Nervous system

Question 1

Role of neurons

Answer 1

Process sensory info + carry out motor response
-> X divide therefore cannot be replaced

Question 2

Role of neuroglia

Answer 2

Insulate, support + nourish neurons

Question 3

Structure of multipolar neuron

Answer 3

• many dendrites
• 1 axon
• cell body b/t dendrites + axon

Question 4

Structure of unipolar neuron

Answer 4

• dendrites merge onto axon
• cell body b/t dendrite + axon
  eg. sensory neuron

Question 5

Structure of bipolar neuron

Answer 5

• 1 dendrite, 1 axon
• cell body b/t dendrite + axon
• rare

Question 6

Describe astrocytes

Answer 6

• most abundant neuroglia in CNS
• provide structural support for neurons
• regulate interstitial environment b/t neurons
• maintain blood brain barrier

Question 7

Describe ependymal cells

Answer 7

produce, secrete + monitor cerebrospinal fluid around spinal cord

Question 8

Describe oligodendrocytes

Answer 8

wrap around axons providing layers of membrane that insulate axons eg. myelin sheaths (CNS)

Question 9

Describe microglia

Answer 9

-least abundant
migrate through tissue / clean up cellular debris, waste products + pathogens

Question 10

Describe satellite cells

Answer 10

regulates environment around PNS neurons

Question 11

Describe schwann cells

Answer 11

Wrap around axons providing layers of membrane that insulate axon

Question 12

Define neurotransmission

Answer 12

Transmission of info across a synapse

Question 13

Define membrane potential

Answer 13

The separation of positive and negative charges across a membrane creating a potential difference
-70mV at rest

Question 14

State how active/gated channels function

Answer 14

• open + close in response to specific stimuli
  at rest, most closed

Question 15

Describe chemically gated ion channels

Answer 15

Chemical eg. neurotransmitter binds to gate
-> gate opens + ions diffuse through

Question 16

Describe voltage gated ion channels

Answer 16

Membrane potential changes -> gate opens to enable ion flow

Question 17

Describe mechanically gated ion channels

Answer 17

Structure of gate changes due to pressure applied -> gate opens + enables ions to enter via diffusion

Question 18

Describe graded potential

Answer 18

Whereby a small, local + temporary change in membrane potential occurs
-> caused by chem/mechanical stimulus opening active channel in dendrite

Question 19

Describe the function of an axon potential

Answer 19

Enables the travelling of info from cell body to axon terminals
-> starts at axon hillock + reaches axon terminal

Question 20

Describe the phases of an action potential

Answer 20

• Resting membrane potential = -70mV, voltage gated Na+ + K+ channels closed
• Depolarisation to threshold = summation of graded potentials reaches threshold (-60mV to -55mV) / voltage gated Na+ channels open
• Activation of sodium channels + rapid depolarisation = Na+ ions rush into cell causing inside of cell to become positive / 30mV
• Inactivation of Na channels / activation of K channels = Na channels close + K channels open to enable K+ to move out of the cell
• Closing of K+ channels = k channels close as resting membrane potential restored / close slowly resulting in brief hyperpolarisation at -90mV

Question 21

Differentiate b/t myelinated + unmyelinated axons

Answer 21

Unmyelinated have continuous propagation whilst myelinated have faster propagation of action potentials as they only move through node

Question 22

Describe the process of neurotransmission

Answer 22

• action potential arrives at axon terminal
• voltage gated Ca+ channels open + Ca2+ enters axon terminal
• Ca2+ entry causes synaptic vesicles to release their contents via exocytosis
• neurotransmitters diffuse across the synaptic cleft + bind to specific receptors on the post synaptic neuron