histology nervous tissue

1. Nervous tissue,
Epithelial Glands,
endocrine glands
Dr sandeep

18.  Multipolar : numerous dendrites project from
the cell body; the dendrites may all arise
from one pole of the cell body or may extend
from all areas of the cell body surface.
 Bipolar: have only a single dendrite which
arises from the pole of the cell body opposite
to the origin of the axon.
 Pseudo-unipolar neurones: single dendrite
and the axon arise from a common stem of
the cell body.

37.  Terminal bouton. Presynaptice axon responsible for
propagating the stimulus terminates at a bulbous
swelling K/as.
 Non myelinated.
 contain mitochondria and membrane bound vesicles
of neurotransmitter substance known as synaptic
vesicles .
 Synaptic vesicles . Contain neurotransmitter
substance which are different in CNS and PNS e.g.
ACh, NA, glutamate or dopamine.
 Synaptic vesicles are transported into the synaptic
bouton down the axon from the cell body. Vesicles
can also be formed in the synaptic bouton by
recycling of vesicle membrane.
 Synaptic vesicles aggregate towards the presynaptic
membrane and, on arrival of an action potential, dock
with the membrane and release their contents into
the synaptic cleft by exocytosis.

38. Narrow intercellular gap of uniform width
(20–30 nm) between two neurons called
the synaptic cleft.
The neurotransmitter diffuses across the
synaptic cleft to stimulate receptors in the
postsynaptic membrane.

41.  Commonest cause of dementia
 Loss of synapses in the hippocampus and the
cerebral cortex.
 The synapses mediating neurotransmission by
acetylcholine (cholinergic system) are
particularly affected.
 Once secreted into the synaptic cleft,
acetylcholine is rapidly destroyed by the action
of cholinesterases.
 Cholinesterase inhibitor drugs are now given to
patients with Alzheimer’s disease to
compensate for the synaptic loss by maximising
the impact of remaining cholinergic synaptic
activity

43.  An autoimmune disease affecting the motor end plate .
 Patients develop fatigue and muscle weakness.
 Normally, the motor end plate releases acetylcholine
(ACh) which binds to receptors on the muscle surface to
cause depolarisation and muscle contraction.
 In myasthenia gravis, ACh is released normally but its
effect on the postsynaptic membrane is reduced
because acetylcholine receptors (AChR) have been
depleted by binding to autoantibodies specific for the
receptor.
 Treatment with cholinesterase inhibitors temporarily
prolongs the effects of the ACh signal and leads to
improved muscle strength.

48.  Each peripheral nerve is composed of one or more
bundles (fascicles) of nerve fibres.
 Within the fascicles, each individual nerve fibre with its
investing Schwann cell is surrounded by a delicate
packing of loose vascular supporting tissue called
endoneurium.
 Each fascicle is surrounded by a condensed layer of
robust collagenous tissue invested by a layer of flat
epithelial cells called the perineurium.
 In peripheral nerves consisting of more than one
fascicle, a further layer of loose collagenous tissue called
the epineurium binds the fascicles together.

51. Single fascicle,
invested by the
perineurium P
composed of
several layers of
flattened cells
with elongated
Nuclei.
TS of peripheral Nerve

52. Nerve fibres often follow an undulating or
zigzag pattern in longitudinal section, as shown here.

53. Discrete aggregations of neuron cell bodies
located outside the CNS.
The spinal ganglia are located on the
posterior nerve roots of the spinal cord;
they contain the cell bodies of the primary
sensory neurones ( pseudo-unipolar form).