NEURONAL COMMUNICATION

Question 1

State the basic plan of a nervous system

Answer 1

Change in enviro of receptor stimulus 
Receptor generates nerve impulses 
Sensory neurone 
Relay neurones in CNS
Motor neurone 
Effector (muscle of GLAND)
Response

Question 2

What is a neurone

Answer 2

Specialised cells that transmit an ACTION POTENTIAL from one part of the body to another

• protect body
• maintain homeostasis

Question 3

What are dendrites

Answer 3

Small extensions on cell body, creating larger SA carrying impulses towards cell body
-one= dendron

Question 4

What is the axon

Answer 4

Single long fibre carries impulse AWAY from cell body

Question 5

Function of axon terminals

Answer 5

Large SA

Lots of connections

Question 6

What does the cell body contain

Answer 6

Nucleus and other organelles

Question 7

Benefits of having long neurones

Answer 7

Transmit action potential over long distance

Question 8

Benefits of sodium potassium pumps

Answer 8

Actively transport sodium out of the cell and potassium into the cell (ATP)
3 sodium out, 2 potassium in

Question 9

Benefits of gated ion channels

Answer 9

Controls entry/exit of sodium/potassium/calcium ions

Ions= polar= repelled by bilayer

Question 10

Benefits of organelles in the cell body

Answer 10

Mitochondria, nucleus, ribosomes, ER, Golgi- for production of neurotransmitters

Question 11

Benefits of the myelin sheath

Answer 11

Fatty sheath insulates neurone from other electrical activity
20-30 layers of schwa cell membrane

Question 12

Describe the myelin sheath

Answer 12

Wrap themselves around the axon
Made of myelin (lipid)
1/3 of cells are myelinated (speeds up conduction, 1ms-100ms)

Question 13

What are gaps between schwa cells called

Answer 13

Nodes of Ranvier

2-3 um wide

Question 14

Function of sensory neurone

Answer 14

Carry an action potential from sensory receptor to CNS

Question 15

Function of motor neurone

Answer 15

Carry action potential from CNS to an effector (e.g. muscle or gland)

Question 16

Function of relay neurone

Answer 16

Connect sensory and motor neurone

Question 17

Sensory neurone:
Position of cell body
Length of dendrites
Length of axon

Answer 17

Outside CNS
Long, dendrites end axon
Short- outside CNS- inside CNS (spinal cord)

Question 18

Motor neurone:
Position of cell body
Length of dendrites
Length of axon

Answer 18

Inside CNS
Many short dendrites
Long (outside CNS- effector)

Question 19

Relay neurone:
Position of cell body
Length of dendrites
Length of axon

Answer 19

Within CNS
Short
Short

Question 20

What is a nerve impulse

Answer 20

Temporary reversal of the electrical potential difference across the neurone membrane

Question 21

What is the resting potential

Answer 21

Potential difference across the neurone cell membrane while membrane is at rest
Polarised membrane approx -70mV

Question 22

How is the resting potential maintained

Answer 22

Phospholipid bilayer impermeable to ions
Sodium-potassium pump actively transports (ATP) 3NA+ out, 2K+ in
Potassium can diffuse back through open channel proteins
Sodium channels are closed, diffusion of potassium is passive- down a concentration gradient
Cytoplasm contains negatively charged ions (e.g. protein molecules)
Interior of neurone= negative

Question 23

Function of channel proteins

Answer 23

Voltage gated- whether open or closed depends on voltage across membrane, changes of ion concentration changes protein shape
Stimulus sensitive- increase pressure, increase NA+ channels open

Question 24

What is the action potential

Answer 24

Brief reversal of the potential across the membrane of a neurone causing a peak of +40mV compared to resting potential -70mV

Question 25

Explain the concept of all or nothing

Answer 25

Below threshold value, no impulse generated
Above threshold, impulse generated
AP is the same size
Larger stimulus= more frequent the impulses

Question 26

What is the refractory period

Answer 26

Follows AP, short period of time where another AP is impossible
V-gated Na+ channels are closed
Keeps AP going in one direction
Separates AP