Signalling💘

Question 1

Short distance signals

Answer 1

Direct (signal passed via channels called connexons)
Intracrine(substance acts within the cell usually on nucleus eg steroids)
Autocrine (substance acts on same cell but on membrane receptors eg immune cells)
Juxtacrine (substance acts on adjacent cells in contact)

Question 2

Medium distance signals

Answer 2

Paracrine (substance acts on cells nearby via dimple diffusion eg allergic reactions)

Question 3

Long distance signal

Answer 3

Endocrine (signal passed throughout body and is usually carried in the bloodstream eg adh)

Question 4

Three classes of neurons

Answer 4

Afferent neurons carry info from peripheral receptors TO cns eg sensory
Efferent neurons carry info away from cns eg motor neurons
Inter neurons carry info between neurons
Eg spinal cord

Question 5

Three main parts of neuron

Answer 5

Soma (cell body) (conveys output)
Axon(generates action potential)
Dendrites (receives input)

Question 6

Neuroglia

Answer 6

Support cells of nervous system by supplying nutrients
Destroying and digesting dead neurons
Regulating content of extra cellular space
Etc
Eg astrocytes microglia Schwann cells

Question 7

Cns

Answer 7

Brain spinal cord and retina signals carried through tracts (bundles of nerve fibers)

Question 8

Pns

Answer 8

Made up of nerves

Signals carried via neurons

Question 9

Endoneurium

Answer 9

Connective tissue which surrounds each individual nerve fiber

Question 10

Fasiculus

Answer 10

Bundle of nerve fibres with perineurium surrounding it (connective tissue)

Question 11

Epineurium

Answer 11

Connective tissue sheath which surrounds each nerve

Question 12

Synaptic transmission in neuromuscular junctions

Answer 12

Action potential arrives at axon terminal
Calcium ions open allowing ca2+ to flow in results in vesicles picking up acetylcholine and transporting it and fusing with membrane and releasing this transmitter via exocytosis and it diffuses along synaptic cleft
Binds to ach receptors channels bring sodium in potassium out of postsynaptic cell
This generates an action potential which flows through muscle fiber causin contraction
Achesterase breaks down ach bit acetate and choline and then reabsorbed and converted back into ach

Question 13

Three main classes of surface receptors

Answer 13

Ligand gated ion channels (signal binds to receptor and channel opens)
G protein coupled receptor (g protein passed on signal to effector enzyme)
Kinase linked receptors (signal passed on through intrinsic enzyme activity or by activating a kinase)

Question 14

G protein receptors

Answer 14

Trigger intercellular signalling cascades using second messengers
Two groups
Monomomeric small molecular weight gtpases
Heterotrimeric G proteins

Question 15

Kinase linked receptors

Answer 15

Also trigger intercellular signalling cascades with second messengers
There are two types serine threonine kinases and tyrosine kinases
Two groups
Receptors with intrinsic tyrosine kinase activities
Tyrosine kinase linked receptors

Question 16

Trimeric g proteins

Answer 16

Has alpha beta and gamma subunits
The alpha subunit is bound to gdp
GDP of alpha subunit is released and replaced by gtp causing activation of alpha subunit so signal is produced