Nervous System

Question 1

General reason for NS

Answer 1

Respond more quickly and as a whole to different stimuli, communication between organs and with the outside world.

Question 2

CNS

Answer 2

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

Question 3

3 types of muscle NS can stimulate

Answer 3

Skeletal, Cardiac, Smooth

Question 4

Stimulating Cardiac, smooth, or glandular epithelium

Answer 4

Affects internal processes = Autonomic nervous system

Question 5

Stimulating skeletal muscle

Answer 5

Somatic Nervous system

Question 6

Large nerves in the limbs

Answer 6

Somatic nerves (info from muscles and from skin)

Question 7

Where are the neurons in CNS? What are they called?

Answer 7

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).

Question 8

PNS

Answer 8

Ganglia and olfactory mucosa and retina of the eye.

most of the PNS is nerves.

Question 9

Neural cell bodies

Answer 9

Reach a certain level of input- produce or stop response (inhibitory or excitatory). They are working out what to do!

Question 10

Inhibitory signal

Answer 10

Goes to another cell body- stops axon from firing.

Question 11

What is a tract? Or pathway?

Answer 11

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

Question 12

White matter

Answer 12

All the neural cell processes- rich in MYELIN!!!

Question 13

Central canal- where is it? What is it?

Answer 13

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

Question 14

What sort of neural cell bodies in the spinal ganglion?

Answer 14

Sensory (they are dorsal). LEFT AND RIGHT- both sensory.

Question 15

What makes up the spinal nerve

Answer 15

Made up of mixed dendrites and axons.

THEN there is a dorsal route and ventral route

Question 16

What is another name for sensory? And motor?

Visceral and somatic

Optic and olfactory

Answer 16

Sensory= Afferent

Motor= Efferent

Visceral = V

Somatic= S

olfactory- info from nasal mucosa

Optic nerve= special nerve (a few other examples)

Question 17

How can nerves be classified?

Answer 17

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

Question 18

Visceral nerves are where?

Somatic are where?

Answer 18

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.

Question 19

GVE

Answer 19

General visceral efferent

e.g. vagus n. or sympathetic chain.

Question 20

Biceps muscle- what nerve classification?

Answer 20

GSE (general somatic efferent)

Question 21

General classification of all nerves.

Answer 21

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

Question 22

Autonomic

Answer 22

Housekeeping, internal

Question 23

Why do you need a motor movement to recognize a lesion?

Answer 23

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.

Question 25

Meninges

Answer 25

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.

Question 26

Intervertebral disc

Annulus Fibrosis

Nucleus pulposus

Answer 26

Nucleus pulposus- remanant of the motor cord (slipped disc is the protrusion of the nucleus pulposus)

Question 27

Dorsal branch and ventral branch of spinal nerve

Answer 27

Dorsal branch goes to apaxial muscles- the ones above the transverse processes

Ventral branches- go to everything else

Question 28

Brachial plexus and Lumbar sacral plexus

Answer 28

Know the nerves

Question 29

Difference in C1 foraminae

Answer 29

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.

Question 30

How do they name the cervical spinal nerves? and thoracic?

Answer 30

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.

Question 31

Cauda equina “Horses tail”

Answer 31

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.

Question 32

Intumescences

Answer 32

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)

Question 33

Divisions of the spinal cord

Answer 33

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.

Question 34

Position sense

Answer 34

How fast it is changing, etc.???

Question 35

What is importanta bout the Cutaneous Trunci?

Answer 35

Use to plot out where damage is occuring in the spinal cord. “Sensory arc”

Question 36

What nerves have both sensory and motor ??

Question 37

Where is the ramus communicans?

Answer 37

Thoracocolumbar

Question 38

Where are neurons located outside of the CNS?