Nerve Tissue Flashcards
Nervous tissue is an essential part of which system?
Nervous system
What are the 2 main subdivisions of nervous tissue?
CNS- Central Nervous System
PNS- Peripheral Nervous System
What does the CNS compose of?
brain and spinal cord (and optic nerve)
What does the PNS compose of?
all nervous tissue outside CNS
What are the 2 divisions of the PNS & their function?
Sensory/afferent division: Information to the CNS.
Motor/efferent division: Information from CNS to the organs (muscles and glands)
The Nervous system helps to..?
Maintain homeostasis (along with the endocrine system),
Initiates voluntary movements
Responsible for perception, behaviour and memory
The nervous systems activities are grouped under 3 major functions, what are they?
Sensory: Detection of internal and external stimuli and transfer to CNS
Integrative: analysis and storing of information
Motor: stimulation of effectors (e.g. muscle and glands) through PNS i.e.
motor here means “effector”
Nervous tissue consists of two types of cells, what are they?
Neurons (nerve cells that can be very large)
Neuroglia (supportive cells – usually small)
What is the longest cell in the body that goes from spinal cord to toe- 1m)?
Neurons
Are neurons consious or unconsious control?
Both
WHat do neurons do?
Have a cell body into which short, branched dendrites convey nerve
impulses (action potentials) and from which a longer, single axon
conducts nerve impulses to another neuron or tissue
What are dentites in neurons?
The receiving/input part
of the neuron (looks like branches)
What are axons in neurons?
arries the nerve impulse
away from the neuron. It is the
output portion of the neuron.
(looks like tail)
Do neurons divide?
No
Do neurons have a high metabolic rate?
Yes
Will neurons die rapidly without O2?
Yes
WHat are the features of a multipolar neuron?
Have 2 or more dendrites
and a single axon.
* Most common neurons in
CNS
* All motor neurons (control
skeletal muscle) are in
this class
* Some of longest (spinal
cord to toe muscles)
(cell body at the top- dentrites branch around)
WHat are the features of a Bipolar neuron?
Two distinct processes
– 1 dendritic process (can
branch at tip but not at cell
body)
– And 1 axon
* Has cell body between
axon and dendrite- dentrite at the top
* Rare and small (30μm)
* Special sense organs
(sight, smell, hearing) relay
information from receptor
to neurons
What are the features of a Unipolar neuron?
The dendrites and axon
are continuous
* Cell body off to one side
* Whole thing from where
dendrites converge called
axon
* Most sensory nerves are
unipolar
* Very long (1m) like motor
nerves CNS-toe tip
Anaxonic neuron features?
Rare and function
poorly understood
* Anatomy cannot
distinguish dendrites
from axons
* Found in brain and
special sense organs
Are neuroglia cells found in CNS or PNS
BOTH
Neuroglia features?
Make up ~50% the volume of the CNS (“glue”).
* Smaller than neurons but more numerous (5-50x)
* Do not propagate action potentials, but can communicate.
* Can divide within the mature nervous system
What are the functions of Neuroglia
Physical structure of nervous tissue
* Repair framework of nervous tissue
* Undertake phagocytosis
* Nutrient supply to Neurons
* Regulate interstitial fluid in neural tissue.
What are the 4 types of Neuroglia in the CNS?
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
Astrocytes features
Star-shaped; largest; most
numerous of neuroglia.
Syncytium network.
b. Support (have microfilaments)
and repair (scar).
c. Communicate with neurons via
‘gliotransmitters’ e.g. glutamate
d. Maintain environment around
neuron by e.g. regulating ions.
e. Maintain blood-brain barrier
via endothelium. Wrap around
vessels and influence their
permeability
Oligodendrocytes features
Form insulating
multilayered myelin sheath
( protein lipid layer) around
CNS axons.
– Can myelinate more than
one neuron cell’s axon.
Accelerate the action
potential
Microglia features
Phagocytic (resident
macrophages) - protection
Inactive microglia= spaced out and smaller
Active microglia = close packed and bigger
Ependymal cells features
Produce cerebrospinal fluid (CSF).
* Line the Cerebrospinal Fluid (CSF)-filled
ventricles in the brain and the central
canal of the spinal cord.
* These single layer of predominantly
cuboidal cells have cilia (flow) and
microvilli (sampling).
* Located in ventricles and in other locations
where CSF found.
* CSF mechanical buffer; moves nutrients
and waste
Neuroglia in PNS
Sshwaan cells
Satelite cells
Schwann cells (“PNS version of CNS oligodendrocyte”) features
form insulating
myelin sheath around axons or can just support and surround several non-
myelinated axons. (Note: One Schwann cell per axon for myelination but
more axons/cell if just support)
Satelite cells features (equiv. to astrocytes in CNS)
surround neuron cell bodies. Support and fluid exchange
.
