5.1.1 - Communication And Homeostasis Flashcards
What is the purpose of an effective communication system in organisms?
To ensure an organism is able to function effectively.
What is a stimulus in the context of cell signaling?
An environmental change like temperature.
What is the response in the context of a stimulus?
A change in behaviour or physiology.
What is the difference between external and internal stimuli?
External stimuli are environmental changes; internal stimuli are changes to tissue fluid and blood composition.
What are the components of the coordinating communication system?
- Stimulus
- Receptor
- Effector
- Response
What is the standard response pathway for homeostasis?
Stimulus → Receptor → Communication pathway → Effector → Response.
Where are sensory receptors typically found?
On surfaces like the skin and in the brain.
What do sensory receptors do when they detect a change?
They send a signal to an effector.
What are the two main communication systems in the body?
- Neural system
- Hormonal system
What is homeostasis?
The maintenance of a constant internal environment despite changes in external and internal factors.
List six examples of homeostatic control systems.
- Blood glucose concentration
- Body temperature
- Blood pressure
- Water potential of the blood
- Blood salt concentration
*Carbon dioxide concentration
What is negative feedback?
A mechanism used to reverse changes to maintain a constant environment.
Fill in the blank: The closer the conditions get to optimum, the receptors detect the reduction in stimulus so they reduce the _______.
input that is sent to the coordination centre.
True or False: The effector causes a change back to the optimum conditions.(negative feedback)
True.
What role do effectors play in the communication system?
They match a response to the stimulus (muscle or gland).
What are the main steps of negative feedback?
- Conditions in the body change from a set point
- The change is detected by receptors in/out of the body
- Once the receptor has received a signal a corrective mechanism, is activated
- Conditions return to a set point
- Corrective mechanism is switched off
What is an example of cell signaling between adjacent cells?
The nervous system secreting neurotransmitters which send signals to other nerve cells or muscle cells
What is an example of cell signalling between distant cells?
The hormonal system releases hormones which travel through the blood and are detected by cell surface receptors
What is the difference between receptors and effectors?
- Receptors detect specific stimuli, like pressure change
- Effectors are cells that bring about a response to a stimulus, like muscles contracting
What is a positive feedback mechanism?
A process that amplifies or increases the effects of a stimulus.
True or False: Positive feedback mechanisms are commonly involved in homeostasis.
False
It is not involved as it does not keep the internal environment constant
Fill in the blank: In a positive feedback loop, the output enhances the __________.
initial stimulus
Which of the following is an example of a positive feedback mechanism? A) Blood sugar regulation B) Childbirth C) Body temperature control
B) Childbirth
Short answer: Describe one situation in which a positive feedback mechanism is beneficial.
During childbirth, the release of oxytocin increases contractions, facilitating delivery.
Fill in the blank: Positive feedback is useful to ______________ something, eg. blood clots after injuries
Rapidly activate
What is the effect of increased temperature on molecular activity?
Increased temperature provides more kinetic energy, leading to faster molecular movement and increased collision rates.
This results in a faster rate of chemical reactions.
What happens to enzyme-controlled reactions at higher temperatures?
Enzymes can denature due to increased temperature, disrupting the complementarity between the substrate and active site.
Denaturation affects the enzyme’s functionality.
Define ectotherms.
Organisms that rely on external sources to maintain body temperature.
Examples include fish, reptiles, and amphibians.
Define endotherms.
Organisms that use heat from metabolic reactions to maintain body temperature.
Examples include mammals and birds.
How do ectotherms generally regulate their temperature?
Through behavioral means such as:
* Moving out of direct sunlight
* Going underground
* Orientating their body away from the sun
* Moving into the sun
* Lying on warm surfaces
* Orientating their body towards the sun
These behaviors help maintain optimal body temperatures.
How do endotherms regulate their body temperature?
Through both behavioral and physiological mechanisms.
They do not rely on external heat sources.
What are the three mechanisms endotherms do to reduce body temperature?
- Sweating
- Hairs lie flat
- Vasodilation
What mechanisms do endotherms use to increase body temperature?
- Shivering
- Much less sweat
- Hairs stand up
- Vasoconstriction
- Hormones
How does sweating reduce body temperature?
- More sweat is secreted from the sweat glands
- The water in the sweat evaporates from the surface of the skin to take heat from the body
- This cools the skin
How does hairs laying flat reduce body temperature?
- Erect pili muscles relax causing the hairs to lie flat
- This traps less air, so the skin is less insulated
- Heat can be lost more easily
How does vasodilation reduce body temperature?
- Arterioles near the skin surface dilate
- This means more blood flows through the capillaries in the dermis
- This cause more heat to be lost from the skin by radiation lowering the temperature
How does shivering increase body temperature?
- When it is cold the muscles contract in spasms
- This makes the body shiver producing more heat from respiration
How does sweating less increase body temperature?
- Less sweat is screamed from the gland which reduces heat loss
How does hairs standing up increase body temperature?
- Erector pili muscles contract when it’s cold
- This causes the hairs to stand up and trap more hair
- This prevents heat loss
Fill in the blanks: Vasoconstriction is when _______ near the surface constrict, so less blood flows through the _________ in the dermis.
- Arterioles
- Cappilaries
Fill in the blanks: The body releases ___________ and ___________ (hormones) to increase metabolism so less heat is produced
- Adrenaline
- Thyroxine
What part of the brain is primarily responsible for regulating body temperature?
The hypothalamus.
True or False: The hypothalamus can induce sweating to help cool the body.
True.
Fill in the blank: The hypothalamus maintains body temperature by balancing heat production and _____ .
heat loss.
Which physiological response is initiated by the hypothalamus when body temperature rises?
Vasodilation and sweating.
Multiple Choice: What is the set point temperature for the human body that the hypothalamus typically maintains? A) 36.5°C B) 37.0°C C) 38.5°C D) 39.0°C
B) 37.0°C.
What are the receptors in the hypothalamus?
Thermoreceptors
What happens after the thermoreceptros detect a change in temperature?
- Send an impulse along the sensory neurones to the hypothalamus
- This sends an impulse along the motor neurones to the effectors
How do plants increase their chance of survival?
Responding to changes in the environment
How do animals increase their chance of survival?
By responding to their external environment (avoiding harmful environments) and responding to their internal environment changing so that their conditions are optimal for their metabolism
