Nerve Tissue

What makes up the Central Nervous System?

Brain & Spinal Cord

What makes up the peripheral nervous system?

Cranial nerves, Spinal nerves, & ganglia

What are Neurons?

the communication cells of the Nervous system

What are Glial cells?

support cells

What do Neurons do?

detect a stimulus & transduce it into an electrical signal

What cells are present in the Central Nervous system?

Astrocytes, Microglia, Oligodendrocytes, & Ependymal Cells

What cells are present in the Peripheral Nervous system?

Schwann cells & Satellite cells

What is the soma of a neuron?

the cell body

What are Nissl Bodies?

Highly developed rough ER that aggregates within the cytoplasm & produce proteins (NT)

What are dendrites?

short projections from the soma of a neuron that can be branched & numerous

What is the Axon hillock of a neuron?

the region from which the axon projects from & it will generate an action potential

What is the Node of Ranvier?

the region along the axon that does not contain a myelin sheath

What is a Schwann cell?

a peripheral nervous system myelin-producing cell

What is an axon?

cylindrical process where action potential travels

What is an axon terminal?

the end of an axonal process; will branch into several different axon terminals per a single axon

What do cytoskeleton proteins do in a neuron?

support nerve cell processes & provide tracks for intracellular transport

What is a synapse?

A connection between two neurons

How do cells communicate with eachother?

through secretion of neurotransmitters at synapse

What are the two types of matter within the CNS?

Grey matter & white matter

What does grey matter contain?

neuronal cell bodies & dendrites

collection of cell bodies

glial cells

In relation to the nervous system what is a Nucleus?

collection of grey matter cell bodies within the CNS

What does white matter contain?

rich in axons & contains a few glial cells & neuronal soma

How is grey & white matter sorted in the Spinal cord?

Grey matter is surrounded by white matter

What are the three layers of the brain?

Inner most layer is grey matter

Middle layer is white matter connections

Outermost layer is another layer of grey matter (cortex)

What is ganglia?

collections of grey matter within the PNS

What are the three classifications of Neurons?

Morphology, Function, Neurotransmitter

What is a multipolar neuron?

One axon, lots of dendrites

What is a bipolar Neuron?

One axon & one dendrite

What is a unipolar neuron?

short process that splits from the soma in two with a continuous stream of conduction

What are pyramidal Neurons?

very large neurons commonly found within the cerebral cortex; have many large projections & triangular shaped bodies; most often excitatory

What is the function of sensory neuron?

transduce sensory input into electrical signal to be carried to brain for perception; also called cutaneous when referring to skin sensation

What is the function of motor neurons?

carry information to muscle cells to produce movement also called efferent carries information AWAY from the CNS

What is the function of an interneuron?

serve as a connection between motor & sensory within the CNS

What does it mean to be excitatory?

generate action potentials & depolarize the post-synaptic neuron

What are excitatory neurotransmitters?

glutamate, epinephrine, norepinephrine, nitric oxide

What does it mean to be an inhibitory neuron?

decreases the likelihood of action potentials & decreases the likelihood of depolarization

What are inhibitory neurotransmitters?

GABA, glycine, serotonin, dopamine

What are the functions of Microglia?

they are macrophages that respond to injury or disease

What is the morphology of Microglia?

variable; small cell body with many processes that are scanning environment

What are the functions of Astrocytes?

Support

Maintain blood-brain barrier

secrete & absorb NT in the synaptic cleft

storage of glycogen for neurons

Regulation of CNS internal environment

Release ATP to stimulate oligodendrocytes to produce myelin sheath

repair damaged nerves

What is the morphology of astrocytes?

star-shaped; bushy cells with many processes

What are gliomas?

tumors that arise form glial tissue; typically astrocytic or oliogodendrocytic

What are oligodendrocytes?

myelinating cell of the CNS; one will wrap around several axons

What is the function of myelin?

electrically insulates an axon to increase transmission speed

What are Ependymal Cells?

line the ventricles & central canal pf spinal cord

act a bit like epithelium in the CNS but lack a basement membrane

What function do the Ependymal cells of the choroid plexus serve?

secretion of cerebrospinal fluid

What are Schwann cells?

Myelinating cells of the PNS

What are Satellite cells?

accessory cells in the PNS ganglia, similar to astrocytes in the CNS

How do Axons regenerate in the CNS?

there are inhibitors to regeneration in CNS so regeneration is minimal

Why is regeneration minimal in CNS?

it is a complicated process & can be produced in a wrong way that can have negative affects

How are axons regenerated in PNS?

schwann cells promote regeneration through a variety of molecules

What are nerves?

Bundles of axons

What forms the nerve fiber?

Axon with glial cells

What do many nerve fibers form?

Fascicle

What surrounds the nerve fiber?

endoneurium

What surrounds the nerve fascicle?

perineurium

What layer of a nerve serves as the diffusion barrier & maintains the pressure & osmotic environment necessary for the fluid within the endoneurium?

The perineurium

What layer of the nerve contains fibroblasts & thick collagen strands that give tensile strength to the nerve?

The epineurium

What is endoneurium?

loss CT surrounding each individual nerve fiber

How do spinal nerves form?

arise from rootlets

What nerves come from the Dorsal side?

sensory

What nerves come from the ventral side?

motor

Rootles come together to form what?

roots

When the dorsal root is formed what happens?

it contains a swelling that contains cell bodies of sensory neurons

What is a mixed nerve?

contains both motor & sensory

As the nerve exits the vertebral column it splits again into

dorsal & ventral Rami

What does the Dorsal Ramus supply?

both motor & sensory innervation to the deep muscles & skin of the back

What does the Ventral Ramus supply?

supplies the muscles & structures of the upper &lower limbs, muscles & skin of the lateral/anterior regions of the trunk

What are the three types of ganglia?

Synaptic ganglia, Non-synaptic ganglia, & ganglion which also mean area of grey matter in CNS

What are autonomic ganglia?

sympathetic or parasympathetic ganglia

What type of neurons are present in sensory ganglia?

pseudo unipolar neurons

What is a Deratome?

a specific patch of skin that a spinal nerve is responsible for

What is a plexus?

a region of interconnecting nerves

What does a plexus do?

combines nerve fibers from multiple spinal levels (always ventral rami) into one larger spinal nerve

What are the 4 main plexuses?

Cervical, Brachial, Lumbar, & Sacral

Where do the nerves of the Cervical Plexus

How many nerves are involved in the Cervical Plexus?

6

Phrenic nerve C3-C5

nerve of the cervical plexus that innervate the diaphragm

What does the Brachial plexus Innervate?

mainly the upper limbs

How many major nerves are involved in the Brachial plexus?

5

Musculocutaneous nerve of the brachial plexus

motor to anterior arm & sensory to later forearm

Axillary Nerve of brachial plexus

motor to deltoid & teres minor & sensory to lateral arm

Radial Nerve of Brachial Plexus

motor to posterior arm & forearm & sensory to posterior forearm

Medial nerve of Brachial Plexus

motor to anterior forearm & thenar muscles

Ulnar nerve of the brachial plexus

motor to anterior forearm & hand

What does the lumbar plexus innervate?

the lower limbs

Iliohypogastric nerve of Lumbar plexus

sensory to pubic region

Ilioinguinal nerve of lumbar plexus

sensory to anterior-medial thigh & genital region

Femoral nerve of the lumbar plexus

motor to anterior thigh

Obturator Nerve of lumbar plexus

motor to medial thigh (ADDuctors)

What does the sacral plexus innervate?

innervates the lower limb (posterior)

Pudendal nerve of Sacral plexus

motor & sensory to perimeum

Sciatic nerve of sacral plexus

very large nerve with multiple spinal levels; innervates the posterior thigh & lower leg split into tibial & fibular nerves

What is ALS Amyotrophic Lateral Sclerosis?

A neurodegenerative disease that affects the motor neurons within CNS

Upper motor neurons

come from cerebral cortex & brain stem

Lower motor neurons

come from the spinal cord out to the periphery

Dysfunction in upper motor neurons causes?

spasticity: muscle stiffness

Hyperreflexia

weakness

Dysfunction in lower motor neurons can cause?

weakness, atrophy, fasciculations

Is ALS fast progressing?

Yes death within 3-5 years

What causes ALS?

no one truly knows but :

oxidative stress

inflammatory response

protein misfolding

viral

genetics

autoimmune disease