Nervous Tissue🧠 Flashcards
What is the function of nervous tissue?
to provide rapid and precise communication between different parts of the body via the action of neurones
The nervous system includes various organs throughout the body, what are these?
brain, spinal chord, receptors of complex sensory organs and the nerves that link the nervous system with all of our other organs and systems in the body
Where do organs of our nervous system receive information from? What do they do with this information?
-Receive info from both their internal and external environment
-process that info and then send out necessary signals to initiate a response
The Nervous system is divided into what two main divisions
Peripheral Nervous System
Central Nervous System
How do the peripheral nervous system and central nervous system bring about a response?
-Peripheral NS delivers sensory info to the CNS
-where it is processed and the signals are sent back out to PNS
-This sends out required signals to initiate an appropriate response.
What two divisions can your Peripheral Nervous System be functionally divided into?
-Somatic Nervous System
-Autonomic Nervous System
What is the function of the Somatic NS?
regulates voluntary control over our skeletal muscle (conscious movement)
What is the function of the Autonomic Nervous System?
Controls involuntary subconscious functions like heartbeat and breathing
Our Autonomic nervous system can be further sub-divided into what two divisions?
Sympathetic NS
Parasympathetic NS
What is the parasympathetic nervous system?
Referred to as the rest and digest system, regulates less urgent process i.e.
-digestion, waste disposal, production of bodily fluids
What is the sympathetic nervous system?
Branch that responds when body needs immediate action, Regulates fight or flight
What function does the parasympathetic and sympathetic nervous system have in common?
Both regulate smooth and cardiac muscle contractions
What is a way of thinking about the parasympathetic and sympathetic nervous system?
Parasympathetic regulates basal rate of all these processes, keeping things ticking along and then the sympathetic system can come in and up the ante, increasing the rate of these functions in times of need
What are neurones?
The main functional cells of the nervous system
What are neurones specifically designed to do?
send signals and communicate with our organs and tissues using electrical impulses
What are neuroglia/ glial cells?
What are their function?
They are support cells
They have have various different roles that include;
-providing support
-protection,
-providing nutrient
-providing immune protection to our neurones
What are neurones specialised for?
Intercellular Communication- communication between cells
-Do neurones live for long?
-What is the metabolic rate of neurones like and why?
-They are long lived cells
-high metabolic rate because the generation and propagation of action potentials, so these electrical impulses place significant energy demands on our neurones
What is the structure of neurones like?
Neurones display substantial variation in size and shape but all have the same basic structure
What are dendrites?
What is their role?
What happens at this site?
-Highly branched processes that extend away from the cell body.
-These play a key role in intracellular communication.
-This is the site at which neurones will receive info from other cells or sensory receptors
What are the size of neurone cell bodies like?
Large cell bodies significantly larger than other cells like neuroglia
All neurones have a single axon, what is the function of these axons?
The axon is designed to rapidly propagate electrical Impulses/ action potentials from one part of the body to another
Describe the size of the single axons of neurones?
some of these can be extremely long, i.e. in the peripheral nervous system some axons can be up to a meter in length
Describe the axon terminals?
At the axon terminal, the axon branches into smaller branches, and at the foot of these branches you have what is known as Terminal Boutons
What do TERMINAL BOUTONS do?
form communication junctions with other cells in the pathway and these communication junctions are often referred to as synapses
What is a function that ALL neurones have?
Excitability
Describe what is meant by EXCITABILITY
-there is a small difference in charge between the inside and outside of the cell.
-It is this property that enables the generation of action potentials
-charge is briefly reversed before returning to baseline
- brief change in electrical potential of the cell and this is what we call an action potential.
What do the purple lines represent on this diagram?
-terminal boutons that form synapses with the dendrites
-These belong to another neurone in the pathway and they are interacting and communicating with the dendrites here
Form?
Respond to?
Convey?
What are Dendrites and their role?
Highly branched processes extending from cell body
Form synapses with adjacent neurones
Respond to external stimuli from other neurones
Convey incoming information to cell body
Dendrites convey incoming information to cell body, what will the cell body do with this information?
interpret information and decide whether to initiate an action potential
Give 3 features of a neurones cell body?
-Large Nucleus and prominent nucleolus
-Nissil Bodies
-Numerous Mitochondria
What are Nissil Bodies?
clusters of rough endoplasmic reticulum,
What surrounds Nissil bodies?
Free Ribosomes
What can we see from this histological image of nervous tissue?
-Neuronal cell bodies are much larger than those of the neuroglia
-Prominent nucleolus, a sign of active and ongoing synthesis of ribosomes
Nissil Bodies can give what appearance to nervous tissue histologically?
Can give neurones a granular appearance when you look at them histologically
-can also see stains a lot darker here in this image compared with surrounding cells
- partly due to nissl bodies and partly due to the high density of other cellular organelles such as mitochondria
As well as giving cell bodies a granular appearance, what else do Nissil Bodies do?
gives grey matter its distinctive colour, i.e. where cell bodies of neurones are located in the CNS.
If you take a gross dissection through the Central Nervous System, you can divide it into what matter?
Grey and white matter?
Where does Grey matter get its distinctive colour from?
Where does white matter indicate?
-predominantly from high densities missile bodies present in neuronal cell bodies
-white matter predominantly indicates where the axons are located
What is the function of axons and what are they specialised for?
-Rapidly propagates signal from cell body towards axon terminals
-Specialised to conduct action potentials
Are axons myelinated or non-myelinated in the Peripheral NS
Axons in PNS can either be myelinated or non-myelinated depending on whether they are coated by an external myelin sheath
Are axons myelinated or non-myelinated in the Central NS
All axons within the CNS are myelinated, it’s the myelin that gives the white matter a distinctive colour
What gives white matter its distinctive colour?
Myelin
What do terminal Boutons form?
What are they?
What happens at terminal boutons?
Form synapses with other neurones or effector organs
Form Communication junctions (eg neuromuscular junctions)
Here electrical signal converted to chemical signal
Neurotransmitters released and convey message to next cell in pathway
What are communication junctions?
A type of synapse at the end of terminal boutons
Cells of the Nervous System;
What is the function of neuroglia and where do they exit?
-Protect and support neurones
-Variety that exist, some only exist in CNS some only exist in PNS
What are the four types of neuroglial cells in the CENTRAL NERVOUS SYSTEM
Ependymal cells
Astrocytes
Microglia
Oligodendrocytes
Central Nervous tissues consist of a vast number of neurones, where are their processes of these neurones?
-Embedded in a mass of support cells, which is collectively known as the neuroglia.
-These cells form almost half of the mass of the CNS
-highly branched cells that occupy the spaces between neurones in the diagram.
-They have intimate functional relationships with the neurons and provide both mechanical and metabolic support,
Ependymal cells make up what tissue?
Simple Ciliated cuboidal epithelium
What is the shape of ependymal cells? and how are they bound together to form Simple Ciliated Cuboidal Epithelium?
-Cuboidal or low columnar
-Tightly bound together at their adjacent luminal surfaces
Do ependymal cells lie on a basement membrane?
No
-the cells taper into these long processes which merge with underlying tissues
What is at the surface of ependymal cells and what do these structures facilitate?
-At the luminal surface of these cells they have various cilia and some microvilli
-help to move for example spinal fluid around and they also regulate the composition of spinal fluid
Where would you find epedymal cells?
Lining fluid filled cavities in brain (ventricles) and spinal canal
Describe astrocytes and their function.
Named for their star-shape
Large, most numerous glial cells
Form the blood-brain barrier
Regulate the chemical environment
What do astrocytes provide and mediate?
Mechanical support and mediate exchange of metabolites between neurones and the vascular system
What are Microglia and what is their function?
Named for their small size
Phagocytic capacity -Derived from monocytes and macrophages - in response to tissue damage these cells will transform into large phagocytic cells so will…
-Remove invading microbes and dead cells from CNS
What are oligodendrocytes and what is their function
Predominant neuroglia of white matter
Form myelin sheaths around all CNS axons
Provide structural and metabolic support
The neuroglia of the peripheral nervous system is made up of what two cell types?
-Schwann Cells
-Satellite Cells
How does myelination of axons provide structural and functional support?
structural support as it encases them within this myelin sheath, but also functional support because myelin increases the rate of action potentials along the axon.
What are Schwann cells and what are their function?
Form myelin sheaths around PNS axons
Provide structural and metabolic support
How are non-myelinated and myelinated axons structured
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 are Satellite cells?
- PNS
-Flattened cells that cover the surface of neuronal cell bodies
-Provide Structural and Functional Protection
-Most cell bodies in the CNS are located within the grey matter
Where are cell bodies outwith the CNS i.e. within the PNS located?
In structures known as ganglions
What are ganglions and what is located here?
Aggregations of neuronal cell bodies that are located near the spinal column, this is where satellite cells are located