NERVOUS SYSTEM Session 2 Flashcards
What is the nervous system responsible for?
- It receives and processes sensory information from both external and the internal environments
What are the two major divisions of the nervous system and what do each of them consists of ?
- Central Nervous System (CNS) : consists of the brain and the spinal cord
- Peripheral Nervous System (PNS) - consists of nerves. which lie outside the CNS
What are the three main functions of the nervous system and what do each of them do?
- Sensory : The sensory receptors respond to stimuli by generating nerve signals that travel via the PNS to the CNS
- Integration : the CNS sums up the input it receives from all over the body , stores memories and creates motor response
- Motor : Generates motor output , which travels from the CNS via the PNS to muscles , glands and organs
Review the graph on slide 4 in session 1
What are the two types of cells that the Nervous Tissue contain and what are each of their functions ?
- Neurons : Transmit nerve impulses
- Neuroglia : mainly support and nourish neurons
What are some examples of the Neuroglia in both the CNS and the PNS
- CNS : Microglia , astrocytes , oligodendrorcytes , Ependymal
- PNS : Schwann cells and Satellites cells
What are the functions of the following cells ?
1. Microglia
2. Astrocytes
3. Oligodendrocytes
4. Ependymal
5. Satellite cells
6. Schwann cells
- Microglia - Phagocytic cells that remove bacteria and debris
- Astrocytes - provide metabolic and structural support directly to the neurons
- Oligodendrocytes - form myelin sheaths in CNS
- Ependymal - Lines ventricles (brain) and central canal (spine) and are involved in the production of cerebrospinal fluid in CNS
- Satellite cells - regulate nutrient and neurotransmitter levels around neurons in ganglia
- Schwann cells - form myelin sheaths in PNS
What are the three types of neurons and what do each of them do ?
- Sensory neuron : carries nerve signals from a sensory receptor to the CNS
- Interneuron : they recieve input from sensory neurons and other interneurons then communicates them with motor neuron
- Motor neurons : carries nerve impulses away from the CNS to an effector which carries out the response to the environmental change
describe the anatomy of the neuron
- Cell body : contains nucleus
- Dendrites : short extensions off the cell body that receive signals from sensory receptors or other neurons
- Axon : the portion of a neuron that conducts nerve impulses
What do myelin sheaths do and how are they formed ?
- They cover axons
- Formed when Schwann cells or oligodendrocytes wrap around an axon many times
What is a key difference between the gray and white matter?
- Gray matter is gray because it has no myelinated axons in it and white is white because it does have them
What does Myelin Sclerosis mean ?
- it is when myelins break down
How is myelin sheath important in nerve regeneration in the PNS?
- It is important because when the axon is severed , the myelin sheath remains and acts as a passageway for new fibre growth
What does resting potential mean ?
- It describes the potential energy of a neuron at rest
How do neurons maintain their resting potential ?
- They do this by the sodium potassium pump, that pumps 3 Na+ out and 2 K+ into the neuron
Describe the process of depolarization in the sodium potassium pump
- When an action potential begins, voltage dependent Na channels open and Na+ rushes into the cell, and when this happens the inside becomes more positive than the outside and it causes polarity inside to change from negative to positive
Describe the process of repolarization in the sodium potassium pump
- immediately after depolarization , Na+ channels close and K+ channels open, and K+ starts to flow out of the cell making it negative again , thus restoring the resting potential
How does the the propagation of Action Potential differ in myelinated and unmyelinated axons ?
- In unmyelinated you have to stimulate all the adjacent axons and the conduction is a lot slower
- In myelinated, the action potential occurs at the nodes of ranvier and it is called a saltatory conduction which Is a lot faster
What is the refractory period ?
- It is the period of time immediately after an action potential during which an axon is unable to conduct another action potential
What is the role of the synaptic cleft ?
- It is a small gap that separates the sending neuron from the receiving neuron
How does the removal of the Neurotransmitter work after it has initiated a response ?
- It is removed from the cleft by either an enzyme that inactivates the neurotransmitter or by the sending membranes reabsorbs the neurotransmitter.
How does excitation and inhibition differ from one another in response of the receiving neuron ?
- Excitation occurs if the neurotransmitter causes sodium gates to open
- Inhibition occurs if a neurotransmitter causes potassium ions to exit the receiving neuron
what does synaptic integration mean?
- It is when it sums up multiple incoming excitatory and inhibitory signals, it will send out a response after seeing If their is more excitation signals or inhibition signals.
