Neuron structure and function

Question 1

What are neurons?

Answer 1

Neurons are the central building blocks of the nervous system. There are 100 billion present at birth. Like all cells, neurons are made up of several different parts. Each part has a specialised function.

Question 2

Where is the semipermeable membrane?

Answer 2

A neuron’s outer surface

Question 3

What does the semipermeable membrane allow?

Answer 3

This membrane allows smaller molecules and molecules without an electrical charge to pass through it. It also stops larger or highly charged molecules

Question 4

Where is the nucleus of a neuron?

Answer 4

Located in the soma, or cell body.

Question 5

What does the some have?

Answer 5

branching extensions known as dendrites.

Question 6

The neuron is a …

Answer 6

small information processor

Question 7

What do dendrites act as?

Answer 7

input sites where signals are received from other neurons.

Question 8

How are electrical signals transmitted?

Answer 8

Transmitted electrically across the soma and down a major extension from the soma known as the axon. The axon ends at multiple terminal buttons.
The terminal buttons contain synaptic vesicles that house neurotransmitters, the chemical messengers of the nervous system.

Question 9

What are neurotransmitters?

Answer 9

The chemical messengers of the nervous system.

Question 10

What happens during signal transmission?

Answer 10

The action potential from an electrical impulse moves rapidly down the axon to the terminal buttons. At the terminal button, synaptic vesicles release neurotransmitters into the synapse.

Question 11

What are the features of a neuron’s membrane?

Answer 11

• Semipermeable membrane
• Stops large molecules
• Allows molecules without charge to pass through

Question 12

Where are neurotransmitters housed ?

Answer 12

In the synaptic vesicles

Question 13

What is a synapse?

Answer 13

At the terminal button, synaptic vesicles release neurotransmitters into the synapse.

Question 14

What is a synaptic cleft?

Answer 14

The synaptic cleft or gap is the space between two neurons.

Question 15

What is a synaptic knob?

Answer 15

The synaptic knob is the bulb shaped end of a neuron where it meets another neuron.

Question 16

Where are the synaptic vesicles?

Answer 16

The synaptic vesicles are in the synaptic knob and are where neurotransmitters are stored before release into the synaptic cleft.

Question 17

What happens once neurotransmitters are released into the synpase?

Answer 17

They travel across the small space and bind with corresponding receptors on the dendrite of an adjacent neuron.

Question 18

What is a receptor?

Answer 18

Proteins on the cell surface where neurotransmitters attach

Question 19

What type of relationship does the neurotransmitter and receptor have?

Answer 19

Lock-and-key. Specific neurotransmitters fit specific receptors.

Question 20

How is an action potential generated?

Answer 20

The neurotransmitter binds to any receptor that it fits. This binding triggers an action potential in the adjacent neuron, and the electrical impulse (i.e. the information) is transferred.

Question 21

What are the features of sensory neurons?

Answer 21

• They carry nerve impulses (information) from sensory receptors (e.g. vision, taste, touch) to the spinal cord and towards the brain. Sensory receptors are found in various locations in the body, for example in the eyes, tongue and skin.
• Sensory neurons convert information from these sensory receptors into neural impulses. When these impulses reach the brain, they are translated into sensations of, for example, visual input, heat, pain etc., so that the organism can respond appropriately.

Question 22

How do quick reflex actions occur?

Answer 22

Not all sensory information travels as far as the brain, with some neurons terminating in the spinal cord. This allows reflex actions to occur quickly without the delay of sending impulses to the brain.

Question 23

What are the features of relay neurons?

Answer 23

Relay neurons lie somewhere between the sensory input and the motor output. Relay neurons allow sensory and motor neurons to communicate with each other. These relay neurons (or interneurons) lie wholly within the brain and spinal cord.

Question 24

What are the features of motor neurons?

Answer 24

• The term motor neuron refers to neurons located in the CNS that project their axons outside the CNS and directly or indirectly control muscles. Motor neurons form synapses with muscles and control their contractions.
• When stimulated, the motor neuron releases neurotransmitters that bind to receptors on the muscle and trigger a response which leads to muscle movement. When the axon of a motor neuron fires, the muscle it has formed synapses with contracts. Muscle relaxation is caused by inhibition of the motor neuron.