Neuro Flashcards
What muscles can change the stiffness of the ossicular chain?
Stapedius and tensor tympani.
Name 4 cerebellar nuclei.
- Dentate.
- Emboliform.
- Globose.
- Fastigial.
where is the primary motor cortex?
pre-central gyrus
Which of the cavities of the cochlea are filled with perilymph?
Scala vestibuli and scala tympani.
where does venous blood exit the cranium?
jugular foramina
other name for primary motor cortex?
Brodmann’s Area 4
what comes before the relative refractory period?
the absolute refractory period
What are the anatomical divisions of the nervous system?
The CNS (brain and spinal cord) and the PNS (cranial nerves and spinal nerves).
- What does Cn2 innervate?
- What are it’s functions?
- Innervates: retina.
- Function: vision.
Define axonal transmission.
Transmitting information from A to B.
Where do sympathetic nerves come from?
T1 -> L2 spinal nerves.
- What does Cn4 innervate?
- What are it’s functions?
- Innervates: superior oblique.
- Functions: movement of eyeball.
What are the vestibular apparatus?
- Otolithic organs: utricle and saccule.
2. 3 Semi-circular canals.
Describe the I’MAuditory pathway.
Inferior colliculi -> inferior brachium -> medial geniculate body.
- Concerned with the reflex of looking towards a loud noise.
What is the cauda equina?
Spinal nerves from the lower spinal cord that hang obliquely downwards.
What are the signs of UMN weakness?
- Increased muscle tone.
- Hyper-reflexia.
- Spasticity.
- Minimal muscle atrophy.
What do the middle cerebellar peduncles convey?
They send information from the primary motor cortex about the motor plan to the cerebellum - corticopontocerebellar tract.
What tracts are known as the dorsomedial system?
DCML.
What is the action(s) of medial rectus on the eyeball?
- Adduction.
Where do the two optic nerves meet?
At the optic chiasm. The images from the two eyes are fused here.
What is the peripheral nervous system?
The nervous system outside the brain and spinal cord. It includes the cranial nerves (except 1 and 2) and the spinal nerves.
- What does Cn1 innervate?
- What are it’s functions?
- Innervates: olfactory epithelium.
- Function: olfaction.
What tracts are known as the ventrolateral/anterolateral system?
Spinothalamic tracts.
- What does Cn6 innervate?
- What are it’s functions?
- Innervates: lateral rectus.
- Function: eye movement, abduction.
where do the fibres of the vestibulospinal tract decussate?
they dont
What nerve fibres innervate golgi tendon organs?
Afferent type 1b sensory nerve fibres (inhibitory).
What week does the neural tube fuse?
Week 4.
What does the metencephalon form?
- Cerebellum.
- Pons.
What is the function of microglia?
They are the immune cells of the CNS - phagocytic and immune surveillance.
What lies beneath the arachnoid mater?
The subarachnoid space containing CSF and arteries.
Where do the purkinje cell axons go to?
Most go to the dentate nucleus. They then pass into the superior cerebellar peduncle to decussate, and then travel to the thalamus and the red nucleus.
where does the external jugular vein receive blood from?
exterior of the cranium, deep parts of the face
What neurones innervate muscle spindles?
Gamma motor neurones.
What are the characteristic features of MS?
MS comes and goes and its symptoms are exacerbated after having a shower.
What do the two vertebral arteries form?
The basilar artery.
What is the conus medullaris?
The tapered, lower end of the spinal cord.
What does the telencephalon form?
- The cerebral hemispheres.
A 30-year-old woman noticed that her face had become progressively droopier whilst putting her make-up on in the mornings. Weeks later she began to experience double vision, and found it progressively more tiring and difficult to chew all the food in her mouth when eating. What is the problem?
Myasthenia Gravis (characterised by progressive weakness and tiredness. Actions like chewing become much harder. It is a neuromuscular junction disease where the Ach receptors are blocked).
where does the rubrospinal tract decussate?
medulla
What is an endorphin?
A peptide with opiate like effects. They inhibit the release of substance P.
What does the mesencehpalon form?
- Midbrain.
- Colliculi.
How do somatic motor neurones differ from autonomic motor neurones?
Somatic motor neurone leaves the spinal cord and synapses straight onto the effector. Autonomic motor neurones have a pre-ganglionic and post-ganglionic component and so synapse at the ganglia and then at the effector.
which tract carries pain sensation?
lateral spinothalamic tract
What does the anterior cerebral artery supply?
The medial aspect of the hemispheres and the corpus callosum.
What sensations does the spinothalamic pathway convey?
- Lateral spinothalamic - pain and temperature.
- Anterior spinothalamic - crude touch.
Briefly describe the pathway of afferent pain transmission.
Nociceptors, A delta and C fibres, synapse with secondary afferent neurones in the dorsal horn of the grey matter. Substance P is released. Interaction amongst afferent neurones and interneurones determines the activity of secondary neurones. The signal is carried via the spinothalamic tract to the thalamus. Third order neurones then ascend to the somatosensory cortex.
What is the effect of stimulating opioid receptors?
It can reduce neuronal sensitivty and so reduce the pain sensation.
- What are the functions of Cn9?
- Sensory functions: general sensation, taste, chemo/baroreception.
- Motor functions: Swallowing (larynx and pharynx are elevated).
- Parasympathetic function: salivation.
What does the myelencephalon form?
- Medulla oblangata.
What site does brain stimulation affect?
Sub-thalamic nucleus.
What sensations is the lateral spinothalamic tract responsible for?
Pain and temperature.
Give 3 functions of the cranial meninges.
- Protects the brain and spinal cord form injury.
- Provides a framework for cerebral and cranial vasculature.
- Provides a space for the flow of CSF.
Where is the falx cerebelli located?
Between the 2 lobes of the cerebellum.
What sensation is the anterior spinothalamic tract responsible for?
Crude touch.
A 30-year-old man presents with increased muscle tone, brisk reflexes and fasciculations. Which spinal tract is likely to be affected?
Corticospinal (UMN and LMN weakness).
Are there any synapses within the descending pathways?
No. At the termination of the descending tracts, the neurones synapse with a lower motor neurone. (All the neurones within the descending motor system are UMNs).
What is the dermatome for the thumb?
C6.
function of the tectospinal tract?
controls head turning to visual stimulus
What are the two types of deafness?
- Conductive - sound is blocked from getting through.
2. Sensory neural - the problems are with the nerves.
What is the ventral stream?
The ‘what’ stream. It is thought to be involved in identification and recognition. It travels through the temporal lobe.
if damaged, cn1 will cause what
anosmia on the ipsilateral side
What is the potential of the scala media?
+80mV.
Briefly describe the stretch reflex.
The muscle is stretched and intrafusal muscle fibres are stimulated -> sends afferent impulses along 1a neurones -> alpha motor neurone -> efferent impulses to extrafusal muscle fibres -> contraction.
where does the internal jugular vein receive blood from?
brain, superficial parts of the face and the neck
What is the function of myelin?
Insulates and allows rapid conduction of action potentials along an axon.
Describe the corticobulbar tracts.
Originate in the primary motor cortex, descends through corona radiata and internal capsule to the brainstem. The fibres terminate on motor nuclei of cranial nerves. They synapse with LMN’s which carry motor signals to the face and neck.
What are the 3 cavities of the cochlea?
- Scala vestibuli.
- Scala media.
- Scala tympani.
Where do the vestibulospinal tracts originate and what are they responsible for?
- Originate from vestibular nucleus.
- Responsible for muscle tone and postural control.
- Remains ipsilateral.
What embryonic part of the brain is the medulla oblangata formed from?
Myelencephalon of Rhombencephalon.
does CN1 have afferent, efferent or both components?
afferent (sensory only)
Which arteries supply about 80% of blood to the brain?
The internal carotid arteries.
What is voluntary motor control?
Goal directed (conscious) or habitual (unconscious/automatic). E.g. running, walking talking etc.
Describe A delta fibres.
- Small nerve fibres but larger than C fibres.
- Thinly myelinated.
- They have a high activation threshold.
What is the function of the limbic system?
The limbic system is involved with emotion, behaviour, long-term memory, olfaction and motivation. It is also thought to have a role in learning.
what innervates extrafusal muscle fibres?
alpha motor neurones
Where in the thalamus do the DCML and spinothalamic tracts synapse?
In the ventral posterio-lateral division (VPL) of the nucleus of thalamus.
What is the action(s) of inferior rectus on the eyeball?
- Depression.
- Extorsion.
- Adduction.
What is myasthenia gravis?
An autoimmune disease; antibodies destroy Ach receptors.
Which lobes of the brain does the loop of optic radiation responsible for the lower visual field travel through?
Travels through the parietal lobes.
Name 4 disorders associated with basal ganglia dysfunction.
- Huntington’s disease.
- Parkinson’s disease.
- ADHD.
- OCD.
What is the function of the ossicles?
To transmit vibrations from the tympanic membrane to the oval window.
What is the function of the cerebellum?
Precise control, fine adjustment and coordination of motor activity based on continual sensory feedback. The cerebellum decides HOW you do something. It computes motor error and adjusts commands and projects it back to the motor cortex.
where are golgi tendon organs situated?
at the junction of a skeletal muscle and a tendon
Approximately how much CSF do we have?
120ml.
What structures connect adjacent stereocilia?
Tip links.
what do extrafusal muscle fibres do?
contract muscles
What would be the affect of damage to the cerebellar vermis?
Balance problems due to loss of postural control. Difficulty in sitting and standing up.
what does the reticulospinal tract do?
acts to facilitate or inhibit the activity of various descending tracts
What nerve provides sensory innervation to the nasopharynx?
Maxillary branch of the trigeminal - Cn 5(b).
what do muscle spindles detect?
muscle relaxation and extension
Name the 3 elements that make up the blood-brain barrier.
- Capillary endothelial cells.
- Basement membrane.
- Astrocytic end-feet.
- What is the name of Cn2?
- Where does it exit the skull?
- Sensory, motor or both?
- Optic.
- Optic canal (ethmoid bone).
- Sensory.
What are the functional divisions of the nervous system?
Somatic (voluntary control) and autonomic (involuntary control, further subdivided into sympathetic and parasympathetic).
where does the tectospinal tract originate?
superior colliculus
what innervates the skeletal muscle?
alpha motor neurones = extrafusal = skeletal
the middle one third of the spindle is associated with which sensory nerves?
type 1a afferent sensory nerves
Name 4 ascending spinal pathways.
- DCML.
- Spinothalamic.
- Spinocerebellar.
- Spinoreticular.
What occular muscle does Cn 4 innervate?
Superior oblique.
Mutation of what protein can result in duchenne?
Dystrophin.
What are the sub-divisions of the prosencephalon?
- Telencephalon.
- Diencephalon.
What nerve provides general sensation to the outer ear?
Cn 10.
What do the superior cerebellar peduncles do?
They connect the midbrain and the cerebellum and carry mostly efferent fibres.
Where are dural venous sinuses located?
In between the endosteal and meningeal layers of dura.
how does cn1 enter the cranial cavity
via small holes in the cribiform plate of the ethmoid bone
What would pouring ice cold water in the external auditory meatus cause?
Convection currents in the semi-circular canals which results in nystagmus.
What do the semi-circular canals detect?
Angular acceleration.
- What is the name of Cn1?
- Where does it exit the skull?
- Sensory, motor or both?
- Olfactory.
- Cribriform plate of ethmoid bone.
- Sensory.
% of fibres in the lateral vs anterior corticospinal tracts?
85% lateral
15% anterior
Withdrawal reflex: what does reciprocal innervation of antagonistic muscles explain?
It explains why the contraction of one muscle induces the relaxation of the other; this permits the execution of smooth movements.
What is the role of the insula in pain recognition?
The insula contributes to the subjective perception of pain. It is where the degree of pain is judged.
A man is feeling very distressed as he woke up being unable to feel the right side of his face and his right arm and leg. What lobe is affected?
The parietal lobe (somatosensory cortex). Feel is the key word here.
What is the action(s) of superior oblique on the eyeball?
- Intorsion.
- Depression.
- Abduction.
what does the anterior corticospinal tract do?
controls muscles of the trunk
Define pain.
An unpleasant sensory and emotional experience associated with actual tissue damage.
where do the axons of lower motor neurones terminate?
on an effector/ muscle
What nerve innervates tensor tympani?
Cn 5.
What nerve provides general sensation to the middle ear?
Cn 9.
What structures lie anteriorly to the cerebellum?
The pons and medulla. The 4th ventricle lies in between these and the cerebellum.
Where are Cn 1 nuclei located?
Olfactory bulb.
What is a berry aneurysm?
A sac-like out pouching that will progressively enlarge until it ruptures resulting in haemorrhage.
Where is the insula located?
Deep in the lateral sulcus.
What occular muscles does the superior branch of Cn 3 innervate?
- Levator palpebrae superioris.
- Superior rectus.
What spinal nerves innervate the biceps reflex?
C5/6.
name the two types of lower motor neurone
alpha and gamma motor neurones
What is the helicotrema?
Where the scala vestibuli and scala media meet.
what innervates the spindle muscle fibres?
gamma motor neurones = intrafusal = spindle
Where do cerebral veins drain into?
Into dural venous sinuses.
What are the 3 structures that make up the organ of corti?
- Hair cells.
- Supporting cells.
- Auditory nerve fibres.
what does the vestibulospinal tract do?
controls muscles involved in balance and posture
Where is a berry aneurysm likely to occur?
At branching points in the circle of willis, especially at the anterior communicating artery.
What do golgi tendon organs measure?
Mechanoreceptors that measure changes in tension of a muscle.
What is the response of golgi tendon organs if they detect a change in tension?
They inhibit alpha motor neurones to prevent muscle contraction if the force gets too great.
What would be the signs of a complete spinal cord lesion?
- Weakness in all muscle groups below the lesion.
- Complete sensory loss below lesion.
- Spasticity and hyperreflexia.
which part of the muscle spindle is contractile?
the two ends are contractile
What do the inferior cerebellar peduncles convey?
Ipsilateral muscle proprioception, balance and vestibular inputs - vestibulocerebellar tract and dorsal spinocerebellar tract. Also fibres from inferior olivocerebellar tract.
What is the dorsal stream?
The ‘where’ stream. It is thought to determine the objects spatial location. It travels through the parietal lobe.
What 3 bones make up the ossicular chain?
Malleus, incus and stapes.
Where do the optic tracts terminate?
Lateral geniculate body in the thalamus.
What descending pathways are described as extrapyramidal?
Vestibulospinal, rubrospinal, tectospinal, reticulospinal - responsible for involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion.
where is CSF reabsorbed?
into the superior sagittal sinus
What nerve innervates stapedius?
Cn 7.
where do the fibres of the the dorsal column-medial lemniscal system decussate?
at the medulla
What is the reason behind the signs of PD?
Not enough dopamine.
What would be the affect on the visual field if there was a complete lesion of the left optic nerve?
Total left eye blindness.
Is the base or the apex of the basilar membrane more sensitive to high frequency sounds?
The base.
Where does the spinothalamic tract decussate?
Within the spinal cord, 2-3 spinal segments above.
Where do parasympathetic nerves come from?
Cn 3, 7, 9 and 10, S2 -> 4.
What is the papez circuit?
A circuit that connects the main structures of the limbic system. It is involved in memory and emotions.
What is the action(s) of lateral rectus on the eyeball?
- Abduction.
Describe C fibres.
- They are the smallest nerve fibres.
- Unmyelinated and so have slow conduction speeds.
- They have a high activation threshold meaning they detect selectively nociceptive stimuli.
How is the neuronal resting potential maintained?
3Na+ are pumped out of the cell for every 2K+ pumped in. This process requires ATP. There are many Na+/K+ transport pumps.
What efferent signals do the superior cerebellar peduncles convey?
Efferent signals from the dentate nucleus that go to the red nucleus and thalamus.
Do the finger tips have lots of muscle fibres or few muscle fibres?
Few muscle fibres. This allows for greater movement resolution.
where are muscle spindles found?
in skeletal muscles
where does the reticulospinal tract originate?
from cells found in the pons and medulla
Define dermatome.
An area of skin with a sensory nerve supply from a single root of the spinal cord.
Where is the straight sinus located?
In the midline of the tentorium cerebelli.
What is the smallest bone in the human body?
The stapes.
What are the signs of parkinson’s disease?
- Tremor.
- Bradykinesia.
- Rigidity.
What is the function of the vestibular hair cells?
They detect changes in motion and position of the head by stereocilia transduction.
- What is the name of Cn6?
- Where does it exit the skull?
- Sensory, motor or both?
- Abducens.
- Superior orbital fissure.
- Motor.
What is the origin and insertion of levator palpebrae superioris?
Origin: common tendinous ring.
Insertion: Upper eyelid.
- What is the name of Cn11?
- Where does it exit the skull?
- Sensory, motor or both?
- Accessory.
- Jugular foramen.
- Motor.
Name 3 locations where the dura mater folds inwards as dural reflections?
- Falx cerebri.
- Tentorium cerebelli.
- Falx cerebelli.
What neurones innervate muscle fibres.
Alpha motor neurones.
What are the functions of rods in the eye?
Rods are important for peripheral vision.
You are carrying out an eye examination on a patient who is looking at the tip of your nose. Behind you, on your left hand side, is a tall medical student. What would be the patients’ retinal representation of the image of this students’ face?
The retinal image is converted from right to left and reversed. The students face is now in left lower corner.
(Medical student is stood on your left but that is the patients right).
What is the dermatome for the big toe?
L5.
What sinuses form the confluence of sinuses?
The straight sinus and the superior sagittal sinus.
Where is the majority of CSF produced?
In the lateral ventricles (greatest amount of choroid plexus here`).
A 40-year-old removal man felt immediate back pain and a popping sensation after lifting a heavy box. The next day he noticed he was tripping over his right foot as it was dragging along the floor. What is affected?
Lower motor neurones (he has a slipped disc. The LMN nerve roots coming out of the spinal cord have been damaged).
What does the diencephalon form?
- Thalamus.
- Hypothalamus.
What is involuntary motor control?
Eye movements, facial expressions, posture, diaphragm etc.
What does the middle cerebral artery supply?
The lateral surface of the hemispheres.
A patient is diagnosed with a lesion to Cn 3, how would the eye appear to the examiner?
‘down and out’ due to unopposed action of lateral rectus and superior oblique.
how are fibres in the dorsal columns arranged?
topographically
Where is the tentorium cerebelli located?
The tentorium cerebelli is a thick fibrous roof lying over the posterior cranial fossa and the cerebellum.
Where is the 3rd ventricle formed in the embryo?
Diencephalon.
What do neural crest cells develop into?
Schwann cells, pigment cells, adrenal medulla, dorsal root ganglia, Cn 5, 7, 9 and 10.
What sensations does the DCML pathway convey?
Fine touch, 2-point discrimination and proprioception.
What do the middle cerebellar peduncles do?
They connect the pons and the cerebellum and they ‘tell’ the cerebellum about voluntary motor outputs.
