9H Science: Nervous System, Endocrine System, and Homeostasis

Comprehensive vocabulary flashcards covering the human nervous system, endocrine system, neurotransmitters, brain structures, and homeostatic mechanisms as discussed in the Year 9 Science lectures.

Stimulus

A detectable change in the internal or external environment of an organism.

Internal Stimuli

Changes originating from inside an organism, such as a reduction in blood glucose or an increase in internal temperature (fever).

Photoreceptor

A sensory receptor located in the eye that responds to light.

Mechanoreceptor

A sensory receptor located in the ear that responds to sound.

Chemoreceptor

A sensory receptor located in the tongue and nose that responds to chemicals.

Thermoreceptor

A sensory receptor located in the skin that responds to temperature.

Sympathetic Nervous System

Part of the nervous system activated during danger, stress, and excitement, causing enlarged pupils and faster heartbeat.

Parasympathetic Nervous System

Part of the nervous system activated when relaxed, allowing for slower heartbeat and continued digestion.

Stimulus-Response Model

A pathway where changes (stimuli) are detected by receptors and communicated to effectors to bring about a correction.

Effectors

Muscles or glands that receive messages from the central nervous system to respond in a particular way.

Reflex

An involuntary and nearly instantaneous movement where the message travels to the spinal cord instead of the brain for a faster response.

Neuron

The most basic component of the nervous system; a specialised cell that receives and transmits information using electrical and chemical impulses.

Dendrites

Structures of a neuron specialised to receive signals from neighbouring neurons and carry them back to the cell body.

Axon

A thin, long structure in a neuron that transmits signals from the cell body to the axon terminal.

Myelin Sheath

A covering that insulates the axon to help speed up neural impulses.

Synapse

The gap between neurons where electrical signals are converted into chemical releases to travel to the next neuron.

Neurotransmitter

Chemicals stored in vesicles that are released from one neuron to receptors on another neuron.

Glutamate

The main excitatory neurotransmitter involved in learning and memory; excessive amounts can cause excitotoxicity.

GABA

The main inhibitory neurotransmitter that helps calm neural activity; low levels contribute to anxiety and tremors.

Serotonin

A neurotransmitter that helps regulate mood, sleep, appetite, and digestion; low levels are associated with depression.

Dopamine

A neurotransmitter involved in reward, motivation, and movement; low levels are associated with Parkinson's disease.

Acetlycholine

A neurotransmitter important for muscle contraction, learning, attention, and memory.

Norepinephrine

A neurotransmitter that helps regulate alertness, attention, arousal, and stress responses.

Endocrine System

A collection of glands that secrete hormones directly into the bloodstream.

Hormones

Chemical messengers secreted by glands that travel through the blood to reach specific target cells.

Target Cells

Cells that possess specific receptors that match a particular hormone like a lock-and-key.

Insulin

A hormone produced by the pancreas that targets the liver and most cells to lower blood glucose levels.

Glucagon

A hormone produced by the pancreas that targets the liver to raise blood glucose levels.

Homeostasis

The maintenance of a constant internal environment, including variables like body temperature and metabolic waste such as $CO_2$.

Negative Feedback

A mechanism where the effector responds to remove or oppose the original stimulus to bring conditions back to normal.

Positive Feedback

A mechanism where the effector responds to enhance or amplify the original stimulus, causing the system to deviate further from the original level.

Multiple Sclerosis

A condition caused by the immune system attacking and damaging the myelin sheath, which results in the loss of electrical signals.

Motor Neuron Disease (MND)

A condition where motor neurons weaken and lose function, eventually affecting the ability to talk and breathe.

Alzheimer’s Disease

A progressive disease characterized by damage to neurons in the brain, possibly due to plaque development, which affects memory and reasoning.

Cerebral Cortex

The brain's ultimate control and information processing centre, divided into four main lobes.

Corpus Collosum

The structure that ensures both hemispheres of the brain are connected and can communicate.

Cerebellum

The part of the brain responsible for voluntary movement and balance.

Hypothalamus

A brain region that maintains homeostasis, influences the Autonomic Nervous System, and regulates hunger and thirst.

Hippocampus

Part of the limbic system involved in memory processing and maintenance activities.

Amygdala

Two almond-shaped neural clusters linked to emotion and fear.

Frontal Lobe

The lobe involved in executive functions, speaking, muscle movements, making plans, and judgment.

Parietal Lobe

The lobe that receives and processes sensory information.

Occipital Lobe

The lobe that receives and processes visual information.

Temporal Lobe

The lobe that receives and processes auditory information.