NAS W2 - SOMATIC & SYNAPSE

Question 1

AFFERENT

Answer 1

• sensory - to brain

- carry sensory info from surface of body to the brain

Question 2

EFFERENT

Answer 2

• motor - to effectors
• convey commands from brain (SNS) to skeletal muscles (lead to contraction)
• has dendrites around the cell body & connects to axon BUT afferent has a naked cell body (no dendrites)

Question 3

PNS

Answer 3

connects CNS to target organs & connects sensory organs to CNS

Question 4

INITIATION SEGMENT

Answer 4

where AP is generated

Question 5

GLIAL CELLS

Answer 5

produce myelin (for myelin sheath - to protect axon)

Question 6

SNS CHARACTERISTICS

Answer 6

• bi-stable state (always either active or inactive)

- effector organ is skeletal muscle & is responsible for muscle tone of body (tensing)

Question 7

CRANIAL NERVES

Answer 7

transfer info to/from brain in relation to head & neck

Question 8

FEATURES/JOB OF DENDRITES OF SOMATIC EFFERENTS

Answer 8

• outside ones are thin & dendrite gets thicker as you get closer to cell body
• increase SA of membrane cell body (for dendrite to receive signal)

Question 9

DIF. IN INITIATION OF EFFERENT & AFFERENT IMPULSES

Answer 9

efferent - impulses generated in cell body to axons to muscles
afferent - peripheral end of axon creates impulse & passes it to side of axon which is in brain (cell body only used for metabolism & to make nutrients for cell)(not used to initiate any signals in afferent)

Question 10

HOW TO TELL IF NEURONE IS HEALTHY

Answer 10

if nucleus in centre of body

Question 11

SOMATIC MOTOR NEURONES

Answer 11

• in ventral horn of spinal cord or cranial nerve motor of brain
• heavily myelinated as very quick impulse transmission

Question 12

STRIATED MUSCLE

Answer 12

• all fibres travel in one direction & has sarcomere (skeletal & cardiac)

Question 13

NON-STRIATED MUSCLE

Answer 13

fibres flow in opp. directions (smooth)

Question 14

DISEASES THAT DEMYELINATE AXON

Answer 14

multiple sclerosis, diabetes, Guillain barre

Question 15

MYELINATION IN PNS

Answer 15

• 1 schwann cell myelinates each axon (insulated to speed up impulse conduction)
• satellite cells support support the neurones
• microglia used for immune & inflammatory functions

Question 16

MYELINATION IN CNS

Answer 16

• one single oligodendrocyte myelinates several axons at once
• damage to oligodendrocyte cell way more dangerous than PNS damage as once cell myelinates all axons not one cell per axon

Question 17

CHROMATOLYSIS

Answer 17

nucleus pushed to side of cell (indicates injured neurone)

Question 18

MEMBRANE ENVELOPE OF NERVES (IN TO OUT)

Answer 18

ENDONEURIUM - encases a single cells axon
PERINEURIUM - encases nerve fascicle (collection of axons)
EPINEURIUM - encases entire nerve & has interfascicular bands attaching adjacent nerve fascicles (perineuriums)

Question 19

SPINAL NERVES

Answer 19

transmit info to & from spinal cord in relation to rest of body

Question 20

PRIMARY SENSORY NEURONES

Answer 20

• cell bodies have no dendrites
• cell bodies appear as ganglia (round clumps)
• detect environment signals & convert them to electrical messages conducted to CNS neurones for processing

Question 21

NORMAL NEURONES (W/DENDRITES)

Answer 21

• have cell bodies in CNS & involved in receiving signals from other cells via dendrites

Question 22

AXON STRUCTURE

Answer 22

• has axon hillock (membranes of cell body that lead to axon (start as bulge))
• has initiation segment where AP are initiated

Question 23

GREY MATTER

Answer 23

• made of cell bodies of NS (more cell bodies = more grey)

Question 24

TYPES OF GLIAL CELLS

Answer 24

• ependymal - secrete CSF
• astrocytes - link neurones to blood supply
• microglial cell - phagocyte pathogens
• Schwann/oligodendrocyte - myelinate neurones

Question 25

GAP JUNCTION (ELECTRICAL SYNAPSE)

Answer 25

- fastest & easiest means of communication between cells | - common between glia-neuron or glia-glia

Question 26

CHEMICAL SYNAPSE

Answer 26

- uni-directional (pre synaptic to post) - neurotransmitter in vesicles bind with membrane & release neurotransmitter (exocytosis) which diffuses across synaptic cleft & goes to post-synaptic receptors

Question 27

RAPID TERMINATION OF SIGNAL (FOR EFFICIENCY)

Answer 27

- by enzyme breakdown (enzymes around synapse breakdown neurotransmitter)(AcH esterase hydrolyses AcH into choline + acetate in post-synaptic & choline up-taken by choline carriers in pre-synaptic to form AcH) - by re-uptake of neurotransmitter (re-uptake proteins reuptake any neurotransmitter back into pre-synaptic to be broken down by enzyme)

Question 28

IONOTROPIC RECEPTOR

Answer 28

- transmitter binds = structrural change = channel opens = ion movement (fast but slow lasting) - e.g. Ach nicotinic receptor - e.g. AP where channel opens & NA+ released

Question 29

METABOTROPIC RECEPTOR (GPCR)

Answer 29

- transmitter binds = activates G-protein = activates effector = indirect effects on excitability (slower but last long) - activated GPCR can open/close ion channels or stimulate/inhibit enzymes - e.g. ACH muscarinic

Question 30

HOW SYNAPTIC INPUT LOCATION IMPACTS INFLUENCE

Answer 30

Synaptic input closer to cell body/axon hillock = more influence

Question 31

EPSP

Answer 31

small excitatory post synaptic potential (not big enough for threshold)

Question 32

SPATIAL SUMMATION

Answer 32

summing of post synaptic potentials generated at separate synapses (many small EPSP = more NA+ influx = reaches threshold)

Question 33

TEMPORAL SUMMATION

Answer 33

summary of rapid succession of post synaptic potential but from ONE synapse