Neural Homeostasis Pathways (PPT 2-3) [U2/ T1] Flashcards
What is the structure of a typical neuron?
Include:
- cell body/ soma
- dendrites
- axon
- myelin sheath
- myelinated neurons
- unmyelinated neurons
- Schwann cells
- nodes of ranvier
- axon terminals
- synapse
What is the function of the cell body/ soma?
- Where genetic material is housed
- Where dendrites connect
- Where organelles are found
What is the function of dendrites?
- To receive information
What is the function of the axon?
- Long single extension
- Often covered by myelin sheath
- Can be myelinated or unmyelinated
What is the function of the myelin sheath?
- Fatty insulator
- Speeds up messages
What is the function of Schwann cells?
- These cells make the non-continuous myelin sheath
What is the function of the nodes of ranvier?
- To increase the speed of comunication.
What is the function of the axon terminals?
- The axon terminates at multiple ends called axon terminals
What is the function of the synapse?
- Neurons don’t connect end to end.
- The messages must jump a gap called the synapse.
What are the 3 types of neurons?
- Sensory
- Relay/ Interneuron
- Motor
What is the function, structure and location of the sensory neuron?
F- Activated by sensory input & send sensoy information to the brain or spinal cord
S- Receptors at the dendritic end and transmit down one axon which is in 2 parts on either side of the soma.
L- Receptors to central neuron system
What is the function, structure and location of the interneurons/ relay neurons?
F- Coordinate and integration of responses
S- Multiple dendrites and axons
L- Located within the central nervous system
What is the function, structure and location of the motor neuron?
F- Recieve inormation from the central nervous system & send it to the effectors. (Muscle or glands)
S- Project axons outside of CNS directly or indirectly to control muscles.
L- Located in CNS & project their axons outside effectors (Muscle or glands)
What are the 3 steps of a stimulus response?
1) Receptor to control centre using the sensory neuon
2) Communication within the control centre using the interneuron/ relay neuron
3) Communication to the effector via a motor neuron
What is the action potential?
The rapid changes in electrical charge across the membrane that occur when a neuron is firing.
What are the 3 main stages action potentials occur in?
1) Depolarization
2) Repolarization
3) Refractory period
What does Depolarization include?
- Refers to a sudden change in the membrane potential, usually from a negative to positive internal charge.
- In response to stimulus or signal, sodium channels open.
- Na ions are more concentrated outside the neruon, the opening of the channels causes a passive influx of sodium into the neruon.
What does Repolarization include?
- Refers to the restoration of a membrane potential (restoring a negative internal charge)
- Following an influx of sodium, potassium channels open.
- K ions are more concentrated inside the neruon, opening of the potassium channels causes a passive movement
- The outward movement of potassium causes the membrane potential to return to a more negative internal differential.
What does the Refractory period include?
- Actively moving ions to ther orignal positions (more Na outside, more K inside).
- Involves active transport and costs energy
- A Na/ K pump is used.
- Takes both time and energy, creating a lag phase where no action potentials can be sent.
What is the sodium potassium pump?
- With the energy from ATP, sodium is pumped out of the cell while potassium is pumped back in.
- 3 sodium ions are moved out in one direction as 2 potassium ions are moved in.
- This restores the resting membrane potential.
How are messages moved down the axon?
When Na ions diffuse into the cell, some diffuse sideways making the next region of the axon depolarized.
What impacts the speed of transmission?
- Temperature
- Axon diameter
- Myelin sheath
- Voltaged-gaged ion channels are only found at the nodes of ranvier, in between is the myelin sheath. this allows the action potential to jump large distances.
What is the all or nothing principal?
- The action potential only occurs if the stimulus is large enough to cause the sodium gates to open in the membrane and allow enough sodium ions to enter the cell to change the membrane potential to a certain threshold level.
- The gates are either open or closed
What is the response of the post synaptic neuron
- The response of the post synaptic neuron depends largely on the nature of the cell, its location and the type of neuro transmitter thats being transported.
Why do neurons transmit in one direction?
- Although axons can transmit in any direction, they transmit one direction due to the refectory period.
