Nervous System - Nerves 1 Flashcards
What is myelin and why is it effective?
Wraps around axon and insulates it
Faster signal transmission and aids axon repair
Schwann cell cytoplasm and plasma membrane form consecutive layers around the axon eventuating forming the myelin sheath with nucleus pushed to the periphery
Unmyelinated axons are enveloped by Schwann cells but there are no myelin sheath wraps around each axon
Unmyelinated region of axon = node of Ranvier
Saltatory conduction - nerve impulse jumps between un-myelinated nodes of Ranvier which speeds up signal transmission.
Describe a neurone.
Neurones can move an action potential along their axon to excite another neurone - wave of excitation
Soma produces all the proteins for dendrites, axons and synaptic terminals
Nissl bodies - combination of free ribosomes and RER
Neuropil - mass of interwoven nerve endings and dendrites from other neurones
Axon hillock - high amount of protein synthesis occurs here
How are neurones classified structurally?
Anaxonic - axon can’t be distinguished from dendrites
Bipolar - axon and single dendrite on opposite ends of soma
Pseudounipolar - dendrite and axon emerging from same process
Multipolar - 2 or more dendrites separate from the axon.
How are neurones classified functionally?
Motor, sensory or association.
What are the 3 types of connective tissue found in nerves?
Endoneurium surrounds an individual axon
Perineurium surrounds a fascicle (group of axons)
Epineurium surrounds a nerve
Describe satellite cells.
Found in PNS ganglia and enclose each neuronal cell body and regulate its microenvironment.
Describe oligodendrocyte.
Neurological cell in CNS.
Forms multiple myelin sheath units for axons.
Describe ependymal cells.
Neurological cell in CNS.
Low columnar like epithelial cells
Line the cavities of the CNS
Secrete cerebrospinal fluid
Describe astrocytes.
Neurological cell in CNS.
Control metabolite exchange between blood and neurones
Restraints of spread electrical disturbance by absorption of potassium ions.
Describe microglia.
Originate from blood monocytes
Macrophage, antigen presenting cell.
What is the difference between CNS and PNS?
CNS transmits using brain, cranial nerves and spinal nerves.
PNS transmits using spinal cord and peripheral nerves.
What is a muscle spindle?
Specialised muscle fibre with a stretch receptor
Conveys sensory information on muscle length to CNS
Sudden change in muscle length = contraction
What is a motor end plate?
Axon loses its myelination and forms a dilated termination - neuromuscular bulb that sits within a trough on the muscle fibre surface.
Highly specialised structures designed to efficiently transmit signals from motor neurons to muscle fibers, allowing for precise control of muscle movement
What is a Meissner’s corpuscle?
Mediates fine touch.
Located below epidermis
3-4 myelinated axons forming a complicated knot.
What is a Pacinian corpuscle?
Mediates pressure and heavy touch.
Located in the dermis.
Single axon with an un-myelinated end
