Biology Chapter: Homeostasis & Nervous System

Homeostasis

• Homeostasis is the body's ability to maintain a stable internal environment despite external changes.
• Examples include body temperature, blood glucose levels, and blood pressure.

Feedback Mechanisms

• Negative Feedback: Counteracts changes to return the body to its normal state.
  • Example: Body temperature regulation
• Positive Feedback: Amplifies changes to achieve a specific outcome.
  • Example: Blood clotting during injury

The Brain

• The brain is a supercomputer responsible for all body functions.
• It controls thoughts, memory, emotions, motor skills, sensory processing, and much more.
• It manages voluntary actions, such as strutting and hugging, and involuntary actions, such as breathing and heartbeat.

Central Nervous System (CNS)

• The CNS is the control center.
• It processes information received from the body and sends instructions back.
• The brain controls higher-level functions.
• The spinal cord relays signals between the brain and the rest of the body, managing reflexes.

Parts of the Brain

• Cerebrum: Responsible for voluntary actions, sensory processing, learning, and memory.
• Cerebellum: Coordinates balance and movement.
• Brainstem: Regulates involuntary functions like breathing and heart rate.

Peripheral Nervous System (PNS)

• The PNS connects the CNS to the rest of the body.
• Somatic Nervous System (SNS): Controls voluntary muscle movements and sensory input.
• Autonomic Nervous System (ANS): Manages involuntary functions.

Subdivisions of the Autonomic Nervous System (ANS)

• Sympathetic Nervous System: Activates the "fight or flight" response during stress.
• Parasympathetic Nervous System: Promotes the "rest and digest" state during relaxation.

Roles of the Nervous System

• Sensory Input: Detects changes in the environment (stimuli).
• Processing Center: The brain and spinal cord interpret and process information.
• Motor Output: Sends signals to effectors (muscles or glands) to correct any imbalances.

Body Temperature Regulation

• Stimulus: Changes in body temperature.
• Sensor: Skin and hypothalamus detect the change.
• Control Center: Hypothalamus processes the signal.
• Effector: Sweat glands, blood vessels, and muscles correct the temperature.

Blood Glucose Regulation

• Stimulus: Changes in blood glucose levels.
• Sensor & Control Center: Pancreas working with the nervous system.
• Effector: Liver and muscle cells regulate glucose levels.

Blood Pressure Regulation

• Stimulus: Changes in blood pressure.
• Sensor: Baroreceptors in blood vessels detect changes.
• Control Center: Medulla oblongata.
• Effector: Heart rate and blood vessel diameter adjust to maintain or restore normal levels.

Importance of Homeostasis

• The nervous system ensures survival and rapid response to internal and external changes.
• Understanding homeostasis highlights the remarkable complexity and efficiency of the body.

Quick Activity

• This section may include a scenario-based activity requiring students to identify stimuli, sensors, control centers, and effectors involved in a given situation.