Dr Gawad Physiology Course Online Exams - Lecture 2 Exam

1. The autonomic N.S. differs from the somatic N.S in having:

A connector neuron which comes outside the CNS (preganglionic neuron) and a postganglionic neuron which supplies the organ

Origin from all segments of the spinal cord.

A complete control on skeletal muscles.

Origin from the anterior horn cells of the spinal cord

The correct answer is that the autonomic N.S. differs from the somatic N.S. in having a connector neuron which comes outside the CNS (preganglionic neuron) and a postganglionic neuron which supplies the organ. This means that the autonomic nervous system has a two-neuron pathway, with the preganglionic neuron originating in the CNS and synapsing with the postganglionic neuron outside of the CNS, which then innervates the target organ. In contrast, the somatic nervous system has a one-neuron pathway, with the motor neuron originating in the CNS and directly innervating skeletal muscles.

Explanation

The correct answer is that the autonomic N.S. differs from the somatic N.S. in having a connector neuron which comes outside the CNS (preganglionic neuron) and a postganglionic neuron which supplies the organ. This means that the autonomic nervous system has a two-neuron pathway, with the preganglionic neuron originating in the CNS and synapsing with the postganglionic neuron outside of the CNS, which then innervates the target organ. In contrast, the somatic nervous system has a one-neuron pathway, with the motor neuron originating in the CNS and directly innervating skeletal muscles.

2. The sympathetic preganglionic nerve fibers:

Which supply the abdominal viscera relay in the sympathetic chain.

Originate at the autonomic ganglia.

Are myelinated nerve fibers

Show minimal divergence in the autonomic ganglia.

The sympathetic preganglionic nerve fibers are myelinated nerve fibers. Myelination is the process by which a fatty substance called myelin is formed around the nerve fibers, which helps in faster conduction of nerve impulses. These fibers originate at the autonomic ganglia and relay in the sympathetic chain. They also show minimal divergence in the autonomic ganglia, meaning that they have a more direct pathway and less branching compared to other nerve fibers.

Explanation

The sympathetic preganglionic nerve fibers are myelinated nerve fibers. Myelination is the process by which a fatty substance called myelin is formed around the nerve fibers, which helps in faster conduction of nerve impulses. These fibers originate at the autonomic ganglia and relay in the sympathetic chain. They also show minimal divergence in the autonomic ganglia, meaning that they have a more direct pathway and less branching compared to other nerve fibers.

3. The following reflexes are all autonomic reflex action except:

Salivary secretion.

Micturition.

Flexion of the arm following a painful stimulus.

Acceleration of the heart after haemorrhage.

The flexion of the arm following a painful stimulus is not an autonomic reflex action because it is a voluntary movement controlled by the somatic nervous system. Autonomic reflexes, on the other hand, are involuntary responses controlled by the autonomic nervous system. Salivary secretion, micturition, and acceleration of the heart after hemorrhage are all examples of autonomic reflex actions.

Explanation

The flexion of the arm following a painful stimulus is not an autonomic reflex action because it is a voluntary movement controlled by the somatic nervous system. Autonomic reflexes, on the other hand, are involuntary responses controlled by the autonomic nervous system. Salivary secretion, micturition, and acceleration of the heart after hemorrhage are all examples of autonomic reflex actions.

4. Concerning the autonomic ganglia, all the following is true except:

They act as distributing centers.

They are 3 types.

Their chemical transmitter is acetylcholine.

The preganglionic fibers may pass through them without relay.

None of the above

The autonomic ganglia act as distributing centers, there are three types of autonomic ganglia, and their chemical transmitter is acetylcholine. However, the statement "The preganglionic fibers may pass through them without relay" is not true. Preganglionic fibers always synapse with postganglionic neurons in the autonomic ganglia before reaching their target organs.

Explanation

The autonomic ganglia act as distributing centers, there are three types of autonomic ganglia, and their chemical transmitter is acetylcholine. However, the statement "The preganglionic fibers may pass through them without relay" is not true. Preganglionic fibers always synapse with postganglionic neurons in the autonomic ganglia before reaching their target organs.

5. The autonomic ganglia all are true except:

Are relay stations for all preganglionic fibers passing through them.

Are the site of relay of efferent neurons.

Function as distributing centers.

Are located outside the CNS.

Autonomic ganglia are not relay stations for all preganglionic fibers passing through them. While autonomic ganglia do serve as relay stations for some preganglionic fibers, not all preganglionic fibers pass through them. Some preganglionic fibers synapse directly with postganglionic neurons without passing through ganglia. Therefore, the statement "Are relay stations for all preganglionic fibers passing through them" is incorrect.

Explanation

Autonomic ganglia are not relay stations for all preganglionic fibers passing through them. While autonomic ganglia do serve as relay stations for some preganglionic fibers, not all preganglionic fibers pass through them. Some preganglionic fibers synapse directly with postganglionic neurons without passing through ganglia. Therefore, the statement "Are relay stations for all preganglionic fibers passing through them" is incorrect.