Chapter 14 Flashcards
Which neuron is involved in the sensory (afferent) division?
1st order neuron
Which neuron is involved in the motor (efferent) division?
Lower motor neuron
The ANS consists of motor neurons that
Innervate smooth and cardiac muscle and glands.
Make adjustments to ensure optimal support for body activities.
Operate via subconscious control.
Other names for the ANS
Involuntary nervous system.
General visceral motor system.
What are the divisions of the ANS?
- Sympathetic division.
- Parasympathetic division.
What is dual innveration?
Almost all visceral organs are served by both divisions, but they cause opposite effects
Where are cell bodies in the CNS found?
Spinal cord
What group fibers are found in the somatic nervous system?
Group A
Where is the cell body of the preganglionic neuron found in the parasympathetic division?
Ventral horn/lateral horn
What group fiber is the preganglionic neuron in the parasympathetic division?
Group B
What group fiber is the postganglionic neuron in the parasympathetic division?
Group C
How many neurons to get from the CNS to effector organs in the somatic nervous system?
1
How many neurons to get from the CNS to effector organs in the autonomic nervous system?
2
What is the anatomical and physiological name of the parasympathetic division?
Anatomical: craniosacral
Physiological: rest and digest
What size fibers does the parasympathetic division have?
Long pre fibers and short post fibers
Where are the ganglia of the vagus nerve and what are the effector organs?
Ganglia: within the walls of target organ
Effector organs: heart, lungs, and most visceral organs
What is the anatomical and physiological name of the sympathetic division?
Anatomical: thoracolumbar
Physiological: fight or flight
Where do neurons in the sympathetic division originate from?
Thoracic or 1st two of spinal cord
What does the white ramus run to?
From the spinal nerve out to the ganglionic trunk
What does the gray ramus run to?
From the ganglionic trunk back to the spinal nerve
What are the rami?
Axons connecting the spinal nerve and trunk
Name the four pathways of sympathetic innervation
- Synapse at same level
- Synapse at a higher level
- Synapse at a lower level
- Synapse in a distant collateral ganglion anterior to the vertebral column
What are the 2 neurotransmitters in the autonomic nervous system?
ACh and norepinephrine
What do preganglionic fibers in the ANS secrete?
ACh
What do all fiber in the parasympathetic division of the ANS secrete?
ACh
What do the postganglionic fibers of the sympathetic division secrete?
Norepinephrine
Properties of nicotinic receptors
Most common.
Ligand gated channels.
Skeletal muscle.
Cell bodies and dendrites of postganglionic fibers.
Always get EPSP.
No inhibition: only thing that matters is if its a strong enough stimulus.
Properties of muscarinic receptors
Very different.
2nd messenger system.
Some generate IPSPs.
Properties of Beta 1
Excitatory.
Increases heart rate and strength.
Stimulates renin release by kidneys.
Properties of Beta 2
Inhibitory.
Relaxation of smooth muscle.
Found in blood vessels and airways of lungs.
Properties of Alpha 1
Excitatory.
Cause contraction of smooth muscle.
How do the somatic and autonomic nervous systems differ?
- Effectors
- Efferent pathways (and their neurotransmitters)
- Target organ responses to neurotransmitters
Somatic nervous system effectors
Skeletal muscles
Autonomic nervous system effectors
Cardiac muscle
Smooth muscle
Glands
Role of parasympathetic division
Promotes maintenance activities and conserves body energy.
Its activity is illustrated in a person who relaxes, reading, after a meal.
- blood pressure, heart rate, and respiratory rates are low
- gastrointestinal tract activity is high
- pupils are constricted and lenses are accommodated for close vision
Role of sympathetic division
Mobilizes the body during activity; is the “fight-or-flight” system.
Promotes adjustments during exercise, or when threatened.
- blood flow is shunted to skeletal muscles and heart
- bronchioles dilate
- liver releases glucose
Dual innervation of the sympathetic division
Increases heart and respiratory rates, and inhibits digestion and elimination
Dual innervation of the parasympathetic division
Decreases heart and respiratory rates, and allows for digestion and the discarding of wastes
Sympathetic Tone
Sympathetic division controls blood pressure, even at rest.
Sympathetic tone: keeps the blood vessels in a continual state of partial constriction.
Sympathetic fibers fire: more rapidly to constrict blood vessels and cause blood pressure to rise; less rapidly to prompt vessels to dilate to decrease blood pressure
What is sympathetic tone essential for?
Regulating blood pressure
Parasympathetic tone
Parasympathetic division normally dominates the heart and smooth muscle of digestive and urinary tract organs: slows the heart.
Sympathetic division can override these effects during times of stress
Cooperative effects
External genitalia.
Parasympathetic fibers cause vasodilation; responsible for erection.
Sympathetic fibers cause ejaculation
Localized vs. diffuse effects
Parasympathetic division: short-lived, highly localized control over effectors.
Sympathetic division: long-lasting, bodywide effects.
- inactivated more slowly than ACh.
- NE and epinephrine are released into the blood and remain until destroyed by liver
Control of ANS functioning
Cerebral cortex (frontal lobe) –> limbic system (emotional input) –> hypothalamus (overall integration; the boss) –> brain stem –> spinal cord
