6.5 – PART II Endocrine system and homeostasis

Homeostasis review Blood pH CO2 concentration Blood glucose concentration Body temperature Water balance within tissues Body variables must stay within certain limits (normal limits)

EX. Body temperature 37 c or 98.6 f Exact values all the time? NO Cold environment or physical exertion alter body temp Internal mechanisms to alter body temp to be close to 37 c Mechanisms (physiological changes) are called negative feedback mechanisms -Negative feedback control functions similar to a thermostat -Thermostat signals actions to keep value within a range -Negative feedback does this for a range typical for homeostasis

Nervous & endocrine system Homeostatic mechanisms under control of autonomic NS Endocrine system includes many glands producing variety of hormones Blood transports hormone to specific tissue

back to body temperature Your temperature is rising Your temperature is cooling BIOLOGICAL THERMOSTAT IN YOUR BRAIN IS THE HYPOTHALAMUS  Hypothalamus receives info from thermo-receptors in skin  Begins to activate cooling mechanisms  Increased sweat gland activity and subsequent evaporative cooling  Arterioles in skin dilate (get bigger) and skin capillaries fill with blood  Heat leaves skin by radiation, you cool down  Hypothalamus receives info from thermo-receptors in skin  Begins to activate warming mechanism  Constriction of skin arterioles so blood goes to deeper organs and tissues  Less heat lost by radiation  Hypothalamus stimulates skeletal muscle to shiver

In summary The Endocrine System -A stimulus is received and processed. -Hormones are secreted into the blood, via ducts. -They are carried to the target tissue, the place of action. -They action of the hormone changes conditions of the tissue. -This change is monitored through feedback. -Most hormonal change results in negative feedback.

Thermal picture showing a dung beetle regulating its internal body temperature by its external environment. What is the darkened object?

Typical blood glucose activity Glucose from diet absorbed into blood stream Cells constantly taking in glucose for cellular respiration Glucose travels from digestive system to liver through hepatic portal vein Hepatic portal vein only vessel where glucose concentration fluctuates Body receives blood after being acted on by liver cells (hepatocytes) Hepatocytes directed to act by hormones insulin and glucagon produced in pancreas Insulin and glucagon have opposite effects on glucose concentration

Blood glucose concentration High blood glucose Pancreas – beta cells produce insulin Insulin opens protein channels which allows glucose to diffuse by facilitated diffusion Insulin also stimulates hepatocytes to take in excess glucose (when it is high in the HPV) and convert it to glycogen Glycogen stored as granules in cytoplasm of hepatocytes (same thing occurs in muscles) Same ultimate result: lower blood glucose concentration Low blood glucose Causes by lack of food intake or rigorous physical activity Body needs to use glycogen made/stored by muscle/liver cells when glucose was in excess Situation results in pancreatic alpha cells producing glucagon Glucagon stimulates hydrolysis of glycogen granules producing glucose Glucose enters bloodstream increasing blood glucose

Any questions?

ntent/ /Animations/Endocrine%20Syste m.swf The complete endocrine system.

Explain how a nerve impulse passes along a non-myelinated neuron.

Explain how a nerve impulse passes along a non-myelinated neuron.

Explain the principles of synaptic transmission

Outline the use of four methods of membrane transport in nerves and synapses.

Outline the use of four methods of membrane transport in nerves and synapses.

Explain the control of blood glucose.