Year 9 Biology Revision: Nervous & Endocrine Systems

Basic Unit of the Nervous System: Neurons are the fundamental cells that make up the nervous system. They transmit signals throughout the body in response to stimuli.
Primary Function of the Nervous System: The nervous system processes information from both internal and external environments and coordinates appropriate responses.
Labeling Exercise: Familiarize oneself with diagrams of a neuron and components of the nervous system by using given terms.

Definition: A reflex arc is the nerve pathway involved in a reflex action.
Sequence of a Reflex Arc:
1. Stimulus: Any change that can evoke a response (e.g., touching a hot surface).
2. Sensory Neuron: Transmits the sensory information to the spinal cord.
3. Spinal Cord (Interneuron): Processes the incoming signal and sends out the response.
4. Motor Neuron: Carries the response signal to the muscles.
5. Response: The action taken (e.g., withdrawing your hand).
Key Feature: Unlike involuntary actions (e.g., heartbeat, digestion), reflex actions bypass the brain for quicker reactions to protect the body.
Examples of Reflex Actions:
- Blinking
- Pupil dilation in response to light
- Knee-jerk reaction

Hormones: Chemical messengers responsible for regulating various body functions (e.g., insulin helps control blood sugar levels).
Gland: An organ that produces and secretes hormones. Examples include:
- Pineal Gland
- Pituitary Gland
- Thyroid Gland
- Adrenal Glands
- Pancreas
- Ovaries
- Testes
Hormonal Transport: Hormones travel through the bloodstream as opposed to signals in the nervous system which travel through neurons.

Characteristics Comparison:
- Type of Message:
- Nervous System: Electrical
- Endocrine System: Chemical
- Speed of Message:
- Nervous System: Fast
- Endocrine System: Slow
- Length of Responses:
- Nervous System: Short Lasting
- Endocrine System: Long Lasting
- Spread of Effect:
- Nervous System: Local
- Endocrine System: Widespread
Homeostasis: Both systems work together to maintain a stable internal environment despite external changes.

Definition: Homeostasis is the ability of the body to maintain a stable internal environment despite changes in the external environment.
Brain Regulation: The hypothalamus is a critical part of the brain responsible for regulating homeostasis.
Feedback Mechanisms:
- Negative Feedback: A process that counteracts changes, e.g., if blood sugar rises, insulin lowers it.
- Positive Feedback: Amplifies changes, e.g., oxytocin release during childbirth increasing contractions.

Negative vs Positive Feedback:
- Negative Feedback:
- Water balance (ADH regulates hydration).
- Oxygen levels in blood (change in breathing rate).
- Blood pressure control (dilation and constriction of blood vessels).
- Positive Feedback:
- Childbirth (increased contractions).

Infectious Diseases: Caused by pathogens (bacteria, viruses, fungi, parasites) that can be transmitted.
- Examples:
- Tuberculosis (Bacteria)
- Influenza (Virus)
Non-Infectious Diseases: Result from genetic factors, lifestyle, or environmental conditions; cannot be transmitted.
- Examples:
- Diabetes
- Cancer
Pathogen: A microorganism that causes disease, including bacteria, viruses, fungi, and parasites.

Prevention Methods Against Diseases:
- Regular hand washing
- Proper food preparation
- Frequent disinfection of surfaces
- Vaccinations
- Use of PPE (masks, gloves)
- Maintaining social distance during outbreaks
- Proper covering when coughing/sneezing
Bacteria vs. Viruses Comparison:
- Bacteria: Living organisms, can reproduce independently, treated with antibiotics.
- Viruses: Non-living, require a host to replicate, treated with antiviral medications.