5.1.3 Neuronal Communication COMPLETE

Question 1

DEFINITION- Neurone

Answer 1

Specialised cells that transmit action potentials from one pat of the body to another

Question 2

DEFINITION- Cell Body

Answer 2

Contains the cells nucleus and other organelles

Question 3

DEFINTION- Dendrites

Answer 3

Small extensions of cell body, create large SA and carry impulse towards cell body as receive them

Question 4

DEFINITION- Axon

Answer 4

Single long fibre that carries nerve impulses away from the cell body

Question 5

DEFINITION- Axon Terminal

Answer 5

Release the neurotransmitters into the synapse

Question 6

DEFINITION- Motor Neurone

Answer 6

Carries action potential from the CNS to the effector, ie. muscle or gland

Short Dendtrites, Long axon

Question 7

DEFINTION- Sensory Neurone

Answer 7

Carries an action potential from sensory receptor to the CNS

Long dendrites, Short Axon

Question 8

DEFINITION- Relay Neurone

Answer 8

Connects the sensory and motor neurone

Short axon and dendtrites

Question 9

DEFINITION- Polarised

Answer 9

Produce positive and negative charges at opposite ends

Question 10

Depolarisation

Answer 10

A reduction in the difference of electrical potential across the plasma membrane. Cell becomes more positively charged as more NA ions flood in, positive feedback. Voltage gated NA channels have opened

Question 11

Resting Potential

Answer 11

-70V, the potential difference across a membrane when its at rest, maintained by Na and K pumps. Some K channels still open

Question 12

DEFINITION- Threshold Potential

Answer 12

Critical level to which a membrane potential must depolarise to, to initiate action potentials

Question 13

DEFINITION- Action Potential

Answer 13

Change in electrical potential associated with the passage of an impulse along a membrane

Question 14

DEFINITION- Hyperpolarisation

Answer 14

K ion gates are slow to shut so too many pass through reducing membrane potential, Na/K pump restores the resting potential.

Question 15

DEFINITION- Refractory Period

Answer 15

Short period of time where no action potentials are generated

Question 16

DEFINITION- Voltage Gated Channels

Answer 16

Voltage across a membrane will open/ close the gates

Question 17

DEFINITION- Local Currents

Answer 17

Movements of ions along a neurone close to the cell surface membrane

Question 18

DEFINITION- Saltatory Conduction

Answer 18

When an action potential only jumps through the Nodes of Ranvier in myelinated neurones

Question 19

DEFINITION- Nodes of Ranvier

Answer 19

The gaps between the Schwann Cells

Question 20

DEFINITION- Myelin Sheath

Answer 20

Fatty, insulative layers of Schwann cells wrapped around the axon

Question 21

DEFINITION- Neurotransmitter

Answer 21

A chemical substance which is released at the end of a nerve fibre when a nerve impulse has arrived

Question 22

DEFINITION- Cholinergic Synapse

Answer 22

Synapses that use Acetylcholine as their neurotransmitter

Question 23

DEFINITION- Synaptic Knob

Answer 23

Where an action potential is converted into a chemical message, interacts with the recipricant neurone

Question 24

DEFINITION- Acetylcholine

Answer 24

A neurotransmitter used at the neuromuscular junction

Question 25

DEFINITION- Acetylcholinesterase

Answer 25

The enzymes that catalyses the breakdown of acetylcholine

Question 26

DEFINITION- Exocytosis

Answer 26

The release of cell contents via a vesicle through diffusion out the exterior membrane

Question 27

DEFINITION- All or nothing

Answer 27

Unless the threshold potential (-50V) is reached, no action potential will form

Question 28

DEFINITION- Summation

Answer 28

Low level stimuli can be amplified and push multiple neurones into one

Question 29

DEFINITION- Myelinated Neurone

Answer 29

Transmits action potentials faster as only travel through the Nodes of Ranvier (100m/s). Has long local currents along with saltatory conduction. Voltage gated NA channels only at the gaps.

Question 30

DEFINITION- Demyelination

Answer 30

Damage to the myelin sheath which slows/ stops impulses. Can cause neurological problems

Question 31

DEFINITION- Multiple Sclerosis

Answer 31

Progressive disease, causes damage to myelin sheath and affects the CNS

Question 32

DEFINITION- Acclimatisation

Answer 32

When the synapse runs out of vesicles due to a prolonged strong stimulus, avoids overstimulation

Question 33

Adaptions of Neurones

Answer 33

LONG- transmit over long distance NA/K PUMPS- actively transports 3Na out and 2K in using ATP GATED ION CHANNELS- control the entry and exit of ions ORGANELLES IN CELL BODY- produce the neurotransmitters MYELIN SHEATH- insulates so becomes faster

Question 34

How resting potential is maintained

Answer 34

Phospholipid bilayer is impermeable to ions channel protein pumps 3Na out and 2K in using ATP second K ion channel so moves faster rate down electrochemical gradient inside axon is more negative

Question 35

Effect of a stimulus on resting potential

Answer 35

triggers the opening of Na channel proteins, casuing a tempory reversal and Na diffuses in down the electrochemical gradient

Question 36

K Channels opening

Answer 36

At 40mV Na channels close but K channels open, both voltage gated

Question 37

Repolarisation

Answer 37

K ions diffuse out of the cell down the electrochemical gradient. Inside of the cell becomes negative again so even more K channels open

Question 38

Non Myelinated Neurones

Answer 38

Uses local currents and has a refractory period. Action potential moves across as Na gates open as the Na ions moves along the axon away from high conc.

Question 39

Factors Affecting Transmission of action potential

Answer 39

MYELIN SHEATH- increases transmission speed due to saltatory conduction, voltage gated Na channels only at nodes of ranvier. DIAMETER OF AXON- increased diameter means increased speed due to lessened leakage and resistance. TEMP- increases diffusion rate REFRACTORY PERIOD- allows recovery, prevents overlap and keeps it to one direction

Question 40

Sensory Receptors

Answer 40

- Specialised cell that detects change in our surroundings - Specific to single types of stimuli - Energy Transducers convert one form of energy into elecctrical

Question 41

The Pacinian Corpuscle

Answer 41

- Mechanoreceptor in the skin that detects mechanical stimuli - The end of the senory neurone is found in the centre of the corpuscle and is surrounded by layers of connective tissue called lamella. seperated by gel

Question 42

How Pacininian corpuscles work

Answer 42

1. When pressure is exerted they change shape 2. Membrane stretches and Na ion channels open 3. This depolarises the membrane and forms a generator potential 4. If large enough it'll initiate and action potential 5. This is then transmitted along the CNS

Question 43

Cholinergic Synapses

Answer 43

- Use Acetylcholine as a neurotransmitter - Action potentials can't cross the synpse so they release neurotrasnmitters

Question 44

Transmission across the Synpase

Answer 44

1. Action potential arrives at the synaptic knob 2. voltage gated Ca ion channels open and they diffuse into the synpatic knob 3. Causes Synaptic vesicles to move and fuse with presynaptic membrane 4. Acetylcholine released by exocytosis and they diffuse across the cleft binding to Na+ receptors on post synaptic membrane 5. Na channels open and Na+ diffuse across postsynaptic membrane into the postsynaptic neurone 6. A generator potential is created, if there is a sufficent number and it reaches the threshold potential a new action potential is created

Question 45

Acetylcholinesterase

Answer 45

Is the enzyme in the synaptic cleft that breaks down the acetylcholine on the postsynaptic membrane. Breaks down into ethanoic acid and choline

Question 46

Roles of the Synpapse

Answer 46

1. Transmit Information 2. Unidirectional 3. Act as junctions 4. Summation 5. Acclimatisation 6. Learning

Question 47

Transmit information

Answer 47

Convey impulse from one neurone to the next

Question 48

Unidirectional

Answer 48

Postsynpatic membrane has receptors, presynaptic membrane has vesicles. So only moves in one direction

Question 49

Act as junctions

Answer 49

DIVERGENCE- allows single stimulus to create many responses CONVERGENCE- Allows a number of impulses to be combined into a single one e.g. retina

Question 50

Summation

Answer 50

TEMPORAL- Low level signals can be amplified, if persistant itll cause the release of many vesicles SPATIAL- Also casued if several presynaptic neurones ech release acetylcholine into one synapse.

Question 51

Acclimatisation

Answer 51

If a stimulus is powerful and prolonged a synapse may run out of vesicles containing neurotransmitter. Said to be fatigued so no longer responds, prevents overstimulation

Question 52

Learning

Answer 52

It is believed that synapses have a role in the brain and allow the recall of events.