524- Nervous System A Flashcards
Explain the process of stimuli through to effector organs
Stimuli are changes detected by sensory receptors inside or outside the body. These receptors make action potentials (electric signals) that gets sent along the sensory neurons to the CNS.
The sensory info is processed in the CNS. More action potentials (for instructions) gets sent through motor neurons this time to an effector (muscle or gland).
When the effector is stimulated, a response is created.
What are the 2 cell types found in the nervous tissue?
functions?
> Neurons:
create and transmit electrical and chemical signals
Glial Cells (“neuroglia”):
provide support, nutrition, insulation for neurons and help signal transmission.
(10 glial cells per neuron!)
What is a myelin sheath?
those little oval looking cells wrapped around the length of the axon. They’re filled with myelin (fatty substance) that provide insulation.
What is an axon?
single long extension that transmits signals
What is the difference between structural and functional classifications of neurons?
> Structural- how many processes (projections) extend out from the cell body.
> Functional- if the neuron is transporting nerve impulses toward, within or away from the CNS.
What are unipolar, bipolar, and multipolar neurons? (differences?)
> UNIPOLAR:
have 1 process, mostly found in sensory receptors transmitting nerve impulses towards CNS.
> BIPOLAR:
have 2 processes (axon + dendrite), these are uncommon but tend to be sensory neurons.
> MULTIPOLAR:
have 3+ processes (1 axon + 2 or more dendrites), makes up 99% of ALL neurons nd are mostly motor and interneurons.
1) What is the neurons role?
2) What are the electric signals called?
3) What is synaptic transmission?
1) to create and transmit electrical & chemical signals that allow communication between body parts!!!
2) action potentials (“nerve impulses”)
3) action potentials are sent through chemical signals and are passed onto other neurons, muscles and glands.
Why do we need to keep positive and negative charges apart? (benefit?)
to stop attraction and keep it separate through barriers (like membranes) to build potential!
1) What is voltage? (V, mV)
2) What is membrane potential?
1) it is the potential energy made when you separate opposite charges. (Usually V but in the body it is mV due to small amounts)
2) difference in charge (bigger difference=higher potential)
What is current?
equation?
the flow of electricity from 1 point to another.
Current= Voltage / Resistance
What is Resistance? (example)
whatever is getting in the way of the current.
plastic: high resistance
conductor (metal): low resistance
1) What are the charges inside and outside of a resting neuron?
2) What is a resting membrane potential?
1)> negative inside (K+ but more bigger -vely charged proteins)
>positive outside (Na+)
2) V across the neuron’s membrane (-70mV)
What is the sodium potassium pump? (what does it do?)
lots of protein along the axon that straddles the membrane of a neuron.
It creates and maintains the resting membrane potential. For every 2 K+ ions it pumps into the cell, 3 Na+ ions is pumped out. This causes a difference in charge (membrane potential) and concentration of Na+ and K+ making the outside of a neuron (ECF) more positive!)
What is the electrochemical gradient?
difference in charges =electrical and
difference in conc. of ions (Na+ and K+) =chemical
1) What must ions do to maintain the balance of charges?
2) What regulates this?
1) MUST PASS the MEMBRANE
2) ion channels (large proteins) that allow movement of ions across the membrane when their respective gates are open!
What are the 3 types of gated channels? (how do they open?)
> Voltage gated:
specific membrane potentials (Na+ channels at -55mV)
> Ligand gated
specific chemical binds to receptors on its surface
> Mechanically gated
physically stretching the membrane
1) What are action potentials?
2) What do they do?
1) electrical signals (“nerve impulses”) made and conducted by neurons!)
2) they send information through neurons from 1 part of the body through another and is done through ion movements across the axonal membrane
What is a graded potential?
This is when there’s only a few channels open and only a few ions enter the cell, creating a SMALL change in the membrane potential in a LOCALIZED part of the cell.
What are the 3 stages that happen during specific voltage changes and ion movements? (briefly describe)
⭐Depolarization:
to reduce difference in charge (V) across the membrane
>-70mV to -55mV to +30mV
⭐Repolarization:
to recreate a difference in charge across the membrane
⭐Hyperpolarization:
to increase the difference in charge across the cell’s membrane
What is Depolarisation?
How does an action potential relate to this?
> When a stimulus occurs, it causes a few sodium voltage ion channels to open, allowing Na+ to move into the neuron. This increases the charge inside the neuron and decreases V across the membrane.
> if the stimulus is strong enough to reach and breach the threshold, an action potential is created. Once it begins, it continues all the way to the end of an axon to +30mV.
What is repolarisation?
After depolarisation– as we reach +30mV, this causes the voltage gated K+ channels to OPEN, letting the K+ to flow out (electrochemical gradient) to try and rebalance the charges and the Na+ v gated channels close!
(+30mV > -70mV)
> it briefly goes below -70mV
What is hyperpolarisation?
This happens because of the voltage gated K+ ion channels being too slow to close, causing extra K+ to leak out of the neuron.
So it briefly goes below -70mV before returning to it.
How do we restore the resting membrane potential after depolarisation, repolarisation and hyperpolarisation?
Why do we need to restore it?
> Through the sodium-potassium pump moving (3) Na+ out and (2) K+ in.
> IT MUST BE RESTORED to the original distribution to be able to make more action potentials.
1) What is propagation of action potentials?
2) Explain process
1) Actions potentials need to move along the ENTIRE length of a neuron’s axon (axon hillock to axon terminal) so it can relay the info from 1 part of the body to another (synaptic transmission!)
2) in the axon hillock, once the threshold is reached, the Na+ v. gated channels open and Na+ flows in the axon making it depolarize to +30mV. Once it reaches +30mV, that section closes off its Na+ v. gated channels to prevent backflow.
Depolarization acts as a wave and moves towards the axon terminal in sections by making them reach the threshold. Again, this makes the Na+ v. gated channels open and depolarize. Synaptic transmission occurs when the action potential reaches the axon terminal.
