Nervous System Flashcards
General reason for NS
Respond more quickly and as a whole to different stimuli, communication between organs and with the outside world.
CNS
Brain and spinal cord. Cells (neurons) contained within skull and vertebral column where they are protected. Cells with a body and various processes: large nucleus, pale staining nucleus, axon hilloc, axon, and dendrites (can have thousands or just a dozen)– generally only has one axon. Axon takes information out. Dendrites receive information from other cells in the periphery. Axons of other cells may end up on dendrites or the cell body. Or other dendrites from other cells. The only way you can understand the NS is by seeing it respond. Neurons in protected places like the CNS or specific places outside called Ganglia (in other words- only in the CNS or ganglion EXCEPT for ones in the olfactory mucosa and retina of the eye).
** When something goes on wrong a neuron has died OR something has prevented the signal from going out (axon) or coming in (via dendrites)
** Nerve- bundle of axons and dendrites from many different neurons. Appear white because of the fatty myelin sheath that surrounds the bundles of axons and dendrites.
**Axons and dendrites carry info by depolarization.
* Electric currents in wires next to each other- they might jump- so the myelin sheath insulates axons and dendrites
* Axons going to the periphery- go either to the ganglion or to where they can signal to another neuron. OR in order to do anything they are going to muscle or gland epithelium.
* the only way the NS can make a change– muscle or gland
3 types of muscle NS can stimulate
Skeletal, Cardiac, Smooth
Stimulating Cardiac, smooth, or glandular epithelium
Affects internal processes = Autonomic nervous system
Stimulating skeletal muscle
Somatic Nervous system
Large nerves in the limbs
Somatic nerves (info from muscles and from skin)
Where are the neurons in CNS? What are they called?
Central Grey Matter (LESS MYELIN!! why it is grey) WHERE THE NEURAL BODIES ARE
Central part of spinal cord. In the deep brain nuclei. And on the periphery or cortex of the cerebrum (cerebral cortex and the cerebellar cortex).
PNS
Ganglia and olfactory mucosa and retina of the eye.
most of the PNS is nerves.
Neural cell bodies
Reach a certain level of input- produce or stop response (inhibitory or excitatory). They are working out what to do!
Inhibitory signal
Goes to another cell body- stops axon from firing.
What is a tract? Or pathway?
Bundle of neuron cell processes- would be called a nerve in the periphy but in the CNS it is called a tract, pathway, a bundle, etc.
e.g. pathway from stubbing toe all the way to the sensory cortex of the brain where you become consciously aware of it– depending on where it is going it will be named accordingly
White matter
All the neural cell processes- rich in MYELIN!!!
Central canal- where is it? What is it?
Of the spinal cord. Grey matter makes a butterfly shape in the middle which may or may not have a “lump” either side. Dorsal and ventral horn. Dorsal is sensory- ventral is motor (basic division)– works all the way to the base of the brain- the brain stem.
Within thoracolumbar and sacrum- intermediate horn- visceral motor- e.g. autonomic (sympathetic) & in the sacral spinal cord intermediate horn- (parasympathetic).
**Regions in the level in the brain stem would be parasympathetic (base of the brain)– congregations of nuclei… basal (motor) intermediate (PS motor) and dorsal (sensory)
** Arrangement holds true for the whole nervous system
What sort of neural cell bodies in the spinal ganglion?
Sensory (they are dorsal). LEFT AND RIGHT- both sensory.
What makes up the spinal nerve
Made up of mixed dendrites and axons.
THEN there is a dorsal route and ventral route
What is another name for sensory? And motor?
Visceral and somatic
Optic and olfactory
Sensory= Afferent
Motor= Efferent
Visceral = V
Somatic= S
olfactory- info from nasal mucosa
Optic nerve= special nerve (a few other examples)
How can nerves be classified?
General or special, visceral or somatic, and afferent or efferent (sensory or motor)
Most nerves are G = general
Autonomic- V= visceral
Skeletal muscle= S= somatic
Sensory endings = S= somatic
Example of special- optic nerve
Visceral nerves are where?
Somatic are where?
Intermediate part of the spinal cord or in the associated part of the brain
somatic = ventral horn OR equiv. in the brain (various nuclei in the brain= going to skeletal muscle or if they are dendrites they carry sensory information from surface of the body and joints, muscles, etc.
GVE
General visceral efferent
e.g. vagus n. or sympathetic chain.
Biceps muscle- what nerve classification?
GSE (general somatic efferent)
General classification of all nerves.
Every nerve in the body carries a mixture of the different fibres at least afferent and efferent. The only ones that don’t are the special ones in the brain- the optic n. (one of the pairs of cranial nerves- SSA- special somatic afferent), olfactory (SVA- special visceral afferent- already inside and the way it develops), and vestibular cochlea from petrous temporal bone straight into the brain (SSA- special somatic afferent)
MOST COMMON:
GVE- preganglionic autonomic fibres
GSE- skeletal muscle
GSA- sensory nerves
Autonomic
Housekeeping, internal
Why do you need a motor movement to recognize a lesion?
Need a response from the animal. May be possible to see when a gland isn’t secreting– dry arm. Still a response. Only 3% of those neurons are motor (effector)- cause muscles to contract or glands to secrete. Nerves are the neurons processes. 15% are sensory- directly- touch, warmth. Everything else is an interneuron (each may have 100,000 connections- millions of cells so there are more potential connections in your brain then particles in the universe- most connections don’t hitch)- within the ganglia and within the CNS. Collecting info from the 15% that are getting sensory information and getting information from the motor– and integrating it and making some sense of it.
* In order to induce nerve cells to hitch and connect- you have to get an input. Most alternative modalities are trying to find a way to get an input into the NS. May only be 15% but it is enough. Provide diff temperatures, moving things– all sorts of ways to stimulate NS and bringing it to a stage of awareness. e.g. nerve damage- stimulating area over time- sometimes over years can sometimes bring the sensation back- a neurologist will very rarely say never. Every NS is different- even if you are an identical twin. Slight differences make a big difference down the track.
* Tricking your brain to put the effort in- to recognize. The more ways you have of recognizing the information- the more likely to develop strong pathways. You are likely to get tired- the brain uses 20% of the cardiac output, 20% of oxygen supply, if it runs out of glucose will metabolise muscles to stay working. Very active and reactive material.
Meninges
3 layers of membrane
Lies within the vertebral canal surrounded by 3 membranes
Pia mater between it and the next one is the fluid filled space and the next one is the arachnoid mater (LIKE A SPIDER)– fluid is the cerebral spinal fluid (CSF)- between pia and arachnoid. The next one is dura mater. Arachnoid is normally connected straight across to the dura so you would not be able to separate it easily.
Within spinal column through most of the length. Between the dura and the periosteum of the bone there is a certain amount of fat dorsal and ventral- surrounding the spinal column– below the vertebral arch and vertebral body and the spinal column.
Intervertebral disc
Annulus Fibrosis
Nucleus pulposus
Nucleus pulposus- remanant of the motor cord (slipped disc is the protrusion of the nucleus pulposus)
Dorsal branch and ventral branch of spinal nerve
Dorsal branch goes to apaxial muscles- the ones above the transverse processes
Ventral branches- go to everything else
Brachial plexus and Lumbar sacral plexus
Know the nerves
Difference in C1 foraminae
Left and right come out of special foraminae in the atlas. You have to protect it from movement. Lateral foraminae of the atlas protect the nerves. In some species- the axis also has similar foramina- depends on range of movement. Otherwise always come out in the intervertebral foraminae. Means it can get trapped if the vertebrae end up positioned poorly.
How do they name the cervical spinal nerves? and thoracic?
8 pairs of cervical spinal nerves and only 7 cervical vertebrae. They exit cranial to which the bone they are named. C1 exception.
T1 spinal nerves come out left and right caudal to the first thoracic vertebrae. FROM T onwards= CAUDAL.
Cauda equina “Horses tail”
At the end of the spinal cord where you have the nerves coming out further away from the end of the spinal cord. Just have projection of their processes further along the vertebral canal. Only the caudal vertebrae. Only when you reach the end that it is a long way caudal.
MEANING if you see damage in one area- the damage may be much further up.
Intumescences
enlarged because it looks bigger compared to the rest of the spinal cord that has lost a lot of its size (because it develops larger and then if not used, atrophies)
Divisions of the spinal cord
Divided into 6
Dorsal funiculi - PROPRIOCEPTION sensory (important tracts: proprioceptor tracts–> fasciculus gracilis (proprioceptive (position sense) info from the body caudal to cranial thoracic– hindlimb and more caudal part of the trunk e.g. lower end of the trunk and the hind legs)- on both sides— and then underneath fasciculus cutaneous (forelimb and neck basically))– ascending**
Lateral funiculi (all sorts)- RUBROSPINAL TRACT- FACILITATE FLEXORS– both ascending and descending**
Ventral funiculi (motor)- MOTOR AND SPECIFICALLY FACILITATE EXTENSOR MUSCLES (helps you stay standing up)– descending**
* shorter tracts- closer to the grey matter
* longer tracts- going straight to the brain- so they aren’t as close
* side note: spinocerebellar- from the spine to the cerebellum- immediately know it is a sensory tract– will be either in the dorsal or lateral funiculus. Motor- will be the other way around– somethingspinal– e.g. corticospinal. From cerebral cortex to the spine.
***also rubrospinal– most interest to vets– from the midbrain.
Position sense
How fast it is changing, etc.???
What is importanta bout the Cutaneous Trunci?
Use to plot out where damage is occuring in the spinal cord. “Sensory arc”
What nerves have both sensory and motor ??
Where is the ramus communicans?
Thoracocolumbar
Where are neurons located outside of the CNS?
