Structural Organisation Of The Brainstem And Spinal Cord

Question 1

The brainstem consists of…

Answer 1

Medulla oblongata
Pons
Midbrain

Question 2

What are the 3 brad functions of the brainstem

Answer 2

Connects the tracts to higher centres
Contains reflex centres
Houses nuclei of CNS 3-12

Question 3

Describe the structure of the brainstem

Answer 3

Occupies the posterior cranial fossa of the skull
Stalk like shape
Connects the spinal cord with the cerebral hemispheres and cerebellum and has long tracts of fibres present at all levels
In transverse section can be divided into 4 areas from posterior to anterior:
Tectum (roof over the ventricular system)
Ventricular system
Tegmentum (core of brainstem)
Basal portion (situated most anteriorly)

Question 4

What are the 4 areas of the brainstem in transverse section

Answer 4

Tectum (roof over the ventricular system)
Ventricular system
Tegmentum (core of brainstem)
Basal portion (situated most anteriorly)

Question 5

Where s the midbrain/mesencephalon

Answer 5

Between the Diencephalon and pons

Question 6

What links the brainstem to the thalami and the cerebrum

Answer 6

2 lateral half’s on the anterior side of the cerebral peduncles which are the part of the midbrain that links these

Question 7

What connects the 3rd and 4th ventricles of the brain

Answer 7

The hollow cerebral aqueduct running through the midbrain

Question 8

What nerves emerge from the midbrain

Answer 8

Oculomotor 3
Trochlear 4

Question 9

What is the function of the red nucleus

Answer 9

Relay station and integrator of info

Question 10

Describe the corpa quadrigemina

Answer 10

Contains 4 rounded bodies
2 superior colliculi - control reflex movements of the eyes, neck and head in response to visual stimuli movements
2 inferior colliculi - control reflex movements of the head, neck and trunk in response to auditory stimuli

Question 11

Describe what th red nucleus contains

Answer 11

Numerous blood vessels and receives info form the cerebrum and cerebellum and issues subconscious motor commands concerned with muscle tone and posture

Question 12

What is lateral to the red nucleus and what is its function?

Answer 12

Melanin-containing substantia nigra
Secretes dopamine to inhibit the excitatory neurons of the basal nuclei

Question 13

Depigmentation of substantia nigra can be indicative of…

Answer 13

Parkinson’s disease

Question 14

Describe the Pons

Answer 14

Found between the midbrain and medulla oblongata
Anterior surface - large bulge , basilar pons
Posterior surface cerebral peduncles - Tegmentum

Question 15

What is the Locus ceruleus

Answer 15

Located within the dorsal wall of the upper pons, under the cerebellum in the caudal midbrain, surrounded by the 4th ventricle
Main source of noradrenaline in the brain
Melanin granules contribute to its blue colour

Question 16

Motor root lies ….. to sensory root

Answer 16

Medially

Question 17

What nerves emerge from the groove between the medulla and pons

Answer 17

6 7 8

Question 18

What nuceli are involved with respiration

Answer 18

Apneustic centre - apneusis sustained gasping inhalation followed by a short inefficient exhalation
Pneumotaxic centres - prevents apneusis by promoting coordinated respiration

Question 19

The pons contains…

Answer 19

Sensory and motor nuclei of CNs 5,6,7,8
Nuclei involved with respiration
Nuclei and tracts that process and relay information to and from the cerebellum
Ascending, descending and transverse tracts

Question 20

Describe the function of the medulla oblongata

Answer 20

Connects the pons superiority with the spinal cord inferiority
Contains long ascending and descending fibres to higher centres
Allows brain and spinal cord to communicate
Coordinates complex autonomic reflexes
Controls visceral functions

Question 21

Describe the anterior surface of the medulla oblongata

Answer 21

Pyramids - contains corticospinal tracts
Decussation of pyramids
Olives - underlying olivary nuceli

Question 22

Describe the posterior surface of the medulla oblongata

Answer 22

Gracile tubercle
Cuneate tubercle

Question 23

What is the function of autonomic nuclei

Answer 23

Regulate/control a range of visceral activities

Question 24

Describe respiration control by medulla

Answer 24

Subset of neurons in the medulla , respiratory pattern generator that sends signals to the cranial and spinal motor nerves that directly innervate the respiratory muscles
Medulla can generate respiratory pattern fine tuned by higher centres

Question 25

Describe the cardiovascular centre of the medulla

Answer 25

• Vasomotor area rostral ventrolateral medulla and the inferior olivary complex • Most afferent fibres from the baroreceptors project to the nucleus tractus solitarii (NTS) • Inhibitory neurons from the NTS project to the vasomotor area and when stimulated and uninhibited by interneurons produces a vasoconstrictor response • Therefore an increase in pressure stimulates baroreceptor firing which causes inhibition by vasomotor interneurons causing vasodilation. •cardioinhibitory area includes the nucleus ambiguus and the dorsal motor nucleus of the vagus nerve • Excitatory neurons project from the NTS into the cardioinhibitory area • Neurons in the dorsal motor nucleus of the vagus account for the cardiac component of the baroreceptor reflex (bradycardia). Inhibitory interneurons project from the NTS onto a cardioacceleratory area and stimulation of these causes heart rate and cardiac contractility to increase

Question 26

Describe sensory and relay nuclei

Answer 26

• The fasciculus gracilis contains ascending fibres from sacral, lumbar and lower thoracic segments T6-T12 (the lower body). synapse with the ipsilateral gracile nucleus in the medulla. • It is involved in the mediation of conscious proprioception including kinaesthesia and discriminative touch sensations from the lower body. • The fasciculus cuneatus exists in thoracic segments above T6 and cervical segments and contains long ascending fibres from the upper body.

Question 27

Describe the reticular formation

Answer 27

Extends through brainstem, loose and far-flung neurons, into the cerebral cortex Reticular activating system-alertness Filters out repetitive or familiar stimuli Inhibited by sleep, alcohol, drugs Severe injury = coma

Question 28

Where does the spinal cord extend from

Answer 28

Foramen magnum L1-2

Question 29

How many spinal nerves in SC

Answer 29

31 pairs mixed spinal nerves 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal

Question 30

Signal nerved C1-7 exit…. To corresponding vertebra

Answer 30

Rostrally

Question 31

C8-S5 exit ….. to corresponding vertebra

Answer 31

Caudally

Question 32

….. and ….. enlargements in SC

Answer 32

Cervical C1-T1 and lumbosacral L1-S3

Question 33

Where do adult cord end

Answer 33

L1-L2

Question 34

Where do children’s spinal cord end

Answer 34

Caudal end of L3

Question 35

Distal end of the cord …. Emerges ….

Answer 35

Conus medullaris Emerges cauda equina l2-c1

Question 36

What anchors the cord

Answer 36

Denticulate ligaments anchors the cord within the dural sac

Question 37

What is the lumbar cistern

Answer 37

Caudal end of spinal cord Suitable for lumbar puncture Adults - between L3-L4 Children - between L4-L5

Question 38

Describe the internal structure of the spinal cord

Answer 38

Gray matter is shaped like a butterfly or an H At every level the gray matter is capped by a zone of closely packed small neurones, the substantia gelatinosa. The white matter surrounds the gray butterfly Consists of the ascending and descending tracts / fasciculi) The neurons comprising these tracts have similar origins and sites of termination. A bundle containing one or more tracts or fasciculi is called a funiculus. Two sides of gray matter connected by gray commissure

Question 39

Name and describe the 3 funiculi in each half of the spinal cord

Answer 39

The dorsal (posterior) funiculus, located between the dorsal (posterior) horn and the dorsal (posterior) median septum. The lateral funiculus which is located between where the dorsal roots enter and the ventral (anterior) roots exit the spinal cord. The anterior (ventral) funiculus located between the anterior (ventral) median fissure and the site where the ventral roots exit.