Autonomic Nervous System

Question 1

Somatic effectors

Answer 1

Reflexes, actions, behaviours

Question 2

Autonomic effectors

Answer 2

Reflexes, coordination and optimisation (tuning body to suit behaviours)

Question 3

What does the autonomic nervous system control?

Answer 3

The ANS controls/organises physiology: blood flow, metabolism, internal organs and water balance. It manages the body to meet needs efficiently.

Question 4

What are the two main patterns of physiological regulation?

Answer 4

Maintenance: conservation and rebuilding Action: periods of peak performance.

Question 5

What parts of the CNS to preganglionic PSNS fibres leave?

Answer 5

The craniosacral.

Question 6

What part of the CNS do preganglionic SNS fibres leave?

Answer 6

Thoracolumbar: T1 to L2

Question 7

Actions of the sympathetic nervous system

Answer 7

Raises heart rate, blood pressure Relaxes and opens airways Mobilises energy stores Increases blood flow to muscles Stimulates sweating Shunts blood to heart, lungs and brain Suppresses digestion Relaxes bladder and rectum (no voiding) Also mediates sexual orgasm

Question 8

Chain ganglia

Answer 8

A component of the sympathetic nervous system. They are highly interconnected and run the length of the spinal cord. They send postganglionic fibres in every spinal nerve, innervating sweat glands, hair erectors and blood vessels. They also innervate the heart, lungs, salivary glands and pupils via special nerves.

Question 9

Collateral ganglia

Answer 9

There are three midline collateral ganglia, which innervate GI and urinary tracts, and genitals.

Question 10

Parasympahetic nervous system

Answer 10

Relaxation and refuelling (rest and digest)

Lowers blood pressure (via heart rate)

Closes off airways, slows respiration

Constriction of pupils; focus on near objects

Boosts the digestive system by increasing:

• GI smooth muscle activity
• GI blood flow
• Digestive enzyme secretion
• GI hormone secretion (nutrient absorption/use)

Contracts bladder and rectum for voiding

Sexual arousal (blood flow, glandular activity)

Question 11

Autonoic short reflex

Answer 11

Does nto involve the CNS

Question 12

Autonomic long reflex

Answer 12

Via teh spinal cord or the brainstem

Question 13

Nicotinic receptors

Answer 13

Autonomic receptor for acteylcholine

Ionotropic (ion channel), excitatory effect

Used by both SNS and PSNS at teh first synapse

Also used by alpha neurons

Question 14

Muscarinic receptors

Answer 14

Autonomic acetylcholine receptors

Metabotropic (activates internal signalling)

Used by PSNS at postganglionic synapse

Also some SNS efferents to sweat glands

Question 15

Noradrenal & adrenalin

Answer 15

Used by SNS only: postganglionic synapses, adrenal gland releases adrenaline into the blood, and tissues choose how to respond via receptors.

All receptors are metabotropic (internal signalling): alpha (vasoconstriction, GI shutdown, etc.) and beta (vasodilation, increase cardiac output, etc.)

Question 16

How do all pre-ganglionics in both the PSNS and SNS activate ganglion neurons?

Answer 16

Using ACh onto nicotinic receptors.

Question 17

What are the neurotransmitters used by post-gangionic fibres when influencing target tissues?

Answer 17

PSNS: ACh

SNS: A/NA

Question 18

Heterotropic interactions

Answer 18

One neurotransmitter affects teh release of another.

E.g. heart, myenteric plexus of the GI

Question 19

Homotropic interactions

Answer 19

Transmitter binds to presynaptic receptors on its own terminals. Self-inhibitory feedback.

Question 20

SAM axis

Answer 20

Sympathetic-adreno-medullary: adrenaline secretion by the adrenal medulla

Question 21

HPA axis

Answer 21

Hypothalamix-pituitary-adrenal: secretion of glucocorticoids (particularly cortisol) by teh adrenal cortex.

Question 22

Cortisol

Answer 22

• Normally secreted at low levels.
• Essential for normal physiology.
• Elevates on waking
• Allows body to cope with stress - adrenalectomy can make stress fatal
• Glucocorticoid - affectes glucose traffic
  
  • Gluconeogenesis in teh liver
  • Catabolic rendering down of proteins and lipids
  • Liberation of energy sources
• Facilitates A/NA/DA actions (e.g. vessels)

Question 23

Chronic cortisol elevation

Answer 23

• Caused by chronic stress
• Chronic effects are often opposite to its acute effects
• Suppresses immue function - cuts down inflammation by suppressing synthesis of arachidonic acid (source of prostaglandins)
  
  • Susceptibility to illness
  • Slowed wound healing
• Hippocampal neurogenesis is impaired - memory formation disrupted
• Sleep is disrupted - less REM, more slow-wave sleep, mroe waking (may lead to insomnia)
• Strong elevation or depression of mood may occur; sexual drive reduced
• The HPA axis can become sensitised to stresses - magnifying future responses