Communication and Homeostasis

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

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Communication and Homeostasis

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	Created by Harry Archer almost 10 years ago