Chapter 9: ANS Flashcards
What does the ANS do?
It manages our physiology by regulating organs/organ systems and their smooth muscle and glands
- innervates organs NOT under voluntary control
- cardiac muscle, smooth muscle, organs, blood vessels, glands
Name the 2 divisions of the ANS and what they are associated with.
- Sympathetic: fight or flight
- Parasympathetic: rest and digest
They usually have antagonistic effects on each other
Discuss the autonomic neurons.
- Somatic motor neurons: cell bodies in spinal cord and 1 neuron traveling from spinal cord to effector
ie. voluntary, skeletal muscle - Autnomic motor neurons: 2 sets of neurons in PNS; preganglionic neuron and postganglionic neuron
Discuss the sympathetic division of the ANS.
- “Thoracolumbar division”
- preganglionic axons exit T1 - L2
- Short preganglionic axons and long post ganglionic axons (pre. synpase right outside spinal cord - paravertebral ganglia)
- travel with spinal nerves
- most act as a unit = mass activation (makes sense b/c fight or flight)
… - white rami communicantes: myelinated axons exit spinal cord ventral root and diverge onto white rami communicantes (on ramp to super highway)
- gray rami communicantes: unmyelinated axons; postganglionic neurons; return to spinal nerves and travel to effectors (off ramp)
Discuss the parasympathetic division of the ANS.
- “Craniosacral division”
- Preganglionic axons exit midbrain, medulla, pons, and S2 - S4
- Preganglionic axons long; Postganglionic axons are short and innervate organs
- Do NOT travel with spinal nerves
ie. vagus nerve
Be able to discuss an example of the antagonistic effects of the sympathetic and parasympathetic divisions of the ANS.
ie. Heart Rate:
If symp division is activated, HR increase
If parasymp division activated, HR decreases
Discuss ANS neurotransmitters.
ALL PREganglionic = ACh
Parasymp POSTganglionic = ACh
Symp POSTganglionic = Norepinephrine
Discuss the 3 ways Symp and Parasymp divisions can work together.
- Usually antagonistic (i.e. HR, pupil dilation)
- Complementary (cause similar effects to same target)
ie. salivation:
- Parasymp stimulates watery saliva
- Symp constricts blood vessels so secretion is thicker
Therefore, overload of parasymp = a lot of drooling but overload of symp = cotton mouth - Cooperative (produce diff effects that work together to produce desired effect)
ie. micturition:
Parasymp aids in detrusor muscle contraction
Symp activity on internal urethral sphincter decreases to allow it to relax and the bladder to empty.
Discuss the control of the ANS by the higher brain centers.
Hypothalamus - MAJOR regulatory center of the ANS
- body temp, hunger, thirst
Medulla - directly controls activity of ANS
- cardiovascular, pulmonary, urinary, reproductive, and digestive systems
Limbic system - autonomic responses during emotional states (blushing, pallor, fainting, sweating, racing HR)
Also influence from cerebral cortex and cerebellum
(Hypothalamus tells medulla what to do but medulla has more direct contact/control over the body)
Discuss organs WITHOUT dual innervation.
- Only innervated by simp division:
- So they are regulated by increase or decrease of symp nerve activity
- Important for body temp regulation.
Other examples:
- Adrenal medulla
- Arrector pili muscles
- Sweat glands in skin
- Most blood vessels