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Date Created: 01/31/16
Biology Chapter 33 1/31/16 1:25 PM ▯ Form/ function ▯ Homeostasis ▯ Feedback- have ways to regulate our body (body temp, hormones) Positive and negative feedback ▯ ▯ Animal Nutrition and the Digestive System: a. Digestion is compartmentalized b. As animals become more complex they become more compartmentalized c. Cells become Specialization Herbivores- live entirely on plant material> Carnivores- eat only meat Omnivores- feed upon animal and plant material (we are omnivores) Animal Forms: Sponge- is the simplest organism= very simple but have specialization Gastrovasular system- incomplete system= food in one way and out the same way o Gastro= digestion o Vascular= circulation Cnidarians and flat worms- only have one opening ▯ a. A gastrovascular cavity has a single opening through which food is ingested and waste is excreted, as shown in this hydra and in this jellyfish medusa. b. An alimentary canal has two openings: a mouth for ingesting food, and an anus for eliminating waste, as shown in this nematode. c. Accessory digestive glands= aid in digestion but are not part of the digestive system Parts of the Digestive System: a. Oral Cavity: Digestion begins in the oral cavity Mechanical and chemical digestion Chewing The tongue: o Tastes o Shapes food into a ball called a bolus o Moves bolus towards the pharynx Salivary glands release o A glycoprotein that moistens and lubricates food o Buffers that neutralize acids o Salivary amylase – an enzyme that begins the hydrolysis of starch o Antibacterial agents that kill some bacteria ingested with food o Lingual lipase – triglycerides broken down; released by tongue b. Peristalsis: i. Peristalsis moves food through the esophagus into the stomach ii. Epiglottis- opens when breathing and closes when swallowing (esophageal sphincter) iii. Esophagus- contracts and relaxes to move food down tube(peristalsis) tube to connect oral cavity to stomach iv. Sphincters- rings of muscle that open and close to allow food to move into the next chamber and step in digestion c. Stomach: i. Contents of the stomach is a pH of 2 1. Very acidic ii. Some chemical digestion occurs in the mouth iii. Gastric juice – consists of 1. Mucus 2. Protein-digesting enzyme 3. Strong acid – pH of around 2 o Ulcers- where the acid begins to eat away at the stomach sides i. Pepsinogen (inactive form of pepsin) and HCl are secreted into the lumen of the stomach ii. HCl converts pepsinogen into pepsin iii. Pepsin helps activate more pepsinogen Pepsin begins the chemical digestion of proteins Mucus protects the stomach form the acid Chyme- the stomach acid and the food (pyloric sphincter allow the food that is able to enter the small intestine d. Small Intestine: i. Major organ of chemical digestion and absorption ii. Chyme mixes with digestive juices from the pancreas, liver, and gland cells in the intestinal wall 1. Pancreas- organ responsible for insulin and releases enzymes into the small intestine iii. pH goes to around a pH of 8 (alkaline pH) iv. The small intestine is well adapted for absorption v. Surface area increased by o Folds in the intestinal lining o Fingerlike projections called villi o Tiny projections on the surface of the intestinal cells called microvilli (on top of the villi) e. Large Intestine: i. Also called the colon ii. Has a pouch (cecum) near its junction with the small intestine which bears the appendix iii. Contains large populations of E. coli which produce important vitamins (good until gets where it shouldn’t be)(largest colony of bacteria in the body) (Antibiotic can kill of these bacteria) iv. Absorbs these vitamins and water into the blood stream v. Helps form feces which are stored in the rectum until elimination vi. Appendix is on the Cecum on the Colon- pain in right side that hurts ▯ Food processing occurs in four stages: ▯ Ingestion- how food gets in system ▯ Digestion- how we get nutrients (chemical and mechanical) ▯ ▯ Absorption- nutrients move into blood stream ▯ Elimination- get rid of food ▯ Know names of enzymes: ▯ ▯ ▯ Carbohydrates: ▯ a. Digestion of carbohydrates is performed by several enzymes. Starch and glycogen are broken down into glucose by amylase and maltase. Sucrose (table sugar) and lactose (milk sugar) are broken down by sucrase and lactase, respectively. ▯ ▯ Proteins: a. Protein digestion is a multistep process that begins in the stomach and continues through the intestines. ▯ ▯ ▯ ▯ ▯ Lipids: Lipids are digested and absorbed in the small intestine Mechanical and chemical digestion of food takes place in many steps, beginning in the mouth and ending in the rectum ▯ Neurons and Nervous Systems a. Neuron – Functional cells in nervous system Glial cells support neurons and maintain their environment. Glial cells of the (a) central nervous system include oligodendrocytes, astrocytes, ependymal cells, and microglial cells. Oligodendrocytes form the myelin sheath around axons. Astrocytes provide nutrients to neurons, maintain their extracellular environment, and provide structural support. Microglia scavenge pathogens and dead cells. Ependymal cells produce cerebrospinal fluid that cushions the neurons. Glial cells of the (b) peripheral nervous system include Schwann cells, which form the myelin sheath, and satellite cells, which provide nutrients and structural support to neurons. ▯ Nervous systems have two main anatomical divisions: 1. The central nervous system (CNS) consists of the brain and spinal cord (vertebrates) 2. The peripheral nervous system (PNS) is located outside the CNS and consists of nerves (bundles of neurons wrapped in connective tissue) and ganglia clusters of cell bodies ▯ The nervous system must: Collects/ Obtains sensory information, sensory input Processes sensory information, integration Sends commands to effector cells (muscles and glands) that carry out appropriate responses, motor output Nervous system discriminates to what to respond to and not to respond to. ▯ Functions of the Nervous System: ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ Components Of the Nervous System: 1. Sensory neurons Convey signals from sensory receptors to the CNS 2. Interneurons Located entirely in the CNS and they integrate information and send it to the motor neurons 3. Motor neurons Convey signals to effector cells ▯ ▯ Simple Reflex Arc: ▯ Demonstrates the ▯ relationship between ▯ neurons and nervous ▯ system structure and ▯ function. ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ Neuron Functions: a. Action potential o Threshold o Depolarization o Repolarization o Hyperpolariztion b. Propagation and synapse ▯ ▯ Resting Potential= unstimulated All neurons have a charge ▯ ▯ Inside Neuron: Large proteins and more potassium ions and sodium ions (both negatively charged) ▯ Outside Neuron: More Sodium ions and potassium (both negatively charged) ▯ ▯ Neurons have channels that allows things to pass through, channels allow for other molecules to pass through. Channels allow only potassium to move through, sodium can move in. Movement of potassium outside the cell than sodium that moves into the cell. Active Transport system: Na/ K pump moves against ▯ Moves more Na out than K in ▯ ▯ In order for a neuron to be stimulated= it has to be at resting potential ▯ ▯ ▯ ▯ ▯ Gated Channels: the channels have a cover and block things from entering the channel Channels are closed, neither Na or K can pass through channel Additional openings allow Na to enter the channels o Depolarization: When the neuron becomes less negative If the stimulus is strong enough: the neuron will reaction with an action potential A stimulus is any factor that causes a nerve signal to be generated A stimulus o Alters the permeability of a portion of the neuron membrane o Allows ions to pass through o Changes the membrane’s voltage After reacting threshold= neuron will become positive and the channel openings open up o Repolarization: when the potassium channels open up and allow for K to move out Hyperpolarization: when the neuron hyper polarizes and neuron is more negative than then during resting potential Refracting Period: the point at which the nerve cannot be stimulated A nerve signal, action potential, is o A change in the membrane voltage o From the resting potential o To a maximum level, and o Back to the resting potential Propagation: movement of action potential down a neuron which causes the other areas to reach the action potential and then they reach the end axis where they have to decide if the response goes further ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ The formation of an action potential can be divided into five steps: ▯ (1) A stimulus from a sensory cell or another neuron causes the target cell to depolarize toward the threshold potential. (2) If the threshold of excitation is reached, all Na channels open and the membrane depolarizes. + + (3) At the peak action potential, K channels open and K begins to leave the cell. At the same time, Na channels+ close. + (4) The membrane becomes hyperpolarized as K ions continue to leave the cell. The hyperpolarized membrane is in a refractory period and cannot fire. (5) The K channels close and the Na /K transporter restores the resting potential. ▯ Propagation: Action potential- K moves out and Na moves into neuron down the axon (moves from dendrites to soma down axon to axon terminal) Myelin sheath- covers up part of the neuron and can not be stimulated Area with out the myelin sheath can be stimulated o The myelin sheath speeds up action potential because the stimulus jumps over the sheath ▯ Synapse: Synapse are relay points between a synaptic terminal or sending neuron and receiving cell The receiving cell can be: o Another neuron o An effector cell Chemical Synapse: o Ending(presynaptic o ▯ Neurons and Nervous Systems: ▯ Action potentials are: a. Self-propagated in a one-way chain along a neuron b. All-or-none events c. Threshold versus non-threshold d. Frequency of action potentials, but not their strength changes with the strength of the stimulus ▯ Neuron has to be at the resting potential in order to be stimulated. ▯ After a neuron become stimulated the neuron will depolarize. K in; Na out. ▯ Na, K pump deals with active potential ▯ Synapse are relay points between a synaptic terminal of a sending neuron and a receiving cell ▯ The receiving cell can be: Another neuron An effector cell such as a muscle cell or endocrine cell ▯ A decision has to be made here- discrimination (highly sophisticated thing) either the action potential dies there or it goes on to another neuron ▯ Neurons do not physically touch each other- they are across from each other ▯ Chemical synapses (neurotransmitters): The ending (presynaptic) cell secretes a chemical signal, a neurotransmitter The neurotransmitter crosses the synaptic cleft The neurotransmitter binds to a specific receptor on the surface of the receiving (postsynaptic) cell ▯ Neurotransmitters are contained in these balls and the vesicles fuse with each other and move to the surface of the axon. ▯ Presynaptic neuron ▯ Postsynaptic neuron- opens up gates of Na to allow to exit the neuron ▯ When Na moves in- depolarized ▯ Hyperpolarizes- goes below the resting potential because it is losing the positively charged K- cant be stimulated ▯ ▯ enzymes are released with the neurotransmitters ▯ Some neurotransmitters Excite a receiving cell (E.P.S.P) excited postsynaptic potential Inhibit a receiving cell (I.P.S.P.) inhibitory post synaptic potential ▯ A receiving neuron’s membrane may receive excitatory and inhibitory signals from different sending neurons ▯ ▯ The summation of excitation and inhibition determines if a neuron will transmit a nerve signal ▯ ▯ A single neuron can receive both excitatory and inhibitory inputs from multiple neurons, resulting in local membrane depolarization (EPSP input) and hyperpolarization (IPSP input). All these inputs are added together at the axon hillock. If the EPSPs are strong enough to overcome the IPSPs and reach the threshold of excitation, the neuron will fire. A neuron can be an EPSP or an IPSP- depends on the neurotransmitters ▯ Neurons and Nervous Systems: ▯ Overview: The flow of information in the nervous system relies on synaptic integration; how many neurons are organized in the body The brain has thousands and thousands of neurons arranged in blocks all receiving either excitatory or inhibitory signals There are divergent circuits-neurons in one block fan out to form connections with other blocks There are also convergent circuits-signals from many blocks are relayed to a few blocks Evolutionary Trends: Invertebrates= less complex that vertebrates ▯ Trends to look for: a. Whole body response to more local response b. Cephalization – the formation of a head c. Specialized functions of sensory, integrating, and responding Brain is part of the central nervous system ▯ Radial symmetrical animals have: a nervous system arranged in a web like system of neurons called a nerve net ▯ Most bilaterally symmetrical animals evolved: Cephalization – the concentration of the nervous system at the head end Centralization – the presence of a central nervous system distinct from a peripheral \nervous system Presence of ganglia ▯ ###Study the Power Point Diagram### ▯ ▯ The PNS can be divided into two functional components ▯ Motor system – mostly voluntary ▯ Autonomic nervous system – mostly involuntary ▯ The motor nervous system Carries signals to and from skeletal muscles Mainly respond to external stimuli ▯ The autonomic nervous system Regulates the internal environment Controls smooth and cardiac muscle and organs and glands of the digestive, cardiovascular, excretory, and endocrine systems The sympathetic and parasympathetic nervous systems often have opposing effects on target organs. Hormones and the Endocrine System: Consist of all hormone- secreting cells Works with the nervous system in regulating body activities Hormone system takes longer than the endocrine system to respond Chemical Messengers: Hormones- endocrine glands and some neurons Neurotransmitters- end of axons Local signaling molecules- release by a variety of cells Pheromones- secretions of exocrine glands (body odor) Hormones enter into the blood system and only certain cells will be affected by the hormones- only target tissues/ cells respond Hormones do not have their response with the entire body Hormone signaling involves three stages Reception – receptor protein on or in the target cell; if it stays on the surface of the cell, there are receptors to allow hormones to interact with it. If the hormone enters the cell, there is a receptor inside the cell to interact with the hormone Signal transduction – converts signal into some kind of response molecule Response – a change in the cell’s behavior Hormones exert their effects on specific cells called target cells; along with the nervous system coordinate and integrate activities Hormones are signaling molecules ligand- signal molecule Two groups of hormones Water-soluble includes proteins, short polypeptides and some modified amino acids; most hormones Lipid-soluble includes the steroid hormones, small molecules made from cholesterol Water soluble hormones cannot pass through membrane, so there must be a receptor on the surface of the membrane- they can make changes in the cell without ever entering the target cells The structures of peptide hormones (a) oxytocin, (b) growth hormone, and (c) folliclestimulating hormone are shown. These peptide hormones are much larger than those derived from cholesterol or amino acids. The amino acid-derived hormones epinephrine and norepinephrine bind to betaadrenergic receptors on the plasma membrane of cells. Hormone binding to receptor activates a G-protein, which in turn activates adenylyl cyclase, converting ATP to cAMP. cAMP is a second messenger that mediates a cell-specific response. An enzyme called phosphodiesterase breaks down cAMP, terminating the signal. Lipid-soluble hormones pass through the phospholipid bilayer and bind to receptors inside the cell An intracellular nuclear receptor (NR) is located in the cytoplasm bound to a heat shock protein (HSP). Upon hormone binding, the receptor dissociates from the heat shock protein and translocates to the nucleus. In the nucleus, the hormone-receptor complex binds to a DNA sequence called a hormone response element (HRE), which triggers gene transcription and translation. The corresponding protein product can then mediate changes in cell function. Response is very specific- an enzyme is synthesized A steroid hormone is lipid- soluble- will produce a new protein that alters the target cells function Vertebrate Endocrine System Endocrine glands- produce and secret hormones into blood stream Endocrine and nonendocrine function –hormones released into pancreas Stomach and heart have some cells that secrete hormones o Hormones are produced a lot of places in the body Hypothalamus/Pituitary Interaction The hypothalamus-blurs distinction between endocrine and nervous systems: Receives input from the nerves about internal conditions of the body and external environment Responds by sending out appropriate nervous and endocrine signals Uses the pituitary gland to exert master control over the endocrine system Involves nervous system nervous system= faster but doesn’t last long hormones= slower but last a lot longer Pituitary gland consists of two parts 1. Posterior pituitary Composed of nervous tissue Is an extension of the hypothalamus Stores and secretes oxytocin and ADH which are made in the hypothalamus OCT- reacts on the mammary glands and the uterus 2. The anterior pituitary Synthesizes and secretes hormones that control other glands Is controlled by two types of hormones released from the hypothalamus: o Releasing hormones - stimulate the anterior pituitary o Inhibiting hormone - inhibit the anterior pituitary Alcohol dehydrates the body Portal circulatory system- it is localized Regulation of Blood Glucose: Pancreas secretes two hormones that control blood glucose – antagonistic hormones Insulin – signals cells to use and store glucose- removes excess glucose from blood Glucagon – causes cells to release stored glucose into the blood LOOK AT POWERPOINT- slides 29- 31 Metamorphosis is controlled by the presence and amount of juvenile hormone and ecdysone. Optimal levels of ecdysone are needed for larva-to-larva and pupa-to-adult molts Optimal levels of juvenile hormone and ecdysone assures larva-to-larva molts. Metamorphosis regulates the life cycle of insects (hormones regulate insect life cycles)
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