Week 1: Health and Homeostasis Flashcards
what is homeostasis?
maintenance of a relatively stable/constant internal environment despite changes in the external environment. This contains a state of consistency and ensures viability.
what is the importance of tolerance limits on homeostasis?
the body and its cells require a specific concentration of substances and elements (ions, salts, pH, temp, etc) which is fixed in a narrow limit. if limits are not maintained and these factors have exceeded or below the limit, this causes molecular, cellular or system dysfunction.
what are the control systems which maintain homeostasis in the body?
nervous system and endocrine system
what are some differences between endocrine and nervous system
ENDOCRINE SYSTEM:
1. **type of messenger = chemical messenger –> endocrine glands/cells secrete hormones upon detecting stimuli.
2. transport of message = **(hormone) via bloodstream and act on target cells through receptors on/in target cell.
**3. speed of response = **produces slower responses. Hormones take time to be synthesized, released, and transported through the bloodstream
4. Duration of response = long-lasting. Hormones can remain in the bloodstream for an extended period, leading to sustained effects on target cells and tissues.
**5. specificty of message = **although hormones are only detected by complementary receptors, it is spread around the whole body via the bloodstream.
NERVOUS SYSTEM:
**1. type of messenger = **electrochemical emssage –> neurons transmit an electrical message (action potential) via axons and a chemical message (neurotransmitters) at axon terminal and synapse.
2. transport of message = uses electrical impulses to transmit signals. Relies on neurons, which transmit information through electrical and chemical signals across synapses.
3. speed of response = rapid responses. Nerve impulses can travel at high speeds, allowing for quick reflex actions and immediate reactions to stimuli.
**4. duration of response = **signals are usually short-lived. Once the nerve impulses cease, the effects diminish quickly.
5. specificity of the message = the neural messages have hihs specificity as it targets a specifc site or organ.
similarities between nervous and endocrine system
- both regulate body systems and maintain homeostasis agains external stimuli.
- both rely on chemical messengers to transmit messages
- NS = neurotransmitters
- ES = hormones - feedback mechanisms = both use negative and positive feedback mechanisms
- receptors = both utilise receptors to increase specificity of the message to ensure it impacts only effectors it is meant to.
- adaptation to stress = Contribute to the body’s response to stress. fight or flight response (NS = taking hand off the stove; ES = adrenaline released while sitting a test).
what is a negative feedback loop
- output or response of a system inhibits or reverses the initial stimulus or input, thereby maintaining stability and homeostasis.
- It is a self-regulating process that helps to maintain balance and prevent excessive fluctuations in a system.
what is positive feedback loop
- the response/output increases/enhances the initial stimulus, resulting in a greater/amplified response.
- This feedback loop creates a self-reinforcing cycle that pushes the system towards an extreme or new state (drives system away from inital state).
- in most cases, once the purpose is complete, countersignals are released –> suppressing the amplification.
what are the 3 types of negative feedback
- restoration of homeostasis = quickly work to restore homeostasis but affect may take longer to achieve. e.g. control of calcium and blood pressure.
- receptor feedback loops = multiple signalling cascades as hormones trigger more hormones e.g. metabolic homeostasis and temp. control.
- antagonistic loops = 2 oppostive effects that woek together to achieve homeostasis. e.g. glucose homeostasis using insulin and glucagon.
examples of positive and negative feedback mechanisms
negative feedback:
- blood glucose regulation (antagonistic loop)
- thermoregulation
- blood pressure regulation
- osmoregulation
positive feedback
- breast feeding
- blood clotting processes
- uterine contractions
what is afferent and efferent?
- afferent = bring the information from different parts of the body to the central nervous system (CNS) (from PNS —> CNS)
- efferent = carry nerve impulses away from the central nervous system (CNS) (from CNS –> PNS)
what is dual regulation in homeostasis
when a body system is regulated via the nervous and endocrine system working together for a negative or postive feedback processess.
control of blood pressure
EXAMPLE OF NEGATIVE FEEDBACK LOOP
**1. stimulus = **decrease in BP
**2. receptors = **detected by receptors in the carotid or aortic artery
**3. control centre ** = sends signal to brain
**4. effector ** = information send along efferent pathway to heart and blood vessles.
**5. Response = ** vasoconstriction and increased heart rate which increases the blood pressure (BP) to ideal/normal state :. reach homeostasis.
Regulation of Blood clotting
EXAMPLE OF POSITIVE FEEDBACK
1. stimulus = tear in vessel wall
**2. ** the tear/damage detected by receptors of adjacent cells.
**3. ** stimulates platelet aggregation
**4. ** Platelets release chemicals to attract other platelets.
5. Newly attracted chemicals further release chemical to attract other platelets.
6. Clot formation cmplete and other inhibitory processes prevent further aggregation.
Oxytocin and uterine contraction
EXAMPLE OF POSITIIVE FEEDBACK
1. stimulus = the pressure of the baby pushing againts the uterine wall/birthing canal.
2. Oxytocin released from posterior pituitary
3. oxytocin stimulates contraction of the uterine muscles during parturation.
4. contractions stimulate stretch receptors inside the uterus and birth canal
5. signals brain to continue process until the baby is born.
6. countersignals are released to suppress the release of oxytocin and inhibit the contraction of uterine muscles.
Describe an example of homeostatic mechanism and the consequences of system dysfunction.
- body works to maintain pH of 7.35-7.45
- this is done by increasing and decreasing breathing rate via a negatove feedbakc loop which expels CO2 from bloodstream at varying rates.
- any vairation away from normal range of pH results in acidosis or alkalosis –> cells cannot survuve for more than few hours, hence causing body systems to shut down, thus, body cannot function accordingly.
