CNS anatomy

Cross-section (transverse) of medulla:

- Pyramid containing corticospinal tracts - Inferior olivary nucleus - relays proprioceptive information to the cerebellum. - Medial lemniscus - Reticular formation - intranet of the brain o Connects everything to everything. o Keeps you awake o Valium shuts down the reticular formation - CN VII nucleus - CN XII nucleus - CN X nucleus

There are two main groups of tracts in the white matter of the spinal cord:

1-" The ascending (sensory) tracts 2-The descending (motor) tracts

Medial lemniscal (dorsal column) pathway:

1-1st order neuron cell body sits in dorsal root ganglion 2-sensory information travels up dorsal column to synapse with 3-second order neuron - in this case the medulla at nucleus gracilis & nucleus cuneatus. 4-Axon crosses the midline (decussation) becoming the medial lemniscus 5-Travels up to thalamus where it synapses with 3rd order neuron 6-Axon of 3rd order neuron informs cortex about information.

pair of spinal nerves (31 segments) consists of

1-8 of the segments are in the cervical region. 2-12 in thoraxes 3-5 in the lumbar 4-5 in sacral 5-1 in coccygeal

Ponto medullary sulcus:

1-CN VI - most medial 2-CN VII 2-CN VIII - most laterally

nervous sysytem is divided into 2 groups

1-CNS 2-PNS

cross section of midbrain

1-Cerebral peduncles: pyramidal tracts pass through 2-Sup. or inf. colliculus 3-Cerebral aqueduct 4-CN III nuclei 5-Reticular formation 6-Medial lemniscus 7-Red nucleus: 8-Substantia nigra:

Ventral corticospinal

1-Descends in the anterior column 2-Decussates at the level of the spinal cord 3-Synapse with the lower motor neuron in anterior horn

brain is divided into

1-Forebrain 2-Midbrain 3-Hindbrain

function of brain stem

1-It acts as a passageway for all ascending and descending tracts between the cerebrum and spinal cord. 2-It contains the nuclei of the cranial nerves III to XII. 3-It regulates the automatic behaviors required for survival such as respiration.

The white matter of the spinal cord

1-It surrounds the gray matter 2-IT is organized as ventral, lateral, and dorsal columns on each half of the spinal cord.

Two different types of pyramidal pathways

1-Lateral corticospinal 2-Ventral corticospinal

cross section of pons

1-Pontine nuclei 2-Corticospinal tracts Tracts can be ascending or descending pathways 3-Medial lemniscus 4-CN V nuclei 5-Reticular formation 6-4th ventricle

cross section of medulla

1-Pyramid containing corticospinal tracts 2-Inferior olivary nucleus 3-Medial lemniscus 4-Reticular formation 5-CN VII nucleus 6-CN XII nucleus 7-CN X nucleus 8-fourth ventricle

pons consists of

1-The white matter of the pons is formed by the ascending and descending tracts. 2- The gray matter is organized as nuclei embedded in the white matter

Spinocerebellar pathway

1-body of first order neuron in DRG 2-synapse with body of second order neuron in dorsal horn ascends ipsilaterally and end in the cerebellum no decussation and no third order neuron.

the CNS is divided into 2 groups

1-brain 2-Spinal cord

Enlargement of the spinal cord occurs in

1-cervical region 2-lumbar region

PNS is divided into

1-cranial nerve(12 pairs) 2-spinal nerves(31 pairs)

medulla oblongonta is composed of:

1-inferior part: same arrangement as spinal cord 2-superior part: the gray matter is embedded as a nuclei within white matter

bain stem consists of

1-midbrain, 2-pons, and 3-medulla oblongata.

medulla oblogonta has 2 pairs of elevation

1-pyramid elevation 2-olive elevation (lateral)

Substantia nigra

1-specific to midbrain 2-part of pyramidal pathway and 3-coordinates voluntary movements Damage results in Parkinson's disease (resting tremor)

Red nucleus:

1-specific to midbrain and 2-relay centers of extra pyramidal pathway Lesions of the red nucleus results in intention tremor

Spinothalamic pathway

1st order neuron DRG 2nd order neuron in dorsal horn 2nd order neuron immediately decussates and ascends contra-laterally 2 parts travelling in lateral and anterior columns synapse in thalamus with 3rd order neuron

tracts

= bundles of myelinated nerve fibers

6. Nervous system is best described as.... a) Receives and processes the impulses from external / internal environment. b) Functionally can be subdivided into PNS and CNS c) Structurally is classified into somatic and visceral components d) All of the above e) B & C only

A

Cerebral spinal fluid circulates in the? a. Subarachnoid space b. Epidural space c. Subdural space d. Dural sinuses

A

Sensory fibres from which cranial nerve do not pass through the thalamus? a. CN I b. CN II c. CN VII d. CN VII

A

where do all of your senses pass? what is the exception?

ALL OF YOUR SENSES PASS THROUGH THALAMUS EXCEPT SMELL

7. Which of these segments is NOT part of brain stem? a) Medulla oblongata b) Spinal cord c) Midbrain d) Pons e) B & D

B

Sympathetic fibres that synapse in pre-vertebral ganglia supply the? a. Pelvis b. Abdomen c. Thorax d. Head and neck

B

Which of the following spinal segments would carry cell bodies of sympathetic neurons? a. C5 b. T12 c. S1 d. Co

B

Abducent exits the cranium from? a. Foramen rotundum b. Jugular foramen c. Superior orbital fissure d. Internal acoustic meatus

C

At what level of the spinal cord do the dura mater and arachnid mater end? a. LI b. LIII c. SII d. Co

C

What is the origin of the ulnar nerve? a. Posterior cord b. Lateral cord c. Medial cord d. Superior trunk

C

Which cranial nerve has parasympathetic control of the parotid gland? a. CN III b. CN VII c. CN IX d. CN X

C

Anterior view of the brainstem consists of

Cerebral peduncle of midbrain, pons, medulla (pyramid)

lateral view of brain stem

Cerebral peduncle, pons, medulla (olive) sup. culliculus inf. colliculus CN XII

Lateral corticospinal

Crosses the midline in medulla after traveling through the pyramid Synapses with a lower motor neuron in the ventral horn Supplies muscles of upper and lower limbs

Individuals who are shorter than average are more likely to have their spinal cord end at the vertebral level of? a. TXII b. LI c. LII d. LIII

D

Sensory tracts in the spinal cord travel in the ...... a. Dorsal horn b. Ventral horn c. Ventral column d. Dorsal column

D

The internal capsule contain fibres that..... a. Connect similar parts of the same hemisphere b. Connect similar areas between the left and right hemisphere c. Connect cerebellum to the midbrain d. Connect the cerebrum to lower neural centres

D

The muscles of the medial compartment of the thigh and the skin of the medial thigh are innervated by what nerve? a. Lateral femoral cutaneous b. Femoral c. Sciatic d. Obturator

D

Which of the following nerves supplies the pelvic floor? a. Sciatic b. Femoral c. Obturator d. Pudendal

D

13. Which of the following cranial nerves supplies the extra ocular muscles? a) CN II b) CN III c) CN IV d) All of the above e) B & C

E

2. Which statement regarding CSF is true? a) Is produced by choroid plexus in ventricles b) Flows between arachnoid and dura mater c) Is drained into dural venous sinuses d) All of the above e) A & C

E

Columns of the spinal cord are best described as.... a) Made up of gray matter b) Occupied by sensory and motor neurons c) Demarcated at the surface by vertical fissures / sulci d) Formed by ascending / descending tracts e) C & D

E

This cranial nerve is involved in distribution of parasympathetic fibers. a) CN III b) CN V c) CN X d) All of the above e) A & C

E

name the ascending tracts

I. dorsal (posterior) spinocerebellar tract, II. dorsal column (medial lemniscus) tract III. lateral spinothalamic tract IV. anterior spinothalamic tract

Medial lemniscal (dorsal column) pathway:

In charge of touch and conscious proprioception

columns

It compromised of tracts that carry sensorimotor information

Lateral horn

It houses autonomic neurons It is only present in certain segments of the spinal cord

Posterior horn

It houses cell bodies of sensory neurons. These neurons receive information from the sensory neurons residing in the dorsal root ganglia whose axons form the dorsal root of the spinal nerves

the ponto-medullary sulcus,

It is a transverse sulcus that separates the medulla oblongata from pons

33-B 34-C 35-A

Match the numbers with correct labels on the diagram 33. Foramen ovale 34. Passage for CN VII 35. Jugular foramen

charactersistics of ascending tract

Sensory tracts consist of 3 sets of neurons exception: dorsal spinocerebellar tract

sympathetic and parasympathetic neurons in the spinal cord

Sympathetic neurons of lateral horn T1-L2 - SEGMENTS*** Parasympathetic neurons of lateral horn S2-S4 SEGMENTS***

Spinothalamic pathway

Temperature & pain

what is seen in the anterior part of midbrain

The anterior aspect of the midbrain presents two columns, the cerebral peduncles, between which the cranial nerve III emerges.

nerve emerged from anterolateral surface of the medulla oblongata

The cranial nerves IX, X, XI, and XII

the relation of pons to PARTS of brain stem and to cerebellum

The pons is related to the 1-cerebellum (posteriorly), 2-medulla oblongata (inferiorly), 3- midbrain (superiority).

gray commissure

The right and left halves of the gray matter are connected by a narrow strip connecting the central canal

Motor pathways:

Usually comprised of two neurons only: Upper and Lower motor neurons 1-Upper motor neuron expected to be in cortex or brainstem 2-Lower motor neuron generally in ventral horn

most of the nuclei are associated with cranial nerve

V, VIII ,IX ,X ,XI ,XII

The nuclei deep to these colliculi are

a rely center for the visual and auditory reflexes respectively

CN IX, X, XI, XII

all lateral to pyramid

CN III

between the cerebral peduncles

which cerebral nerve does not arise from

brainstem

The horn contains

cell bodies of neurons

Extra pyramidal pathways

control involuntary contractions of skeletal muscles (subconscious): maintain balance and posture.

Pyramidal pathways

control your voluntary skeletal muscle movements

inf. colliculus

controlling some of your auditory reflexes

sup. culliculus

controlling some visual reflexes

The ascending (sensory) tracts

convey the messages from the periphery to the upper centers of the nervous system

The descending (motor) tracts

convey the messages from the upper centers of the nervous system to the periphery

nerve emerged from the ponto-medullary sulcus

cranial nerve VI,VII and VIII

Conus medularis

distal end of the spinal cord

Spinal cord ends at

ends at LI/L2 a)70% of normal population LI/LII b)T12 or LIII in some other people depending on height

CN V

exiting from sides of pons

Spinal cord starts at

foramen magnum

On the posterior aspect of the midbrain, there are

four elevations known as superior and inferior colliculi.

Length of spinal cord

has nothing to do with height (between 43 and 45 cm)

Reticular formation

intranet of the brain Connects everything to everything. Keeps you awake Valium shuts down reticular formation

The second-order neuron

is located either in the dorsal horn of the spinal cord or within the medulla oblongata and relays impulses to the thalamus

Anterior horn

is where you find cell bodies of the motor neurons whose axons exit the cord via the ventral roots and travel directly to the muscles

CN IV -

lateral to cerebral peduncles

which parts are seen in all section of brain stem

medial leminiscus and reticular formation

the relation of midbrain to PARTS of brain stem and to cerebellum

midbrain connect to cerebellum inferiorly and diencephalon superiorly

Neuron can be

motor or sensory

Pontine nuclei:

relay centres, which receive motor impulses from your brain and pass those impulses to your cerebellum.

Inferior olivary nucleus

relays proprioceptive information to cerebellum.

The first-order neuron

resides in: the dorsal root ganglion of the spinal nerve and conducts impulses from sensory receptors to the spinal cord or medulla oblongata.

. The third-order neuron

residing in the thalamus conveys impulses to the general sensory area of the parietal lobe of the cerebral cortex

Spinocerebellar pathway

subconscious proprioception

The gray matter of the spinal cord is shaped like

the letter "H" with a ventral (anterior) horn and a dorsal (posterior) horn on each side.

Each spinal nerve is formed by

the union of the ventral and dorsal roots

Ventral corticospinal Innervates

trunk muscles