Download Brain and Cranial Nerves

Chapter 13
Brain and Cranial Nerves
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Formation of the Neural Tube
• Brain and spinal cord
develop from the neural
plate under the
influence of the
notochord.
• Neural folds elevate to
form the neural crest
and a neural groove.
• Neural crest cells
become the peripheral
nerves.
• Ventricles and central
canal develop from the
lumen of the neural tube
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Development of Brain Segments
and Ventricles
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Brain and Cranial Nerves
• Brain
– Part of CNS contained in cranial cavity
– Control center for many of body’s functions
• Structures of the Brain
– Brainstem
• Includes the Medulla Oblongata, Pons and Midbrain
– Cerebellum
– Diencephalon
• Includes the Thalamus, Subthalamus, Epithalamus and
Hypothalamus
– Cerebrum and basal nuclei
• Cranial nerves
– Part of PNS arise directly from brain
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Brainstem
• Connects spinal cord to brain
• Parts
– Medulla oblongata
– Pons
– Midbrain
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Brainstem
• Medulla oblongata
– Functions:
• Regulates: Heart rate, blood vessel
diameter, respiration, swallowing,
vomiting, hiccupping, coughing, and
sneezing
• Contains ascending and descending
fiber tracts.
– Pyramids:
• Function: Controls voluntary muscle
movement
• Fiber tracts Decussate at the lower
pyramid
– Olives
• Function: equilbrium, coordination
and modulation of sound in inner ear.
• Contains Nuclei for many cranial
nerves
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Brainstem
• Pons
– Function
• Contains Ascending and
Descending nerve tracks
and Pontine nuclei
• Contains Sleep and
respiratory center
– Pontine Nuclei
• Anterior nuclei: relay
information from cerebrum
to cerebellum
• Posterior Nuclei: Cranial
nerves V – IX.
• Respiratory and Sleep
Nuclei
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Brainstem
• Midbrain
– Contains:
• Cranial nerve nuclei III, IV, V
• Tectum
– Corpora Quadrigemina
» Superior Colliculus – visual reflexes
» Inferior Colliculus – auditory reflexes.
• Tegmentum
– Ascending tracts and Red nucleus
• Cerebral Peduncles
– Major descending motor pathways
• Substantia Nigra
– Muscle tone and movement
• Reticular Formation
– Sleep wake cycle and arousal.
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Brainstem and Diencephalon
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Cerebellum
• Involved in control of:
balance, posture,
locomotion, and fine
motor coordination
producing smooth
flowing movements
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Diencephalon
• Components
– Thalamus, Subthalamus, Epithalamus, Hypothalamus
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Diencephalon
• Thalamus
– Largest part of
diencephalon
– Most sensory input projects
to here
– Influences mood and
actions as fear or rage
• Subthalamus
– Involved in controlling
motor functions
• Epithalamus
– Pineal gland may influence
sleep-wake cycle
• Hypothalamus
– Functions
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ANS control
Endocrine control
Muscle control
Temperature regulation
Regulation of food and
water intake
Emotions
Urine production
Regulation of sleep-wake
cycle
Regulation of reproductive
behavior
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Cerebrum
• Functions: sensation,
perception, voluntary
movement, learning, speech
and cognition.
• Divisions
– Right
– Left
• Lobes: Frontal, parietal,
occipital, temporal, insula
• Cortex: Outer surface
• Medulla: Center
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Basal Nuclei
• Structure:
– Corpus Striatum
• Lentiform Nucleus
(Putamen)
• Caudate Nucleus
– Subthalamic nucleus
– Substantia Nigra
– Motor function control
• Function: Facilitate the
initiation of willed
movements
• Basal Ganglian Disorders
lead to Diskinesias.
– Hypokinesia -paucity of
movement caused by over
inhibition.
– Hyperkinesia -excess
movement.
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•Hypokinesia – Parkinson’s Disease
•Affects 1% of people over 50
•Difficult to initiate willed movements
•Leads to Akinesea, rigidity and tremors of hands and jaw
•Due to degeneration of substantia nigra and dopamine circuits.
•Hyperkinesia- Huntington’s Disease
•Hereditary, progressive and lethal syndrome
•Characterized by: demetia, chorea (uncontrolled movements)
and ballistic movements
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•Due to Damage in the basal nuclei
Limbic System
•Basic survival
functions such as:
• Memory
• Reproduction
• Nutrition
• Emotions
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Meninges
• Connective tissue
membranes
– Dura mater: Superficial
– Arachnoid mater
– Pia mater: Bound
tightly to brain
– Spaces
• Subdural: Serous fluid
• Subarachnoid: CSF
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Ventricles
• Ventricles: Lateral ventricles (2), third ventricle, fourth
ventricle
• Choroid plexuses produce CSF which fills ventricles and
other parts of brain and spinal cord
– Blood-cerebrospinal fluid barrier: Substances do not pass between
cells but through due to tight junctions of blood endothelial cells
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Cerebrospinal Fluid (CSF)
• Similar to serum with most of proteins
removed
• Bathes brain and spinal cord
• Provides a protective cushion around CNS
• Provides some nutrients to CNS tissues
• Produced by ependymal cells
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Flow of CSF
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Brain Blood Supply
• Brain
– Requires tremendous amount of blood
– Receives 15-20% of blood pumped by heart
– Interruption can cause unconsciousness and irreversible
brain damage
– High metabolic rate and dependence on constant supply
of oxygen and glucose
– Receives blood through arteries
• Blood-Brain barrier
– Capillary endothelial cells along with astrocytes and
basement membrane
– To be considered when developing drugs
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Cranial Nerves
• Indicated by Roman
numerals I-XII from
anterior to posterior
• May have one or more of
3 functions
– Sensory (special or general)
– Somatic motor (skeletal
muscles)
– Parasympathetic (regulation
of glands, smooth muscles,
cardiac muscle)
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Cranial Nerves
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Olfactory (I)
Optic (II)
Oculomotor (III)
Trochlear (IV)
Trigeminal (V)
Abducens (VI)
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Facial (VII)
Vestibulocochlear (VIII)
Glossopharyngeal (IX)
Vagus (X)
Accessory (XI)
Hypoglossal (XII)
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