chapter 13 - nervous system (exam 2)

what is in the CNS

brain and spinal cord bathed in cerebro-spinal fluid

what is the integration center

in the CNS, takes info in to decide the action and sends action out to PNS

what is the PNS

cranial and spinal nerves that contain sensory and motor fibers

what is the job of the PNS 

connect the CNS to muscles, glands, and all sensory receptors and brings into to and from the CNS 

afferent division

sensory info arriving to the CNS

efferent division

motor and exiting the CNS

somatic division 

an efferent division that is conscious (skeletal muscles, you can control)

autonomic division

an efferent division that is unconscious (glands, smooth muscles, heart that you cannot control) 

what does the sensory function do

pick up information and change both inside and outside of the body

what is a change ?

any stimuli that will cause a reaction (temperature, vision, sound, oxygen, sugar)

what are the effectors ?

responsive parts that are outside of the nervous system (what responds)

what are neurons

one single nerve cell, functional unit

what are neuroglial cells ?

accessory cells that support, take care of, and nourish the neuron 

nissl bodies

ribosome clusters that give a gray appearance

axon hillock

connects the soma to the axon (part where soma tapers)

perikaryon 

region around the nucleus “cytoplams”

neruofibrils

cytoskeleton that extend into dendrites and axon that give the neuron its shape

how can impulses travel ?

dendrite → cell body → axon (can only travel in one direction)

axonal transport (a.k.a axoplasmic flow) 

movement of cellular materials through the axon (it has nothing to do with informational signaling, just cellular material) 

anterograde axonal transport

away from soma (neurotransmitters, organelles, nutrients)

retrograde axonal transports

toward soma (materials to be recycled and extracellular substances)

where are neurotransmitters made and stored ?

they are made in the soma and stored in vesicles in the synaptic terminal 

axoplamsa

cystoplasm of an axon

axolemma

plasma membrane of an axon

PNS neuroglial cells 

satellite cells and schwann cells 

CNS neuroglial cells

astrocytes, oligodendrocytes, ependymal cells, microglia

astrocytes

found between neurons and blood vessels

• supports

• metabolism

• regulation of ion concentration

• repair process

• nutrition

• guide neurons to targets

• form blood brain barrier

what is the blood-brain barrier 

determines what from the blood has access to the neurons 

oligodendrocytes

form the myelin sheath around the axons in CNS, clean up debris when injured (1 oligodendrocyte can provide myelin to multiple axons at the same time)

microglia

support neurons, phagocytosis, increase in number during injury or disease

ependymal 

have microvilli on luminal surface (inner), joined by gap junctions, produce and monitor cerebro-spinal fluid, line ventricles of brain and spinal cord 

satellite cells

cover parts of the soma that dont form synapse (to prevent overload of information), assist with the exchange of nutriens, isolate neuron from extraneous or unwanted stimuli

schwann cells

produce myelin in PNS (can only myeelinate a small part of an axon, need multiple to myelinate entire axon), protects contact from bare axons and causing a short circut

unmyelinated axons 

appear gray: in PNS many axons are separated by a single schwann cell (not individually wrapping), in CNS no glial cells 

myelinated axons 

appear white; oligodendrocytes myelinate several axons, schwann cells myelinate parts of one axon  

what is myelin

plasma membrane wrapped around the axon

neurilemma

part of shcwann cell that contains the cytoplasm

nodes of ranvier 

gaps in the myelin sheath where the action potential originates (jumps from node to node) 

how does myelin function ?

increases the rate of action potential because they only have to generate where node of ranvier is

irritability

ability to respond to a stimuli

excitability 

ability to transmit an impulse 

action potential (AP)

an electrical impulse changing the permeability of a membrane, the signal being carried down the neuron

nerve impulse

AP moving down an axon

how can an impulse travel faster ?

when the axon is myelinated or has a large diameter 

examples of neurotransmitters

achetylcholine (Ach), monamines, amino acids, peptides

enzyme that removes the Ach neurotransmitter

achetylcholinesterase (AChE)

how will an outgoing impulse be sent ?

if the net effect is excitatory and at threshold (if negative and postive go from -70 to +30 AP will go)

what is convergence

a single nerve may receive an impulse from 2 or more incoming fibers, all bring in + to allow AP to move down the nerve

divergence

allows impulse to be amplified and travel to different places (when touch something hot)

serial processing 

one neuron to another in a series 

parallel processsing

processing information from several neurons at once

reverberation

positive feedback continues the activity of the circuit

nuclei 

collection of neuron cell bodies with a distinct boundary 

center

collection of neuron cell bodies working together

tracts

bundles of axons

ganglia 

collection a neuron cell bodies 

nerves

bundles of axons

what is gray matter

non-myelinated material

what is white matter 

myelinated axons