Topic 6.5 – Nerves, Hormones & Homeostasis

6.5 From the Text:

Today’s Agenda: NEXT CLASS: Get a computer! Review this PowerPoint with a partner and take notes. Ask questions as needed Go to: http://tinyurl.com/65practice1 Practice with flashcards or a game NEXT CLASS: Hexagon activity-- will be a lab grade, so understand resting vs action potential Short quiz after 6.5.1 – State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses.

The nervous system consists of the central nervous system (CNS) and peripheral nervous systems (PNS), both of which are composed of neurons that carry electrical impulses. The CNS consists of the brain and spinal chord. The PNS consists of all of the other nerves. 6.5.1 – State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses. 6.5.1

6.5.1 – State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses. 6.5.1

Motor neurons are nerves that transmit signals to/from the brain and muscles/glands. [Draw/Label: dendrites, cell body with nucleus, axon, myelin sheath, nods of Ranvier & motor end plates] 6.5.2 – Draw and label a diagram of the structure of a motor neuron. Include dendrites, cell body with nucleus, axon, myelin sheath, nodes of Ranvier and motor end plates. 6.5.2

6.5.2 – Draw and label a diagram of the structure of a motor neuron. Include dendrites, cell body with nucleus, axon, myelin sheath, nodes of Ranvier and motor end plates. 6.5.2

Neurons that detect stimuli, receptors, such as pressure, heat, pain, etc. send signals to the CNS through sensory neurons. Relay neurons send signals within the CNS and motor neurons carry signals to effectors (muscles, glands) in response. These set of neurons (receptor, sensory, relay and motor neurons) makeup reflex-arcs. 6.5.3 – State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons. 6.5.3

Receptors (e.g. heat, pressure, light) Peripheral Nervous System Receptors (e.g. heat, pressure, light) Effectors (e.g. muscle tissues) Sensory Neurons Motor Neurons Central Nervous System Relay Neurons (within spine & brain) 6.5.3 – State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons. 6.5.3

6.5.3 – State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons. http://www.anatomypics.org/images/4159-reflex-arc.jpg 6.5.3

Recall that all cells have ion gradients across their cell membranes Recall that all cells have ion gradients across their cell membranes. The difference between the charges is called the electric potential and is measured in millivolts (mV). An resting potential is the potential when a neuron is not propagating an impulse. Usually around -70 mV An action potential is the localized reversal/restoration of the potential across a neuron membrane as it propagates an impulse. 6.5.4 – Define resting potential and action potential (depolarization and repolarization). http://droualb.faculty.mjc.edu/Course%20Materials/Physiology%20101/Chapter%20Notes/Fall%202011/chapter_4_Fall%202011.htm 6.5.4

In neurons, the resting potential is the result of differing concentrations of Cl- and inorganic ions. Movement of K+ and Na+ ions control the resting potential. At rest, the inner surface of the membrane has a negative charge and the outer surface has a positive charge. cell membrane 6.5.4 – Define resting potential and action potential (depolarization and repolarization). http://droualb.faculty.mjc.edu/Course%20Materials/Physiology%20101/Chapter%20Notes/Fall%202011/chapter_4_Fall%202011.htm 6.5.4

6.5.4 – Define resting potential and action potential (depolarization and repolarization). http://droualb.faculty.mjc.edu/Course%20Materials/Physiology%20101/Chapter%20Notes/Fall%202011/chapter_4_Fall%202011.htm 6.5.4

When a neuron is stimulated by an impulse, it creates an action potential by opening voltage-gated Na+ ion channels. Since [Na+] is higher outside of the axon, Na+ ions rush in and locally depolarize the cell. 6.5.5 – Explain how a nerve impulse passes along a non-myelinated neuron. Include the movements of Na+ and K+ ions to create a resting potential and an action potential. http://www.uic.edu/classes/bios/bios100/lectures/gated_channels.jpg http://people.eku.edu/ritchisong/301images/Neuron_action_potential.jpg 6.5.5

Local depolarization activates the neighboring Na+ channels, creating a moving action potential. When the potential in an area reaches +40 mV, the Na+ channels close and K+ channels open. K+ ions repolarize the region by decreasing the potential. The K+ gates close when the potential reaches -70mV. 6.5.5 – Explain how a nerve impulse passes along a non-myelinated neuron. Include the movements of Na+ and K+ ions to create a resting potential and an action potential. 6.5.5

6.5.5 – Explain how a nerve impulse passes along a non-myelinated neuron. Include the movements of Na+ and K+ ions to create a resting potential and an action potential. http://www.uic.edu/classes/bios/bios100/lectures/gated_channels.jpg 6.5.5

After the action potential has passed and the resting potential restored, sodium/potassium pumps return the Na+ and K+ ions to their original location (K+ = intracellular ; Na+ = extracellular) When finished, [Na+] is higher extracellularly and [K+] is higher intracellularly. The resting potential returns to the resting value of about -70 mV. 6.5.5 – Explain how a nerve impulse passes along a non-myelinated neuron. Include the movements of Na+ and K+ ions to create a resting potential and an action potential. 6.5.5

6.5.5 – Explain how a nerve impulse passes along a non-myelinated neuron. Include the movements of Na+ and K+ ions to create a resting potential and an action potential. 6.5.5

6.5.5 – Explain how a nerve impulse passes along a non-myelinated neuron. Include the movements of Na+ and K+ ions to create a resting potential and an action potential. http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter8/animation__the_nerve_impulse.html 6.5.5

What would result in the following changes in potential? 6.5.5 – Explain how a nerve impulse passes along a non-myelinated neuron. Include the movements of Na+ and K+ ions to create a resting potential and an action potential. 6.5.5

6.5.5 – Explain how a nerve impulse passes along a non-myelinated neuron. Include the movements of Na+ and K+ ions to create a resting potential and an action potential. 6.5.5

For extra review of impulse transmission, refer to the website below For extra review of impulse transmission, refer to the website below. Don’t let the title stop you!! http://www.dummies.com/how-to/content/understanding-the-transmission-of-nerve-impulses.html 6.5.5 – Explain how a nerve impulse passes along a non-myelinated neuron. Include the movements of Na+ and K+ ions to create a resting potential and an action potential. 6.5.5

Synaptic transmission involves passage of an impulse from one neuron to another through the synaptic cleft. When an action potential reaches a synapse at the end of an axon, it causes the membrane there to depolarize. This results in Ca2+ voltage-gated channels there to open, allowing Ca2+ to diffuse into the cell. Increased levels causes vesicles to release neurotransmitters into the cleft via exocytosis . 6.5.6 – Explain the principles of synaptic transmission. Include the release, diffusion and binding of the neurotransmitter, initiation of an action potential in the post-synaptic membrane, and subsequent removal of the neurotransmitter. 6.5.6

The neurotransmitters cross the cleft and bind to extracellular receptors on the receiving cell’s membrane, which induces depolarization or hyperpolarization. 6.5.6 – Explain the principles of synaptic transmission. Include the release, diffusion and binding of the neurotransmitter, initiation of an action potential in the post-synaptic membrane, and subsequent removal of the neurotransmitter. 6.5.6

Neurotransmitter molecules remaining in the synaptic cleft are removed by either being reabsorbed into the pre-synaptic neuron or by being broken down by enzymes. Doing this prevents transmitted impulses from being continuously transmitted to the post-synaptic neuron. A common transmitter is acetylcholine which is broken down by acetyl cholinesterase. 6.5.6 – Explain the principles of synaptic transmission. Include the release, diffusion and binding of the neurotransmitter, initiation of an action potential in the post-synaptic membrane, and subsequent removal of the neurotransmitter. 6.5.6

6.5.6 Synaptic transmissions can be either inhibitor or excitatory. Excitatory signals move the post-synaptic membrane potential closer to the threshold value, making it more likely for an action potential to occur. Inhibitory signals move the post-synaptic membrane potential away from the threshold value, making it less likely for an action potential to occur 6.5.6 – Explain the principles of synaptic transmission. Include the release, diffusion and binding of the neurotransmitter, initiation of an action potential in the post-synaptic membrane, and subsequent removal of the neurotransmitter. 6.5.6

The endocrine system works with the nervous system to maintain homeostasis. It consists of glands that release hormones that are transported in the blood. Cells with specialized hormone receptors react to the hormones as they flow through the bloodstream. These are the hormones’ target cells. 6.5.7 – State that the endocrine system consists of glands that release hormones that are transported in the blood. The nature of action of hormones or direct comparisons between nerve and endocrine systems are not required. 6.5.7

Homeostasis involves the maintenance of internal conditions within acceptable limits, despite fluctuations in the external environment. Ideal conditions are essential for cell/organ survival. Maintained conditions include blood pH, CO2 concentration, glucose levels, body temperature and H2O balance. 6.5.8 – State that homeostasis involves maintaining the internal environment between limits, including blood pH, carbon dioxide concentration, blood glucose concentration, body temperature and water balance. The internal environment consists of blood and tissue fluid. 6.5.8

Maintaining homeostasis involves monitoring levels of variables and correcting changes in levels via negative feedback mechanisms. Sensory cells detect deviations from desired values and relay information to the CNS, which activates mechanisms designed to bring the value back to normal. 6.5.9 – Explain that homeostasis involves monitoring levels of variables and correcting changes in levels by negative feedback mechanisms. 6.5.9

Thermoregulation is the control of body temperature through various mechanisms in response to both internal and external changes. The general desired temperature is around 98.2 – 98.6oF. Methods of thermoregulation (cooling and heating) include… 6.5.10 – Explain the control of body temperature, including the transfer of heat in blood and the roles of the hypothalamus, sweat glands, skin arterioles and shivering. 6.5.10

Arterioles in the skin dilate which increases blood flow to the skin Arterioles in the skin dilate which increases blood flow to the skin. The skin becomes warmer and more heat is lost from blood to the environment. Sweat glands produce sweat which carries away heat energy when its phase changes from liquid to gas. (recall properties of water from Topic 3). 6.5.10 – Explain the control of body temperature, including the transfer of heat in blood and the roles of the hypothalamus, sweat glands, skin arterioles and shivering. 6.5.10

Decreasing metabolism decreases the amount of energy produced by the body. Some species have behavior adaptations. Dogs will dig into the cooler dirt to lay in. Rodents retreat into burrows. Birds and other animals will bathe or idle in water. 6.5.10 – Explain the control of body temperature, including the transfer of heat in blood and the roles of the hypothalamus, sweat glands, skin arterioles and shivering. 6.5.10

Shivering increases the rate and number of muscle contractions, which produce heat as a byproduct. Vasoconstriction involves the contraction of blood vessels in the skin, decreasing blood flow there. The skin cools, which reduces heat lost to the environment. 6.5.10 – Explain the control of body temperature, including the transfer of heat in blood and the roles of the hypothalamus, sweat glands, skin arterioles and shivering. 6.5.10

Glucose concentration in the blood is primarily controlled by two antagonistic pancreatic hormones: insulin and glucagon. Within the pancreas, chemoreceptors located in islets of Langerhans detect blood glucose levels. 6.5.11 – Explain the control of glucose concentration including the roles of glucagon, insulin and alpha and beta cells in the pancreatic islets. The effects of adrenaline are not required here. http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/pancreas/islets.jpg 6.5.11

When glucose levels are too low, alpha cells in the pancreatic islets secrete glucagon, which is a protein hormone that targets cells in the liver. There, hepatocytes respond by converting stored glycogen into glucose and releasing it into the blood stream. 6.5.11 – Explain the control of glucose concentration including the roles of glucagon, insulin and alpha and beta cells in the pancreatic islets. The effects of adrenaline are not required here. 6.5.11

When glucose levels are too high, beta cells in the pancreatic islets secrete insulin, which enters the bloodstream. Muscle cells take in glucose through open glucose channels. Muscle and hepatocyte cells covert the glucose to glycogen. 6.5.11 – Explain the control of glucose concentration including the roles of glucagon, insulin and alpha and beta cells in the pancreatic islets. The effects of adrenaline are not required here. 6.5.11

6.5.11 Glucose Concentration Control HIGH GLUCOSE LOW GLUCOSE Protein Hormone Insulin Glucagon Target Cells Muscle Cells Liver Cells Fat Cells Hepatocytes (liver cells) Response Increased glucose uptake; Conversion of glucose to glycogen/fat Conversion of glucagon to glucose and release into bloodstream Result Decrease in glucose levels Increase in glucose levels 6.5.11 – Explain the control of glucose concentration including the roles of glucagon, insulin and alpha and beta cells in the pancreatic islets. The effects of adrenaline are not required here. 6.5.11

Diabetes is a metabolic disorder in which a person does not produce enough insulin or whose body does not properly react to insulin. This results in high glucose levels in blood. Increased levels glucose can result in damage to nerves, blood vessels, retinal tissue, coma and even death. 6.5.12 – Distinguish between type I and type II diabetes. http://www.diabetesandrelatedhealthissues.com/images/diabetes_symptoms.gif 6.5.12

Type I diabetes results when beta cells produce insufficient amounts of insulin. It is caused by an autoimmune disorder in which antibodies are produced that target insulin or beta islets within the pancreas. It is typically inherited and can be treated through regular insulin injections or pancreas transplantation. 6.5.12 – Distinguish between type I and type II diabetes. http://i.telegraph.co.uk/multimedia/archive/01571/diabetes_1571708c.jpg 6.5.12

Type II diabetes results when less insulin is produced AND when cells become less sensitive to insulin. It is thought to be caused by poor diet and increasing age. Can be treated by decreasing carbohydrate intake and increasing exercise. Medication can also be used to increase insulin production or decrease glucose levels. 6.5.12 – Distinguish between type I and type II diabetes. http://www.topnews.in/health/files/Type-2-Diabetes.gif 6.5.12

6.5.12 – Distinguish between type I and type II diabetes.