CH18 External Regulation of the Heart

Exam 1 Review: Chapter 18: External Regulation of the Heart

cardiovascular center - A major autonomic nucleus located deep inside the medulla which receives visceral sensory information about blood pressure, blood oxygen levels, blood pH, etc., and integrates this information to regulate the rate of the heartbeat and the level of muscular tension in the blood vessels primarily via sympathetic impulses; it includes the parasympathetic cardioinhibitory center and the sympathetic cardioacceleratory center; peripheral factors such as emotions, ion concentrations, and body temperature may affect heart rate and these are usually mediated through the cardiac center.

cardioacceleratory center - The sympathetic subcomponent of the cardiovascular center in the medulla which received visceral sensory information about blood pressure, blood oxygen levels, blood pH, etc., and integrates this information to increase the rate of the heartbeat and the muscular tension in the blood vessels by sending sympathetic impulses down through the spinal cord to thoracic segments where sympathetic preganglionic neurons reside in the lateral grey horns, the neurons synapse with sympathetic postganglionic neurons which reside in the sympathetic trunk ganglia (mainly on the right chain) and relay the impulses to the sino-atrial node where their neurotransmitter, norepinephrine, directly stimulates the heart to increase cardiac output to support increased muscular activity or fight-or-flight emergencies; this center plays the major role in controlling cardiac output.

cardioinhibitory center - The parasympathetic subcomponent of the cardiovascular center in the medulla which receives visceral sensory information about blood pressure, blood oxygen levels, blood pH, etc., and integrates this information to decrease the rate of the heartbeat and the muscular tension in the blood vessels by sending parasympathetic impulses via parasympathetic preganglionic neurons through the vagus nerve (X), the preganglionic neurons synapse with parasympathetic postganglionic neurons which reside near the sino-atrial node and relay the impulses to the sino-atrial node where their neurotransmitter, acetyl choline, directly stimulates the heart to decrease cardiac output to return the circulatory system to a resting homeostasis after the end of episodes of increased muscular activity or fight-or-flight emergencies; this center plays the more minor role in controlling cardiac output.

proprioceptors - A sensory nerve cell or sense organ which detects the movement, position, location and spatial orientation of the body and its parts arising from stimuli within the body itself; mechanoreceptors responding to stretching of a muscle, tendon, or ligament or responding to the movement of special structures in the inner ear; the mechanism involved in the self-regulation of posture and movement; in the heart, the prioprioceptors are stretch receptors which respond to the overfilling of the atrial and ventricular chambers.

chemoreceptors - A sensory nerve cell or sense organ which responds to chemical stimuli; including exteroreceptors for smell and taste and enteroreceptors sensitive to concentration changes of a variety of molecules in the blood or other body fluids.

baroreceptors - A type of mechanoreceptor; a specialized sensory end organ or sensory neuron which responds to mechanical stimuli such as tension (stretching) in the wall of a blood vessel or other tubular organ; important sensors in the regulation of blood pressure.

cardiac accelerator nerves - The autonomic sympathetic nerves consisting of postganglionic axons which relay impulses, which originated in the sympathetic cardioacceleratory center in the medulla, from the sympathetic chain ganglia (mainly on the right chain) to the sino-atrial node where their neurotransmitter, norepinephrine, directly stimulates the heart to increase cardiac output to support increased muscular activity or fight-or-flight emergencies.

vagus nerve = cranial nerve X - The tenth and longest of the cranial nerves, a pair of mixed (modality) nerves arising from the medulla oblongata and passing through the neck and thorax into the abdomen and supplying sensation to part of the ear, the tongue, the larynx, and the pharynx, somatic motor impulses to the skeletal muscles of the palate, larynx and vocal cords, and visceral sensory and parasympathetic autonomic motor and secretory impulses to the abdominal and thoracic viscera.

List:

8. the extrinsic factors which regulate or can influence the heart rate (HR).

General Categories Specific Examples

Autonomic Nervous System Regulation Sympathetic Division: releases Norepinephrine which increases HR.
Parasympathetic Division: releases acetyl choline which decreases HR.

Endocrine System Regulation Epinephrine = Adrenalin and Thyroid Hormones (T₃ & T₄) increase HR

Electrolytes = Ions Changes in Calcium (Ca⁺⁺) & Potassium (K⁺) concentrations in plasma and interstitial fluid influence HR.

Body Temperature Hypothermia decreases HR while hyperthermia & fever increase HR.

Demographics Increasing age increases HR.
Males tend to have higher HR.

Body Size Characteristics Increased body mass or increased blood volume tend to increase blood pressure and therefore increase HR.

Lifestyle Regular exercise tends to decrease HR; tobacco and alcohol and many types of drug abuse tend to increase blood pressure and therefore increase HR.

Pathology Stress and many illnesses effect HR; stress and most such diseases increase Sympathetic Division activity, releasing Norepinephrine, which increases HR.

General Categories	Specific Examples
Autonomic Nervous System Regulation	Sympathetic Division: releases Norepinephrine which increases HR. Parasympathetic Division: releases acetyl choline which decreases HR.
Endocrine System Regulation	Epinephrine = Adrenalin and Thyroid Hormones (T₃ & T₄) increase HR
Electrolytes = Ions	Changes in Calcium (Ca⁺⁺) & Potassium (K⁺) concentrations in plasma and interstitial fluid influence HR.
Body Temperature	Hypothermia decreases HR while hyperthermia & fever increase HR.
Demographics	Increasing age increases HR. Males tend to have higher HR.
Body Size Characteristics	Increased body mass or increased blood volume tend to increase blood pressure and therefore increase HR.
Lifestyle	Regular exercise tends to decrease HR; tobacco and alcohol and many types of drug abuse tend to increase blood pressure and therefore increase HR.
Pathology	Stress and many illnesses effect HR; stress and most such diseases increase Sympathetic Division activity, releasing Norepinephrine, which increases HR.