Lecture 4

Question 1

What is the central nervous system composed of?

Answer 1

Brain and spinal cord

Question 2

What is the peripheral nervous system composed of?

Answer 2

All nerves outside the brain and spinal cord

Question 3

What are the three domains of the PNS and what are their targets?

Answer 3

• Somatic= skeletal muscle - autonomic= all targets except skeletal muscle - enteric= gut

Question 4

What is the autonomic nervous system composed of?

Answer 4

• Sympathetic nervous system - Parasympathetic nervous system

Question 5

What is the sympathetic nervous system responsible for?

Answer 5

Fight or flight response

Question 6

What is the parasympathetic nervous system responsible for?

Answer 6

Rest and digest

Question 7

What is the role of afferent fibres?

Answer 7

Carry sensory information to the CNS

Question 8

What is the role of efferent fibres?

Answer 8

Carry signals from the CNS to the periphery

Question 9

Outline the sensory reflex arc

Answer 9

Sensory receptors > afferent fibres in dorsal root > interneurone > efferent fibres in ventral root > effector cell

Question 10

Role of the dorsal horn?

Answer 10

Receives sensory input

Question 11

What is found in the lateral horn?

Answer 11

Spinal preganglionic neurones

Question 12

What is found in the ventral horn?

Answer 12

Somatic motor neurones

Question 13

What is the structure of the synapse?

Answer 13

• presynaptic terminal - mitochondrion - synaptic vesicles - active zone - synaptic cleft - postsynaptic density - postsynaptic structure

Question 14

Stages of neurotransmission

Answer 14

1) synthesis 2) storage 3) release 4) activation 5) inactivation

Question 15

What is the purpose of storing a neurotransmitter in a vesicle?

Answer 15

• protection - packaging (quanta)

Question 16

What happens in neurotransmitter release?

Answer 16

• docking of a vesicle - Ca2+ entry - exocytosis - endocytosis (recycling)

Question 17

What is the neurotransmitter released at the somatic nervous system synapse?

Answer 17

Acetylcholine

Question 18

What is the synapse called in the somatic nervous system?

Answer 18

Neuromuscular junction/endplate

Question 19

What are the two neurones found in most efferent autonomic pathways?

Answer 19

• preganglionic neurones - postganglionic neurones

Question 20

Where do postganglionic neurones synapse with?

Answer 20

• visceral smooth muscle - cardiac muscle - vascular smooth muscle - exocrine glands

Question 21

What is the neurotransmitter released from preganglionic autonomic neurones?

Answer 21

Acetylcholine

Question 22

Where are transmitters released from in the autonomic synapse?

Answer 22

Varicosities

Question 23

What is the neurotransmitter released from postganglionic parasympathetic neurones?

Answer 23

Acetylcholine

Question 24

What is the neurotransmitter released from the majority of postganglionic sympathetic neurones?

Answer 24

Noradrenaline

Question 25

What neurotransmitter is released from sympathetic postganglionic neurones innervating sweat glands?

Answer 25

Acetylcholine

Question 26

What is released from the chromaffin cells of the adrenal medulla and what is its target?

Answer 26

Adrenaline is released into blood vessels

Question 27

What are cholinoceptors?

Answer 27

Receptors upon which ACh acts

Question 28

What are the two classes of cholinoceptor?

Answer 28

- nicotinic - muscarinic

Question 29

What are adrenoceptors?

Answer 29

Receptors upon which noradrenaline acts

Question 30

What are the two classes of adrenoceptor?

Answer 30

- 𝛼 - β

Question 31

What type of receptors are nicotinic receptors?

Answer 31

ligand-gated ion channels (ionotropic)

Question 32

What type of receptors are muscarinic receptors?

Answer 32

GPCRs (metabotropic)

Question 33

What type of receptors are adrenoceptors?

Answer 33

GPCRs (metabotropic)

Question 34

How many subunits do nicotinic receptors have?

Answer 34

5 (pentameric)

Question 35

What are the types of subunits found in nicotinic receptors?

Answer 35

- 𝛼 - β - 𝛿 - 𝛾

Question 36

Why does the composition of receptor subunits matter?

Answer 36

Determines - structure - function - ion permeability

Question 37

Why is the M2 region important in ionotropic receptors?

Answer 37

Amino acid residue determines the acetyl activity of receptors of particular ions

Question 38

What happens once the ionotropic receptor is agonised?

Answer 38

Induced conformational change allowing ions to flow in/out

Question 39

What is an appropriate analogy for a nicotinic receptor- colander or pore?

Answer 39

Colander

Question 40

Why is a colander an appropriate analogy for a nicotinic receptor

Answer 40

Ions repelled by the high positive charge at the bottom of the vestibule flow in/out of fenestrations

Question 41

What are the steps of GPCR activation?

Answer 41

1) agonist binding induces conformational change in receptor 2) receptor interacts with 𝛼 G protein subunit 3) GTP displaces GDP 4) G𝛼 subunit interacts with target protein 5) G𝛼 containing GTPase hydrolyses GTP= inactivation

Question 42

What differentiates the receptor subtypes from one another e.g. M1 and M2?

Answer 42

The ligand binding pocket differs between subtypes

Question 43

How does Gβ𝛾 interact with GIRKs?

Answer 43

After separating from G𝛼, Gβ𝛾 induces opening of GIRKs= K+ ions leave the cell

Question 44

Name an example of where nAChRs are found

Answer 44

Skeletal muscle

Question 45

Names examples of where mAChRs are found

Answer 45

Salivary and sweat glands

Question 46

Name an example of where adrenoceptors are found

Answer 46

Blood vessels

Question 47

What happens to organs innervated by the parasympathetic NS?

Answer 47

- pupils= contract - tears= stimulated - salivation= stimulated - bronchi= constricted - bronchi secretions= stimulated - heart= slowed - gallbladder= constricted - gut motility= increased

Question 48

What happens to organs innervated by the sympathetic nervous system?

Answer 48

- blood vessels= constricted - sweat glands= stimulated - pupils= dilated - bronchi= dilated - heart rate and contractility= increased - gut motility= slowed - stimulates production of adrenaline