14- nervous co-ordination

Question 1

Temporal summation=

Answer 1

• ONE pre-SN releases NTs many times & rapidly

- This causes sufficient NTs so reaches threshold for AP

Question 2

Spatial summation

Answer 2

• many pre-SN share SAME post-SN

- These release sufficient NTs to reach threshold for APs

Question 3

Inhibitory NTs/ synapses= (3)

Answer 3

• When bind to post-s-m , K+ channels & Cl- channels open
• K+ diffuse out post-SN & Cl- diffuse in
• This prevents AP formation

Question 4

why is synaptic transmission UNIDIRECTIONAL? (2)

Answer 4

• NTs only made in pre-SN

- can only bind to receptors on post-S-M

Question 5

neuromuscular junction- differences (3)

Answer 5

• has lots of FOLDS, leading to cleft formation
• has more RECEPTORS
• always triggers AP

Question 6

cholinergic synaptic transmission

Answer 6

1) AP arrives, causing D, causing Ca2+ channels to open
2) Ca2+ diffuse into pre-SN causing vesciles containing acetylcholine to fuse with pre-s-m & release acetylcholine which diffuses across cleft
3) Acetylcholine binds to receptors on post-s-m
4) Na+ enter post-SN, leading to D

Question 7

cholinergic synapse vs neuromuscular junction=

Answer 7

cholinergic= Neurone>Neurone
Neuromuscular= Neurone> muscle

Question 8

Factors affecting conduction speed=(3)

Answer 8

Myelination-
-in myelinated= SC so FASTER
-in non-myelinated= WOD, so SLOWER
Axon diameter-
-Greater AD= greater SA for movement of ions across cell m
Temperature-
-Increase in temp increases kinetic energy
-Ions move across membrane quicker when have more kinetic
energy

Question 9

importance of refractory period= (3)

Answer 9

• produces DISCRETE & DISCONTINUOUS impulse (so APs dont overlap)
• Limits frequency of impulse transmission at certain intensity
• Unidirectionality ensured

Question 10

M vs Non-myelinated axon (2+2)

Answer 10

non-myelinated=

• AP passes as a wave of depolarisation
• Influx of Na+ in ONE region increases permeability of adjoining region to Na+ by causing Na+ channels to open so adjoining region depolarised

myelinated=

• Depolarisation of axon at NOR only
• Results in salatory conduction (impulse jumps from N>N)

Question 11

All or nothing response= (5)

Answer 11

1)stimulus
-when stimulated Na+ channels open
- membrane more permeable to Na+ & Na+ flood into neurone
down EC gradient
2)Depolarisation
-PD reaches threshold & an AP is formed as more Na+
channels open so more Na+ diffuse into neurone until no
more can (+30mV)
3)Repolarisation
-Na+ channels close while K+ channels open, so K+ diffuse out of
axon
4)Hyperpolarisation
-K+ channels are slow to close
-PD becomes slightly more - than RP (H) (Refractory period)
5)Return to RP
-After RP, K+ channels close & membrane returns to RP

Question 12

All or nothing response, stages=

Answer 12

1) Stimulus
2) Depolarisation
3) Repolarisation
4) Hyperpolarisation
5) Return to RP

Question 13

Establishment/ maintenance of RP (-70mV) process (4)

Answer 13

1) Na+-K+ pumps AT 3Na+ OUT of axon & 2K+ into axon
2) This creates electrochemical gradient
3) Membrane is more permeable to K+ than Na+ (due to open K+ channels & closed Na+ channels)
4) Inside cell is more - charged than out

Question 14

Structure of a myelinated motor neurone (5)=

Answer 14

Dendrities= carry nervous impulses > cell body
Axon= carries nervous impulses AWAY from cell body
Cell body= where nucleus located
schwann cells= form myelin sheath
nodes of ranvier= impulse ‘jumps’ between these in myelinated transmission