Neurophysiology 1

do invertebrates have myelinated or non-myelinated nerve cells

non myelinated

role of glial cells

connect brain nerve cells to capillaries to deliver solutes

role of microglial cells

phagocytosis/immune response

role of myelin sheath

insulation, structure, protection, allow nerve cells to be thinner

role of neurones

communication, generate electrical signals

which cells form myelin in PNS vs CNS

PNS - Schwann cells, CNS - oligodendrocytes

pathway of AP through neurone

dendrites, cell body, axon hillock, axon, presynaptic terminals

3 types of neurones

afferent (sensory), interneurones (CNS), efferent (motor)

role of sensory neurone

receive signals from environment

3 ways sensory inputs are classified

modality (smell), stimulus energy, mechanism of transduction

what is taste mediated by in mammals

3 types of papillae (receptors in taste buds)

3 types of papillae

circumvallate, foliate, fungiform

how many elongate slender cells are in each taste bud

50-150

5 types of taste qualities

salt, sour, sweet, umami, bitter

distribution of the 3 types of papillae on the tongue

circumvallate at back, foliate on sides, fungiform in front

what is sweet, umami, bitter sensed by

G coupled protein receptors

how is salt taste controlled

H+ through channels

explain the metabotropic response to sweet, umami, bitter

ligand binds protein in membrane, conformational change of protein, GTP released, conformational change of PIP2, Ca2+ released into cytoplasm, Na+ channels open

which sensory cell types are metabotropic

sweet, bitter, umami taste chemoreceptors, vertebrate olfactory chemoreceptor, photoreceptors

2 part of body involved in CNS

spinal cord, brain

2 simple forms of integration in CNS

reflex arc, central pattern recognition (e.g. mating, digestion)

phase 1 of AP

resting phase, -60 - -80mV, membrane potential maintained by non-gated channels

phase 2 of AP

depolarisation, Na+ gated channels open

phase 3 of AP

falling, Na+ channels shut, K+ open

phase 4 of AP

hyperpolarisation

phase 5 of AP

return to resting potential

relationship between axon diameter and conduction speed

larger diameter = faster conduction speed

advantage and disadvantage of large axon

respond quickly to environment, more vulnerable to damage

what is saltatory conduction in vertebrates

AP conducts and jumps across nodes of Ranvier

advantage of saltatory conduction

increased conduction speed without need for increased axon diameter

2 types of inputs

excitatory (depolarising), inhibitory (hyperpolarising)

synapse definition

specialised site of contact of a neurone with another neurone or effector

2 types of synaptic transmission + which is most common

electrical via gap junctions, chemical (most common)

process of chemical synapse

AP reaches presynaptic terminal, voltage gated Ca2+ channels open so Ca2+ influx, vesicles fuse, neurotransmitter released into synaptic cleft and binds receptor, ions flow into post synaptic membrane, post-synaptic excitation, signal passed on

what happens when acetylcholine is released into the synaptic cleft

binds receptors, Na+ influx into post synaptic membrane

what stops the action of the neurotransmitter

enzyme degraded

2 pathways for retrieval of the vesicular membrane

classical - vesicular membrane fuses with presynaptic membrane then endocytosis,
kiss and run - vesicle fuses with membrane partially then recycled

is ionotropic or metabotropic faster

ionotropic

what is the rate limiting step in ionotropic

diffusion of neurotransmitter across synapse

what is the rate limiting step in metabotropic

time G protein receptors elicit their effect

4 transmitter classes

amines, amino acid, peptides, soluble gases

what does drug application at a synapse cause

block neurotransmitter action