UNIT 2 – Maintaining the Internal Environment (QCE Biology)

Homeostasis

The role of homeostasis is to keep the system the same, at optimum levels from the organism to survive.

Stimulus Response Model

External stimuli triggering a response in the nervous system.

Negative Feedback

The hallmark of a negative feedback loop is that it counteracts a change, bringing the value of a parameter—such as temperature or blood sugar—back towards it set point.

Positive Feedback

Reinforces a change… such as with contractions in childbirth, they disrupt the normal ‘bodily flow’ and continue.

Stimulus

A stimulus is a detectable change in the internal or external environment that evokes a response in an organism. It can be a physical or chemical signal that triggers a biological reaction.

Detection

the process of identifying and responding to stimuli through sensory receptors and neural pathways.

Receptors

Sensory cells or organs that detect specific stimuli (e.g., thermoreceptors for temperature, chemoreceptors for chemical changes).

Control Centre

Processes the information and determines the appropriate response (e.g., hypothalamus in the brain).

Effectors

Muscles, organs, or glands that carry out a response (e.g., sweat glands, muscles).

Chemoreceptors use ____ stimulus

Chemical Substances

Thermoreceptors use ____ stimulus

Changes in temperature

Mechanoreceptors use ____ stimulus

Mechanical forces such as pressure, vibration, and stretch.

Photoreceptors use ____ stimulus

Light Stimulus (usually in retinas)

Nociceptors use ____ stimulus

Pain stimulus

Effectors are

Muscles or glands.

How can stimulus effect Muscles?

Spasm and contraction

How can stimulus effect Glands?

Secrete hormones and fluids.

Metabolism

Metabolism is the conversion of molecules (namely food) into energy through enzyme controlled chemical reactions.

Anabolic

‘Forms’/sythesises smaller molecules into larger more complex molecules.

Catabolic

Breaks down larger and more complex molecules

Dendrites

Dendrites are branch-like structures on a neuron that receive signals from other neurons and transmit them to the cell body.

Neuron Cell Body (Soma)

contains the nucleus and organelles, responsible for maintaining the cell's functions and supporting neuronal activity.

Axon

A long, slender projection of a nerve cell that conducts electrical impulses away from the cell body to other cells.

Myelin Sheath

Insulating layer around nerve fibers that speeds up electrical impulses. Produced by Schwann cells in the peripheral nervous system.

Nodes of Ranvier

The nodes of Ranvier are gaps in the myelin sheath along the axon of a neuron. They help speed up the transmission of electrical impulses.

Axon Terminal

The end of an axon where neurotransmitters are released to communicate with other neurons or muscle cells.

Synapse

A junction between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter.

Peripheral Nervous Sytem

The nervous system outside of the brain and spinal cord. Such as the nerves themselves.

Central Nervous System

The brain and spinal cord. The centre of integration and control.

Sensory Neurons

Sensory neurons transmit sensory information from the body to the central nervous system. They detect stimuli such as touch, temperature, and pain.

Motor Neurons

Neurons that carry signals from the brain and spinal cord to muscles, enabling movement and coordination. They ‘engage’ in subconcious movement (in a way)

3 parts of the nervous system?

Brain, Spinal cord and nerves

What systems work together to maintain homeostasis?

Nervous and Endocrine system.

Antigens

Any substance that provides an immune response.

Non-self antigens

Foreign bodies that enter the body (such as bacteria or viruses).

What do non-self-antigens introduce?

Foreign chemicals (through surface of pathogen) and often produce toxins.

Self-antigens

An organisms own cells that trigger an immune response. Self tolerance usually regulates this (if not, its an autoimmune disorder)

Innate Immune System

The 1st and 2nd immune response. These are non-specific.

What are the three types of innate immune phagocytes?

Macrophages, Neutrophil, Dendritic

Phagocytes

These are a type of immune cell that play a crucial role in the body's defense system. They engulf and digest foreign particles, bacteria, and dead or dying cells through a process known as phagocytosis.

Macrophage

Recruits other immune cells to the infection site.

Neutrophil

Releases Cytokines (they amplify the immune response) and recruit other immune cells to the infection site.

The adaptive immune system

The ‘final’ set of defence which provides specified defences for a given non-self antigen, such as through the secretion of chemicals