Fundamentals of the nervous system and nervous tissue (1)

Question 1

Two benefits of cells communicating via electrical and chemical signals?

Answer 1

1.Rapid and specific
2.Usually cause almost immediate responses.

Question 2

What are the three overlapping functions of the nervous system?

Answer 2

1.Sensory input
2.Integration
3.Motor output

Question 3

What is the sensory function of the nervous system?

Answer 3

-Information gathered by sensory receptors about internal and external changes

Question 4

What is the integration function of the nervous system?

Answer 4

-Processing and interpretation of sensory input

Question 5

What is the motor output function of the nervous system?

Answer 5

-Activation of effector organs (muscles and glands) produces a response

Question 6

What are the 2 principle parts of the nervous system?

Answer 6

1.Central nervous system (CNS)
2.Peripheral nervous system (PNS)

Question 7

What is the central nervous system? (2 parts)

Answer 7

1.Brain and spinal cord of dorsal body cavity
2.Integration and control center (interprets sensory input and dictates motor output)

Question 8

What is the peripheral nervous system? (2 parts)

Answer 8

1.The portion of nervous system outside CNS
2.Consists mainly of nerves that extend from brain and spinal cord (Spinal nerves to and from spinal cord, Cranial nerves to and from brain)

Question 9

Nervous tissue consists of which two principle cell types?

Answer 9

1. Neuroglia (gial cells)= small cells that surround and wrap delicate neurons
2. Neurons (nerve cells)= excitable cells that transmit electrical signals

Question 10

What are the 4 main neuroglia support CNS neurons?

Answer 10

1. Astrocytes
2. Microglial cells
3. Ependymal cells
4. Oligodendrocytes

Question 11

Points about astrocytes

Answer 11

1.Cling to neurons, synaptic endings and capillaries
2.Most abundant, versatile and highly branched glial cells

Question 12

Some functions of astrocytes

Answer 12

-Support and brace neurons
-Guide migration of young neurons
-Participate in information processing in the brain
-Control the chemical environment around neurons
-Play role in exchanges between capillaries and neurons
Respond to nerve impulses and neurotransmitters
-Influence neuronal functioning

Question 13

Points about microglial cells (include functions)

Answer 13

1. Small ovoid cells with thorny processes that touch and monitor neurons
   2.Migrate toward injured neurons
   3.Can transform to phagocytize microorganisms and neuronal debris

Question 14

Points about ependymal cells (and functions)

Answer 14

1.Are ciliated (Cilia beat to circulate cerebrospinal fluid -CSF)
2.Produce Cerebrospinal fluid to line the central cavitiees of the brain and spinal column.

Question 15

Oligodendrocyte points and functions

Answer 15

1. Branched cells
   2.Processed wrap CNS nerve fibers, forming insulating myelin sheaths in thicker nerve fibers.

Question 16

What are the two major neuroglia seen in the PNS?

Answer 16

1.Satellite cells
2.Schwann cells

Question 17

Function and location of satellite cells

Answer 17

1.Function similar to astrocytes (in CNS)
2.Surround neuron cell bodies in PNS

Question 18

Function and location of Schwann cells.

Answer 18

1.(Function similar to oligondendrocytes)- vital to regeneration of damaged peripheral nerve fibers
2.Surround all peripheral nerve fibers and form myelin sheaths in thicker nerve fibers.

Question 19

What are neurons and their structure (function)

Answer 19

1. Neurons (nerve cells) are structural units of nervous systems
2. Large, highly specialised cells that conduct impulses

Question 20

Special characteristics of neurons (3)

Answer 20

1. Extreme longevity (they last a person’s lifetime)
2. High metabolic rate: requires continuous supply of oxygen and glucose
3. All have cell body and one or more processes.

Question 21

What is the neuron cell body? (also known as soma) and function of its plasma membrane?

Answer 21

-Biosynthetic center of neuron
-(in most) The plasma membrane is part of the receptive region that receives input information from other neurons.

Question 22

Name for clusters of neuron cell bodies in the CNS?

Answer 22

-Nuclei

Question 23

Name for clusters of neuron cell bodies in the PNS

Answer 23

-Ganglia

Question 24

Arm like processed that extend from cell body (CNS and PNS)

Answer 24

-CNS contains both neuron cell bodies and their processed
-PNS contains mostly neuron processes.

Question 25

What are tracts

Answer 25

*Bundles of neuron processes in CNS

Question 26

What are nerves

Answer 26

*Bundles of neuron processes in PNS

Question 27

What are the two types of processes?

Answer 27

1.Dendrites 2.Axon

Question 28

Describe the basic structure of a motor neuron (9)

Answer 28

1. Dendrites (receptive regions) 2. Cell body (biosynthetic centre and receptive region) 3.Nucleus & Nucleolus 4. Chromatophilic substance (rough endoplasmic reticulum) 5.Axon (impulse-generating and conducting region) 6. Schwann cell 7. Myelin sheath gap (node of Ranvier) 8.Axon terminals (secretory region) 9.Terminal branches

Question 29

How are organelles and molecules moved along axons?

Answer 29

Moved by motor proteins and cytoskeletal elements

Question 30

Definition of anterograde

Answer 30

*Away from the cell body -e.g. membrane components, enzymes, neurotransmitters, cytoskeletal elements.

Question 31

Definition of retrograde

Answer 31

*Towards the cell body -e.g. signal molecules, viruses, bacterial toxins, organelles to be degraded

Question 32

Composition of myelin sheath

Answer 32

- Myelin, a whitish, protein-lipid substance

Question 33

Function of myelin (2)

Answer 33

1. Protect and electrically insulate axon 2.Increase speed of nerve impulse transmission

Question 34

What are myelinated fibers?

Answer 34

*Segmented sheath suurrounds most long/large-diameter axons

Question 35

What non-myelinated fibers?

Answer 35

*Do not contain sheath (conduct impulses more slowly)

Question 36

What are the steps for the myelination of a nerve fiber (axon)

Answer 36

1. Schwann cell envelopes axon 2. The schwann cell rotates along the axon, wrapping its plasma membrane loosely around it in successive layers 3.The schwann cell cytoplasm is forced from between the membrane, the tight membrane wrappings surrounding the axon form the myelin sheath.

Question 37

How are myelin sheaths presented in the CNS and how many axons can one cell wrap?

Answer 37

-Formed by processes of oligodendrocytes (not whole cells) -Each cell can wrap 60 axons at once

Question 38

What is white matter?

Answer 38

*Regions of the brain and spinal cord with dense collections of myelinated fibers (usually fiber tracts)

Question 39

What is grey matter?

Answer 39

*Mostly neuron cell bodies, dendrites, axon terminals and non--myelinated fibers (areas where synapses occur between neurons- where integration and command initiation takes place)

Question 40

What are the three types of neurons related to the CNS?

Answer 40

1.Sensory 2.Motor 3.Interneurons

Question 41

Function of sensory neurons and where they are found.

Answer 41

1. Transmit impulses from sensory receptors toward CNS 2.Cell bodies are located in ganglia in PNS

Question 42

Function of Motor neurons and where they are found.

Answer 42

1. Carry impulses from CNS to effectors 2. Most cell bodies are located in CNS (except some autonomic neurons)

Question 43

Function of interneurons, where they are found, percentage of them in the body

Answer 43

1. Shuttle signals through CNS pathways 2.Lie between motor and sensory neurons, most are entirely in CNS 3. 99%

Question 44

What does generating a resting membrane potential depend on? (2)

Answer 44

1. Differences in K+ (higher inside) and Na+ (higher outside) conc inside and outside cells 2. Differences in permeability of the plasma membrane to these ions

Question 45

What is the transmembrane potential of a neuron usually around?

Answer 45

-70mV

Question 46

Notes about the charge in the cytosol and extracellular fluid

Answer 46

1. Cytosol contains an abundance of negatively charged proteins 2.Extrecellular fluid contains relatively few -Therefore these proteins cannot cross the plasma membrane.

Question 47

How can potassium ions diffuse out of the cell?

Answer 47

Via potassium leak channels

Question 48

How does the sodium-potassium pump maintain a stable resting potential?

Answer 48

1. It ejects 3Na+ for every 2K+ taken in from the extracellular fluid

Question 49

How can sodium ions diffuse into the cell?

Answer 49

Sodium leak channels