Biology Module 8 Flashcards
What is homeostasis?
The process of keeping conditions inside the organism relatively stable or constant to maintain a stable environment.
Things we do when cold
Shivering - muscles rub together to generate heat
Metabolism increases - break down more glucose which produces heat from respiration
Things we do when hot
Sweat - vasodilation (blood to surface of skin). Excess body heat is used to convert beads of sweat into vapour to evaporate off our skin.
negative/positive feedback
negative - response is opposite to the stimulus (e.g., if we are cold, we will warm up)
positive - response enhances the stimulus (e.g., oxytocin promotes contractions, contractions release oxytocin)
Why is homeostasis so important?
It is needed for an organism to function properly and efficiently (allows the enzyme’s optimal conditions to be met)
Flow chart of stimulus to response
Stimulus (environmental change)
Receptor (detects the change e.g., thermoreceptors) Messenger (chemical and electrical signals that contain information)
Effector (the gland that releases a hormone or muscle that carries out response)
Response
Types of neurones
Sensory - between receptor and messenger (detects stimulus)
Inter - mostly in brain/spinal cord (transmits information from a sensory to motor)
Motor - takes the impulse to the effector
Set Point
The level or point at which a body variable tends to stabilise (e.g., 37 degrees)
Control Centre
Hypothalamus
Types of Receptors
Thermoroceptor: temperature (skin/hyp)
Chemoroceptor: carbon dioxide, oxygen, pH (nose/taste buds/hyp)
Int/Exteroceptor: inside and outside of body
Osmoreceptor: changes in salt/water (kidney)
Mechanoreceptor: touch, pressure, vibration, sound (skin)
Body Temp High process
body temp rises
thermoreceptors detect change
hypothalamus
muscles and glands
the metabolism will slow down, vasodilate (excess blood flow to skin, heat loss through sweat)
Exposure to light process
increase in light
photoreceptor detects
sensory neuron (optic nerve)
interneuron CNS
motor neuron
iris (effector)
expand closing pupil
Flow of types of neurons
The nervous pathway consists of a sensory neuron (nerve cell) that sends the message to the interneurons on the central nervous system (CNS). Then travels to the motor neuron that transfers the message to the effector.
Goose bumps
Piloerection - done when cold
Constriction of the piloerection muscles around hair follicles (increases the insulating effects of hair)
Minimal effects in humans but in animals with thick fur, the layer of trapped air increases significantly
Metabolic changes
Regulated by pituitary and thyroid - impacts rate of metabolic reactions in mitochondria (releases heat)
Behavioural Responses to temp
seeking shade (e.g., kangaroo to get out of sunlight)
lick forearms (e.g., kangaroo applys saliva to skin to increase evaporation)
pant (e.g., dog, hot water from mouth is evaporated)
Structural Responses to temp
seasonal coats (thin coat in summer, thick coat in winter)
blubber (layer of fat, retains heat)
Physiological Responses to temp
thirst (indicator the animal is dehydrated, hormones released to make them thirsty)
metabolism (can be slowed or increased)
glucose/glycogen/glucagon
glucose - simple sugar
glycogen - glucose stored in the liver (glucose stuck together)
glucagon - hormone that releases glucose from glycogen
High blood glucose process
high blood glucose
pancreas
beta cells release insulin
peripheral tissue cells take glucose from the blood
normal blood glucose
Low blood glucose process
low blood glucose
pancrease
alpha cells release glucagon
glucose broken down in liver and released to blood
normal blood glucose
endotherms/ectotherms
endotherms - organism that maintains it owns body temp by generating heat metabolic processes (warm blooded) e.g., a dog, humans
ectotherms - organisms that regulate their body temp based on the external environment (cold blooded) e.g., lizards, snakes
What are neurons?
Neurons are nerve cells that transmit signals by electrochemical charges in their membrane.
Functional unit of the nervous system.
Structure of a neuron
Axon: Long section (usually only one of them, branch at the end leading to synaptic terminals, release neurotransmitters into the gap between the neurons)
Myelin Sheath: Fatty insulating material (keeps the electrical signal in the neuron so it is transmitted full length)
Dendrites: Small branch-like projections (connects to other cells, increases surfaces area and allows for the collection of incoming impulses)
The impulse goes from the dendrite, along the axon and to the end.
Synapse
Gap inbetween two neurons
For an impulse to cross the synapse, neurotransmitters are released by the axon terminals
Along the neuron (signal is electrical)
At the synapse (signal is chemical)
What are neurotransmitters?
Signalling molecules
e.g., serotonin (increases mood, sleep) and dopamine (reward-motivated behaviour)
Importance of synapse
Pass impulses in one direction only, passing between neurons, acts as junctions
Depressants/Stimulants
Affect the transmission of nerve impulses along the synapse
What are nerves
Bundles of nerve fibres outside the brain. Fibres are surrounded by myelin (to insulate)
What is an action potential?
Rapid and short-change in the membrane potential of an excitable cell.
Movement of information down a neuron.
The threshold is a particular value of the membrane voltage that needs to be reached for an action potential to be started.
Flow Chart of Action Potential
- Stimulus (e.g., light)
- Sensory receptor
- If ABOVE THRESHOLD, Na (sodium) channels open > (depolarisation)
- Wave of excitation spreads along neuron
- As the impulse arrives at a section of the neuron, causes more Na channels to open up
- Rapid influx of Na into the axon
- Further increases the permeability of the membrane to Na
- Inside is positive relative to outside (DEPOLARISED)
- Na channels shut and K (potassium) ions also move out
- Membrane is repolarised (hyperpolarised first)
- K channels shut, restores resting membrane potential
- Refractory period (drops down on graph)
- Ready to go again
Graph explanation
Voltage on Y, Time on X
Start of spike (Na channels open, Na enters)
Just before peak (K channels open, K begins to leave)
Peak (Na channels close)
Just after peak (K channels close)
Endocrine System
Body system composed of different endocrine glands that secrete hormones directly into the blood stream.
A NETWORK OF GLANDS THAT SECRETE HORMONES FOR REGULATION
Hypothalamus
Considered the link between the nervous system and the endocrine system.
Receives information from almost all parts of the nervous system.
Hormones
Diverse group of cell signalling molecules
Types of Hormones
Prolactin - anterior pituitary gland, targets breast cell glands for milk production
Adrenalin - medulla in the adrenal gland, targets the liver and heart to prepare body for fight or flight
ADH/anti-diuretic - pituitary gland, targets tubular cells in kidney to release less water, decreasing the amount of urine production
How does ADH work?
If you are dehydrated:
You need to wee less so more water is retained
Increase in ADH
Increase in water retention
Decrease urine
Drink too much:
Decrease ADH
Therefore diuresis occurs
Urine output increases
What hormones are involved in the regulation of water and salt levels?
ADH, aldosterone
What do plants need to regulate?
Maintain water balance, remove metabolic waste, internal concentrations of major nutrients
Hydrophytes
Live in fresh water, lots of water available.
Due to the water gradient (low in plant, high outside), water tries to move into the plant.
- lots of stomata
- large surface area
stops tissues from flooding
Xerophytes (e.g., spinifex)
Live in dry climates > not much water
- focus on conserving water
- small number of stomata/stomata hairs/depressions stomata sit in
- builds a microclimate around stomata (reduces air flow and water loss via transpiration)
Aussie Plant Adaptation
Eucalyptus - reduce water loss
- leaves stand vertically to decrease SA (avoids radiation)
- thick waxy cuticle to prevent evaporation and reflect heat