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What is the oldest and most primitive part of the brain?

The brainstem


What is the main function of the brainstem?

Maintenance of homeostasis

CN nuclei are interspersed with the fibers of the reticular formation to form the origins of the CN’s

Contains nuclei which give rise to some of the descending motor pathways

Provides a thoroughfare for fibers passing between the brain, spinal cord and cerebellum


What do cranial nerves do?

They innervate somatic structures of the head and neck with motor and sensory supply

They mediate the special senses

They provide PSNS supply to the viscera, heart, GIT, Resp system and vasculature


Where do each of the CN's exit the brain?

I - cortex
II - diencephalon
CN’s III – XII exit the brainstem surface
III & IV from the midbrain
V & VI from the pons
VII & VIII from the pontomedullary junction
IX, X, XI & XII from the medulla
XI picks up some Cx fibers also


What CN's tend to exit medially from the brain stem?

Those that have predominantly motor function


What CN's nuclei sit medially?

Motor nuclei


What is the 4th ventricle continuous with?

The 3rd ventricle above via the cerebral aqueduct


What makes up the core of the brainstem?

The reticular formation


Foramen of Lushka is what?

The end of the lateral recesses there CSF can exit the fourth ventricle and surround the spinal cord


What is larger, the cuneate or gracile tubercle?

The cuneate (as there is more sensation in the upper limbs


What is the reticular formation?

A diffuse network of neurons and glial cells that is interspersed between the CN nuclei and tracts that traverse through the brainstem.

Its function is very poorly understood. Possibly some kind of primitive motor centre.


What are the key functions of the reticular formation?

Coordinates arousal for the adjustment of conscious perception of our environment for sleep & variations in alertness

Controls our habituation to ‘insignificant’ sensory information

Modulation of pain sensation

Regulation of motor function for muscle tone, balance & posture

Relays audiovisual information to the cerebellum for integration into motor control systems

Coordination of autonomic function and rhythmic pattern generation for breathing & swallowing


What art the primary neurotransmitters in the reticular formation nuclei?



What is noradrenaline? Where is it made? Where does it usually exert its effects? What does it contribute to?

Largely produced by the locus coeruleus

Exerts its affect on:
- Hippocampus & Amygdala
- Cingulate gyrus & Neocortex
- Thalamus & Hypothalamus
- Striatum
- Cerebellum
- Spinal cord

Contributes to:
- autonomic regulation
- behavioural arousal (to control alertness & vigilance)
- Is a key ‘stress’ hormone


Where is the majority of the bodies serotonin produced and found? How much is found here? What is its function here?

The GIT.


The function is to regulate GIT motility


Where is the other 10% of serotonin found in the body (not in the GIT?). What is its function here?

In the CNS.

Its function is to regulate mood, appetite and sleep.

Serotonergic neurons from the raphe nuclei spread their influence to almost every CNS structure to influence:
- ascending nociceptive pathways
- memory & learning
- Its roles as a vasoconstrictor & in clotting are also thought to have implications in migraine


What is the tegmentum?

The structures derived from the ventral part of the neural tube


What are the 3 distinct dopaminergic pathways?

Mesostriatal fibres project to the diencephalon to influence voluntary movement

Mesolimbic fibres project to the limbic cortex

Mesocortical fibres project to the frontal cortex - The function of the these pathways are not understood but thought to influence emotional and cognitive behavior


What does injury to the brain stem usually result in?

Ipsilateral cranial nerve affects
Contralateral somatic and sensory disturbance
UMN weakness contralaterally
May involve paralysis of the larynx, pharynx and irregularities in breathing and heart rhythm


What is the medulla oblongata? what does it contain?

It is a continuation of the spinal cord, with ascending sensory tracts and descending motor tracts.

Cardiovascular center
Cardiac contractility & HR
Blood vessel diameter
Respiratory center
Rhythmicity area sets basic rhythm of breathing
Centers for cough, sneeze & swallow reflexes
Nuclei for CN’s


What structures are found on the ventral surface of the medulla?

The pyramids:
- largest motor tract
- decussation of most fibres

The olives:
- key cerebellar input for precision movement
- proprioceptive and motor signals


What is found on the dorsal surface of the medulla

- Gracile & cuneate tubercles
- Relay DCML sensation to contralateral thalamus


What cranial nerves arise from the medulla



Where does CN 12 arise from? Describe CN 12 function and where it receives input from.

Arises: Hypoglossal nucleus

Controls tongue muscles (except palatoglossus) for speech & swallowing

Injury causes tongue to deviate to the injured side when protruded

Primarily motor

Receives input from the corticobulbar tract


Describe the function of the 2 portions of CN 11

Cranial portion
- From the medulla
- With CN IX/X supplies skeletal mm of throat & soft palate

Spinal portion
- cervical spinal cord
- SCM & trap mm.


What are the 3 key nuclei of CN 10 and what are their functions?

Functions via 3 key nuclei:

Dorsal nucleus for parasympathetic motor supply of the thoracic & abdominal viscera

Nucleus Ambiguus for the parasympathetic output to the heart and LMN supply to the skeletal muscle of the pharynx & larynx

Solitary nucleus for primary afferents from the pharynx, ear & viscera
(CNVII/IX also terminate here)


Describe CN 9 function

Somatic motor supply to Stylopharyngeus mm.

Parasympathetics to the parotid gland to regulate secretion

Somatic sensation & taste post.1/3 of tongue

Somatic sensation from the tonsils and middle ear

Visceral sensation from the carotid body and sinus


Describe the functions of the different parts of CN 8

Cochlear portion for audition
- begins in medulla
- Hair cell receptors in cochlea
- deafness or tinnitus produced in dysfunction

Vestibular branch for equilibrium
- begins in pons
- Mechanoreceptors in vestibular apparatus
- vertigo & ataxia produced in dysfunction


How long is the pons?

approx 1 inch long


What is the function of the pons?

Holds fiber tracts, both ascend & descend

Pneumotaxic & apneustic areas to control breathing

Cerebellar peduncles carry info to the cerebellum

Is the area where cranial nerves 5-7 exit