13-1 Brain and Cranial Nerves Chapter 13

13-2 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

13-3 Development of Brain Segments and Ventricles

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13-5 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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13-7 Brainstem Connects spinal cord to brain Parts –Medulla oblongata –Pons –Midbrain

13-8 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

13-9 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

13-10 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.

13-11 Brainstem and Diencephalon

13-12 Cerebellum Involved in control of: balance, posture, locomotion, and fine motor coordination producing smooth flowing movements

13-13 Diencephalon Components –Thalamus, Subthalamus, Epithalamus, Hypothalamus

13-14 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

13-15 Cerebrum Functions: sensation, perception, voluntary movement, learning, speech and cognition. Divisions –Right –Left Lobes: Frontal, parietal, occipital, temporal, insula Cortex: Outer surface Medulla: Center

13-16 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.

13-17 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

13-18 Limbic System Basic survival functions such as: Memory Reproduction Nutrition Emotions

13-19 Meninges Connective tissue membranes –Dura mater: Superficial –Arachnoid mater –Pia mater: Bound tightly to brain –Spaces Subdural: Serous fluid Subarachnoid: CSF

13-20 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

13-21 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

13-22 Flow of CSF

13-23 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

13-24 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)

13-25 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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