A2 - Nervous system

Question 1

Central Nervous System (CNS)

Answer 1

Consists of the brain and spinal cord.

Question 2

Peripheral Nervous System (PNS)

Answer 2

Consists of sensory and motor neurons.

Question 3

Sensory Neurons

Answer 3

Neurons that receive information from receptors and transmit it to the CNS.

Question 4

Motor Neurons

Answer 4

Neurons that carry information from the CNS to effectors, such as muscles.

Question 5

Neurons

Answer 5

Cells that receive and transmit nerve impulses or action potentials.

Question 6

Soma

Answer 6

The large cell body of a neuron.

Question 7

Dendrites

Answer 7

Small projections on a neuron that receive signals from other neurons.

Question 8

Axon

Answer 8

A long projection of a neuron that carries nerve impulses away from the soma.

Question 9

Axon Terminal

Answer 9

The end of the axon that communicates with the dendrite of the next neuron

Question 10

Synaptic Cleft

Answer 10

The small gap between the axon terminal and the dendrite of the next neuron.

Question 11

Nerve Impulse

Answer 11

Electrical signals that carry information along neurons.

Question 12

Action Potential

Answer 12

Brief change in voltage across a neuron’s membrane, resulting in a nerve impulse

Question 13

Ion Balance

Answer 13

The equilibrium of ions (charged particles) within a nerve cell.

Question 14

Nerves

Answer 14

Bundles of neurons that form a network throughout the body.

Question 15

Neurotransmitters

Answer 15

Chemicals released by neurons that transmit signals across the synaptic cleft.

Question 16

Synaptic Cleft

Answer 16

The small gap between neurons where neurotransmitters are released and received.

Question 17

Receptors

Answer 17

Proteins on the post-synaptic membrane that bind to neurotransmitters

Question 18

Glial Cells

Answer 18

Cells that support and nourish neurons, digesting dead neurons and producing neuronal components.

Question 19

Resting Potential

Answer 19

Potential difference across the membrane of a neuron in its resting state, with the interior of the cell negative compared to the exterior.

Question 20

Concentration Gradient

Answer 20

Difference in ion concentration between the inside and outside of a neuron

Question 21

Voltage-Gated Ion Channels

Answer 21

Ion channels that open or close in response to changes in voltage.

Question 22

Threshold Voltage

Answer 22

The minimum voltage required to trigger an action potential (around -55mV).

Question 23

Depolarization

Answer 23

Change in membrane potential where the inside of the membrane becomes less negative.

Question 24

Polarization

Answer 24

State of a neuron’s membrane when at rest, with a positive charge outside and negative charge inside.

Question 25

Stimulus

Answer 25

Chemical, mechanical, thermal, or electrical signal that triggers a response in a neuron.

Question 26

Repolarization

Answer 26

Restoration of the internal negativity of a neuron after depolarization, achieved by K+ channels opening and allowing K+ to rush out of the cell. -70mV.

Question 27

Sodium-Potassium Pump

Answer 27

Protein pump that actively transports Na+ out of the cell and K+ into the cell, restoring ionic conditions.

Question 28

Hyperpolarization

Answer 28

Membrane potential falls below the resting potential, causing the interior of the membrane to become more negative than -70mV.

Question 29

Refractory Period

Answer 29

The time taken for the membrane to return to resting potential after hyperpolarization, during which an action potential cannot be generated.

Question 30

Overshoot

Answer 30

Excessive increase in the interior membrane potential during hyperpolarization.

Question 31

K+ Channels

Answer 31

Potassium ion channels that are slow to close, resulting in excessive efflux of potassium ions.

Question 32

Interior Membrane Potential

Answer 32

Electrical charge inside the neuron's membrane.

Question 33

K+ Permeability

Answer 33

Ability of potassium ions to pass through the membrane.

Question 34

Na+ Channels

Answer 34

Sodium ion channels that reset during hyperpolarization.

Question 35

K+ Efflux

Answer 35

Outward flow or diffusion of potassium ions.

Question 36

Unidirectional Signal

Answer 36

Hyperpolarization prevents the neuron from receiving another stimulus and ensures that the signal proceeds in one direction only.

Question 37

Signal Propagation

Answer 37

The transmission of an action potential along an axon.

Question 38

Nerve Impulse Speed

Answer 38

The speed at which a nerve impulse travels in humans

Question 39

Unmyelinated Fibers

Answer 39

Nerve fibers without a myelin sheath, where nerve impulses travel at a speed of 1-3 m/s.

Question 40

Myelinated Fibers

Answer 40

Nerve fibers with a myelin sheath, where nerve impulses travel at a speed of 3-120 m/s.

Question 41

Axon Diameter

Answer 41

The size of the axon, with larger axons allowing for faster conduction of nerve impulses.

Question 42

Myelination

Answer 42

The presence of myelin around a neuron, which increases the speed of nerve impulse conduction.

Question 43

Number of Synapses

Answer 43

The quantity of synapses involved in transmitting a nerve impulse, with fewer synapses resulting in faster communication.

Question 44

Myelin Sheath

Answer 44

Fatty insulating layer around the axon, formed by Schwann cells, which enhances the speed of action potential travel.

Question 45

Schwann Cells

Answer 45

Specialized cells that wrap around the axon to form the myelin sheath

Question 46

Nodes of Ranvier

Answer 46

Exposed areas on the myelinated axon where ion exchange occurs.

Question 47

Saltatory Conduction

Answer 47

The process of the nerve signal jumping from one node of Ranvier to the next along a myelinated axon, significantly increasing conduction speed.

Question 48

Synapse

Answer 48

The junction where two neurons meet, allowing communication between them

Question 49

Presynaptic Neuron

Answer 49

Neuron carrying the nerve impulse towards the synaptic cleft.

Question 50

Postsynaptic Neuron

Answer 50

Neuron receiving the nerve impulse from the presynaptic neuron and carrying it away.

Question 51

Neurotransmitters

Answer 51

Chemical molecules used by the nervous system to transmit messages between neurons or from neurons to muscles.

Question 52

Dendrites

Answer 52

Branch-like projections at the end of a neuron's axon that receive signals from other neurons.

Question 53

Receptor Molecules

Answer 53

Molecules on the membrane of the postsynaptic neuron that bind to neurotransmitters.

Question 54

Acetylcholine

Answer 54

A common neurotransmitter responsible for muscle contraction.

Question 55

Action Potential Arrival

Answer 55

The action potential reaches the pre-synaptic membrane at the end of the axon.

Question 56

Calcium Ion Entry

Answer 56

Calcium ion channels open, allowing calcium ions (Ca+2) to enter the axon.

Question 57

Vesicle Movement

Answer 57

Vesicles containing neurotransmitters move towards the pre-synaptic membrane.

Question 58

Vesicle Fusion and Release

Answer 58

Vesicles fuse with the pre-synaptic membrane and release neurotransmitters into the synaptic cleft.

Question 59

Neurotransmitter Diffusion

Answer 59

Neurotransmitters diffuse across the synaptic cleft from high to low concentration, down a concentration gradient.

Question 60

Receptor Binding

Answer 60

Neurotransmitters bind to receptors on the post-synaptic cell membrane.

Question 61

Sodium Ion Entry

Answer 61

Sodium ion channels open in the post-synaptic membrane, allowing sodium ions to enter and depolarize the membrane.

Question 62

Neurotransmitter Recycling

Answer 62

Neurotransmitters are recycled through enzyme degradation or re-uptake into the pre-synaptic neuron.

Question 63

Neurotransmitter Removal

Answer 63

Neurotransmitters are removed from the synaptic cleft to prevent continuous stimulation, either by re-uptake or enzyme degradation.

Question 64

Threshold Level

Answer 64

The minimum level of neurotransmitter required to produce a postsynaptic action potential.