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2901488
Communication and Homeostasis
Descrição
A2 Module 1 Unit 1
Sem etiquetas
postgrad
Mapa Mental por
Harry Archer
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Harry Archer
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Resumo de Recurso
Communication and Homeostasis
COMMUNICATION
Multicellular organisms require communcation to cooridnate the functions of different systems
Division of Labor
Stimulus -> Receptor -> Effector -> Response
External Stimuli: Changes in light, temperature
Internal Stimuli: Body temperature and blood sugar levels
Relies on Nervous and Hormonal (Endocryne) systems
HOMEOSTASIS
The process of maintaining a constant internal environment, despite external changes
Negative Feedback
Response reverses the change
Positive Feedback
Less Common
Doesn't lead to homeostasis: Amplifies the change
Often harmful, however in childbirth the release of oxytocin is positive
Maintaining Body Temperature
Endotherms
Warm-blooded: use physiological mechanisms to regulate body temperature
Ectotherms
Cold-blooded: rely on external temperatures solely
Action Potential
Sensory receptor
Energy Transducer: Converts stimulus into electrical signal
Neurone
Resting Potential
-60mV
Action potential
Generator potential
Slight depolarisation caused by small stimuli
Threshold potential
-40mV
When enough gated sodium ion channels open an action potential is generated
Transmitted down neurone by local currents
Myelinated Sheath
Schwann cell with nodes of ranvier between
Saltatory conduction: Node to node
Speeds up transmission
Sensory Neurone
Receptor -> CNS
Relay Neoruone
Motor Neorone
Relay -> Effector
Synapses
Summation
Spatial
Many pre to one post
Temporal
Many small impulses
Roles in the CNS
Allows junction for many to one or one to many
Only allows one way flow
Summation allows low level impulses to flow
Acclimatisation to background stimuli
Running out of vesicles (fatigue)
Glands
Endocrine
Secretes hormones directly into blood for transport
No Duct
Exocrine
Duct
Secrete materials along a duct directly to target location
Hormones
Steriod
Can pass directly into cell via csm
Protein/Peptide
Must bind to receptor of target cell
Regulating Blood Glucose
Liver
Has endocrine and exocrine functions
Secretion of enzymes (Exocrine)
Secretes into the pancreatic duct
Secretion of hormones (Endocrine)
Islets of Langerhans
Alpha Cells
Glucagon
Beta Cells
Insulin
Diabetes
Disease where the body isn't able to control its blood glucose concentration
Leads of Hpo/Hyperglycaemia
Normal conc. is 90 mg 100 cm-3
Type II
Non insulin dependant
Can still produce insulin
With age, receptors decline and respond less freuqiently
Secretion by beta cells may also decrease
Treated by monitoring diet
Type I
Insulin Dependant
Develops in childhood
Autoimmune Response
Body's own immune system attacks Beta cells
Cannot manufacture sufficient insulin
Cannot store excess glucose as glycogen
Treated by injection
Control of Heart Rate
Factors
Bpm
Strength of Contraction
Volume per beat
Heart tissue is myogenic
SAN is the start point of all contractions
Medulla oblongata sends signals to SAN to alter rate
Accelerator Nerve
Faster
Vagus Nerve
Slower
60-80 waves per minute
Stimuli
Stretch receptors in muscle
Low pH of blood
Adrenaline in blood
High bp detected by carotid sinus
Triggers vagus nerve
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