Nervous tissue Flashcards
Central Nervous System
- this consists of the brain and the spinal cord
- this processes and coordinates sensory input and motor output
- the area of higher intelligence, memory, learning and emotion
Peripheral Nervous System
- this is divided into afferent and efferent systems
- this is anything outside of the CNS
Afferent Nervous system
- carries sensory information to CNS
- receptors monitor the environment which then sends information to the CNS
Efferent Nervous system
- this is then divided into the somatic and the autonomic nervous systems
- the efferent pathway is the pathway that is leaving the CNS and an effect will be coming within the body
somatic motor system
this controls the skeletal muscles
- this can be voluntary and involuntary
ex. moving your arm to drink water is done consciously but moving you hand off a hot stove is a reactionary response
visceral nervous system
- this is the unconscious actions that the body recognizes in the afferent and efferent
- afferent would be using receptors to see what is happening internally
- efferent would be actions that are taken in response to what the afferent system said was happening
- this regulates smooth muscle, cardiac muscle, and glandular activity.
- this is always involuntary
ex. heartbeat, digestion
sensory nervous system
this is the afferent nervous system
- can be visceral or somatic
motor nervous system
this is the efferent nervous system
-this can be visceral or somatic
visceral motor system
- would be secretions from glands or contractions of smooth muscle in response to sensory input
- this is unconscious
Somatic motor system
this would be a voluntary movement and involves the innervation of skeletal muscle
-this is concious
visceral sensory system
- the body is watching for internal environmental changes with receptors
- the body looks how much is being secreted from glands or how the blood vessels are dilated and this then goes to the CNS which will make a decision on what the approbate visceral motor response will be
- this is unconscious
somatic sensory system
- as external changes such as touch, pain occur, this sends that information to the CNS to allow it to react
- this is concious
dendrite
sensory processes that are stimulated by changes of activities by other cells
axon
conducts a nerve impulse toward the axon terminal
neuroglia
these are glial cells
- they have the ability to divide
- different types in the CNS and PNS
soma
- another name for cell body
- contains the nucleus,mitochondria, ribosomes, and other organelles and inclusions
5 characteristics of Neurons
- send electrical signals to glands, other neurons or muscles
- live for a lifetime
- cannot divide
- high metabolic rate (they need a good blood supply
- most cell bodies in the CNS
why are most of the cell bodies in the CNS
this is because when there is damage to the cell body the neuron will die
-the CNS is surrounded by bone so it is really important for them to be in there or near it for protection
collection of cell bodies in the CNS
nucleus
collection of cell bodies in the PNS
ganglian
collection of axons traveling to a common destination in the PNS
nerve
collection of axons traveling to a common destination in the CNS
tract or column
endoneurium
this is the connective tissue that is around each axon
perineurium
this in the connective tissue around individual fascicles
Fascicle in regards to the nervous system
this is a group of axons
epineurium
connective tissue around the entire nerve
synapse
this is the place of neuronal communication
-this is at the end on one axon and at the cell body or another neuron
astrocytes
-a glial cell in the CNS
-this is star shaped and has long processes that reach out through the CNS
-these are the largest and the most numerous of all the glial cells
Functions:
-maintain blood/brain barrier
-provide structural support
-regulate ion, nutrient, and dissolved gas concentration
-absorb and recycle neurotransmitters
-form scar tissue after injury
oligodendrocytes
-a glial cell in the CNS
-small cell bodies and shorter processes than astrocytes
Functions:
-mylinate the CNS axons
-provide structural framework
what is the main difference between oligodendrocytes and Schwann cells
- the Schwann cells can only myelinate on axon and only one part of one axon where as oligodendrocytes can myelinate multiple axons and multiple parts of an axon
microglia
-a glial cell in the CNS
- these are the smallest of the glial cells
Fuctions:
remove cell debris, waste and pathogens using phagocytosis
-sometimes called the “immune system of the brain”
ependymal cells
-a glial cell in the CNS
-cubodial or columnar in shape and have cilia
Functions:
-lines the ventricles (brain) and central canal (spinal cord)
-assist in producing, circulating and monitoring how cerebral spinal fluid
Satellite cells
-a glial cell in the PNS
Functions:
-surround neuron cell bodies in peripheral ganglia
-regulate the echange of nutrients and waste products between the ECF and the cell body
-isolates neuron from stimuli not intended to pass from neuron to neuron
Schwann cells
-a glial cell in the PNS Functions: - surround the axons in the PNS -myelinate peripheral axons -participate in the repair process after an injury
glial cells
- these can divide
- provide protection, insulation and nourishment for neurons
- provide scaffolding for neurons
- much more abundant than neurons
- not excitable so cannot send signals
bipolar neuron
this has dendrites that merge together to form a single dendrite which then travels to the cell body which is in the middle and then goes to the axon
-very rare and is used in special senses (sight and smell)
pseudounipolar neuron
- dendrites converge and meet the axon early in the pathway
- looks like the cell body is hanging off
- used to sense touch in the periphery to the CNS
multipolar neuron
- this is the most common
- dendrites surround the cell body and a signal is sent out through one axon
convergence
this is when many neurons synapse at a single post synaptic neuron
- this allows for amplification of a signal in some cases
- may also allow for an increased strength of signal which may be required for the post synaptic neuron to fire
divergence
this is when on neuron synapses onto many post synaptic neurons
-this allows for a message to be widespread and alert many places of what is going on
node of ranvier
this is the space between two schwann cells in the myelin sheath
myelin
- a lipid rich substance with a whiteish appearance (makes up the white matter of the brain and spinal cord)
- in the CNS this will be done by the ogliodendrocytes and in the PNS this will be done by the schwann cells
myelination
this is the process of wrapping an axon in a myelin sheath
-a Schwann cell wraps itself around the axon and keeps wrapping over and over, all the while forcing the cytoplasm into the superficial layers
myelin sheath
this insulates, improves conductance and protects the axon
-made of many schwann cells on one axon or many ogliodendcytes
gliomas
this is a tumor of the glial cells
ex. astrocytoma = tumor of the astrocytes
- oligodendroglioma=tumor of the oligiodendrocytes
- mixed glioma = many cell types within
what are more difficult to resect or remove? Astocytomas or olgodendrogliomas?
Astrocytomas because they have less defined boarders because these cells stretch throughout the CNS which makes it difficult to know if you actually got the whole thing
axon regneration
- this can only occur in the PNS
- the axon is broken and then the schwann cells are able to create a regeneration tube and secrete chemicals to promote axonal regeneration but the oligodendrocytes do not do either of these things so not possible in CNS
what other than the oligodendrocytes in the CNS prevents axon regeneration?
the astrocytes wall off areas in the brain that are damaged to isolate the area and protect surrounding areas and that makes it hard for axons to regenerate and break through the barrier
(oligodendrocytes can not make the regeneration tube and secrete chemicals that inhibit regeneration)
Wallerian Degeneration
An injury to an axon occurs which causes anything after the injury to break down or “degenerate”
-anything before the injury is fine but anything after fragments off
