Neurons, glia and mechanisms of communication within the neuron Flashcards Preview

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Flashcards in Neurons, glia and mechanisms of communication within the neuron Deck (24):
1

Multiple sclerosis

An autoimmune disorder that affects the myelin covering nerve cells. Symptoms include visual impairment, problems with eye movements, numbness, slurred speech, and muscle weakness (eventually leading to paraplegia in many cases)

2

withdrawal reflex

sensory neuron senses painful stimulus, message is sent to the spinal cord where a neurotransmitter is released by the terminal buttons, an interneuron is excited and releases a neurotransmitter which in turn excites a motor neuron, the motor neuron joins a nerve travels to the muscle and causes it to contract

3

withdrawal reflex (inhibited)

sensory neuron senses painful stimulus, message is sent to the spinal cord where a neurotransmitter is released by the terminal buttons, an interneuron is excited and releases an inhibitory neurotransmitter which in turn decreases the activity of the motor neuron which blocks the withdrawal reflex

4

cell body

contains the nucleus (genetic material) and internal organelles necessary for cell maintenance

5

dentdrites

the tree like branches that allow neurons to communicate with one another. Dendrites receive information from other neurons

6

Axon

a long slender fibre that carries signals from the cell body. The signal carried by the axon is an action potential

7

terminal buttons

small knobs at the end of the dendrites that play a critical role in transmitting information from one neuron to another, by secreting a chemical called a neurotransmitter

8

cytoplasm

a jelly like substance inside the cell that contains the mitochondria (produces energy). The mitochondria produces ATP which can be used in the cell as energy.

9

nucleus

contains the cells chromosomes, which are composed of DNA. The genes that make up chromosomes create proteins that build the structure of the cell and form enzymes that create and break down molecules

10

Glial cells

provide support, assist with chemical transport to and from neurons, provide insulation, destroy and remove neurons that have died from injury or old age (phagocytosis)

11

astrocyte

provide physical support for neurons, cleaning up waste (phagocytosis) and providing nutrients to neurons, maintaining the correct composition of extracellular fluid

12

Oligodendrocytes

provide physical support to neurons, most importantly though provide the myelin sheath that surrounds the axon for neurons in the CNS

13

Microglia

the smallest glial cells. They act as phagocyctes.

14

Schwann cells

provide the myelin sheath that surrounds the axon for neurons in the PNS. When a neuron is damaged they also digest the debris and align themselves into a hollow cylinder, to act as a guide for any axonal stump that resprouts after damage. This process helps connect axons with the muscles and sense organs with which they were originally connected

15

Resting membrane potential

The inside of the neuron is slightly more negatively charged than the extra cellular space. Resting membrane potential is about -70 millivolts

16

depolarisation

bringing the resting membrane potential closer towards zero in order to trigger an action potential
+40 millivolts

17

Diffusion

when molecules distribute themselves from regions of high concentration to regions of low concentration

18

Electrostatic pressure

The force created by the combination of repulsion and attraction
Anion- negatively charged
Cation- positively charged

19

What are the four ions that are crucial to resting membrane potential?

sodium (Na+) Chloride (Cl-) Potassium (K+) Organic Anions (A-)

20

Sodium potassium pump

protein molecules in the cell membrane pump Na+ ions out of the axon to maintain a ratio of 3 Na+/2 K. Energy supplied by the mitochondria (ATP) is used in this process. Sodium- potassium transporters consume roughly 40% of a neuron's metabolic resources

21

Nodes of ranvier

unmyelinated portions of the axon which is considered an active region for action potentials

22

all or none law

Once a neuron reaches it's threshold for excitation an action potential will occur. Once triggered an action potential remains at the same amplitude

23

rate law of the action potential

the strength of an action potential is indicated by the number of action potentials triggered (the neuron's rate of firing)

24

What causes MS?

disruption of the normal process of transmission of the action potential along the axon. The usual saltatory conduction between the nodes of ranvier is disrupted due to myelin damage which prevents the signal being conveyed down the axon