Activity of Neurons Flashcards
Information conducting unit of the nervous system
Neuron
What are the functions of dendrites? (2)
- Collect information from other cells
- Increase cell’s surface area
What are Dendritic spine?
Small protrusions that cover the dendrites
Describe the axon of a neuron. (4)
- Extends out from the cell body
- Axon hillock
- Axon collateral - branches of the axon
- Teleodendria - smaller branches toward the end
What are terminal boutons? Where do they sit?
- End foot’ at the end of each teleodendrion
- Sits close to the dendritic spine of another neuron
What is a synapse?
Space between the terminal button of one neuron and dendritic spine of another
What is a Neurotransmitter?
Chemical released from terminal buttons that carries the message across the synapse
Dopamine is an _____________ neurotransmitter.
inhibitory
What encapsulate the neurotransmitters in the terminal boutons?
Vesicles
What does the nucleus of a neuron contain?
Chromosomes and genes
What is intracellular fluid of a neuron?
Fluid in which the cell’s internal structures are suspended
What is the cell membrane in neurons?
membrane surrounding the cell
Extracellular fluid, fluid outside , c__________ the cell
cushions
What is another name for intracellular fluid?
Cytoplasm (Salty Water)
True or False:
Concentration of dissolved substances in extracellular and intracellular fluid is THE SAME
False Concentration of dissolved substances in extracellular and intracellular fluid is DIFFERENT, this difference is very important for allowing a neuron to conduct electrical signal
The cell membrane is impermeable, what does impermeable mean?
Does not allow liquid to pass (hydrophobic)
How do substances like potassium and sodium cross the neuron cell membrane?
From extracellular fluid, the substances cross the membrane via embedded proteins (channels, gates or pumps)
What are the five steps of a Nerve impulse?
- Resting potential
- Action potential (Depolarization Phase)
- Repolarization
- Hyperpolarization
- Restoration of Potential
Which step describe this nerve impulse step:
Cell membrane is polarized (i.e., electrical difference between inside & outside of cell)
Intracellular fluid has a negative charge relative to the extracellular fluid
Difference in charge is about -70mV
Maintained by efflux (i.e., exit) of Na+ and influx (i.e, entry) of K+
Sodium-Potassium pump works continuously exchanging 3 Na+ for 2 K+
Since more Na+ exits than K+ enters, intracellular fluid is negatively charged
The Resting potential
Which step describe this nerve impulse step: Na+ channels close
Voltage-sensitive K+ channels open causing rapid efflux of K+
Intracellular fluid develops a more negative charge relative to the extracellular fluid
Repolarization
Which step describe this nerve impulse step: K+ efflux overshoots
Causes brief period in which charge of intracellular fluid relative to extracellular fluid is even more negative than in resting state
Hyperpolarization
Which step describe this nerve impulse step: Cell membrane receptors activated by external or internal stimuli
If -50 mV threshold reached, there is a brief but extremely large flip in the polarity of cell membrane
Voltage-sensitive Na+ channels open causing rapid influx of Na+
Intracellular fluid develops a positive charge relative to the extracellular fluid
Depolarization
Which step describe this nerve impulse step: Sodium-Potassium pump reactivated (3 Na+ out for 2 K+ in)
Cell membrane polarized (-70 mV)
Restoration of Resting Potential
What are the two types of Refractory Period?
Absolute Refractory Period
Relatively Refractory Period
What is the difference between the absolute and relatively refractory periods?
Absolute refractory period: the period of time during which no amount of external stimulus will generate an action potential. Relative refractory: period of time during which only a large stimulus will generate an action potential.
What are refractory periods?
Time period during which neuron cannot fire again unless a large amount of stimulus can make the neuron fire again
Why are refractory periods important in the nerve impulse process?
- Limits action potential frequency & prevents backward flow of signal
- Typical rate = 30 action potentials/sec
What is saltatory conduction?
the way an electrical impulse skips from node to node of Ranvier down the full length of an axon
Why did we develop myelin sheath for axons relating to skull size?
Because our skull size limits how big and how many neurons will fit, so it speeds up signal transmission
Large Axon = _____ transmission of the action potential
** size refers to diameter, not length
Quick
Axon =______
transmission of the action potential
** size refers to diameter, not length
Slow
What structure is this?
Uninsulated regions between the myelinated segments
Action potentials can only be propagated here (since myelin creates a barrier to flow of ions & therefore electrical change)
Nodes of Ranvier
Saltatory Conduction greatly ________ the rate of transmission of the action potential.
Increases
Describe what occurs when there is an action potential reaches axon terminal.
- causes a chemical to be released into synaptic gap
- A neurotransmitter is a chemical (or occasionally a gas) that is released at a synapse to transmit signals to a postsynaptic neuron (or muscle)
(2) It is
– Located inside the axon terminal
– Contain the neurotransmitter
Synaptic Vesicles and Storage Granules
Membrane on the dendritic spine
Postsynaptic Membrane
Space between the axon terminal and the dendritic
spine
Synaptic Cleft
Membrane on the axon termina
Presynaptic Membrane
What are the steps in synaptic transmission?
• Wave of depolarization to axon terminal
• Vesicles migrate presynaptic mem.
• Exocytosis
• Neurotransmitter binds to receptor
• Response is generated in
postsynaptic structure
• Type of response depends on
neurotransmitter (NT)
Neurotransmitter released into
synaptic cleft: what is this process?
Exocytosis
What is a neuromuscular junction in the PNS?
Axon to muscle synapse
True or False: A neurotransmitter typically has one
type of receptors that it can bind to
FALSE: A neurotransmitter typically has MULTIPLE
types of receptors that it can bind to
True or False: MANY neurotransmitters are associated with a single type of influence
FALSE: No one neurotransmitter is associated with
a single type of influence
What is the link between excitatory neurotransmitters and depolarization?
Excitatory neurotransmitters depolarize
the post-synaptic membrane (increasing
likelihood of AP)
What is the link between inhibitory neurotransmitters and hyperpolarization ?
Inhibitory neurotransmitters hyperpolarize the post-synaptic membrane (decreasing
likelihood of AP)
What is summation?
Process by which postsynaptic neuron “adds up” all of the excitatory & inhibitory inputs
What are the two types of summation?
Temporal and spatial summation
Explain what occurs during SPATIAL summation. Draw it
- Simultaneous stimulation by several presynaptic neurons
- Excitatory Post Synaptic Potentials (EPSPs) spread from several synapses to axon hillock
- PS neuron Fires
Explain what occurs during TEMPORAL summation. Draw it.
- High Frequency stimulation by one presynaptic neuron
- Excitatory Post Synaptic Potentials (EPSPs) spread from one synapses to axon hillock
- PS neuron Fires
What is EPSP-IPSP cancellation? Draw it
When Inhibitory input cancel out depolarization of Excitatory input through hyperpolarization.
Describe Acetylcholine NT (3)
- Muscle activation in PNS
- Sleep/wakefulness & memory in CNS
- Depletion = Alzheimer’s
disease
NT Involved in sympathetic NS:
Epinephrine `
NT Involved in arousal & attention:
Norepinephrine
NT Involved in movement & pleasure/reward and Depletion associated with Parkinson’s
disease
Dopamine
NT Involved in mood, aggression, appetite,
arousal, pain, respiration.
Serotonin (5-HT)
Describe what Major Activating Systems are? (3)
• Cell bodies gathered into nuclei in brainstem
• Axons project throughout brain and
synapse on target structures
• Each activating system is associated with different behaviors and diseases
What occurs in the axon hillock?
sums up the total signals received, both inhibitory and excitatory signals. If this sum exceeds the limiting threshold, the action potential is triggered
Explain MS. (4)
- Degenerative disease
- Attacks the myelin CNS
- Disrupts flow of signals
- Symptoms auditory, visual, somatosensory, motor & cognitive disturbances, fatigue
