Homeostasis and Response: Principles of Homeostasis

Homeostasis and Response

Big Idea and Topic

  • Big Idea: Homeostasis and Response (B5)
  • Topic: Homeostasis

Lesson Sequence

  • L1: The principles of Homeostasis
  • L2: The structure and function of the human nervous system
  • L3: Reflex actions
  • L4+L5: Reaction time practical

Key Concepts

  • Homeostasis
  • Receptors
  • Stimuli
  • Coordination centers
  • Effectors
  • Neurons
  • Nerves
  • Central nervous system
  • Sensory neurons
  • Motor neurons
  • Reflex arc
  • Cerebral cortex
  • Cerebellum
  • Medulla
  • Suspensory ligaments
  • Ciliary muscles
  • Myopia
  • Hyperopia

Key Question

  • Why are reflex actions so important for survival?
  • 4. 10 HOMEOSTASIS
  • 4. 5. 1 LINK TO SPECIFICATION (page 41)

Core Learning

  • Students will study the principles of homeostasis and should be able to give some examples and outline the control system involved.
  • Students will learn about the structure and function of the human nervous system.
  • Students should be able to describe a reflex arc, with detail of synaptic transmission.
  • Students will learn that receptors detect a change in a stimulus and not the stimulus itself.
  • They should be able to describe an electrical impulse accurately.
  • Students will learn about different areas of the brain and their relative functions.
  • There is a higher-tier topic of investigating the brain and the treatment of brain damage.
  • Finally, students will learn the structure and function of the human eye and the process of accommodation.
  • They should understand that the ciliary muscles contract in accommodation.
  • These students should be able to describe common defects of the eye including myopia, hyperopia, and the role of new technology in the treatment of these conditions

Prior Learning

  • In Year 10 Students studied:
    • Enzyme action in B3 Organisation and the digestive system;
    • The function of cells in B1 Cell structure and transport

Future Learning

  • Students will learn about the second control system for homeostasis- the endocrine system.

Definition of Homeostasis

  • Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
  • Homeostasis maintains optimal conditions for enzyme action and all cell functions.

Examples of Internal Conditions Controlled in Humans

  • Blood glucose concentration
  • Body temperature
  • Water levels

Types of Responses

  • These automatic control systems may involve nervous responses or chemical responses.

Components of All Control Systems

  • Cells called receptors, which detect stimuli (changes in the environment)
  • Coordination centers (such as the brain, spinal cord, and pancreas) that receive and process information from receptors
  • Effectors, muscles, or glands, which bring about responses which restore optimum levels.

Last Lesson/Term/Year Retrieval Questions

  • Name the chambers of the heart: Atria and ventricles
  • Name the blood vessel that carries blood away from the heart to the lungs: Pulmonary artery
  • What is the job of the aorta: Carries blood away from the heart to the body
  • Describe the action/role of a stent
    • Build-up of fatty material narrows arteries and reduces blood flow
    • A stent is a metal mesh placed in an artery to widen it and increase blood flow
    • Stents do not remove the fatty material

Homework

  • Complete worksheet on homeostasis and/or exam questions

Learning Objectives

  • Define homeostasis and state examples
  • Describe the pathway of a control system as receptor, coordination center, effector
  • Explain why internal conditions need to be maintained

Key Questions

  • Why do we sweat?
  • Why do we shiver?
  • Why does our urine change color?
  • What do these processes have in common?

Examples of Homeostatic Processes

  • Sweating (Thermoregulation – Temperature control)
  • Changing how much water we absorb (Osmoregulation – Water control)
  • Shivering (Thermoregulation)

What is Controlled by Homeostasis

  • Glucose
  • Temperature
  • Water

Control System Pathway

  • Stimulus → Receptor → Coordination center → Effector → Response

Examples of Stimuli and Receptors

  • Touch: Stimulus = pressure, Receptor = pressure receptors in the skin
  • Sight: Stimulus = light, Receptor = light-sensitive cells in the retina of the eye
  • Smell: Stimulus = chemicals, Receptor = olfactory cells lining the nose
  • Taste: Stimulus = chemicals, Receptor = taste buds in the tongue, palate, and epiglottis
  • Sound: Stimulus = vibrations in the air, Receptors = in the inner ear

Coordination Centers

  • Brain
  • Spinal cord
  • Pancreas

Effectors

  • Muscles (contract/relax to move a body part)
  • Glands (produce and release substances e.g. hormones, saliva, sweat)

Putting the Control System in Order

  1. Stimulus (e.g., heat)
  2. Receptor
  3. Coordination center
  4. Effector (e.g., shivering)
  5. Response (back to optimum)

Examples of Stimulus and Effector

  • Touching a hot stove: Stimulus = Heat, Effector = Hand muscles
  • Man going into a hot room: Stimulus = High temperature, Effector = Sweat gland
  • Light being turned on: Stimulus = Bright light, Response = Eyes will close, hands cover eyes
  • Plants respond to light and gravity

Importance of Controlling Internal Conditions

  • To maintain optimum condition for enzymes and cells to work

What Happens If Internal Conditions Are Not Controlled

  • Enzymes become denatured (the shape of the active site changes)

Why Fever Makes You Feel Unwell

  • Enzymes are needed for all of the body’s processes. If the enzymes are not working efficiently and becoming denatured, then the body’s reactions e.g. respiration releasing energy, will not be completed at a suitable rate.

Exam-Style Questions

  • Define the term homeostasis.
  • Describe the function of receptors in the skin.
  • Give one reason why it is important to control body temperature.