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Unit 2: Topic 1 - Homeostasis (Neural Homeostatic Control Pathways…
Unit 2: Topic 1 - Homeostasis
Homeostasis
Stimulus Response model
Stimulus > Receptor > Sensory Neuron > Relay/Inter-neuron > Motor Neuron > Effector > Response
Sensory Receptors
Chemoreceptors
Detect chemicals
Thermoreceptors
Detect changes in temperature
Mechanoreceptors
Detect physical pressure/distortion
Photoreceptors
Detect light (electromagnetic pulses)
Nociceptors
Detect pain
Effectors
Muscles
Glands
Interpret feedback control diagrams
A steady state, maintenance of dynamic internal balance
Metabolism
Describes all chemical reactions related to sustaining life
Anabolic
Build up
Simple + Simple = Complex
Consumes energy
Catabolic
Break Down
Complex = Simple + Simple
Releases energy
Metabolism can change body heat & chemistry. Metabolic (enzyme) activity management keeps conditions within tolerance limits
Neural Homeostatic Control Pathways
Neurons transport nerve impulses
Motor Neuron
Sensory Neuron
Interneuron
Neurons
Soma
Cell body
Dendrites
Branched extensions (receivers)
Axon Hillock
Where signals are generated (after review)
Mylin Sheath
Electrical insulation surrounding axons
Schwann's Cells
Cells that the mylin sheath is made of
Node of Ranvier
Exposed part of the axon between Schwann's cells
Axon
Extension which transmits signals
Axon Terminal
Branched end of axon
Synapse
Gap between axon terminal and dendrites of next neuron
Signal Transmission
Action Potentials
Long distance electrical signals conducted in an identical manner
Synaptic Transmission
Short distance (neuron-neuron) through neurotransmitters)
Hormonal Homeostatic Pathways
Hormones
Long distance chemical messengers
Part of the endocrine system
Travel via lymphatic or circulatory system
Cell Sensitivity
Relies on hormone receptors
More = More sensitive
Less = Less sensitive
Hormonal Signal Transduction
Water Soluble Hormones
Travel in blood
Bind outside of target cell
Cannot diffuse through bi-layer
Triggers events in cell membrane > Chemical signal > Intracellular response
Lipid Soluble Hormones
Travel in blood with transport protein
Diffuse through bi-layer
Bind to intracellular receptors > moves into nucleus > triggers cellular response
Thermoregulation
Structural Features
Insulation
Reduces heat flow between body & environment
Mitochondria
Cellular respiration = heat & ATP
Brown Adipose Tissue
Contains more mitochondria than white adipose tissue
Non-shivering thermogenesis
Behavioural Responses
Kleptothermy
Huddling
Torpor
State of decreased activity & metabolism
Hibernation
Long-term torpor
Aestivation
Summer torpor (during hot times)
Physiological Mechanisms
Vasomotor Control
Vasoconstriction
Vasodialation
Evaporative heat loss
Sweating
Countercurrent heat exchange
The way that blood flows
Thermogenesis
e.g. shivering, cellular respiration, non-shivering thermogenesis
Homeostatic Mechanisms
Thyroid Homrones
Secretes thyroxin (T4) to speed up metabolic activity
Insulin
Stimulates uptake & release of glucose and increases cellular respiration
Osmoregulation
In Animals
Behavioural Responses
Drinking & Eating
Thirst/desire to restore water balance
Nocturnal Behaviour
Reduces evaporative heat loss
Seeking shade
Reduces evaporative heat loss
Physiological Mechanisms
Hyperosmotic
Tend to lose water
Concentrated urine
Actively eliminate salts
Hypoosmotic
Tend to gain water
Dilute urine
Actively uptake salts
On land
Concentrated urine
Limit sweating
Structural Features
Excretory System
Manages bodily fluids
Body Coverings
Reduces evaporative heat loss
Salt Glands
Excretes excess salt from water
Homeostatic Mechanisms
Antidiuretic Hormone (ADH)
Manages water re-absorption
Renin-Angiotensin-Aldosterone System
Manages blood pressure & volume
In Plants
Structural Features
Stomata
Guard cells
Homeostatic Mechanisms
Abscisic Acid
Slows/stops photosynthesis and growth
Plant Types
Xerophytes
Arid environment
Halophytes
Saline environment
Mesophytes
Normal environment
Hydrophytes
Water/Wet environment
