520 intro & cns cells

what does rostral mean?

towards the ceiling

what does caudal mean?

towards the floor

what is a nucleus?

a group of neuronal cell bodies in the CNS

what is a ganglion?

a group of cell bodies in the PNS (outside the CNS)

what is a nerve?

a collection of axons in the CNS

tract (affarent/efferent)

what is a fasciculus?

a bundle of nerve fibers (axons)

what makes up white matter in the CNS?

axons

what makes up gray matter in the CNS?

cell bodies

what are the two classes of cells in the CNS and give a synopsis of what they do.

neurons: carry nerve impulses

neuroglial cells: support nerve cells (nutritionally and structurally)

are there more neurons or neuroglial cells?

neuroglial cells

what are neurons?

the structural and functional unit of the nervous system that are highly specialized for the encoding, conduction, and transmission of info

what is the cell body? what does it do? what is the cytoplasm of the cell body called?

the cell body (aka soma) contains the nucleus; it receives info from receptors and integrates the information

cytoplasm: perikaryon

what are dendrites? what do they do?

dendrites are short branches off the cell body that receive signals from other neurons

what is an axon? what does it do? what is the cytoplasm called?

an axon is a long process off the cell body that carries signals away from the cell body and to other neurons

cytoplasm: axoplasm

where is the nucleus located and what does it hold?

located in the center of the cell body and contains chromosomal DNA

what does the cell body contain?

nucleus

cytoplasm (perikaryon): mitochondria, ER, Golgi bodies, ribosomes

nissel granules: consist of rough ER and associated ribosomes

Neurofibrils: composed of a complex network of structural proteins called neurofilaments (plays a role in impulse propagation)

are dendrites uniform in structure?

no

what is the dendritic spine?

where it connects to other neurons

the postsynaptic part of the dendrite

does the axon of a nerve cell have a uniform diameter?

yes

long axons are motor or interneurons?

motor

short axons are sensory or interneurons?

interneurons

what are the terminal branches of an axon called?

telodendria: make contact with other neurons

what is the surface membrane of the axon called?

axolemma

what does the axoplasm contain?

neurofilaments, microtubules, mitochondria, and fragments of the smooth ER

what is the myelin sheath?

a covering on the axon that protects the neuron from damage and speeds up impulse conduction

is myelin sheath continuous?

no, there are gaps in each sheath that are called the nodes of ranvier

longer and/or thicker myelin sheath results in quicker or slower transmission?

quicker

where are the voltage gated sodium channels located at?

the nodes of myelinated axons

what does saltatory conduction mean?

impulses jump from one node to another making the conduction velocity higher

conduction velocity is dependent on what?

myelination

the diameter of the nerve fibers - larger diameter means faster conduction

what are the three types of neurons (functionally)?

afferent (sensory)

efferent (motor)

interneurons

what are afferent neurons and what do they do?

they are neurons that carry information from receptors in the body to the CNS

what are sensory neurons?

afferent neurons when the information reaches a conscious level

what are efferent neurons?

nerve fibers that carry information away from the CNS

what are motor neurons?

efferent neurons when the information reaches the effector organ (ex.muslce)

what are interneurons?

neurons in the CNS that connect one neuron to the other

what are the three types of neurons (structurally)?

unipolar: there is only one process that comes off the cell body, and from there it splits into two (axon and dendrites)

bipolar: there are two processes that come off the cell body (axon one way and dendrite the other)

multipolar: there are multiple processes that come off the cell body (one axon and multiple dendrites)

what type of structural neuron is the most common?

multipolar

where is each type of structural neuron found?

unipolar: only in dorsal root ganglia

bipolar: retina, cochlea of ears, nasal mucosa

multipolar: spinal motor neuron, Purkinje neuron, pyramidal cell

what are pyramidal cells and where are they found?

(multipolar) cells with a long axon found in the cerebral cortex

what are purkinje cells and where are they found?

(multipolar)cells where the dendrites look like a tree found in the cerebellum

in reference to unmyelinated neurons, what type of fibers play a role in slow (chronic) pain?

c fibers

what are glial cells?

an abundant (15 times more glial than neurons) type of supporting cell that provide structural and biochemical support (nutritional and environmental - remove waste)

do glial cells conduct impulses?

no

where are Schwann cells found and what do they do?

schwann cells are in the axon of neurons in the PNS and are responsible for the synthesis of myelin in the PNS

they also help to buffer excess extracellular K+ which prevents rampant depolarization

where are oligodendrites found and what do they do?

oligodendrites are found in the axons of neurons in the CNS and are responsible for the synthesis of myelin in the CNS

they are only found in the brain

unlike schwann cells, they can myelinate a segment of several axons

what are the functions of astrocytes?

1. blood-brain barrier: prevent circulatory chemicals from entering the brain and spinal cord
2. nutrition: transport nutrients, ions, and molecules from capillary to neurons (thought to be important communicators between neurons and capillaries)
3. healing: astrocytes act as scavengers to remove neuronal debris and seal off areas for healing
4. prevent excess depolarization: buffer excess K+
5. remove neurotransmitters from synaptic cleft
6. support: provide structural support and stability


1. developmental: act as a guide for outgrowth and migration in developing nervous system

what are ependymal cells and what do they do?

found in the ventricles of brain

they are ciliated columnar epithelial cells with tight junctions that line cavities of the neural tube forming a selective barrier between nervous tissue and ventricular fluid

ependymal cells form the?

choroid plexus which produces CSF by filtering components from the blood

what are microglia and what do they do?

they develop from the mesoderm and normally exist in small #s until needed

they become macrophages in response to injury or damage (act as scavengers because they have a phagocytic role in removing debris and damaged cells)

all glial cells (except microglia) develop from what?

ectoderm

give a synopsis of each glial cell.

oligodendrocytes: synthesis of myelin in the CNS

Schwann cells: synthesis of myelin in the PNS

ependymal cells: ciliated cells that form the choroid plexus

astrocytes: BBB, nutrition, healing, support, prevent excess depolarization, remove neurotransmitters, development

microglia: act as macrophages

differentiate gray matter and white matter in the spinal cord compared to the brain.

brain: grey matter (cell bodies) is outside and white matter (axons) is inside

spinal cord: grey matter (cell bodies) is inside and white matter (axons) is outside

what is the synapse? what are the two types and which is most common?

the junction between neurons where impulses are transmitted

electrical and chemical

chemical is most common

what is the electrical synapse?

the cell membrane of one neuron is very close to the other neurons cell membrane (makes a small gap) so the electrical signal easily jumps from one membrane to the other

what is the chemical synapse?

nerve impulses are transmitted via chemical substances from one cell membrane to the next

the presynaptic membrane is where the impulse comes from, the post synaptic membrane is where it goes to, and the synaptic cleft is the junction (gap)

what are the different types of chemical synapses?

axodendritic: axon-dendrite connection (most common)

axoaxonic: axon-axon connection

axosomatic: axon-cell body connection

what are the different types of neurotransmitters? give a small synopsis of each

acetylcholine: CNS and PNS; in the neuromuscular junction

serotonin: only CNS (mainly midbrain - raphe nucleus); sleep wake cycle; when concentration is low = depression

dopamine: only CNS (basal ganglia); important for movement; low dopamine related to Parkinsons

noradrenalin: in sympathetic post ganglionic nerve fibers and hypothalamus

glutamin acid: in the brain

GABA (gamma amino butyric acid): in the spinal cord and cerebellum

are neurons able to multiply?

most cannot because they do not have centromeres but some peripheral nerve fibers are able to regenerate because they contain the growth factor