Nervous system

Question 1

What is the role of the nervous system?

Answer 1

To detect stimuli, process information and elicit a suitable response, which is achieved by interdependent systems (nervous and endocrine).

Question 2

What are the two main components of the nervous system?

Answer 2

Central nervous system (CNS) and the peripheral nervous system (PNS).

Question 3

What is the nervous system?

Answer 3

A system of nerve cells (neurons) throughout the body that carries information rapidly in the form of electrochemical pulses (nerve impulses).

Question 4

What are the main functions of the nervous system?

Answer 4

• Coordination and control of bodily activities
• Storing experiences (memory)
• Establish patterns of response based on prior experiences (learning)
• Programming of instinctive behaviour
• Regulation of internal and external environments

Question 5

What does the CNS consist of?

Answer 5

Brain and spinal cord.

Question 6

What is the role of the CNS?

Answer 6

To detect internal changes in the brain, receive stimuli from the peripheral nerves, process information and send nerve impulses to relevant tissues and organs to elicit a response.

Question 7

What does the PNS consist of?

Answer 7

Nerves that lie outside of the brain and spinal cord, with its role being to connect the CNS to all parts of the body.

Question 8

What are cranial nerves and spinal nerves?

Answer 8

Cranial nerves are peripheral nerves originating in the brain, whilst spinal nerves are those connected to the spinal cord.

Question 9

What is the execption for optic nerves?

Answer 9

They are cranial, but considered part of the CNS.

Question 10

What are ‘voluntary’ nerves?

Answer 10

They control skeletal muscles, comprising the somatic nervous system (SNS).

Question 11

What are ‘involuntary’ nerves?

Answer 11

They control automatic processes such as gut movement, heart rate and breathing as part of the autonomic nervous system (ANS).

Question 12

The autonomic nervous system (ANS) is divided into the…

Answer 12

…the sympathetic and parasympathetic nervous system.

Question 13

What is a nerve?

Answer 13

A bundle of neurons whose axons are parallel to one another.

Question 14

What are the two main types of cells that make up the nervous system and their basic definition?

Answer 14

Neurons (transmit impulses) and glial cells (provides structural and metabolic support to neurons).

Question 15

Describe the basic structure/features of all neurons.

Answer 15

They contain a cell body, an axon and dendrites.

Question 16

Define synapse.

Answer 16

The junction between two neurons (between the axon terminal of one neuron, and the dendrites of another neuron). The synapse junction is too wide to allow for the direct spread of electrical impulse from one neuron to another.

Question 17

How do neurons produce electrical impulses?

Answer 17

A neuron in a resting state has a small negative charge on the inside of the membrane. This potential difference is produced by the action of the sodium-potassium pump. The action of this pump means the inside of the axon membrane is negatively charged, and the outside is negatively charged.

Question 18

What are the three main types of neurons?

Answer 18

Sensory neurons, interneurons and motor neurons.

Question 19

What are the three structures that a neuron may terminate at?

Answer 19

Muscle (cause muscle cell to contract), gland (cause gland cell to secrete substance) or another neuron (conduct another electrical impulse along the neuron).

Question 20

What are neurotransmitters?

Answer 20

A chemical substance that transfers a nerve impulse across the synapse.

Question 21

Describe the process of a synapse.

Answer 21

When an electrical impulse reaches the axon terminal of a neuron, it induces the release of neurotransmitters from vesicles. The neurotransmitters diffuse across the synapse junction and combine with receptor proteins on the other neuron, inducing a response. Neurotransmitters and receptor proteins have complementary shapes, and exocytosis is involved to release neurotransmitters from a vesicle.

Question 22

What is a neuromuscular junction?

Answer 22

The site where a nerve reaches a muscle cell, which involves the neurotransmitter acetylcholine.

Question 23

What happens to neurotransmitters following secretion?

Answer 23

They are either destroyed by an enzyme, diffuse away quickly, or are absorbed by the cell that secreted them. If they remained in the synaptic cleft, it would cause continual stimulation of the next neuron or effector.

Question 24

Describe the role of sensory neurons.

Answer 24

They detect stimuli and carry a nerve impulse towards interneurons in the CNS. Stimuli is detected by specialised nerve endings (receptors), and this triggers a nerve impulse that travels along sensory neurons. Most have a structure deemed unipolar, since the soma has only one ‘process’ extending from it.

Question 25

Describe the role of interneurons.

Answer 25

Located in the brain and spinal cord, they receive signals from sensory neurons and transmit them to motor neurons. Interneurons in the brain have longer axons, while those in the spinal cord have shorter axons. They have a structure deemed multipolar, as they have many processes extending from the soma.

Question 26

Describe the role of motor neurons.

Answer 26

They carry nerve impulses from the CNS to effectors, such as muscles and glands. This results in a response, usually movement or secretion. They are multipolar, as they have many processes extending from the cell body

Question 27

What is the main role of peripheral nerves?

Answer 27

They generally carry nerve impulse to or from the CNS.

Question 28

Describe the structure of a nerve pathway from receptor to effector.

Answer 28

A sensory receptor detects a stimulus, and this triggers a nerve impulse which travels along a sensory neuron towards the spinal cord in the CNS. The impulse is transmitted along nerve fibres in the spinal cord to the brain. The information is processed by the brain, which sends a nerve impulse down the spinal cord along a motor neuron. The motor neuron carries a nerve impulse to the effector, either a muscle or a gland, and this results in a response.

Question 29

What are excitatory neurotransmitters?

Answer 29

Neurotransmitters that stimulate the nest neuron in the pathway.

Question 30

What are inhibitory neurotransmitters?

Answer 30

Neurotransmitters that block, or inhibit, a nerve impulse.

Question 31

How do neurotransmitters act?

Answer 31

By complementarily binding with receptor molecules on the membrane of the receiving cell.

Question 32

What is the neuromuscular junction?

Answer 32

The site where a nerve reaches a muscle cell.

Question 33

What would happen if a neurotransmitter remained in the synaptic cleft?

Answer 33

It would cause continual stimulation of the next neuron in the pathway or the effector.

Question 34

What is a reflex response?

Answer 34

An automatic response to a stimulus.

Question 35

How does a reflex occur?

Answer 35

The brain is not directly involved, as the signal from the receptor travels along a sensory neuron to the spinal cord, then along an interneuron to a motor neuron that signals the muscles--the effectors--to respond. This protects the organism by providing a rapid response.

Question 36

What are examples of reflex actions?

Answer 36

- Removing a hand from a hot surface - Dilation/constriction of pupil size is response to changes in light intensity - Coughing after inhaling a substance - Closing to the opening of the trachea when swallowing