Homeostasis & Response

Homeostasis & Response

1. Nervous System

   • Electrical Impulses along neurones
   • Stimulus
     • Change that causes a response
   • Sense Organs
     • Sensetive to stimuli
     • Cluster of receptor cells
   • Reflexes
     • Automatic
     • Rapid
     • Protects body from harm
     • Basic body functions
       • ie. breathing
     • Sequences
       • Stimulus => Receptor => Coordinator => Motor neurone => Effector => Response
   • Synapses
     • Junction between 1 neurone and another
       • ie. Sensory => Motor

2. Endocrine System

   • Homeostasis
     • Maintanence of a constant internal organism.
   • Hormones
     • Chemical substances secreted by glands
   • Pituitary gland
     • Master gland
     • ADH - urine produced by kidneys
     • FSH - Follicle Stimulating Hormone - Stimulates ovaries to make Oestrogen
       • Egg to mature
     • TSH - stimulates thyroid gland to make thyroxine
     • LH - Lutenising Hormone - stimulates eggs release
   • Thyroid Gland
     • Thyroxin
       • Regulates metabolism
   • Adrenal gland
     • Adrenaline - fight or flight
   • Ovaries
     • Oestrogen - Growth + Repair of Uterus wall
     • Progesterone - Maintains thickness of Uterus wall
   • Testes
     • Testerone

3. The Brain

   • controls behaviour
   • Cerebral Cortex
     • Consciousness
     • Memory
     • Balance
     • Intelligence
   • Cerebellum
     • Coordinating muscular activity
     • Balance
   • Medulla
     • Unconscious Activity
       • Heart rate
       • Gut movements
       • Breathing
   • Hypothalamus
     • Controls body temperature
   • Studying Brain Damage
     • People suffering from damage can be used to map the brain's behavior
     • Electrically Stimulating parts of the brain
       • Remove top of Skulls
       • See effect
     • MRI scans
       • Brain tumour will affect behaviour
         • MRI scan shows where the affected area is
     • Brain Tumours
       • Conscious patients
         • No Nerve endings

4. The Eye

   • Sense Organ
   • Cornea
     • Shields the eye from bacteria & Protects front of eye
   • Iris
     • Controls amountof light entering the eye via pupil
     • Dilated pupil
       • Circular muscles relaxes
       • Radial Muscle contracts
     • Pupils constricts
       • Circular muscles contracts
       • Radial Muscle contracts
   • Lens
     • Focuses light rays
     • Produces image on Retina
   • Retina
     • Layer of light Sensitive Lights
     • Converts light to neural signals
   • Optic Nerve
     • Transfers visual info => brain
     • Sensory Neurones
   • Sclera
     • Tough / Fibrous
     • Resistant to squashing
   • Ciliary Muscles + Suspensory Ligiment
     • Controls shape of lens
   • Binocular / Monocular Vision
     • Binocular
       • Two eyes
         • Overlapping fields
       • Good depth perception
       • Smaller field of view
     • Monocular
       • Two eyes used seperately
       • Limited depth perception
       • Large field of view
   • Accomodation
   • Vision Problems
     • Myopia
       • Short Sighted
       • Distant objects = blurry
     • Hyperopia
       • Near objects = blurry
       • Long Sighted

5. Controlling body temperature

   • Controlled by thermoregulatory centre in brain
     • Hypothalamus
   • Hot
     • Vasodilation
       • Arterioles dilate so more blood enters and more heat is lost
     • Sweat
       • Sudorific glands remove heat when water changes state
     • Pilorelaxation
       • Hairs flatten
     • Stretching out
       • Larger SA
   • Cold
     • Vasoconstriction
       • Arterioles get smaller so less blood enter and less heat is lost
     • Shivering
       • Rapid contraction & Relaxation
         • Heat from respiration
     • Piloerection
       • Hairs on skin stand up
     • Curling up
       • Smaller SA

6. Controlling Blood Glucose levels

   • Blood glucose % monitored by pancreas
   • Diabetes
     • Cannot control levels of blood glucose
     • Type 1
       • Treated by daily insulin injections
         • Can not be given in tablet form as it would be digested
         • Live normal lives
       • Genetic problem
     • Type 2
       • Links to
         • Old age
         • Obesity
         • Lack of excersise
       • Treated by
         • Balanced diet
         • Losing weight
         • Regular excersise
         • Otherwise drugs that
           • Insulin work better on the body
           • Pancreas make more Insulin
           • Reduce amount of glucose you absorb

7. Maintaining water + Nitrogen Balance

   • Osmoregulation
     • Regulating aount of water in the body
   • Nitrogen
     • Manufacture of proteins
     • Removed by Urea
     • Filtered from Kidneys + expelled in urine
   • Kidneys
     • Filter blood to clean it
     • Blood passes once every 5 minutes
     • Selective Reabsorption
       • Too concentrated = ADH produced
       • Tiny tubules
         • More ADH = More water absorbed
       • Receptor Cells detect concs of solutes in the blood
     • Kidney problems
       • Dialysis
         • Blood leaves body and flows through machine
           • Partially permeable membranes
         • Dialysis fluid
           • % of dissolved substances in a healthy person
         • 8 hours for dialysis to be complete
         • Disadvantages
           • Controlled diet
       • Kidney Transplants
         • Replaced from donor kidney
         • Joined to patient's groin
         • Rejection due to different antigens
           • Immunosuppressant drugs
             • Poor immune system
         • Lasts roughly 9 years

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