Autonomic tone
Normal background rate of activity represents the balance of the two systems according to the body’s changing needs
Parasympathetic tone
At rest
- Highly focused on urinary and digestive tracts
- Maintaining smooth muscle contraction
- stimulating cardiac muscles (70-80 bpm)
Sympathetic tone
At rest maintain blood vessels dilation
Parasympathetic releases the hormone
Acetylcholine (ACh)
Sympathetic releases the hormone..
norepinephrine (NE)
Receptors are located on..
Target cells
Automatic vs somatic
Uncontrolled(little conscious control) vs voluntary
Autonomic nervous system (ANS)
A motor nervous system that controls glands, cardiac muscle, and smooth muscle. Self contained, don't need thought. All needed is visceral motor functions, descending tracts. -send signals to most visc organs -ignore sensory signals -no conscious control Brain➡medulla➡synapse➡visceral organs
ANS is responsible for..
Maintaining the body’s homeostasis
Visceral reflexes
Unconscious, automatic stereotyped responses to stimulation involving visceral receptors and effectors and somewhat slower responses.
Visceral reflex arc
Receptors-detect stimuli(body temp). Stretch➡pressure on veins and arteries. Stretch of kidney,urinary system, stomach +trigger of digestion, blood chemicals(sugar,K,Na)
Afferent neurons-brain and spinal
Interneurons-determine how to respond
Efferent neurons-send response
Effectors- visceral organs than initiates a changr
Two divisions innervate same target organ by preparing body for physical activity and they are…
Sympathetic and parasymp
Sympathetic division
Prepares body for physical activity
Fight or flight response
-exercise, trauma, stress, anger, arousal
-⬆❤rate,⬆resp rate, dilate blood vessels, ⬆blood glucose levels for more energy,⬇digestion and urinary so more energy for ❤and resp
Parasympathetic division
Calms many body functions reducing energy expenditure and assists in bodily maintenance. -rest and digest -maintaining homeostasis ⬆Digestion ⬆urinary system 70-80 resting bpm Lower ❤rate if too high Turn urinary back on
ACh is…
Secreted by all preganglionic neurons in both divisions and postganglionic parasympathetic neurons.
Two types of cholinergic receptors. (Only ACh)
Muscarinic receptors- found on cardiac, glands + smooth muscle. ✳INHIBITORY✳(shuts down)
Nicotinic receptors-found near adrenal gland + on skeletal muscle
✳EXCITORY✳(increases)
NE is secreted by
Nearly all sympathetic postganglionic neurons called adrenergic fibers
Two types of NE receptors (adrenergic receptors)
Alpha-adrenergic receptors-
✳EXCITORY✳
❤, resp, blood vessels have a lot of alpha receptors
Beta-adrenergic receptors-
✳INHIBITORY✳
Digestive + urinary have a lot of beta receptors
Autonomic effects on glandular secretion..
Are often an indirect result of their effect on blood vessels. Almost 100% dependent on blood flow.
- vasodilation
- vasoconstriction release less hormone
Sympathetic effects tend to last long than..
Parasympathetic effects.
✳Takes longer for the breakdown of hormones
-half life of hormones. Amt of time it takes to get to 1/2 the total Amt
Dual innervation
Most viscera receive nerve fibers from both parasympathetic and sympathetic divisions
-antagonist effect:oppose
-cooperative effect:work together, unified act
- both divisions do not normally innervate an organ equally.
Digestion-more para
❤Rate many more symp so raise quickly
Antagonist effects of dual innervation
Oppose each other
-exerted through dual innervation of same effector cells
-exerted because each division innervate a different cells.
Symp-dilate cells +muscles of eye, survival advantage
Constricted my para
Cooperative effects of dual innervation
When two divisions act on different effectors to produce a unified effect
- symp produces mucus in stomach
- parasym causes production of saliva from ACh being triggered
Cerebral cortex
Has an influence :anger,fear,anxiety. Emotions play huge role in ANS regulation. Powerful influence
Hypothalamus
Major visceral motor control center. Hunger, thirst, sexdrive. Induce/regulate sympathetic division
Midbrain,pons, and medulla oblongata
Basic homeostatic controls
✳Controls eye movement ✳
Spinal cord reflexes
Urination+defecation. Signal for urination (stretch) is processed within spinal cord
Neuropharmacology
Study of effects of drugs on the nervous system
Sympathomimetics..
Enhance sympathetic activity
-stimulate receptors or increase norepinephrine