physio ch 8

neurons with processes secrete what?

neurotransmitters

whats in the CNS

brain and spinal cord

* nerves can't recover

peripheral nervous system

nerves can be recovered

afferent (sensory) neurons

signal goes to nervous system

efferent neurons (motor neurons)

take information from the brain to the rest of the body

autonomic nervous system

the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms.

action potential

spike, nerve impulses, and conduction signal

autonomic nervous system (ANS)

visceral nervous system

Axon

nerve fiber

axon transport

axoplasmic flow

axon terminal

end of axon

* synaptic knob, synaptic bouton, presynaptic terminal

axoplasm

cytoplasm of an axon

cell membrane of an axon

axolemma

glial cells

neuroglia

Interneurons

association neuron

rough ER

nissil substance, nissil body

neuron structure

soma, axon and dendrites

things about CNS

* the neurons don't divide
* are post-mitotic
* have a high metabolism
* need oxygen
* can go 4 mins without oxygen

neurons will have a soma, 1 axon and can have \_____ dendrites

many

axon hillock: is always just one

where the soma and axon connect

what can branch off

dendrites

the bouton is the end of

axon

dendrites and soma can make more only when

you are sleep

dendrites are thick in the beginning while axons

stay the same

why can't axon reproduce

because there are no ribosomes in the hillock to the axon

nerves are axons bundled with

connective tissue

the cell body is the

control center

Dendrities

receive incoming signals

axons

carry outgoing signals

fast axonal transport

moves organelles at a rate of up to 400mm/day

anterograde transport

from the cell body to the axon terminal

retrograde transport

from the axon terminal to the cell body

slow axonal transport

moves material by axoplasmic flow at 0.2-2.5 mm/day

Synapse

is the region where an axonal terminal meets its target

most brain caner is connected to

neuroglia

CNS neuroglia

astrocytes, oligodendrocytes, microglia, ependymal cells

PNS neuroglia

Schwann cells and satellite cells

Astrocytes

secrete growth factors and filters blood (forms perivascular) and recycles neuronal debris

microglia

Act as phagocytes, eating damaged cells and bacteria,

* clean up debris

Oligodendrocytes

produce myelin sheets in CNS, 1:20 sheets

ependymal cells

produce cerebrospinal fluid

water type

Schwann cells

secrete growth factors, provide myelin

satellite cells

immune

* protect

How do neurons communicate?

through synapses

axon to muscle fiber

neuromuscular junction (NMJ) axiomatic synapse and axoaxonic synapse

if the cell body dies

neuron dies

regeneration may occur in PNS

but not in CNS

in CNS and PNS injury to the \____ can repair and \____

dendrites and cell body

stem cells repair

* axoplasm leaks out and seals the damaged and attached segments of the axon swells
* Schwann cells release chemical signals alerting of tissue damage
* Schwann cells secrete neurotrophic factors to keep the cell body alive and encourage axon regeneration

in CNS if an axon is damaged

* astrocytes increase the number of proliferating
* increase size hypertrophy
* increase growth factors secretion
* this creates an astrogates scar so it can not grow and will stay there forever

If PNS is damaged

* schwann cells: increases number, increase size, and increase GF
* create ==collagen== sheaths
* remyelinated

Nersnt Potential

is the electrical equilibrium for a single ion

Vx

is singular

Vm

is entire

cells resting permeability

K, Na, and Cl

changes in a membrane's permeability results in

ion movement

movements creates an

electrical signal

graded potentials

can add up to voltage because of speed

action potentials

can't add up voltage

* super fast

graded potential

lose strengths as they move through the cell due to current leak to cytoplasmic resistance

at the hillock

it becomes more negative inside because K leaves the cell through the leaky gates but the ATP will pump it back in

the action potential is

a domino effect but can use stimulus has to be strong enough to go to bouton from hillock

action potential beings when

graded potential reaching the trigger zone depolarizes the threshold

\-The rising phase of the action potential: voltage-gated Na channels open and Na entry depolarizes cell

\-The falling phase of teh action potential: at peak Na channels close, slower voltage-gated k channels open

\-K exit repolarizes ten hyperpolarizes the cell

\-Voltage-gated K channels close less K leaks out of the cell

\-Cell return to resting membrane

2 types of voltage along the axon

* sodium voltage-gated channels (2)
* K voltage-gated channels (1)

refactory

is when all gates are closed and are one way

Lidocaine, Novocaine, and benzocaine

temporarily block sodium-gated channels and is responsible for upstroke

venum

the H gates stay the same so its responsible for the downstroke

chemical factors alter

alter electrical activity if the K levels are messed up

Normokalemia

is normal K levels, but if the stimulus doesn't hit the threshold, then it won't have an action potential

* if above threshold stimulus will fire an action potential

hyperkalemia

is a lot of K

\-it can trigger an action potential

* makes neurons less likely to fire an action potential in response to a stimulus

nerocrine can also means

neuron transmitter

Acetylcholine (ACh)

\-made by acetyl coa and chlorine

* ach used in muscle NMT
* -long term memory
* -muscle contraction

nicotinic receptors (ach)

is a substrate, good at mimicking fast, but it doesn't change the cell

muscarinic receptors (ach)

can be found in shrooms it affects the slow so affects the cell

agonist

substitute Ach

Amines-modified amino acids

\-Norepinephrine is for short-term memory and stress

\-tryptophan-> 5' hydroxytryptophan (5HT is serotonin, sleep-wake conscious) and most abundant in turkey

\-Dopamine: suppresses unwanted motor movement. A decrease is Parkinson's disease which shows unwanted motor while an increase in addiction

\-Alpha is fast, and beta is ~~slow~~

amino acids can be

neurotransmitter

glutamate

excitatory-\> brain (fast and slow positive) and is responsible for adult Seizures

Aspartate

excitatory-\> brain

Gamma-aminobutyric acid (GABA)

inhibitory (negative fast or slow)-\> brain, also for baby seizure

Glycine and D-serine

enhance the excitatory effect of glutamate

Enkephalins and endorphins

suppress pain

Opioid

make that naturally

Other neurotransmitters

peptides, purines, gases, and lipids

Purines are

ATP

gases (toxic gas) can

diffuse in the cells

synaptic communication

1. An action potential depolarizes the axon terminal
2. The depolarization opens voltage-gated Ca channels and Ca enters the cell
3. Calcium entry triggers exocytosis of synaptic vesicle contents
4. Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell
5. Neurotransmitter binding initiates a response in the polysynaptic cell

not enough Ca

then makes bone weak and muscles contractions and after transmission

NT are released from

exocytosis

where are the Ca voltage channels

the presynaptic membrane

Synaptic communication: neurotransmitter termination

1. Neurotransmitter gets recycled/reused
2. Enzymes that break them apart Ach-> choline
3. Neurotransmitters, once released can go back into the blood

active potential

* produced by voltage-gated channels
* -move fast and one way
* presynaptic

postsynaptic cell

* produce by ligand-gated channels
* -2 types: fast and slow
* slow makes permanent changes to the cell
* graded potential
* -postsynaptic

Proteins start a cascade of events to start

transcription for the slow, which causes preset changes to the cell and 2nd messenger system

the dendritic spine

It gives more space for the neurons

Slow synaptic potentials involve

G-protein coupled receptors and second messenger

Fast synaptic potentials involve

the opening of ion channels

An excitatory postsynaptic potential (EPSP) is

depolarizing

An inhibitory postsynaptic potential (IPSP) is

hyperpolarizing

(fast) Ion channels open:

More Na in= EPSP (excitatory depolarization)

More K out of Cl in= IPSP (inhibitory hyperpolarization)