ELECTROCHEMICAL COMMUNICATION Flashcards
1
Q
what are the main type of cells in the brain?
A
- neurones > process and transmit info, vary in structure- dendrites receiving info & axons transmitting
- Glial cells > provide support - inc: astrocytes, oligodendrocytes, & microglia
2
Q
what are glial cells?
A
- perform caretaking functions
- Astrocytes: Nourish**> recovering glucose from bloodstream & passing to neurones, support, clean up other dead cells (phagocytosis)
- Oligodendrocytes: myelination> placing fatty sheaths around axon of neurones in CNS
- Microglia: phagocytosis, immune system functions
3
Q
what is the structure of a neurone?
A
- cell body: contains nucleus & carries out metabolic functions of neurone
- neural membrane: skin of neurone> bi-lipid layer (fat)= insulation & seperate outside (extracellular space) of cell from inside (intracellular fluid) = diff concentrations of charges particles
- dendrites: branchlike extensions of cell body> Carry impulses from other neurone towards cell body
- Axon: Carries impulse away from cell body down length of a neurone
- Myelin sheath: Protects axon + speeds up transmission of impulse
- Nodes of ranvier: Gaps in myelin sheath= speed up transmission > forces current to ‘jump’ across gaps
4
Q
What is neurones’ resting potential?
A
- negative potential of cell at rest in region of -60 mV
- caused by differences in concentration of charged ions inside/outside cell
- maintained by membrane insulation and restored by sodium-potassium pump
5
Q
How do cells regulate the balance of ions across their cell membrane?
A
- extracellular fluid (outside) has lots of sodium chloride (NaCl)> intracellular fluid (inside) has lots of potassium (k+)
- Opposing Forces: Diffusion & electrostatic pressure act as opposing forces= driving ions in diff directions across cell membrane
- Ion Pumps: To maintain correct ion concentrations> ion pumps e.g. sodium-potassium pump, actively transport ions against their concentration gradients.
- sodium potassium pump is necessary cos sodium is driven in by both electrostatic pressure and diffusion = maintain balance
6
Q
What is the action potential in neurones?
A
- Action potentials = electrical events in neurones, triggered by depolarisation exceeding the threshold of excitation
- Sodium channels open > allowing sodium in > As the potential rises > potassium channels open > potassium ions out = decrease in the electrical potential = repolarisation
- All-or-none
- travel by passive transmission between nodes of ranvier in myelinated axon
- electrical message that travels along axon to facilitate neural communication
7
Q
what is the ‘all or none rule”?
A
- when electrical charge reaches axon> if the threshold for excitation is reached = neurone generates full-action potential> if the threshold is not reached = no action potential
8
Q
what is passive transmission?
A
- the electrical properties of axons, such as conductance and resistance.
- axons exhibit both passive & active properties during signal transmission> w/ passive decremental conduction gradually losing strength (signal) over distance & active processes stepping in to sustain & reinforce the signal (like action potential)
- myelin sheath = reduces leakage of the electrical signal
- Passive transmission = helps conserve energy > signal doesn’t need to be continually regenerated along the full length of axon> only periodic regeneration at the nodes of Ranvier.
9
Q
why is active regeneration of action potential necessary?
A
- Active regeneration refers to the restoration of the original conditions so that the signal can continue its journey
- electrical charge is lost during passive transmission = membrane potential needs to be actively regenerated to its resting state
10
Q
How does neural integration occur?
A
- Neurones influence each other through excitatory postsynaptic potentials (EPSPs) & inhibitory postsynaptic potentials (IPSPs)
- Action potential generation depends on the combination of these potentials
- Neural integration allows nervous system to process and respond to complex info by combining signals from various sources > balance between excitatory and inhibitory inputs determines if a neuron will generate an action potential & if info will be transmitted through the neural circuit
11
Q
what is neural summation?
A
- integration of signals within a neurone at axon hillock > The likelihood of cell firing is determined by summation.
- the excitatory & Inhibitory influences are added together, if the net effect on postsynaptic neuron is inhibitory then the postsynaptic neuron is less likely to fire, if the net effect is excitatory, it is more likely to fire
- two types:
- temporal summation: where signals arrive close in time > if arrive close enough in time = add up & reach threshold for action potential initiation
- spatial summation: where signals from different synapses combine > if their cumulative effect reaches threshold= action potential triggered
12
Q
What happens in synaptic transmission?
A
- impulses arrive at presynaptic neuron, > they’re converted to chemical msgs in form of neurotransmitters> Terminal boutons release neurotransmitters into the synaptic cleft > influencing postsynaptic membrane
- Neurotransmitters diffuse across synapse & bind to receptors on post synaptic neuron> either ionotropic (directly opening ion channels) or metabotropic (indirectly influencing ion channels)
- Postsynaptic potentials depend on the neurotransmitter’s characteristics> excitatory neurotransmitters = depolarisation = more likely for postsynaptic neuron to fire action potential / inhibitory neurotransmitters = hyperpolarisation = less likely for neuron fire
13
Q
what is inactivation and reuptake?
A
- when neurotransmitter is released in to postsynaptic cleft= opens up ion channels= postsynaptic response > to prevent overstimulation & channels opened up indefinitely = dealt with inactivation & reuptake
- reuptake: terminal boutons reabsorbs neurotransmitter it released so it can be recycled after in next cycle
- inactivation: enzymatic breakdown of neurotransmitter so its no longer active > e.g. acetylcholinesterase breaks down acetylcholine, preventing continuous stimulation.
14
Q
What is the role of neurotransmitters in neuropharmacology?
A
- Neurotransmitters activate various receptors in the brain > Psychoactive drugs influence synaptic transmission by blocking or activating receptors, blocking reuptake, or increasing neurotransmitter production
> Drugs that increase activation are agonists > while those decreasing activity are antagonists.
15
Q
what are voltage gates ion channels?
A
- found in cell membranes> play role in generating & transmitting electrical signals e.g. action potentials.
- sodium gates ion channels: channels open when positive charge in membrane (depolarisation) up to threshold of excitation = sodium rushes into cell= action potential initiation
- potassium gated ion channels: normally negative but when sodium opens= potassium open up> diffusion and electrostatic pressure tells potassium to get out of cell cos of positive charge= takes potential back down> potassium pump= back resting state
16
Q
what is Active conduction?
A
- involves regeneration of an action potential along an excitable membrane> e.g. axon of a neuron
- the action potential is regenerated at specific points along the membrane > typically at the Nodes of Ranvier in myelinated axons or continuously along the unmyelinated axon
17
Q
what is passive conduction?
A
- transmission of electrical signals along the membrane through the passive spread of charge > seen in dendrites or short distances within the neuron
