Peripheral Nervous System

What is the PNS?

The PNS consists of nerve fibers that carry information to and from the CNS, including ganglia outside the brain and spinal cord.

How many pairs of cranial nerves are there?

There are 12 pairs of cranial nerves.

What type of nerves are most cranial nerves classified as?

Most cranial nerves are mixed nerves, carrying both sensory and motor information.

How many pairs of spinal nerves are there?

There are 31 pairs of spinal nerves.

What are the two roots joining spinal nerves to the spinal cord?

The dorsal root and the ventral root.

What is contained in the dorsal root of a spinal nerve?

The dorsal root contains axons of sensory neurons.

What is contained in the ventral root of a spinal nerve?

The ventral root contains axons of motor neurons.

What does the afferent division of the PNS do?

Carries impulses into the CNS.

What type of neurons are in the somatic sensory division?

Somatic sensory neurons that carry information from receptors in skin, muscles, and joints.

What do visceral sensory neurons do?

They take impulses from internal organs to the CNS.

What does the motor division of the PNS do?

Carries impulses away from the CNS to target muscles or glands.

What is the somatic division responsible for?

Transmitting impulses from the CNS to skeletal muscles.

What is the autonomic division responsible for?

Carrying impulses from the CNS to heart muscle, involuntary muscle, and glands.

What does the autonomic division control?

The body's internal environment and many mechanisms to maintain homeostasis.

What is the main control center for the autonomic nervous system (ANS)?

Medulla Oblongata, Hypothalamus, and Cerebral Cortex.

How many motor neurons are involved in the autonomic pathway?

Two motor neurons.

What type of neuron is involved in the somatic pathway?

One motor neuron.

What is the main neurotransmitter released by the parasympathetic division?

Acetylcholine.

What type of response does the sympathetic division produce?

Responses that prepare the body for physical activity (fight-or-flight response).

What neurotransmitter is released by the sympathetic division?

Noradrenaline.

What happens to heart rate with only sympathetic stimulation?

The heart rate can increase to around 100 beats per minute.

How does parasympathetic stimulation affect heart rate?

It reduces the heart rate to around 70 to 80 beats per minute.

What occurs during a threatening situation in terms of autonomic balance?

The sympathetic stimulation becomes dominant.

What triggers the fight-or-flight response?

Fear, stress, anger, danger, or competition.

Which part of the PNS acts without conscious control?

The autonomic division.

Describe the role of the autonomic division in homeostasis.

It regulates internal body conditions to maintain stability.

What is the function of the cranial nerves?

They arise from the brain and carry components of both sensory and motor information.

How are spinal nerves classified?

All spinal nerves are mixed nerves.

What type of impulses do somatic division fibers carry?

Impulses from the CNS to skeletal muscles.

What do the sensory nerve cells in the sensory division do?

They carry impulses into the CNS.

What is the difference between somatic and autonomic divisions?

Somatic division controls voluntary actions; autonomic division controls involuntary actions.

How does the ANS maintain internal stability?

It involves many mechanisms and processes that operate automatically.

Describe how the sympathetic division affects the body.

Prepares the body for strenuous physical activity and stress responses.

What does 'visceral' refer to in visceral sensory neurons?

It refers to impulses from internal organs.

What influences the balance between parasympathetic and sympathetic stimulation?

Different physical or emotional states, such as stress or danger.

What type of signals do the nerve fibers of the ANS carry?

Impulses to heart muscle, internal organ muscles, and glands.

What is a key feature of the autonomic nervous system?

It is largely self-governing and operates without conscious awareness.

Why are the activities of the ANS usually unnoticed in daily life?

Most autonomic functions occur without conscious thought.

What maintains the stability of body functions in relation to heart rate?

The balance between sympathetic and parasympathetic stimulation.

What is the relationship between the CNS and PNS?

The PNS connects with the CNS to transmit information and responses.

How do sensory neurons from muscles and skin communicate with the CNS?

Through afferent pathways in the sensory division of the PNS.

What is the relationship between neuron pathways in the autonomic system?

Two neurons connect the CNS to the target organ for autonomic control.

What is the primary function of the sympathetic nervous system?

To prepare the body for physical activity, often referred to as the 'fight-or-flight' response.

What is the primary function of the parasympathetic nervous system?

To promote the 'rest-and-digest' response, conserving energy and restoring the body to a state of calm.

How do the sympathetic and parasympathetic nervous systems affect heart rate?

Sympathetic stimulation increases heart rate, while parasympathetic stimulation decreases heart rate.

What neurotransmitters are associated with the sympathetic nervous system?

Noradrenaline (norepinephrine) is primarily released.

What neurotransmitters are associated with the parasympathetic nervous system?

Acetylcholine is primarily released.

How do the sympathetic and parasympathetic systems affect digestive activity?

The sympathetic system inhibits digestive activity, while the parasympathetic system stimulates it.

In terms of response time, how do the sympathetic and parasympathetic systems compare?

The sympathetic system activates more rapidly compared to the slower, more sustained responses of the parasympathetic system.

What is the anatomical origin of the sympathetic nervous system fibers?

Sympathetic fibers arise from the thoracic and lumbar regions of the spinal cord.

What is the anatomical origin of the parasympathetic nervous system fibers?

Parasympathetic fibers arise from the brainstem and sacral region of the spinal cord.

How does the sympathetic nervous system influence pupils in the eyes?

It dilates the pupils to enhance vision.

How does the parasympathetic nervous system influence pupils in the eyes?

It constricts the pupils.

What happens to bronchi in the lungs during sympathetic activation?

The bronchi dilate to increase airflow.

What happens to bronchi in the lungs during parasympathetic activation?

The bronchi constrict to minimize airflow.