Nervous coordination

Question 1

How does a membrane remain at a resting potential?

Answer 1

The sodium potassium ion pump uses energy from ATP to actively transport 3 Na+ out for every 2K+ in.

Question 2

Name the features of an axon membrane

Answer 2

Voltage gated ion channels

Potassium, sodiu ion pump

Question 3

What happens to generate an action potential?

Answer 3

A stimulus arrives causing Na+ channels to open. Na+ diffuses in to the axon down the electrochemical gradient.
The membrane is now depolarised.
As sodium ion channels close potassium channels open, decreasing potential difference.

Question 4

What happens when a stimulus is big enough?

Answer 4

Na+ channels open, as Na+ diffuses in more voltage sensitive ion channels open. This is an action potential as the positive feedback causes more depolarisation.

Question 5

What happens when a stimulus is not big enough?

Answer 5

Only a few Na+ channels open. Not enough Na+ diffuses in to the axon to exceed the threshold. Called a failed stimulus.

Question 6

What happens during repolarisation?

Answer 6

Sodium ion channels open and sodium ions diffuse in . At 30mV voltage gated sodium ion channels close and potassium ion channels open. Potassium ions diffuse out causing the potential difference alters.

Question 7

Name factors effecting nervous conduction

Answer 7

Temperature
Myelin sheath
Axon diameter (bigger = less resistance)

Question 8

Discuss nerve impulse propagation

Answer 8

At the leading edge of the action potential, Na+ diffuse in. Na+ are attracted to the less negative area of the axon in front of the leading edge. This causes Na+ channels further along to open, a localised circuit is established.

Question 9

Describe synaptic transmission

Answer 9

A wave of depolarisation reaches the pre synaptic knob. Ca+ channels open and Ca+ diffuses in. Vesicles containing acetylcholine fuse to the pre synaptic membrane. Acetylcholine diffuses into the synaptic cleft and it binds to receptors on the post synaptic membrane. The receptors act as Na+ channels, Na+ diffuses through. When the threshold is exceeded an action potential is generated down the post synaptic nuerone.

Question 10

How is acetylcholine reuptook after synaptic transmission?

Answer 10

An enzyme called acetylcholinesterase hydrolyses acetyl and choline. Using energy from ATP an acetyl and choline pump reuptakes the acetyl and choline.
Some may be reuptook from the vesicle.

Question 11

What is spatial summation?

Answer 11

Adding together of action potentials from several neurones to exceed a threshold.

Question 12

What is temporal summation?

Answer 12

Adding together of action potentials over a period of time from one neurone.

Question 13

What does the neurotransmitter GABA do?

Answer 13

It binds to other receptors
Causes chloride ions to diffuse in
This causes hyper polarisation
An inhibitory response

Question 14

Name some ways drugs can affect synaptic transmission

Answer 14

Same shape as the neurotransmitter and increase amount of receptors activated (agonists).
Block the receptor so they can’t be activated and fewer receptors are (activated antagonists)
Inhibit the enzymes breaking down the neurotransmitter
Stimulate the release of neurotransmitter
Inhibit the release of a neurotransmitter

Question 15

What are the there types of muscle?

Answer 15

Skeletal (striated muscle)
Cardiac
Smooth

Question 16

What are the characteristics of slow twitch muscle?

Answer 16

Type of striated muscle 
Endurance 
Aerobic 
High quantities of mitochondria 
High quantities of myoglobin 
High affinity for oxygen at low partial pressures 
Darker in colour

Question 17

What are the characteristics of fast twitch muscle?

Answer 17

Type of striated muscle 
Explosive movements 
Short bursts 
Anaerobic 
Light colour

Question 18

Name the properties of a muscle cell

Answer 18

Elongated
The membrane is called the sarcolemma
The sarcoplasm is a specialised cytoplasm for contraction
Sarcoplasm contains units called myofibrils
(repeating units of actin and myosin)
Internal membranes called sarcoplasmic reticulum run through sarcoplasm

Question 19

Where are the following on a myofibril...
I band 
A band 
Z line 
M line 
H zone

Answer 19

I band= bands containing actin filaments
A band= myosin filaments (some overlapped by actin)
Z line= end of each sarcomere
M line= middle of myosin
H zone= only containing myosin

Question 20

Outline how muscular contraction occurs

Answer 20

An action potential arrives at the motor neurone
Acetyl choline is released
An action potential is generated through the t tubules
Causes the sarcoplasmic reticulum to release calcium ions
Trypomyosin moves of of binding sites
Myosin heads form bridges with actin
They rotate through a 45 degree angle
Actin and myosin filaments slide and the Z line shortens
ATP binds to myosin heads causing them to detach and recock
They attach further down the filament later

Question 21

What happens to calcium ions after an action potential?

Answer 21

Calcium ions move from binding sites via active transport back to the sarcoplasmic reticulum
Tropomyosin molecules move back and block the actin-myosin binding sites again
Sarcomere lengthens