lecture 19 - nerve tissue histology Flashcards
What are the histological features of a soma nucleus?
Pale (euchromatic), spherical, central
What are the organelle features of a neurone soma?
rich in rER and sER to prodcue proteins, nissl bodies, neuronal cytoskeleton
What is the name for aggregations of ER in a neurone soma?
Nissl bodies
What part of a neurone contains mitochondria?
All parts
What part of a neurone is involved in the afferent signalling system?
dendrite
What part of a neurone is involved in the efferent signalling system?
Axon/axon terminal
What type of axodendritic connections do dendrites receive?
Both excitatory and inhibitory
Where does the axon of a neurone start?
At the axon hillock
How can the axon hillock be identified based on organelles present/absent?
It is a region free from nissl bodies
What is the name for the expansions at terminal parts of axons?
Presynaptic boutons
What are the types of macroglia cells in the CNS?
Astrocytes, oligodendrocytes
What are the functions of astrocytes?
energy store, maintain/regulate synapses, help form blood-brain barrier
What is the function of oligodendrocytes?
myelinate CNS axons
How many axon segments can a single oligodendrocyte myelinate?
Up to 50
What are microglia?
Antigen presenting immune cells of the CNS
How do astrocytes regulate the blood brain barrier?
By changing permeability/constriction of blood vessels in the brain
What is the distribution of schwann cells in realtiob to axons?
Found along axons in longitudinal chains
What are the roles of schwann cells apart from myelination?
facilitation of axonal regrowth following acute nerve injury.
What is a myelin sheath made up of?
Tightly wrapped spiral of lipid-rich cell membrane of schwann cells (PNS) or oligodendrocytes (CNS)
How does the wrapping of the myelin sheath occur?
Wrapping proceeds from outside to inside, starting with a portion of the axon.
How are Schwann cells involved with unmyelinated axons?
They envelope multiple axons, but do not wrap them in myelin
What is the internode of an axon?
A territory myelinated by an oligodendrocyte or Schwann cell, between 2 nodes of ranvier
What is a node of ranvier?
An interval between two myelinated internodes of an axon
How are nodes of ranvier important in propagating action potentials?
They have ion pumps for exchanging sodium and potassium ions across membrane to help in propagating depolarisations
What are the 3 main connective tissue sheaths of nerve tissue?
Epineurium, perineurium, endoneurium
What is the epineurium of peripheral nerves connected to surrounding tissues by?
Mesoneurium
What is the mesoneurium of nerves?
Connective tissue that joins peripheral nerves to outside structures, and contains nerve segmental blood supply
What encloses a ganglion?
Fibrous connective tissue
What type of neurone make up the dorsal root ganglia?
Unipolar/pseudounipolar, with both myelinated and unmyelinated axons
What part of a neurone is invovled in a ganglioin?
Soma
What sheath surrounds the soma in the dorsal root ganglion and provides structural and metabolic support?
Satellite glial cells
What type of neurone make up autonomic ganglia?
Multipolar neurons
What are the histological differences between autonomic and dorsal root ganglia?
autonomic have fewer satellite glial cells, and the neurones soma are more widely spaced as they are separated by dendrites and other axons. dorsal root ganglia are unipolar while autonomic are multipolar
What are the 2 types of sensory receptor nerve endings?
free nerve endings, encapsulated nerve endings
What are the 5 key types of encapsulated nerve endings?
meissner’s corpuscles, pacinian corpuscles, ruffini endings, neuromuscular spindle, golgi tendon organs
Where are golgi tendon organs found?
Near a musculotendinous junction between a muscle and tendon
What stimuli will activate golgi tendon organs?
Passive stretch/tension in tendon, active contraction of muscle
What is the function of golgi tendon organs?
They provide proprioceptive information about musculotendinous junctions
