Neurons and The Nervous System Flashcards
What is the resting potential of a neuron?
-70mV
What is the equilibrium potential of a neuron?
-81mV
What’s the difference between resting potential and equilibrium potential?
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
Which equations calculate EP and RP?
EP: Equilibrium equation
MP: Goldmann equation
How much more permeable is potassium than sodium?
25-30x
What does ion movement depend on?
Electrical driving force
Permeability
What needs to be in place to an action potential to occur?
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
What are the two sections of the refractory period and when do they occur?
Absolute: no further action potentials can occur (during depolarisation)
Relative: if signal is stronger than the previous action potential, another can occur (during repolarisation)
What is the type of action potential movement in an unmyelinated axon?
Contiguous
What is the type of action potential movement in a myelinated axon?
Saltatory
How is a saltatory action potential different to a contiguous action potential?
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.
Which cells myelinate axons in the CNS and PNS?
CNS: oligodendrocytes
PNS: Schwann cells
How quickly do chemical and electric synapses transfer the information?
Chemical: 2ms
Electric: 0.2ms
What are the four types of neurotransmitter? Give an example of each
Biogenic amine - dopamine, adrenaline
Amino acids - glutamate, GABA
Neuropeptides - enkephalin
Adenosine, nitrous oxide etc
What do excitatory neurotransmitters allow for and how?
Depolarisation - opens Na+ and K+ channels
What do inhibitory synapses allow for and how?
Hyperpolarisation of the postsynaptic neuron - open K+ (leaves) and Cl- (enters) channels to reduce MP
What do excitatory post synaptic potentials (EPSPs) and inhibitory post synaptic potentials (IPSPs) summate to and how can they summate?
Grand post synaptic potential (GPSP) - action potential only occurs if total is over threshold
Summate either spatially or temporally
What is the function of microglia?
Immune defence
What is the function of ependymal cells?
Line cavities of the CNS
What is the function of astrocytes?
Supportive:
Nutrient transfer
Neurotransmitter degradation
Maintenance of ion balance
Aid neurotransmitter travel across synapses
Form neural scars
Aid foetal development
Which root do afferent signals enter the spinal cord? Which root do efferent signals exit the spinal cord?
Afferent: dorsal
Efferent: ventral
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)
Neuron and interneuron cell bodies
Dorsal horn: interneuron cell bodies
Lateral horn: autonomic efferent cell bodies
Ventral horn: somatic efferent cell bodies
What is white matter made up of in the spinal cord?
Myelinated ascending and descending tracts
What are the pairs of the spinal cord?
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
What are the cranial nerves 2-7?
2: Optic
3: Oculomotor
4: Trochlear
5: Trigeminal
6: Abducens
7: Facial
List the types of receptors and state what they detect
Photo: light
Baro: pH changes
Chemo: chemical changes
Thermo: temperature changes
Mechano: mechanical changes
Noci: pain and tissue damage
How are environmental changes detected?
Via receptors - either a neuron within the tissue or a receptor cell which sends neurotransmitters to the neuron
What response do the sympathetic and parasympathetic nervous systems create? Give an example of a physiological reaction to activation of each
S: fight or flight - pupil dilation, increased heart rate and BP
PS: rest and digest - increased digestion, slowed breathing
Which ganglionic fibres are long and which are short for the parasympathetic and sympathetic nervous systems?
PS: long preganglionic, short postganglionic
S: short preganglionic, long postganglionic
Does the somatic nervous system have ganglions?
No, only one neuron from CNS to muscle
Which parts of the muscle do the following neurons innervate and what do they detect?
1a, II, alpha and gamma
1a: centre of muscle - length/speed changes (afferent)
II: ends of muscle - length changes (afferent)
Alpha: extrafusal fibres (efferent)
Gamma: intrafusal fibres (efferent fibres)
What is reciprocal innervation? What’s an example of it?
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
