscious control, decision making, emotions)
Hypothalamic Nuclei - helps take in afferent information and process them into efferent responses
How does the CV system help perfusion?
Blood pressure
Cardiac output
- Heart rate → SA node
- Stroke volume
What is the role of the cardiovascular and respiratory systems?
Maintain oxygen supply to vital organs by
- maintaining oxygen saturation in blood
- maintaining perfusion to organs
Control of Blood pressure
PROCESS: Afferent pathways (input)→ integration/processing→ efferent pathways (output)
Control of cardiac activity - heart rate and stroke volume
Control of peripheral vasculature - peripheral resistance
Activation of sympathetic (ANS efferent) nerves to the heart
Goes to SA node and AV node
Increases heart rate (+ chronotropy)
Increases contractility (+ inotropy)
Increases stroke volume
Increases blood pressure
Activation of parasympathetic (ANS efferent) nerves to the heart
Goes to dorsal motor nucleus of vagus→ parasympathetic ganglia→ SA node and AV node
Decreases heart rate (- chronotropy)
Decreases contractility (- inotropy)
Decreases stroke volume
Decreases blood pressure
Higher autonomic levels of cardiac regulation
Cardiac accelerator center → activates sympathetic system (spinal cord)
Cardiac inhibitory center → activates parasympathetic system (brainstem/medulla)
Efferent Control of Peripheral Vasculature - Basic ANS Control
Sympathetic efferent: secrete NE and E (catecholamines) to cause vasoconstriction
Most blood vessels do NOT have parasympathetic innervation
Efferent Control of Peripheral Vasculature - Higher Control
the activity of the vasomotor center can be enhanced or suppressed
If enhanced: vasoconstriction → increased BP
If suppressed: vasodilation → decreased BP
Afferent Component of Cardiac Reflexes - Overview
Sensory receptors (EX: baroreceptors and chemoreceptors) detect change and impact firing rate
change in firing rate is a signal to ANS to react
Afferent Component of Cardiac Reflexes - Decreased BP
Decreased BP → baroreceptors reduce their firing
Cardiac accelerator center → increased sympathetic, spinal cord→ heart
Cardiac inhibitory center → decreased parasympathetic, brainstem (medulla) → heart
Afferent Component of Cardiac Reflexes - Increased BP
Increased BP → baroreceptors increase their firing
Cardiac accelerator center → decreased sympathetic, spinal cord→ heart
Cardiac inhibitory center → increased parasympathetic, brainstem (medulla) → heart
Afferent Control of Cardiac Function
sympathetic stimulation increases contractility, frequency, conduction velocity, and irritability
Why is it necessary to control body temperature?
Our body has electrical and chemical processes that require certain temperatures for optimal functioning
Autonomic reflexes play an important part
- in health (EX: exercise) and in disease (EX: fever)
Hypothalamus as a thermostat
Conditions cause body temp to increase →
body temp→
thermoreceptors sense temp change →
hypothalamus compares against 98.6 F (set point, normal body temp is 35.6 C - 37.8 C) →
sweat glands secrete sweat and blood vessels dilate →
body temp decreases
Hypothalamus - Warm sensitive neurons
lead to activation of the parasympathetic system→
leading to vasodilation→
activates sweat glands →
dissipation of heat
Hypothalamus - Cold sensitive neurons
leads to activation of the sympathetic system→
leading to vasoconstriction→
minimizes overall heat loss from skin surfaces
Control of Glucose and Energy Balance
Intake of food → output of energy expenditure
Hormonal systems and neural systems decide this balance
Peripheral mechanisms of blood glucose control
Glycogenolysis - breakdown of glycogen into glucose
Gluconeogenesis - formation of glucose from amino acids
Food Intake - Historic View
Controlled by “glucoreceptors” ; arteriovenous comparison
Hypothalamus
- Lateral: Feeding Center
- Medial: Satiety Center
Food Intake - Contemporary View
Energy balance
Arcuate Nucleus
Metabolic Sensing Neurons - some help feeding behavior, some suppress it
No “Centers” in Hypothalamus - instead complex circuitry between hypothalamic nuclei
Orexigenic vs Anorexigenic
Regulates feeding and body weight
Orexigenic = appetite stimulant
- Neuropeptide Y (NPY)
- Agouti-related peptide (AgRP)
Anorexigenic = appetite suppressant
- Proopiomelanocortin (POMC)
4 Hormones Controlling POMC and NPY-AgRP Activity
Leptin
PYY
Ghrelin
Insulin
How the hormones regulate eating behaviors
Leptin and PYY - SUPPRESS feeding behavior
Ghrelin and insulin - ACTIVATE feeding behavior
How glucose drives balance of eating behaviors
Increased glucose levels
- increased POMC firing → satiety
Decreased glucose levels
- increased NPY-AgRP firing → hunger
2 Abnormalities of Glucose and Energy Metabolism
Obesity - progressive metabolic disorder of ENERGY homeostasis
Type 2 Diabetes Mellitus - progressive metabolic disorder of GLUCOSE homeostasis
Impact of exercise on appetite
Acute exercise does not acutely increase appetite
Vigorous exercise may lead to a temporary suppression of appetite
Exercise Effects on the Brain
Upregulation of neurotransmitter activity
Altered cerebral metabolism and cortisol levels
Increases in brain-derived neurotrophic factor (BDNF) - implications on memory
Some studies show exercise training is more effective for fat loss in (men OR women?)
men
Impacts of Exercise Training
improved satiety, weight/fat loss
Increased in fasting plasma PYY & fat loss (conflicting findings about ghrelin)
Does not induce a strong drive to increase food intake
Change in insulin resistance
