Physiology Lecture (9) PDF

Physiology Higher control of autonomic functions LECTURE (9) DR. El-Sawy 0  Physiology Higher control of auton...

Physiology Higher control of autonomic functions LECTURE (9) DR. El-Sawy 0  Physiology Higher control of autonomic functions Autonomic functions are integrated within CNS This occurs at different levels. Simple autonomic functions are integrated reflexly e.g.  Primary centers for these reflexes are found in sacral Micturition, defecation & erection segments of spinal cord.  Spinal vasomotor centers (LHCs) : Vascular tone a) Maintain vascular tone b) Integrate some cutaneous vascular reactions. DR. El-Sawy 1  Physiology Higher control of autonomic functions  Vital centers that control: a) Cardiovascular & respiratory functions. b) Gastric secretion & vomiting. Medulla oblongata Pons  Control respiration and salivary secretion.  Control micturition and ocular reflexes i.e. pupillary light reflex and accommodation reflex. Midbrain DR. El-Sawy 2  Physiology Higher control of autonomic functions  It is principal higher center for autonomic nervous system  Considered as the head ganglion of autonomic nervous system.  Hypothalamus regulates various functions 1) Food intake 2) Adrenaline secretion 3) Body temperature Playing an important role in maintaining 4) Body water internal environment constant.  Hypothalamus can affect the activity of almost all the brain stem autonomic centers i.e. a. Stimulation of anterior nuclei of hypothalamus  ↑ parasympathetic functions :  ↓ heart rate, ↓ arterial blood pressure, pupillary constriction  ↑ motility of GIT and micturition b. Stimulation of posterior nuclei of hypothalamus  ↑ sympathetic functions :  ↑ heart rate, ↑ arterial blood pressure, pupillary dilatation  Erection of hair and adrenaline secretion DR. El-Sawy 3  Physiology Higher control of autonomic functions  Certain areas in the cerebral cortex can modify the autonomic functions either directly or through reticular formation e.g. 1- Cardiovascular and gastrointestinal changes :  That occur during psychological disturbances (e.g. acceleration of heart & increased blood pressure). 2- Increased blood flow in the skeletal muscles during exercise. 3- Increased secretion of saliva and gastric juice :  Even on thinking or seeing of food (conditioned reflex). 4- Voluntary control of micturition or defecation. 5- Some conscious control of heart rate & respiratory rate by yoga players. DR. El-Sawy 4  Physiology Higher control of autonomic functions  Group of tracts and nuclei that form a ring (limbus) around Def brain stem.  The limbic system, plus hypothalamus, are concerned with emotions (such as fear, anger, sadness, hunger and memory). Functions  Limbic stimulation produces autonomic effects, particularly changes in arterial blood pressure and respiration in response to emotional reactions. DR. El-Sawy 5