Human Body Systems: Nervous System Overview

Study Notes

The nervous system is made up of the central nervous system (CNS) and peripheral nervous system (PNS).
The CNS consists of the brain and spinal cord.
The PNS connects the entire body to the CNS via nerves.
The PNS has two major categories of nerves: somatic nerves and autonomic nerves.
- Somatic nerves control voluntary movements.
- Autonomic nerves control involuntary functions like heart rate, breathing, and digestion.

The brain is divided into four lobes (frontal, parietal, temporal, and occipital).
The cerebrum, a large part of the brain, manages complex functions including thinking, movement, memories, sensory processing, vision, and speech.
The cerebellum is important for balance, muscle coordination, and muscle memory.
The brain stem, made up of the medulla oblongata and pons, controls basic body functions such as breathing, heartbeat, blood flow, and coughing.
The spinal cord is a major pathway of signals between the brain and body.
Meninges are protective layers surrounding the brain and spinal cord, and cerebrospinal fluid (CSF) cushions and nourishes the brain.

Thalamus: Directs incoming sensory messages to appropriate brain areas.
Hypothalamus: Regulates hunger, thirst, and body temperature.
Corpus Callosum: Connects the left and right hemispheres of the cerebrum to allow signal exchange.
There are other parts of the brain, like the amygdala and hippocampus which are not specifically shown in detail here: the images provided focus on structures and functions.

Brain size does not definitively correlate to intelligence.
Other factors, like brain structure and the connections between neurons, play a significant role in cognitive ability.

The right hemisphere controls the left side of the body, and is associated with artistic talents like art and writing, creativity, intuition, and emotions.
The left hemisphere controls the right side of the body, and is related to logic, science, mathematics, and organization.

Reflexes are quick subconscious actions without higher brain processing.
The spinal cord bypasses the brain in reflexes, creating rapid responses, e.g. quickly withdrawing a hand from a hot stove, pain realization following the action.

Afferent nerves: These carry sensory information from the body (like touch, heat, and pain) to the brain. Sensory neurons send this information.
Efferent nerves: These relay messages from the brain to the body's muscles, glands, and organs to elicit a response. Both somatic motor nerves and autonomic nerves fall under this category.

The autonomic nervous system manages involuntary functions—heart rate, digestion, and blood pressure.
It's broken down into the sympathetic ("fight or flight") and parasympathetic ("rest and digest") divisions, which have opposite effects on the body.

The spinal cord carries nerve signals to and from the brain to the rest of the body. This is critical for all bodily functions outside of the brain. It manages reflexes and carries information from the senses.