Neurons and The Nervous System

Question 1

What is the resting potential of a neuron?

Answer 1

-70mV

Question 2

What is the equilibrium potential of a neuron?

Answer 2

-81mV

Question 3

What’s the difference between resting potential and equilibrium potential?

Answer 3

RP: membrane potential at resting state, with a more negative charge inside the cell
EP: membrane potential equal, with no net movement of ions across the membrane

Question 4

Which equations calculate EP and RP?

Answer 4

EP: Equilibrium equation
MP: Goldmann equation

Question 5

How much more permeable is potassium than sodium?

Answer 5

25-30x

Question 6

What does ion movement depend on?

Answer 6

Electrical driving force
Permeability

Question 7

What needs to be in place to an action potential to occur?

Answer 7

Active voltage gated K+ channel
Active voltage gated Na+ channel
Permeable ions
All three of these create the ability to move ions across the membrane rapidly

Question 8

What are the two sections of the refractory period and when do they occur?

Answer 8

Absolute: no further action potentials can occur (during depolarisation)
Relative: if signal is stronger than the previous action potential, another can occur (during repolarisation)

Question 9

What is the type of action potential movement in an unmyelinated axon?

Answer 9

Contiguous

Question 10

What is the type of action potential movement in a myelinated axon?

Answer 10

Saltatory

Question 11

How is a saltatory action potential different to a contiguous action potential?

Answer 11

In a saltatory action potential, the charge flows underneath each part of the myelin to the next node, where all the channels are located. The action potential essentially jumps to each node.

In a contiguous action potential, the charge flows continuously along the membrane, with channels evenly spread to move the action potential down the axon.

Question 12

Which cells myelinate axons in the CNS and PNS?

Answer 12

CNS: oligodendrocytes
PNS: Schwann cells

Question 13

How quickly do chemical and electric synapses transfer the information?

Answer 13

Chemical: 2ms
Electric: 0.2ms

Question 14

What are the four types of neurotransmitter? Give an example of each

Answer 14

Biogenic amine - dopamine, adrenaline
Amino acids - glutamate, GABA
Neuropeptides - enkephalin
Adenosine, nitrous oxide etc

Question 15

What do excitatory neurotransmitters allow for and how?

Answer 15

Depolarisation - opens Na+ and K+ channels

Question 16

What do inhibitory synapses allow for and how?

Answer 16

Hyperpolarisation of the postsynaptic neuron - open K+ (leaves) and Cl- (enters) channels to reduce MP

Question 17

What do excitatory post synaptic potentials (EPSPs) and inhibitory post synaptic potentials (IPSPs) summate to and how can they summate?

Answer 17

Grand post synaptic potential (GPSP) - action potential only occurs if total is over threshold
Summate either spatially or temporally

Question 18

What is the function of microglia?

Answer 18

Immune defence

Question 19

What is the function of ependymal cells?

Answer 19

Line cavities of the CNS

Question 20

What is the function of astrocytes?

Answer 20

Supportive:
Nutrient transfer
Neurotransmitter degradation
Maintenance of ion balance
Aid neurotransmitter travel across synapses
Form neural scars
Aid foetal development

Question 21

Which root do afferent signals enter the spinal cord? Which root do efferent signals exit the spinal cord?

Answer 21

Afferent: dorsal
Efferent: ventral

Question 22

What is grey matter made up of in the spinal cord? Which specific parts of the grey matter contain what? (Dorsal, lateral and ventral horns)

Answer 22

Neuron and interneuron cell bodies
Dorsal horn: interneuron cell bodies
Lateral horn: autonomic efferent cell bodies
Ventral horn: somatic efferent cell bodies

Question 23

What is white matter made up of in the spinal cord?

Answer 23

Myelinated ascending and descending tracts

Question 24

What are the pairs of the spinal cord?

Answer 24

8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal

Question 25

What are the cranial nerves 2-7?

Answer 25

2: Optic
3: Oculomotor
4: Trochlear
5: Trigeminal
6: Abducens
7: Facial

Question 26

List the types of receptors and state what they detect

Answer 26

Photo: light
Baro: pH changes
Chemo: chemical changes
Thermo: temperature changes
Mechano: mechanical changes
Noci: pain and tissue damage

Question 27

How are environmental changes detected?

Answer 27

Via receptors - either a neuron within the tissue or a receptor cell which sends neurotransmitters to the neuron

Question 28

What response do the sympathetic and parasympathetic nervous systems create? Give an example of a physiological reaction to activation of each

Answer 28

S: fight or flight - pupil dilation, increased heart rate and BP
PS: rest and digest - increased digestion, slowed breathing

Question 29

Which ganglionic fibres are long and which are short for the parasympathetic and sympathetic nervous systems?

Answer 29

PS: long preganglionic, short postganglionic
S: short preganglionic, long postganglionic

Question 30

Does the somatic nervous system have ganglions?

Answer 30

No, only one neuron from CNS to muscle

Question 31

Which parts of the muscle do the following neurons innervate and what do they detect?
1a, II, alpha and gamma

Answer 31

1a: centre of muscle - length/speed changes (afferent)
II: ends of muscle - length changes (afferent)
Alpha: extrafusal fibres (efferent)
Gamma: intrafusal fibres (efferent fibres)

Question 32

What is reciprocal innervation? What’s an example of it?

Answer 32

A secondary efferent signal is sent to the opposing muscle, to make sure that it performs the opposing action - can also be sent to same muscle in other limbs to maintain posture/balance
e.g. patellar tendon reflex