Transcript
Autonomic Nervous System
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Module: Regulation
Activity: Animations
Title: Autonomic Nervous System
Introduction
1. What is the sensory function of the Autonomic Nervous System (ANS)?
Perceives visceral sensations or emotions
2. What is the function of the hypothalamus and spinal cord relative to the ANS?
The ANS control center is primarily the hypothalamus but parts of the spinal cord may also be involved.
3. Name some of the effectors regulated by the ANS.
Smooth muscle, cardiac muscle, endocrine and exocrine glands, and adipose tissue.
4. a. Identify the two ANS divisions.
Sympathetic and parasympathetic.
b. Define dual innervation and explain its function.
The phenomenon of regulating a single effector by both divisions of the ANS. This allows the modulation of the effects from each division.
5. Contrast ANS and somatic motor pathways
They differ by number of motor neurons for each pathway, presence and location of.ganglia, and number and type of neurotransmitters.
Motor Pathways: Preganglionic and Postganglionic Neurons
6. Describe somatic motor neuron structure for stimulating an effector such as a skeletal muscle.
In the SNS, one motor neuron excites the skeletal muscle effector.
7. Unlike the SNS, two ANS motor neurons carry action potentials to effectors. Describe the location and function of each of them. Note their myelination differences, too.
a. Preganglionic Neuron
Preganglionic neurons are located in the CNS within specific regions of brain and spinal cord, and send impulses along myelinated axons to postganglionic neurons. .
b. Postganglionic Neuron
The postganglionic neurons are located outside the CNS. They receive impuses from the preganglionic neurons and transmit them to effectors via unmyelinated fibers.
Motor Pathways: Ganglia
8. Describe the role of acetylcholine at the ganglia.
Released via exocytosis from the preganglionic neuron, it diffuses
across the synaptic cleft and depolarizes the membrane of the the postganglionic neuron. Sufficient depolarization will result in the generation of an action portential by the postganglionic neuron.
9. a. Describe the location of parasympathetic motor ganglia.
Within or close to the effector organs.
b. Describe the pattern that establishes a stimulation connection to only a single parasympathetic effector.
Parasympathetic ganglion has only a few postganglionic neurons, usually providing stimulation to only one effector.
10. a. Describe the location of sympathetic motor ganglia. Near the spinal cord or major abdominal arteries.
b. Describe the pattern that establishes a stimulation connection to MANY sympathetic effectors.
Sympathetic ganglion has many postganglionic neurons, usually providing stimulation to many effectors.
Motor Pathways: Neurotransmitters
11. How are autonomic neurons classified?
By the neurotransmitter they release into a synapse.
12. Identify the neurotransmitter , the deactivation enzyme
a. cholinergic neurons - Releases acetylcholine (Ach), inactivated by acetycholinestrase.
b. adrenergic neurons - Releases norepinephrine (NE), inactivated by monoamine oxidase (MAO).
13. Identify the ANS neurons that are cholinergic.
All sympathetic and parasympathetic preganglionic neurons and all parasympathetic postganglionic neurons.
14. Contrast the functions of postsynaptic receptors.
a. nicotinic receptors – Always depolarize (excite) a cell when activated.
b. muscarinic receptors – May depolarize or hyperpolarize (inhibit) a cell when
activated.
15. a. Identify the ANS neurons that are adrenergic. Most sympathetic postganglionic neurons.
b. What affect does norepinephrine (NE) have on postsynaptic membranes? Either depolarizes or hyperpolarizes the cell.
Physiological Effects of the ANS
16. Describe hypothalamus role within the ANS. Ensures a more efficient response.
17. a. When does the sympathetic division of the ANS respond and stimulate its effectors?
Dominates when the body undergoes physical or emotional stress such as hemorrhaging, embarrassment, exercise, or excitement. .
b. Identify some sympathetic responses.
Pupil dilation, increases in heart rate, force of contraction and blood pressure, bronchodilation of airways in lung.
c. How are these responses appropriate for the sympathetic “fight or flight” response?
Allows for better vision; increased blood flow and pressure for muscular activity and increased oxygen supply to the tissues. .
d. Name three reasons why the effects of sympathetic stimulation are longer lasting and more widely spread than parasympathetic stimulation.
1- motor pathways diverge to more effectors.
2- norepinephrine is deactivated more slowly than acetylcholine.
3- Norepinephrine, secreted from the adrenal medulla during times of stress, increases and spreads overall effect of NE that is released as a neurotransmitter.
18. a. Explain why the parasympathetic division is sometimes called the
“rest and digest” reaction.
Because it dominates when a person is relaxed, well fed, or asleep.
b. Identify some parasympathetic responses. Decreased heart rate, bronchoconstriction of airways in lung (opposite of sympathetic responses).
c. Define the SLUDD responses. Salivation, lacrimation, urination, digestion, defecation are ALL increased.
d. In general, define the function of parasympathetic responses. Maintains normalcy, decreases energy consumption, and increases energy conservation.
