Overview of the Nervous System

Question 1

How many genes in the nervous system?

Answer 1

• 14 000 of 20 000 genes are in the nervous system

Question 2

How many genes are uniquely expressed in the nervous system?

Answer 2

• 6000

Question 3

cells in the nervous system

Answer 3

• neurons and glial cells

Question 4

Neurons

Answer 4

• specialized cells involved in (often) long-distance intercellular (between cells) communication and electrical signaling

Question 5

Nucleus

Answer 5

• organelle that houses DNA

- where gene expression occurs

Question 6

Soma

Answer 6

• also called cell body

- contains nucleus and other organelles

Question 7

Dendrites

Answer 7

• tree-like projections that receive signals from other neurons and transmit them to the soma

Question 8

Axon hillock

Answer 8

• located at the end of the soma; site where action potentials are generated

Question 9

Axon

Answer 9

• extends from the axon hillock and carries action potential away from cell body down to the axon terminal, where it will communicate with other neurons or muscle cells

Question 10

Myelin sheath

Answer 10

• discontinous sleeves of lipid-based insulation produced by oligodendrocytes (CNS) or Schwann cells (PNS) membrane
• helps increase speed of action potential

Question 11

Nodes of Ranvier

Answer 11

• uninsulated gaps in the myelin sheath along the axon

- together with myelin, it helps increase the speed of action potential down the axon

Question 12

Axon terminal

Answer 12

• also called presynaptic terminal or terminal button

- site at the end of the axon where neurotransmitters are stored

Question 13

Synapse

Answer 13

• site of information exchange between two neurons

- often form between axon and dendrites of two neighbouring neurons but can occur between axon-axon or dendrite-dendrite

Question 14

Glial cells

Answer 14

• non-neuronal cells that do no engage in electrical signalling
• function to provide metabolic and functional support for neurons in CNS and PNS

Question 15

What are the glial cells in CNS?

Answer 15

ependymal cells, oligodendrocytes, astrocytes, and microglia

Question 16

What are the glial cells in PNS?

Answer 16

satellite cells and Schwann cells

Question 17

Ependymal cells

Answer 17

• lines the ventricles of the brain and spinal cord

- creates CSF

Question 18

Oligodendrocytes

Answer 18

• lines axons in CNS, insulating them with a fatty substance called myelin

Question 19

Astrocytes

Answer 19

• star-shaped cells that mediate levels of neurotransmitters around the synapse and regulate the ion concentrations

Question 20

Microglia

Answer 20

• CNS macrophages involved in controlling local immune responses
• act primarily as scavengers that remove cellular debris from sites of injury

Question 21

Satellite cells

Answer 21

• surround somata of neurons in the PNS

- similar to astrocytes, they assist in regulating the external chemical environment

Question 22

Schwann cells

Answer 22

line axons in PNS, insulating them with myelin

Question 23

Neural circuits

Answer 23

• arrangement of neurons interconnected by synapses that work together to perform a particular function
• ex. patellar (knee-jerk) reflex

Question 24

Reflex

Answer 24

motor response to sensory input that doesn’t require consciousness

Question 25

Monosynaptic

Answer 25

direct communication between sensory neuron and motor neuron

Question 26

Central Nervous system

Answer 26

central processing centre that receives, integrates, and interprets information from periphery, and sends information back out to the periphery

Question 27

Two main functions of CNS

Answer 27

1. receiving and interpreting and relaying sensory information 2. higher-order learning known as associational systems (e.g., learning, memory, emotions)

Question 28

Peripheral nervous system

Answer 28

connects CNS to external environment and various organs

Question 29

Somatic

Answer 29

- voluntary - receives and responds to sensory input and innervates skeletal muscles - responsible for voluntary motor functions - e.g., walking

Question 30

Autonomic

Answer 30

- involuntary - also known as visceral - controls internal organs and is responsible for involuntary bodily functions - e.g., breathing, digestion - split into two types; sympathetic and parasympathetic

Question 31

Sympathetic

Answer 31

flight or fight

Question 32

Parasympathetic

Answer 32

at rest

Question 33

Genes

Answer 33

comprises of coding DNA sequences (exons) that are templates for mRNA that will ultimately be translated into a protein, and regulatory DNA sequences (promoters and introns) that control whether and in what quantities a gene is expressed given a cell type

Question 34

Gap junctions

Answer 34

allow for cytoplasmic continuity and the direct transfer of electrical and chemical signals between cells in the nervous system

Question 35

Synaptic cleft

Answer 35

site of extracellular proteins that influence the diffusion, binding and degradation of molecules including neurotransmitters