please

CNS

brain and spinal cord

PNS

nerves, ganglia, sensory receptors, plexuses

Divisions of the PNS

sensory (afferent) and motor (efferent)

afferent (sensory)

-sensory organs to CNS

-cell bodies located in ganglia near spinal cord/cranial nerve origin

efferent (motor)

CNS to effector (muscle, gland)

Divisions of efferent division of PNS

somatic motor nervous system and autonomic nervous system

somatic nervous system

CNS to skeletal muscle

neuron cell bodies located within CNS; axons extend to NMJ

somatic reflexes

autonomic nervous system

CNS to smooth/cardiac muscle & glands

provides subconscious control

2 sets of neurons: 1st neuron within CNS axon extends to autonomic ganglia

2nd neuron in autonomic ganglia send axon to effector

visceral reflexes

Divisions of ANS

sympathetic, parasympathetic, enteric

sympathetic

prepares body for activity/stress "fight or flight"

parasympathetic

regulates resting/vegetative functions; return to homeostasis

"rest and digest"

enteric

plexuses within the wall of the digestive tract. Can control the digestive tract independently of the CNS, but still considered part of ANS because of the parasympathetic and sympathetic neurons that contribute to the plexi.

CNS

processes information, initiating responses, integrating mental processes

PNS

detect stimuli, transport information to/from CNS in the form of APs

neuroglia

cells that support and protect neurons

1/2 of brains weight

neurons

receive stimuli/conduct APs

cell body (soma)

contains the nucleus and other parts of the cell needed to sustain its life

dendrites

short branched processes with extensions (dendritic spines)

carry info towards cell body

axon

nerve fiber- begins at axon hillock, single process

carry info away from cell body

trigger zone

where action potential is generated

nissl bodies

found within cell body; specialized areas of RER to protein synthesis

organization of NS

Receptor -> Sensory NS -> CNS -> Motor NS -> Effector

within axon

axoplasm, axolemma, telodendria, presynaptic terminals

anterograde

away from the cell body

retrograde

up axon to cell body

herpes/rabies

interneurons

between sensory & motor neurons in the CNS

Astrocytes

star-shaped cover surfaces of BVs, neurons, Pia mater

regulate extracellular fluid around neuron

important in blood-brain barrier structure/function; protect CNS

blood-brain barrier

very selective, protects CNS from toxins

non polar material pass through barrier ex. nicotine and alcohol

polar materials can't pass without help

Parkinson's disease

lack of dopamine causes decreases muscle control increased shaking

Levodopa crosses blood-brain barrier instead of dopamine

ependymal cells

line cavities of the brain and spinal cord, circulate cerebrospinal fluid

choroid plexus

Specialized ependymal cells and capillaries

Secrete CSF into ventricles

some cells contain cilia to move CSF

microglia

small cells, mobile and phagocytic

respond to inflammation and the presence of disease producing organisms

oligodendrites

form sheaths around axons within CNS

Schwann cells (neurolemmocytes)

form myelin sheath around axons within PNS

satellite cells

specialized Schwann cells that surround soma in ganglia

give support, provide nutrients, protect against heavy metal poisoning

myelin sheath

phospholipid-rich material, insulates axon, white appearance

formed by oligodendrites(CNS) & Schwann cells (PNS)

unmyelinated axon

AP must travel along entire length of CM

nodes of ranvier

gaps in the myelin sheath

saltatory conduction

the jumping of action potentials from node to node

Type A fibers

large diameter, myelinated, conduction speed = 15-120 m/s

ex. motor neurons for rapid response

Type B fibers

-medium diameter

-lightly myelinated

-conduction speed = 3-15 m/sec

Type C fibers

small diameter, unmyelinated, conduction speed 2m/sec or less

Types B&C

found primarily in ANS, used to maintain homeostasis

white matter

myelinated axons

gray matter

neuron cell bodies + unmyelinated axons

integrative functions

nerve tracts

myelinated axons (white matter) of CNS

nerves

myelinated axons of PNS

nuclei

cell bodies in CNS

ganglia

cell bodies in PNS

endoneurium

delicate connective tissue around individual nerve fibers in nerve

perineurium

surrounds group of nerve fibers forming a fascicle

epineurium

surrounds the entire nerve

RMP (resting membrane potential)

a difference in electrical potential across the membrane of a nerve cell during an inactive period

-70mv

ion channels

protein pores in CM specific for single ion movement

voltage gated channels

open and close in response to changes in membrane potential

ligand-gated channels

channel that opens when a neurotransmitter attaches

local potential

a depolarization event; result of a stimulus applied at 1 point on cell

ex. of graded potential

summation

adding together of local potentials to result in larger depolarization

propagation

spread of local potential over CM

decreases in magnitude as it spreads over CM away from point of origin

not good for long distances

action potential

when local potentials cause depolarization to a level termed the threshold potential

all or none fashion

depolarization phase

membrane potential moves away from the resting membrane potential and becomes more positive

sodium channels open

repolarization phase

-MP returns to the RMP

-MP becomes more -

-Na+ channels close, K+ channels open

afterpotential

-slight hyperpolarization that occurs with repolarization

-Na+/K+ pump reestablishes normal Na+/K+ concentrations after AP

refractory period

decreased sensitivity to further stimulation once AP has occured

depolarization/repolarization cycle must be completed before 2nd AP is generated

absolute refractory period

complete insensitivity no APs will be generated no matter how strong 2nd stimulus is

relative refractory period

after the absolute refractory period has passed a stronger than threshold stimulus can initiate a 2nd AP

propagation of AP

-AP spreads to adjacent regions along the CM

-depolarization occurs upstream; repolarization occurs behind travelling AP

AP frequency

strength of stimuli affects the frequency of APs

sub threshold stimulus --> local potential

threshold stimulus--> local potentials undergo summation and result in single AP

submaximal stimulus- greater than threshold but less than maximal stimulus results in increases AP frequency

maximal stimulus (or supramaximal stimulus) results in AP frequency reaching its maximal rate

AP propagation

when threshold is reached, voltage gated sodium channels open in a domino effect along axon resulting in a wave of depolarization that spreads downstream

in myelinated axons APs jump from node to node (saltatory conduction)

in unmyelinated axons entire length of axolemma must undergo depolarization

APs travel faster in myelinated axons

synapse

space over/through which AP travels between cells

electrical synapse

gap junctions; cells are close enough together to allow direct "jumping" of AP from cell 1 to cell 2

chemical synapse

neurotransmitter released by cell 1 and diffuses across space (synapse), binds to cell 2 receptors & causes depolarization

accommodation

adjustment/return to the RMP even though stimuli continue

monoamine oxidase (MAO)

deactivates norepinephrine

Amphetamines

increase release of NE, block NE reuptake, inhibit MAO results in increased alertness

Neuromodulators

pre/postsynaptically influence the likelihood of an AP being transferred from presynaptic to postsynaptic side of synapse

glutamate

excitatory neurotransmitter; with a stroke increased release/binding & nitric oxide production resulting in nerve damage

possible to reduce stroke damage by decreased NO production

EPSPs (excitatory postsynaptic potentials)

when NT and their receptors cause depolarization

IPSPs (inhibitory postsynaptic potentials)

when NT & receptor binding cause hyperpolarization

excitatory neurons

release NT producing EPSPs

Primarily due to increased sodium permeability

local anesthetics decreases sodium permeability and block EPSPs

inhibitory neurons

-release NT producing IPSPs, result from increased permeability to chloride(moves into cell) or potassium (moves out of cell)

axo-axonic synapse

axon of 1 neuron synapses with presynaptic terminal of another neuron

neuromodulators release at this point influences the NT released from the 2nd axons terminus

presynaptic inhibition

decreased NT release ex. endorphins/enkephalins

lead to decreased awareness of pain

presynaptic facilitation

increases neurotransmitter release ex. glu and NO

glu release stimulates NO production and more glu release

spatial summation

2 APs arrive at same time at 2 different presynaptic terminals that synapse with same postsynaptic neurons

temporal summation

2 APs arrive close together at the same presynaptic terminal

1st AP doesn't finish and 2nd adds to it

convergent pathways

many converge and synapse with smaller number of neurons

divergent pathways

small number of presynaptic neurons synapse with large number of postsynaptic neurons

oscillating circuit

arranged in a circular fashion; prolongs response due to afterdischarge

spinal cord

link between brain and PNS

runs from foramen magnum to L2 region

contains enlargements in cervical and lumbosacral region

CSF fills central canal and subarachnoid space

protected by 3 meningeal layers: dura mater, arachnoid layer, pia mater

spinal nerves

31 pairs

8 cervical

12 thoracic

5 lumbar

5 sacral

1 coccygeal

white matter

consists of nerve tracts= fasciculi

myelinated axons in fasiculi carry same type of information

ascending-sensory

descending- motor

funiculi- columns of white matter

funiculi

columns of white matter in the spinal cord

ventral, dorsal, lateral

anterior median fissure and posterior median sulcus

clefts partially separating L&R

gray matter

nerve cell bodies and dendrites

Dorsal horns

axons of sensory neurons synapse here

ventral horn

contains cell bodies of motor neurons

lateral horn

autonomic function

dorsal root ganglion

collection of cell bodies of unipolar sensory neurons forming dorsal roots

reflex arcs require

1. sensory receptor

2. afferent/sensory neuron

3. association neuron

4. efferent/motor neuron

5. effector (muscle/gland)