13-1 brain and cranial nerves chapter 13. 13-2 formation of the neural tube brain and spinal cord...
TRANSCRIPT
13-1
Brain and Cranial Nerves
Chapter 13
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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
• 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•Due to Damage in the basal nuclei
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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
• Olfactory (I)• Optic (II)• Oculomotor (III)• Trochlear (IV)• Trigeminal (V)• Abducens (VI)
• Facial (VII)• Vestibulocochlear (VIII)• Glossopharyngeal (IX)• Vagus (X)• Accessory (XI)• Hypoglossal (XII)
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