Neuro 3 Flashcards
Integrative functions
complex motor patterns, cardiorespiratory control, reflexes
Reticular formation, central core in brainstem – can’t see this in standard sections/preps. “in between” tissue
corticospinal tract
(motor – brain telling muscle what to do). Forms “pyramids” on anterior surface of medulla.
medial lemniscus
part of pathway that carries info from posterior columns – vibration, discriminative touch. Proprioception, 2 point tactile.
spinothalamic tract
temp and pain
Tegmentum - brainstem
Tissue anterior to ventricle -
Tectum (“roof”)
Tissue posterior to ventricle
Pyramidal decussation
interrupts anterior median fissure, at junction of brainstem and spinal cord. Contains corticospinal tract, motor fibers from cerebral cortex on their way to the spinal cord. Note pyramid bounded by anterolateral sulcus
Olive
has lots of cerebellum connectivity. You find hypoglossal nerve root emerge near this
Bulge created by inferior olivary nucleus
Pyramidal decussation
interrupts anterior median fissure, at junction of brainstem and spinal cord. Contains corticospinal tract, motor fibers from cerebral cortex on their way to the spinal cord. Note pyramid bounded by anterolateral sulcus.
Basal pons (BP)
Large bulge on anterior surface of brainstem. Site of many neurons that receive axons from cerebral cortex, the pontine neurons then send an axon across the midline of the pons (so-called crossing fibers) that collect laterally forming the middle cerebellar peduncle. )This is part of the cerebropontocerebellar pathway; more to come).
Middle cerebellar peduncle (MCP)
Major cerebellar input pathway
Trigeminal nerve (V)
Enters at midpontine level thru middle cerebellar peduncle.
Abducens nerve (VI)
Exits brainstem at the pontomedullary junction near midline, near edge of pyramid as it emerges from the pons.
Facial nerve (VII)
Exits lateral the abducens at the pontomedullary junction. Has two parts: motor root that is larger and more medial than the sensory root. Sometimes the sensory root is known as the intermediate nerve.
Vestibulocochlear nerve (VIII)
Exits lateral the facial nerve at the pontomedullary junction. Has two parts: a medially situated vestibular division and a more laterally situated cochlear division.
Superior cerebellar peduncle (brachium conjunctivum):
Forms much of the roof of the fourth ventricle. It emerges from the cerebellum (it is mostly a cerebellar out flow pathway) and moves towards the midline entering the brainstem near the junction of the pons and midbrain.
Lateral lemniscus
Band of fibers that covers the superior cerebellar peduncle in the rostral pons that is part of the ascending auditory pathway which terminates in the inferior colliculus, a midbrain structure.
Inferior brachium in inferior caliculus
auditory pathway. Goes to thalamus - midbrain
Cerebral peduncles
Large bundle of white matter at the base of the midbrain. It contains tightly packed fibers from the cerebral cortex on their way to the brainstem and spinal cord.
Oculomotor nerve (III)
Lower motor neurons for extraocular muscles and contains preganglionic parasympathetic neurons that control pupillary sphincter and ciliary muscles. Nucleus is located in rostral midbrain.
Trochlear nerve
: Found in caudal midbrain. The nerve leaves the dorsal aspect of the brainstem (the only one that does this) just below the inferior colliculus. Innervates the superior oblique muscle.
Caudal (closed) medulla
Note at this rather caudal level the medulla (taken at the spinomedullary junction) is not all that different in appearance from the spinal cord and part of the anterior horn (AH) is present.
nucleus gracilis (NG) and nucleus cuneatus
collectively referred to as posterior column nuclei) Part of dorsal columns.
Inferior olivary nucleus (IO):
This nucleus makes the bump we call the olive on the external surface of the medulla. Fibers leave the hilum of the inferior olivary nucleus and cross the midline to reach the inferior cerebellar peduncle; these are the internal arcuate fibers.
Rostral medulla
Inferior cerebellar peduncle (ICP
Appears and will become larger at rostral levels.
Caudal medulla
Central canal
Gracile and cuneate nuclei & tracts
Pyramidal decussation
Rostral medulla
Fourth ventricle Inferior olivary nuclei (in olive) XII, nucleus Pyramids Medial lemniscus (feet down) – carries info from posterior columns of spinal cord.
Caudal pons is attached to the cerebellum by the
middle cerebellar peduncle (MCP)
Central tegmental tract (CTT)
This is a rather heterogeneous tract that serves as a path for fibers going to and leaving the reticular formation as well as some other fiber types such as a major projection from the red nucleus to the inferior olivary nucleus. More to come on the CTT in future lectures.
Corticospinal tract
turns into pyramids in medulla.
Superior cerebellar peduncle (SCP)
present in the rostral pons at this level. The SCP is the major cerebellar outflow tract and it (mostly) projects to the thalamus and the red nucleus in the midbrain.
Caudal pons
Inferior cerebellar peduncle: mostly within cerebellum at this level
Middle cerebellar peduncle attaches pons to cerebellum
Medial lemniscus: horizontal with feet lateral (compare to rostral medulla)
Fourth ventricle present
rostral pons
Superior cerebellar peduncle
Medial lemniscus: horizontal with feet lateral, approaches spinothalamic tract
Small ventricular space: at opening of aqueduct
periaqueductal gray matter
Around the aqueduct is the periaqueductal gray matter (PAG). The PAG is very important in descending pain control to be discussed later.
SCP - caudal midbrain
superior cerebellar peduncles enter the midbrain and decussate (DSCP). Cross and dive into midbrain, make a V/X.
Substantia nigra - rostral midgbrain
nucleus that contains neurons that use dopamine as a neurotransmitter and heavily innervate the putamen and caudate of the cerebrum. Neuronal loss results in Parkinson’s disease. Important motor functions.
Caudal midbrain
Inferior colliculus
IV
Decussation of superior cerebellar peduncle
Rostral midbrain
Superior colliculus
III
Red nucleus
Substantia nigra (most of it)
sulcus limitans
separates motor and sensory nuclei in the spinal cord and in the brainstem as well.
Somatic motors hug
midline. Hypoglossal nerve in rostral medulla hugs midline as well.
Reticular Formation
Central core of the brainstem
Extends into the cerebrum as the hypothalamus
Important in the regulation of:
Posture
Some stereotypic motor behaviors
Regulating internal environment (blood pH, Co2, Respiration rate)
Pain regulation (opiates function in part here)
Sleep and wakefulness
Emotional tone
Reticular formation zones
Composed of many subnuclei or zones.
Raphe zone
Paramedian zone
Lateral zone biggest, extends out through brainstem
Raphe nuclei (“seam”)
immediately adjacent sagittal plane. Serotonergic neurons located here (seratonin)
Medial zone
alongside raphe, mixture of large and small neurons, source of most ascending and descending projections. Ex. Reticulospinal tract helps in motor function
Lateral zone
prominent in rostral medulla and caudal pons, primary involved in cranial nerve reflexes and visceral functions (heart rate, respiration rate, BP control..)
RF and movement control
Two reticulospinal tracts:
Medial: pons; ipsilateral, descends near MLF & in anterior funiculus
Lateral: medulla, descend bilaterally, in lateral funiculus
Reticular Formation & Movement
Major alternative to corticospinal tract (cerebral cortex voluntary primary way) in regulating spinal motor neurons
Influences spinal motor neurons directly
Regulates spinal reflexes
So that only noxious stimuli evoke a reflex
Reticulospinal tract neurons receive input from many areas including cerebral cortex, basal ganglia, substantia nigra, etc
RF contains
basic neural machinery for some complex patterned movements
Section brainstem-diencephalon junction in cat and it still walks
Arm swing. Responsible for more rhythmic walking movements. Not so much sophisticated movements. Having these pattern movements be so mechanistic is nice. There is symmetry if the pattern is established. If you severe a cats diencephalon from the brainstem, it can still kind of walk because of this.
Gaze centers
Midbrain vertical gaze center
Pontine horizontal gaze center
Supratrigeminal nucleus (pons)
Node that helps motor nucleus regulate chewing.
Peripheral causes theory
- bruxism
Malocclusion results in premature and one-sided contact.
Jaw movements continue in an attempt to reach the resting position.
This theory is based on clinical observation and experience with treatment
Central causes theory
Sleep-related dysfunctions cause bruxism
Input to supratrigeminal nucleus may be from basal ganglia, lateral hypothalamus, and central nucleus of the amygdala
RF is key to
modulating pain. Periaqueductal gray is central to one well described pain suppression system
PAG receives pain info from
spinomesencephalic fibers
Nucleus raphe magnus
big cells, send axons to posterior horn, receive axons from midbrain.
RF in Arousal and Consciousness
RF projections to thalamus and cortex
Midbrain and pons RF get input from multiple sensory modalities (e.g. pain; spinoreticular fibers – ascending, mostly pain)
Project to thalamic intralaminar nuclei, which project diffusely to cortex, seem to activate it, end at different parts of cortex.
Heightens arousal in response to sensory stimuli or tasks that demand attention
Norepinephrine in
locus ceruleus mainly
Substantia nigra - loaded with
dopamine neurons
Medial – ventral tegmental areas loaded wth
dopanergic neurons
Medulla NE
Solitary nucleus
Memory enhancement
Ventrolateral medulla
Pain regulation (to spinal cord)
Rostral pons NE
Locus ceruleus (blue spot) Cortex (arousal) vigilance & attention Active in attentive situations Moderate while awake Low activity during sleep
Noradrenergic Projections
Innervates practically the entire CNS; heavy projections to somatosensory cortex
Locus Ceruleus
Norepinephrine released in the cortex from the Locus ceruleus:
Respond to novel environmental stimuli
Stimulation produces:
increased state of arousal
feeling of anticipation
Facilitates attention to selected stimuli
Norepinephrine released in the trigeminal spinal nucleus (pain to face) and spinal cord:
From ventrolateral medulla
Suppresses incoming pain signals
Dopaminergic neurons in midbrain
Substantia nigra (Putamen & Caudate) Ventral tegmental area (Limbic system)
Dopaminergic neurons in midbrain
Substantia nigra (Putamen & Caudate)
Nigrostriatal, motor activity
Parkinson disease
Ventral tegmental area (Limbic system)
Mesocortical fibers
Organized thinking & planning; heavy projections to frontal cortex
Mesolimbic fibers (Nucleus accumbens, amygdala)
Emotional reward, sense of reward
Drug dependency
Dopaminergic Projections
Uses medial forebrain to send signals all over.
Ventral Tegmental Area associated with
schizophrenia
Serotonergic neurons located at
much all brainstem levels in raphe
Raphe nuclei
serotonergic neurons
Midbrain raphe nuclei to all regions of cortex
Attention: inhibition of distracting stimuli
Hypothalamus: day-night cycle
Medullary raphe nuclei to spinal cord (pain suppression)
Nucleus raphe magnus
Clinical depression
Selective Serotonin Reuptake Inhibitors (SSRI) – increase seratonin levels in brain.
Low levels of serotonin
High carbohydrate consumption
Binge eating
High levels of serotonin
Compulsive behavior and anorexia nervosa
Drugs that increase the level of serotonin are used to treat:
Depression
Anxiety
