Extra Neuro Flashcards
Where are muscle spindles found?
Fibres within hidden within the contractile fibres (intrafusal)
What are muscle spindles innervated by?
Gamma motor neurons
What is a muscle spindle?
Stretch receptors that are wrapped round intrafusal muscle fibres (within the muscle)
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 do golgi tendon organs measure?
Mechanoreceptors that measure changes in tension of a muscle.
What nerve fibres innervate golgi tendon organs?
Afferent type 1b sensory nerve fibres (inhibitory).
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 is a LMN?
A neurone that carries signals to effectors. The cell body is located in the brain stem or spinal cord.
What is an UMN?
A neurone that is located entirely in the CNS. Its cell body is located in the primary motor cortex.
What are the signs of UMN weakness?
- Increased muscle tone.
- Hyper-reflexia.
- Spasticity.
- Minimal muscle atrophy.
What are the signs of LMN weakness?
- Decreased muscle tone.
- Hypo-reflexia.
- Flaccid.
- Muscle atrophy.
- Fasciculations.
Define a Motor pool
All the lower motor neurones that innervate a single muscle
* The motor pool contains both the alpha and gamma motor neurons (see later) * Motor pools are often arranged in a rod like shape within the ventral horn of the spinal column
What do medial alpha neurones (near the spinal chord supply)
Proximal muscles
What do lateral alpha neurones supply
distal muscles
Define motor unit
an alpha neurone and all the extrafusal skeletal muscle fibres it innervates
What does it mean if a motor unit has a small amount of muscle fibres?
Where would you see this?
it allows for greater movement resolution, as there is a greater variation of movement
In the finger tips or tongue
Where do first order neurones for the olfactory nerve synapse?
in the olfactory bulb
Where is the degree of pain judged?
in the insula
Where is the emotional response to pain generated?
The cingulate gyrus
What is a collection of cell bodies called in the
a CNS?
b PNS
a Nucleus
b Ganglion
What is a collection of axons called in the
a CNS?
b PNS
a Tract
b Nerve
What neuroens are mylinated?
A and B fibres
What the differnece between A and B fibres? (they are both mylinated)
A is THICK
B is THIN
A transmission speed is 100m/sec
B transmission speed is 10m/sec
What kind of fibres are unmylinated?
C fibres, they are very thin
Their transmission speed is 1m/sec
what makes up myelin in the
a CNS
b PNS
CNS - Oligodendrocytes
PNS - Schwann Cells
In the spinal chord, what is conveyed in the
a VENTRAL ROOT/RAMUS
b DORSAL ROOT/RAMUS
Ventral root - Motor, efferent
Dorsal Root - Sensory, afferent
What can the motor branches either be?
Autonomic (can be sensory or motor)
or Somatic
Will somatic nerves relay in a Ganglia ?
no. it will go straight to whatever it innervates
Because they have to be fast
This is why they use A fibres
Will Autonomic nerves relay in a ganglia?
Yes. Fibres before it are known as pre ganglionic, fibres after are known as post ganglionic
(they are distribution centres for regulation. One nerve eg Vagus can split and supply different regions of the stomach, for example)
because of this however, they aren’t as fast
Do we have more somatic or autonomic fibres in our bodies? Why
Have more somatic, so we can carry out more fine movements
What fibres does the autonomic system use?
B and C fibres.
They are slower than A fibres
Autonomic and somatic - which came from lateral horn and which came from the anterior horn
Autonomic - lateral horn
Somatic - Anterior horn
What neurotransmitter do preganglionic fibres secrete?
Always Acetylcholine
What neurotransmitter do post ganglionic fibres secrete?
It depends
Parasympathetic - Acetylcholine
Sympathetic -
Noradrenaline
(—> Exception for sympathetic postganglionic is sweat glands. - They secrete Ach )
What do microglia do?
Primary defence of the CNS
They are the resident macrophage of the brain and spinal chord
Remove things like Damged neurons, pathogens etc
Astrocytes are a type of Macroglia. What is the role of Astrocytes?
Provide Nutrient support to neurones
Regulating Communication between neurons
Help repair damaged neurons
Form part of and maintain the blood - brain barrier
Astrocytes are a type of Macroglia. What is the role of Ependymal cells?
They are found in the ventricles, and produce cerebrospinal fluid, that has many roles such as protecting the brain from injury and removing waste products from the brain.
Radial Glia are a type of Macroglia. What is the role of Them?
they are involved in neurogenesis, and help new neurons travel through the brain
What is the indirect pathway of the Basal ganglia? For stopping movement
Striatum =(Which excites)=> External Globus Pallidus =(Which Inhibits)=> The Subthalamic nucleus =(which Inhibits)=> Internal Globus Pallidus =(which Inhibits)=> Thalamus =(which Inhibits)=> The cerebral cortex
So one excitatory and then 4 inhibitory
Striatum, External Globus Pallidus, Subthalamic Nucleus, Internal Globus Pallidus, Thalamus, Classroom
Sam’s Extremely Stupid In The Classroom.
What is the Direct pathway of the Basal ganglia? For initiating movement -
Cerebral cortex.
Then: Striatum =(Inhibits)=> Internal Globus Pallidus =(Inhibits)=> Thalamus (double inhibition means thalamus is excited) so Thalamus can excite the cerebral cortex == Movement
Sam Is Terribly Confused =
Striatum, Internal Globus Pallidus, Thalamus, Cerebral Cortex
What are the DCML pathways responsible for?
These are responsible for FINE TOUCH AND TACTILE SENSATION, VIBRATION, PROPRIOCEPTION etc.
What is the DCML pathway for the
a Upper limb Above T6
b Lower limb below T6
Signals from the lower limb (below T6) tend to travel in the Fasciculus Gracilis
(so they then Synapse in the Gracile Nucleus of the Medulla)
Signals from the upper limb (above T6) tend to travel in the Fasciculus Cuneatus
(so they then Synapse in the Cuneate Nucleus of the Medulla)
*graciLis = L for Leg of Lower Limb
Fasciculus Gracilleus is more medial than fasciculus Cuneatus
describe the DCML pathway
- Afferent signals are carried along first order neurones to and up the Dorsal columns (from proprioception receptors) to then synapse in the medulla.
- 2nd order Neurones then DECUSSATE IN THE MEDULLA and travel up to the THALAMUS where they synapse again.
- 3rd order neurones then travel through the internal capsule to the somatosensory cortex in the Parietal mode (postcentral gyrus)
what would be seen in damaged to the DCML pathways at the spinal chord ?
They are at medial and at the back of the spinal cord.
THESE TRACTS RUN IPSILATERALLY THROUGH THE SPINAL CORD AND DECUSSATE IN THE MEDULLA OF THE BRAINSTEM = so damage to spinal cord here would lead to loss of Ipsilateral fine touch, tactile sensation, proprioception etc.
What is the anterior spinothalamic tract responsible for?
Crude touch/ or pressure
What is the lateral spinothalamic tract responsible for?
responsible for Pain and temperature
Where do Spinothalamic and Dorsal Column medial lemniscal pathway synapse in the thalamus?
The Ventral Posterio-lateral division of the nucleus of the thalamus
Where do the Spinothalamic and Spinoreticular tracts decussate?
These pathways Decussate within the spinal cord and travel up to the brain
A nerve entering the Anterior lateral pathways tend to travel up 1 or 2 vertebral levels before Decussating
So lesion of the spinal cord will cause a contralateral loss of pain, crude touch, sensation (Generally speaking),
What do the Spinocerebellar and Spinoolivary tracts carry?
Carry Unconscious sensation, specially involved in transmitting Proprioceptive information from the LOWER limbs UP TO THE IPSILATERAL CEREBELLUM
SENOSRY, ASCENDING
What do the CUNEOCEREBELLAR AND ROSTRAL SPINOCEREBELLAR TRACTS carry?
Carry Unconscious sensation, specially involved in transmitting Proprioceptive information from the Upper limbs and neck UP TO THE CEREBELLUM
Both convey through the INFERIOR CEREBELLAR PEDUNCLE
What might be seen in someone with cerebellar damage?
Dysdiadochokinesia - inability to perform rapidly alternating movements
Ataxia - Disorders that affect balance, speech and coordination
Nystagmus - Abnormal eye movements
Intention tremor - tremor when moving
Slurred speech
Hypotonia - Abnormally low muscle tone
What are the two descending Pyramidal tracts?
What do they do?
PYRAMIDAL TRACTS: ANTERIOR AND LATERAL CORTICOSPINAL AND CORTICOBULBAR TRACTS (pass through the pyramids of the Medulla
Carry signals down from the brain involved in Voluntary Movement
What does the corticospinal tract split into? what do these tracts do?
lateral and anterior corticospinal tracts.
Lateralcoritcospinal tract comprised of Decussated fibres (cross at the medulla) , so operate contralaterally. = (controls the limbs and digits)
Around 90% of fibres Decussate in the Medulla (lateral corticospinal tract) and 10% don’t, forming the Anterior corticospinal tract = (controls Trunk, shoulder, neck muscles - AXIAL MUSCLES)
Fibres from the anterior corticospinal tract only decussate at the level of spinal nerve in which they exit
What does the corticobulbar tract do?
What has bilateral innervation and what has contralateral innervation? What does this mean?
Innervates skeletal muscle of head and neck, via the cranial nerves
So 5 and 11 (and upper face motor part of 7) = Bilateral
12 and lower face motor part of 7 = 7 Contralateral
Bilateral - receive signals from both hemispheres of the brain
Contralateral - decussate at the brainstem so only Contralateral innervation from contralateral side of Cerebral hemisphere
Extrapyramidal tracts: What of these tracts decussate?
Rubrospinal tract - provides contralateral innervation for fine motor control
Originate in the RED NUCLEUS , and decussate immediately.
Tectospinal tracts = involved in coordination of head movements with vision.
Arise in the tectum, Superior and Inferior Colliculi
Extrapyramidal tracts: What of these tracts remain ipsilateral?
What do they do?
Medial Reticulospinal tract- FACILLITATES voluntary Muscle contraction, increase Muscle tone -
Lateral reticulospinal tract: INHIBITS VOLUNATRY MOVEMENT, reduce muscle tone,
and plays are role in ATUOMATIC BREATHING - STARTS IN THE PONTINE RETICULAR NUCLEI - nb Both Contra and Ipsiateral
Vestibulospinal tracts = Helps control balance and posture - STARTS IN THE LARGE VESTIBULAR NUCLEI IN PONS AND MEDULLA
What is the fluid called that fills the labyrinth?
Perilymph
what is the
a ascending portion of the cochlea
b descending portion
a) Scala vestibuli
b) Scala tympani
Vestibuli on top!! Not alphabeticalv decent
Tonotopic organisation: Where do lower frequencies produces vibrations on the cochlear?
the apex ( or higher up ) of the cochlear
Tonotopic organisation: Where do Higher frequencies produces vibrations on the cochlear?
The base of the cochlear
What is the Rubrospinal tract involved in ?
Arises from red nucleus
Fibres decussate and then descend
Plays a role in fine control of hand movement
What is the Reticulospinal tract involved in ?
Medial tract arises from the pons Facilitates voluntary movements Increases muscle tone Lateral tract arises from medulla Inhibits voluntary movement Reduces muscle tone
What is the vestibulospinal tract involved in?
Vestibulospinal tract: Arise from vestibular nuclei Medial and lateral tracts Supply ipsilateral information Controls balance and posture
Doenst decussate
where do the extrapyramidial tracts originate from?
What extrapyramidal tracts decussate?
Originate in brainstem
4 in total
Rubrospinal and tectospinal decussate – others don’t
What arteries supply brocas area? What Broddman area
Middle cerebral artery
Area 44
What arteries supply Wernickes area? What Broddman area
Middle cerebral artery
Area 22
What CN control which parts of the pupillary light reflex?
Afferent - Optic Nerve
Efferent - Oculomotor nerve (parasympathetic)
What layer does neural tissue come from?
Ectoderm
In a hemi section of the spinal chord, would spastic paresis occur contralaterally or ipsilaterally?
Ipsilaterally, as it would be due to the corticospinal tract, which is doesn’t decussate in the spinal chord
