PhD MD MBBS Faculty of Medicine Al Maarefa Colleges of Science & Technology Faculty of Medicine Al Maarefa Colleges of Science & Technology Lecture – 7: Brainstem Nervous System Physiology By Dr. SHAHAB SHAIKH PhD MD MBBS Faculty of Medicine Al Maarefa Colleges of Science & Technology Faculty of Medicine Al Maarefa Colleges of Science & Technology

Objectives Describe the components of Brain stem. Enumerate different functions of brainstem. Know the reticular formation and its activating & inhibiting system Role of brainstem in brain death. 2

Brainstem 3 Brain Stem consists of 1. Mid brain 2. Pons 3. Medulla

Functions of Brainstem The nerve connections of the motor and sensory systems between the main part of the brain to the rest of the body pass through the brainstem. Has role in Regulation of muscle reflexes involved with equilibrium and posture Reception and integration of all synaptic input from spinal cord 4

Functions of Brainstem Origin of majority (10) of cranial nerves is in Brainstem Cranial nerves arising from brain stem –Mid-brain – III, IV –Pons – V, VI, VII, VIII –Medulla – IX, X, XI, XII The brainstem provides the main motor and sensory innervation to the face and neck via the cranial nerves. Note only Cranial nerves I (Olfactory) & II (Optic) do not have any origin from Brainstem 5

Functions of Brainstem It also regulates the central nervous system, and is Important in... –Arousal and Activation of cortex, –Maintaining Consciousness and –Regulating the Sleep cycle. Centers for Cardiovascular, Respiratory, and Digestive control are located in Brainstem Thus basic functions controlled from Brainstem Include … –Heart Rate & Blood Pressure, –Breathing including Cough & Sneezing –Sleep, wakefulness, Consciousness –Digestive activities including swallowing, vomiting –Posture & Equilibrium 6

Cranial Nerves 7

8 No.Cranial NerveMajor Functions IOlfactorySmell IIOpticVision IIIOculomotorEyelid and Eyeball Movement IVTrochlear Innervates Superior Oblique Turns Eye Downward and Laterally VTrigeminal Chewing Face & Mouth Touch & Pain VIAbducensTurns Eye Laterally VIIFacial Controls Most Facial Expressions Secretion Of Tears & Saliva Taste

Cranial Nerves 9 No.Cranial NerveMajor Functions VIII Vestibulocochlear (Auditory) Hearing Equilibrium Sensation IXGlossopharyngeal Taste Senses Carotid Blood Pressure XVagus Senses Aortic Blood Pressure Slows Heart Rate Stimulates Digestive Organs Taste XISpinal Accessory Controls Trapezius & Sternocleidomastoid Controls Swallowing Movements XII HypoglossalControls Tongue Movements

Functions of Brainstem - CVS Cardiovascular center (Vasomotor Center) – It controls Myocardial contractility – Controls Blood Pressure – Controls diameter of blood vessels 10

Respiratory centers Medulla – –DRG - Inspiratory and –VRG – Expiratory center Pons – –Apneustic center –Pneumotaxic center 11 Functions of Brainstem - RS

12 Functions of Brainstem - RAS

Alertness Arousal Sleep/Wakefulness Respiratory Center Cardiovascular Center Digestion center Tone, Posture & Equilibrium Autonomic Functions Visual reflex center Auditory reflex center eye movement, and body movement. Relays Information Between the Peripheral Nerves and Spinal Cord to the Upper Parts of the Brain Cranial Nerves 13 Functions of Brainstem - Summary Brain stem subconsciously controls many life sustaining processes such as respiration, circulation, and digestion. These are referred as vegetative functions

Brain Death As per the ‘Uniform Determination of Death Act’ of USA, “Brain death is complete & irreversible cessation of all Brain (cerebrum & Brainstem) functions including involuntary activity necessary to sustain life”. While in UK, the Royal College of Physicians defines death based on the irreversible loss of brain stem function alone (Brainstem Death). Brain death is used as legal definition of Death in many jurisdictions. It is a different state from biological death. It is often possible to maintain respiratory and circulatory activity if resuscitative measures are started soon 14

Brain Death The determination that comatose patient maintained by artificial respiration and other supportive measure is alive or dead has important medical, legal, and social implications. It is important to distinguish between brain death and states that may be difficult to differentiate from brain death (such as barbiturate overdose, alcohol intoxication, sedative overdose, hypothermia, hypoglycemia, coma, and chronic vegetative states). The continuing function of vital organs in the bodies of those diagnosed brain dead, if mechanical ventilation and other life-support measures are continued, provides optimal opportunities for their transplantation. 15

Brain Death 16 EEG RECORDING SHOWING WAVES EEG RECORDING - FLAT

17 Once the brain stem has permanently irreversibly stopped functioning, the heart will eventually stop beating even if a ventilator has been used Brain Death

References Human physiology by Lauralee Sherwood, 8 th edition Text Book Of Physiology by Guyton & Hall, 11 th edition

19 THANK YOU