The brainstem Flashcards
What are the embryological names for forebrain, midbrain and hindbrain?
Forebrain: prosencephalon
Midbrain: mesencephalon
Hindbrain: rhombencephalon
Main role of the midbrain?
Maintaining conciousness, processing visual and auditory data
Main role of the pons?
Relays sensory information to cerebellum and thalamus
Main role of the medulla?
Relays information to the thalamus
3 general functions of the brainstem?
Conduit: long tracts to/from spinal cord pass through brainstem
Cranial nerves: sensory input and motor output, as well as parasympathetic motor output
Sensorimotor integration: connects to cerebellum
3 things that brainstem mediates
Autonomic control of respiratory and cardiovascular reflexes
Somatic/ autonomic modulation via descending pathways
Diffuse neuromodulatory systems regulate conscious states
What is found in dorsal part of brainstem?
Cranial nerve nuclei and sensory reflex centres
What is found in middle part of brainstem?
Ascending motor pathways and reticular formation
What is found in ventral part of brainstem?
Descending motor pathways
Describe organisation of cranial nerve nuclei in the dorsal brainstem?
Motor nuclei- medial
Mixed nuclei- more lateral
Sensory nuclei- sensory
What does tectum and tegmentum (of midbrain) mean?
Tectum= roof Tegmentum= body
Where do the corticospinal and corticobulbar tracts pass?
Through cerebral peduncle of the midbrain
What are the white parts of the internal pons?
Remnants of corticospinal tract
What can be found in open medulla?
Cranial nerves, inferior cerebral peduncle, nuclear groups that project to cerebellum
Where do cranial nerve afferents arise from?
Ganglia
Where are second order sensory neurons located?
Cranial nerve nuclei
Which cranial nerves are only sensory?
I, II, VIII
Which cranial nerves are only motor?
III, IV, VI, XI and XII
Which cranial nerves are mixed?
V, VII, IX and X
Describe 3 types of cranial nerve motor nuclei
- Somatic motor nuclei project to skeletal muscle
- Branchial motor nuclei project to muscles derived from branchial arches (craniofacial structures such as movement of jaw, expression etc)
- Visceral motor nuclei: preganglionic parasympathetic fibres
At what level does spinal cord begin to become brainstem?
C2
Describe position of nuclei, midline to laterally, in the brainstem
Somatic motor (LMN)
Visceral motor (pre ganglionic parasympathetic)
Visceral sensory
Somatic sensory
Define cranial nerve nuclei
Columns of neurons associated with cranial nerves
What type of nerve is hypoglossal? What does it innervate?
Somatic motor
Internal and external tongue muscles
What type of nerve is spinal accesory? Where does it arise from?
Branchial motor
Arises from branchial motor neurons in spinal cord
What does spinal accesory nerve innervate?
Trapezius and sternocleidomastoid
Where does spinal accesory nerve enter/ exit the skull?
Enters through foramen magnum
Exits through jugular foramen
What type of nerve is vagus? Where does it arise from?
Mixed nerve
Arises from nucleus ambiguus
What type of nerve is glossopharyngeal?
Mixed (although mainly has sensory functions)
Functions of glossopharyngeal nerve
Parasympathetic secretomotor to parotid
special sensory- detects taste at back of mouth
touch fibres from back of mouth
What happens if there is damage to vagus?
Loss of voice on affected side
What happens if there is damage to glossopharyngeal?
Loss of gag reflex on affected side
What type of nerve is vestibulocochlear? What information does it convey?
Sensory
Special sense of hearing, perception of self motion, head position and spatial orientation
What type of nerve is facial?
Mixed
5 somatic branches of facial nerve
Temporal, zygomatic, buccal, mandibular, cervical
What does facial nerve parasympathetic output control?
Nasal secretion and lacrimation
Sensory input from facial nerve? Describe course of sensory fibres?
Taste afferents from anterior 2/3 of the tongue
Travel from chorda tympani via geniculate ganglion to rostral nucleus of solitary tract
What type of nerve is trigeminal?
Mixed nerve
Motor output of trigeminal nerve?
V3: motor to muscles of mastication
What does the medial longitudinal fasciculus connect?
The cranial nerve nuclei controlled eye movement and vestibular nuclei
Which cranial nerves innervate extraocular eye muscles?
III, IV and VI
What does damage to the medial longitunal fasciculus cause? Why?
Internuclear pohthalmoplegia
Normally when looking left VI nucleus fres to contract left lateral recus. The righ lateral rectus also contracts due to connection to contralateral oculomotor nucleus.
Both eyes should look in same direction, but if there is damage to MLF this doesn
t work
What usually causes unilateral internuclear ophthalmoplegia?
A stroke
What usually causes bilateral internuclear ophthalmoplegia?
MS
What is the role of signals from vestibular nuclei?
Keep the eyes balanced in space, despite head movements
What does the MLF become in the spinal cord?
Medial vestibulospinal tract
Role of medial vestibulospinal tract?
Acts on motor neurons in neck to coordinate reflexes
What cranial nerves coordinate pupillary light relfex?
CNII in and III out
What is the reticular formation?
Forms a core of interconnecting neurons
Key centre for regulating conciousness
Integrates and modulates inputs
What does reticular formation have output to?
hypothalamus, cortex, limbic system and descending projections
What part of brainstem produces noradrenaline?
Locus coeruleus
What part of brainstem produces serotonin
Raphe nuclei
What part of brainstem produces dopamine?
Substantia nigra and ventral tegmental area
What part of the brainstem produces acetyl choline?
Pedunculopontine nucleus
What is the function of dopamine made in substantia nigra?
Control of movement
Low levels of dopamine from SN=
parkinsons
What is function of dopamine made in ventral tegmental area?
organising behaviour, focusing and attention, reward and motivation
Disturbance of dopamine levels from VTA=
Schizophrenia and addiction
Functions of noradrenaline?
activates motor system so reflees are faster, inhibits pain,
Functions of serotonin?
Rostrally: inhibit basal forebrain GABA cells to produce arousal
Caudally: modulates pain perception
Results of deficits in serotonin?
OCD, depression, anxiety, aggresion
How would you define a monoamine and cholinergic brainstem centre
Nuclei containing specific neurotransmitters which modulate variety
What controls noradrenaline release?
Sympathetic nervous system control centre activated by the hypothalamus
Descending fibres carried in reticulospinal tract activate preganglioninc sympathetics
