What are the only two exceptions to rule that all neurons have at least one axon and one or more dendrites?
- Amacrine cells of the retina
2. Granule cells of the olfactory bulb
What are Nissl bodies? AKA?
AKA chromophil substance because of its affinity for basic dyes
They are composed of membrane bound ribnucleoproteins (granular endoplasmic reticulum) responsible for synthesis– products are sent to the golgi apparatus
What organelle is noticeable missing from the axon?
Those for protein synthesis or assembly.
Nissl substance, Golgi complex and ribosomes)
What ion channels are located in the nodes of Ranvier?
Voltage gated sodium channels
What covers:
- Individual axons
- Grouping of axons
- An entire nerve (multibundle of axons)
- Individual axons: Endoneurium
- Grouping of axons: Perineurium
- An entire nerve (multibundle of axons): Epineurium
What is the only organelle found in the perkiaryon that is NOT in the dendrite?
Golgi apparatus
What neurons are bipolar?
Retinal cells
Olfactor receptors
Peripheral ganglia of the vestibulocochlear nerve
Sensory dorsal root ganglia is PSEUDOUNIPOLAR
Which neuroglia is the largest?
Astrocytes
Which astrocytes
- Have foot processes that form a continuous glial sheath surrounding blood vessels.
- Found in white matter concerned with transference and repair of damaged tissue
- Found in close proximity to neurons in the gray matter
- Fibrous
- Fibrous
- Protoplasmic
Identify which nerve fiber type and which number desgination
- Proprioreception and motor to skeletal muscles
- Contractile force (Golgi tendon organ)
- Pressure stretch muscle spindle, touch and vibration
- Motor to muscle spindle
- Nerve endings serving pain and temperature and touch
- Sympathetic preganglioninic axons
- Sympathetic post ganglionic
- Proprioreception and motor to skeletal muscles: Aalpha 1a
- Contractile force (Golgi tendon organ) Aalpha 1b
- Pressure stretch muscle spindle, touch and vibration: A beta 2
- Motor to muscle spindle A gamma 2
- Nerve endings serving pain and temperature and touch A delta 3
- Sympathetic preganglioninic axons B
- Sympathetic post ganglionic C 4
PRACTICE WRITING THE TABLE!
What is the speed of the fastest nerve fiber? Type A alpha 1a 1b
70-120m per second
12 to 22 micrometers in size
What is the only type of nerve fiber that is not myelinated?
Type C/ 4
Speed at 0.6-2.0m/s
Incomplete fusion of schwann cell membrane with schwann cell protoplasm is called?
Schmidt-Lanterman clefts
Which can produce myelin for a group of axons rather than just one?
Oligo
Schwann
Oligo
In synaptic transmission, when a AP arrives at the axon terminal what events occur?
Membrane at the terminal is depolarized
Calcium ions enter the permeable membrane terminal
Synaptic vesicles fuse with the presynaptic membrane releasing the NT.
Eg. if NT is Ach then upon contact with the post synaptic membrane there is an increase in permeability to Na thereby causing causing a propagated depolarization
What are the major synaptic vesicle associated proteins?
SYNAPSINS
Synaptotagmins are Ca++ sensors that signal docking after Ca++ surge
Vesicle side: Synaptobrevin++, Synaptophysin
Terminal side: SNAP 25 and Syntaxin++
++ interact directly
What constitutes a motor unit?
Motor neuron and the muscle fibers that it innervates.
What receptor is responsible for
- Constant touch or pressure and is responsible for the tactile gnosis of static objects such as in Braille reading
- Moving objects on skin
- Vibration– rapidly adapting receptors
- Pressure– slowly adapting
- Sensation of cold
- Merkel’s corpscles
- Meissner’s tactile corpuscles
- Pacinian/ Vater Pacini
- Ruffini’s corpuscles
- End bulbs of Krause
A gamma/ 2 fibers are for?
How about A alpha/ 1a fibers?
Motor to muscle spinde (intrafusal muscle fibers)
Motor to skeletal muscle fibers
When a muscle is excessively stretched what mechanism makes it relax?
Afferent nerve from the golgi tendon type A alpha 1b fibers synapes on the inhibitory interneurons of the spinal cord.
What is the maximal rate of axon elongation during regeneration?
5-6mm per day
but usually 1mm per day
What are the 2 key events upon transection of an axon?
- Nucleus and nucleolus swells and shifts location from central to peripheral resulting in an eccentrically located nucleus
- Chromatolysis of Nissl bodies– they become dispersed and the sharp staining pattern disappears– most marked int he perinuclear portion
Other orgnalles like golgi and mitochondira proliferate and swell
What are the different types of nerve injury?
Base on the Sunderland classification of nerve injury
- Neurapraxia: Distortion of myelin resulting in segmental block of conduction WITHOUT WALLERIAN DEGENRATION
1st degree nerve injury - Axonotmesis: Wallerian damage present
2nd degree nerve injury: axon loss
3rd degree: axon loss with endoneurial damage
4th degree: axon loss with endoneurial and perineurial damage - Neurotmesis: Fifth degree
Complete disruption of nerve with endoneurial, perineurial and epineurial damage
