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

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

3. 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

6. 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.

7. Cranial Nerves

8. 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 

9. 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 

10. 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

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

12. 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. 

13. 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.

14. 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.

15. 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

16. 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.

17. 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

20. Respiratory Center

21. Respiratory center

22. 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

23. 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

24. VASOMOTOR CENTER

25. VASOMOTOR CENTER

27. 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.

28. 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.

29. 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)