Human Body Systems: Nervous System Overview

Study Notes

The nervous system is divided into two main parts: central nervous system (CNS) and peripheral nervous system (PNS).
CNS comprises the brain and spinal cord.
PNS consists of nerves connecting body parts to the spinal cord.
Somatic nerves control voluntary actions (like moving muscles).
Autonomic nerves control involuntary processes (like heart rate and digestion).
The autonomic system has two divisions: sympathetic (fight-or-flight) and parasympathetic (rest-and-digest).

The cerebrum is the largest part of the brain, responsible for complex functions like thinking, memory, and sensory processing.
It's divided into four lobes: frontal, parietal, temporal, and occipital. Each lobe has specific roles.
The cerebellum is responsible for balance, coordination, and muscle memory.
The brain stem connects the brain to the spinal cord and controls vital functions like breathing, heart rate, and blood flow.
The spinal cord carries signals between the brain and the body, acting as an information highway.

Afferent nerves carry sensory information to the CNS.
Sensory neurons receive information from the body and send it to the brain or spinal cord. Visceral sensory neurons transmit information from internal organs, including blood pressure, oxygen levels, and stomach content.
Efferent nerves carry instructions from the CNS to the body.
Motor neurons in the somatic system control voluntary movements.
Autonomic neurons control involuntary actions like heart rate, gland secretions, and digestion.

Reflexes are rapid, involuntary responses to stimuli.
The CNS isn't always involved in a reflex—the response occurs quickly because the signal gets processed in the PNS before going to the brain.
Examples include withdrawing a hand from a hot stove.
This process highlights the interaction between the CNS and PNS, along with different parts of the peripheral nervous system.

Thalamus - directs sensory information to appropriate brain regions.
Hypothalamus - regulates hunger, thirst, and body temperature.
Corpus Callosum - connects the brain hemispheres, allowing for communication between the two sides.
Meninges are protective layers of tissue surrounding the brain and spinal cord.
Cerebrospinal fluid (CSF) cushions the CNS and protects from toxins.

Brain size doesn't definitively indicate intelligence.
There is ongoing scientific investigation into the concept of hemisphere dominance: the idea that one side of the brain (right or left) may be more active depending on the task.
Left-hemisphere usually associated with logic and language, and right-hemisphere with creative thinking, emotions, and artistic abilities.