CH. 11 Nervous Tissue - Dr. Jones

sensory input

monitoring stimuli occurring inside and outside the body

integration

processing and interperating sensory input

motor output

activation of effectors (whatever is responding to; muscles + glands) produces a response

central nervous system (CNS)

-brain and spinal cord

-control center of the body

peripheral nervous sytstem (PNS)

-cranial nerves and spinal nerves

-communication lines between the CNS and the rest of the body

enteric nervous system

walls of GI tract neurons

sensory (afferent) division

-info ARRIVAL

-SOMATIC(body) and VISCERAL(organs) sensory nerve fibers

-conducts impulses from receptors to the CNS

motor (efferent) division

-info EXITS

-motor nerve fibers

-conducts the impulses from the CNS to effectors (muscles and glands)

somatic nervous system

-part of the motor (efferent) division

-voluntary (somatic motor)

-conducts impulses from the CNS to skeletal muscles

somatic nervous system

neuron releases ACh to skeletal muscle

automatic nervous system

-part of the motor (efferent) division

-involuntary (visceral motor)

-conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands

automatic nervous system

organs responding to amount of food you eat

sympathetic division

automatic nervous system (ANS)

-mobilizes body systems during emergency situations

-fight or flight

parasympathetic division

automatic nervous system (ANS)

-conserves energy; at rest

-promotes nonemergency functions

-maintenance system (daily activity in body eg. digestion)

neurons

excitable cells that transmit electrical signals

-amitotic = cannot divide (has no centrioles)

-contract muscle

neuroglia (glial cells)

-support cells of neurons

-many cells that surround and wrap neurons

astrocyte

“star-shape” -most abundant

-(support brace) anchor neurons

-end of axon of neuron to clean around area

-chaperone of young neurons

-exchanges between capillaries and neurons (middleman)

-astrocytes

-microglial cells

-ependymal cells

-oligodendrocytes

main neuroglia cells supporting CNS neurons

microglial cells

oval in shape + spikey

-protector / immune system and defense of neuron

-migrate toward injured neurons

-local cop of CNS neuroglia

-phagocytosis foreign cells

ependymal cells

-circulate cerebral spinal fluid (CSF)

-contains cilia to create a moving current

oligodendrocyte

-makes protective myelin sheath for CNS

-minimizing weakening of Action Potential before it gets to target

myelin sheath

insulator surrounding nerve fibers of either CNS or PNS

satellite cells

-surround neuron cell bodies in PNS

-same function as astrocyte of CNS

schwann cells

-surround peripheral nerve fibers of PNS and form myelin sheaths around thicker nerve fibers

-same function as oligodendrocytes of CNS

cell body , soma

contains spherical nucleus with nucleolus, surrounded by cytoplasm

-has free ribosomes and golgi body

-rough ER (nissl bodies)

nuclei

clusters of neuron cell bodies in CNS

ganglia

clusters of neuron cell bodies in PNS

dendrites

“free brach extensions”

-process that extend from cell body of neuron

-receptive area allow neurons talk to each other; electrical signal come into __

axon

transmitting portion of neuron

nerve fibers

long axons

axon collaterals

axons branches ; teminal branches

axon terminal

knob-like distal ends of axon

tracts

bundles of axons in CNS

nerves

bundles of axons in PNS

axolemma

axon plasma membrane

neurotransmitter

signaling chemicals

-Electricity does not jump open space so it needs a ___

anterograde movement

Axonal Transport

transport of cellular materials TOWARD axon terminal AWAY cell body

ex. mitochondria, cytoskeletal elements, membrane components, enzymes

retrograde movement

Axonal Transport

transport of cellular materials AWAY axon terminal TO cell body

ex. organelles to be degraded, signal molecules, viruses, bacterial toxins

myelin sheath

-fatty material that wraps around the AXON

-insulator (prevents electrical signals from going out randomly) ; physical protector

-increases the speed of electrical signals [faster electrical signal]

nodes of ranvier

gaps in between adjacent Schwann Cells (PNS)

oligodendrocyte

-can branch and insulate multiple neurons

-CNS neuron cell

schwann cells

-single neuron has multiple myelination cells

-PNS neuron cell

multipolar neurons

many processes extend from cell body

-all dendrites except for single axon

-most abundant in body; major neuron type in CNS

bipolar neurons

two processes (1 axon, 1 fused dendrite)

-found in retina, ear, olfactory mucosa (nose) ; perceive chemical, air, light

unipolar neurons

one process (T-shaped process exits cell body and divides into 2 branches of axons)

-peripheral process

-central process

peripheral process

unipolar neuron branch

-associated with sensory receptor

central process

unipolar neuron branch

-branch enters CNS > transmitter to brain or spinal cord

multipolar neuron

neuron found in cerebellum; responsible for coordination of movement (balance)

sensory (afferent) neurons

transmits impulses from sensory receptors to CNS (brain and spinal cord)

-almost all unipolar neurons

motor (efferent) neurons

-exiting brain and spinal cord (CNS)

-carry impulses from CNS to effectors

-multipolar neurons

interneurons

middle man

-shuttle signals through CNS pathways

-processing info coming in to determine what communication of motor neurons go out (THINKING NEURON)

resting membrane potential

-always active

-the potential difference (-70mV) across the membrane of a resting neuron

voltage

what we measure electrically

current

movement of voltage flow

resistance

how easy it is for voltage to move

leakage channel

type of plasma membrane ion channel that is ALWAYS OPEN (slightly like a creak of a door)

chemically (LIGAND) gated channels

type of plasma membrane ion channel that open with binding of a specific neurotransmitter / chemical

ex. ACh

voltage gated channel

type of plasma membrane ion channel that open and closes in response to membrane potential

electrochemical gradient

determines where ions diffuse into or out of cells

-concentration gradient (high to low concentration)

-electrical gradient (ions move toward opposite electrical charge)

polarized

the membrane is said to be ___

(negatively charged relative to outside)

K+

what chemical plays the most important role in membrane potential?

-cell cytosol has higher concentration of it

stabilize resting membrane potential; constantly trying to reverse what is happening to K+

what is the role of the sodium potassium pump?

graded potential

small impulse signal

-operate locally over short distances

action potential

big impulse signal

-operate long distance

strength: ALL or NONE

depolarization

Decrease in membrane potential (move toward zero and above)

-inside of membrane become less negative / more positive than resting membrane potential

-probability of producing impulse increases

hyperpolarization

HIGH repolarization; increase in membrane potential (away from zero)

-inside of membrane become more negative / less positive than resting membrane potential

-probability of producing impulse decrease

hyperpolarization

what membrane potential change is HARDER for a neuron to fire an electrical signal / action potential?

action potential

brief reversal of membrane potential with a change in voltage of ~100mV

action potential

-70mV to +30mV

activation gates

closed at rest; open with depolarization allowing Na+ to enter cell

inactivation gate

open at rest; block channel once it is open to prevent more Na+ from entering cell

two gates

-activation gate

-inactivation gate

how many voltage sensitive gates does Na+ have? What are they?

one gate

-close at rest

-open slowly with depolarization (less neg inside, positive outside)

how many voltage sensitive gates does K+ have?

depolarization

voltage-gated channels open; Na+ rush to cell

-inside cell is less negative/more positive

-large action potential spike if threshold (-55mV) is reached; open up all Na+ channels

repolarization

channels are inactivating, voltage-gated channels open

-Na+ channel inactivation gates close

-Na+ decline to resting rate

-AP spike stop rising

-voltage-gated K+ channels open; K+ exits cell down its electrochemical gradient

-MEMBRANE RETURNS TO RESTING MEMBRANE POTENTIAL

hyperpolarization

some channels remain open and channels reset

-some K+ channels remain open, allowing excessive K+ efflux

-inside membrane become MORE NEGATIVE than resting state

-slight dip below resting voltage of -70mV

-Na+ channels reset

propagation

how action potential travels

-”domino effect” > only can go forward

-AP impulse not strong enough to make to end target, so it keeps firing AP impulse down length of axon to reach target

frequency

difference in action potentials

-how many AP impulses firing difference tells the body what is more important to target

absolute refractory period

-time of opening Na+ channels until resetting of channels

-ensure each AP is all-or-none event

-enforce one-way transmission

relative refractory period

-follows absolute refractory period

-most Na+ return to resting state, some K+ channels still open

-REPOLARIZATION OCCURING to reset

larger axon diameter

-less resistance to local current flow

-faster impulse conduction

nonmyelinated axon

slower conduction ; CONTINUOUS CONDUCTION

myelinated axon

faster conduction ; SALTATORY CONDUCTION

salatare = to leap

no voltage-gated channel

what causes a voltage to decay in plasma membrane?

multiple sclerosis (MS)

-autoimmune disease mainly affects young adults

-NO myelin sheath protection

-lose muscle control or muscle become weak, thus losing control of urination

-progressive disease so it gets worse over time

-no cure; only maintanence

synapse

where the neuron meets its target

presynaptic neuron

neuron conduct impulse toward synapse (send info) > does the talking

postsynaptic neuron

neuron transmitting electrical signal AWAY from synapse (recieve info)

chemical synapse

most common type of synapse

-Specialized for release and reception of chemical messengers neurotransmitters

excitatory postsynaptic potential (EPSP)

turn on

inhibitory postsynaptic potntial (IPSP)

turn off

-reuptake by astrocytes or axon terminal (repack)

-degregation by enzymes

-diffusion away from synaptic cleft

how is neurotransmitter effect terminated after getting attention of a recieving cell?

biogenic amines

-Catecholamines – dopamine, norepinephrine (NE), and epinephrine

-indolamine - serotonine and histamine

-role in emotion and biological clock

gamma aminobutyric acid (GABA)

the ONLY true inhibitory receptor!

-quiets others, makes them stop impulse

excitatory

is ACh inhibatory or excitatory at neuromuscular junction in skeletal muscle?

inhibitory

is ACh inhibatory or excitatory in cardiac muscle?

apoptosis

programmed cell death

(when axons do not form synapse with their target)

neuropeptide

endorphin, the body’s natural painkiller is an example of what kind of neurotransmitter?

ACh, biogenic amines, amino acids, neuropeptides

neurotransmitters