Neurons, glia and mechanisms of communication within the neuron

Question 1

Multiple sclerosis

Answer 1

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)

Question 2

withdrawal reflex

Answer 2

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

Question 3

withdrawal reflex (inhibited)

Answer 3

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

Question 4

cell body

Answer 4

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

Question 5

dentdrites

Answer 5

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

Question 6

Axon

Answer 6

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

Question 7

terminal buttons

Answer 7

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

Question 8

cytoplasm

Answer 8

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.

Question 9

nucleus

Answer 9

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

Question 10

Glial cells

Answer 10

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)

Question 11

astrocyte

Answer 11

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

Question 12

Oligodendrocytes

Answer 12

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

Question 13

Microglia

Answer 13

the smallest glial cells. They act as phagocyctes.

Question 14

Schwann cells

Answer 14

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

Question 15

Resting membrane potential

Answer 15

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

Question 16

depolarisation

Answer 16

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

Question 17

Diffusion

Answer 17

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

Question 18

Electrostatic pressure

Answer 18

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

Question 19

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

Answer 19

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

Question 20

Sodium potassium pump

Answer 20

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

Question 21

Nodes of ranvier

Answer 21

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

Question 22

all or none law

Answer 22

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

Question 23

rate law of the action potential

Answer 23

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

Question 24

What causes MS?

Answer 24

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