Nervous Tissue Flashcards
What is the CNS composed of
spinal cord and brain
What is the PNS composed of?
cranial nerves and spinal nerves
What is the function of nervous tissues
carrying information through electrical impluses throughout the body
What does the somatic nervous system regulate?
Somatic nervous system regulates control over skeletal muscle
What does the autonomic nervous system regulate?
Autonomic nervous system regulates control over heartrate, breathing, things that are automatic
What are the divisions of the ANS and what do they regulate?
The sympathetic division of the ANS is the branch that responds when the body needs sudden or immediate action. Fight or flight response. Increase rate of function in times of need
The parasympathetic division of the ANS regulates less urgent actions. Such as digestion, waste disposal, production of bodily fluids. Regulates basal rate
What are the cells of nervous tissue?
neurones, glial
What is the role of neurones?
to send signals around the body
What are glial cells and what is their role?
support cells and to protect and provide nutrients to neurones
What is the basic structure of a neurone?
dendrite, cell body (nucleus), axon, axon terminal (boutons)
What is the dendrite?
highly branched cellular process which extends from a large cell body
they form synapses with adjacent neurones
What is the axon?
conducts action potentials
rapidly sends signals to the axon terminals
in CNS - mylienated
in PNS - can be mylienated or non mylienated
What are the terminal boutons?
neurotransmitter are released here
form synapses with neurones
electrical signal converts to chemical signal
What is the fundamental property of a neurone?
excitability
Describe how messages are delivered in neurons
Action potential travels through the neuron, reaches the terminal boutons and chemical message is released
and then received by dendrites of the next neuron and then processed to trigger an action potential in that next neurone
Identify the neuroglial cells located only within the central nervous system
Ependymal cells, Astrocytes, Microglia, Oligdendrocytes
Identify the neuroglia cells located only within the peripheral nervous system
Schwann cells, Satellite cells
What are ependymal cells?
Simple ciliated cuboidal epithelium
Lines fluid-filled cavities in brain (ventricles) and spinal canal
No basement membrane
What are astrocytes?
Most numerous cell within the CNS.
Mediate the exchange of metabolites between neurones and the vascular system
From blood-brain barrier and have a star-like structure
What are microglia?
Microglia are derived from monocytes and microphages
In response to tissue damage, these cells will transform into phagocytic cells. They will remove invading microbes and dead cells from CNS
What are oligdendrocytes?
Predominant neuroglia of white matter
Form myelin sheaths around all CNS axons
Provide structural and metabolic support
What are Schwann cells?
Form myelin sheaths around PNS axons
Provide structural and metabolic support
Non-myelinated axons are enveloped in cytoplasm of Schwann cell
Myelinated axons are gradually wrapped by the Schwann cell membrane to create a myelin sheath
What is an alternative name for nerve fibres?
axons
What is each nerve fibre surrounded by in the PNS (around Schwann cells)?
endoneurium
What is each fascicle surrounded by?
perineurium
What are bundles of fascicles surrounded by?
epineurium
What does the perikaryon refer to?
cell body of neuron
By looking at the individual fibres at high magnification, you will notice that there are short intervals at which the axon is not covered by a myelin sheath. What is the name of these intervals?
nodes of ranvier
What is the function of the nodes of Ranvier?
Allows nutrients and waste to enter and exit the neuron.
Enhances conduction speed of axons
Local anaesthesia is widely used in dental practice. The local anaesthetic acts by binding to an internal site on the Na+ channels and blocking them. Why are the nodes of Ranvier important in this process?
They allow Na+ to access the sodium channels.
Na+ channels are enriched at nodes of Ranvier
Do nerve fibres differ in calibra?
yes
How can the effectiveness of local anaesthesia be affected by the presence of adipocytes?
The potency of an anaesthetic is associated with its lipid solubility. Greater lipid solubility enhances diffusion through nerve sheaths, as well as the neural membranes of individual axons comprising a nerve trunk.
The local anaesthetic bupivacaine is more lipid soluble compared with lidocaine. Which of these anaesthetics is most likely to be prepared at a higher dose to achieve equivalency of action with the other?
lidocaine
What organs do the motor neurones at the lumbar level predominantly innervate?
lower limb muscles
What organs do the motor neurones at the cervical level predominantly innervate?
upper limb muscles
In which direction does information typically travel in the ventral horns?
downwards
In which direction does information typically travel in the dorsal horns?
upwards
Where are Purkinje nerve cells found?
cerebellum
