Autonomous nervous system (Properties (viscreal reflexes are mediated by…
Autonomous nervous system
viscreal reflexes are mediated by ANS, which has two branches: parasympathetic (resting and digesting) and sympathetic (fight or flight)
Target organs are glands, cardiac muscle and smooth muscle (homeostasis)
Two neurons leading from the ANS to the effector a preganglion neuron and postganglion neuron
Baroceptor reflex (blood pressure: detected by arterial stretch receptors; afferent neuron carries signal to CNS and efferent signal travel to the heart; heart then slows, reducing BP.
Control of ANS
Cerebral cortex is influential: powerful emotions (anger, fear, anxiety) influence the ANS because of the connections between limbic system and hypothalamus
Midbrain, pons & Medulla: nuclei for cardiac & vasomotor control (BP), respiration, salivation, swallowing, sweating, bladder control and pupillary changes
Hypothalamus (major control center): nuclei for primitive functions - hunger, thirst, sex, temperature
Get more oxygen and fuel to your muscles
• Bronchodilation, increased HR & CO, vasodilation at muscles, breakdown of stored glucose (liver, muscle) & fat (adipose tissue) increases plasma [glucose] & [fats], blood vessel constriction (increased BP drives blood to where you need it).
Shut down renal/hepatic/gastrointestinal tract blood flow (and function), peripheral & visceral vasoconstriction.
– Same as Flight, plus...
– See better
• Dilate pupils
– Increased strength & skill
• Increased muscle tone, increased mental activity
– Lose less blood
• Peripheral vasoconstriction, increased clotting response
Rest and digest
Coolyourjets! – Slow down HR
• Digest things
– Increased glandular (secretion) and muscular (peristalsis) activity in the gut, increased blood flow to the gut to pick up all the goodies.
– Increased sexual arousal, eye ciliary muscle constriction
(all the better to see nearby faces) • Gotosleep...
– Pupillary constriction
Antagonise most sympathetic activities
How does it work?
ANS - two neuron from CNS to effector
Ganglion” = a collection of nerve cell bodies outside the CNS
• Preganglionic neuron cell body is in CNS
• Postganglionic neuron cell body is a ganglion
• Preganglionic neuron is myelinated (=fast)
• Postganglionic neuron is unmyelinated (=slow)