The Autonomic Nervous System Flashcards
Overall function of ANS
Homeostasis: Maintaining a stable internal environment within a narrow physiological range amid changing external conditions
ANS is?
Involuntary Diffuse projections Slow action Innervates smooth and cardiac muscle, and gland cells Disynaptic
Somatic motor system is?
Voluntary Specific projections Rapid action Innervates skeletal muscle Monosynaptic
The ANS consists of 3 subdivisions
Sympathetic: “Fight/flight”
Parasympathetic: “Rest/digest”
Enteric: Semi-autonomous control of digestion
Comparative anatomy- Sympathetic
Preganglionic neurons originate in thoracic and lumbar spinal cord
Ganglia located near spinal cord
1:10 ratio of pre- to post-ganglionic neurons
Comparative anatomy- Parasympathetic
Preganglionic neurons originate in brainstem and sacral spinal cord
Ganglia located near target organs
1:3 ratio of pre- to post-ganglionic neurons
Ganglion:
cluster of cell bodies in the peripheral nervous system
Neurotransmitters and receptor subtypes determine effects and timecourse of ANS innervation
Preganglionic:
Acetylcholine (ACh)
Neurotransmitters and receptor subtypes determine effects and timecourse of ANS innervation
Postganglionic:
Sympathetic: Norepinephrine
NE) and epinephrine
Parasympathetic: ACh
Neurotransmitters and receptor subtypes determine effects and timecourse of ANS innervation
Receptors:
ACh: nicotinic vs. muscarinic
NE: α- and β-adrenergic
Adrenal medulla – functionally, a?
sympathetic ganglion
Adrenal medulla fx?
Innervated by preganglionic sympathetic neurons
Releases norepinephrine and epinephrine into bloodstream
Widespread sympathomimetic effects (e.g., increased heart rate)
Cardiovascular regulation by the nervous system
Sympathetic and parasympathetic control of heart rate and force of contraction
Baroreceptor reflex
Humoral response to low blood pressure
ANS regulation of heart rate and force of contraction Sympathetic stimulation (via increased NE)
increases blood pressure
Increase in heart rate and contractile force
Constriction of blood vessels
ANS regulation of heart rate and force of contraction Parasympathetic stimulation (via increased ACh)
decreases blood pressure
Decrease in heart rate and contractile force
muscarinic (M2) antagonist in heart; increases heart rate
Atropine
*mimic sympathetic activation
β-adrenergic (β1 and β2) antagonist in heart; decreases heart rate
Propranolol
*mimic parasympathetic activation
If blood pressure falls, such as on orthostatic hypotension or in hypovolaemic shock, firing rate decreases and _________ act to help restore blood pressure by increasing heart rate.
baroreceptor reflexes
Humoral response to low blood pressure: controlled by _____-
hypothalamus
Hypothalamus controls release of hormones via the _________
pituitary
Posterior pituitary: brain
Anterior pituitary: gland
Low blood pressure is detected by __________ Which causes release of vasopressin in posterior pituitary
subfornical organ
release of vasopressin in posterior pituitary causes _________
vasoconstriction
Which acts on kidneys to increase water retention
vasoconstriction acts on _______ to increase water retention
kidneys
Low blood pressure causes _____ to be releases from kidneys
renin
Angiotensinogen + renin –> –> Angiotension II that fxs to?
Angiotensin II:
Constricts blood vessels
Acts on kidney to increase water retention
Activates neurons in subfornical organ
Opposing effects of ______ divisions enable homeostasis
sympathetic and parasympathetic
Hypothalamus coordinates ANS and ________
humoral responses
