The Nervous System

Question 1

SENSORY RECEPTORS

Answer 1

Receive stimuli and form a nerve impulse

Question 2

SENSORY NEURONS

Answer 2

Transmit impulses from the sensory receptors to the interneurons.

Question 3

INTERNEURONS

Answer 3

• Are found in the brain and spinal cord.

- Act as an integration centre

Question 4

Motor Neurons

Answer 4

Conduct impulses from the interneurons to the effectors.

Question 5

EFFECTORS

Answer 5

Muscles, glands and other organs that respond to the impulses from the motor neurons.

Question 6

REFLEX ARC

Answer 6

Simple connection of neurons that result in a reflex action in response to a stimulus.

Question 7

NEURON STRUCTURE

Answer 7

• Dendrites
• Cell Body
• Axon
• Branching ends

Question 8

DENDRITES

Answer 8

Short, branching terminals that receive nerve impulses from other neurons or sensory receptors, and relay the impulse to the cell body.

Question 9

CELL BODY

Answer 9

• Contains the nucleus and is the site of the cell’s metabolic reactions.
• Processes input from the dendrites.

Question 10

AXON

Answer 10

Conducts impulses away from the cell body.

Question 11

MYELIN SHEATH

Answer 11

• Fatty, insulating layer which gives the axons a glistening white appearance.
• Protects myelinated neurons and speeds the rate of nerve impulse transmission.

Question 12

SCHWANN CELLS

Answer 12

• Type of glial cell

- From myelin by wrapping themselves around the axon.

Question 13

WHITE MATTER

Answer 13

Myelinated neurons.

Question 14

GREY MATTER

Answer 14

Unmyelinated neurons.

Question 15

MEMBRANE POTENTIAL

Answer 15

• Electrical charge separation across a cell membrane

- Form of potential energy

Question 16

RESTING MEMBRANE POTENTIAL

Answer 16

Potential difference across the membrane in a resting neuron.

Question 17

POLARIZATION

Answer 17

• Lowering the membrane potential of the cell below its equilibrium value
• In nerves, the process of generating a resting membrane potential of -70 mV.

Question 18

NODES OF RANVIER

Answer 18

• Gap in the myelin sheath insulating the axon of a myelinated nerve cell.
• The membrane of the axon is exposed and action potentials occur only at these nodes.
• Nerve impulses jump from one node of ranvier to the next.

Question 19

ACTION POTENTIAL

Answer 19

• In an axon, the change in charge that occurs when the gates of the k+ channels close and the gates of the Na+ channels open after a waves of depolarization is triggered.

Question 20

Depolarization

Answer 20

In a neuronal membrane, reducing a membrane potential to less than the resting potential of -70mV.

Question 21

THRESHOLD POTENTIAL

Answer 21

• In a neuronal membrane, the minimum change in the membrane potential required to generate an action potential
• Usually -55mV.

Question 22

REPOLARIZATION

Answer 22

Return of a nerve to its resting potential following depolarization.

Question 23

REFRACTORY PERIOD

Answer 23

• The brief time between the triggering of an impulse along an axon and the axon’s readiness for the next impulse
• During this time, the axon cannot transmit an impulse,.

Question 24

SYNAPSE

Answer 24

Junction between two neurons or between a neuron and an effector.

Question 25

NEUROMUSCULAR JUNCTION

Answer 25

Synapse between a motor neuron and a muscle cell.

Question 26

NEUROTRANSMITTER

Answer 26

Chemical messenger secreted by neurons to carry a neural signal from one neuron to another, or from a neuron to an effector, such as a gland or muscle fiber.

Question 27

ACETYLCHOLINE

Answer 27

The primary neurotransmitter of both the somatic nervous system and the parasympathetic nervous system.

Question 28

CHOLINESTERASE

Answer 28

Enzyme that breaks down the neurotransmitter acetylcholine in a synapse.