RETINA + NERVOUS SYSTEM

Question 1

RETINA

Answer 1

light sensitive membrane that processes light before passage to optic nerve

Question 2

TRANSDUCTION

Answer 2

light —> electrical potential

Question 3

ENCODING

Answer 3

electrical potentials —> action potential sequences for retinal output

Question 4

OPTIC DISC

Answer 4

• no neural retinal or RPE

- blind spot

Question 5

FOVEA

Answer 5

• depression in the macula of retina

- inner retinal layers pushed aside to let light fall directly on the cones to give sharpest image

Question 6

PARAFOVEA

Answer 6

• rods + cones

- inner + outer nuclear layers

Question 7

PERIFOVEA

Answer 7

• circumscribes parafovea + fovea

- thickest part

Question 8

MACULA

Answer 8

• overlaps fovea, para + peri
• contains yellow pigment
• central area of retina

Question 9

FUNCTIONS OF RETINAL PIGMENT EPITHELIUM

Answer 9

1. LIGHT ABSORPTION
2. EPITHELIAL TRANSPORT
3. ACTIVE POTASSIUM TRANSPORT
4. VITAMIN A METABOLISM
5. PHOTORECEPTOR MEMBRANE RECYCLING
6. HORMONE PRODUCTION + SECRETION

Question 10

RODS

Answer 10

• less intense light
• peripheral vision
• 110-130 million/ retina
• long, slim cells

Question 11

CONES

Answer 11

• colour vision
• bright light
• wider cells
• 5-7 million/ retina

Question 12

RETINA LAYERS

Answer 12

4 cellular layers:

1. pigment epithelium
2. rods + cones
3. outer limiting membrane
   - muller cells
   - horizontal cells
   - bipolar cells
   - amacrine cells
4. ganglion cells
   - nerve fibre layer
   - inner limiting membrane

Question 13

MULLER CELLS

Answer 13

• principle glial cell of retina
• form architectural support structures
• support neuronal tissue in retina

Question 14

NEURON FUNCTION

Answer 14

• to receive, process + transmit electrochemical messages

- uses electricity + chemical interaction to communicate between themselves + targets (e.g. muscles, glands etc)

Question 15

NEUROGLIA

Answer 15

• to help neurons
• they make up half the cell volume in the CNS
• don’t generate or conduct nerve impulses

Question 16

NEURON STRUCTURE

Answer 16

• cell body
• dendrites (branching outputs)
• axon (long cylindrical output)

Question 17

TYPES OF NEURONS

Answer 17

• multipolar
• bipolar
• unipolar
• interneurons

Question 18

MULTIPOLAR

Answer 18

several dendrites + one axon

Question 19

BIPOLAR

Answer 19

one main dendrite + one axon

e.g. in retina, inner ear, olfactory system

Question 20

UNIPOLAR

Answer 20

one process that branches out; one end is dendrite + other end is axon terminal
- usually found in somatosensory pathway (touch)

Question 21

INTERNEURONS

Answer 21

• 90% of neuronal population in body
• most are multipolar
• e.g. Purkinje, Renshaw, pyramidal
• process incoming sensory info from sensory NEURONS + then elicit a motor response by activating the appropriate motor NEURONS

Question 22

WHAT CLASSIFIES THE VARIOUS NEURONS IN THE BODY?

Answer 22

structural (number of processes - axons or dendrites) + functional (electrophysiological properties) features

Question 23

WHERE DO SENSORY (AFFERENT) NEURONS CONVEY ATP?

Answer 23

INTO the CNS through cranial or spinal nerves

Question 24

WHERE DO MOTOR (EFFERENT) NEURONS CONVEY ATPS?

Answer 24

AWAY from CNS to effectors (muscles + glands) in the periphery through cranial or spinal nerves - most are multipolar

Question 25

WHAT ARE FOUND MAINLY IN THE CNS BETWEEN SENSORY + MOTOR NEURONS?

Answer 25

interneurons or association NEURONS

Question 26

ASTROCYTES

Answer 26

maintain the right chemical environment for NEURON function

Question 27

MICROGLIA

Answer 27

clean up + defend nervous system from disease

Question 28

EPENDYMAL CELLS

Answer 28

make cerebrospinal fluid

Question 29

SATELLITE CELLS

Answer 29

support NEURONS in the PNS ganglia

Question 30

SCHWANN CELLS

Answer 30

make myelin sheath that provides an insulating cover for axons in the PNS (the neurolemma in the myelin aids nerve regeneration by forming a regeneration tube)

Question 31

OLIGODENDROCYTES

Answer 31

make myelin sheath in the CNS - no neurolemma so no regeneration occurs in CNS

Question 32

GREY MATTER

Answer 32

myelin covered axons - outside in brain - inside in spinal cord

Question 33

MYELINATION

Answer 33

process of forming myelin sheath which insulates + increases nerve impulse speed

Question 34

WHITE MATTER

Answer 34

- formed from aggregations of myelinated axons from many neurons - lipid part of myelin makes appearance white

Question 35

GREY MATTER

Answer 35

- formed from neuronal cell bodies + dendrites | - lacks myelin = grey appearance

Question 36

NODES OF RANVIER

Answer 36

gaps in myelin sheath - speeds propagation

Question 37

WHERE DOES NERVE TISSUE REGENERATION OCCUR?

Answer 37

only in PNS | CNS astrocytes form scar tissue