Organization of the Nervous System The Spinal Cord Organization of the Nervous System CNS Brain Spinal cord PNS Somatic Autonomic Sympathetic Parasympathetic

The Spinal Cord Position Lies in vertebral canal Continuous above with medulla oblongata at level of foramen magnum Ends below at lower border of L1 in adult; at birth at level of L3

The Spinal Cord 1. External features: Shape: A long cylindrical structure Enlargements: cervical enlargement lumbar enlargement Two enlargements Cervical enlargement : corresponds to the C4 to the T1 segments Lumbosacral enlargement : corresponds to the L2 to the S3 segments

4. Conus medullaris → filum terminale → S2 → coccyx caudal to the lumbosacral enlargement the spinal cord tapers gradully& becomes the conical termination Filum termination: A condensation of pia mater forms~ Cauda equina: lumbosacral roots descend ,sourrounding the filum terminale.. 4. Conus medullaris → filum terminale → S2 → coccyx

Fissure and sulci Anterior median fissure Posterior median sulcus Anterolateral sulcus －anterior (motor) roots emerge serially Posterolateral sulcus －posterior (sensory) roots enter spinal cord, each bear a spinal ganglion which constitutes the first cell-station of the sensory nerves

It's a part of spinal cord, which is connected Spinal segment: It's a part of spinal cord, which is connected with the rootlets of a pair of spinal nerve. 31 segments 8 cervical segments 12 thoracic segments 5 lumbar segments 5 sacral segments 1 coccygeal segments

Corresponding relationship between spinal segments and vertebrae spinal segments correspond to vertebrae C1-C4 C1-C4 C5 ~ T8, T l~ T4 C4 - C7, C7 ~ T3 T5 ~ T8 T3 ~ T6 T9-T12 T6-T9 L1-L5 T10-T12 S l~S5,Co1 LI  - 0 - 1 - 2 - 3

2. Internal structure The central canal Gray matter: parts: Lateral horn (only extends from Tl to L3 segments.) gray commissure (anterior and posterior ) posterior horn central canal Intermediate zone Lateral horn anterior horn Gray matter gray commissure

Main nuclei: anterior horn: medial group intermediate zone: lateral group intermediate zone: intermediolateral nucleus intermediomedial nucleus posterior horn: the nucleus posteromarginalis the substantial gelatinosa the nucleus proprius: the dorsal nucleus (thoracic nucleus) in segments C8~L3 the nucleus posteromarginalis the substantia gelatinosa the nucleus proprius the dorsal nucleus (thoracic nucleus) Intermediomedial nucleus: intermediolateral nucleus medial group lateral group

White matter White matter contains three kinds of fibers: ascending, descending, and fasciculus proprius

White matter: parts: posterior funiculus lateral funiculus posterior median sulcus posterior lateral sulcus lateral funiculus anterior lateral sulcus anterior white commissure anterior funiculus anterior median fissure

Main functions of spinal cord Conduction of excitations Reflex activity

Functions: To convey afferent impulses, which come from somatic and visceral receptors to the brain, and conduct efferent impulses from brain to effectors. Related to reflexes

The brain stem

The brain Telencephalon Diencephalon Cerebellum Brain stem mid-brain pons myelencephalon

The brain stem Consists of midbrain pons medulla oblongata Bulbopontine sulcus

1. Three parts: midbrain, pons and medulla Ⅰ. General features: 1. Three parts: midbrain, pons and medulla oblongata (from superior to inferior) 2. Position: spinal cord---diencephalon--cerebellum Ⅱ. External features: 1. Ventral surface of the brain stem 2. Dorsal surface of the brain stem

Located btwn the cerebrum and the spinal cord Provides a pathway for tracts running between higher and lower neural centers. Consists of the midbrain, pons, and medulla oblongata. Each region is about an inch in length. Produce automatic behaviors necessary for survival.

ventral surface of Medulla oblongata Pyramid: contain pyramidal tract (corticospinal tract) Decussation of pyramid formed by crossing fibers of corticospinal tract Olive : overlying inferior olivary nucleus hypoglossal nerve emerge from anterolateral sulcus Glossopharyngeal n. vagus n. accessory n. emerge from retroolivary sulcus

dorsal surface of Medulla oblongata Lower portion Gracile tubercle : overlying gracile nucleus，produced by underlying gracile nucleus Cuneate tubercle : overlying cuneate nucleus，marks the site of cuneate nucleus Inferior cerebellar peduncle participate in the 4th ventricle

Medulla Oblongata Nuclei in the medulla are associated w/ autonomic control, cranial nerves, and motor/sensory relay. Autonomic nuclei: Cardiovascular centers Cardioinhibitory/cardioacceleratory centers alter the rate and force of cardiac contractions Vasomotor center alters the tone of vascular smooth muscle Respiratory rhythmicity centers: receive input from the pons Additional Centers: emesis, coughing, hiccupping, and sneezing

Ventral surface Pons Basilar part Basilar sulcus Bulbopontine sulcus : from medial to lateral, the abducent, facial & vestibulocochlear nerves appear Middle cerebellar peduncle Trigeminal nerve Pontocerebellar trigone : the junction of medulla, pons and cerebellum

Pons Literally means “bridge” Wedged between the midbrain & medulla. Contains: Sensory and motor nuclei for 4 cranial nerves :Trigeminal (5), Abducens (6), Facial (7), &Auditory/ Vestibular (8) Respiratory nuclei: to maintain respiratory rhythm Nuclei & tracts that process and relay info to/from the cerebellum Ascending, descending, and transverse tracts that interconnect other portions of the CNS

Dorsal surface of the brain stem rhomboid fossa Boundaries Superolateral: superior cerebellar peduncle Inferolateral: gracile tubercles cuneate tubercles inferior cerebellar peduncle Lateral recess

dorsal surface of the brain stem rhomboid fossa Median sulcus Sulcus limitans Vestibular area overlies vestibular nuclei Acoustic tubercle overlying dorsal cochlear nucleus Medial eminence Striae medullares Facial colliculus: overlies nucleus of abducent n. and genu of facial nerve

dorsal surface of the brain stem rhomboid fossa dorsal surface of the brain stem Hypoglossal triangle : overlying hypoglossal nucleus Vagal triangle : overlies dorsal nucleus of vagus nerve Area postrema ：lies between the vagal triangle and gracile tubercles Locus ceruleus at the upper end of Sulcus limitans

Dorsal surface of Pons Superior cerebellar peduncle Superior medullary velum Trochlear nerve

Ventral surface Midbrain Crus cerebri Interpeduncular fossa oculomotor nerves emerge from medial of crus cerebri Posterior perforated substance

Midbrain Dorsal surface Corpora quadrigemina Superior colliculus constitute centers for visual reflexes Inferior colliculus associated with auditory pathway Brachium of superior colliculi Brachium of inferior colliculi

Dorsal surface of Midbrain Corpora quadrigemina: Superior colliculus centers of visual flexes Inferior colliculus conduct auditory sensation Trochlear nerve Brachium of superior colliculus Brachium of inferior colliculus

Midbrain contains a red nucleus and a substantia nigra Red nucleus contains numerous blood vessels and receives info from the cerebrum and cerebellum and issues subconscious motor commands concerned w/ muscle tone & posture Lateral to the red nucleus is the melanin-containing substantia nigra which secretes dopamine to inhibit the excitatory neurons of the basal nuclei. Damage to the substantia nigra would cause what?

Position Fourth ventricle Central canal →fourth ventricle →mesencephalic aqueduct→third ventricle Position Situated ventral to cerebellum, and dorsal to pons and cranial half of medulla

Internal structures Gray matter Cranial nerve nuclei Relay nuclei

Cranial nerve nuclei The Cranial nerve nuclei may be divided into 7 kinds: General Somatic motor nuclei Special visceral motor nuclei General visceral motor nuclei Visceral afferent（sensory）nuclei ( general and special ) General somatic afferent （sensory） nuclei Special somatic afferent （sensory） nuclei

General somatic motor nuclei Nucleus of oculomotor n. Nucleus of trochlear n. Nucleus of abducent n. Nucleus of hypoglossal n.

General somatic motor nuclei Nucleus Site Cranial n. Function Nucleus of Oculomotor n. Midbrain Ⅲ Supreior, inferior,and medial recti, inf. obliquus, levator palpebrae superioris trochlear n. Ⅳ Superior obliquus Nucleus of abducent n. Pons Ⅵ Lateral rectus Nucleus of hypoglossal n. Medulla Ⅻ Muscles of tongue

Special visceral motor nuclei Motor nucleus of trigeminal n. Nucleus of facial n. Nucleus ambiguus Accessory nucleus

[Special visceral] Somatic motor nuclei Nucleus Site Cranial n. Function Motor nucleus of trigeminal n. Pons Ⅴ Masticatory muscles Nucleus of facial n. Ⅶ Facial m., platysma, posterior belly of digastric, stylohyoid, stapedius Nucleus ambiguus Medulla Ⅸ,Ⅹ.Ⅺ Skeletal m. of pharynx, larynx and upper part of esophagus Accessory nucleus Medulla-cervical cord Ⅺ Sternocleidomastoid, trapezius

General visceral motor nuclei Accessory oculomotor nucleus Superior salivatory nucleus Inferior salivertory nucleus Dorsal nucleus of vagus n.

General visceral motor nuclei Nucleus Site Cranial n. Function Accessory oculomotor nucleus Midbrain Ⅲ Sphincter pupillae and ciliary m. Superior salivatory nucleus Pons Ⅶ Submandibular, sublingual and lacrimal glands Inferior salivertory nucleus Medulla Ⅸ Parotid gland Dorsal nucleus of vagus n. medulla Ⅹ Many cervical, thoracic and abdominal viscera

Visceral sensory nuclei Nucleus of solitary tract

Visceral sensory nuclei ( general and special ) Nucleus Site Cranial n. Function Nucleus of solitary tract Medulla Ⅶ,Ⅸ,Ⅹ Taste and visceral sensation

General somatic sensory nuclei Mesencephalic nucleus of trigeminal n. Pontine nucleus of trigeminal n. Spinal nucleus of trigeminal n.

General somatic sensory nuclei Nucleus Site Cranial n. Function Mesencephalic nucleus of trigeminal n. Midbrain Ⅴ Proprioception of head Pontine nucleus of trigeminal n. Pons Tactile sensation of head Spinal nucleus of trigeminal n. Medulla Pain & temperature sense of head

Special somatic sensory nuclei Cochlear nuclei Vestibular nuclei

Special somatic sensory nuclei Nucleus Site Cranial n. Function Cochlear nuclei Pons and medulla Ⅷ Sense of hearing Vestibular nuclei Sense of equilibrium

Non- Cranial nerve nuclei Nucleus position Gracile nucleus Medulla (underneath gracile tubercle) Cuneate nucleus Medulla (underneath cuneate tubercle) Pontine nucleus Pons Nucleus of inferior colliculus Midbrain Inferior colliculus superior colliculus Red nucleus Substantia nigra

White matter Ascending tracts Medial lemniscus Spinal lemniscus Trigeminal lemniscus Lateral lemniscus Descending tracts Pyramidal tract Corticospinal tract Corticonuclear tract

white matter of brain stem The long ascending & descending tracts long ascending tracts: 1. Medial lemniscus (fine touch and proprioceptive sense) 2. Spinothalamic Lemniscus [superficial sensation] 3. Trigeminal lemniscus [superficial sensation of opposite side head and facial ] 4.lateral lemniscus[Sense of hearing)

Descending tracts pyramidal system ①corticospinal tract lateral anterior ②corticonuclear tract formatio reticularis keep waking state nuclei of median raphe（5-HT）。

White matter — ascending tracts Medial lemniscus - decussation of medial lemniscus

White matter — ascending tracts Spinal lemniscus

White matter — ascending tracts Trigeminal lemniscus

White matter — ascending tracts Lateral lemniscus

White matter — descending tracts Pyramidal tract Corticospinal tract Corticonuclear tract

White matter — descending tracts Pyramidal tract Corticospinal tract Corticonuclear tract

Reticular formation of brain stem The reticular formation is recognized as the extensive area outside the more conspicuous fiber bundles and nuclei of the brain stem, in which the grey were intermingled with whiter matter. Its major function may sum up as follows:

Reticular formation of brain stem Ascending reticular activating system (ARAS) Motor central and vital centres Reticulospinal tract Cardiovascular center and respiratory center Serotonergic rapheal nuclei