2. Physio

Question 1

Resting membrane potential is determined by

Answer 1

distribution of K+, Na+, Cl-

Question 2

where is AP generated

Answer 2

AP will only be generated if depolarisation reach threshold membrane potential at trigger point/ axon hillock

Question 3

Describe rising phase in AP cycle

Answer 3

As neuron depolarises, voltage gated Na+ channels are opened.
Rapid entry of Na+ into the cell through voltage-gated Na channels depolarises the cell

Question 4

Describe overshoot phase of AP cycle

Answer 4

• at one point, the inside of the cell become more positive than outside → reverse membrane potential polarity → drop in voltage
• at peak: no influx of Na+ and efflux of K+ through voltage gated channels

Question 5

Describe falling phase of AP cycle

Answer 5

• Inactivated voltage-gated Na channels
• Open voltage-gated K channels (K more concentrated inside cell)
• K+ moves out of cell → membrane rapidly repolarises

Question 6

2 events that occur at Neuromuscular Junction

Answer 6

Receptive step and Translating/transmitting step

Question 7

Receptive step

Answer 7

• arrival of AP at presynaptic cell/ axon terminal → depolarisation of presynaptic neuron → opening of voltage-gated Ca channels → influx of Ca →
• fusion of synaptic vesicle with presynaptic membrane → release of NT into synaptic cleft

Question 8

Translating/transmitting step

Answer 8

binding of NT (eg acetylcholine) to postsynaptic ligand gated receptor (eg nicotinic receptor) → influx of Na into postsynaptic membrane

Question 9

how does hypokalemia affect signalling

Answer 9

causes hyperpolarisation → impairs ability to generate AP at NMJ → skeletal muscle membrane becomes less excitable → muscle cannot contract → weakness and paralysis of skeletal muscles

Question 10

how does hyperkalemia affect signalling

Answer 10

reduce efflux of K+ from inside to outside of the cell

Question 11

sensory transduction

Answer 11

Transformation of an external stimulus to AP

Question 12

describe the sensory transduction pathway

Answer 12

1. Depolarisation of sensory receptor
2. Generation of action potential
   
   • depolarisation at trigger point generate AP
   • Depolarisation from the receptor travels to the axon hillock/ tigger zone → generates AP
3. Propagation to CNS
4. Synaptic transmission
5. Excitation of neuron in spinal cord/ CNS

Question 13

types of sensory receptors and their stimuli

Answer 13

• mechanoreceptor - mechanical energy (non-noxious)
• nociceptor/free nerve ending - noxious stimuli
• chemoreceptor - chemicals
• photoreceptor - light
• thermoreceptor - heat
• proprioceptor - position of body in space

Question 14

Afferent (nerve fiber)

Answer 14

carry signals from periphery to CNS

Question 15

receptive field

Answer 15

area on skin where stimulus will excite a receptor

Question 16

afferent eg 1

Answer 16

• Pacinian corpuscle (touch): a type of afferent nerve fiber embedded in the skin
• receptor in the receptive field will convey physical energy to signal → travels to CNS via Aß myelinated axon fiber

Question 17

afferent eg 2

Answer 17

• Nociceptors/ free nerve endings (pain): pain receptors that respond to tissue damaging stimuli
• Eg of nociceptor is TRPV1: opens when there is a painful stimuli → cations enter
• signal travels via unmyelinated C axon fiber or thinly myelinated Aδ axon fiber to CNS

Question 18

type of fibers and their stimuli

Answer 18

• Aß thickly myelinated axon fiber (largest diameter): for touch, non noxious stimuli
• Aδ thinly myelinated axon fiber (bigger diameter than C): for pain
• C unmyelinated axon fiber (smallest diameter): for pain

Question 19

how does myelination and size affects speed of conduction of signal

Answer 19

Aß (fastest) > Aδ > C (slowest)

Question 20

Significance of different fibers (eg loss/damage)

Answer 20

• loss of Aß fibers: cannot feel touch/vibration but can still feel pain
• absence of Aδ & C fibers (eg CIPA): cannot feel pain, touch sensation normal

Question 21

Postsynaptic target for excitatory and inhibitory

Answer 21

• dendrite for excitatory synapse
• soma for inhibitory synapse

Question 22

where is AP generated

Answer 22

AP generated in axon hillock/trigger zone

Question 23

how is NT released into synaptic cleft

Answer 23

1. AP trigger opening of voltage-gated Ca2+ channels
2. Influx of Ca2+ cause fusion of synaptic vesicles to membrane of axon terminal.
3. NT released into synaptic cleft
4. NT diffuse across synaptic cleft and bind to receptor on postsynaptic dendrite/soma membrane

Question 24

what happen when NT bind to receptor on postsynaptic neuron

Answer 24

• on dendrite (excitatory): ligand-gated Na+ opens → Na+ enters → depolarisation
• on soma (inhibitory): ligand gated K+ opens, ligand gated Cl- opens → K+ leaves, Cl- enters → hyperpolarisation

Question 25

2 forces acting on K+

Answer 25

- concentration gradient - more K+ inside cell (favours movement of K+ out of cell) - electrical gradient - cell inside more negative (favours entering of K+)

Question 26

how does hypokalemia affects RMP

Answer 26

- in hypokalemia (less K+ outside cell) → more K+ will move out of cell → neuron cell hyperpolarise (more negative inside) - moves RMP away from threshold (cell become less excitable) → cause muscle paralysis

Question 27

how does hyper-excitable neurons cause altered RMP

Answer 27

- normally, inhibition of neurons by GABA cause hyperpolarisation - Decrease in GABA cause uncontrolled excitation → seizures/ epilepsy

Question 28

describe the generation of AP when touch is applied

Answer 28

1. through pharmacological receptors (eg TRPV1/nociceptor open when exposed to heat) - receptors transduce external stimuli to an electrical charge 2. mechanical pressure opens the channel → allows influx of cations → depolarisation

Question 29

what type of activities does the cortex control?

Answer 29

needed for all activities that need consciousness (aware and responsive to surrounding)

Question 30

what type of activities does the frontal lobe control?

Answer 30

personality trait

Question 31

what type of activities does the Broca's area (in left hemisphere) control?

Answer 31

expressing language

Question 32

what type of activities does the Wernicke's area (in left hemisphere) control?

Answer 32

comprehending language

Question 33

what type of activities does the Subgenual Anterior Cingulate Cortex (Subgenual ACC) control?

Answer 33

emotions - hyperactivity of subgenual ACC leads to depression (sadness and lost of interest)

Question 34

what does the medial temporal lobe contain?

Answer 34

hippocampus and amygdala

Question 35

what type of activities does the Cortical and sub-cortical regions control?

Answer 35

cognition (learning and memory), emotions and mood

Question 36

what type of activities does the hippocampus control?

Answer 36

involved in declarative memory that involves recall (eg memory of events, names, numbers) - lesion of hippocampus/ medial temporal → loss of memory (eg Alzheimer)

Question 37

what type of activities does the amygdala control?

Answer 37

for emotion and emotional memory

Question 38

eg of excitatory and inhibitory NT

Answer 38

excitatory: glutamate, epinephrine and norepinephrine inhibitory: GABA