specialised tissues

Question 1

nerve cell types

Answer 1

neurones, neuroglia (astrocytes, oligodendrocytes incl. Schwann, microglial, ependymal)

Question 2

neurone: defining characteristics

Answer 2

excitable, non-dividing

Question 3

neurone: projections

Answer 3

all have projections from cell body but only 1 axon

Question 4

neurone: unipolar

Answer 4

rare, 1 single axonal projection from soma

Question 5

neurone: pseudo-unipolar

Answer 5

1 axonal projection from soma which divides into 2

Question 6

neurone: bipolar

Answer 6

2 projections from cell body (axon and dendrite)

Question 7

neurone: multipolar

Answer 7

most common, 1 axon and multiple dendrites

Question 8

multipolar neurone examples

Answer 8

pyramidal, Purkinje, Golgi

Question 9

common neuronal features

Answer 9

soma containing nucleus, ribosomes and neurofilaments, axon, dendrites

Question 10

axon

Answer 10

long process from soma at “axon hillock”; branch off into “collaterals”; usually covered in myelin; send signals away from soma

Question 11

dendrites

Answer 11

highly branched; not myelinated; receive signals and deliver to soma

Question 12

astrocytes

Answer 12

most abundant; able to proliferate; maintain blood-brain barrier; main role in water movement; structural and cell repair; immune cells; maintain homeostasis (neurotransmitter release and uptake)

Question 13

oligodendrocytes

Answer 13

variable morphology and function; produce myelin (one cell myelinates many axons); in PNS called Schwann and one cell only myelinates one axon

Question 14

microglial

Answer 14

CNS immune cell

Question 15

ependymal

Answer 15

line fluid-filled ventricles and produce cerebrospinal fluid

Question 16

CNS anatomy

Answer 16

cerebral cortex, brain stem, cerebellum, spinal cord

Question 17

cerebral cortex

Answer 17

frontal, parietal, temporal and occipital (convoluted surface - gyri ridges and sulci valleys); most visible

Question 18

brain stem

Answer 18

midbrain, pons and medulla (target/source of all cranial nerves)

Question 19

cerebellum

Answer 19

motor coordination

Question 20

spinal cord

Answer 20

down medulla; conduit for neural transmission

Question 21

synapse: process

Answer 21

action potential arrives → Ca2+ influx → vesicles move and fuse to plasma membrane → neurotransmitter released by exocytosis → diffuse through cleft → bind to post-synapse receptors → action potential produced in next neurone → neurotransmitter dissociates → broken down in cleft by enzymes/recycled back into neurone by transporter proteins

Question 22

what does neurotransmission rely on

Answer 22

membrane impermeability to ions

Question 23

distribution of ions at resting membrane potential

Answer 23

Na+ Cl- and Ca2+ greater EC; K+ greater IC; membrane potential concentrated around membrane

Question 24

neurone resting potential

Answer 24

-70mV; always compared to outside of cell; negative charge IC vs EC; -40mV (more excitable) to -90mv (less excitable); hyperpolarised to 0mv

Question 25

define non-decremntal

Answer 25

size of action potential maintained throughout transmission

Question 26

neurone resting potential: voltage-gated channels

Answer 26

Na+ and K+ channels are closed

Question 27

action potential: process

Answer 27

membrane depolarised → Na+ channel opens → Na+ influx → depolarisation → K+ channel opens at slower rate → K+ eflux → repolarisation

Question 28

how is the imbalance of ions restored after an action potential

Answer 28

Na+/K+ATPase pump: at rest, Na+ in vestibule → ATP phosphorylates → active transport of Na+ out → K+ in vestibule → return to rest as K+ in

Question 29

saltatory conduction

Answer 29

action potential via cable transmission; jumps at nodes of Ranvier; speeds up transmission of action potential

Question 30

nodes of Ranvier properties

Answer 30

small gaps of non-myelinated axon; high conc. of Na+ and K+ channels