ANS and Glucose Metabolism (9/26b) [Biomedical Sciences 1] Flashcards Preview

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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

- helps process memories



Central Autonomic Network - Efferent Information

Cingulate cortex and Amygdala

Basal forebrain

Midbrain- Dorsal motor nucleus of vagus, periaqueductal grey matter


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

- 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



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