Chemical and Nervous Control in Humans

Chemical and Nervous Control in Humans

• Humans experience constant internal and external changes, including blood sugar levels, temperature, and thirst, as well as a sleep-wake cycle.
• Learning objectives for this topic include determining the function of the nervous system, comparing and contrasting nervous system divisions, explaining action potential generation and propagation, and understanding brain structures and functions.

Functions of the Nervous System

• The nervous system receives sensory input, processes this information, controls muscles and glands, and maintains homeostasis and mental activity.

Divisions of the Nervous System

• The central nervous system (CNS) comprises the brain and spinal cord.
• The peripheral nervous system (PNS) consists of nerves and ganglia.
• The nervous system coordinates body functions using both electrical impulses and chemical messengers (neurotransmitters).

Autonomic Nervous System

• The autonomic division of the peripheral nervous system controls involuntary body functions.
• It has two branches: sympathetic and parasympathetic.

Sympathetic Nervous System

• This division is involved in "fight-or-flight" responses.
• It's associated with things like dilating bronchioles, increasing heartbeat, and releasing adrenaline.

Parasympathetic Nervous System

• This branch is associated with the "rest-and-digest" functions.
  • It's involved in constricting bronchioles, slowing heartbeat, increasing stomach secretion, and increasing motility of internal organs.

Action Potential

• An action potential is an all-or-none response triggered when a local potential reaches a threshold.
• The process involves depolarization (voltage changes), repolarization, and a brief hyperpolarization phase before returning to resting membrane potential.
• The entire action potential usually takes 1-2 milliseconds to complete.

Brain Regions

• The brain has various regions with specialized functions:
  • The frontal lobe controls voluntary motor functions, motivation, aggression, and mood.
  • The parietal lobe processes sensory information such as touch, pain, temperature, and balance.
  • The occipital lobe is responsible for visual input.
  • The temporal lobe is critical for olfactory (smell) and auditory (hearing) senses and memory. Its inferior portion is called the psychic cortex, related to abstract thought.