Nervous System

what are the two divisions of the nervous system?

Central Nervous system

Peripheral nervous system

what does the central nervous system consist of?

Brain & spinal cord

what does the peripheral nervous system consist of?

spinal nerves (nerves branching off spinal cord)

cranial nerves (nerves coming off of brain)

what is the basic function of the nervous system?

input

integration

coordination

control

output

what are the two major peripheral pathways?

somatic nerve pathways

splanchnic nerve pathways

where does somatic nerve pathways supply?

the body wall/ anywhere with skeletal muscle

where do splanchnic nerve pathways supply?

body cavities /where smooth muscle and cardiac muscle are

what are the two types of nervous cells and what makes them different?

neurons - send signals

neuroglia cells - wrap around & support neurons

what is the structural organization of nervous tissue in the CNS?

It is made of mainly cells b/c it is vascularized with out CT. since there is not CT it is Jello like consistency (delicate) This creates the need for bones to protect it.

what is the structural organization of nervous tissue in the PNS?

cells and extracellular matrix wrapped in collagenous sheaths. has cells but also CT so tougher

what are the different types of neurons?

multipolar

pseudounipolar

bipolar

what is the structure of a multipolar neuron?

1. a cell body that has all the cellular components of a regular cells

2. dendrites (branches coming off cell body, increases SA, recieves signals)

3. axon - long single terminal with branches, going t next cell

4. boutons - little sacks at end of axon branches

what is the function of dendrites?

1. receive signal from other neurons

2. increase surface area for more connections

what is the function of the axon and boutons?

1. information send out

2. boutons actually release the signal

what are multipolar neurons located and what is their general function?

they are the most numerous neurons in the body.

All motor neurons are multipolar neurons.

They are responsible for motor movement and decision making.

what about the multipolar structure makes it good for decision making?

the large cell body in between the dendrites and the axon allow for incorporation of information and decision of weather to stop the signal or send it to the next neuron.

what is the structure of the pseudounipolar neuron?

a signal long axon with a cell body pultruding out in the middle

peripheral process with receptor terminals

central process with axon terminals

what is significant about the pseuodunipolar neuron's axon?

it has two process or parts.

peripheral process - part reaching out into body and has receptor terminals

central process - part reaching into spinal cord & has boutons to communicate with other neurons

what is the location and function of pseudounipolar neurons?

they are sensory neurons for basic senses (touch, temp, pain).

what is the structure of bipolar neurons?

dendrites with receptors terminals and cell body in center and then axon with boutons

what is the location and function of bipolar neurons?

sensory neuron of special senses

(sight, smell, hearing, taste)

sensation NOT decision making

how does electrochemical molecular movement occur?

nerve ion channels start polarized with positive chare in the interstitial fluid and negative charges inside. ions are excited and move through the ion channels conducting other ions to move through channels down the neuron.

what does excitability refer to?

the depolarization of the membrane

what does conductivity refer to?

the propagating of membrane depolarization. Allowing the excitability of ones part of the membrane to excite others

what always happens after a nerve impulse?

the nerve membrane repolarizes

what are the different types of neuronal circuits?

convergence

divergence

feedback loop

what is a convergence neuronal circuit?

when multiple neurons attach and send signals to one neuron

what is a divergence neuronal circuit?

one neuron attaches and sends signals to multiple neurons

what is a feedback loop neuronal circuit?

neuron loops back and gives feedback to the original neuron that sent the signal. allows for inhibition (usually negative)

what are the different types of the neuroglia cells and are they apart of the CNS or PNS?

astrocytes - CNS, nonmylenated

oligodendrocytes - CNS, mylenated

schwann cells - PNS, mylenated

what are the two different types of schwann cells?

nonmyelinating schwann cells

myelinating schwann cells

what do nonmyelinating schwann cells create, how many cells do the wrap around, & how many times do they wrap around said cells?

-can wrap multiple neurons (axons)

- wraps a single time

what do myelinating schwann cells create, how many cells do the wrap around, & how many times do they wrap around said cells?

-myelin sheath (cell membrane wraps around neuron)

- wraps one neuron

- wraps around many times

what is significant about astrocytes and oligodendrocytes of the CNS?

astrocytes are the nonmeylinating cells of the CNS and oligodendrocytes are the myelinating cells of the CNS

what is the structure and function of astrocytes?

-nonmyelinating cells

- many astrocytes attach to an axon creating a patch to cover the axon

- create grey matter

- creates a thin wrapping

what is the structure and function of oligodendrocytes?

- meylinating process

- wraps around multiple axons creating branches

- creates white matter

- thick wrapping multiple times

what is the structure of the myelin sheath?

internodal segment - thick part made from schwann cells

myelin sheath gap/node - thin part in between schwann cells

what is the functional significance of the myelin sheath?

It speed up action potential of signal by jumping elctrochemical depolarization.

what is it called when the myelin sheaths force the jumping of the myelin sheath nodes speeding up the action potential?

Saltatory conduction

what is a transducer?

changes one type of energy to another ( like a receptor)

what are the different types of receptors and their function?

1. mechanoreceptors - vibration, pressure, movement

2 .thermoreceptors - tempature

3. chemoreceptors - detecting chemicals (smell & taste )

4. photoreceptors - detect photons of light (seeing)

5. nociceptors - detect pain

6. proprioceptors - detect position of body in space

what creates complexity?

multiplicity of simplicity creates complexity

what is the purpose of synapses and how do they work put simply?

to communicate with other cells

yes or no switch

what are synaptic vessels?

bubbles in boutons that hold neurotransmitters

what are neurotransmitters?

chemical signals that are inside synaptic vessels (key)

what are the steps of the communication of signal from one neuron to another at the synapse?

1. impulse reaches the bouton

2. synaptic vesicles fuse to the membrane

3. vesicles release neurotransmitters

4. neurotransmitters bind to receptors on next neuron

5. channel gates open

6. membrane depolarizes and starts an impulse

what is the structure of a nerve? what is the tissues of it? NOT neuron

1. nerve fiber (neuron) and schwann cell wrap

2. endoneurium - lose CT (vascular supply) within & around nerve fibers

3. perineurium - dense irreg. CT creating fasciculus, resisting tension all over

4. epineurium - dense irreg. Ct wrapping whole nerve

5. May have lump called ganglion

what is a nerve fasiculus?

a little package of axons and endoneurium

what is a ganglion? what are the two different types?

a cluster of cell bodies in a nerve

sensory ganglion: psuedounipolar neurons

autonomic ganglion: smooth mucle associated

what structures in the vertebral column and vertebrae account for the spinal cord and nerves?

vertebral foramen (single vertebrae)/ canal (multiple) - hole where the spinal cord lives

intervertebral foramen - between vertebrate, allow for nerves to exit and enter the spinal cord

how many levels of nerves come off the spinal cord and how are they best grouped?

31 levels on the spinal cord:

C1-C8

T1-L2: white communicating ramus

L3-S1

S2-S4; parasympathetic pelvic splanchnic nerve

S5-Cocc

what are all the possible parts of the spinal nerve?

posterior & anterior rootlets

posterior & anterior roots

posterior root ganglion

the spinal nerve trunk

posterior & anterior ramus

white & gray communicating Ramus

parasympathetic pelvic splanchnic nerve

what are the intervertebral portions of the spinal nerves?

posterior & anterior rootlets

posterior & anterior roots

posterior root ganglion

what is the intervertebral foramen portion of the spinal nerves?

the spinal nerve trunk

what are the exterior branches of the spinal nerves?

posterior & anterior ramus

white & gray communicating Ramus

parasympathetic pelvic splanchnic nerve

what are parts of the spinal nerves are responsible for the sensory pathway?

posterior rootlets, root, & ganglion

what parts of the spinal nerve are responsible for the motor pathway?

anterior rootlets and root

what neurons are in the posterior roots and rootlets and what does this create?

pseudounipolar neurons

this creates the posterior root ganglion b/c of cell bodies

what neurons are in the anterior root and rootlets? what is significant about this?

multipolar motor neurons

cell body is in grey matter of spinal cord so there is no ganglion

what is the function of the posterior ramus and what sections of cord are they on?

-to supply the muscles of the back

- on all sections

what is the function of the anterior ramus and what sections of cord are they on?

- to supply all skeletal muscle not in the vertebral column

- on all sections

what is the function of the white communicating ramus and what sections of cord are they on?

- connect spinal nerve to sympathetic trunk

- is a myelinated axon

- only on T1-L2

what is the function of the grey communicating ramus and what sections of cord are they on?

- connect to anterior ramus to sympathetic trunk

- nonmyelinated segment

- on all section

what is the function of the parasympathetic pelvic splanchnic nerve and what sections of cord are they on?

- part of the autonomic nervous system

- goes to smooth, muscle in the pelvic cavity

- only S2-S4

what are plexus formation and where are they located?

a mesh of nerves coming together and apart

more near the limbs

what is a spinal reflex?

an automatic response before the brain even registers what is happening

what happens in a spinal reflex when the hand feels extreme heat?

a somatic sensory neuron receives signal from thermoreceptors causing a signal to travel through the the pseudo unipolar neuro through the posterior root where it synapses in the grey matter of the spinal cord with a multipolar motor neuron which travels through the anterior root to signal the brachial muscle to pull the hand away.

what must be incorporated for bilateral, multilevel, and continuous control during response?

interneurons or internuncial neurons

They are the nerves of the spinal cord and are multipolar neurons

what are the autonomic divisions of the PNS? are they sympathetic or parasympathetic? what does this mean?

thoracolumbar (sympathetic) and craniosacral (parasymp.)

parts that innervate "automatic" functions (smooth & cardiac muscle)

what nerves are part of the thoracolumbar nerves? what do they intervate?

communicating rami

sympathetic trunk & sympathetic trunk ganglion

INERVATES SMOOTH MUSCLE OF CARDIOVASCULAR TUBES and heart

stress response

what nerves are part of the craniosacral nerves? what do they intervate?

Parasympathetic

• vagus nerve

• pelvic parasympathetic splanchnic nerve

• pelvic ganglia (in wall or organs)

INERVATES SMOOTH MUSCLE OF GUT TUBE

Rest and digest

where are the ganglia of sympathetic and parasympathetic nerves?

sympathetic- in sympathetic nerves

parasympathetic - in wall of organs

what is the enteric plexus? Number of neurons? relationship to sympathetic and parasympathetic pathways? function?

the internal nerves of the digestive tubes & "second brain"

-Has 100 million neurons

-modulate action

-controls digestive tube on its own, can work independently of CNS so someone with a spinal cord injury and still have a working digestive system

what are the embryonic origins for thoracolumbar nerves and craniosacral nerves?

thoracolumbar- where yolk sack was so heart developed near which is why we have T1-L2 nerves there

Craniosacral- rapid development of gut tube creating digestive, urinary, & respiratory system. Anywhere there is rapid division of smooth muscle nerves grow to innervate that area.

- there are gaps of spinal nerves to allow for limb development

what are the 4 significant levels of different types of spina nerves?

C1 - C8

T1 - L2

L3 - S1

S2- S4