3.1 The Concept Of The Synapse

Question 0

Sherrington (1906) studied ____ - automatic muscular responses to stimuli.

Answer 0

reflexes

Question 1

The specialised area separating one neuron from another is called a ____. Ramón y Cajal.

Answer 1

synapse

Question 2

In a leg flexion reflex, a sensory neuron excites a second neuron, which in turn excites a motor neuron, which excites a muscle. The circuit from the sensory neuron to muscle is called a ____ ___.

Answer 2

reflex arc

Question 3

Sherrington found that the speed of conduction through the reflex arc varied but was never more than about __ m/s. In contrast, previous research had measured action potential velocities along sensory motor neurons in about __ m/s.

Answer 3

15 : 40

Question 4

Shenton concluded that some process was slowing ____ through the reflex, and he inferred that the delay must occur where one neuron communicates with another.

Answer 4

conduction

Question 5

Sherrington found that repeated stimuli within a brief time have a cumulative effect. He referred to this phenomenon as ____ ____ (summation overtime).

Answer 5

temporal summation

Question 6

Sherrington surmised that a single pinch did not reach the ____ of ____ for the neuron.

Answer 6

threshold of excitation

Question 7

The neuron that delivers transmission is the ____ neuron.

Answer 7

presynaptic

Question 8

The neuron that receives the transmission is the ____ neurons.

Answer 8

postsynaptic

Question 9

Sherrington proposed that this _____ excitation in the postsynaptic neuron decays over time, but it can combine with a second excitation that follows it quickly.

Answer 9

subthreshold

Question 10

Eccles (1964) discovered with micro-electrodes, after briefly stimulating an axon, a slight ____ of the membrane of the postsynaptic cell. This depolarisation is a grated potential.

Answer 10

depolarisation

Question 11

Unlike action potentials, which are always depolarisations, ____ ____ may be either depolarisations (excitatory) or hyperpolarisations (inhibitory).

Answer 11

graded potentials

Question 12

A graded depolarisation is known as an ____ ____ ____ (EPSP). It results from a flow of sodium ions into the neuron.

Answer 12

excitatory postsynaptic potential

Question 13

If an EPSP does not cause the cell to reach its threshold, the depolarisation ____ quickly.

Answer 13

decays

Question 14

Sherington also found that synapses have the property of ____ ____ – that is, summation over space. Synaptic inputs from separate locations combine their effects on a neuron.

Answer 14

spatial summation

Question 15

Sherrington concluded that pinching two points activated separate sensory neurons, who’s axons converged onto a neuron in the spinal-cord. Excitation from either sensory axon excited that spinal neuron, but not enough to reach the threshold. A ____ of excitations exceeded the threshold and produced an action potential.

Answer 15

combination

Question 16

At inhibitory synapses, input from an axon ____ the postsynaptic cell. That is, it increases the negative charge within the cell, moving it further from the threshold and decreasing the probability of an action potential.

Answer 16

hyperpolarises

Question 17

This temporary hyperpolarisation of the membrane – called an ____ ____ ____ or IPSP – resembles an EPSP.

Answer 17

inhibitory postsynaptic potential

Question 18

In IPSP occurs when synaptic input selectively opens the gates for ____ ions to leave the cell (carrying a positive charge with them) or for ____ ions to enter the cell (carrying a negative charge).

Answer 18

potassium : chloride

Question 19

Most nuerons have a ____ ____ ____, a periodic production of action potentials even without synaptic input.

Answer 19

spontaneous firing rate

Question 20

The EPSPs on a neuron ____ with the IPSPs; the balance between the two increases or decreases the neurons frequency of action potentials.

Answer 20

compete