OCR GCE Biology (A) Module 5.3 - Neuronal Communication

The pressure sensor found in the skin is called:

Pacinian corpuscle

Cells or sensory nerve endings that respond to a stimulus in the internal or external environment are called:

Sensory receptors

A transducer is:

A cell that converts one form of energy into another

The stimulus of temperature change is sensed by:

Temperature receptors in the skin and hypothalamus

The stimulus of chemicals in the air is sensed by:

Olfactory cells of the epithelium that lines the nose

The stimulus of changes in sound is sensed by:

Vibration receptors in the cochlea

The cessation of a response to a continuous and constant stimulus is:

Habituation

Neurones that take action potentials from the CNS to the effectors are:

Motor neurones

Neurones that take action potentials from the sensory receptor to the CNS are:

Sensory neurones

Neurones that connect sensory and motor neurones are:

Relay neurones

A neurone that is surrounded by Schwann cells is called a:

Myelinated neurone

A neurone that is not wrapped in Schwann cells is called a:

Non-myelinated neurone

"A brief reversal of the potential across the membrane of a neurone, causing a peak of +40mV compared to the resting potential of -60mV" is the definition of:

Action potential

"the potential difference across the membrane when it is at rest (-60mV)" is the definition of:

Resting potential

"All nerve impulses are identical. They are not graduated" is the definition of:

All-or-nothing law

When at rest, active transport of ions occurs at the sodium-potassium pump. In this instance, ............. ions are pumped outside the cell membrane, while ......... ions are pumped inside the cell.

Na+
K+

During depolarisation, ..................... voltage gated ion channels open, allowing this ion to diffuse into the cell.

Na+

During repolarisation, .................... voltage gated channels open, allowing this ion to diffuse out of the cell.

K+

Hyperpolarisation is caused because K+ voltage gated ion channels are slow to close after repolarisation. This occurs during the refractory period. The outcome of this is that:

Action potentials are unable to travel backwards

The potential difference across a neurone membrane at resting potential is:

-60mV

The potential difference across a neurone membrane at peak depolarisation is:

+40mV

The potential difference across a neurone membrane at the threshold value is:

-50mV

The refractory period is when:

Na+ and K+ ions are not in the correct position for an action potential to be transmitted

Action potentials that jump from one node of Ranvier to the next, thus speeding up the transmission of action potentials, is known as:

Saltatory conduction

A synapse that uses acetylcholine as its neurotransmitter is known as a:

Cholinergic synapse

A neurotransmitter is:

A chemical used as a signalling molecule between two neurones in a synapse (an example of cell signalling)

The synaptic cleft is:

The gap between the pre- and post-synaptic membranes

One way to ensure action potentials travel in one direction only across a synapse is that neurotransmitters are only produced in the:

Pre-synaptic bulb

One way to ensure action potentials travel in one direction only across a synapse is that sodium ion channels, that have receptor sites for neurotransmitters, are only found on the membrane of the:

Post-synaptic bulb

The effect of an action potential arriving at the pre-synaptic bulb is to:

Open the voltage-gated Ca2+ ion channels, allowing Ca2+ ions to diffuse into the cell

The effect of Ca2+ ions diffusing into the pre-synaptic bulb is to:

Cause the synaptic vesicles to move to, and fuse with, the pre-synaptic membrane

Acetylcholine is released from the pre-synaptic bulb by:

Exocytosis

Acetylcholine molecules move across the synaptic cleft by:

Diffusion

.................. ions diffuse into the post-synaptic bulb, which causes a new action potential to be created in the post-synaptic neurone.

Na+

The enzyme found in the synaptic cleft is:

Acetylcholinesterase

The function of the enzyme found in the synaptic cleft is to:

Hydrolyse any neurotransmitter left, in order to stop action potentials in the post-synaptic neurone, being continuously initiated when there has been no new stimulus

The effects of several excitatory post-synaptic potentials (EPSPs) when added together is called:

Summation

Temporal summation is when:

A single neurone has to have several action potentials in a short space of time, before the neurotransmitter is released from the pre-synaptic bulb.

Spatial summation is when:

Several neurones have to have carry action potentials to a single synapse, before the neurotransmitter is released from the pre-synaptic bulbs

The combination of several ESPS' can be prevented by a single

IPSP

Excitatory post-synaptic potentials (EPSP's) are:

A small number of acetylcholine molecules that diffuse across the synaptic cleft. An action potential is only propagated in the post-synaptic neurone when a threshold of several of these is reached

Inhibitory post-synaptic potentials (IPSP's) are:

Produced by some pre-synaptic neurones that reduce the effect of summation and prevent an action potential being propagated in the post-synaptic neurone

Having several pre-synaptic neurones converging at a synapse with a single post-synaptic neurone, has the effect of:

Allowing information from several different stimuli to generate a single response (e.g. of danger). This is also known as spatial summation.

Having one pre-synaptic neurone diverge to several post-synaptic neurones, allows a response to be generated in several parts of the body. This is useful in a:

Reflex arc (the body responds at the same time action potentials are passed to the brain)

The creation and strengthening of specific pathways within the nervous system are thought to be useful in:

Conscious thought and memory

Synapses can .................... ............. unwanted to low-level stimuli that the body does not need to respond to (e.g. the feeling of the shirt on your back).

Filter-out

An example of an inhibitory neurotransmitter is:

GABA

Action potentials move away from the cell body of a neurone down the:

Axon