Nervous Tissue Flashcards
What is the function of nervous tissues?
Provide rapid and precise communication between different parts of the body via action of neutrons. (Electrical impulses)
What 4 things does the nervous system include?
Brain
Spinal chord
Receptors of complex sensory organs
Nerves that link it with all other organs and tissues in the body
What makes up the CNS?
Brain
Spinal chord
What makes up the peripheral nervous system?
All nervous tissue outside the CNS
What are the 2 functional divisions of the peripheral nervous system?
Describe them.
Somatic = regulates voluntary control over skeletal muscle
Autonomic = heartbeat, breathing (subconscious)
Name and describe the 2 autonomic nervous systems.
Parasympathetic = regulates less urgent processes eg. digestion, waste disposal (referred to as rest and digest)
Sympathetic = branch that responds when body needs sudden or immediate action (regulates fight or slight response)
Describe similarity and difference between parasympathetic and sympathetic?
Both can regulate smooth muscle and cardiac muscle contraction
Parasympathetic- regulates basal rate of all these processes so it keeps things ticking
Sympathetic - increases rate of function in times of need
Name the 2 main cell groups in the nervous system?
Neutons and Glial cells
Describe neurones in the NS.
- nerve cells
- main functional units of nervous system
- send signals and communicate with organs and tissues
- use electrical impulses
Describe the function of glial cells (neuroglia) in the NS.
- support cells
- protect and provide nutrients
- provide immune functions and protection
Name 4 structures a neuron contains?
Dendrites
Large cell body
Single axon
Terminal boutons
Describe a functional property all neurons have?
EXCITABILITY
- small difference in charge inside and outside cel
- enables generation in action potential
- briefly reversed before returning to baseline
- brief change in electrical potential of cell (action potential)
Why do neutrons have a high metabolic rate?
Generation and propagation of action potentials so these electrical impulses place a significant energy demand on neurons.
Describe the structure of dendrites.
Highly branched processes extending from the cell body
They form synapse with adjacent neurones.
Describe how dendrites communicate with terminal boutons from a different axon?
Axon branches into terminal boutons which forms synapses with dendrites from another neuron in the pathway
How do neurons respond to external stimuli?
They respond to external stimuli from another neuron and convey info to the cell body.
It interpretates it and decides weather to initiate action potential.
What are neurons specialised for?
Intercellular communication
Describe the cell body of a neuron?
large nucleus
prominent nucleolus
Contains nissil bodies
Has numerous mitochondria
Larger than surrounding neuroglia
What does the nucleolus do in the nucleus (cell body) of a neuron?
Active and ongoing synthesis of ribosomes
This reflects the high metabolic demand of neutrons
What reflects the high metabolic demands of neurons?
High concentration of cellular organelles
Prominent nucleolus
What are nissil bodies and what do they do in the cell body of a neuron?
Clusters of RER
Free ribosomes surround
They give neurons a granular appearance
Why does the cell body of a neuron stain darker than the surrounding cells?
Nissil bodies and density of other cell bodies eg mitochondria
Describe grey and white matter in a neuron.
White = axons are located
Grey = cell bodies of neurons located
What is the function of an axon in a neuron?
Rapidly propagate signal from cell body to axon terminals.
What are axons specialised for in neurons?
Conduct action potentials
Are axons myelinated or non-myelinated in the CNS & PNS?
PNS = can be myelinated or non-myelinated
CNS = myelinated
How do you know if an axon is myelinated or non-myelinated in the PNS?
Depending on whether they are coated by an external myelin sheath
Function of a terminal bouton?
Form synapses with other neurons or effector organs
What is a neuromuscular junction?
It’s a communication junction
Type of synapse between motor neuron and skeletal muscle fibre it’s communicating with
What happens at the terminal bouton?
Electrical signals are converted to chemical and the neurotransmitters are released and convey messages to next cell in pathway
What are neuroglia cells?
Support system of the nervous system
What type of neuroglia exist in CNS?
Ependymal cells
Astrocytes
Microglia
Oligodendrocytes
What type of neuroglia exist in PNS?
Schwann cells
Satellite cells
What is the shape of a ependymal cell? (Neuroglia)
Simple ciliates cuboidal epithelium
What do ependymal cells do? (Neuroglia)
Line fluid filled cavities in brain (ventricles) and the spinal canal.
Features of ependymal cells? (Neuroglia)
Merge with astocytes.
Have cilia and microvilli at liminal surface to move spinal fluid and regulate its composition.
No basement membrane - Taper into long processes that merge with basement membrane.
What shape are astrocytes?
Star shaped
What is the most numerous glial cell?
Astrocyte
What glial cell forms the blood-brain barrier?
Astrocytes
Function of Astrocytes?
Regulate chemical environment
Mechanical support and mediate exchange of metabolites between nerurons and vascular systems
How do Astrocytes regulate metabolites?
Wrap tightly around blood vessels and allow them to diffuse from blood to CNS
Shape (size) of microglia?
Small
What glial cell has phagocytic capacity?
What does this mean?
Microglia - derived from monocytes and macrophages
What do Microglia do in response to tissue damage?
Transform into large phagocytic cells to remove microbes and dead cells from CNS
What Neuroglia is prominent in white matter?
Oligodendrocytes
Function of Oligodendrocytes?
Provide structural support and metabolic support
What do Oligodendrocytes do to axons?
Form myelin sheaths around axons in CNS
each axon may need many Oligodendrocytes to form the myelin sheath
Function of Schwann cells?
Provide structural and mechanical support.
What 2 cells are equivalent to each other in CNS and PNS?
CNS - Oligodendrocytes
PNS - Schwann cells
What do Schwann cells do to axons in PNS?
Form myelin sheaths around the PNS axons
What do Schwann cells do to non-myelinated axons?
They are enveloped in the cytoplasm of Schwann cells. (Small)
What do Schwann cells do to myelinated axons?
Gradually wrap them to form myelinated sheaths.
- wrapped by variable number of concentric layers
What do satellite cells do?
Cover surface of neuronal cell bodies.
Where are satellite cells located?
In ganglions of neuronal cell bodies near spinal column
Function of satellite cells?
Unknown however presumed structural and functional protection
