Nerves

Question 0

Action Potential

Answer 0

• A reversal of the resting potential
• About +40mv potential difference
• Which sweeps along the axon
• A stimuli causes some sodium channels to open and depolarise

Question 1

Transducers

Answer 1

Changes one form of energy into another form

Mechanical to electrical

Question 2

Receptors

Answer 2

• Transforms forms of energy/stimuli into nerve impulses

- Act as a transducer

Question 3

Saltatory Conduction

Answer 3

Where the action potential ‘jumps’ from one node of Ranvier to the next

Question 4

Speed of conduction of nerve impulses

Answer 4

• Wider the axon = increased speed
• Myelination = increased speed
  
  • insulates
  • bigger jumps between nodes of ranvier so cover a longer distance
• due to ions cant pass through sheath

Question 5

How do action potentials carry info?

Answer 5

• All action potentials are the same size
• nature of stimuli = position/type of receptor
• stronger stimuli = more action potentials
• stronger stimuli = stimulates more neurones

Question 6

Refractory period

Answer 6

• the time it takes to recover from an action potential
• hyperpolarisation
• stopping generating another action potential

Question 7

Local circuit

Answer 7

• the depolarised region and the resting region on either side of the action potential cause a temporary circuit

Question 8

Hyperpolarisation

Answer 8

• before returning to resting potential the membrane becomes more negative than the resting potential during the refractory period

Question 9

Repolarisation

Answer 9

• Na+ channels close when too +ve
• k+ channels open and ions leave the cell down their electrochemical gradient
• Change returns to near resting potential

Question 10

Depolarisation

Answer 10

• A stimuli causes some sodium channels in the plasma membrane to open
• Na+ ions enter the cell
• potential difference about +40mv

Question 11

Electrochemical gradient

Answer 11

• The charge and concentration on one side of the membrane is different to that on the other side
• ie depolarisation in action potential

Question 12

Voltage gated channels

Answer 12

• whether they are open or shut depends on the potential difference across the membrane

Question 13

Resting potential

Answer 13

• the potential difference normally -70mv whilst not transmitting an action potential
• actively pumps 3na+ ions out while 2k+ ions in
• can be leaky = more k+ out

Question 14

Perineurium

Answer 14

• protective covering of a nerve

Question 15

Structure of a nerve

Answer 15

• Lots of neurones bundled together with a protective perineurium
• some only sensory neurones, some only motor neurones, some a mix

Question 16

Reflex arc (stages)

Answer 16

Impulse-> sensory neurone-> dorsal root ganglion-> spinal cord-> (intermediate neurone) -> motor neurone -> axon-> effector (ie muscle contraction)

Question 17

Reflex arc

Answer 17

• A pathway from which impulses are carried from a receptor to an effector
• without conscious thought
• helps when in danger

Question 18

Effector

Answer 18

• part of the body that responds to a stimulus ie muscles/glands

Question 19

Nodes of Ranvier

Answer 19

• Spaces between Schwann cells about every 1-3mm

Question 20

Myelin/ myelin sheath

Answer 20

• a spiral layer of schwann cells that surround the axon

- increases the speed of conduction of nerve impulses

Question 21

Axon

Answer 21

Conducts impulses away from the cell

Question 22

Dendrites

Answer 22

• short cytoplasmic processes that transmit action potentials from one neurone to another

Question 23

Neurones

Answer 23

• A nerve cell

- specialised for the rapid transmission of electrical impulses called action potentials

Question 24

Organphosphorous insecticides

Answer 24

- inhibits acetylcholinesterase = continuous action potentials - in flea sprays& sheep dip for ticks - linked to illness in farmers

Question 25

Botulinum toxin on the synapse

Answer 25

- botox - can be in contaminated canned food - prevents the release of acetylcholine from the pre synpatic membrane - can be fatal - medically stop muscle contractions/spasms ie eyelids - smooths wrinkles

Question 26

Nicotine on synapses

Answer 26

- fits into acetylcholine receptors on postsynaptic membrane = action potential - not broken down quickly - large dose can be fatal

Question 27

Function of synapse

Answer 27

- transmit signals 1 way - specific pathways - some inhibitory synapses - some join lots of neurones - new synapses form linking& remembering factors

Question 28

Recharging synapses

Answer 28

- if acetylcholine constantly bonded to the membrane - Na+ channels constantly open - constant action potential - no new action potentials - acetylcholinesterase = acetate + choline - choline taken back to presynaptic knob+ acetyl coA &Atp =acetylcholine

Question 29

Neuromuscular junction

Answer 29

- is the synapse between the end of the motor neurone & a muscle - passes along muscles & causes fibres to contract

Question 30

Postsynaptic membrane

Answer 30

The membrane after the synapse

Question 31

Presynaptic membrane

Answer 31

Membrane before synapse

Question 32

Transmitter substance

Answer 32

- A chemical that is released by a presynaptic neurone - diffuses across the synaptic cleft - binds to receptors on postsynaptic membrane

Question 33

Crossing a synapse

Answer 33

- action potential arrives - calcium ion channels open ca2+ flood into cytoplasm - vesicle fuses with presynaptic membrabe leaves by exocytosis - acetylcholine diffuses across synapse& binds to receptors - na+ channels open depolarises membrane = action potential

Question 34

Synaptic cleft

Answer 34

- the small gap between 2 neurones or a neurone and effector

Question 35

Synapses

Answer 35

- the area in which a nerve impulses can be passed - neurone- neurone - neurone- effector