Nerves and the ANS

Question 1

Neuronal action potential

Answer 1

1. Negative at rest (polarised) due to potassium inside of cell and chloride outside
2. Sodium ion channels open and sodium floods into cell - depolarisation
3. Calcium channels open and cell fires
4. Potassium channels open so potassium leaves cell - repolarisation

Question 2

Myelinated nerve conduction

Answer 2

Faster
Saltatory conduction
Myelin sheaths called Schwann cells
Conduction jumps between gaps called nodes of Ranvier

Question 3

Neurotransmission

Answer 3

1. Depolarisation causes vacuoles of neurotransmitter to exocytose into synaptic cleft
2. Neurotransmitter bnds to receptors on post-synaptic nerve or other targets

Question 4

Central components of the ANS

Answer 4

Hypothalamus
Brain stem
Spinal cord

Question 5

Peripheral components of the ANS

Answer 5

Sympathetic nerves

Parasympathetic nerves

Question 6

Functions of the ANS

Answer 6

Mediates neuro-humoral regulation of the internal environment
Prepares body for normal and life-threatening stress

Question 7

Function of the SNS

Answer 7

Fight or flight

Question 8

Function of the PSNS

Answer 8

Rest and digest

Question 9

Stress causing activation of SNS

Answer 9

Low BP
Low oxygen
Increased temperature
Mental stress

Question 10

Aim of the SNS

Answer 10

To increase energy by increasing levels of glucose and oxygen

Question 11

SNS receptors and messengers

Answer 11

Noradrenaline (neurotransmitter) binds to alpha 1 and 2
Adrenaline (hormone) binds to beta 2
Beta 1 binds noradrenaline and adrenaline equally

Question 12

The heart and the SNS (3)

Answer 12

Mediated by the beta 1 receptor

1. Increases SA node firing rate
2. Increases AV node conduction velocity
3. Increases contractility

Question 13

Blood vessels and the SNS (2)

Answer 13

Beta 2 receptors - vascular smooth muscle relaxation causes vasodilation
Alpha 1 receptors - vascular smooth muscle contraction causes vasoconstriction

Question 14

Drugs modulating blood vessels

Answer 14

1. Beta blockers (beta 1 antagonists) reduce heart rate and contractility
2. Beta agonists increase heart rate and contractility
3. Alpha 1 receptor enhancer - synthetic noradrenaline
4. Alpha 1 receptor blockers - hydrolazine

Question 15

Lungs and the SNS

Answer 15

Beta 2 agonists (e.g. salbutamol) mimic effect of adrenaline - bronchodilation by relaxing smooth muscle

Question 16

The kidneys and the SNS

Answer 16

Reduces urine formation

Increased adrenaline and noradrenaline release from adrenal medulla

Question 17

Adverse effects of beta antagonists (6)

Answer 17

Bradycardia
Hypotension
Depression
Impotence
Broncho-constriction
Elevated blood glucose

Question 18

Adverse effects of beta agonists (3)

Answer 18

Tachycardia
Anxiety
Problems with micturation

Question 19

Alpha agonists (3)

Answer 19

Increased heart rate
GI tract disturbances
Urinary retention

Question 20

Alpha antagonists (1)

Answer 20

Increased blood glucose

Question 21

The parasympathetic nervous system is largely controlled by…

Answer 21

the vagal nerve