Cranial Nerves & Brain dissection Lab 19 Cranial Nerves & Brain dissection

Today Intro to the brain The cranial nerves Human and sheep brain anatomy Get to work CLEAN UP

Practical 4 Thurs 12/6 50 points: about half brain models and half book figures (with a few fresh brains too) Know: List of brain parts on objectives (names and locations only; you will need to know functions on the exam though) The 12 cranial nerves: names, locations, & functions (shown in blue in this lecture)

Brief intro to the brain External structures cerebral hemispheres cerebrum midbrain cerebellum pons medulla central sulcus precentral gyrus postcentral gyrus lateral sulcus longitudinal fissure frontal lobe parietal lobe occipital lobe temporal lobe Internal structures: corpus callosum basal ganglia (nucleus) Caudate Putamen internal capsule thalamus hypothalamus hippocampus amygdala pineal gland pituitary gland reticular formation fornix substantia nigra cingulate gyrus optic chiasm lateral ventricles mammilary bodies corpora quadrigemina inferior colliculus superior colliculus

Major Regions and Landmarks Figure 14–1

Regions of the Adult Brain Telencephalon (cerebrum) – cortex, white matter, and basal nuclei Diencephalon – thalamus, hypothalamus, and epithalamus Mesencephalon –midbrain (brain stem) Metencephalon – pons (brain stem), cerebellum Myelencephalon – medulla oblongata (brain stem)

Some terms nucleus: collection of neuron cell bodies in the CNS tract: collection of axons in the CNS ganglia: collection of neuron cell bodies in the PNS nerve: collection of axons in the PNS Cranial nerves Spinal nerves

Tour through the brain From caudal/inferior to rostral/superior

The Brain Stem Includes: mesencephalon (midbrain) pons medulla oblongata Note: some consider the diencephalon part of the brain stem as well

Anatomy: Brain stem Most cranial nerves are located in the brain stem

Posterior view

Medulla Oblongata

Cerebellum

Cerebellum – side view

Mesencephalon

Mesencephalon

The Diencephalon Thalamus Hypothalamus Pineal gland Pituitary gland Figure 14–5a

Telencephalon Cerebrum Basal nuclei Largest part of brain, includes huge wrinkly cerebral hemispheres Basal nuclei

The Basal Nuclei (Ganglia) Figure 14–14b, c

Lateral Ventricles

The Limbic System Figure 14–11a

The Cerebral Cortex 4 Lobes: frontal parietal temporal occipital Figure 14–12b

Cerebral Cortex landmarks Lateral sulcus Longitudinal fissure Central sulcus Precentral gyrus (primary motor) Postcentral gyrus (primary sensory) Association areas are for integrating information

Motor and Sensory Areas of the Cortex Central sulcus separates motor and sensory areas Figure 14–15a

Cranial Nerves

Cranial Nerves 12 pairs connected to brain Figure 14–18

Cranial Nerves Figure 13.5a

Cranial Nerves Twelve pairs of cranial nerves arise from the brain They have sensory, motor, or both sensory and motor functions (mixed) Each nerve is identified by a number (I through XII) and a name Four cranial nerves carry parasympathetic fibers that serve muscles and glands

3 main types of Cranial Nerves Sensory nerves: carry somatic (touch) or special sensory information Motor nerves: axons of somatic motor neurons Mixed nerves: mixture of motor and sensory fibers

Cranial Nerves I – Olfactory II – Optic III – Occulomotor IV – Trochlear V – Trigeminal VI – Abducens VII – Facial VIII – Vestibulococlear IX – Glossopharyngeal X – Vagus XI – Accessory XII – Hypoglossal On Occasion, Our Trusty Truck Acts Funny; Very Good Vehicle Anyhow

Summary of Function of Cranial Nerves Figure 13.5b

You need to learn: Names Numbers Locations Main functions (in blue)

Anterior View Lateral view

The Olfactory Nerves (I) Figure 14–19

Olfactory Nerves (I) Don’t originate or enter brainstem Primary function: special sensory (smell) Arises from the olfactory epithelium Passes through the cribriform plate of the ethmoid bone Fibers run through the olfactory bulb and terminate in the primary olfactory cortex Functions solely by carrying afferent impulses for the sense of smell

The Optic Nerves (II) Figure 14–20

Optic Nerves (II) Enter diencephalon Primary function: special sensory (vision) Arises from the retina of the eye Optic nerves pass through the optic canals and converge at the optic chiasm They continue to the thalamus (diencephalon) where they synapse

CNs III,IV,VI All motor only All innervate eye muscles

The Oculomotor Nerves (III) Figure 14–21

Oculomotor Nerves (III) Primary function: motor (many eyeball movements, pupil constriction, controlling lens shape) Origin: mesencephalon Destination: somatic motor: 4 extrinsic eye muscles: visceral motor: parasympathetic NS cell bodies in the ciliary ganglion, got to intrinsic eye muscles

The Trochlear Nerves (IV) Figure 14–21

Trochlear Nerves (IV) Smallest CN Primary function: Origin: motor (eye movement: looking down) Origin: mesencephalon Destination: superior oblique muscle (that’s it!)

The Abducens Nerves (VI) Figure 14–21

The Abducens Nerves (VI) Primary function: motor (eye movement: looking to the side) Origin: pons Destination: lateral rectus muscle (just one eye muscle)

The Trigeminal Nerves (V) Figure 14–22

Trigeminal Nerves (V) Largest CN – it’s huge! Primary function: mixed (sensory and motor) to face All sensory from face; motor for chewing Three branches ophthalmic branch (sensory) maxillary branch (sensory) mandibular branch (sensory and motor) Destinations sensory: sensory nuclei in pons motor: muscles of mastication

The Facial Nerves (VII) Figure 14–23

Facial Nerves (VII) Primary function: sensory: motor: **Bell’s Palsy mixed (sensory and motor) to face Motor to facial muscles; taste sensory: taste receptors on anterior 2/3 of tongue motor: Facial muscles, parasympathetic to lacrimal and salivary glands **Bell’s Palsy

The Vestibulocochlear Nerves (VIII) Figure 14–24

Vestibulocochlear Nerves (VIII) Primary function: special sensory vestibular branch: balance and equilibrium cochlear branch: hearing Origin: receptors of inner ear Destination: nuclei in both pons and medulla

The Glossopharyngeal Nerves (IX) Figure 14–25

Glossopharyngeal Nerves (IX) Primary function: mixed (sensory and motor) to head and neck Mainly: swallowing, some salivary gland function Origins: sensory: posterior 1/3 of tongue part of pharynx and palate carotid bodies (blood pressure/CO2 sensors) motor: motor nuclei of medulla

The Vagus Nerves (X) Figure 14–26

Vagus Nerves (X) Primary function: mixed (sensory and motor) of thorax and abdomen Only CN that extends beyond head and neck “Mr. parasympathetic” motor to para-NS Runs outside of spinal cord to visceral organs Originates in medulla

The Accessory Nerves (XI) Figure 14–27

Accessory Nerves (XI) Primary function: Origin: Two roots: motor to muscles of neck and upper back Origin: motor nuclei of spinal cord and medulla oblongata Two roots: The spinal root passes upward into the cranium via the foramen magnum The accessory nerve leaves the cranium via the jugular foramen Destinations: voluntary muscles of palate, pharynx, and larynx sternocleidomastoid and trapezius muscles

The Hypoglossal Nerves (XII) Figure 14–27

Hypoglossal Nerves (XII) Primary function: motor (tongue movements) Origin: motor nuclei of medulla Destination: muscles of tongue which aid in speech

Gross Anatomy of the human brain

Human brain

Midsagittal

Coronal

InferiorView

Sheep brain

Sheep brain inferior view

Midsagittal

Anterior View

Follow instructions in lab book look at the meninges start by examining the external brain Ventral surface first, then dorsal then look internally without cutting (fig 19.12) cut it midsagittally to see inside Try a coronal cut to see what you can find Review Sheet due next Thursday

To find: Meninges Cranial nerves I – XII (?) fissures and sulci on surface, lobes pineal gland corpora quadrigemina (part of midbrain) midbrain pons medulla cerebellum mamillary body (just one) optic chiasm corpus callosum (central) fornix lateral ventricles choroid plexus (inside ventricles) hypothalmus “pituitatry gland” (hangs off hypothalamus arbor vitae (inside cerebellum)