Lecture 25 Flashcards
What is homeostasis - balance
- a relatively constant internal environment that supports cell functioning and life processes
- human body systems keep each regulated variable withen an original range
Imbalance - loss of homeostasis
- as cells function, they use up nutrients and produce biproducts
- example = during growth, reproduction, exercise, stress and illness
What is regulated variable
A variable for which there is a sensor and a system to ensure the variable is kept withen a normal range, around a set point
What are examples of regulated physiological variables
- core temperature
- plasma gluclose concentration
- plasma calcium concentration
- basal metabolic rate
And many more
Regulated variables, Normal range
The restricted set of variables for a regulated variable, that permits optimal cell functioning
Regulated variable, set point
- the physiological value of any given variable, around which its normal range fluctuates
- each person has a unique set-point for each variable based on genetics and other factors
What is the set point
This is the target value for which the system aims to maintain
What is the normal range
The normal rage is rages that are a range of values that are around the set point
Control system for non physiological example, so if we are thinking about temperture
control system is responsible for regulating the room temperature to keep it within the normal range around the set-point. In this example, the control system consists of a thermostat connected to a heat pump. The thermostat continuously monitors the current room temperature and compares it to the set-point. If the temperature deviates from the set-point, the thermostat sends signals to the heat pump to adjust its operation accordingly. For instance, if the room temperature rises above the set-point, the heat pump activates the cooling function to lower the temperature back to the desired level. Conversely, if the temperature drops below the set-point, the heat pump switches to heating mode to warm up the room.
What is a physiogical example if we are talking about normal range and set point
If we were discussing the regulation of body temperature in a living organism, such as a human, it would be a physiological example because it involves the natural processes that occur within the body to maintain temperature homeostasis.
What is a non-physiological example
On the other hand, the room temperature control scenario is a non-physiological example because it pertains to the regulation of temperature in an artificial environment (a room) using a mechanical system (a thermostat connected to a heat pump). It does not involve biological processes or living organisms.
What is population refernace rage
The set of values for a regulated variable that are considered normal and/or healthy and it tends to be wider than any given individuals normal range
Population refernace range vs individuals normal range
- most indivuals will have a set point that is withen the population refernace range
- remember the normal range fluctuates around the set point for any given variable
And so if the variable was to move outside the normal range this may lead to deasises or symptoms of a disorder
This can even occur if the variable is in the population refernace range
Homeostasis of regulated variables: NEGATIVE FEEDBACK FOR BALALCE
A negative control loop keeps a regulated variable in its normal range around the set point,-
-if the variable was to go up the negative feedback will bring it down
- if the variable was to go down, the negative feedback will bring it up
What is the negative feedback control loop
- sensors : this monitors the variable and directs changes
- control centre - this compares the variables changed value to its set point and it send signals to effectors if correction is required
- effectors - these act to oppose the effect of the stimulus, meaning it corrects the change and restoring the variable to its setpont
Amplification of regulated variables: positive feedback for amplification
Positive feedback control drives the process to completion by amplifying the change to a regulated variable
- if the virile was to go up, positive feedback makes it go up more
- if the variable goes down, potive feedback makes it go down more
Positive feedback amplification loop
- sensors: monitor the variable and detect changes
- control centre: send signals to the effectors
- effectors: action amplifies the change to drive to process to completion
Nervous system control ( neural )
-Homeostatic control ( eg: breathing, core temperture, blood pressure )
-sensory detection and interpretation
-control of msucle and movement
-higher functions (thinking, speech, learning, memory )
Endorocrie system control ( hormonal )
-homeostatic control ( eg: plasma (Ca2+) or gluclose or PH ect… )
- cellular respiration
-reproduction
-growth and development
-immunity and stress management
Nervous sysytm
-neurons produce action potentials and release neurotransmitter at synapses
-neurotransmitter binds to chemically gated ion channels on post-synaptic cell
-extremely fast signalling
Endocrine system
- endocrine cells realise hormones into the bloodstream to travel to target cells
- hormones blind to the membrane or intercellular receptors of target cells
- relativly slower but it has longer lasting action compared to nervous system
Endocrine glands and organs
Hypothalamus
Pituitary gland
Thyroid gland
Adrenal gland
Pancreas
Parathyroid glands
What are hormones
Chemicals relases by endocrine gland cells
They travel through the blood
Bind to the receptors either on the target cell membrane or withen the target cell
Are made from amino acids or cholrterol
How do hormones work
1)Travel through the bloodstream to target origins
- LIPID SOLUBLE hormones require carrier proteins to travel in the blood ( eg thyroid hormones released by thyroid gland )
- WATER SOLUBLE hormones do not enquire carrier proteins
2) hormones bind to target cell receptors
- LIPID SOLUBLE hormones esally diffuse across plasma membranes to bind to intracellular recpeptors inside the target cells cytosol or nucleus
-WATER SOLUBLE hormones cannot cross cell membrane so they bind to receptor on the membrane of a target cell
3) hormones stimulate target cells to produce a response
- LIPID SOLUBLE hormones bind to intracellular receptor they stimulate creation of new proteins - often enzymes - to produce a response
-WATER SOLUBLE bind to membrane receptors and they activate a 2nd messenger system to produce a response ( increased heart rate )
4) hormone effects stop when hormones are removed
- effect of hormone stops when it unbinds from the receptor
- used or excess hormone, gets broken down, and/or recycled, or excreted in sweat , urine or feces
Lips soluble hormones: what are the chemical classification, synthesis and storage, form of transport, receptor location
Chemical classification: Amines ( Thyroid hormones ) steroid
Synthesis and storage: thyroid hormones: pre-made and stored. Steroids: made as required and is not stored
Form of transport: bound to carrier protein
Receptor location: intracellular receptors
Water soluble hormones: what are the chemical classifications, synthesis and storage, form of transport, receptor location.
Chemical classifications: Amines ( Catecholamines ) Peptides and proteins
Storage and synthesis : all are premede and stored untl needed
Form of transport: unbound ( no carrier protein )
Receptor location: plasma membrane receptors
Lipid soluble hormone - action mechanism
Lipid soluble hormones diffuses across the plasma membrane and binds to receptors in cytosol Or in the nucleus, causes genes activatio, transportation and mRNA production and translation for protein synthesis.
The protein creates a cellular response, this is a slow hormone response because protein synthesis takes time.
Water soluble hormone - action mechanism
Water soluble hormones bind to a membrane receptor on a target cell activating the attached G protein and then the G protein activates or inhibits 2nd messenger and these effects the action of other proteins ( eg: enzymes or ion channels )
Because 2nd messenger is already pre-made, this is a relativly fast response
