Question

1. Define autonomic nervous system and explain its relationship to the peripheral nervous system.
2. Compare the functions of the sympathetic and parasympathetic division of the ANS.
3. Describe the difference between somatic and autonomic motor pathways.
4. Describe a visceral reflex arc.
5. Compare the anatomy of the sympathetic and parasympathetic division of the ANS.
6. Describe major pathways of the parasympathetic division of ANS.
7. Describe sympathetic innervation of the adrenal glands.
8. Describe how neurotransmitters/receptor interact to determine response of effector.

9. Describe the effects of the two ANS divisions.
   

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Answer 1

1. Autonomic nervous system is the efferent (motor)division of the PNS that innervates cardiac and smooth muscles and glands: it is also called the involuntary or visceral motor system.

2. Sympathetic system prepares our body to respond to an emergency situation such as high intensity excercise

Parasympathetic division keeps body energy use as low as possible while doing digestion and elimination activities.

3. The Somatic nervous system stimulates skeletal muscles while autonomic nervous system innervates cardiac, smooth muscles and glands .

The neurotransmitter released by somatic nervous system is acetylcholine which is excitatory while the neurotransmitter released by ANS are epinephrine and acetylcholine ,and both may have either inhibitory or excitatory effect.

There is overlap between somatic and autonomic nervous system ,and most bidy responses to changing environment involve skeletal muscle activity and visceral responses.

4. Visceral reflex arc:

Recetors- afferent neurons- interneuron- efferent neuron-effector

Example–

Receptors- nerve endings that detect tissue damge,stretch, blood pH, body temperature and other internal stimuli

Afferent neurons- lead towards CNS

interneuron- in the CNS

Efferent neurons- carry motor signals away from CNS

Effectors: make adjustments

BAROREFLEX:

1)High BP detected by arterial stretch receptors

2) afferent neuron carries signal to CNS

3)efferent signal travel towards the heart

4)heart slows down by reducing BP.

5. ANATOMY OF SYMPATHETIC AND PARASYMPATHETIC NERVOUS SYSTEM:

–Origin sites : Parasympathetic axon fibers emerge from the brain and sacral spinal cord(craniosacral). Sympathetic axon fibers originates from the thoracolumbar region of the spinal cord

–Length of fibres: Parasympathetic division has long preganglionic and short post ganglionic fibres while the Sympathetic division has short preganglionic and long postganglionic fibres.

–Location of the ganglia : Most Parasympathetic ganglia are located in the visceral effector organs. Sympathetic chain ganglia lie close to the spinal cord.

6. Parasympathetic system pathway:

– the preganglionic axons extend from the CNS nearly all the way to the structures to be innervated,where they synapse with ganglionic neurons in the teminal ganglia.

–the cranial outflow consists of preganglionic fibers that run in the occulomotor,facial, glossopharyngeal, and vagus cranial nerves.

–the rest of the large intestine and pelvic organs are served by sacral outflow ,which arises from neurons located in the lateral gray matter of spinal cord segments S2-S4.

7. Sympathetic innervation of adrenal gland:

Some preganglionic fibres pass directly to the adrenal medulla without synapsing,unlike others with synapse with prevertebral ganglia.

These upon stimulation,medullary cells secrete epinephrine and norepinephrine into the blood.

8. Neurotransmitter binds to the receptor producing a cascade of reactions that lead to the physiological response in effector.

However the response is determined based on the neurotransmitter that produces excitatory or inhibitory effect.

9. Sympathetic system produces effects such as vasoconstriction, accelerate the heart rate,decrease the mobility of large intestine, widens the brochial passages,pupillary dilation, piloerection.

Parasympathetic system produces effects such as pupillary constriction, decreased heart rate, increased intestinal mobility, constriction of bronchial passages.