1a.) Basic Topography Flashcards
What components of nervous system are classed as:
- CNS
- PNs
Describe what grey matter is composed of
- Cell bodies and dendrites with rich blood supply
- There are axons in grey matter which allow it communicate with white matter, but volume predominatly cell bodies and dendrites
- Most of computation occurs in GM
Describe what white matter is composed of
- Myelinated and non-myelinated axons with no cell bodies
- Fibres (remember fibres are axons associated with suppporting cells- which is this case is Schwann cell)
- Myelin is white
- White matter pathways connect areas of grey matter
What is the PNS equivalent of:
- Grey matter
- White matter
- Grey matter: ganglion
- White matter: peripheral nerve
*NOTE: beware of term basal ganglia as this is actually grey matter in brain
How many spinal cord segments are there?
31 segments
Each segment has a pair of spinal nerves that go on to supply a given dermatome and myotome on each side
Describe where the grey and white matter are in the CNS
- Brain:
- Spinal cord: central core of grey matter, outer shell of white matter
If you have a sensory deficit in a homuncular pattern wherre may it suggest the lesion is?
Above thalamus
Define a funiculus (pleural: funiculi)
Segment of white matter containing multiple distinct tracts which both ascend and descend (hence often contain both sensory & motor)
State and describe the position of the three funiculi in spinal cord
- Dorsal funiculi
- Laterl funiculi
- Ventral funiculi
Define a tract
An anatomically and functionally defined white matter pathway connecting two distinct regions of grey matter. Impulses travel in one direction. Found within discrete places in the funiculi. All fibres in tract have similar function.
Define a fasciculus
A subdivision of a tract supplying a distinct region of the body
Cell bodies of grey matter in spinal cord is organised into cell columns; what name is given to these columns?
Rexed’s laminae (each column has a particular number)
If we think of all the lower motor neurones supplying a given muscle, these are found at multiple adjacent cord elvels (e.g. quads are supplied by L3, L4) and can be thought of as forming a distinct nucleus controlling that particular muscle
Define a nuclues and state whether it is white or gray matter
Collection of functionally relatd cell bodies
Grey matter
Define the cortex and state whether it is grey or white matter
A folded sheet of cell bodies found on surface of brain structure
Grey matter
How thick is the cortex typically?
1-5mm
Define a fibre and state whether it is grey or white matter
An axon in association withi its supporting cells (e.g. axon plus multiple Schwann cells)
White matter
The world ‘fibre’ is used synonymoulsy with what word?
Axon
State the three types of fibres and what each one connects
- Association fibres: connect cortical regions within the same hemisphere which are relatively to close to each other (NOTE: association fibrest that connect neighbouring gyri are called U fibres)
- Commisural fibres: connect left and right hemispheres or cord halves (an example is the corpus callosum)
- Projection fibres: connect cerebral hemisphere with the spinal cord/brainstem and vice versa
State what each of the following parts of brainstem are responsible for:
- Midbrain
- Pons
- Medulla
- Midbrain
- eye movements & reflex responses to sound and vision
- Pons
- Feeding
- Sleeping (particulary REM)
- Medulla
- Cardiovascular & respiratory centres
- Contains a major motor pathway (medullary pyramids)
What sulcus separtes frontal and parietal lobes?
Central sulcus
Where is the primary motor cortex found?
Precentral gyrus
What does the lateral/Sylvian fissure separate?
Temporal lobe from frontal and parietal lobes
What does the parieto-occipital sulcus separate?
Parietal and occipital lobe
What surrounds the calcarine sulcus?
Primary visual cortex
What is the parahippocampal gyrus involved in?
It is a key cortical region for memory encoding
What is the corpus callosum?
Fibres connectin the two cerebral hemispheres
What is the thalamus?
Sensory relay station projecting to sensory cortex
What is the cingulate gyrus and where is it?
Cortical area importnat for emotion and memory. Found just above corpus callosum
What is the fornix?
Major output pahtway from hippocampus
Do all the ventricles contain choroid plexus?
Yes, all ventricles contain choroid plexus
Choroid plexus is highly vascular; true or false?
True
How much CSF does choroid plexus in ventricular system make per day?
600-700ml
Where is most of the CSF made?
Lateral ventricles
Describe the structure of the ventricular system
- Right and left lateral ventricles: in their resepective hemispheres of cerebrum. Have horns that project into frontal ,occipital and temporal lobes
- Third ventricle: between the right and elft thalamus
- Fourth ventricle: junction between pons and medulla
The connection between the lateral ventricles and the third ventricle is called the…?
Interventricular foramen of Monro
What is the connetion between the 3rd and 4th ventricle called?
Cerebral aqueduct
Describe the production and reabsorption of CSF
- Produced by choroid plexus, located in lining of ventricles and made of capillaries, loose CT and cuboidal epithelial cells
- Plasma filtred from blood by the cuboidal epithelial cells to produce CSF
- CSF travels around ventricular system
- In the 4th ventricle, CSF can drain via the foramen of luschka (lateral) and/or the foramen of Magendie (median); these are direct holes in the brian permitting CSF to drain into the subarachnoid space. Minimal drainage via central canal of spinal cord
- From subarachnoid space, CSF then drains via arachnoid granulations into dural venous sinuses.
Where is a common site for occlusion/blockage of the ventricular system?
Cerebral aqeuduct (would cause upstream dilation and potential damage to structures surrounding dilated ventricles)
Define a:
- Gyrus
- Sulcus
- Fissure
- Gyrus: raised fold of cerebral cortex
- Sulcus: valley between adjacent gyri
- Fissure: large groove between adjacent hemispheres or lobes
Does CSF contain glucose?
Yes
Briefly describe Ondine’s curse
Autonomic control of breathing is impaired hence person stops ventilating when asleep. Voluntary control of ventilation that operates during waking hours is generally intact
Where is the tentorial notch?
What passes through the tentorial notch?
Opening surrounded by anterior edges of tentorium cerebelli
Midbrain passes through it
Where are the anterior and posterior commisures?
Where is the septum pellucidium?
Separates lateral ventricles
Where is the pineal gland?
What is, and where is, the cervical enlargement?
Cervical enlaragement contains neurons for the innervation of the upper extremeties/limbs (it is an expansion of grey matter) and is from C5-T1
What is, and where is, the lumbosacral enlargement?
Contains neurons for innervation of lower extremeties/limbs (is an expansion of grey matter) and is at L1-S2
What is and where is the conus medullaris?
Where spinal cord tapers off/ends at aroundn L2
What is the filium terminale?
Continuation of pia mater from conus medullaris of spinal cord to first segment of cocyx
What is the lumbar cistern?
Enlargement of subarachnoid space distal to the conus medullaris
What imaging can we use to reveal connectivity in the brain?
DTI (diffusion tensor imaging)
When performing the knee jerk reflex, what structures detect muscle stretch whent the tendon hammer is applied?
Spindles (stretch receptors) in the quadriceps
What is a reflex?
A reflex is defined as an involuntary, unlearned, repeatable, automatic reaction to a specific stimulus which does not require input from the brain
State the 5 components of a reflex arc
- A receptor – muscle spindle
- An afferent fibre – muscle spindle afferent
- An integration centre – grey matter in spinal cord
- An efferent fibre – α-motoneurones
- An effector – muscle
What is meant by a monosynaptic reflex?
There is only one synapse between the sensory and motor neuron
Describe the reflex arc in the knee jerk
Tapping patella stretches quadriceps
- Muscle spindles detect stretch
- Causes action potentials to be fired by afferent fibres
- Afferent fibres synapse in spinal cord (L3&L4) with alpha motoneurones
- Efferent alpha motoneurones innverate extrafusal fibres causing agonist to contract
- The afferent fibres also synapse with segment controlling hanstrings (L4.L5) and activate inhibitory interneurones; the hamstrings (antagonist muscle) then relax
The sensitivity of a reflex is regulated by what motoneurons?
Gamma motoneurones
What spinal levels mediate the knee jerk reflex?
L3 & L4
What is the Jendrassik maneuvre?
Speculate on how you think it may work
Used when struggling to ellicit the knee jerk reflex. Ask patient to lock their fingers together and clench their teeth and pull when you say so.
It counteracts the normal descending inhibitory neurones which leads to exageration of the reflex
Gadolinium can be used to enhance MRI scans of the brain explainn why it is able to enhance the lesions on MRI scans
- Shortens T1 relaxation tme fo nearby water protons in blood
- Doesn’t cross blood brain barrier hence is useful iin detecting disruption to blood brain barrier
- Also used to detect purfusion and blood volume of tumours
Define paralysis
The loss of the ability to move (and sometimes to feel anything) in parts of body
Define quadriplegia
Paralysis of all 4 limbs
Defien paraplegia
Paralysis from waist down
Define ataxia
Imparied voluntary coordination which can therefore affect balance, speech and coordination
Define dyslexia
Learning disability that can cause problems reading, writing and spelling
Define aphasia
Difficulty with language and speech due to brain injury. People with aphasia have trouble reading, writing/typing, speaking and listening
Define rigidity
Body still or inflexible
Define paresis
Slight or incompelte paralysis (muscular weakness caused by nerve damage)
Define hypertonia
Increased muscle tone
Define areflexia
Loss of reflexes
What does the suffix -praxia mean?
Coordination
Define apraxia
Lack of coordination
Define akinesia
Loss or impairment of voluntary movement
Define hemiplegia
Paralysis of one half of body
Define dysarthria
Difficulty speaking e.g. slurred speech due to weakness in muscles controlling speech or difficulty controlling them
Define agnosia
Inability to recgonise objects or persons
Define hyporeflexia
Muscles less responses to stimuli
Define dysdiadochokinesis
Inability to execute rapidly alternating movements
Define spasticity
Increased tension in muscle (causing it to be resistant to stretching)
Define bradykinesia
Slow or difficult body movement
Define palsy
Complete or partial paralysis often accompanied by loss of sensation and involuntary body movements or tremors
Define chorea
Rapid, jerky, involuntary movements especially of limbs and face
Define dysphonia
Impairment of voice (often referred to as a hoarse voice)
What are the 3 “flavours”/”regions” of grey matter in the CNS
- Cortext (brain)
- Nuclei (brain)
- Horns of spinal cord
State the s
What level of the brainstem is this section at?
Midbrain
Label this image of a cross section of the midbrain
What is syringomyelia?
Formatin of fluid filled cyst in spinal cord
