The Brain and Cranial Nerves Chapter 14 The Brain and Cranial Nerves

Brain and Cranial Nerves

Brain and Cranial Nerves 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

Brainstem Connects spinal cord to brain Parts Medulla oblongata Pons Midbrain

Brainstem Medulla oblongata or medulla Pons Midbrain 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

Brainstem and Diencephalon

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

Diencephalon Components Thalamus, Subthalamus, Epithalamus, Hypothalamus

Diencephalon Hypothalamus Thalamus Functions Subthalamus Epithalamus 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 sleep-wake cycle

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

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

Limbic System

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

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

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

Flow of CSF

Brain Blood Supply Brain Blood-Brain barrier 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

Formation of the Neural Tube

Development of Brain Segments and Ventricles

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)

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)