Study- Term 3 Flashcards
Homeostasis
Maintenance of a constant internal environment within a living organism despite internal or external changes to their environment
Stimulus
A detectable change in either the internal or external environment that acts as a signal for cells
Receptors
A specialised cell or group of specialised cells (sense organ) that receive stimuli
Regulator
A coordinating centre which the receptor sends a chemical message to that determines if a change is required
Effectors
Either a muscle (movement response) or gland (secretes molecules)
Response
The change in chemicals within a cell or within an effector organ
Chemoreceptors
Chemical
Photoreceptors
Light
Mechanoreceptor
Touch, pressure, stretching, motion, sound waves
Thermoreceptor
Temperature, heat
Nocireceptor
Potentially damaging stimuli or to actual damage
Feedback
The return of information
Negative
An action that opposes the input
Positive feedback
Instead of getting a counteracting response to some variable you instead intensify the variable
Negative feedback
When some variable triggers a counteracting response in order to come back to some set point
Hormonal homeostatic pathways
- involve the endocrine system
- can be slow
- chemical message,travelling in bloodstream
Neural homeostatic pathways
Involve nervous system
Very rapid
Electric impulse, travelling along nerves
Hormones
Chemical messengers that regulate the activity of cells and organs
Endocrine
Travel long distances through the body to target cells
Endocrine + hormones
Hormones produced in endocrine glands which are released directly into the blood vessels, work together to maintain homeostasis
How hormones work
Hormones affect only certain tissue cells or organs called target cells or target organs
Target cells must have protein receptors present on the cell membrane to allow the hormone to attach
Hormones must bind to the target cell to influence the cell
Nervous system
Comprised of nerves (neurone)
Two parts:
-central nervous system (CNS)
-peripheral nervous system (PNS)
Nervous system
- Receptor detects a change (stimulus)
- Receptor to the CNS by a sensory neurone
- CNS to an organ that carries out a response a motoneuron carries this message
Motor neurone
Carry message from the brain to allow us to move our muscles
Inter neuron
Connect neurons to other neurons
Sensory neuron
Receive information from sense organs. Send sensory information to our brain and spinal cord
Thermoregulation
Maintenance of a constant internal temperature of an organism independent of the temperature of the environment
Endotherms
Most of their heat is generated internally through metabolic activity and they are not so reliant on environmental conditions
Ectotherms
Gets their body heat mainly from their environment and can tolerate a reasonably wide range of body temperatures
Thermoregulatory mechanisms:
Physiological mechanisms-
Evaporate heat loss Vasodilation Vasoconstriction Countercurrent Thermogenesis
Evaporate heat loss
Humidity affects thermoregulation by limiting sweat evaporation
Vasodilation
Dilation of blood vessels in the skin
Vasoconstriction
Constriction if blood vessels in skin
Countercurrent
Blood vessels in which heat flows warmer to cooler blood
Thermogenesis
Production of heat within tissues to raise body temp
Structural features-
Brown adipose tissue=
Specialised for rapid heat production, transfers food from energy to heat
Structural features:
Increase no. of mitochondria per cells=
Enables organisms to generate heat by increasing the rate at which they metabolise fats and sugars
Structural features:
Insulation-
Traps warm air to insulate organism
Behavioural responses:
Kleptothermy=
Sharing another organisms body heat
Behavioural responses:
Torpor=
Physiological state in which the metabolic rate is lowered to save energy
Behavioural responses:
Hibernation-
State of animal dormancy taking place in the winter
Behavioural responses:
Aestivation=
State of animal dormancy taking place in the summer
Homeostatic mechanisms:
Thyroid hormones-
Increase available energy in the body, as well as by increasing appetite pulse, the amount of oxygen delivered to different body parts and fat building up
Homeostatic mechanisms:
Insulin-
Promotes an increase in heat production and or vasoconstriction
Osmoregulation
The maintenance of a constant solute and water balance
Excretion
Removal of metabolic waste
Osmoconformers
Maintain internal environment that is isotonic (the same) to external environments
Osmoregulators
Actively control the levels of internal salt concentrations so that overall solute concentration is constant
Terrestrial animals
Must take in water to replace that which is continually lost in the process of eliminating waste and by evaporation from the lungs and body surface
Hormonal control of water balance in mammals
Antidiuretic hormone (ADH) is most important for controlling reabsorption of water—> released by pituitary glands
Vacuoles
- Store water and other substances in cells
- Important for plants as they help maintain turgor pressure against the cell wall when water levels are low
Waxy cuiticle
- waterproof layer covering leaf surface (epidermis)
- prevent water losses
Stomata
- found on leaf surface (epidermis)
- surrounded by guard cells —>control opening and closing stomata
- close when water levels in plant are low—> reduces water loss
Guard cells
- Cell walls are thicker next to stomata pore than next to surrounding cells -when they are full of water—>thin walls stretch more than thick ones —>two cells curve away from each other->opens stomata
- when they lose water —> turgor pressure decreases —> cell walls become straighter—> stomata close
Diseases and it’s causes
Disease is a physiological abnormality or significant disruption in the health of an individual. It is caused by a variety of factors such as genetic predisposition, environmental conditions, poor nutrients and by pathogens
Infectious
They are caused by another organism or organic agent and can be passed from one individual to another either directly or indirectly. Are caused by pathogens which are biological agents that caused diseases or illnesses to a host
Non-infectious
They cannot be spread from one side of individual to another
Cellular vs non-cellular
Cellular=can reduce
non-cellular=cannot reproduce alone requires host
Virulence
Virulence of a pathogen refers to its ability to cause disease in a host
Pathogenesis
Pathogenesis refers to the mechanisms which have a lead to its current state
Virulence factors
Are molecules or strategies that can contribute to the survival of pathogen. they are typically proteins and include adherence factors, invasion factors, capsules, toxins, lifestyle changes
Adherence factors
Before a pathogen can cause a disease it must first enter the host for this to occur the pathogen must adhere to a molecule on the membrane of the host cell a starting point for the micro organism to penetrate tissues and colonise the host
Invasion factors
Are proteins that allow pathogens to enter cells. Produce proteins that either disrupt host cell membranes or stimulate Endocytosis into the host cells so the pathogens can get inside
Capsules
Bacterial capsule is a very large structure of many bacteria it is a polysaccharide layer that lies outside the outer membrane of the cell. It allows movement into the host cell easier
Toxins
Proteins that poison host cells and cause tissue damage.
Endotoxins
Bound to the pathogen and can induce inflammatory responses when the host tries to destroy it
Exotoxins
Are produced and secreted by pathogen once inside the host
Mode of transmission
Direct contact or indirect contact
Innate immune system
Non-specific defence mechanism that comes into play immediately or within hours of an antigens appearance in the body
Innate immune system includes
Physical barriers to prevent entry of pathogen and chemicals in blood, immune system cells that attack pathogens
First line of defence
Physical and chemical barriers prevent entry of pathogens
