Nervous Coordination

Question 1

What are the key features of neurones?

Answer 1

-cell body
-dendrons/dendrites
-axon
-myelin sheath
-Schwann cells
-Nodes of Ranvier

Question 2

What is the direction of impulse for a motor neurone?

Answer 2

cell body to axon terminal

Question 3

What is the myelin sheath?

Answer 3

an electrical insulator, increases transmission speed
-a lipid

Question 4

What are the nodes of Ranvier?

Answer 4

gaps between adjacent Schwann cells
-no myelin sheath

Question 5

What is in the cell body?

Answer 5

-nucleus
-lots of rER
-to produce lots of proteins (especially neurotransmitters)

Question 6

What is the basic structure of a sensory neurone?

Answer 6

cell body on the side of the axon

Question 7

What are the two types of nervous system regarding motor neurones?

Answer 7

somatic (voluntary responses)
autonomic (involuntary responses)

Question 8

What are the two divisions the autonomic nervous system?

Answer 8

sympathetic - fight or flight
parasympathetic - rest or digest

Question 9

What is the resting potential?

Answer 9

-overall more negative inside the neurone than outside
-around -70mV

Question 10

How is the resting potential maintained? (names of the proteins)

Answer 10

sodium-potassium pump
potassium ion channels

Question 11

What does the sodium-potassium pump do?

Answer 11

-they use active transport
-to move three Na⁺ out
-2 K⁺ moves in
-using ATP

Question 12

What do the potassium ion channels do ?
(maintaining resting potential)

Answer 12

-allow facilitated diffusion of K⁺ out of neurone

Question 13

Describe the permeability of the neurone membrane to Na⁺ and K ⁺ ions
(resting potential)

Answer 13

permeable to K⁺ ions (through K⁺ channels- most of these are open at resting potential)
impermeable to Na⁺ ions

Question 14

What type of protein channels are the sodium channels?

Answer 14

voltage-gated

Question 15

What happens when the neurone is stimulated?

Answer 15

-sodium ion channels open
-Na⁺ moves into neurone down the electrochemical gradient
-makes the inside of the neurone less negative

Question 16

When does depolarisation occur?

Answer 16

-ONLY if the threshold potential is reached

Question 17

What happens when the threshold potential is reached?

Answer 17

-depolarisation occurs
-more Na⁺ channels open
-more Na⁺ ions diffuse in

Question 18

What happens during repolarisation?

Answer 18

-at 30mV
-Na⁺ close
-K⁺ opens
-K⁺ ions diffuse out of the neurone down gradient
-lowers the p.d

Question 19

What happens during hyperpolarisation?

Answer 19

-K⁺ channels are slow to close
-too many K⁺ ions diffuse out of the neurone
-cell becomes more negative than the resting potential

Question 20

What is the definition of refractory period?

Answer 20

the period following an action potential in which a neurone cell membrane cannot be excited

Question 21

How does an action potential travel through the axon?

Answer 21

wave of depolarisation
(propagates)

Question 22

What is the benefit of the all-or-nothing principle?

Answer 22

-stops the brain from getting over stimulated by not responding to very small stimuli

Question 23

What is the all-or-nothing principle?

Answer 23

-once the threshold potential is reached
-an action potential will always fire in the same change in voltage
-if the threshold potential is not reached , the action potential won’t fire

Question 24

What does a bigger stimulus cause?

Answer 24

it will cause action potentials to fire more frequently

Question 25

What are the three factors affecting the speed of conduction?

Answer 25

-myelination
-axon diameter
-temperature

Question 26

What is the myelin sheath?

Answer 26

-it is made up of a Schwann cell
-electrical insulator

Question 27

In a myelinated neurone, where does depolarisation occur?

Answer 27

at the nodes of Ranvier

Question 28

What is saltatory conduction?

Answer 28

-process in myelinated neurones
-action potential travels (‘jumps’) between nodes of Ranvier