Chapter 14 The Brain and Cranial Nerves 1

2

Brain and Cranial Nerves 3

Brain and Cranial Nerves • Brain – Part of CNS contained in cranial cavity – Control center for many of body’s functions – Much like a complex computer but more • Parts of the brain – – Brainstem Cerebellum Diencephalon Cerebrum • Cranial nerves – Part of PNS arise directly from brain 4

Brainstem • Connects spinal cord to brain • Parts – Medulla oblongata – Pons – Midbrain 5

Brainstem • Medulla oblongata or medulla – Regulates: Heart rate, blood vessel diameter, respiration, swallowing, vomiting, hiccupping, coughing, and sneezing – Pyramids: Decussate • Pons – Sleep and respiratory center • Midbrain – Integral part of auditory pathways in CNS 6

Brainstem and Diencephalon 7

Cerebellum • Involved in control of: balance, posture, locomotion, and fine motor coordination producing smooth flowing movements 8

Diencephalon • Components – Thalamus, Subthalamus, Epithalamus, Hypothalamus 9

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 • Regulation of sleepwake cycle 10

Cerebrum • Largest portion of brain • Divisions – Right – Left – Lobes: Frontal, parietal, occipital, temporal, insula • Cortex: Outer surface • Medulla: Center 11

Basal Nuclei and Limbic System • Basal nuclei – Motor function control • Limbic system – Basic survival functions as memory, reproduction, nutrition – Emotions 12

Limbic System 13

Meninges • Connective tissue membranes – Dura mater: Superficial – Arachnoid mater – Pia mater: Bound tightly to brain – Spaces • Subdural: Serous fluid • Subarachnoid: CSF 14

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 15

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 16

Flow of CSF 17

Brain Blood Supply • Brain – Requires tremendous amount of blood – Receives 15 -20% of blood pumped by heart – Interruption 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 18

Formation of the Neural Tube 19

Development of Brain Segments and Ventricles 20

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) 21

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) 22