Autonomic Nervous System

Question 1

Function of ANS

Answer 1

maintain homeostasis and respond to changes in environment eg. fight or flight

Question 2

What does the ANS do during exercise

Answer 2

increase heart rate to shunt more blood to working muscles, dilate vessels to muscles and constrict those to digestive tract, increase breathing rate, dilate airways and increase sweating to cool down

Question 3

How does ANS prepare body for digestion

Answer 3

increase blood flow to splanchnic bed- vessels around intestine, liver and adipose tissue, increase secretions of digestive glands, increase motility of digestive tract

Question 4

what is dual innervation

Answer 4

divisions have opposing effects on the target organs, but they work in a coordinated way in order to achieve the appropriate effect

Question 5

where does the sympathetic division emerge

Answer 5

thoracic lumbar region T1-L2

Question 6

where do the fibres exit in sympathetic division

Answer 6

exit with the ventral root of corresponding spinal nerve and sunspace in one of the ganglia called paraventricular ganglia/ sympathetic trunk

Question 7

explain the two neuron pathway in efferent in both divisions

Answer 7

the first neuron (preganglionic) has cell body in CNS and synapses with the second neuron which has the cell body in a ganglion and the axon reaching to the target organ

Question 8

Where do the cell bodies of preganglionic neuron in sympathetic division ?

Answer 8

lateral horn of grey matter

Question 9

what are the two sets of sympathetic ganglia ?

Answer 9

paravertebral ganglia and prevertebral ganglia

Question 10

where do the two sets of sympathetic ganglia lie

Answer 10

paravertebral ganglia lie next to spinal cord, linked to a chain on each side.
Prevertebral ganglia found in the thorax and abdomen

Question 11

What are the three paths that preganglionic fibres can take in sympathetic division

Answer 11

1. synapse in same trunk ganglion, postganglionic axons return to spinal nerve via grey ramus communicans and white ramus communicans
2. Synapse at different level, axons pass through ganglion to another trunk ganglion and synapse there
3. pass through sympathetic trunk to synapse in a collateral ganglion anterior to vertebral column

Question 12

what characteristics do parasympathetic fibres have

Answer 12

long preganglionic and short postsynpatic fibres

Question 13

why are postsympathetic fibres shorter

Answer 13

parasympathetic ganglia are nearer to target organ

Question 14

which four cranial nerves do preganglionic neurons have cell bodies in

Answer 14

oculomotor, facial, glossopharyngeal and vagus

Question 15

where do parasympathetic output originates from

Answer 15

cranial and sacral (S2-S4)

Question 16

Where do sacral nerves synapse in parasympathetic division

Answer 16

fibres form pelvic splanchnic nerves and synapse in ganglia within the walls of pelvic organs

Question 17

compare sympathetic and parasympathetic divisions in response and functions

Answer 17

sympathetic has more functions and output is more widespread and long lasting effects

Question 18

describe the cellular structure of somatic division

Answer 18

single neuron with myelinated axon from spinal cord to target muscle

Question 19

describe the cellular structure of sympathetic division

Answer 19

ganglia is close to emergence from CNS, with short preganglionic and long postganglionic

Question 20

describe the cellular structure of parasympathetic

Answer 20

ganglia near or embedded within target organs with long preganglionic and short postganglionic

Question 21

what receptors and neurotransmitters do somatic division use

Answer 21

cholinergic receptors and uses acetylcholine (Ach) and neuromuscular junction has nicotinic receptor (NIC)

Question 22

what receptors and neurotransmitters do sympathetic and parasympathetic division use in preganglionic neurons

Answer 22

cholinergic receptors with acetylcholine and neuromuscular junction has nicotinic receptor (NIC)

Question 23

what neurotransmitters do sympathetic postganglionic neurons use

Answer 23

they are adrenergic receptors and uses noradrenaline. Adrena medulla receives preganglionic stimulation and releases adrenaline. both adrenaline and noradrenaline binds to different receptors

Question 24

what neurotransmitters do parasympathetic postganglionic neurons use

Answer 24

cholinergic,but receptors on the target are muscarinic receptors,

Question 25

what does an autonomic reflex consists of

Answer 25

sensor, afferent fibre, integration centre, efferent fibre and effector

Question 26

where are chemoreceptors found

Answer 26

carotid bodies, aortic bodies

Question 27

where are central chemoreceptors found

Answer 27

medulla oblongata

Question 28

where are baroreceptors found

Answer 28

walls of internal carotid artery, aorta arch, large veins, heart right atrium

Question 29

what is the relationship between blood pressure, cardiac output and total peripheral resistance?

Answer 29

blood pressure proportional to cardiac output x resistance

Question 30

what happens in a normal baroreceptor reflex

Answer 30

blood vessels are constantly slightly constricted by sympathetic stimulation. baroreceptors are stretch receptors and are inhibitory which keeps sympathetic stimulation by tonic inhibition

Question 31

what happens when pressure drops

Answer 31

``` • Baroreceptors are less stretched ↓ • Inhibition of sympathetic centres ↓ • Sympathetic output↑ • RESULT : § Peripheral vasoconstriction increase TPR↑ § Heart rate ↑ § Force of contraction increase CO ↑ • BLOOD PRESSURE ↑ ```

Question 32

Name the two smooth muscles that control pupil

Answer 32

radial muscles for dilation (mydriasis) and circular muscle for constriction (miosis)

Question 33

describe the light reflex pathway

Answer 33

1. The sensor - retina detects an increase in light 2. Optic nerve carries this information to lateral geniculate nucleus of thalamus and occipital cortex (for vision) and pretectal nucleus in midbrain 3. This is linked to the nucleus of the Oculomotor (cranial nerve III) where preganglionic parasympathetic fibres originate 4. These synapse in ciliary ganglion and postganglionic fibres reach the circular muscle 5. Contracts and narrow the pupil

Question 34

describe the acute stress response

Answer 34

* Adrenal medulla receives sympathetic cholinergic stimulation via splanchnic nerves from thoracic segments * Adrenal chromaffin cells (postganglionic neurons) release adrenaline rather than synapse

Question 35

what happens in response to fight or flight

Answer 35

* increased arterial blood pressure * increased respiration and heart rate * increased blood flow to active muscles (and decreased blood flow to other area such as the splanchnic bed, i.e. blood vessels of the abdomen, and skin) * increased blood glucose concentration, and release of energy from adipose tissue * increased mental alertness * sweating (in order to cool down during muscle activity) * dry mouth  * block of digestion * dilated pupil, eyes adapted for far vision.

Question 36

what causes dysautonomia

Answer 36

neuropathy (disease or damage affecting nerves) due to diabetes mellitus, alcoholism, autoimmune disorders (eg. Guillain-Barre syndrome), multiple sclerosis

Question 37

what is dysautonomia

Answer 37

failure or overactivity of sympathetic or parasympathetic function

Question 38

what symptoms do primary autonomic failure have

Answer 38

inability to maintain blood pressure or upright position (orthostatic postural hypotension), dizziness, inability to sweat, inability to constrict pupils