Behavior Neurobiology - basics

Question 1

what makes up the nervous system:

Answer 1

neurons, glial cells, muscle cells

Question 2

glial cells =

Answer 2

sit amongst neurons and form specialised wrappings around axons = insulate neurons to speed up transmission

Question 3

PNS glial cells -

Answer 3

schwann cells - myelination of axons

satellite cells - similar to astrocytes

Question 4

CNS glial cells -

Answer 4

oligodendrocytes - cellular extensions forming the myelin sheath around axons

microglia - brain macrophages, clear infections and debris

astrocytes - form scar tissue after injury

Question 5

muscle cells -

Answer 5

are electrically excitable non-neural cells that receive signals from neurons - generate movements (or electrical fields in electric fish)

Question 6

sensory neurons -

Answer 6

usually associated with non-neuronal cells that help in signal detection through mechanical means

Question 7

sensory receptors:

Answer 7

act as transducers (convert energy into different forms)

exteroceptor = near surface of body (external environment)

interoceptors = deep within the body (internal environment)

proprioceptor = monitor the relationship between external and internal, position, movement and orientation relating to gravity

Question 8

sensory neurons (afferent) -

Answer 8

cells that conduct action potentials towards the CNS

carry somatic signals from skin, joints, skeletal muscle, sensory organs

carry autonomic signals from visceral organs (heart, lungs, vessels)

Question 9

interneurons -

Answer 9

from the CNS and link the sensory and motor neurons

they integrate and interpret sensory info and initiate appropriate response behaviours, which they transfer to motor neurons

Question 10

motor neurons (efferent) -

Answer 10

multipolar shaped cells that conduct action potentials out of the CNS

excitatory = depolarisation (promotes generation of action potentials

inhibitory = hyperpolarisation (prevents action potential)

Question 11

how do we study the nervous system?

Answer 11

physiology - record electrical activity, optical imaging, brain scans (NMR, PET, MRI)

anatomy - staining neurons (golgi stain, intracellular filing)

immunocytochemistry - monoclonal antibodies raised against neurotransmitters)

molecular biology - manipulate patterns of gene expression to determine where specific neurons are formed

make predictions from behaviour

Question 12

maintenance of conc. gradient:

Answer 12

Na+/K+ -ATPase pumps 3 Na+ ut and 2 K+ in

resting membrane potential = -65mv measured by placing a microelectrode into cell cytoplasm

Question 13

how an action potential is generated:

Answer 13

1. resting potential (-65mv) - energy from stimulus causes Na+ to move into the neurone
2. charge becomes less negative (-50mv threshold value) = more Na+ channels open
3. potential difference becomes depolarised (+40mv) - inside of neurone is more positive
4. Na channels close, k chanels open = K+ efflux = repolarisation
5. temporary hyperpolarisation - neurone becomes too negative
6. restoration of resting potential during refractory period (limits max firing rate)

Question 14

eqbm (reversal) potential:

Answer 14

voltage at which there is no net flow of a certain ion across the membrane

K+ = -70mv

Na+ = +55mv

Ca2+ = +130mv

Cl- = -90mv

if one ion dominates, membrane potential tends towards the reversal potential for that ion…

at rest - K+ permeability is greatest

during action potential - Na+ permeability is greatest

Question 15

electrical signals code info in two forms -

Answer 15

1. action potentials propagate actively through neurone and do not decay (‘all or nothing’ signals)
2. graded responses = passively propagating, decaying changes in membrane potential

Question 16

types of signalling within a nerve cell:

Answer 16

1. voltage-gated ion channels
2. ligand-gated ion channels
3. spike threshold - membrane potential at which Na+ channels open leading to generation of action potential
4. generator potential - graded potential in sensory neurons which generates action potentials

Question 17

terms to describe firing patterns:

Answer 17

phasic = neurons fire short burts of action potentials (e.g. sensory hair neuron)

tonic = neurones fire action potetnials constantly (e.g. muscle tesnion receptors)

endogenous bursters = neurones repeatedly fire short bursts (e.g. snail salivary neurons)

Question 18

how synapses work:

Answer 18

1. action potential causes depolaristaion of presynaptic knob - calcium influx
2. calcium binds to synaptotagmin
3. vesicles brought to membrane and snare complex makes a fusion pore
4. exocytosis and diffusion across cleft
5. binds to complementar receptors - sodium influx causes depolarisation and generates action potential

Question 19

excitatory synapse -

Answer 19

excitatory transmitters bind to sodium or calcium ligand-gated channel = cause depolarisation = generate excitatory postsynaptic potential

e.g. acetylcholine, glutamate

Question 20

inhibitory synapse -

Answer 20

inhibitory transmitters bind to potassium or chloride ligand-gated channel = cause hyperpolarisation = generate inhibitory postsynaptic potential

e.g. glycine, GABA

Question 21

property of chemical synapses: summation

Answer 21

(signal integration)

temporal = integration of action potentials over time

spatial = integration of action potentials that arrive at multiple different places at the same time

Question 22

property of chemical synapses: facilitation and depression

Answer 22

when some neurons are repeatedly activated…

faciliattion = their synaptic connection becomes stronger

depreesion = their synaptic connection may weaken