ANS 1

Question 1

describe the organisation of the nervous system

Answer 1

• CNS - brain and spinal cord
• PNS - motor & sensory neurons, somatic and ANS divisions
• ANS - parasympathetic vs sympathetic

Question 2

what is the peripheral NS?

where are the cell bodies and peripheral nerves?

Answer 2

• anything not in the brain or spinal cord
• cell bodies are located in the spinal cord or in ganglia (collection of cell bodies)
• peripheral nerves are either - somatic NS (sensory and motor nerves) or autonomic NS (controls smooth muscle and gland secretions and enteric NS)

Question 3

what is the ANS and briefly describe what it controls

Answer 3

• ANS controls multiple systems that maintain homeostasis
• eg it controls blood pressure, metabolism, gut mobility, digestion, reproductive function etc
• involuntary - subconscious

Question 4

what does the NTS stand for?

Answer 4

nucleus tractus solitarri - nuclei in the brainstem that receives many inputs from the cranial nerves

Question 5

how are the efferent nerves organised in the ANS?

Answer 5

• two distinct branches
• pre and post ganglionic neurons

Question 6

what 2 branches is the ANS divided into?

Answer 6

• parasympathetic
• sympathetic

Question 7

Describe the parasympathetic system PNS

eg functions

Answer 7

• rest and digest functions
• GI acid secretion
• GI motility - increases motility
• pupil constriction and lens adjustment
• heart rate - reduces
• often overridden by the SNS

Question 8

describe the sympathetic NS

Answer 8

• often described as ‘fight or flight’
• functions include increasing the hr, airway dilation (bronchodilation), dilates pupil of eye, decreases gut motility and secretions

Question 9

what are the **3 different types of interaction **between the SNS and the PSNS?

Answer 9

• **antagonistic **- act in opposing directions
• **complementary **- both act similarly
• co -operative - both play a role at some stage in overal function

Question 10

describe the **antagonistic effects **of the SNS and PSNS

Answer 10

• heart rate - SNS increases it and PNS decreases it
• gut motility - SNS decreawes contraction and PNS increases contraction
• pupil pf the eye - SNS dilates the pupil and PSNS constricts the pupil

Question 11

what is an example of a **complimentary effect **of SNS and PNS?

Answer 11

• saliva
• primarily controlled by the PNS in response to various stimuli - eg if there is food in the mouth etc
• SNS input changes the composition of saliva but not the volume made (makes it thicker and conatin more protein)

Question 12

Describe the **co-operative effects **of the SNS and PNS

2 examples

Answer 12

1. **pupil of the eye and lens **
   * sns causes dilation of the pupil and pns causes focussing of the lens
2. reproduction
   * PNS causes erection through the dilation of blood vessels
   * SNS causes ejaculation by constriction of smooth muscle

Question 13

what is a pre-ganglionic vs post ganglionic neuron?

Answer 13

• pre-ganglionic neuron - cell body in the brain stem or spinal cord
• post ganglionic neuron - collection of cell bodies outside the CNS

Question 14

what is the anatomical definition of the SNS?

Answer 14

• thoraco-lumbar (T1-L2)

Question 15

What is the** anatomical definition** of the PSNS?

Answer 15

• cranio-sacral
• crain nerves III,VII,IX and X)
• sacral segments S2-S4

Question 16

describe the length of the pre and post ganglionic fibres in the PSNS

Answer 16

• in the PNS, ganglia are **close to the target tissue **
• therefore there are** long pre-ganglionic fibres**
  *** short post ganglionic fibres **

Question 17

describe the length of the pre and post ganglionic fibres in the SNS

Answer 17

• fibres in the SNS are arranged in a **chain close to and on either side of the spinal cord **
• short pre-ganglionic fibres
  * long post-ganglionic fibres

Question 18

what neurotransmitters do the post ganglionic fibres of the PSNS and the SNS release?

Answer 18

• PNS post-ganglionic fibres release Ach
• SNS post-ganglionic fibres release noradrenaline (NA)
• NB - some SNS fibres tp sweatglands and pilorector muscles are cholinergic

Question 19

what do pre-ganglionic neurons of both the PNS & the SNS release?

Answer 19

Acetylcholine

Question 20

where are the adrenal glands located and what NT’s do they release & what area of the gland is an extension of the SNS & how?

Answer 20

• the adrenal medulla of the adrenal glands is an extension of the SNS
• adrenal glands sit next to the kidney (ad renal) and secrete catecholmines (NA & Adr) from the medulla
• sympathetic pre-ganglionic fibres stimulate chromaffin cells in the medulla leading to release of adr and NA

Question 21

what is neural tone in the ANS?

Answer 21

• it is not the case that the ANS is switched on or off as required
• at rest, there is basal activity in both the SNS and PNS known as neural tone
• ie the SNS tone keeps the blood vessels slightly constricted and the PNS tone keeps the HR under 100bpm

Question 22

what centre of the CNS is the site of cardio and resp control?

Answer 22

• the brain stem - pons & medulla
• they receive afferents from both baro and chemo receptors

Question 23

what is the function of the hypothalamus in terms of the ANS?

Answer 23

• set point control in a number of negative feedback control systems including temperature, osmolality and hunger