CH 1.1: The cells of the Nervous System

Question 1

What are the 2 kinds of cells that the Nervous system consists of?

Answer 1

Glia & Neurons

Question 2

What is the average number of neurons in the human brain?

Answer 2

86 billion

Question 3

What are the 2 scientists who are recognized as the pioneers of Neuroscience?

Answer 3

• Santiago Ramon y cajal

- Charles Sherinngton

Question 4

What did Ramon y Cajal discover?

Answer 4

• He discovered that there is a gap between the tip of a neuron fiber and the surface of another neuron
• He used infant brains bc cells are smaller= easier to see on single slide

Question 5

What are the 5 components of a cell?

Answer 5

• Membrane
• Nucleus
• Mitochondria
• Ribosomes
• Endoplasmic Reticulum

Question 6

What is the function of a cell Membrane?

Answer 6

• It separates the inside of a cell from the environment
• It also has protein channels that allow important molecules to pass through (water, oxy, sodium, potassium, calcium, chloride)

Question 7

What is the function of a cell Nucleus?

Answer 7

-It is the structure that contains the cell’s chromosomes

Question 8

What is the function of a cell Mitochondria?

Answer 8

• It performs metabolic activities
• They also have genes separate from the ones in the nucleus that allow them to be genetically different from one another

Question 9

What is the function of cell Ribosomes?

Answer 9

• They are sites within a cell that transport newly synthesized proteins
• They can be attached to the RER or found floating around the cell

Question 10

What is the function of a cell Endoplasmic Reticulum?

Answer 10

-It is a network of thin tubes that transport newly synthesized proteins to other locations

Question 11

What are the 4 major structures of a Neuron?

Answer 11

• Soma (cell body)
• Dendrites
• Axon
• Presynaptic terminals

Question 12

How does a Motor Neuron work?

Answer 12

• It has its soma in the spinal cord

- Receives excitation through its dendrites & then conducts impulses along its axon to a muscle

Question 13

How do Sensory Neurons work?

Answer 13

• It has its soma in a little stalk off main trunk
• They are highly sensitive in one end to a type of stimulation (light, sound, touch)
• Tiny branches branch from the receptors into the axon

Question 14

What are Dendrites?

Answer 14

• They are branching fibers that get narrower towards the ends
• The surface is lined with synaptic receptors= receives info from other neurons, the greater the surface area the more info it can receive

Question 15

What are Dendritic Spines?

Answer 15

-They are short outgrowths that increase the surface area for synapses

Question 16

What is the Soma?

Answer 16

• It is the cell body of the neuron
• It contains a nucleus, ribosomes, and mitochondria
• It is also the place of metabolic werk
• It is also similar to dendrites w/ synapses covered on surface

Question 17

What is the Axon?

Answer 17

• It is a thin fiber of a constant diameter that is covered w/ Myelin Sheath w/ gaps= nodes of ranvier
• Its job is to convey impulses toward other neurons, organs or muscle
• They can be a meter long (spinal cord to feet)

Question 18

What is the Myelin Sheath?

Answer 18

-It is an insulating material made up of fats & proteins that cover the axon

Question 19

What kind of axons DO NOT have a myelin sheath?

Answer 19

-Invertebrate axons

Question 20

What is the Presynaptic Terminal?

Answer 20

• AKA end bulb/ bouton
• It is located at the end of the branches of the axon
• It is also the point where the chemicals that the axon releases cross through the junction between that neuron and another cell

Question 21

What is an Afferent Axon?

Answer 21

-It brings info into the structure

Question 22

What is an Efferent Axon?

Answer 22

-It carries info away from the structure

Question 23

What type of neurons are Afferent from the Nervous System?

Answer 23

-Sensory neurons

Question 24

What type of neurons are Efferent from the Nervous System?

Answer 24

-Motor neurons

Question 25

How do we know if a cell is an Interneuron/ Intrinsic Neuron of a structure?

Answer 25

-If their dendrites & axon are entirely contained within that structure

Question 26

What does the shape of a neuron determine?

Answer 26

-It determines its connections w/ other cells= determines its function

Question 27

Where do Glia outnumber neurons?

Answer 27

-In the cerebral cortex

Question 28

What are the 5 types of Glia cells?

Answer 28

- Astrocytes - Microglia - Oligodendrocytes - Schwann Cells - Radial glia

Question 29

What are Astrocytes?

Answer 29

- Star-shaped - They wrap around synapses of functionally related axons & shields it from chemicals circulating around - They also help synchronize closely related neurons= enables their axons to send messages in waves - IMPORTANT FOR GENERATING RHYTHM (breathing, etc) - They also dilate blood vessels to bring more nutrition into higher areas of activity & respond to hormones

Question 30

What are Microglia?

Answer 30

- They remove viruses/ fungi from the brain & increase in number to remove dead/ damaged neurons via inflamatory response - They also contribute to learning by removing weak synapses

Question 31

What are Oligodendrocytes?

Answer 31

- Located in brain & spinal cord | - They build myelin sheaths that insulate axons & supply them w/ nutrients to keep workin good

Question 32

What are Schwann Cells?

Answer 32

- Located in the periphery of the body | - They build myelin sheaths that insulate axons & supply them w/ nutrients to keep workin good

Question 33

What are Radial Glia?

Answer 33

- They guide the migration of neurons/their axons/dendrites during embryonic development - After embryonic development, they differentiate into neurons or astrocytes & oligodendrocytes

Question 34

What is the Blood-Brain Barrier?

Answer 34

- It is a mechanism that excludes chemicals from the vertebrate brain - It is lined w/ tightly packed cells that keep out viruses & harmful chemicals

Question 35

What happens when viruses cross the blood-brain barrier?

Answer 35

-It infects the brain & leads it to death bc the vertebrate brain does not replace damaged neurons

Question 36

What does the Blood-Brain Barrier depend on?

Answer 36

-Depends on endothelial cells that form capillary walls

Question 37

How is the structure of Endothelial cells inside the brain vs outside?

Answer 37

- Inside the brain, they are joined hella tight= blocks viruses, bacteria & harmful chemicals from passing through - Outside the brain they are separated by small gaps

Question 38

Why don't we have walls similar to the Blood-Brain Barrier?

Answer 38

-The barrier keeps out both harmful and useful chemicals (Glucose & amino acids)

Question 39

What process does the brain use to allow useful chemicals to pass through the Blood-Brain Barrier?

Answer 39

-Active transport!= protein mediated process that uses energy to pump chemicals from blood into brain

Question 40

What are the chemicals that need to be actively transported into the brain?

Answer 40

- Glucose (brain fuel) - Amino acids (building blocks of protein) - Purines - Choline - Few vitamins - Iron

Question 41

What is the disadvantage of the Blood-Brain Barrier?

Answer 41

-Nearly all chemotherapy drugs fail to pass through it= making treating brain cancer difficult

Question 42

What kinds of chemicals can cross the Blood-Brain Barrier passively?

Answer 42

-Small uncharged molecules & fat-soluble

Question 43

What chemicals do vertebrates rely on the most and why?

Answer 43

-They rely on glucose the most because it is the only nutrient that crosses the blood-brain barrier in large quantities

Question 44

What percentage of oxygen & glucose does the brain use

Answer 44

-It uses 20% of oxygen and 25% of its glucose

Question 45

What part of the body makes glucose?

Answer 45

- The liver! | - It makes glucose from many kinds of carbs, amino acids & glycerol (break down product from fats)

Question 46

How many Neurons are in the Cerebral Cortex & associated areas?

Answer 46

12-15 billion

Question 47

How many Neurons are in the Cerebellum?

Answer 47

70 billion

Question 48

How many Neurons are in the Spinal Cord?

Answer 48

1 billion

Question 49

What is the Node of Ranvier?

Answer 49

- They are the gaps between the myelin sheath on the axon | - Here the action potential is regenerated by a chain of positively charged ions pushed along by the segment before