Brain and Cranial Nerves

Parts of the Brain

(b) Sagittal section, medial view Parts of the Brain CEREBRUM (b) Sagittal section, medial view CEREBELLUM Spinal cord DIENCEPHALON: Thalamus Hypothalamus BRAIN STEM: Midbrain Pons Medulla oblongata

Parts of the Brain

Meninges

Meninges

Ventricles

Ventricles

Origin and Flow of CSF

Cerebrum perception - sensory initiate voluntary movements memory learning understanding conscious behavior

Cerebrum The lobes of the cerebrum correspond to the bones of the braincase which bear the same names. parietal frontal temporal occipital frontal parietal temporal occipital

Cerebrum

Cerebrum

Cerebral Gray and White Matter

Cerebrum Functional Areas 1. Sensory areas 2. Motor areas 3. Association area

Cerebrum Functional Areas Primary somatosensory area (1, 2, 3) Primary visual area (17) Primary auditory area (41, 42) Primary gustatory area (43) Primary olfactory area (28 - not visible) Primary motor area (4) Broca’s area (44, 45 left hemisphere) Somatosensory association area (5, 7) Prefrontal cortex (9, 10, 11, 12 -medial view only) Visual association area (18, 19) Auditory association Area (22) Wernicke’s area (22, 39, 40 - left hemisphere) Common integrative area (5, 7, 39, 40) Premotor area (6) Frontal eye field (8)

Cerebrum Functional Areas

Cerebrum Functional Areas

Cerebrum Motor/Sensory

Lateralization

Basal Nuclei The basal nuclei also control subconscious contractions of skeletal muscles. Examples include automatic arm swings while walking and true laughter in response to a joke.

Limbic System Encircling the upper part of the brain stem and the corpus callosum is a ring of structures on the inner border of the cerebrum and floor of the diencephalon that constitutes the limbic system. The limbic system is sometimes called the “emotional brain” because it plays a primary role in promoting a range of emotions, including pleasure, pain, docility, affection, fear, and anger. Together with parts of the cerebrum, the limbic system also functions in memory.

Brain Waves Summing waves of different frequency produces some characteristic, and diagnostic patterns. Alpha (10–12 Hz (cycles/sec) waves are present when awake but disappear during sleep. Beta (14–30 Hz) waves are present with sensory input and mental activity when the nervous system is active. Theta (4–7 Hz) waves indicate emotional stress or a brain disorder. Delta (1–5 Hz) waves appear only during sleep in adults but indicate brain damage in an awake adult.

Brain Stem - Medulla Oblongata The medulla begins at the inferior border of the pons and extends to the foramen magnum. It contains all ascending and descending tracts extending between the spinal cord and cerebrum. The medulla contains nuclei which are regulators for vital body functions.

Medulla Oblongata Axons from the left pyramid cross over to the right and axons on the right cross over to the left (decussation of pyramids) – so that the left hemisphere of the brain controls the right side muscles, while the right hemisphere controls the left side.

Brain Stem -Pons The pons lies directly above the medulla and anterior to the cerebellum (2.5 cm). It acts as a bridge connecting the spinal cord with the brain and parts of the brain with each other.

Brain Stem- Midbrain The midbrain extends from the pons to the diencephalon. The cerebral aqueduct passes through the midbrain connecting the 3rd ventricle above with the 4th ventricles below (both locations of CSF formation and circulation.)

Reticular Formation

Cerebellum

Cerebellum

Compares intention with actual performance Cerebellum Compares intention with actual performance Cerebrum initiates voluntary muscle contractions and notifies cerebellum. 2. Cerebellum gets information from proprioceptors. 3. Assesses information. 4. Dispatches “blueprint” for coordination to cerebrum

Diencephalon

Diencephalon - Thalamus All sensory input Sort out information Major relay station for sensory ascending to sensory cortex, and inputs of subcortical motor nuclei and the cerebellum

Diencephalon - Hypothalamus 1. Autonomic control center 2. Center for emotional response 3. Body temperature regulation 4. Regulation of food intake 5. Regulation of water balance and thirst 6. Regulation of sleep-wake cycles 7. Control of endocrine system

Diencephalon- Epithalamus Pineal gland secretes melatonin during darkness promotes sleepiness & sets biological clock Habenular nuclei emotional responses to odors

Cranial Nerves vs. Spinal Nerves Designation C1-8, T1-12, L1-5, S1-5, Co1 Roman Numerals I – XII Number 31 pairs 12 pairs Origin Spinal cord Brain Number of roots 2 - a dorsal and a ventral root Single root Contents Mixed Most mixed; some sensory only Target Limbs/Trunk All in the Head/Neck (vagus n leaves)

Cranial Nerves

I. Olfactory nerve

II. Optic Nerve

III. Oculomotor nerve IV. Trochlear nerve VI. Abducens nerve

V. Trigeminal nerve

VII. Facial nerve

VIII. Vestibulocochlear nerve

IX. Glossopharyngeal nerve

X. Vagus nerve

XI. Accessory nerve

XII. Hypoglossal nerve