nerons+ seminar

what is in the skin to allow it to detect pain?

In the skin we have free nerve endings – loads of these witch are breached

those free nerev endings converge onto an axon

how does the free nerve ending create a action potental

when pressure is added to the free neurve endings pressure gated na+ chanles open letting soduim past the membbrain, making the mebrain more postive (depolirising)

Noctercepters

is a sensory neuron that responds to damaging or potentially damaging stimuli by sending "possible threat" signals to the spinal cord and the brain

what is the resting mebrain potentlal

-70mv

what is a mebrain potental

what is the relative diffrence between inside the meron and outside the membrain

sodium

postive

cloride

negative

hyperpolirising

makes mebrain potental more negative

depolirising

makes more postive

what happens after the pressure gated sodium channels are open?

sodium flows into  of the membrain meaning that the membrin potential becaimes more postive Witch then triggars the voltage gate Na+ chnales- it is senstive to the membrain potental till it reaches action potential

what haopens when they reach the action potential

the action potental spreds along the axon. the the membrane potential attains +30 mV, the voltage-gated channels specific to K⁺ ions open. As the membrane repolarizes, the sodium channels de-inactivate and return to the initial state, ready to open after receiving a stimulus. The potassium channels also close but remain open long enough to undershoot as potassium moves toward its equilibrium potential of -80 mV

How dose action potentals move up the axon?

There are spodium channales all over the axon witch will spered the mabrains potential witch will triggar more sodium chanles oping. Witch will casue more action potentials Is the axions mylinated it jumps because of the nodes of ravror

where do the axons go to?

This axon runs to the spinal cord.

To the dorsal horb in the spinal cord

the dorsal horn

Dorsal- towards back

dorsal root

is a bundle of axons coming into the dorasl part

dorsal root gangluar

cell bodies collection

where is the cell body of the axon

The cell body of the nerve witch sits on a stallk next to the axon and the axon potental dosnet go through the cell body just next to it. All the the cell body sit close together in the doral root gangular.

what dose the axon go to ?

onto the 1st order spinal neron

what happens when the axon potental gets to the presysnaps

th emebrain potental is postive witch Wicth then triggaes voltage gated calcuim chanles to open.

what dose calcium do in the presynaps

Calcuim is postive. But also a magor intercellulart signiloing molecule and when intracts with proteens it can change the shapes of those proteens

how do the vicecals go into the synaptic cleft

Clacium intracts with the proteens that are in the vesicles. The proteens that make the vesical open into th synaptic gap are controlled by calcium concentraits.

what are the nerons in the 1st order sensory neron synaps

• substace p

• glutimate

if there is a lot of pain what happens diffrently at the sensory and 1st order spin synaps

Lots of action potential both will relace but only a few just glutamate is reliced

What substace p is reliced then we feel a lot more pain.

what happens whe the nerotrasnmitters diffuse at th epost synaptic neuron

nerotransmitters bind to the to receptors that depolirises the mebrain potential ( makes more positive). The rectptors are ligand- gated na+ chanles. Wich allows sodium to go into the cell. If this happen in enough recptors/ close together. To reach the threshold for the voltage gated sodium chanles to open with will then generate an action potential.

whatr types of gates are at the postsynaptic recetpters

ligand- gated na+ chanles

where dose the Desendig angisal circuit start

Starts in the PAG(Periaqueductal gray)  is in the mid brain, gray and located near the aqueduct. has a collection of nerisn witch are respnsable for the DAC

Internerons

Short axon, in the same area, inhibitory most common one is GABA

Projection neron

long axon that comunictaes with different parts of the cns

how do inhibitory post synaps fire randomly?

In some mebrains of nerons the mebrain potential is very closte to csing a action potential witch causes the neorn to fire by random fluctuation is mebarin potentiual.

 

what neons are used in teh PAG

internurons that are inhibitory witch use GABA

what happens at the PAG to progection neron

Releces Gaba and bind to the postsytptic receptors wich cayses the projecting neron  hyperpolarise ( become negative so it less likely to fire a action potential)

how dose the post synaptic mebrian in the PAG and projection neoron

Gaba chnales are chloride chanles witch allow chloride to come into the neon and the inside becomes more negative. Membrain hyperpolirises- no chance of action potential

what happens when the ingibatiry interanl nerons in the PAG nt bind to the receptors

they stop releasing Gaba onto the projection neurons, meaning

these membranes depolarise and become closer to 0 as they aren’t inhibited

– when negativity comes small enough it opens channels that allow sodium

ions to flow in making the membrane potential positive on the inside which

starts firing AP’s

what is disihabition

lifing of the inhibition by the inhibitory interneurons that causes circuit to

become active. Inhibition is lifed due to endogenous opioids (released from

other axons from outside the PAG) inhibiting the interneurons

what is the Activation of the descending analgesia circuit is a process of

disinhibition

what starts the circte

1.        Endoougous opiods get relice

2.        Ther inhibitory so the action potential from the internal to projection synaps dsont happen

3.        So GABA isn’t realiced

4.        Meaning that the post synaps doesn’t get hyperppolirised (more neg) so the random firing of AP because the mebrain is close to 0

5.        So there is action potentials firing down the projection  

inhibitory synaps

1.        Action potential

2.        Relice of gaba

3.        Gaba binds-

4.        Becomes more negative because gaba chanles are cluride chanles so they open and let in clirine in making more neg

5.        Probirbility oif firing becomes less –

where dos ethe projection neron go to

the rafe magnus

what happens at the projection (pre) adn rafe mangus (post) synaps

glutamate binds to the receptor depolirises wicth opens the voltage gate soum chanles witch cause action potential

The rapha magnas relices

-            Serotonin

-            Neroadreninlin

Can be both excitortaty and inhibortoty

whre dodoe the rafe magnus go to

the dorsal horn- al along the spinal cord

what three synapsis dose the rapa magsnus split to

1. rafe magnus (pre) to the pre synaps of the senry neron (post)

2. internerons (inhinbitory)

3. internurons (inhibioty)

what nror transmitter is reliced by the rafe mganus

• serotonin and or adrenalin

what type of symaps is the rapha magnas to presynaptic sesonry neron?

inhibitory

what kind of synaps os the rafoah to the inter nerpons

inhibitory

what type of nero transmiteer are seritonin and neroadrenilin

excittoray and ca be inhibitory, it depends on the recepteros on the outher side of the cleftr

what type of nerotraynsmitters on on the internerons binding to the internurons

excitory witch depolirises and caysues action potentals

what are the targest of the internerons that are connected to the rafe magnus

• firts order neron

• onto the presynaptic termanal of the nocersepeter

what type of neron is the fisrt order neorn and what transmitter dose it use

• inhibory

encephilin

so What happens to the membraine of the first order nerton whne encephiln binds to it

hyperpolirises becomes more negative ,menas less likley to fire action potentals

what is pre synapting on the neoticepeter synaps with teh first orner spinal neron

• inhibiotory internueron with encehilin

• raphe magnoiut with seriotioninn wihc is inhibitory

what will the inhabiron do to the presynaptic terminal of the not9iceptor and 1st order spinal nuron

• hyperoplirises with mean that they less likelyr to shoot action potentals witch isnt able start the pain cylcle

• they need to hyperpoliris enough though because tehre rae two presynaps

what happens if the nocicepter has so much action potental that it ivverrunss teh depolirisating encephil and sseritoionin

the fisrt order neron is hyperpolirised so it wont be able tp depolirise wenough because it is alredy being deplorised by encephilin

• further reducing the likely hood of an action potental to get to the barin

Glial cells

Glial cells are a type of cell that provides physical and chemical support to neurons and maintain their environment. Located in the central nervous system and peripheral nervous system, glial cells are sometimes called the "glue" of the nervous system, as well as neuroglia or just glia.

pricniples of the nerosystem

• GLIA

• NEURONS

Neurons

Within-cell communication: electrical (e.g. Action Potentials)

Between-cell communication: chemical (neurotransmitters)

two inhibitoy and one excitoray nerons feed into a noron will it fire?

NO

one inhibitory and two exsitotay nerons feed into a neron will it fire?

YES

hormones

-            Through the bloodstream- definition of a hormone

-            Global action

-            Effects can be varied, depending on the hormone/receptor combination

Neurotransmitters

-            From one neuron to the next

-            Local action

-            Effects can be activation or inhibition, depending on the transmitter/receptor combination