Lecture 1 and 2- Nervous System Components

Question 1

How many genes are expressed in the brain?

Answer 1

~14, 000 genes (6,000 gene expressed ONLY in brain and no where else)

Question 2

How do glia cells differ from neurons? (7 points)

Answer 2

• replaced by precursors in adulthood
• do not generate electrical activity
• modulate synaptic functions
• essential for brain metabolism
• maintain mature chemical homeostasis
• regulate blow flow through capillaries
• provide immune type functions

Question 3

What are ependymal cells?

Answer 3

Endothelial cells that line ventricles

• derive from radial glia (present during development)
• some produce cerebral spinal fluid
• others serve as stem cells or progenitor cells to make more glia and perhaps even neurons

Question 4

What are tanycytes?

Answer 4

Ependymal cells that line 3rd ventricle and extend into hypothalamus

• involved with transferring signals from CSF to CNS (glucose levels)
• likely to originate embryonically from radial glial

Question 5

What are the myelinating glial cells on the PNS?

Answer 5

Schwann cells

Question 6

What are the mylinating neurons of the CNS?

Answer 6

Oligodendrocytes

Question 7

What are micro glia also called?

• function?
• derived from what cells?

Answer 7

PHAGOCYTOTIC CELLS

• main elements of intrinsic immune system
• sense brain injury and clear cellular debris
• deprived from hemopoetic stem cells in bone marrow

Question 8

10 normal functions of astrocytes?

Answer 8

1) sequestration and/or redistribution of K+ during neural activity
2) removal of glutamate and GABA at synapses
3) synthesis of precursors for glutamate and GABA production
4) providing energy substrate to neurons (eg. Lactate)
5) sharing energy substrate derived from glycogen with neurons
6) brain water homeostasis
7) influencing integrity of blood brain barrier
8) regulate extra cellular pH
9) modulation of excitatory and inhibitory synapses
10) vascular dynamics

Question 9

3 pathological functions of astrocytes?

Answer 9

1) cytotoxic brain edema
2) glioma formation
3) modulation of stroke outcome

Question 10

Mechanism used by astrocytes to regulate blood flow to active brain regions

Answer 10

Constricting and relaxing of arteriole through changes in Ca2+ in astrocytes

Question 11

How close are neurons to capillaries in the mammalian brain?

Answer 11

Within 10-20 micrometers

Question 12

Other name for cell body of neurons

Size of cell body in

1) vertebrates
2) invertebrates

Answer 12

Soma (lots of mitochondria and endoplasmic reticulum)

Size in vertebrates:
Small- 8um
Large- 50um
Largest- 200um (mauthner cell in fish brain stem)

Size in invertebrates:
Small- 8um
Giant- >600um (R2 neurons in aplysia)

Question 13

5 things to know about dendrites

Answer 13

1) primary sites of input from other neurons (#of inputs determine size and complexity of dendritic “arbor”)
2) can release neurotransmitter in some neurons
3) contain ribosomes (can make proteins locally)
4) vary in diameter (thicker proximal, thinner distally)
5) contain lots of actin

Question 14

6 things to know about Axons

Answer 14

1) arise from cell body (vertebrate neurons)
2) specialised for relaying electrical signals
3) vary in length (10um to many cm)
4) contain microtubules and microtuble binding proteins
5) relatively constant diameter in any neuron
6) have specialised area that release neurotransmitters , terminal or en passent

Question 15

Axons and dendrites serve the primary functions of neurons to _______, _________, _________, and __________ electrochemical signals that encode information

Answer 15

Generate, send, receive, and integrate (process)

Question 16

Neurons communicate with each other via _________

Answer 16

Synapses

Question 17

What are “directed” synapses

What are the 4 types

Answer 17

Neurotransmitter released onto receptors 15nm away across a synaptic cleft

4 types:
Axo -dendritic 
Axo- somatic 
Axo- axonic 
Dendro- dendritic

Question 18

What are “non-directed” synapses

Answer 18

Transmitter released onto receptors 1um to mm’s away

Aka hormonal/neuromodulatory

Question 19

2 functions of dendritic spines

Answer 19

1) spine compartmentalises biochemical process (calcium influx)
2) can amplify local voltage changes if voltage dependent channels are in spine head

Question 20

Circuit elements (5)

Answer 20

Monosynaptic

Disynaptic

Polysynaptic

Feedforward

Feedback

Question 21

Convergence…..

Answer 21

Defines by the number of inputs to a single neuron

Eg. Purkinje cell up to 100, 000

Question 22

Divergence….

Answer 22

Number of targets innervated by one neuron