Dr. Shaikh Mujeeb Ahmed Assistant Professor AlMaarefa College BRAIN STEM FUNCTIONS CNS BLOCK 424 Dr. Shaikh Mujeeb Ahmed Assistant Professor AlMaarefa College

Objectives Describe the components of Brain stem. Enumerate different functions of brainstem. Explain the clinical conditions which can affect the brainstem function.

Brain Stem Critical connecting link between spinal cord and higher brain regions Oldest region of the brain Continuous with spinal cord All incoming and outgoing fibers traversing between periphery and higher brain centers must pass Brain Stem Consists of Medulla Pons Midbrain

BRAINSTEM Most of the cranial nerves come from the brainstem. The brainstem is the pathway for all fiber tracts passing up and down from peripheral nerves and spinal cord to the highest parts of the brain.

Cranial Nerves

Cranial Nerves No. Cranial Nerve Major Functions I Olfactory smell II Optic vision  III Oculomotor eyelid and eyeball movement IV Trochlear innervates superior oblique turns eye downward and laterally  V Trigeminal chewing  face & mouth touch & pain VI Abducens turns eye laterally  VII Facial controls most facial expressions  secretion of tears & saliva taste 

Cranial Nerves No. Cranial Nerve Major Functions VIII Vestibulocochlear (auditory)  hearing  equilibrium sensation  IX Glossopharyngeal taste  senses carotid blood pressure  X Vagus senses aortic blood pressure  slows heart rate  stimulates digestive organs taste  XI Spinal Accessory controls trapezius & sternocleidomastoid controls swallowing movements XII XII Hypoglossal controls tongue movements 

The brainstem controls several important functions of the body including: Alertness Arousal Breathing Blood Pressure Digestion Heart Rate Other Autonomic Functions Relays Information Between the Peripheral Nerves and Spinal Cord to the Upper Parts of the Brain

MID BRAIN Visual reflex center Auditory reflex center eye movement, and body movement.

Pons It is involved in motor control and sensory analysis... for example, information from the ear first enters the brain in the pons. It has parts that are important for the level of consciousness and for sleep. Some structures within the pons are linked to the cerebellum, thus are involved in movement and posture. 

Pons The pons is a bridge-like structure which links different parts of the brain and serves as a relay station from the medulla to the higher cortical structures of the brain. It contains the respiratory center.

Medulla Oblongata The medulla oblongata functions primarily as a relay station for the crossing of motor tracts between the spinal cord and the brain. It also contains the respiratory, vasomotor and cardiac centers, as well as many mechanisms for controlling reflex activities such as coughing, gagging, swallowing and vomiting.

Respiratory Centers of the Brain Found in 3 pairs of basal nuclei in medulla and pons Medulla contains respiratory rhythmicity centers Set pace for respiration Pons adjusts rate and depth in response to sensory stimuli, emotions, speech Control both voluntary and involuntary Involuntary center in brain controls: Respiratory muscles Respiratory rate 12-18 breaths/min (normal adult) Respiratory depth

Respiratory Centers Dorsal respiratory group (DRG) Contains inspiratory center Functions in every respiratory cycle Ventral respiratory group (VRG) Contains expiratory center Used only during forced breathing Pneumotaxic center in pons, play a role in switching between inspiration and expiration Apneustic center in pons, promotes inspiration by stimulating the inspiratory neurons in the medulla.

Reflex Control of Respiration Normal breathing automatic Activities of respiratory centers modified by sensory information from mechanoreceptors Stretch receptors Pressure (baro)receptors Chemoreceptors Information from the receptors alter pattern of respiration

Respiratory Center

Respiratory center

Chemoreceptor Reflexes Respond to chemical changes in blood, CSF Centers: Carotid bodies and aortic bodies Sensitive to pH, PCO2, PO2 in arterial blood Medulla Sensitive to pH and PCO2 in CSF Stimulation Stimulation: increase in depth and rate of respiration

Chemoreceptor Reflexes Much more sensitive to changes in PCO2 than PO2 Due to small increase in PCO2 stimulates receptors (regulates under normal conditions) PO2 generally does not decline enough to stimulate receptor Cannot hold your breath

VASOMOTOR CENTER

VASOMOTOR CENTER

THE DEGLUTITION CENTER The deglutition (swallowing) center are areas in the medulla and pons that respond to the incoming impulses by sending motor signals back to the pharynx and the upper esophagus (swallowing reflex). These motor impulses travel via the cranial nerves (V, IX, X, XII) and a few superior cervical nerves.

The Reticular Formation it can influence the heart rate, respiration, posture and equilibrium. The so-called reticular activating system plays a critical role in sustaining consciousness. It regulates sleep and wakefulness. The mechanism that triggers REM sleep is located in the pontine reticular formation.

Summary Functions Most of cranial nerves arise from brain stem Neuronal clusters within brain stem control heart and blood vessel function, respiration, and many digestive functions Plays role in regulating muscle reflexes involved in equilibrium and posture Reticular formation within brain stem receives and integrates all incoming sensory synaptic input Centers that govern sleep are in brain stem (evidence suggests center promoting slow-wave sleep lies in hypothalamus)