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Flashcards in Nerves Deck (36):
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Transducers

Changes one form of energy into another form
Mechanical to electrical

1

Action Potential

- 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

2

Receptors

- Transforms forms of energy/stimuli into nerve impulses
- Act as a transducer

3

Saltatory Conduction

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

4

Speed of conduction of nerve impulses

- 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

5

How do action potentials carry info?

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

6

Refractory period

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

7

Local circuit

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

8

Hyperpolarisation

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

9

Repolarisation

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

10

Depolarisation

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

11

Electrochemical gradient

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

12

Voltage gated channels

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

13

Resting potential

- 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

14

Perineurium

- protective covering of a nerve

15

Structure of a nerve

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

16

Reflex arc (stages)

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

17

Reflex arc

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

18

Effector

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

19

Nodes of Ranvier

- Spaces between Schwann cells about every 1-3mm

20

Myelin/ myelin sheath

- a spiral layer of schwann cells that surround the axon
- increases the speed of conduction of nerve impulses

21

Axon

Conducts impulses away from the cell

22

Dendrites

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

23

Neurones

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

24

Organphosphorous insecticides

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

25

Botulinum toxin on the synapse

- 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

26

Nicotine on synapses

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

27

Function of synapse

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

28

Recharging synapses

- 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

29

Neuromuscular junction

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

30

Postsynaptic membrane

The membrane after the synapse

31

Presynaptic membrane

Membrane before synapse

32

Transmitter substance

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

33

Crossing a synapse

- 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

34

Synaptic cleft

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

35

Synapses

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