CNS and neurotransmitters (AO1)

Question 1

Define “the nervous system”.

Answer 1

A system of organs and cells that is specialised for coordinating behaviour

Question 2

What are the 2 sections of the nervous system?

Answer 2

Central Nervous System (CNS) - The brain, spinal cord and neurone cells

Peripheral Nervous System (PNS) - a series of nerves that carry information between CNS and the rest of body

Question 3

What are the two sections of the peripheral nervous system?

Answer 3

Somatic nervous system - voluntary skeletal muscles

Autonomic nervous system - involuntary muscles i.e. organs

Question 4

What are the two sections of the autonomic nervous system?

Answer 4

Parasympathetic - ‘rest & digest”

Sympathetic - “fight or flight”

Question 5

What are the 3 functions of the central nervous system?

Answer 5

Detecting environmental changes and stimuli
Eg. sound and smell

Processing information to produce a response
Eg. emotional reactions to significant life events

Co-ordinating muscles to produce a response
Eg. moving away from a falling object

Question 6

What are the 6 parts of the neuron and what are their functions?

Answer 6

Dendrites - receive electrical impulses from neighboring neurons

Soma - cell body which contains most of the cell’s organelles

Nucleus - contains cell’s DNA

Axon - transfers electrical impulse signals from cell body to synapse

Myelin sheath- insulates axon to help keep electrical signals inside the cell, allowing them to move faster

Synapses - sends electrical impulses to neighboring neurons

Question 7

Define “Schwann cells” and “Node of Ranvier”.

Answer 7

Schwann cells- cells that form the myelin sheath

Node of Ranvier - a gap in the myelin sheath on the axon

Question 8

Define “saltatory conduction”.

Answer 8

Propagation of action potentials (electric impulses) along myelinated axons from one node of Ranvier to the next, increasing electrical transmission speed

Question 9

Describe the stages of neurotransmission before and including diffusion. (4 points)

Answer 9

Action potential arrives at presynaptic neurone

Calcium channels open - influx of Ca+ ions into the presynaptic neurone

Neurotransmitter-carrying vesicles move to the presynaptic membrane and fuse with the cell membrane

Exocytosis of neurotransmitter into synaptic cleft - neurotransmitter diffuses across

Question 10

Describe the stages of neurotransmission after diffusion. (4 points)

Answer 10

Neurotransmitter binds to receptors on the postsynaptic membrane

Ligand-gated ion channels on postsynaptic membrane open - influx of Na+ ions at postsynaptic membrane causes depolarisation

Action potential in postsynaptic membrane is stimulated

Neurotransmitter broken down and taken back into synaptic vesicles - occurs via receptors in presynaptic membrane

Question 11

Define “agonist” and “antagonist”.

Answer 11

Agonist - a drug that occupies receptors and activates them

Antagonist - a drug that occupies receptors but doesn’t activate them, effectively blocking them

Question 12

What is an “excitatory synapse”?

Answer 12

+ Increases the activity of post synaptic membrane
+ By depolarisation
+ Due to influx of Na+ ions
+ Causing an action potential to be fired

Question 13

What is an “inhibitory synapse”?

Answer 13

+ Decreases activity of postsynaptic membrane
+ By hyperpolarisation
+ Due to influx of Cl- ions
+ Causing no action potential to be fired