C13 - Neuronal communication

Question 1

Why is coordination needed?

Answer 1

Cells are specialised but cannot function effectively on their own

Question 2

What is homeostasis?

Answer 2

Maintenance of a stable equilibrium in the conditions inside the body

Question 3

What is cell signalling? and how does it work?

Answer 3

Cell releases a chemical that has an effect on a target cell

Can transfer signals locally using a neurotransmitter
Can transfer signals across large distances using hormones

Question 4

Do plants have a nervous system?

Answer 4

No

Question 5

How are plants coordinated

Answer 5

Plant hormones

Question 6

What is a stimulus?

Answer 6

Detectable change in external or internal environment of an organism

Question 7

What is a response?

Answer 7

Reaction to a stimulus

Question 8

What is a neurone?

Answer 8

Specialised cell which transmits impulses in the form of action potentials

Question 9

What is a specialised nerve cell

Answer 9

Neurone

Question 10

What is the structure of a neurone

Answer 10

Cell body
-contains nucleus surrounded by cytoplasm
-ER and mitochondria in cytoplasm (inv in production or neurotransmitters)

Dendrons
-short extensions from cell body
-divide into smaller branches called dendrites
-transmit electrical impulses towards body

Axons
-single elongated nerve fibres that transmit impulses away from cell body

Question 11

What are the types of neurones?

Answer 11

Sensory neurones
-transmit impulses from a sensory receptor to a relay neurone /motor neurone / brain
-have 1 dendron carrying impulse to cell body
-1 axon carrying impulse away from cell body

Relay neurones
-transmit impulses between neurones
-many short axons and dendrons

Motor neurones
-transmit impulses from relay neurone / sensory neurone to an effector (muscle/gland)
-1 long axon
-many short dendrites

Question 12

What pathway do electrical impulses follow for most nervous responses?

Answer 12

Receptor —> sensory neurone —> relay neurone —> motor neurone —> effector cell

Question 13

Diagram of neurones

Answer 13

Question 14

What are neurotransmitters

Answer 14

Chemical involved in communication across a synapse between adjacent neurones / a neurone and a muscle cell

Question 15

What is a myelin sheath

Answer 15

Membrane rich in lipid which surrounds the auxin of some neurones, speeding up impulse transmission

Question 16

What are myelinated neurones

Answer 16

Neurones where their axon is covered with myelin sheath (many layers of plasma membrane)

Question 17

What cells produce the myelin sheath? How?

Answer 17

Schwann cells
-grow around axon many times
-each time a double layer of phospholipid bilayer is laid down

Question 18

How does the myelin sheath work?

Answer 18

Acts as insulating layer
Allows neurones to conduct electrical impulse faster

Question 19

What is a node of Ranvier

Answer 19

Small gap between adjacent Schwann cell

Question 20

Difference between electrical impulse in myelinated vs non-myelinated neurone

Answer 20

Electrical impulse jumps in myelinated, making it faster

Question 21

What is a receptor?

Answer 21

Extrinsic glycoproteins that bind chemical signals, triggering a response by the cell

Question 22

What is a sensory receptor?

Answer 22

Specialised cell which detects a stimulus

Question 23

What is an effector?

Answer 23

Muscle/gland which carries out body’s response to a stimulus

Question 24

What are two features of a sensory neurone?

Answer 24

-Specific to a single type of stimulus
-Act as a transducer (convert stimulus into nerve impulse - aka generator potential)

Question 25

Types of sensory receptors

Answer 25

Question 26

What is the pacinian corpuscles

Answer 26

Sensory receptors that detect pressure
Located deep within skin (esp in soles of feet and palms)

Question 27

Structure of Pacinian corpuscle diagram

Answer 27

End of sensory neurone found within centre of corpuscle
Surrounded by layers of connective tissue
Layers separated by layer of gel

Question 28

What type of sodium channels are present in the Pacinian corpuscle

Answer 28

Stretch-mediated sodium channels
Permeability to sodium changes when channels change shape

Question 29

How does the Pacinian corpuscle convert mechanical pressure into a nerve impulse?

Answer 29

1) Resting state (at resting potential) - stretch-mediated sodium ion channels in sensory neurone membrane are too narrow for Na+ ions to pass through
2) When pressure is applied to corpuscle, changes shape, membrane stretches, sodium ions channels widen
3) Sodium ions diffuse into neurone
4) Influx of positive sodium ions depolarises membrane creating generator potential
5) Generator potential creates action potential that passes along the sensory neurone
6) Action potential transmitted along neurones to CNS

Question 30

What is resting potential?

Answer 30

Potential difference across the membrane of the axon of a neurone at rest (~ -65mV)

Question 31

What is action potential?

Answer 31

The change in the potential difference across the neurone membrane of the axon when stimulated (~ + 40mV)

Question 32

What does it mean if the membrane is polarised?

Answer 32

Outside membrane is more positively charged than inside the axon
PD across the membrane