Lecture 1- Homeostasis Flashcards
Define the term homeostasis
Homeostasis is the maintenance of a constant internal environment.
What are the 7 life processes?
- Sensitivity: awareness of changes in the environment, eg heat, light, tough and chemical
- Growth: ongoing increase in size of organisms
- Respiration: energy from food is unlocked by this process. 2 types anaerobic, aerobic
- Nutrition: plants and animals need food as a source of energy and growth
- Excretion: getting rid of metabolic wastes, produced by the body eg water, urine, and carbon dioxide. This is not elimination (poo)
- Movement: both animals and plants can move
- Reproduction: all plants and animals can reproduce, carrying out their genes and continuing the species. Can be sexual or asexual (one parent reproduces itself)
What are the list of parameters under homeostatic control
Environmental factors that effect cells:
-osmolarity, temp, and pH
Materials for cells needs
-nutrients, water, Na, ca, inorganic ions, oxygen
Internal secretions:
-hormones, neurotransmitters etc
Communication via nervous system and endocrine system is essential for homeostasis to occur.
What were Canons 4 postulates of homeostasis?
- Nervous system preserves ‘fitness’ of internal environment
Fitness= conditions that provide normal function
Eg nervous system coordinates and integrates control of blood volume/ pressure, osmolarity etc - Tonic level of activity
Ie it’s up and down all the time not on and off
Eg neural regulation of blood vessel diameter - Antagonistic control
-generally for systems not under tonic control
Eg blood glucose: insulin vs glucagon
Eg sympathetic vs parasympathetic divisions of ANS - Chemical signals can have different effects in different tissues
-Receptor dependant
Eg adrenaline (epinephrine) constricts or dilates blood vessels, depending on a or b adrenergic receptors
Diseases are generally of two types when failure of homeostasis occurs. What are they?
- Internal ‘failure’ of physiological process(es)
Eg abnormal cell growth, auto-immune diseases, inherited disorders - External causes
Eg toxins, trauma, bacteria
What is the term to describe when the body attempts to compensate when homeostasis is disturbed?
Pathophysiology
Homeostasis is maintained by local of long distance pathways. Explain the two?
- Local control: cell or tissue senses a change (ie locally) and responds by paracrine or autocrine mechanism
Paracrine: signalling affects cells of a different type than the cell performing the secretion
Autocrine: signalling affects cells of the same type
Eg a drop in O2 concentration results in the release if paracrines (NO, CO2, lactate, that sense this drop; paracrines then relax muscles in blood cell walls so more blood can deliver O2.
-the response is generally restricted to the area where the change took place. - Long distance (or reflex control pathway)- were the control of the reaction lies outside the organ that carries out the response (more systematic in nature) eg a normal autonomic reflex arc eg the osmoregulation one
What is the 7 step pathways of a feedback response loop?
Stimulus
receptor: all receptors have a mimum stimulus that must be achieved in order for reflex to occur
afferent pathway,
integrating centre: compares set point to actual level of the variable
efferent pathway, effector, response
Error signal: difference between actual level and set point
What are the 5 freedoms to the approaches of animal welfare? To minimise suffering and promote well being
- Freedoms from hunger and thirst
- Freedom from discomfort
- Freedom from pain, injury, disease
- Freedom from fear and distress
- Freedom to behave naturally
What is negative feedback?
The output systems (ie response) opposes or removes the (intensity) of the origins signal.
The mechanisms cause the variable to change in the opposite direction to that of the initial change, returning to its ideal value (set point)
Set points: of a variable can be varied. The adaptation of physiological process to the environment is called:
Acclimatisation: (natural, eg prior conditioning to cold temps) or
Acclimation: artificial eg rats and short term exposure to cold
Give an example of a simple neuron reflex eg temperature regulation
Body temp increases
Sensory neurons to integrating centre
Integrating centre: brain thermoregulatory centres compare actual temp to set point and send appropriate signals to effectors
Output
Effectors: sweat glands, skin blood vessels, and skeletal muscles
Body temperature decreases
Negative feedback!
Give an example of an endocrine loop..meh
Meg
Positive feedback. Give an example
Eg parturition
Cervical stretch -> stimulates oxytocin release -> causes uterine contractions -> push baby against cervix (further stretch) -> stimulates more oxytocin release
What are the 7 life processes?
- Sensitivity: awareness of changes in the environment, eg heat, light, tough and chemical
- Growth: ongoing increase in size of organisms
- Respiration: energy from food is unlocked by this process. 2 types anaerobic, aerobic
- Nutrition: plants and animals need food as a source of energy and growth
- Excretion: getting rid of metabolic wastes, produced by the body eg water, urine, and carbon dioxide. This is not elimination (poo)
- Movement: both animals and plants can move
- Reproduction: all plants and animals can reproduce, carrying out their genes and continuing the species. Can be sexual or asexual (one parent reproduces itself)
