Nervous System Flashcards
What is the parasympathetic supply to the enteric system?
The enteric nervous system contains preganglionic cholinergic vagal fibres
In the enteric nervous system, are vagal fibres post-ganglionic?
No, pre-ganglionic
In the enteric nervous system, does it contain post-ganglionic sympathetic fibres?
Yes.
The sympathetic supply is post ganglionic but may end on cholinergic neurones or smooth muscle fibres directly.
Where does the enteric nervous systems sympathetic fibres end on?
Cholinergic neurones or intestinal smooth muscle fibres directly
Which type of nerve fibres are the fastest?
A and B fibres are myelinated and conduct via saltatory conduction, so have fast conduction velocities
Are C-fibres myelinated?
No
What speed do A-alpha fibres conduct at?
70 - 120m/s
What type of fibres supply motor supply to muscle spindles?
A-gamma fibres
What does Brown-Sequard syndrome cause?
This is hemisection of spinal cord.
Causes:
- ipsilateral paralysis
- ipsilateral loss of proprioception
- ipsilateral touch + vibration sensation
- contralateral loss of pain
- contralateral loss of temperature sensation
How big is the synaptic cleft?
30-50 nm wide
What type of summation do excitatory postsynaptic potentials exhibit?
Temporal or spatial
How long is synaptic delay?
0.5ms
What are IPSPs? (inhibitory post synpatic potentials)
Hyperpolarising
What are EPSPs? (excitatory post synaptic potential)
Depolarising
How many synapses does the knee jerk reflex have?
It is monosynaptic
What is the synaptic transmitter at the knee jerk reflex?
Glutamate
What is the sensory organ in the knee jerk reflex?
The muscle spindle
What spinal roots does the knee jerk reflex involve?
L2,3,4
How does the knee jerk reflex work?
The sensory organ is the muscle spindle, which when stretched sends signals to the CNS where a single synapse occurs with the motor supply to the muscle. In addition the Ia fibre from the muscle spindle synapses with an inhibitory interneurone (golgi bottle neurone) which releases inhibitory glycine at the motor neurone to the antagonistic muscle - known as reciprocal innervation.
What happens to fibres in the antagonistic muscles in the knee jerk reflex?
Glycine inhibition
The Ia fibre from the muscle spindle synapses with an inhibitory interneurone (golgi bottle neurone) which releases inhibitory glycine at the motor neurone to the antagonistic muscle. Reciprocal innervation.
What do optic tract lesions cause?
Homonymous hemianopia
(optic tract carries fibres that supply the same field (ie left or right) from both eyes)
What do optic chiasm lesions cause?
Bitemporal hemianopia
(at the optic chiasm temporal fibres cross the midline)
Why do occipital lesions spare the macula?
The macula fibres are separated from the rest of the cortex subserving vision
What do optic nerve lesions cause?
Unilateral loss of vision
What do visual field defects start as?
Scotomas - small areas of visual loss
Where are the cell bodies of the A-delta fibres?
Dorsal root ganglia
Where do A-delta fibres synapse?
With cells in laminae I and V of the dorsal horn
Where do C fibres synapse?
Cells in laminae II and III in the dorsal horn
Which column are most ascending neurones in?
The anterolateral columns (spinothalamic tract)
Most second order neurones cross within a few segments and ascend in the anterlateral columns.
What does the substantia gelatinosa do?
It does not project directly to higher levels but contains multiple interneurones involved in pain modification.
What are Meissners corpuscles associated with?
Touch
What are Ruffini corpuscles associated with?
Proprioception
What are Pacinian corpuscles associated with?
Vibration and proprioception
What are free nerve endings associated with?
Nociception
What cranial nerve supplies taste sensation?
The posterior 1/3 of tongue is glossopharyngeal (IX) and the rest is the chorda tympani accompanying the facial nerve (VII)
What does the trigeminal nerve supply?
Muscles of mastication and sensation to forehead and face in distribution of opthalmic, maxillary and mandibular branches.
Includes sensation from cornea.
What muscle does cranial nerve IV (trochlear) innervate?
The superior oblique muscle
Which cranial nerve is responsible for most eye movements? Which nerves do the rest?
Cranial nerve III.
IV (trochlear - superior oblique- look down and inward) and VI (abducens - lateral rectus- abduction)
What does XII (hypoglossal nerve) innervate?
ALL tongue muscles EXCEPT palatoglossus - which is innervated by the vagus nerve (X)
When are delta waves present on the EEG?
They are abnormal 4Hz waves - but can be normal in sleep or in children
When are alpha waves prominent on the EEG?
On closing the eyes or with increased cortical activity
When are beta waves prominent in the EEG?
Over the frontal area
