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Approaches to Psychology > Lecture 5: Physiology of Nerve Transmission > Flashcards

Lecture 5: Physiology of Nerve Transmission Flashcards

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1
Q

What are Neurons?

A
  • Receives information and convey it to other neurons
  • Receives and transmits information to other cells.
  • Adult brain: 100 billion neurons.
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2
Q

What are Glia?

A
  • Cells serve many supporting functions, do not convey information over large distances.
  • Many functions, support Neurons in their functions.
  • Smaller but more numerous than neurons.
  • Many supportive functions.
  • Do not transmit information across long distances.
  • Astrocytes
  • Help synchronize the activity of neurons.
  • Remove waste material.
  • Microglia
  • Remove waste materials and microorganisms (viruses, fungi)
  • Oligodendrocytes & Schwann cells
  • Build the myelin sheaths.
  • Radial Gila
  • Guide the migration of neurons and the growth of their axons.
  • Differentiate into neurons when development is over.
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3
Q

What is Soma (cell body)?

A

*Contains nucleus, ribosomes, mitochondria.

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4
Q

What is Dendrites?

A

*Branching, fibres, receive info via synaptic receptors.

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5
Q

What is Axon?

A

*Thin fibres of constant diameter, information sender to the neuron.

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6
Q

What is Myelin Sheath?

A

*Insulates the axon. Nodes of Ranvier: interruptions of the myelin sheath.

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7
Q

What is Presynaptic terminal (end bulb, bouton)?

A

*Point at which the axon transmits information.

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8
Q

What are Afferent Axons?

A

*Brings info into a structure.

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9
Q

What are Efferent Axons?

A

*Carries info away from a structure.

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10
Q

Are sensory neurons Afferent or Efferent?

A

*Afferent to the rest of the nervous system.

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11
Q

Are Motor Neurons Afferent or Efferent?

A

*Efferent from the nervous system.

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12
Q

What protects the nervous system?

A
  • Skull (brain), backbone (spinal cord), meninges (membrane surrounding brain and spinal cord).
  • Blood brain barrier
  • prevents viruses, bacteria, and harmful chemicals from entering the brain.
  • Depends on the endothelial cells that forms the walls of the capillaries.
  • What is stopped by the barrier?
  • Most viruses, bacteria, toxins, large molecules, electrically charged molecules.
  • Some useful molecules e.g. fuels and amino acid, the building blocks of proteins.
  • What passes the barrier?
  • *Passively (no expenditure of energy).
  • Small uncharged molecules (o2m co2).
  • Water
  • Fat- soluble molecules (vitamins A and D, various drugs).
  • *Activity (expenditure of energy)
  • glucose
  • Amino Acid
  • Certain Vitamins
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13
Q

How is information transmitted in the nervous system?

A
  • Neurons conduct information via electric impulses.

* Speed

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14
Q

What is resting potential?

A
  • At rest, neurons are more negative inside than outside.
  • Voltage difference called the resting potential
  • Typical resting potential - 7 millivolts.
  • Results from an unequal distribution of negatively and positively charged particles.
  • *Negatively charged
  • Chloride ions (CI)
  • Proteins.
  • *Positively charged.
  • Sodium ions (Na)
  • Potassium ions (k)
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15
Q

What 4 interacting factors maintain resting potential?

A

1) Concentration gradients
* Ions are in random motion.
* Move form areas of high concentration to areas of low concentration.
2) Electrical Gradient
* Accumulation of changes repels like charges and attracts unlike charges.
3) Membrane permeability at rest
* Cl and K pass
* Na+ passes with difficulty.
4) Sodium - potassium pump
* Transports Na+ out and K in
* Requires energy.

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16
Q

What is action potential?

A
  • The response of a neuron to stimulation above a certain threshold.
  • Resting potential prepares the neuron to respond quickly to a stimulus with an AP.
  • Stimulation results in depolarization - the neuron becomes less negative.
  • Stimulation that results in a depolarization beyond the threshold of excitation results in a sudden, massive depolarization.
  • After the depolarization the potential returns to slightly below the RP and back to the RP value (repolarization).
  • Subthreshold stimulation produces depolarization proportional to the strength of stimulation.
  • Stimulation above threshold produces always a very similar AP.
  • All or now law: amplitude and velocity of an AP are independent of the initiating stimulus.
17
Q

What is the molecular basis of the action potential?

A
  • Na+ enters the cell.
  • K+ leaves the cell
  • Na+ K+ pump restores the original ion distribution.
  • Immediate after AP, membrane area cannot produce another AP.
  • Refractory period.
  • Absolute refractory period (1ms) - No AP can be produced.
  • Relative refractory period (2-4ms) - Stronger than usual stimulus can initiate as AP.
  • Mechanisms:
  • Na+ channels closed during the absolute refractory period, but returning to normal during the relative refractory period.
  • K+ flowing out of the cells.
18
Q

What is Neural Coding?

A

*Firing an action potential is all a neuron can do.
*1/10 system.
*How can the nervous system code for the complexity of our experience?
-Different depending on experience.
- Basic principles
~ Frequency
~ Changes in the population of neurons involved.

19
Q

What is the Propagation of the Action Potential?

A
  • Starts at the axon hillock.
  • Propagates along the axon.
  • Mechanisms
  • slight depolarisation of adjacent areas of the membrane causes area to reach its threshold.
  • AP is generated.
  • Direction of propagation determined by refractory period.
  • Speed depends on Axon diameter
  • thin: up to 1m/s
  • thick: up to 10m/s
  • myelin sheath increases speed up to 100m/s
  • crucial: nodes of ranvier.
  • Saltatory conduction: AP jumps from node to node: increases speed & saves energy.
20
Q

What is the concept of the synapse?

A
  • Late 1800s Ramon y Cajal: existence of a gap separating one neuron from another.
  • Early 1900s Charles Scott Sherrington: communication between one neuron and the next differs from communication along a single axon.
  • Speed of a reflex and delayed transmission at synapse.
  • Side at which the information flows from one neuron to another.
  • Small gap between neurons.
  • 3 main parts
  • presynaptic
  • Synaptic cleft or gap
  • Postsynaptic neuron.
21
Q

What are the events at a synapse?

A

*AP arrives at the presynaptic terminal
*Ca2+ enters, neurotransmitters attach to receptor and alter activity of the postsynaptic neuron.
*Neurotransmitters attach to receptor and alter the activity of the postsynaptic neuron.
Neurotransmitters separate from the receptors.
*Neurotransmitters are taken up by the presynaptic cell or diffuse away.

22
Q

What is the activation of postsynaptic receptors?

A
  • Neurotransmitters attach to postsynaptic receptors.
  • Key - lock system: specific receptor for specific neurotransmitters.
  • Ionotropic receptors:
  • effect fast and short.
  • Neurotransmitter open/closes channels directly.
  • Glutamate, Gaba
  • Relevant for vision, hearing (quickly changing information).
  • Metabotropic receptors
  • Effects slow and long
  • Neurotransmitters activates G - protein within the cell.
  • G - protein binds to ion channels or stimulate synthesis of second messengers.
  • Relevant for hunger, thirst, fear, anger (long term changes).
23
Q

What is the inactivation and reuptake of neurotransmitters?

A
  • Break down by enzymes
  • Detachment from receptor without break down.
  • Neurotransmitters taken up and reused by presynaptic neuron (reuptake).
24
Q

What is Temporal and Spatial summation?

A
  • Neurons conduct information through action potentials
  • Neurons communicate through synapse.
  • One synapse does not initiate an action potential
  • Post synaptic potentials are graded potentials (depolarisation below threshold, the more stimulation, the larger the change).
  • Graded depolarisation can be depolarising (excitatory) or hyperpolarizing (inhibitory).
  • The trick: action potential can be initiated by temporal or spatial summation of excitatory postsynaptic potential (EPSPs)?
25
Q

What does temporal summation effect?

A
  • summation of EPSPs from one source
  • Effects depends on:
  • size of EPSPs
  • Time between EPSP
  • Threshold of postsynaptic neuron.
26
Q

What does spatial summation effect?

A
  • Summation of several simultaneous EPSPs from separate locations.
  • Effects depends on:
  • Size of EPSPs
  • Time between EPSP (simultaneous)
  • Threshold of postsynaptic neurons.

Approaches to Psychology (21 decks)

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