Bio-System

Question 1

What is the role of the nervous system?

Answer 1

perceive, comprehend and respond to the world around us and inside of our body

Question 2

What are the two types of actions the nervous system causes?

Answer 2

Voluntary actions
Involuntary actions like reflexes

Question 3

What is the role of the motor neuron?

Answer 3

They play a role in voluntary and involuntary movements

Question 4

What is the role of sensory neurons?

Answer 4

React to outside inputs, allowing us to feel sensations

Question 5

What is the role of interneurons?

Answer 5

The primary function is to integrate the other types of neurons.

Question 6

What is the neuron membrane made from?

Answer 6

Phospholipid molecules in a bi-layer

Question 7

What are the properties of the head and tail of the phospholipid molecule

Answer 7

• Head - hydrophilic/ absorbs water - which faces water
• Tail - hydrophobic - which faces inwards

Question 8

What is the purpose of the bilayer?

Answer 8

It allows hydrophilic molecules like 02 and C02 to diffuse easily, while larger polar molecules cannot

Question 9

Why is it important to keep larger polar molecules inside?

Answer 9

As the ions are needed to determine the membrane potential and therefore firing.

Question 10

Role of membrane proteins in ion movement

Answer 10

Specialised ion channels and pumps in the membrane allow selective, often regulated passage of ions across the otherwise impermeable lipid bilayer.

Question 11

Resting permeability of the neuron membrane to Na⁺ vs K⁺

Answer 11

At rest, the neuron membrane is much more permeable to K⁺ than to Na⁺ because there are more K⁺ leak channels open.

Question 12

Ion distribution inside vs outside a neuron (Na⁺ and K⁺

Answer 12

Neurons have high K⁺ and low Na⁺ inside, and low K⁺ and high Na⁺ outside, creating concentration gradients across the membrane.

Question 13

Function of the Na⁺/K⁺ pump in neurons

Answer 13

The Na⁺/K⁺ ATPase pump uses ATP to move 3 Na⁺ out and 2 K⁺ into the cell, maintaining ion gradients and contributing to resting membrane potential.

Question 14

What is simple diffusion?

Answer 14

The movement from high conc to low conc

Question 15

What is facilitated diffusion?

Answer 15

The use of specific channels or carrier protiens to diffuse from high to low conc

Question 16

Does facilitated diffusion require energy?

Answer 16

NO

Question 17

What is active transport?

Answer 17

Spends cellular energy, ATP, to move substances across the membrane

Question 18

Can active transport diffuse from low to high conc?

Answer 18

YES

Question 19

Is the membrane polarised?

Answer 19

Yes

Question 20

What pd between the inside and outside of the membrane?

Answer 20

The inside is more negative by 50-100mV

Question 21

What is the resting membrane potential?

Answer 21

The difference between the inside and outside fo the membrane ~ 50-100mV

Question 22

Purpose of the Nernst equation in neurons

Answer 22

The Nernst equation calculates the equilibrium potential of a single ion across a membrane, where its electrical and chemical gradients exactly balance and there is no net ion movement.

Question 23

General form of the Nernst equation

Answer 23

Vm = RT / zF * ln|conc in / conc out|
R ~ gas constant
z ~ valence of ion interest
F ~ faraday’s constant

Question 24

Meaning of R and its value in the Nernst equation

Answer 24

gas constant and RT - thermal energy

Question 25

What is the meaning of z in the Nernst equatiin?

Answer 25

the valence (charge) of the ion (e.g. +1 for Na⁺ or K⁺, +2 for Ca²⁺, −1 for Cl⁻), affecting the size and sign of the equilibrium

Question 26

Purpose of the Goldman–Hodgkin–Katz (GHK) equation

Answer 26

The GHK equation calculates the membrane potential when several ion species (typically K⁺, Na⁺, Cl⁻) with different permeabilities all contribute simultaneously.

Question 27

General form of the GHK equation for K⁺, Na⁺, Cl⁻

Answer 27

Vm = (R * T / F) * ln( (Pk * [K+]_out + Pna * [Na+]_out + Pcl * [Cl−]_in) / (Pk * [K+]_in + Pna * [Na+]_in + Pcl * [Cl−]_out) ).

Question 28

Meaning P in the GHK equations?

Answer 28

Membrane permeability of ions

Question 29

Typical relative permeabilities at neuronal rest

Answer 29

For a typical neuron at rest, relative permeabilities are about k : Na : Cl = 1 : 0.05: 0.45 (approximate values may vary by cell type).

Question 30

What is an action potential?

Answer 30

A brief all-or-nothing spike in the membrane voltage

Question 31

Resting membrane potential state

Answer 31

At rest (~−70 mV), voltage‑gated Na+ and K+ channels are closed, K+ leak channels and the Na+/K+ pump keep the inside relatively negative.

Question 32

Threshold potential in neurons

Answer 32

The membrane voltage at which enough voltage‑gated Na+ channels open to trigger a self‑sustaining action potential; sub‑threshold depolarisations do not fire.

Question 33

Ions and channels driving depolarisation

Answer 33

During the rising phase, voltage‑gated Na+ channels open rapidly, Na+ rushes into the neuron, and the membrane potential moves toward the Na+ equilibrium potential.

Question 34

Voltage during the depolarisation peak

Answer 34

The action potential peak (overshoot) often reaches around +30 to +40 mV as Na+ permeability briefly dominates.

Question 35

What happens to Na+ channels at the peak

Answer 35

Near the peak, voltage‑gated Na+ channels inactivate (their inactivation gates close) so Na+ influx stops even though the membrane is still depolarised.

Question 36

Channels responsible for repolarisation

Answer 36

Slower voltage‑gated K+ channels open, K+ flows out of the cell, and this outward positive current drives repolarisation (falling phase) back toward resting potential.

Question 37

Hyperpolarisation (undershoot) definition

Answer 37

After the spike, K+ channels remain open long enough that the membrane potential becomes more negative than rest before returning to the resting level.

Question 38

Define depolarization vs repolarization

Answer 38

Depolarization: membrane potential becomes less negative or positive; repolarization: membrane potential returns toward its resting negative value after being depolarized.

Question 39

What is a synapse?

Answer 39

A structure that allows the neuron to pass an electrical or chemical signal to another neuron or target cell

Question 40

Chemical vs electrical synapse (basic idea)

Answer 40

Chemical synapses use neurotransmitter released into a cleft to signal the next cell; electrical synapses use gap junctions to pass ions directly and very rapidly between cells.

Question 41

Role of voltage‑gated Ca2+ channels at synapse

Answer 41

Depolarisation of the presynaptic terminal opens voltage‑gated Ca2+ channels, allowing Ca2+ to enter the terminal down its electrochemical gradient.

Question 42

How Ca2+ causes neurotransmitter release

Answer 42

The influx of Ca2+ binds to proteins on synaptic vesicles and triggers vesicle fusion with the presynaptic membrane (exocytosis), releasing neurotransmitter into the synaptic cleft

Question 43

Overall sequence of chemical synaptic transmission

Answer 43

AP arrives at presynaptic terminal, 2) depolarisation opens voltage‑gated Ca2+ channels, 3) Ca2+ influx triggers vesicle fusion and neurotransmitter release, 4) transmitter binds postsynaptic receptors and changes postsynaptic potential.

Question 44

Excitory hormones?

Answer 44

Adrenaline and Noradrenaline

Question 45

Inhibitory?

Answer 45

Serotonin