Anatomy, Histology & Physiology (Week 20)

Question 1

What are the three main functions of the nervous system?

Answer 1

Sensory: Detects and collects sensory information via sensory neurons

Integrative: Processes sensory information via interneurons

Motor: Transmits appropriate responses to effector organs via motor neurons

Question 2

How is the Nervous system organised?

Answer 2

Central Nervous System (CNS): Brain & Spinal Cord

Peripheral Nervous System (PNS): Cranial and spinal nerves that connect CNS to the rest of the body

Question 3

What are the main components of a Neuron?

Answer 3

1. Cell Body (soma): Contains nucleus and organelles
2. Dendrites: Receive signals from other neurons
3. Axon: Sends electrical impulses away from cell body

Question 4

What are the supporting cells of the nervous system called, and what do they do?

Answer 4

Neuroglia (Glial cells): Support and protect neurones. They include:

• CNS Glial cells: Astrocytes, Oligodendrocytes, Microglia, Ependymal Cells
• PNS Glial Cells: Schwann cells, Satellite Cells

Question 5

What is the difference between Gray Matter and White Matter?

Answer 5

• Gray Matter: Contains neuron cell bodies, dendrites, and unmyelinated axons.
• White Matter: Contains myelinated axons, allowing for faster impulse transmission

Question 6

What is membrane potential?

Answer 6

Difference in electrical charge across neurone’s membrane, due to unequal distribution of ions inside and outside the cell

Question 7

What is the resting membrane potential of a neuron?

Answer 7

Approximately -70mV with:

• More K+ inside the neuron
• More Na+ outside the neuron
• Maintained by the sodium potassium pump

Question 8

How does the sodium- potassium pump work?

Answer 8

Actively transports 3x Na+ out and 2x K+ in maintaining the negative charge inside the neuron.

Question 9

What is an action potential and how is it triggered?

Answer 9

A nerve impulse caused by a rapid change in membrane potential.

Triggered when the membrane potential reaches the threshold (-55mV), causing voltage-gated Na+ channels to open.

Question 10

Describe the stages of an action potential

Answer 10

1. Depolarisation: Na+ enters, making the inside more positive (+30mV)
2. Repolarisation: K+ exits, restoring a negative charge
3. Hyperpolarisation: Brief overshoot below -70mV before stabilising.W

Question 11

What is the all-or-nothing principle?

Answer 11

If a neuron reaches the threshold (-55mV), an action potential ALWAYS occurs. A stronger stimulus does not produce a stronger impulse - just a higher frequency of impulses.

Question 12

How do neurons conduct impulses along their axons?

Answer 12

• Unmyelinated axons: Continuous conduction (slow)
• Myelinated axons: Saltatory Conduction (fast) - impulse “jumps” between nodes of Ranvier

Question 13

What is a Synapse?

Answer 13

A functional junction where a neuron communicates with another neuron or an effector (muscle/gland).

Question 14

What are the components of a synapse?

Answer 14

Presynaptic Neuron: Sends signal
Synaptic Cleft: Gap between Neurons
Postsynaptic neuron: Receives signal