Muscle And Synapses L3

Question 1

Two types of ion channels

Answer 1

• voltage gates ion channels (closed @ RMP, opens at stimuli)
• ligand gates ion channels

Question 2

How is the Afferent neuron activated ?

Answer 2

Muscle stretch (stretch reflex) or other sensory stimuli

Question 3

Muscle stretch (stretch reflex) or other sensory stimuli =

Answer 3

opening of the Na+ recpetors, entry into afferent fibre and depol. Of the afferent neuron.

Question 4

If the neurons entry is sufficient to depolarization the neuron to its threshold (-90mV), the result is the

Answer 4

Opening of voltage gates channel and AP

Question 5

Membrane depolarization =

Answer 5

Opening of voltage gated Na+ channel, allowing for the flow of Na+ ions inside the neuron

Question 6

Influx of Na ions brings the memb pot. Closer to the

Answer 6

equilibrium pot. (+55mV)

Question 7

Synaptic transmission steps (8X)

Answer 7

1) AP arrives in presynaptic terminal
2) presynaptic terminal depolarizers
3) voltage gates Ca+ channel opens
4) Ca+ influx into the presynaptic terminal
5) Ca+ ions causes synaptic vesicles to fuse with presynaptic membrane
6) transmitter released by exocytosis and diffuses across synaptic cleft. Bind to, and open ligand gated ion channels.
7) ions flow across membrane as dictated by their conc. Gradients and depolarizes (EPSP) or hyperpolarizes (IPSP) postsynaptic cell [directly-gated]
8) transmitter removed and recycled or degraded. Ion channel closes, PSP ends

Question 8

Presynaptic neuron can a be either

Answer 8

Excitatory (EPSP) or inhibitory (IPSP)

Question 9

(EPSP) excitatory postsynaptic potential

Answer 9

Release of excitatory NT (glutamate)

• glutamate binds to receptor and opens ligand gates Na+
• Na+ enters postsynaptic cell and results in small depolarization known as excitatory postsynaptic potentials (EPSP).

Question 10

Are EPSP above or below threshold?

Answer 10

Below threshold, subthreshold

Question 11

(ISPS) inhibitory postsynaptic potential

Answer 11

Releases inhibitory NT (GABA)

• GABA binds to receptor and opens ligand gates Cl- channels
• Cl- enters postsynaptic cell and results in small hyperpolarization known as inhibitory postsynaptic potential (IPSP) and prevents generation of AP

Question 12

What are the steps for AP ?

Answer 12

• resting
• depolarization
• repolarization
• hyperpolarization
• resting

Question 13

Resting phase for AP

Answer 13

Voltage gated Na+ channels at resting state, K voltage gated channels are closed

Relative permeability: K+»Na+

Question 14

Depolarization phase of AP

Answer 14

Stimulus causes voltage gated Na+ channels to open,

Relative permeability: Na+»»K+

Question 15

Repolarization phase of AP

Absolute refractory period

Answer 15

Voltage gated K+ channels open, Na+ channels close

Relative permeability: K+»»Na+

Question 16

Hyperpolarization phase of AP

Relative refractory period

Answer 16

Voltage gated K+ channels are still open, Na+ channels are in resting state.

Relative permeability: K+»Na+

Goes back to resting after this.