All About ... Nerve Cells

Nerve cells (or neurones) convey information (messages), as I explained in my blog about the nervous system a while ago.  All living things have to be able to detect changes in their environment and then respond accordingly to survive.  The change is known as a stimulus and this can be from inside the living thing (internally) as well as externally.  Horses, like all mammals, detect external stimuli in the sense organs (eyes, ears, nose, skin, mouth)but then the message has to be conveyed to cause a response.  This is where the nervous system comes in . 

Nerves are tight bundles of nerve fibres.  Nerve cells (neurones) have a body which contains a nucleus and the nerve fibres, which are the long extensions, these transmit the nerve impulses around the body.  The fibres which carry the impulses away from the nerve cell body are called axons and those carrying the impulses to the cell body are called dendrons.  The cell body may also have smaller dendrons called dendrites!

In horses, the sensory neurones transmit messages from the sensory receptors  (in the peripheral sense organs) to the Central Nervous System (CNS).  The motor neurones carry messages from the CNS to the muscles and glands.  

The motor neurones convey information incredibly quickly, a message (or impulse) can be transmitted from the spinal cord to the feet in a few milliseconds.  These neurones are protected along most of their length by a myelin sheath which provides a thick insulating layer.  The sheath is basically a series of cell membranes each of which are formed by a Schwann cell, which are then wrapped around the axon.  Along the membranes of the Schwann cells are gaps (nodes of Ranvier) and these are the key to fast transmission of impulses. 

The nerve impulses are electrical signals, these are generated when something stimulates the nerve membrane.  If this stimulation is above a certain level (threshold) it will cause a change in the membrane's permeability and therefore an exchange of ions across the membrane.  This in turn causes a small current to flow in the cytoplasm of the nerve fibre and in the fluid surrounding the cells (extracellular fluid).  This current will stimulate the nerve membrane of the next neurone which will then alter its permeability again causing an exchange of ions ... and so on along the nerve fibre.  

In nerve fibres which have a myelin sheath (motor neurones) the impulses travel more quickly because they 'jump' from one gap (node of Ranvier) in the cell membrane to the next.  This also uses less energy.   

The impulse then moves along the nerve fibres through the body.  To move from one neurone to another there is either an electrical or a chemical 'message'.  This message has to pass across the gap between cells - the junction (or synapse)!  Most cells will communicate using a chemical 'message' called a neurotransmitter.   

When the impulse reaches the end of the fibre it will cause a change in permeability again, allowing the release of a neurotransmitter across the gap.  This neurotransmitter will then cross and attach itself to the other cell, which will then be stimulated and the ion exchange will continue down that nerve fibre.  When the final nerve fibre interacts with the muscle, gland or organ the neurotransmitter will cause a reaction .. dilate pupils, move a muscle etcetera.  Usually, more than one impulse along a nerve fibre will be needed to cause a reaction.

Stimulation of the nerve membrane can be caused by: light, sound, pressure or other neurones.  The stimulation is also an 'all or nothing' response, there is either an impulse or there is not an impulse, it does not vary in strength.  The stronger the stimulus the more impulses are produced in a given time.  

In sense organs, however, there are many neurones and these have different threshold levels which gives the brain more information about the stimulus.

This is a simplified explanation of how nerves work - it is a complex and amazingly clever system!

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Jo

Jappeloup - Greatest Horses

Jappeloup was a 15.2hh black showjumper ridden by Pierre Durand in the 1980's.  Born in 1975 His sire was a French Trotter, Tyrol II and his dam a Thorougbred called Vénérable.  

Relatively small for show-jumping he had the most amazing jump. He was a fiery little horse and great to watch - make sure you find some clips on YouTube because he is fantastic!

In 1984, at the Olympics,  Jappeloup stopped at a jump, Pierre flew into the jump and the bridle came off, leaving Jappeloup to gallop back to his stable.  

In 1985 they were 3rd at the World Cup Final.

In 1986 they were 4th individually and part of the Bronze winning team at the World Championships.

In 1987 they won individual Gold and team Silver at the European Championships.

In 1988 they were 2nd at the World Cup Final and won individual Gold and team Bronze at the Olympics in Seoul.

In 1989 they were part of the Silver winning team at the European Championships.

In 1990 they were 2nd at the World Cup Final but part of the Gold winning team at the World Championships.
Jappeloup was retired but 3 months later he sadly died at 16 of a heart attack :(

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Jo

All About ... Cells

In quite a few of my blogs recently I have mentioned cells; epithelial cells, muscle cells, bone cells nerve cells etc.  Although, I vaguely remember learning about cells in Biology at school I don't remember much about them - so I thought I would find out!

Just about all living things are made of cells 

·         cells are the building blocks of living organisms

·         new cells only appear when existing cells divide

·         cells contain inherited information - which controls their activities

·         the chemical reactions of life take place inside cells

Animal cells are different from plant cells!

Animal cells have:

·         a surface membrane which encloses the contents

·         inside the membrane there is a nucleus (like a ball) and cytoplasm

·         inside the nucleus there is chromatin (fibrous material), it is this material which condenses to form chromosomes during cell division

·         the chromatin contains DNA - which is the inherited material controlling cell activity

·         scattered within the cytoplasm are mitochondria - these supply energy to the cell

·         within the cytoplasm are also particles of stored food (often glycogen)

Plant cells also have:

·         a vacuole - a large sap filled cavity, sap is a fluid which contains salts and sugars

·         the vacuole is surrounded by a membrane called the tonoplast

·         the cytoplasm also contains starch grains (food storage for plants)

·         plant cells (only in the green parts of a plant) also have chloroplasts in the cytoplasm.  These contain pigments used in photosynthesis.

Knowing about the ultra-structure of animal cells helps to understand how they work ....  the surface membrane (cell membrane) is selectively permeable, which means it lets some substances through but not all, it controls the exchange of these substances between the cell and its surrounding environment.   The cytoplasm is made up of cytosol, which is a fluid containing molecules, and different organelles: -

·         nucleus - is enclosed by 2 membranes (nuclear envelope) which have pores controlling the exchange of substances between the nucleus and the outside environment ie: the cytoplasm.  As well as the chromatin in the cytoplasm there are nucleoli which make ribosomes

·         endoplasmic reticulum and ribosomes - endoplasmic reticulum (ER) comes in 2 types, smooth and rough.  Smooth ER does not have any ribosomes.  ER is a system of sacs, each sac is full of fluid.  In the Rough ER the sacs transport proteins - proteins made by the ribosomes.  In the Smooth ER carbohydrates and lipids and other products (but not proteins) are made, stored and secreted.  NB - in liver cells the Smooth ER contains enzymes which break down chemicals. 

·         mitochondria - are also enclosed by 2 membranes.  They enclose a watery substance which contains DNA, ribosomes, enzymes and calcium phosphate granules.  Mitochondria are involved with the generation of ATP (a form of energy used to form biological activities).

·         golgi apparatus and lysosomes - the golgi apparatus 'processes and packs'  cell material into small sacs (vesicles) so that it can pass through the cell membrane.  It is also involved in the formation of lysosomes which remove worn out organelles (such as mitochondria).  Lysosomes are also involved with the breakdown of tissue and will digest substances which white blood cells have ingested eg: bacteria.

·         Centrioles - are involved in cell division.

·         Flagella and cilia are involved in cell locomotion.

The cell membrane forms the barrier between the cell and the environment around it.  It is strong but flexible because the cells must be able to move, grow and divide.  It also provides a surface for hormone and neurotransmitter receptor sites.

As I mentioned at the beginning of this blog there are many different types of cells in a horses' body.  They are all very similar in structure and ultra-structure BUT have specialised, this makes them more efficient.  However, some have specialised and so lost their ability to carry out other functions - red blood cells do not have a nucleus so they cannot reproduce.

Cells of the same type are grouped together to form tissue.  All the cells in the tissue will act together to perform the same function.

Tissue may join with tissue of a different type to form an organ: muscle tissue, nerve tissue and connective tissue all work together in the heart.   So an organ is a group of tissues which work together to   perform a specific function.  

 So, cells are pretty important .... to everything we do consciously and unconsciously!  

Have you seen Wednesday's video 'It's October!'  on my You Tube channel?   
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Until next time!

Jo

A sunny autumn day ...

Follow my leader ...
 

  
What a beautiful day ...

 

 

 

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Jo

Things to look out for now - Autumn

There are a lot of things I love about Autumn, but it also means Winter is not far away.  I start tidying, cleaning and preparing for the dark mornings and nights in plenty of time to try to make them easier.  However, there are still things to look out for at this time of year!

Top of the list is Atypical Myopathy.  Also known as Sycamore Poisoning this is usually FATAL. Sycamore seeds and leaves are a source of the toxin which causes this so prevent your horse from eating them.  Make sure your horse is not in a field with sycamore trees, especially at this time of year when the seeds are falling (these are the ones that look like helicopters).  Unfortunately the seeds can blow quite a long way so if there are trees nearby check your field!  

Look out for acorns now too.  Horses love them but they are poisonous, as are the leaves of the Oak tree, and so can cause Colic if many are eaten as well as diarrhoea.

Mud Fever - my field is just beginning to get muddy so I am starting to look out for this now.  As I have mentioned before Chesney is most susceptible because of his white legs, Basil and Tommy seem to be fine even though they are much thinner skinned!  

Rainscald is often a problem too at this time of year in the UK.  As the weather turns and it rains more, often horses don't have rugs on as it is not particularly cold and this means they are exposed and can be more susceptible. 

Tapeworm - if you haven't already then now is the time to worm for Tapeworm, or ideally carry out a tapeworm saliva test first.  I do find these a bit irritating because the horses have to stand for half an hour before I can do the test, but it is worth it to help prevent resistance building up.

Laminitis is still a concern with the final burst of growth from the grass before the winter, so keep an eye on weight and body condition score!  I do like Basil and Chesney to have a slightly higher condition score going into the winter as both tend to lose quite a bit at the end of the Winter when there is no grass left.  

Now is the time many people change their horses from being grass kept to stable kept.  I don't have to worry so much as my horses are out half the time and in half the time throughout the year but with many yards limiting winter grazing it is often not an option.  It is important to consider what affect this will have on your horse.  Have a look at a blog I wrote a while ago about this.

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Jo

Things that affect healing ...

For the past few weeks I have been blogging about injury and how types of therapy can help healing and repair after injury.  However, there are factors which can negatively affect healing too.

Position of the wound is important because healing depends on the blood supply to the area.  Parts of the horse with lots of arteries and veins eg: the face, will heal more quickly.  The lower leg has a much poorer blood supply and so healing is slower.  In addition to this, if the wound is in an area of the horse which is moved often, healing will be slower.  As with any other animals, horses will also lick or bite painful wounds which can again slow healing.

The shape of the wound can also affect healing.  Larger wounds will heal more quickly if the skin is loose because the wound is able to contract, where there is less skin the wound is filled much more slowly as it relies on the multiplication of epithelial cells.  In these situations excess granulation tissue can also form.  

Granulation tissue is a normal part of the healing process.  However, in the lower leg it can become a problem.  In the normal healing process  the surface of the wound will heal over at the same time as the deeper part of the wound is healing.  Unfortunately, if this is slow (as in the lower leg), the wound will not heal over quickly enough to confine the granulation tissue.  In this situation the granulation tissue can grow over the edge of the wound and form proud flesh.  Epithelial cells will NOT grow over proud flesh but through and this is VERY SLOW.  The granulation tissue will cause the epithelial cells at the edge of the wound to die so it is important to prevent proud flesh forming.

Foreign bodies in the wound will also affect the healing process because they harbour bacteria.  The foreign body eg: a thorn, will irritate the area and stimulate the inflammatory process .  The foreign body will then be caught in the fibrous tissue and form an abscess.  The area will not heal until the foreign body has been removed (or made its own way to the surface).

Have you seen this week's video 'Stables and Yawns' on my You Tube channel?   
Horse Life and Love.  Please check it out and SUBSCRIBE.

You can also follow me on Facebook, Instagram and Twitter for updates on Chesney, Basil, Tommy and Daisy. 

Until next time!

Jo