Myogenic muscle contraction: heart muscle can contract and relax without nervous system SA node: tissue sends an electrical signal to stimulate atrial contraction (nearly every second) AV node: tissue responds to SA node sending an electrical signal to stimulate ventrical contraction 0.1 seconds after it gets SA node signal These act as the hearts pacemaker to keep it in time
When you exercise, CO2 levels in your blood increase This increase is sensed by the medulla in your brain which sends a nerve signal through your cardiac nerve to the SA node which increases your heart rate When you stop exercising, CO2 levels fall, and the medulla sends another signal to the SA node through the vagus nerve to return rate control to the SA node, slowing down the rate.
Resting potential: the condition of a nerve axon when it is ready to send a signal, or impulse Characterized by Na + ions outside the membrane, and K - ions inside Action potential: the condition of a nerve axon when it is sending a signal, or impulse Characterized by K - ions outside the membrane, and Na + ions outside
ccccc Cell membrane (axon) Key: Sodium ion Potassium ion Resting Potential cytoplasm Action Potential (depolarized area) polarized area
Human body kept within normal limits for: Blood pH CO 2 concentration Blood glucose concentration Body temperature Water balance Affected by your nervous (mostly autonomic), endocrine, and circulatory systems primarily.
Thermostat in the hypothalamus If thermoreceptors detect an increase in temp: Increase activity of sweat glands (persperation, evaporative cooling) Skin arterioles dilate filling capillaries with blood (works really well in elephant ears) If thermoreceptors detect a decrease in temp: Skin arterioles constrict Skeletal muscle activation (shivering)
Cellular respiration always takes glucose out Digestion always adds more glucose From the villi in the intestines, glucose enters capillaries which eventually lead to the hepatic portal vein into the liver Hepatocytes are liver cells that are directed by 2 important hormones for controlling blood glucose (antagonistic) Insulin Glucagon
Pancreatic β (beta) cells produce & secrete the hormone insulin Insulin communicates to body cells the need for opening protein channels to absorb more glucose (facilitated diffusion) Insulin also causes hepatocytes in the liver to convert glucose into glycogen
Pancreatic α (alpha) cells produce & secrete the hormone glucagon Glucagon stimulates the hydrolysis of glycogen in hepatocytes and muscle cells By breaking glycogen down into glucose, blood sugar will go back up
Type I: caused when β cells of the pancreas do not produce enough insulin and is autoimmune (often called juvenile onset) ~10% Type II: caused when body cell receptors do not respond properly to insulin (insulin resistance)~90% Can cause: blindness, kidney failure, nerve damage, higher risk of cardiovascular disease, decreased healing capacity