Neuroanatomy - Brain stem, Spinal cord, Protection of CNS Flashcards
The brain stem consists of what?
And what is its role?
Midbrain, pons, medulla oblongata
- Rigidly programmed automatic behaviour
- Pathway between high & low neural centres
- Associated with 10 pairs of cranial nerves
What contains large pyramidal motor tracts on the midbrain?
The 2 cerebral peduncles (sends motor instructions to body)
What surrounds the cerebral aqueduct? What is its function? (midbrain)
The periaqueductal GM surrounds the cerebral aqueduct. It is involved in pain suppression (inhibitory)
Describe the corpora quadrigeminal
From the midbrain
4 bodies:
Paired superior colliculi responsible for visual reflex
Paired inferior colliculi responsible for auditory relay & startle reflex
High melanin content, a precursor of dopamine
Substantia nigra
What is richly vascularized and is a relay nuclei for descending pathways? What movement does it help with?
The red nucleus, limb flexion
Which level of the ventricle is the pons at and which cranial nerve is it associated with? Other pons nuclei also a part of ….
4th ventricle
- Cranial nerves: Trigeminal (V), Abducens (6), Facial (7)
- Also a part of reticular formation
Medulla oblongata has a decussation of pyramids. Explain this.
Contralateral: fibers cross over to opposites side before continuing to spinal cord.
What is the role of the inferior olivary nuclei and which part of the brain stem is it from?
The olivary nuclei is from the medulla. It is responsible to relay sensory info of muscles stretch & joints to cerebellum
List the cranial nerves associated with the medulla.
Cranial nerves Hypoglossal (XII), Glossopharyngeal (IX), vagus (X) and vestibulocochlear (VIII)
Explain the role of the medulla oblongata.
The medulla has an important role for autonomic reflex centre for homeostasis.
- Cardiovascular centre
- Respiratory centre
- Vomiting, hiccups, seezing
Does the medulla overlap with another structure?
Medulla overlaps with hypothalamus because the instructions are sent through medullary centres to carry out motor output.
Timing and patterns are influenced by the cerebellum. Is doing the movements conscious or not under conscious control? Examples?
Not under a lot of conscious control, automatic
- Ex. Driving, typing, playing instrument
Describe the cerebellum and how is it connected.
Bilaterally symmetrical and connected by vermis. There are transverse fissures called folia.
Lists the 3 lobs of the cerebellum and their roles.
Anterior and posterior lobes have overlapping sensory & motor maps of body, and receiving input from a body regions also controls output from the same region.
Flocculonodular lobes - equilibrium sensory (balance & eye movement)
Describes the medial, intermediate, and lateral aspects of the cerebellum.
Medial: head and girdle
Intermediate: distal limbs, skilled movement
Lateral: association areas - planning movements
Explain how a movement response is carried out by the cerebellum (how is it the blueprint).
Coordination of proprioceptive, planning info, and instructions to motor cortex via thalamus.
Explain ipsilateral. Which part of the brain does this applies to?
Fibers entering and leaving are affecting the same side of the body.
- Cerebellar peduncles
What does the cerebellar peduncles connect?
The cerebellar peduncles connect the cerebellum to the brain stem
Describe the superior (outgoing) peduncles and what part of the brainstem does it connect to.
Superior peduncle connect cerebellum to midbrain.
Fibers containing instructions are going from cerebellum to midbrain to thalamus (gateway) to motor cortex.
Describe the middle (incoming) peduncles and what part of the brainstem does it connect to.
Middle peduncle connect cerebellum to pons.
Pons passes the info about voluntary motor activities initiated by motor cortex to cerebellum.
Describe the inferior (incoming) peduncles and what part of the brain does it connect to.
Inferior peduncle connect cerebellum to medulla.
Sensory info from proprioceptors & vestibular nuclei to cerebellum.
Briefly describe the cerebellar processing to fine-tune motor activity. (Ask what when where how)
- Cortex frontal motor association area - plan and indicate intention of action… sends collaterals to cerebellum
- Cerebellum also receives proprioceptive & visual/equilibrium info
- Cerebellar cortex receives the info and determines best way to coordinate force
- Via superior peduncles, cerebellum dispatches blueprint for coordination to cerebral motor cortex and to brain stem nuclei (ex. red nucleus)… to motor neurons of spinal cord
Cerebellar injury is linked to what?
Loss of muscle tone - clumsy movements
Explain the meaning of emotional-visceral brain and what makes up the limbic system.
- Amygdala: fear, danger, anger
- Hippocampus: emotions & memories
- Anterior cingulate gyrus: gestures, body language
The limbic system links 3 things…
Odour, memories, & emotions
Explain the function of the reticular activating system RAS
Maintain arousal & filter incoming signals
What is the ideal spot for a puncture to the spinal cord and why?
Below 1-2L, lumbar puncture
Because nerves are more dispersed
Briefly describe the spinal cord
A 2-way conducting system
- Major reflex centre and initiate complex patterns for motor activity
The spinal cord must be held in place. This structure is pia matter shelving that has indentations to allow the spinal cord to be anchored loosely.
Denticulate ligaments
The spinal cord must be held in place. This structure is pia mater-covered conus extension
Filium terminale
What is the cauda equina?
“Horses’ tail”, terminal neurons of spinal cord that come down then out laterally.
The anterior (ventral) and posterior (dorsal) horns of the spinal cord are connected by what?
Gray commissure, which is where the central canal is for CSF
What is associated with the lateral horns of the spinal cord?
The thoracic & superior lumbar regions of spinal cord.
The anterior horns are largest where?
Cervical & lumbar enlargements (for upper & lower limbs)
Compare and contrast the 3 horns of spinal cord GM
Posterior horns: interneurons, input from somatic & visceral, enter via dorsal root
Anterior horns: somatic motor neurons exit via ventral roots
Lateral horns: ANS motor neurons to visceral organs exit via ventral roots
What forms the dorsal root ganglions?
Afferent fibers from peripheral sensory receptors
List the general properties of spinal tracts
- Most pathway have decussation
- Most consists of 2-3 neurons chain
- Somatotopy
- All pathways are paired
What the 3 meninges and what are the functions of the meninges (meninx sing.)?
Dura, arachnoid, pia matter
- Cover & protect CNS
- Protect blood vessels & encloses venous sinuses
- Contain CSF
- Form division within skull
Which of the layers of the dura matter that the spinal cord has?
Only the meningeal layer
List the two layers of dura matter.
Outer periosteal and inner meningeal layer
The dural septa creates partitions and anchoring. List the 3 fissures.
- Falx cerebri: L&R cerebral hemispheres
- Falx cerebelli: (vermis) L&R cerebellum
- Tentorium cerebelli: Cerebral hem & cerebellum
What is the space that separates the dura mater from he arachnoid matter?
Subdural space
What is the space that separates the pian matter from the arachnoid matter?
Subarachnoid space
What is the role of arachnoid granulations (villi)?
To absorb the accumulating CSF to the venous sinus, which will be reabsorbed back into bloodstream.
What is the infection of meninges that causes them to be inflamed? What can that lead to if it remains untreated?
Meningitis.
This can develop to be encephalitis, which causes brain inflammation.
Compare CSF to plasma
Filtrate form of plasma with less proteins, less Ca++, less K+, but more vit C, Na+, Cl-, Mg++, H+.
What is the role of ependymal cells?
To filter the CSF going in and out. The cells are linked by tights junctions.
How many times a day is the CSF replaced and how much?
Every 8h or 3x a day, 150 ml
What is the disorder where the CSF build up in the ventricles faster than it can be drained?
Hydrocephalus
(Cause an increase in pressure, more fatal to adult brain because skull more rigid)
What are the 3 layers of blood-brain barrier
- Epithelium of capillary wall (tight junctions)
- Basal lamina (contains enzymes)
- Astrocytes & pericytes (maintain endothelial cells)
What can get in the blood-brain barrier?
Glucose, essential amino acids, electrolytes
- Facilitated diffusion and fat-soluble molecules (including drugs and alcohol)
Where is the blood-brain barrier very permeable?
Near vomiting centre and hypothalamus
Summarize the formation & circulation of CSF.
- The choroid plexuses are found on the 3rd and 4th ventricles where the CSF is produced.
- CSF flows through the ventricles and then into the median and paired lateral apertures to reach the subarachnoid space.
- Arachnoid granulations villi will reabsorb CSF into dural (venous) sinuses.
- Turnover 3x a day
