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Human Systems

Human Systems. Nervous, Endocrine, Reproductive . The Nervous System. OH MY!!!. The Mad Mad Neuron Competition!!!. Nervous system pathway is a one way road from dendrite to synaptic terminals. Functions. Dendrites: receive signals Axon: transmits signals

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Human Systems

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  1. Human Systems Nervous, Endocrine, Reproductive

  2. The Nervous System OH MY!!!

  3. The Mad MadNeuron Competition!!!

  4. Nervous system pathway is a one way road from dendrite to synaptic terminals.

  5. Functions • Dendrites: receive signals • Axon: transmits signals • Synapse terminals: location where neurotransmitters are released • Neurotransmitters: chemical messengers that travel out of the presynaptic neuron and into the postsynaptic neuron. • Ex: acetylcholine, epinephrine, norepinephrine, dopamine, serotonin, and GABA

  6. Neurons of Vertebrates & Most Invertebrates • Have cells that are helper cells to the neurons called: Glial or glia cells • Nourish neurons, insulate the axons, & regulate the extracellular fluid around the neurons. • Outnumber the neurons in the mammalian brain 10-50 fold. • During a synapse some neurotransmitters are sent to the glial cells to be metabolized for fuel

  7. Types of Glia Cells Astrocytes: facilitate info. Transfer at synapses & sometimes release neurotransmitters. cause nearby blood vessels to dilate enabling neurons to receive oxygen & glucose faster. They also regulate extracellular concentrations of ions & neurotransmitters. Schwann cells & oligodendrocytes: cover axons with a myelin sheath. Microglia: protect against pathogens.

  8. What is a nerve impulse? • Nerve impulse is misleading. We will call it an action potential instead • Can be measured in the same way as electricity is measured • Voltage • Millivolts • The conductor of a neuron is the axon • Is covered by a myelin sheath • Increases the rate at which an action potential passes down an axon.

  9. Resting potential • Area of a neuron that is ready to send an action potential but is not currently sending one. • This area is considered polarized • Characterized by the active transport of sodium ions (Na+ ) out of the axon cell& potassium ions (K+) into the cytoplasm. • There are negatively charged ions permanently located in the cytoplasm • This collection of charged ions leads to a net positive charge outside the axon membrane & negative charge inside.

  10. Neuron at Resting Potential

  11. Action Potential • Described as a self-propagating wave of ion movements in and out of the neuron membrane • This is the diffusion of the Na+ & the K+ . • Sodium channels open & then potassium ones do to. • This is the “impulse” or action potential • It is a nearly instantaneous event occurring in one area of the axon = depolarization • This area initiates the next area on the axon to open up the channels. • This action continues down the axon. • Once an impulse is started at the dendrite end that action potential will self-propagate itself to the far axon end of the cell.

  12. Return to Resting Potential • Remember that one neuron may send dozens of action potentials in a very short period of time. • Once an area of the axon sends an action potential it cannot send another until the Na+ & K+ have been restored to their positions at the resting potential. • Active transport is required to move the ions = repolarization • The time it takes for a neuron to send an action potential & then repolarize is called: the refractory period of that neuron.

  13. The Central Nervous system- CNS CONSISTS OF THE BRAIN AND SPINAL CORD Receive sensory information from various receptors & then interpret & process the information. If a response is needed some portion of the brain or spinal cord initiates a response = motor response. The cells that carry this information are neurons

  14. FUNCTIONS OF THE BRAIN

  15. Spinal Nerves: • There are 31 pairs • Emerge from the spinal cord • Some are motor nerves & some are sensory nerves • Cranial Nerves: • There are 12 pairs • Emerge from the brain stem of the brain • EX: optic nerve pair (carry visual information from retina to the brain)

  16. Typical Pathway of Nervous System Explain in as much detail as possible the pathway if you should touch something hot.

  17. As soon as you touched the pot of boiling water a sensory receptor began an action potential or “nerve impulse”. Each receptor in your body is designed to transform a particular kind of stimulus into an action potential There are a chain of neurons which take the impulse towards the CNS. In this case the spinal cord. Once at the spinal cord the action potential is routed to the appropriate area of the CNS for interpretation. During its stay in the CNS the action potential is carried by relay neurons. Your brain has now made the decision to remove your hand. Relay neurons send the action potential to the spinal cord & out one of the spinal nerve pairs (motor neuron). The motor neuron is taking the impulse/action potential to the muscle and a chemical signal is sent to the muscle which results in a contraction, moving your hand.

  18. Junction where a neuron sends a chemical to muscle tissue is called: motor end plate The name for the muscle (in this case) is the effector.

  19. How do neurons communicate with each other? This occurs through a chemical communication called a synapse. -examples of chemicals: acetylcholine, epinephrine, dopamine, norepinephrine, serotonin, and GABA Different communication synapse pattern may occur…

  20. 7.5 The neurotransmitters binding to the receptor protein initiates to ion channel opening and Na+ diffusing in which starts the action potential down the postsynaptic neuron 9.5 The neurotransmitter is broken down by enzymes & is released from the receptor protein. They will diffuse back across the synaptic gap. 9.75 Sodium channel closes Usually a ligand-gated channel

  21. Generations of Postsynaptic Potentials • Neurotransmitters which generate action potentials are known as Excitatory Neurotransmitters. • Cause Na+ to diffuse into the postsynaptic neuron • EX:acetocholine • Neurotransmitters which prohibit action potentials are known as Inhibitory Neurotransmitters. • Causes hyperpolarization of a neuron by allowing Cl- move across postsynaptic cell into the membrane or cause K+ to move out of the postsynaptic cell • EX: GABA

  22. Acetylcholine • Common neurotransmitter to vertebrates & invertebrates. • Helps with muscle stimulation, memory formation, learning, heart rate, energy level. • Released by motor neurons • If it remained in the synapse, the postsynaptic neuron would keep “firing” indefinitely. • Acetylcholinesterase breaks down the acetylcholine in the synapse. • Read article about acetylcholine and nicotine

  23. Decision making • A neuron is on the receiving end of many excitatory and inhibitory stimuli. • The neuron sums up the signals • If the sum is excitatory the axons will “fire” • If the sum is inhibitory the axons will not • The summation of the messages is the way decisions are made by the central nervous system.

  24. Controlling the Signaling System • Some synapses have neurotransmitters bind to metabotrophic receptors instead of ion channels • Activates a signal transduction pathway in the postsynaptic neuron involving a 2nd messenger. • Have a slower onset but last longer • Modulate the responsiveness of postsynaptic neurons in diverse ways. • EX: altering the number of open channels

  25. THE MOUSE PARTY

  26. The Nervous System & The Endocrine System Work cooperatively in order to ensure homeostasis.

  27. The Endocrine System Glands that secrete hormones as a chemical signal which is sent to different parts of your body. Helps maintain homeostasis

  28. What are hormones? • Chemical messengers that have a physiological effect far from where they originated. • They travel through the bloodstream • Most are under the control of a negative feedback mechanism. • Exceptions: oxytocin

  29. Homeostatic control of body temperature Negative feedback: physiological changes that bring a value back closer to a set point. Message is sent by thermoreceptors

  30. Maintaining Blood Glucose Levels • Our cells rely on glucose for cellular respiration • Therefore our cells are acting to lower the glucose in our blood • The increase and decrease of our glucose levels never stops • From the villi in the intestines glucose is passed the capillary beds into the hepatic portal vein which takes the blood directly to the liver where the glucose is converted to glycogen.

  31. Maintaining Blood Glucose Levels • The hepatic portal vein is the only major blood vessel where the blood glucose concentration changes in large degrees. • Other blood vessels receive the blood after it has been acted upon by the hepatocytes (liver cells ) • Hepatocytes take direction by two hormones: • Insulin • glucagon Both produced in the pancreas & have opposite effects on blood glucose concentrations

  32. INSULIN • Produced by β(beta) cells in the pancreas when blood glucose levels are high. • It “hooks up” with body cells & causes them to open protein channels which allow the glucose to diffuse (facilitated) into the cells • In the liver & muscles, insulin stimulates the hepatocytes to take in glucose and convert it to glycogen.

  33. GLUCAGON • Produced by α(alpha) cells in the pancreas when blood glucose levels are low. • When released into the bloodstream this molecule stimulates the hydrolysis the granules of glycogen in the liver cells and muscles cells.

  34. Maintaining Blood Glucose Levels

  35. Diabetes • A disease characterized by hyperglycemia • High blood glucose

  36. Difference between neurotransmitters & endocrine signals • Neurotransmitters: usually small, nitrogen-containing compounds that are conveyed from one specialized nerve cell to another along specific nerve highways throughout the body & are designed to elicit immediate responses. • Endocrine signals: usually hormone secreted from glands that use blood vessels to disperse their signal molecules, to elicit a slower response.

  37. Types of Hormones & Their Function • Steroid hormones: • Example is estrogen • Function: increases thickness of uterine lining • Peptide hormones: • Example is insulin • Function: stimulates glucose uptake by body cells • Tyrosine Derivative hormone: • Example is thyroxin • Function: increases metabolic rate

  38. Steroid Hormones • Synthesized from cholesterol & classified as lipids • Easily passes through cell membrane • Once in cytoplasm binds with receptor protein • Forms hormone receptor complex • Then passes through nuclear membrane & binds to certain genes • It will then either inhibit or induce transcription • They control the production of proteins in a target cell

  39. Peptide Hormones • Are protein molecules • When it reaches its target cell it binds with a receptor protein on the outer surface of the cell • No receptor protein on surface of cell it isn’t a target cell • A secondary messenger molecule is triggered into action in the cytoplasm • Never enter the cell

  40. Major Endocrine Glands Sometimes the glands come in pairs… Sometimes they are alone…

  41. Hypothalamus & The Pituitary Gland • Hypothalamus largely controls the pituitary gland The anterior & posterior lobes of the pituitary gland communicate differently with the hypothalamus The pituitary gland is actually a pair Anterior & posterior lobes

  42. Posterior lobe of the pituitary gland Contain axons of cells called neurosecretory cells that extend from the hypthalamus to the posterior lobe of the pituitary These hormones are produced within the hypothalamus but secreted from the posterior pituitary.

  43. Anterior Lobe of The Pituitary Gland Hormones (called releasing hormones) produced in the hypothalamus are transported through capillary beds to the portal vein which goes to the anterior pituitary. These hormones target cells are the anterior pituitary cells They cause the anterior pituitary to secrete specific hormones

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