3.3 Parts of the Nervous System

What are the two major subdivisions of the nervous system?

Central Nervous System (CNS) and Peripheral Nervous System (PNS).

What does the CNS consist of?

The brain and spinal cord.

What does the PNS do?

Connects the CNS to the rest of the body via nerves.

What are the two subdivisions of the PNS?

Somatic nervous system and autonomic nervous system.

What is the somatic nervous system responsible for?

Conscious or voluntary activities; relays sensory and motor information.

What are efferent fibers?

Motor neurons that carry instructions from the CNS to muscles (efferent = exit).

What are afferent fibers?

Sensory neurons that carry information to the CNS (afferent = arrive).

What is the autonomic nervous system responsible for?

Involuntary control of internal organs and glands.

What are the two divisions of the autonomic nervous system?

Sympathetic and parasympathetic nervous systems.

What does the sympathetic nervous system do?

Prepares the body for stress-related activities (fight or flight response).

What are some effects of sympathetic activation?

• Dilates pupils

• Increases heart rate

• Relaxes bladder

• Releases glucose

• Inhibits digestion

• Secretes adrenaline

What does the parasympathetic nervous system do?

Returns the body to routine, relaxed states (rest and digest).

What are some effects of parasympathetic activation?

• Constricts pupils

• Slows heart rate

• Stimulates digestion

• Contracts bladder

• Stores glucose as glycogen

What is homeostasis?

A state of biological equilibrium where conditions are maintained at optimal levels.

What is the fight or flight response?

A physiological reaction to perceived threats that prepares the body to fight or flee.

Why is the fight or flight response less adaptive today?

Modern stressors are often psychological, leading to chronic activation and health issues.

What health problems are linked to chronic stress?

Increased risk of heart disease and impaired immune function.

What can influence stress reactivity in individuals?

Early experiences of trauma.