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Nerves, Hormones, and Homeostasis. Topic 6.5. The vertebrate nervous system has two main divisions: · Central Nervous System (CNS): consists of the brain and spinal cord. - PowerPoint PPT Presentation
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Nerves, Hormones, and Homeostasis
Topic 6.5
The vertebrate nervous system has two main divisions:·Central Nervous System (CNS): consists of the brain and spinal cord.·Peripheral Nervous System (PNS): consists of all the nerves and their branches that enter and leave the brain and spinal cord.
Motor Neuron:
nodes of Ranvier
motor end plates
Motor neuron
Nerves are made up of 3 types of neurons (nerve cells):·Sensory neurons: bring information to the CNS from receptors·Relay neurons: conduct nerve impulses within the CNS·Motor neurons: carry response information to the muscles
Relay Neurons
Nerve Impulse(See supplemental info)
http://outreach.mcb.harvard.edu/animations/actionpotential_short.swf
Homeostasis·Human body usually stays within certain limits for many physiological variables
- blood pH - CO2 concentration- body temp - blood glucose concen.- water balance w/in tissues
·Each variable has an expected value or set point- ie Body temp = 98.6 ℉ or 37 ℃
·Fluctuations above and below are inevitable
Negative feedback mechanisms·physiological changes that bring a value back closer to a set point·nervous system and endocrine system work together to ensure homeostatis
house example
Increased body temperature·exercise or high environmental temps
Sensed by Thermoreceptors·in skin
Hypothalamus receives info·in brain
Activated cooling mechanisms·increased activity of sweat glands leads to evaporative cooling effect of perspiration·dilation of arterioles in skin, fills capillaries with blood, allows heat to radiate out of skin
Sensory nerveMotor nerve
Homeostatic control of body temperature
Increased body temperature·exercise or high environmental temps
Sensed by Thermoreceptors·in skin
Hypothalamus receives info·in brain
Activated cooling mechanisms·increased activity of sweat glands leads to evaporative cooling effect of perspiration·dilation of arterioles in skin, fills capillaries with blood, allows heat to radiate out of skin
Sensory nerveMotor nerve
Homeostatic control of body temperature
Increased body temperature·exercise or high environmental temps
Sensed by Thermoreceptors·in skin
Hypothalamus receives info·in brain
Activated cooling mechanisms·increased activity of sweat glands leads to evaporative cooling effect of perspiration·dilation of arterioles in skin, fills capillaries with blood, allows heat to radiate out of skin
Sensory nerveMotor nerve
Homeostatic control of body temperature
Increased body temperature·exercise or high environmental temps
Sensed by Thermoreceptors·in skin
Hypothalamus receives info·in brain
Activated cooling mechanisms·increased activity of sweat glands leads to evaporative cooling effect of perspiration·dilation of arterioles in skin, fills capillaries with blood, allows heat to radiate out of skin
Sensory nerveMotor nerve
Homeostatic control of body temperature
Increased body temperature·exercise or high environmental temps
Sensed by Thermoreceptors·in skin
Hypothalamus receives info·in brain
Activated cooling mechanisms·increased activity of sweat glands leads to evaporative cooling effect of perspiration·dilation of arterioles in skin, fills capillaries with blood, allows heat to radiate out of skin
Sensory nerveMotor nerve
Homeostatic control of body temperature
Increased body temperature·exercise or high environmental temps
Sensed by Thermoreceptors·in skin
Hypothalamus receives info·in brain
Activated cooling mechanisms·increased activity of sweat glands leads to evaporative cooling effect of perspiration·dilation of arterioles in skin, fills capillaries with blood, allows heat to radiate out of skin
Sensory nerveMotor nerve
Homeostatic control of body temperature
Decreased body temperature·low environmental temps
Sensed by Thermoreceptors·in skin
Hypothalamus receives info·in brain
Activated warming mechanisms·stimulates skeletal muscles to shiver, generating body heat·constriction of arterioles in skin so blood is diverted to deeper tissues and less heat is lost
Sensory nerveMotor nerve
Control of Blood Glucose Concentration·Although other sugars exist in the blood, it is glucose that is most important and is monitored in order to maintain homeostasis·Levels rise after meals and are usually lowest in the morning before breakfast·If levels drop too low, hypoglycemia develops
- symptoms include lethargy, impaired mental function and irritability·If levels are too high, hyperglycemia develops
- symptoms include diabetes and its associated problems (eye, kidney, and nerve damage)
·Glucose levels are monitored by cells in the pancreas·If blood glucose drops to a dangerous level:
1) α cells (alpha) in pancreas produce glucagon, a hormone 2) glucagon activates liver and muscle cells to convert
glycogen to glucose (glycogenolysis) and thus raise blood sugar·If blood levels of blood sugar rise (either due to a meal or as a result of glycogen conversion)
1) β cells (beta) in pancreas produce insulin, a hormone2) insulin causes body cells to open protein channels and allow
glucose to diffuse into the cell by facilitated diffusion3) insulin causes the liver and muscle cells to convert
glucose to glycogen for storage
Diabetes
see supplemental info