Homeostasis and Feedback Mechanisms

Homeostasis

• Homeostasis is the process where the body maintains a stable internal environment.
• Key organ systems involved include the nervous system, endocrine system, muscular system, hair, nails, skin, reproductive system, and excretory system (kidneys).
• Circulation plays a vital role by transporting nutrients, waste, and hormones, regulating pH through buffering systems, and the maintaining homeostasis.

Homeostatic Mechanisms

• Homeostatic mechanisms involve three key elements:
  • Sensor: detects changes in the internal or external environment.
  • Integrator: processes information from sensors, determines the response, and acts as the control center.
  • Effector: carries out the response to restore balance.

Feedback Mechanisms

• Negative Feedback: Reverses a change, returning conditions to their original state (e.g., maintaining body temperature, blood pH, returning to resting heart rate after exercise).
• Positive Feedback: Amplifies a change, taking the body further from its normal condition (e.g., labor and childbirth, hormone oxytocin).

Body Temperature Regulation

• The hypothalamus acts as a thermostat, regulating body temperature.
• When cold, blood vessels constrict, skeletal muscles contract (shivering), and hair stands on end to conserve heat.
• When hot, blood vessels dilate, sweat glands activate, cooling the body.

Body Temperature Classification

• Homeotherms: Maintain a stable body temperature independent of external environment (e.g., birds, humans).
• Endotherms: Generate internal heat through metabolic processes (typically homeothermic).
• Ectotherms: Rely on external heat sources, and their body temperature fluctuates (e.g., reptiles, amphibians).

Nervous System

• The nervous system is responsible to maintain homeostasis via quick, short-lived responses.
• The Central Nervous System (CNS) consists of the brain and spinal cord.
• The Peripheral Nervous System (PNS) connects the CNS to the rest of the body.

Types of Neurons

• Sensory Neurons (Afferent): Transmit information from receptors (e.g., skin, eyes) to the CNS.
• Interneurons (Association): Connect sensory neurons to motor neurons within the CNS.
• Motor Neurons (Efferent): Transmit signals from the CNS to effectors (e.g., muscles, glands).

Neuron Structure

• Dendrites: Branch-like structures receiving signals from other neurons.
• Cell Body (Soma): Contains the nucleus, processing incoming signals.
• Axon: A long fiber transmitting electrical impulses away from the cell body.
• Myelin Sheath: Insulating layer speeding up signal transmission.
• Axon Terminal: End branches where the neuron communicates with other cells.

Action Potential

• An action potential is a rapid electrical signal traveling along an axon.
• Gated channels, specifically sodium and potassium channels, are involved, triggering a change in voltage across the membrane.
• Sodium channels open initially, followed by potassium channels, resulting in depolarization and repolarization phases, maintaining homeostasis across cell membrane.
• The sodium-potassium pump helps restore the resting potential.

Brain Lobes and Functions

• Cerebrum: Largest part of the brain involved in reasoning, decision-making, voluntary movement, speech, sensory processing (touch, temperature, pain), hearing, memory, language comprehension, and vision.
• Cerebellum: Coordinates balance, posture, and voluntary movements.
• Brainstem: Controls basic life functions (breathing, heart rate).
• Hypothalamus: Regulates homeostasis (e.g., temperature, hunger, thirst).

Reflex Arc

• A reflex arc is a neural pathway responsible for a fast, involuntary response.
• It involves a receptor, sensory neuron, interneuron, motor neuron, and an effector.