Overview of PNS Flashcards
define nucleus (plural: nuclei) (in terms of neuronal nomenclature)
nucleus= A group of functionally related nerve cell bodies in the CNS. (NOT the nucleus of a single cell!)
e.g. Inferior olivary nucleus, nucleus ambiguus, caudate nucleus
define column (neuronal nomenclature)
Column= In the spinal cord, a group of functionally related nerve cell bodies that form a longitudinal column extending through part or all of the length of the spinal cord.
e.g Clarke’s column
define Tract or fasciculus (fasciculi)
Tract or fasciculus (fasciculi)= A bundle of parallel axons in the CNS (fasciculus is Latin for “bundle”)
e.g. Optic tract, corticospinal tract, medial longitudinal fasciculus, fasciculus gracilis
=spinal tracts are bundles of axons in CNS, these bundles are organised into specific groups with specific functions forming the tracts
ASCENDING TRACTS= conduct sensory info up to brain
DESCENDING TRACTS= motor instructions down the cord
define nerve, ramus (rami), nerve root
A bundle of axons or nerve fibres. A typical peripheral nerve may have many thousands of individual nerve fibres of many different diameters
what vertebral level does the spinal cord end at
The spinal cord ends around L1/L2, consequently, the caudal nerve roots below the first lumbar root form the cauda equina.
If the sensory loss corresponds to multiple dermatomes the damage is more likely to be the ____________ nerve
If the sensory loss corresponds to multiple dermatomes the damage is more likely to be the peripheral nerve
where is a lumbar puncture performed and why
Lumbar puncture (sampling of cerebrospinal fluid) performed between L3-L4 or L4-L5 to avoid spinal cord
what are the symptoms of cauda equina syndrome
- Cauda equina syndrome
- S = saddle anesthesia (numbness and loss of sensation in the buttocks, perineum, and inner surfaces of the thighs)
- P = pain
- I = incontinence (fecal + urinary)
- N = numbness
E = emergency
_________ MATTER IS WHERE THE NEURONS SYNAPSE + TRANSMIT INFO TO Each other
GREY MATTER IS WHERE THE NEURONS SYNAPSE + TRANSMIT INFO TO Each other
what do the following sensory receptor sense for:
1) root hair plexus
2) free nerve ending
3) meissner corpuscle (encapsulated)
4) pacinian corpuscle (encapsulated)
5) ruffini ending (encapsulated)
6) merkel disc
- Root hair plexus
- Very sensitive mechanoreceptors for touch
- Free nerve ending
- Temperature, mechanical stimuli = pain
- Meissner corpuscle
- Discriminatory touch, sensitive for shape and textural changes
- Pacinian corpuscle
- Vibration and deep pressure
- Ruffini ending (bulbous corpuscle)
- Skin stretch and sustained pressure/movement
- Merkel disc
Pressure, position (deep static touch features)
What kind of neuron detects linear head position
the OTOLITH organs detect linear forces acting on the head, whether by static displacement of hair bundles due to gravity or by transient displacement of hair bundles due to linear accelerations, and this information is preserved in the firing rate of vestibular axons.
Which one of these demonstrate slow adaptation:
* merkel nerve endings
* pacinian corpuscles
- Some neurons the magnitude of the generator potential decays
○ Slow adaptation = Merkel nerve endings □ Good for coding sustained stimulus and its intensity for entire duration ○ Rapid adaptation = Pacinian corpuscles
Good for coding changes in stimulus intensity but not duration
what do golgi tendon organs detect?
muscle tension receptors (proprioceptors)
Aα group Ib
what do muscle spindles detect?
Muscle spindles=
* they’re Proprioceptors
* that are Muscle length receptors
* 5-10% of all neurons in DRG
Aα group Ia
what is the difference between a generator potential vs. an action potential
- Generator (receptor) potential (can potentially become AP if stimulus large enough)
- In the receptor (e.g. sensory dendrites in skin)
- Graded
- Does not obey the all or none rule (it grades how strong stimulus is)
- Can be summated
- Unpropagated
- Action potential
- In the sensory nerve fibre
- Not graded
- Obeys all or none rule
Not summated
