CH11 AP 1 fundamentals of nervous system and nervous tissue

function of the nervous system

sensory input, integration, motor output

sensory input

monitors changes that occur inside and outside the body

sensory input sends to

brain but sometimes spinal cord

integration

processing and interpretation of input information

motor output

message being sent over and responded to

components of the nervous system

CNS and PNS

CNS function

responsible for interpreting sensory input and deciding motor output

PNS function

allows information to be sent between CNS and body

if no PNS

no motor function, no regulation, brain makes things up (hallucinations etc)

general nervous cells

neurons, neuroglia

neurons

specialized nerve cells that can respond to stimuli and transmit electrical signals

neurons that do nothing

die

neuroglia function

provide support and maintain neurons

types of neuroglia

astrocytes, microglia, ependymal, satellite cells, oligodendrocytes, schwann cells

astrocytes location

CNS

astrocytes function

help with clean up immediately around neuron and energetically

shape of astrocytes

star shaped with projections from membrane to connect

astrocytes connected to

to connect AROUND neurons, nerve endings and surrounding blood capillaries/vessels

most abundant glial cells

astrocyte are most common

astrocytes in utero

allow immature nerve migration

neurons cannot be exposed to

cannot be exposed to blood

main examples of astrocyte cleanup

leaked K+ and neurotransmitters

microglia location

CNS

microglia function

contact nearby neurons to monitor neuron health

microglia shape

finger like extensions

dead neurons cause

loss of brain function

migration of microglia

toward impaired neurons and transform into macrophage and phagocytize neuron

immune system has little access

little access to spinal cord

reason immune system doesnt have access to spinal cord

protection from diseases

ependymal location

CNS

ependymal cells have

have cilia

ependymal cell function

lines central/vertebral cavity to circulate CSF within

cilia of central cavity

to move CSF

function of CSF

protecting brain structures

satellite cell location

PNS

satellite cell function

support and protect via wrapping neuron cells in PNS

satellite forms

form wall and blood supply to protect cell body

oligodendrocytes location

CNS (myelin)

oligodendrocytes function

insulates via myelin sheath for neurons

Schwann cells function

insulate via myelin sheath

characteristics of neurons

longevity, amitotic, metabolism

metabolism of neurons

very active

neurons need what to make glucose

high o2

neurons produce

proteins, glucose and neurotransmitters

low CNS function

alzheimer’s, parkinsons, ALS

trauma or disease kill neurons

permanently

most cell body location

in the cns and protected by bone

clusters of cell bodies in CNS

nuclei

dendrites

main receptive region with high SA

axon

single nerve fiber to transmit away from cell body

bundles of axons in CNS

tracts

bundles of axons in PNS

called nerves

axon length vs dendrites

axon is always longer

PNS axon length

2.5 feet, longer than CNS axon

cells that make myelin sheaths

schwann and oligodendrocytes

function of myelin shealths

insulation

location of myelin sheaths

only on axon portion

are all axons myelinated

not are are myelinated

do pns shealths touch

they do not touch

formation of sheaths

multiple Schwann cells

classification of nerves

direction they travel relative to CNS

sensory afferent neuron

transmit from body to CNS

motor efferent neurons

from cns to body/effector organs

interneurons

found between sensory and motor neurons in CNS

membrane potential

difference in electrical charge across the plasma

types of resting potential

graded vs action

ion channels

selective protein proteins in plasma membrane that forms “channels” to allow passage of ions into/out of cell

types of ion channels

leakage and gated channels

leakage channels

always are open, K+ leaky channel

gated channel types

chemical, voltage and mechanical

chemically gated channels

only open when a certain chemical/neurotransmitter bind to protein

chemically gate opens

free flow

voltage gated channel

open and close in response to changing membrane potentials

mechanically gated channel

open in response to physical deformation of receptor ( not lots in CNS)

result of changing membrane potential

depolarization

define depolarization

inside is more positive, lots of Na+ ions, less potential and more excitation, -55mV

excitation

more positive inside of neurons and more likely to send message

hyperpolarization

inside become more negative, ions leave cell, higher difference to inhibit neuron

graded potentials

magnitude varies directly with stimulus strength

longer stimulus causes

strong graded potential

strong stimulus defined by

by frequency of stimulus

function of graded potentials

needed to initiate nerve impulse around dendrites

action potentials

the literal message

action potential produced by

by neurons and muscle cells

all action potentials have

have consistent strength

do action potentials delay with distance

do not delay with distance

only depolarizing

move from -70 mV to +30 mV

max length of action potentials

3 feet

generation of action potential

only at axon

activated voltage gated

voltage sensitive, opens at depolarization

main ion of ECF

NA+

inactivation voltage gate

blocks channel to prevent Na+ movement

voltage gate has only

only K+, 1 gate, opens at repolarization

resting membrane potential gates

voltage gated channels are closed, K+ leaky is open to increase permeability

-55 mV leads to

action potential becomes self-generating because Na+ flips open

depolarization reversion

brief reversible of membrane potential to +30 mV

repolarization

action potential ends, Na+ channel ends, K+ gated open

effect of no end to action potential

CNS gets confused

K+ voltage gated is open to long

leads to -90mV

hyperpolarization voltage

-90mV