Module Workshops Flashcards
Describe the locations and functional associations of the spinal cord grey and white matter
Grey matter: Contains the cell bodies of neurones
White matter: Contains the myelinated neuronal processes
Outline the changes observed in transverse sections of the spinal cord at different regions
The beginning of the spinal cord is marked by the emergence of the first pair of spinal nerves.
Thoracic region: Increased white matter seen due to the large number of nerves exiting the spinal cord in this region
From T1-L2 a lateral horn is seen - indicates the cell bodies of sympathetic neurones.
Cervical region: The dorsal column medial lemiscus pathway has 2 elevations. Only 1 is seen in the lumbar region (as gracilias cuneatus is for the upper limb)
Outline the function and route of the main descending and ascending tracts
Outline the positions of the ascending and descending tracts within the spinal cord
Describe the arterial supply to the spinal cord.
Clinical link: Outline the potential consequences of blockage to these vessels and how this may be induced
Great radicular artery (Artery of Adamkiewicz): Reinforces blood supply to the distal parts of the spinal cord
Causes of spinal ischaemia: Vertebral fracture; vascultic disease; external compression
Potential consequences
Anterior spinal artery: Loss of descending pathways hence loss of voluntary and involuntary motor movements. Loss of some ascending pathways (spinothalamic and spinocerebellar) leading to loss of pain and temperature sensation alongside reduced co-ordination. Loss of spinal reflexes
Posterior spinal artery: Loss of the dorsal column medial lemniscal pathway, causing loss of fine touch, vibration and unconscious proprioception sensory input.
Describe the autonomic outflow from the CNS
Sympathetic: T1 - L2
- Cell bodies are seen in the lateral horn of the gray matter
- Travel in the sympathetic chain.
3 possible routes:
- Synapse within the paravertebral ganglia. Re-enter the spinal nerve via the gray rami communicantes. Travel to the periphery
- Exits the ganglia without synapsing. Travel with splanchnic nerves to distal ganglia where they then synapse. Post-ganglionic fibres then innervate visceral structures.
- Travel up or down the sympathetic chain.
- Fibres travel from the spinal nerve to the sympathetic chain (paravertebral ganglion) via the white rami communicantes. They are able to re-enter the spinal nerve from the sympathetic chain via the grey rami communicantes.
- Ganglion situated around the body. Tend to closer to the CNS than those to which the parasympathetic fibres travel
Parasympathetic: Cranial nerves (CN V, VII and IX) and S2-S4
- Travel to ganglia
Outline the route taken by the sympathetic nerve supply to the head and neck
Clinical link: Explain Horner’s syndrome and the potential lesion sites
Originate from T1 - T6
Sympathetic fibres travelling to the head and neck exit the spinal nerve and travel to the sympathetic chain via the white rami communicantes.
There are 3 ganglia of the chain related to the head and neck, which are in turn related to specific arteries:
Superior (internal carotid artery); middle (inferior thryoid artery) and inferior (vertebral and subclavian arteries) cerival ganglia.
Sympathetic fibres synapse at these ganglia with post-ganglionic structures continuing to supply the head and neck. These post-ganglionic fibres ‘hitch-a-ride’ with their assoicated arterial vessels.
Horner’s syndrome: Results from loss of sympathetic input to the head. Characterised by ptosis, anyhydrosis and miosis.
Ptosis: Eyelid drooping due to loss of superior tarsal muscle innervation
Miosis: Pupillary contriction due to loss of dilator pupillae innervation
Causes: Spinal cord lesion, traumatic injury, Pancoast tumour (apex of the lung),
Identify and describe the major parts of the eyeball
* Central retinal artery and vein travel in the optic nerve
* Fovea centralis: A area condensed with photoreceptor cells, seen at the centre of the macula. Allows for high visual acuity
* Optic disc: Devoid of photoreceptor cells. Allows the passage of the optic nerve and blood vessels.
* Cornea = a transparent continuation of the sclera
* Conjuctiva: Mucous membrane covering of the eyelid and eye. Maintains moisture
* Ciliary muscles and associated suspensory ligaments: Adjust the convexity of the lens
Describe the movements of the eye and their associated muscles
Clinical link: Describe the clinical testing for these muscles
Clinical testing: Superior/inferior obliques and rectus muscles swap
State and explain the resting position and appearance of the eye with a given injury to CN III, IV or VI
Describe the visual pathway
Describe the different visual field defects that may result due to damage to the visual pathway
* Macula is spared due to its dual blood supply from PICA and the middle cerebral artery
Orbit: Identify component bones, anatomical relations and contents
Outline the innervation of the lacrimal gland and the drainage of secretions
Innervation:
Sensory from lacrimal nerve, a branch of Va
Parasympathetic from greater petrosal (CN VII) → maxillary (Vb) → zygomatic nerve. Stimulates fluid production.
Sympathetic orginate from the superior cervical ganglion and then follow the same route as parasympathetic fibres. Inhibit fluid production.
Drainage: To the nasal cavity via the lacrimal lake → lacrimal sac → nasolacrimal canal
Describe the corneal reflex
Afferent: Nasocoliary branch of the ophthalmic branch of the trigeminal nerve (Va)
Efferent: Temporal branch of the facial nerve (VII)
Elicited by using a wisp of cotton wool to touch the cornea.
Describe the pupillary reflex
***DOES NOT INVOLVE THE PRIMARY VISUAL CORTEX OR THE LGN (THALAMUS)***
Describe the accommodation reflex
Describe the role and relative importance of the cornea and lens in the focusing power of the eye
- The cornea provides the majority of the eyes focussing power, through the refraction of the incidence of light
- The cornea is a continuation of the sclera and is avascular.
- The lens is also able to refract light and may do so to varying degrees through adjustment of its convexity. The lens provides ‘fine tuning’ in the refraction of light.
Describe astigmatism
Resultant of an ‘abnormal’ morphology of the eye which leads to refractive error. The cornea forms a more oval shape (rugby ball), instead of round. This changes the path of light meaning that the visual image is not focussed sharply. This causes blurred vision, headaches and eye strain. In young children a high astigmatism may cause lazy eye.
Treatment: Glasses, contact lenses, laser eye surgery
Describe the mechanism by which the shape of the lens is altered
The shape of the lens is altered by the ciliary muscles (a component of the ciliary body).
Contraction of the ciliary muscles relaxes the suspensory ligaments. The lens increases in convexity, becomes more round and decreases in size. This allows greater refractive power.
Describe the structural abnormalities which lead to myopia and heterometropia (hyperopia)
Myopia:
- Short sightedness
- The distance between the lens and the retina increased causing light to be focussed in front of the retina
- This abnormality can be corrected using a convex/minus lens
Heterometropia:
- Long sightedness
- The distance between the lens and the retina is decreased causing light to be focussed behind the retina
- This abnormality can be corrected using a concave/plus lens
Describe the effect of aging on the lens and how this leads to presbyopia
With the age the lens becomes thickened and hardened, reducing its flexibility/elasticity.
Presbyopia: The increasing long sightenedness associated with aging. Resultant of changes in the elasticity of the lens
Identify the bones of the skull, foramina and sutures
Outline the structures passing through the foramen of the skull and potential consequences of fracture to their component bones or compression of their contents
Pontomedullary junction
Cerebellomedullary angle
Pontomedullary junction: Seen on the ventral surface. Defined by the angle of the lower border of the pons and the upper border of the medulla.
- Origin site of abducens (VI) nerve
Cerebellopontine angle: Formed by the junction of the pons, medulla and cerebellum
- Cerebellar flocculus, ventricular choroid plexus and emerging CNs VII and VIII surround the lateral apertures of the fourth ventricle
- Origin site of facial (VII - motor), nervus intermedius (sensory and autonomic fibres of VII) and the vestibulocochlear nerve (VIII) NOTE: The glossopharyngeal nerve (CN IX) arises from the posteriorlateral sulcus (alongside X and XI)
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Clinical link:
- Often the site of intracranial growths, with initial signs linked to the impingement of CN VIII
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Vestibular schwannomas are the most common growth in the area. They are benign and slow growing but complications arise due to their compression of nearby structures.
- Symptoms: Ipsilateral hearing loss, tinnitus and dysequilibrium (due to CN VIII compression); nystagmus (due to cerebellar flocculus compression). Untreated large tumours will lead to compression of nearby structures, CN V and CN VII (loss of facial sensation, facial expression, reduced corneal reflex)
Identify the lobes of the brain and the principle features of cerebral hemispheres
List the main features and function of the brain stem
Describe the main functions of the thalamus and be able to identify its key anatomical relations
Functions:
- A relay station for the distribution of sensory information with nearly all sensory information passing through the thalamus, allowing thalamic nuclei to send sensory fibres to the cortex.
- EXCEPTION: Olfaction (via CN I) does not pass through the thalamus. This sensory information is sent to the temporal lobe. Linked to embryological origin (from telecephalon)
- Relays information from the ipsilateral cerebral cortex to the outside world via cortico-fugal neurons
Key anatomical relations:
- Lateral to the 3rd ventricle
- Medial to the internal capsule
- Posterior to the caudate nucleus
- Superior to the sub- and hypothalamus
- Rostral to the midbrain
Outline the structure and functions of the following neurones:
- Pseudounipolar
- Bipolar
Pseudounipolar: A sensory neurone of the peripheral nervous system. The axon is split into 2 branches, with one running to the periphery and the other to the spinal cord.
Bipolar: Has 2 extensions, 1 axon and one dendrite. Act as specialised sensory neurones for the transmission of special sensory information - smell, sight, taste, hearing and vestibular system e.g. the ganglia of the vestibulocochlear nerve and the bipolar cell of the retina.
State the thalamic nuclei and outline their functions
State the visual defect that would be experienced following a lesion at the sites indicated
Complete the sensory receptor table
Outline the structure of the Dural venous sinuses
Draw diagram - state location
This sinuses are formed at the sites of separation between the periosteal and meningeal Dura matter. The venous blood contained within the sinuses eventually drains into the internal jugular vein.
State the key anatomical sites of the tongue
Draw diagram
Outline the sensory and special sensory supply to the tongue
State the processes associated with the TMJ and the process responsible for articulation at the joint
Identify and describe the lobes of the brain and the functional associations of each lobe
Identify the main features of cerebral hemispheres on transverse and coronal sections
Outline the contributors and components of the vertebrobasilar arterial system and circle of Willis
Describe the parts of the brain supplied by branches of the vertebrobasilar arterial system
Draw transverse and coronal sections
Outline the consequences of loss/blockage of blood supply to areas of the brain
Identify the main anatomical features of the oral cavity and submandibular region
Describe the anatomy of the tongue and outline its sensory, motor and taste nerve supply
Outline the presentation of an UMN and LMN lesion of CN VII, explain why the presentation is different (referring to neural pathways)
UMN: Forehead sparing, due to bilateral innervation of the forehead, with contralateral paralysis of the lower face.
LMN: Ipsilateral forehead and lower face paralysis
Identify and describe the muscle groups and nerves responsible for chewing, swallowing and speaking
Describe the basic anatomy, location, relations and innervation of the salivary glands
Identify the cranial nerves originating from different levels of the brain stem
Describe the structure and basic function of the cochlea
Draw diagram
Describe the pathway of fibres from the cochlea to the primary auditory cortex
Draw pathway
Describe how the dynamic labyrinth can bring about automatic eye movement, specifically horizontal conjugate gaze only
Draw pathway
☆ The MLF (medial longitudinal fasciculus) is crucial for conjugate eye movement - lesions lead to loss of conjugate movement (intranuclear opthalmoplegia - seen in MS)
Outline the potential range of symptoms associated with damage/disease of the vestibular system and explain the basic mechanism surrounding each
Identify and describe the basic anatomy of the cerebellum
