Nervous System
Physiology
By
Dr. SHAHAB SHAIKH
PhD MD MBBS
Lecture – 7: Brainstem
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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.
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Brainstem
Brain Stem consists of
1. Mid brain
2. Pons
3. Medulla
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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
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Functions of Brainstem
• Origin of majority (10) of cranial nerves is in
Brainstem
• Cranial nerves arising from brain stem
– Mid-brain
– Pons
– Medulla
– III, IV
– V, VI, VII, VIII
– 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
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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
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Cranial Nerves
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Cranial Nerves
No.
Cranial Nerve
Major Functions
I
Olfactory
Smell
II
Optic
Vision
III
Oculomotor
Eyelid and Eyeball Movement
Trochlear
Innervates Superior Oblique
Turns Eye Downward and Laterally
V
Trigeminal
Chewing
Face & Mouth Touch & Pain
VI
Abducens
Turns Eye Laterally
Facial
Controls Most Facial Expressions
Secretion Of Tears & Saliva
Taste
IV
VII
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Cranial Nerves
No.
Cranial Nerve
VIII
Vestibulocochlear
(Auditory)
Hearing
Equilibrium Sensation
Glossopharyngeal
Taste
Senses Carotid Blood Pressure
Vagus
Senses Aortic Blood Pressure
Slows Heart Rate
Stimulates Digestive Organs
Taste
XI
Spinal Accessory
Controls Trapezius &
Sternocleidomastoid
Controls Swallowing Movements
XII
Hypoglossal
Controls Tongue Movements
IX
X
Major Functions
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Functions of Brainstem - CVS
• Cardiovascular center (Vasomotor Center)
– It controls Myocardial contractility
– Controls Blood Pressure
– Controls diameter of blood vessels
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Functions of Brainstem - RS
Respiratory centers
• Medulla –
– DRG - Inspiratory and
– VRG – Expiratory center
• Pons –
– Apneustic center
– Pneumotaxic center
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Functions of Brainstem - RAS
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Functions of Brainstem - Summary
•
•
•
•
•
•
•
Alertness
• eye movement, and
body movement.
Arousal
• Relays Information
Sleep/Wakefulness
Between the
Respiratory Center
Peripheral Nerves and
Cardiovascular Center Spinal Cord to the
Digestion center
Upper Parts of the
Tone, Posture &
Brain
Equilibrium
• Cranial Nerves
• Autonomic Functions Brain stem subconsciously controls
• Visual reflex center many life sustaining processes such
as respiration, circulation, and
• Auditory reflex center digestion. These are referred as
vegetative functions
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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
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transplantation.
Brain Death
EEG RECORDING SHOWING WAVES
EEG RECORDING - FLAT
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Brain Death
Once the brain stem has permanently irreversibly stopped functioning, the heart
will eventually stop beating even if a ventilator has been used
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References
• Human physiology by Lauralee Sherwood,
8th edition
• Text Book Of Physiology by Guyton & Hall,
11th edition
THANK YOU
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