1. Temperature Control in Humans Premed Biology January 2015

2. 37⁰ C (98.6 F) What is your normal body temperature?

3. Homothermic (constant & high body temperature) or Endothermic (warm blooded) – Birds & Mammals Poikilothermic ( Varying in temperature according to the surrounding or environment temperature) or Ectothermic ( cold-blooded) – Amphibians & Reptiles – Bask in warm temperature and hibernate in cold temperature

4. Regulation of body temperature is a type of homeostasis called “Thermoregulation” Thermoreceptor is a type of “sensory receptor” detects change in temperature

5. EFFECTORRESPONSE TO LOW TEMPRESPONSE TO HIGH TEMP Smooth muscles in Arterioles of skin Contraction of muscles resulting in vasoconstriction Skin turns blue Muscles relax resulting in vasodilation Skin turns red Sweat GlandsNo sweatGlands secrete sweat that evaporates Erector pili muscle of skinMuscles contract raising skin hair (Goosebumps) to trap warm air Muscles relax lowering hair for evaporation Skeletal MusclesContract resulting in shivering No shivering Adrenal & Thyroid glandsSecrete adrenalin and thyroxine increasing metabolic rate (E.g. High metabolic rate in LIVER generating heat) No gland secretion

7. Erector pili muscle (muscle connected to hair follicle) CONTRACTS in response to cold trapping warm air E.g. Goosebumps

8. Sensory Transduction All Sensory processes begin with STIMULI (form of energy) – Many (but not all) detect from outside body (Heat, light, pressure, chemicals) Sensory Receptor converts stimulus energy into a change in membrane potential Sensory information travels through nervous system as impulse or action potentials When action potential reaches the brain through sensory neurons, circuit of neurons process generating the PERCEPTION of stimuli

9. Transduction of stimuli by sensory receptors subject to 2 modifications: 1. Amplification (Strengthening of sensory signal) 2. Adaptation (Upon continuous stimulation, receptors undergo a decrease in responsiveness)

11. Sensory Receptors Body contains 5 types of sensory receptors: 1. Mechanoreceptors for touch & pressure 2. Thermoreceptors for temperature change 3. Nociceptors for pain 4. Chemoreceptors for taste and smell 5. Electromagnetic receptors for light (spectrum)

12. Mechanoreceptors Sense physical deformation caused by mechanical energy (eg. Pressure, touch, stretch, motion and sound) Receptors that detect light touch or vibration are close to surface of skin. Strong pressure and vibrations are detected in deep skin layers.

13. Mechanoreceptors Vertebrae stretch receptors, are mechanoreceptors that detect muscle movement and triggers Knee-jerk-reflex Stretch receptors are dendrites of sensory neurons that spiral around skeletal muscle fibers Muscle fibers stretch  sensory neurons depolarize  nerve impulses  spinal chord  motor neuron  Reflex Response

14. Chemoreceptors Transmit information about solute concentration, others about individual kinds of molecules Eg. Osmoreceptors in brain stimulate thirst, detect changes in total solute concentration in blood Receptors for O2, CO2, glucose, and amino acids

15. Electromagnetic Receptors Detect forms of electromagnetic energy Light, electricity, and magnetism

16. Thermoreceptors Located in skin and anterior hypothalmus Send information to body’s thermostat in posterior hypothalmus

17. Pain Receptors Detect stimuli that reflect harmful conditions Also called “Nociceptors” Some chemicals enhance perception of pain Damaged tissues release prostaglandin, local regulators of inflammation Prostaglandins worsen pain by increasing sensitivity

18. Sensory Receptors in Skin

21. Physical stimulus  Neural Signals Each receptor has own neural pathway to the CNS resulting in different sensations (E.g. Body temperature detected by thermoreceptors and send to Hypothalamus)