A&P Ch. 11: Nervous System and tissue

SPC BSC 2085: A&P Ch 11

brain and spinal cord

the central nervous system includes the __

cranial nerves, spinal nerves, ganglia

the peripheral nervous system includes the __

somatic

refers to the skin of the human body

Astrocytes

most abundant in CNS, many processes that attach to capillaries and neurons

Microglial cells

defensive cells in CNS, phagocytes that monitor health of neurons

Ependymal cells

line CSF CNS cavities, have cilia that line cavities

Oligodendrocytes

CNS neuroglial cell that produces myelin sheath on multiple axons

neuroglia

supporting cells of the nervous system, “glue”

satellite cells

surround the cell body of the neuron

Schwann cells

form myelin sheaths surrounding nerve fibers

Soma

cell body; no centrioles, Nissl bodies

Dendrites

short, tapering receptive regions, points of synapses with other neurons, electrical signals conveyed as graded potentials, always unmyelinated

Axons

generate nerve impulses called action potentials, myelinated

Node of Ranvier

myelin sheath gaps between adjacent Schwann cells

nucleus

a collection of neuron cell bodies in the CNS

ganglion

a collection of neuron cell bodies in the PNS

tract

a bundle of axons in the CNS

nerve

a bundle of axons in the PNS

myelin sheath

Whitish, fatty (Protein-lipoid), segmented sheath around most long axons

function of myelin sheath

function: Protection of the axon, Electrically insulating fibers from one another, Increasing the speed of nerve impulse transmission

multipolar neuron

many processes extend from the cell body. All are dendrites except for a single axon

bipolar neuron

two processes extend from the cell body. One is a fused dendrite, the other is an axon

unipolar neuron

one process extends from the cell body and forms central and peripheral processes, which together comprise an axon

positive

the charge outside of the plasma membrane is

negative

the charge inside the plasma membrane is

-70mv

the average resting membrane potential for neuron cells

Membranes

built in potential energy like a battery, have an electrochemical gradient due to the differences in chemicals and charges

Chemical/Ligand

open or close when appropriate chemical binds

Voltage Gated channels

pen or close in response to changes in membrane potential (voltage)

dendrites, somas

where are chemical gated channels located

axons

where are voltage gated channels located

Depolarization

membrane potential become less negative; Increases the probability of a nerve impulse

Hyperpolarization

membrane potential becomes more negative; Reduces the probability of a nerve impulse

excitatory post synaptic potential

what does EPSP stand for?

inhibitory post synaptic potential

what does IPSP stand for?

decay

graded potentials _ (decrease only with distance)

action potential

a brief change in membrane potential in a patch of membrane that is depolarized by local currents

axon

where do action potentials occur?

depolarization

in action potential, _ is caused by Na+ flowing into the cell

repolarization

in action potential, _ is caused by K+ flowing out of the cell

hyperpolarization

in action potential, _ is caused by K+ continuing to leave the cell

all or none phenomenon

action potentials either happen completely or not at all

more

strong stimuli generate __ APs than weaker stimuli

frequency

The CNS discerns stimulus intensity by the __ of impulse transmission

absolute refractory periods

time periods once Na gates are open until they return to resting state- neuron is incapable of responding to another stimulus no matter how strong (no AP)

resting state

Na gates have to be in their __ to be responsive

relative refractory period

most sodium gates are closed, K+ still open. Repolarization is occurring, but threshold level is elevated. Only stronger than usual stimuli can generate an AP

axon diameter, myelin sheaths

rate of impulse propagation is determined by

saltatory conduction

presence of myelin sheath dramatically increases impulse speed

continuous conduction

unmyelinated impulse conduction

larger

the __ the diameter of the axon, the faster the impulse

Multiple sclerosis

Nerve fibers are severed/Myelin sheath in the CNS become nonfunctional; symptoms include visual disturbances, weakness, loss of muscular control, and urinary incontience. affects mainly young adults

synapse

a junction that mediates information transfer from one neuron to another neuron or an effector cell

presynaptic neuron

conducts impulses toward the synapse;

postsynaptic neuron

transmits impulses away from the synapse; receives the signal

trigger zone

high concentration of Na channels, depolarization happens and AP begins here

Electrical Synapses

Correspond to gap junctions found in other cell types. Intercellular protein channels, permit ion flow from one neuron to the next. Less common than chemical synapses

brain, embryonic tissue

where are electrical synapses commonly found before they’re replaced by chemical synapses

chemical synapses

specialized for the release and reception of neurotransmitters.

axonal terminal, receptor region

a chemical synapse is typically composed of what two parts

axon terminal

presynaptic neuron, contains synaptic vesicles

receptor region

postsynaptic neuron, located on dendrite or soma

dendrites, cell body

location of graded potential

axon hillock/ trigger zone

location of action potential

short distance

distance traveled in a graded potential

long distance

distance traveled in an action potential

various sizes

amplitude (size) of graded potentials

always the same size

amplitude (size) of action potentials

chemical or sensory stimulus

stimulus for opening ion channels in a graded potential

voltage

stimulus for opening ion channels in an action potential

absent

is positive feedback absent or present in a graded potential

present

is positive feedback absent or present in an action potential

voltage independent

repolarization in graded potential is __; comes when stimulus is no longer present

voltage regulated

repolarization in action potential is __; occurs when Na+ channels inactivate and K+ channels open

Synaptic Delay

Neurotransmitter must be released, diffuse across the synapse, and bind to receptors. The rate-limiting step of neural transmission

.3-.5 ms

The time needed for synaptic delay

EPSP

depolarization that spreads to initial segment of axons; moves membrane potential toward threshold for generating an AP