Nervous system overview

Question 1

How many neurons do humans have on average?

Answer 1

On average the human brain has 86 billion neurons

- 160,000 km end-to-end

Question 2

What are dendrites?

Answer 2

Branch-like structures that receive information from other neurons

Question 3

What is the purpose of a soma or cell body? What is the structure?

Answer 3

It protects the nucleus and cell contents. The phospholipid bilayer maintains the negative charge within the cell.

Question 4

What is the nucleus?

Answer 4

Contains the genetic material, produces neurotransmitters

Question 5

What is the axon hillock?

Answer 5

It is the gatekeeper of transmission of signal (action potential). Graded potentials are summed to determine if an action potential will be fired.

Question 6

What is an axon?

Answer 6

It is a long nerve fibre which conducts the electrical signals from the cell body.

Question 7

What is the myelin sheath?

Answer 7

It is a coating that insulates the axon to increase the speed of signalling. IT is produced by Schwann cells.

Question 8

What are nodes of ranvier?

Answer 8

They are gaps in the myelin sheath, bare axon. They allow for signal to travel down the axon. Without them, signal may be lost.

Question 9

What is Multiple Sclerosis?

Answer 9

It is an autoimmune disease leading to failure of cells responsible for myelination (Schwann cells). Overtime this leads to the degradation of myelin sheath, reducing the speed of transmission.

Question 10

What are some symptoms of MS?

Answer 10

Musculoskeletal symptoms - weakness, spasms, ataxia
Cognitive impairments, depression, unstable mood
Damage to the brain affects cognition, behaviour, etc.

Question 11

What are some types of neurons?

Answer 11

Multipolar, bipolar, and unipolar neurons.

Question 12

What are multipolar neurons like in terms of anatomy?

Answer 12

Multiple dendritic branches
Somatic membrane gives rise to one axon, but to trunks of many dentritic trees
Can have co-lateral axon branches

Question 13

Where are multipolar neurons most found?

Answer 13

Multipolar neurons are the most common type found within CNS.

Question 14

What are axon terminals/ terminal buttons?

Answer 14

Presynaptic, sent from these to the next neuron.

Question 15

What are sensory neurons?

Answer 15

Neurons activated by sensory input.

e.g. photoreceptors, mechanoreceptors, sterocilia

Question 16

Afferent signal

Answer 16

From periphery to brain

Question 17

Efferent signal

Answer 17

From brain to periphery

Question 18

What kind of neuron is the Purkinje cell of the

cerebellum?

Answer 18

Multipolar neuron

Question 19

What do sensory neurons tend to be?

Answer 19

Unipolar or bipolar. They all send information to the brain from the periphery (afferent signal).

Question 20

What do motor neurons tend to be?

Answer 20

Multipolar. They all send information from the brain to the periphery (efferent signals).

Question 21

Where are motor neurons located?

Answer 21

Cell body located in the spinal cord
Axon projects to the periphery to control
muscles

Question 22

Where are interneurons found?

Answer 22

Within the brain. They are involved in higher order processing e.g. memory and cognition