Wk 3: Nervous Tissue Flashcards
What is nervous tissue
The main tissue component of the nervous system
What is the function of nervous tissue
Neural communication within the body via neurons
What is the CNS composed of
- Brain
- Spinal cord
Where is the CT in the CNS
- Meninges
- Walls of large blood vessels
What is the PNS comprised of
- Branching peripheral cranial & spinal nerves
- Relay centres (ganglia)
What can the PNS be subdivided into
- Somatic nervous system
- Autonomic nervous system
Function of somatic nervous system
- Controls voluntary functions
- Transmits signals from brain to end organs
Function of autonomic nervous system
- Controls involuntary functions - heart rate, blood pressure
What do neurons do
Receive & transmit impulses
What do neuroglia do
- Support, protect & assisst neurons in neural transmission
- (dont receive or transmit impulses)
Where does the impulse in sensory neurons originate
In sensory receptors
How are the impulses in sensory neurons conducted
Conducted via sensory (afferent) neurons to the CNS
Where do motor neurons originate
In the CNS
How are the impulses in the motor neurons conducted
They are conducted via motor (efferent) neurons from CNS to the PNS, muscle tissue or glands
Interneurons function
Forms connections between neurons in the CNS
What is the axon hillock of the cell body
The region where the axon arises
What does the cell body contain
- Nucleus
- Perinuclear cytoplasm
What 2 types of processes extend from cell body / soma
- Single axon
- One or more dendrites
Function of the cell body
Receives signals from other cells & sends them towards the axon
What does the branching of dendrites result in
Synaptic terminals
What do dendrites function as
The major sites of information input into the neuron
What is the portion of axon that stretches from the origin at the axon hillock to the beginning of the mtelin sheath
Initial segment
What are the swellings on the ends of the axon branches called. What do these form??
- Terminal boutons
- These form synapses
What does an axon being myelinated mean
It has a myelin sheath
What does the grey matter of the CNS & PNS contain (2)
- Cell bodies
- Dendrites
What does the white matter of the CNS & PNS contain
Axons
Structure of bipolar neurons
- Single dendrite
- Single axon
Structure of unipolar neurons
One process which branches into central & peripheral branch
Structure of multipolar neurons
- Multiple dendrites
- Single axon
How does a chemical synapse work
- Presynaptic membrane releases neurotransmitters into synaptic cleft
- Neurotransmitter diffuses across synaptic cleft to gated ion channel receptors (located on postsynaptic membrane)
- Binding results in ion channels opening, allowing passage of ions - reverses membrane potential
What is the synaptic cleft
A gap separating the presynaptic & postsynaptic membranes
What are neurotransmitters decomposed by in the synaptic cleft
Enzymes
4 functions of neuroglia
- Monitoring synapses
- Regulating flow of CSF
- Scavenging neurotransmitters
- Releasing gliotransmitter - such as glutamate
Which 4 neuroglia are of the CNS
- Astrocytes
- Oligodendrocytes
- Microglia
- Ependymal cells
What neuroglia is of the PNS
Schwann cells
Function of astrocytes
Provide structural & metabolic support ot neurons
Function of fibrous astrocytes
Maintains blood brain barrier
2 functions of oligodendrocytes
- Electrical insulation
- Myelin production in the CNS
Where are oligodendrocytes located
Grey & white matter of CNS
Function of interfascicular oligodendrocytes
Manufacture & maintain myelin on axons of CNS
Function of microglial cells
Function as phagocytes: clear debris in CNS, protect nervous systme from viruses, m/os & tumour formation.
What happens when microglial cells are activated
- When activated by pathogens, they secrete interferon gamma which causes other microglia to be activated.
- Release signalling molecules to recruit T lymphocytes
Function of ependymal cells
Facilitates movement of CSF
What kind of epithelial cells are ependymal cells
Low columnar epithelial cells
Where are ependymal cells found
Lining the ventricles of the brain & central canal of the spinal cord
Function of schwann cells
Form both myelinated & unmyelinated coverings over axons in PNS
what are peripheral nerves
Bundles of nerve fibres (fascicles)
Located outside the CNS
What are the 3 layers of peripheral nerves
- Epineurium - outermost layer
- Perineurium
- Endoneurium - innermost layer
