Study sets, textbooks, questions
Upgrade to remove ads
Lecture 7- Brainstem and cranial nerves 1
Terms in this set (72)
Components of the brain:
1. Forebrain (PROSENCEPHALON)
3. Pons and cerebellum (METENCEPHALON)
FUNCTIONS OF THE DIENCEPHALON:
1. Relay and processing centers for sensory information.
2. Centres controlling emotions, autonomic functions and hormone production.
FUNCTIONS OF THE MESENCEPHALON:
-processing of visual and auditory data.
-Generation of reflexive somatic motor responses.
-Maintenance of consciousness.
FUNCTIONS OF THE cerebrum:
-Conscious thought processes, intellectual functions.
-Memory storage and processing.
-Conscious and subconscious regulation of skeletal muscle contractions.
FUNCTIONS OF THE pons:
-Relays information to the cerebellum and thalamus.
-Subconscious somatic and visceral motor centers.
FUNCTIONS OF THE medulla oblongata:
-Relays sensory information to the thalamus and to other portions of the brainstem.
-Autonomic centres for regulation of visceral function (cardiovascular, respiratory and digestive system activities).
FUNCTIONS OF THE cerebellum:
-Coordinates complex somatic motor patterns.
-Adjusts output of other somatic motor centres in brain and spinal cord.
Function of the brainstem:
1. Conduit --> long tracts to or from the spinal cord pass through the brainstem.
2. Cranial nerve functions --> sensory input and motor output for the head plus parasympathetic motor output; cranial nerves also carry special senses and the brainstem coordinates reflexes involving them.
3. Integrative centres in the brainstem:
-sensorimotor integration - connectivity with cerebellum (coordination); reflex centres.
Brainstem core or reticular formation mediates:
-autonomic control of important respiratory and cardiovascular reflexes & other behaviours e.g., swallowing, sneezing.
-Somatic/ autonomic modulation via descending pathways (reticulospinal tract, premotor sympathetics)
diffuse neuromodulatory systems are important in regulation of conscious states as well as affecting sensory, motor and cognitive functions.
Dorso-ventral organisation of the brainstem:
1. What is located in the DORSAL part ?
2. What is located in the middle part (TEGMENTUM)?
3. What is located in the VENTRAL part ?
1. CRANIAL NERVE nuclei and SENSORY REFLEX centres.
2. ASCENDING pathways & RETICULAR FORMATION (with integrating nuclei; descending sympathetic axons.
3. DESCENDING motor pathways e.g., CORTICOSPINAL & CORTICOBULBAR tracts; rubrospinal, reticulospinal and vestibulospinal tracts arising in brainstem.
1.Where are sensory reflex centres located?
2. Where are the DCML, Spinothalamic and Spinocerebellar tracts located?
1. In the dorsal part- they are more LATERAL (whilst motor are more medial).
2. In the tegmenjtum (middle). The RF if located centrally, MLF and DCML are located medially.
Organisation of the brain stem:
The ventral side has descending tracts.
Dorsal features of the mid-brain:
> superior - important for VISUAL reflexes (associated with CN II).
>Inferior - more involved in HEARING.
-The floor of the 4th VENTRICLE can be seen on the dorsal surface.
-In the pons = links to cerebellum.
Ventral surface features: <- you can see tracts.
-the cerebral peduncle - carries the CORTICOBULBAR fibres in the midbrain.
-In the pons are fibres going media-laterally.
Therefore corticospinal tract is located on the VENTRAL surface of the brainstem and the DORSAL part of the spinal cord.
There is a crossing at the spina-medullary junction. It is the motor crossing here and then it continues running down in the torso-lateral part of the spinal cord.
REVIEW THE INTERNAL ANATOMY OF THE BRAINSTEM.
1. How many pairs are there?
2. What information do they provide?
1. 12 pairs
-Provide sensorimotor innervation of the skin, muscles and joints of the head & neck.
-Mediate vision, hearing, taste and olfaction (special senses)
-Carry autonomic fibres that control visceral functions e.g. gut, breathing, heart rate, and blood pressure regulation.
>Cranial nerve nuclei are one origin of preganglionic parasympathetic neurons i.e., the cranio-sacral system
What are the 12 cranial nerves and where can they be seen?
Which nerve is not associated with the brainstem?
1. There are 12 nerves: Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear (Auditory), Glossopharyngeal, Vagus, Accessory, Hypoglossal---
2. Cranial nerves can be seen from the ventral surface.
3. 11 nerves are associated with the brainstem- Olfactory is not.
Cranial nerve nuclei
-Do cranial nerves have distinct sensory and motor roots as found in the spinal cord?
-Functionally, cranial nerves are analogous to spinal nerves in their afferent compliment. Afferents arise from ganglia (except- mesencephalic nucleus of V).
- Second order sensory (relay) neurons are located in cranial nerve nuclei.
-Motor efferents arise from cranial nerve nuclei. Such nuclei control parasympathetic and somatic motor functions.
Cranial nerve nuclei continued
-Where do sensory afferents arise from?
- Where are Second order sensory (relay) neurones located?
-Where do motor efferents arise from?
>SENSORY afferents will be in GANGLIA.
>Second order sensory (relay) neurons are located in cranial nerve NUCLEI.
>MOTOR efferents arise from cranial nerve NUCLEI --> Such nuclei control parasympathetic and somatic motor functions.
Functions of the cranial nerves:
1. Olfactory --> sense of smell.
2. Optic --> vision
3. Occulomotor --> eye movements, pupillary constriction and accommodation, muscle of eyelid.
4. Trochlear nerve --> eye movements (SO)
5. Trigeminal --> somatic sensory from face, mouth, cornea, muscle of mastication.
6. Abducens --> eye movements (LR)
7. Facial nerve --> controls muscles of facial expression, taste from anterior tongue, lacrimal and salivary glands.
Functions of the cranial nerves continued:
8. Vestibulocochlear --> hearing and sense of balance.
9. Glossopharyngeal --> sensation from posterior tongue and pharynx, taste posterior tongue, carotid baroceptors and chemoreceptors.
10. Vagus --> autonomis functions of gut, sensation from larynx and pharynx, muscles of vocal cords, swallowing.
11. Spinal accessory --> muscles of neck and shoulder.
12. Hypoglossal -->movements of TONGUE.
What are the associated cranial nerves in the midbrain region?
Functions = Associated with auditory, visual and pupillary reflexes and with eye movements.
What are the associated cranial nerves in the pons?
Functions = Its main functions are mastication (V), eye movement (VI), facial expression, taste, blinking, salivation, lacrimation (VII), and equilibrium and audition (VIII).
What are the associated cranial nerves in the medulla
Functions= Associated with equilibrium, audition (VIII), deglutition, salivation, taste (IX), respiration & circulation, GI function (X), neck & shoulder movments (XI) tongue movements (XII), coughing and vomiting (RF).
Cranial nerve organisation
-Cranial nerves enter / exit at specific rostral-caudal locations in brainstem
In general II-IV are associated with the midbrain, V-VIII pons and IX-XII medulla
-There is a lateral (sensory)- medial (motor) organisation
-There are pure sensory nerves (I, II, VIII), pure motor nerves (III, IV, VI, XI, XII) and
mixed sensory & motor nerves (V, VII, IX, X)
Cranial nerves and their nuclei.
What are the 3 types of motor nuclei?
>Cranial nerves have general somatic sensory and visceral sensory afferents like spinal nerves
>There are also special sensory afferents- i.e. vision, hearing, smell...
>3 types of motor nuclei:
-SOMATIC MOTOR nuclei project to skeletal muscle (eye muscles and tongue)
-BRANCHIAL MOTOR nuclei project to muscles derived from branchial arches (craniofacial structures)- movement of jaws (V), facial expression (VII), motor to larynx and pharynx (X) and neck and shoulder muscles (XI)
-VISCERAL MOTOR nuclei: pre-ganglionic parasympathetic fibres
In comparison to the spinal cord, where are the sensory nuclei? and also the motor nuclei?
-Sensory nuclei move laterally and ventrally.
-Motor nuclei move medially
Location of nuclei in brainstem from midline to lateral (remember they are bilateral):
1. Somatic motor: lower motor neurons (LMNs- somatic and branchial)
2. Visceral motor i.e. preganglionic parasympathetic
3. Visceral sensory i.e. from gut, blood vessels, mucosa incl. taste
4. Somatic sensory - general (V) and special (VIII).
Review cranial nerve nuclei positioning diagram
name of the nucleus and location of the nucleus for CN 1:
name of the nucleus and location of the nucleus for CN II:
(lateral geniculate nucleus is a relay center in the thalamus for the visual pathway. It receives a major sensory input from the retina. The LGN is the main central connection for the optic nerve to the occipital lobe).
Name of the nucleus and location of the nucleus for CN III
-both in midbrain
name of the nucleus and location of the nucleus for CN IV
name of the nucleus and location of the nucleus for CN V
name of the nucleus and location of the nucleus for CN VI
name of the nucleus and location of the nucleus for CN VII
Many in pons.
name of the nucleus and location of the nucleus for CN VIII
Vestibular - in pons/medulla
Cochlear - in pons/ medulla.
name of the nucleus and location of the nucleus for CN IX
-Inferior salvitory -medulla
-Trigeminal - pons
name of the nucleus and location of the nucleus for CN X
-NUCLEUS AMBIGUOUS- Medulla
-Dorsal motor nucleus- medullla
(Nucleus ambiguous = a group of large motor neurons, situated deep in the medullary reticular formation. The nucleus ambiguus contains the cell bodies of nerves that innervate the muscles of the soft palate, pharynx, and larynx which are strongly associated with speech and swallowing).
name of the nucleus and location of the nucleus for CN XI
-Nucleus ambiguous- medulla
name of the nucleus and location of the nucleus for CN XII
Which nerves pass through the solitary nucleus?
Through the center of the NTS runs the solitary tract, a white bundle of nerve fibers, including fibers from the facial, glossopharyngeal and vagus nerves, that innervate the NTS.
The HYPOGLOSSAL NERVE
Somatic motor- innervates internal and external tongue muscles .
CN XI Spinal accessory Nerve:
innervates muscles that move the neck (sternocleidomastoid and trapezius).
-Pure branchial motor- controls movement of neck & shoulder.
-CN XI: Spinal accessory nerve:
>Arises from branchial motor neurons in the spinal cord.
&trapezius muscles. ENTERS cranial cavity via FORAMEN MAGNUM and exits via the JUGULAR FORAMEN.
>The motor neurons giving rise to the accessory nerve are actually a separated fragment of the long column of the nucleus ambiguus. They arise from C3-C5.
Vagus X- afferent and efferent
-Also arising from the NUCELUS AMBIGUOUS, branchial motor innervation of the palate, pharynx and larynx is conveyed via CN X
-Parasympathetic outflow to the heart and digestive system arises from the dorsal motor nucleus of the vagus (and parasympathetic part of n. ambiguous)
-Afferents from the lungs and gut travel in the vagus nerve mediating parasympathetic reflexes, swallowing, coughing, retching etc... Visceral afferent information is processed in the NUCLEUS OF THE SOLITARY TRACT.
Mainly sensory, but is parasympathetic secretomotor to the parotid gland. So MIXED. Its main function is to detect the taste of things in the back of the mouth and secrete saliva into the mouth. It contains touch fibres from the back of the mouth and these trigger the gag reflex.
-Vagus (X) and Glossopharyngeal (IX) nerves work together to control speaking and swallowing.
-GLOSSOPHARYNGEAL provides mostly SENSORY input. Taste from posterior part of tongue is detected and conveyed to the rostral nucleus of the solitary tract (or simply SOLITARY NUCLEUS or nucleus tractus solitarius NTS) & stimulates saliva secretion. There are also sensory receptors in pharynx for touch travelling in it.
-VAGUS (from NUCLEUS AMBIGUOUS) controls pharyngeal and laryngeal (inc vocal chords) muscles & upper oesophagus.
Damage to Glossopharyngeal :
Loss of Gag reflex on affected side.
Damage to Vagus:
Difficulty swallowing, paralysis of Vocal cords on affected side.
CN VIII Vestibulocochlear nerve- in PONS.
-CN VIII conveys the special senses of audition (hearing) in its cochlear portion and our perception of self motion, head position and spatial orientation relative to gravity in its vestibular part. Vestibular nuclei receive multisensory input and enable reflexes that stabilize gaze, head and posture.
-The vestibular and cochlear nuclei form a complex spanning from the pons into the rostral medulla with separate divisions. The nerve enters the brainstem at the junction of the medulla and pons.
CN VII Facial nerve - PONS MIXED
Main action is to provide motor supply to muscles of facial expression
also enables lacrimation (parasympathetic).
1. Five somatic divisions- mainly branchial motor (some sensory fibres carry touch, pain, temperature sensations via posterior auricular nerve).
2. Parasympathetic secretomotor- superior petrosal nerve controls nasal secretion and lacrimation.
3. Taste afferents from the anterior 2/3 of the tongue travel from the chorda tympani (with parasympathetic fibres to submandibular and sublingual salivary glands) via the GENICULATE GANGLION to the ROSTRAL NUCLEUS of the SOLITARY TRACT (→ventromedial thalamus → insular cortex).
CN V Trigeminal nerve PONS MIXED
Mixed- branchial motor to muscles of mastication and general sensory.
1. Motor to muscles of mastication in V3 : Motor nucleus of V (like the facial nucleus, upper motor neuron (cortical) innervation is bilateral, so supratentorial stroke will not alter mastication)
2. Touch sensation of face (+ dura...) → Trigeminal ganglion→ Principal trigeminal nucleus
3. Pain, temperature, crude touch of face (+) → Trigeminal ganglion → spinal trigeminal nucleus
4. Proprioceptive input- muscles of mastication-- mesencephalic trigeminal nucleus
5. Nerve branches deliver parasympathetic postganglionic fibres.
What does the medial longitudinal fascicles (MLF) do?
Connects cranial nerve nuclei controlling eye movement and the vestibular nuclei.
The MEDIAL LONGITUDINAL FASCICULUS
-The MLF extends the length of the brainstem. Signals from the vestibular nuclei keep the eyes balanced in space despite head movements.
-Motor nuclei for extraocular muscle control and vestibular nuclei contributE to the MLF.
The MLF becomes the MEDIAL VESTIBULOSPINAL TRACT in the spinal cord. Acting on motoneurons for neck muscles it coordinates reflex head and neck movements to keep eyes stable in space.
What does the medial longitudinal fasciculus (in the brainstem) become in the spinal cord?
MEDIAL VESTIBULOSPINAL TRACT.
Which two nerves are involved in the pupillary light reflex?
CN II and CN III
The PUPILLARY LIGHT REFLEX
-Light- sensory input- axons of retinal ganglion cells in CNII- optic nerve
-Synapse in PRETECTAL NUCLEUS (midbrain)
-Bilateral innervation of EDINGER-WESTPHAL NUCLEUS (E-W; parasympathetic div of CNIII)
-E-W nuclei send output to both CILIARY GANGLIA which cause constriction of pupils via sphincter pupillae muscles.
PUPILLARY LIGHT REFLEX
The SENSORY INPUT of light into the eye is only from the OPTIC nerve- (it causes the pupillary light reflex i.e. the pupil constriction).
Edinger-westphal nucleus innervates both oculomotor nuclei- the occulosmotr nuclei is parasympathetic efferent which project to the CILIARY GANGLION, causing co-ordinate constriction of both pupils.
Important visual pathways
-Visual information carried by the optic nerve (CNII) is important in numerous reflexes as well as perception.
-The pupillary light reflex involving the PRETECTUM and parasympathetic E-W nucleus (→CNIII).
-Information sent to the SUPERIOR COLLICULUS is important in VISUAL FIXATION and tracking (tested by asking someone to follow your finger with their eyes).
What is in the middle part (tegmentum) of the brainstem?
ascending pathways & reticular formation (with integrating nuclei); descending sympathetic axons- these arise from the hypothalamus and they innervate pre-ganglionic sympathetics in the thoracolumbar cord.
What is the role of midbrain and rostral pontine reticular formation?
MODULATES forebrain activities.
What is the role of the caudal pontine and medullary reticular formation?
Promote COORDINATION of lower somatic and visceral motor neuronal pools.
-It forms a core of interconnecting neurons- a meshwork or reticulum.
-It acts to integrate and filter inputs- modulating both 'higher' brain centres and 'lower' spinal sensory and motor systems .
-It is a key centre for regulation of consciousness.
-Medial (motor/ output)
-Afferent input from all senses.
-Efferent output to midbrain, cerebellum, hypothalamus, thalamus and spinal cord.
-Facilitatory or inhibitory eg pain filtering inputs.
Examples of MODULATORY systems in the reticular formation:
-Diffuse reticular activating systems utilise MONOAMINES and ACETYLCHOLINE.
> Monoamines include: DOPAMINE, SERETONIN, NORADRENALINE.
-Widespread output to hypothalamus, cortex and limbic system, as well as descending projections.
Monoamine and cholinergic brainstem centres
-Locus coerulus --> NORADRENALINE.
importnat in activation and attention.
-Raphe nuclei --> SEROTONIN
raphe nuclei regulates sensory inputs and involved in mood/ emotion related behaviour.
-Predunculopontine nucleus --> Ach.
-Substantia nigra and ventral tegmental area --> DOPAMINE.
important in drive related behaviour.
- SUBSTANTIA NIGRA
>Control of movement- initiation/ switching
>Loss --> Parkinson's disease
- VENTRAL TEGMENTAL AREA
>Organising behaviour; focusing & attention; reward & motivation
>Disturbance: --> Schizophrenia; Addiction.
LOCUS COERULUS and other nuclei.
-Sympathetic NS control centre activated by the hypothalamus.
-DESCENDING fibres carried in reticulospinal tract activate preganglionic SYMPATHETICS.
-Also activates the motor system so our REFLEXES are FASTER. Don't think about it - respond!
-Also inhibition of pain.
-Ascending fibres to the forebrain activate a central sympathetic system behavioural alertness & arousal (esp. to stress/ stimuli evoking fear).
Monoamines - SEROTONIN (5-HT)
RAPHE NUCLEI - midline nuclei.
-Rostrally Inhibit basal forebrain BFC GABA cells to produce arousal; gates sensory input to cortex; effects on cognition, mood
-Caudally - modulates pain perception
-Numerous receptor types/ complex
Deficits produce OCD, depression, anxiety, aggression.
Drugs that target 5HT receptors affect mood e.g. anti depressants, also anti-migraine, anxiolytics, hallucinogens, anti-psychotics.
Noradrenaline --> alertness, energy. (also mood).
Serotonin --> obsessions and compulsions (also anxiety and mood).
Dopamine --> attention, motivation, pleasure, reward (also mood and anxiety).
Therefore some of their functions overlap.
Recap on motor divisions:
BRANCHIAL goes to facial muscles
- eye muscles
- the tongue.
organised medially throughout the somatic motor nuclei.
Branchial is located a bit more lateral.
Cranial nerve nuclei
-EW and occulomotor = somatic motor.
-Trigeminal motor nucleus = branchial motor.
-Principal trigeminal nucleus - general sensory.
-Vestibular nuclei= special sensory.
-Facial nuclei = branchial motor.
-Abducens nucleus = somatic motor.
-Spinal trigeminal nucleus = general sensory.
-Cochlear nuclei = special sensory.
-Dorsal motor nucleus of vagus = visceral motor.
-Nucleus ambiguus = branchial motor.
-Hypoglossal nucleus = somatic motor.
-Nucleus of the solitary tract = visceral sensory.
Sets found in the same folder
Lecture 12- Retinal physiology
Lecture 13- visual pathways
Lecture 1- Overview of the nervous system
Lecture 15- Neuroimaging techniques
Sets with similar terms
Pray for Dishman
anat lec exam chap 15 & 16
Other sets by this creator
Sugars and polysaccharides
Lipids and membranes
Other Quizlet sets
Retraso en el pago/ Expresiones 1
Economics Midterm Review Q&A (Ch.1-2, 4-6, & 8)
PoliSci Final Exam(Chp. 11,12,13,14,&15)
Verplichte voorbeelden geschiedenis