Responding to Stimuli
what do we call a change inside or outside the body that the body notices and reacts to?
a stimulus
define homeostasis.
the process of keeping the body's internal environment stable, even when external conditions change.
what type of message does the nervous system use to send signals?
electrical impulses along neurons
what is degenerative disease?
a disease where organs or tissues deteriorate and lose function over time
which type of feedback loops reverses a change to restore balance?
negative feedback
low hydration > you feel thirsty
low oxygen > you breathe faster
what is the role of a receptor?
to detect changes inside or outside the body and send messages to the command centre
what type of message does the endocrine system use to send signals?
chemical messengers called hormones in the bloodstream
what substance does the immune system attack in multiple sclerosis?
myelin around nerve axons
which type of feedback loop amplifies a change until a job is done?
positive feedback
name the parts of the stimulus-response model in order
stimulus > receptor > command centre > effector > response
what is a "set point" in a feedback loop?
the ideal value for a variable (e.g., body temperature ~ 37 degrees)
which system is faster, and which system has longer-lasting effects?
nervous system is faster; endocrine system has longer-lasting effectors.
what chemical is lacking in Parkinson's disease and why is it important?
blood sugar rises > chemoreceptors sense increased BGL > pancreas releases insulin > glucose enters the cell > blood sugar returns to normal
photoreceptors in the eyes detect light. what type of stimulus is this, and what is the response?
external stimulus; pupils constrict in bright light or dilate in dim light.
which type of feedback loop helps maintain homeostasis most of the time?
negative feedback loops
give one similarity and one different between the nervous and endocrine systems
both help maintain homeostasis; nervous system is fast/electrical, endocrine system is slow/chemical.
list two common symptoms of multiple sclerosis and two of Parkinson's disease.
MS: muscle weakness, fatigue, trouble walking
Parkinson's: tremors, slow/clumsy movements
what part of the feedback loop fails in type 1 diabetes, and what are two possible long-term effects?
insulin production fails; effects include kidney damage, vision loss, nerve damage, or heart disease.
explain how the body uses receptors, command centres, and effectors when you touch a hot object.
thermoreceptors/mechanoreceptors detect heat (stimulus), send a message to the brain/spinal cord (command centre), which signals muscles (effectors) to contract and pull the hand away (response)
explain the difference between an effector and a command centre.
the command centre (often the brain) decides how to respond; effectors (muscles or glands) carry out the response.
explain how the nervous system would respond to standing on a LEGO brick and how the endocrine systems would respond to being dehydrated.
LEGO brick = nervous system causes fast reflex to move foot; dehydration = endocrine system releases ADH to conserve water in kidneys.
explain one factor that may increase the risk of multiple sclerosis and one treatment strategy for Parkinson's
MS risk = certain genes or viral infections
Parkinson's treatment = medications that increase dopamine or physiotherapy
compare what happens to the body during hyperthermia vs. hypothermia when thermoregulation fails.
hypothermia = body cools too much > slowed body functions, organ failure, death if untreated.
hyperthermia = body overheats > dizziness, heat stroke, organ failure.