Midterm Review PDF

Last class: Cell Signaling Signal transduction ◦ Second messenger Receptor Second ◦ Kinase messenger ◦ Phoshorylation Inactive re...

Last class: Cell Signaling Signal transduction ◦ Second messenger Receptor Second ◦ Kinase messenger ◦ Phoshorylation Inactive relay  protein Extracellular chemical messenger (first messenger) Active relay ☺ protein (protein  Effector kinase) protein Effector protein P (phosphorylated) ☺ Cellular response Last Class: Cell Signaling Lipid soluble ECMs can bind in the cell Receptor-hormone complex Gene expression ◦ Transcription and translation Other types of receptors ◦ Ligand gated ion channels ◦ Enzyme receptors ◦ Enzyme-coupled receptors ◦ G-protein coupled receptors Signal amplification and termination Last Class: Blood Erythrocytes (Red blood cells) ◦ Erythropoiesis (feedback loop) ◦ Blood types Leukocytes (white blood cells) ◦ Neutrophils ◦ Basophils ◦ Eosinophils ◦ Monocytes ◦ Lymphocytes Section 1: https://forms.gle/YnVxZtxWVfPJB2Gc6 Section 2: https://forms.gle/vAvDeAEa4S2CJH2x8 Review Questions Which of the following is false about cell signaling? ◦ Lipid soluble hormones can pass through the cell membrane ◦ The transcription of a gene involves making a copy of a DNA sequence (called mRNA) ◦ Signal termination always occurs once the first messenger dissociates from the receptor ◦ The binding of a single messenger to a receptor could result in the production of hundreds of second messengers A person with type A blood might be able to receive a transfusion containing which of the following blood types? (select all that are correct) ◦ Type A ◦ Type B ◦ Type AB ◦ Type O The Nervous System and Neuronal Excitability BI OL 1 2 1 6 – W K 3 CHA PT ER 7 DR. T R E VOR KI N G Learning Objectives Describe how membrane potential is produced and maintained Predict how a change in the system might impact membrane potential Recall the organization of the nervous system Differentiate the roles of different cells of the nervous system Describe how electrical signals in neurons are generated and propagated (graded and action potentials) Outline the process of signal transmission at synapses Identify the functions of neurotransmitters Distinguish the different neural circuits Divisions of the nervous system Central Nervous system (CNS) ◦ Brain and Spinal cord Peripheral Nervous System (PNS) ◦ Afferent division ◦ Efferent division Organization of the Nervous System Central Nervous system (CNS) ◦ Brain and Spinal cord Peripheral Nervous System (PNS) ◦ Afferent division ◦ Input into the CNS ◦ Efferent division ◦ Info from the CNS to effectors ◦ Somatic (voluntary): skeletal muscles ◦ Autonomic (involuntary): Smooth muscle, cardiac muscle, glands ◦ Sympathetic and parasympathetic Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Functions of the Nervous system Sensory ◦ detect external or internal stimuli, and relay sensory information to the brain and spinal cord Integrative ◦ CNS analyzes sensory information, and makes decisions for appropriate responses Motor ◦ Motor information is conveyed from the CNS through cranial and spinal nerves of the PNS to appropriate effectors (muscles and glands). Feedback loops! Cells of the nervous system By the end of this part, you will be able to: Discuss the structure and function of neurons List the roles of neuroglia Explain the importance of myelination Describe the ability to repair neurons of the CNS and PNS Neuron Structure: An overview Nerve cells/Neurons Soma (Cell body) ◦ Control centre ◦ Dendrite receives signals Axon ◦ Generate and propagate action potentials Axon Terminal ◦ communicates with other neurons/cells at synapse Neuron Function Sensory neuron Interneuron Motor neuron Compare this organization to a feedback loop Electrical signals in Neurons Many cells in the nervous system display ‘Electrical Excitability’ E.g. Follow the path of action potentials ◦ Sensory neuron ◦ Interneuron ◦ Cerebral cortex ◦ Motor cortex ◦ Motoneurons ◦ Muscle (also excitable) Neuroglia Astrocyte Make up half the volume of the CNS Nourish and protect neurons Neuroglia cannot generate or Oligodendrocyte propagate action potentials If injured, neuroglia fill spaces Astrocytes Microglial cell Ependymal cell Neuroglia CNS and PNS have different neuroglia E.g. formation and maintenance of myelin sheath CNS – Oligodendrocytes PNS – Schwann cell Myelin Sheath Electrical insulation ◦ Increases speed of conduction Nodes of Ranvier ◦ Gaps in the myelination Neuron Repair Plasticity ◦ Ability to change throughout life ◦ E.g. sprout new dendrites, change synaptic contacts Repair ◦ Regeneration after damage ◦ Neurons have limited ability to repair PNS repair occurs if… ◦ Cell body is still intact ◦ Schwann cell remains active (guides and stimulates regrowth) CNS has little or no ability to repair ◦ Typically permanent Clinical Connection: Multiple Sclerosis Disease that causes a progressive destruction of myelin sheaths of neurons in the CNS ◦ Multiple regions of myelin sheath deteriorate to scleroses (hardened scars) Slows then short-circuits action potential conduction Autoimmune disease Appears between ages 20 and 40 First symptoms ◦ Heaviness or weakness in muscles ◦ Abnormal sensations ◦ Double vision Brief remission, then attack every year or two ◦ Progressive loss of function interspersed with remission Checkpoint: Nervous System Sam senses the pressure of the pen using a ________ receptor/neuron, which is a component of the ______ division of the _______ nervous system. This information is relayed to the ______ nervous system, where it is passed to an ____ neuron. The brain _______ this information and decides that Sam must increase pressure on the pen using the ______ division of the nervous system. A _______ neuron tells the muscles of the hand to squeeze harder. All of this information is relayed via _____ potentials, which move quickly through the body because many axons are are _______ Electrical signals in Neurons: Ion channels Ion channels cause changes in membrane permeability ◦ Ions can flow down electrochemical gradients ◦ Resting membrane potential (difference in charges) changes ◦ Allows for electrical communication Remember: electrochemical gradient 4 types of ion channels that allow neurons to function: ◦ Leak channels ◦ Ligand-gated channels ◦ Mechanically gates channels ◦ Voltage gated channels Ion channels: Leak Leak channels have gates that randomly alternate between open and closed positions Ion channels: Ligand-gated A ligand-gated channel opens or closes in response to a specific ligand (chemical) stimulus. Ion channels: Mechanically-gated Mechanically-gated channels open or close in response to mechanical stimulation ◦ Mechanical stimulation may take on the forms of touch, pressure, tissue stretching, and vibration Ion channels: Voltage-gated A voltage-gated channel opens in response to a change in membrane potential (voltage) ◦ K+, Ca2+, Na+ ◦ Important for action potentials Membrane potential Voltage that exists across the plasma membrane ◦ The presence of the plasma membrane creates an unequal distribution of positive and negative changes. ◦ The unequal distribution of charge is measured in volts or millivolts Unstimulated neuron cells + + + -+ display a resting membrane + - - + - - potential of around -70 mV + - + - - + - - The inside of the cell - membrane is more This difference in charge across the - negatively charged membrane is called polarization than outside Membrane potential The difference in charges across a membrane Inside Cell Outside Cell Simplification: + ◦ Charge on inside + + ◦ 5 positive, 3 negative + + ◦ 5-3 = +2 + - + ◦ Charge on Outside + - ◦ 6 positive, 3 negative + ◦ 6-3 = +3 - - - - ◦ Membrane potential is difference in charges + ◦ Inside charge minus outside charge + ◦ (+2) – (+3) = -1 ◦ The membrane is more positive outside the cell +2 +3 than inside, therefore the membrane potential is negative ◦ Most neuron cells -70 mV Inside is more negative (less positive) than outside Determinants of resting membrane potential 1. Unequal distribution of ions in the ECF and cytosol 2. Action of the Na+/K+ ATPase ◦ 3 Na+ out and 2 K+ in 3. Differences in membrane permeability ◦ More K+ leak channels than Na+ leak channels Membrane potential: + Hypothetical K leak channel only cell 1. Na+/K+ pump creates K+ concentration gradient Hypothetical cell begins with no membrane potential 2. K+ would flow out (down concentration Concentration gradient) K+ leak Outside cell + Electrical channel Voltage: -90mV K+ 3. electrical gradient would increase, - wanting to flow back into the cell Inside cell K+ K+ K+ 4. Eventually, the electrical gradient and K+ K+ concentration gradient would be equal: equilibrium potential K+ K+ K+ K+ 5. K+ equilibrium potential close to resting membrane potential What does that indicate? Membrane potential: + Hypothetical Na leak channel only cell 1. Na+/K+ pump creates Na+ concentration Na+ Na+ Na+ gradient Hypothetical cell begins with no Na+ membrane potential Na+ 2. Na+ would flow in (down concentration Na+ Na+ Na+ Concentration Na+ gradient) Na+ leak Outside cell - Electrical channel Voltage: +60mV 3.Na+ electrical gradient would increase, + wanting to flow back out of the cell Inside cell 4. Eventually, the electrical gradient and concentration gradient would be equal: equilibrium potential 5. Na+ equilibrium potential is NOT close to resting membrane potential What does that indicate? Membrane potential: Typical cell Membrane is more permeable to K+ ◦ Still leak of Na+ into cell Na+ Na+ Electrochemical gradient Na+ K+ Electrochemical gradient Na+ Na+ Na+ More net movement of positive charge out the cell + Outside cell - Inside cell Na+/K+ ATPase balances the Na+ leak in and K+ leak out K+ K+ K+ K+ K+ ◦ Maintains electrochemical gradient of K+ each NOT at equilibrium potential What is required? Checkpoint What would happen to membrane potential in the following hypothetical situations? ◦ A cell has more Na+ leak channels than usual ◦ Increased K+ leak channels ◦ The Na+/K+ pump was blocked (stopped working) The Nervous System and Neuronal Excitability BI OL 1 2 1 6 – W K 4 – L 1 CHA PT ER 7 DR. T R E VOR KI N G Reminder Midterm Thursday Oct 3 ◦ In class (paper) ◦ 75 minutes ◦ MC and SA ◦ Content: Weeks 1 - 4 Last class: structure and function of nervous system CNS and PNS Neurons ◦ Action potentials Neuroglia ◦ Myelin sheath 4 types of ion channels that allow neurons to function: ◦ Leak channels ◦ Ligand-gated channels ◦ Mechanically gates channels ◦ Voltage gated channels Last class: Membrane potential The difference in charges across a membrane Inside Cell Outside Cell ◦ Inside charge minus outside charge ◦ (+1) – (+4) = -3 + + + ◦ In resting neurons, the membrane is more positive outside the cell than inside, therefore + - the membrane potential is negative + + + - ◦ Most neuron cells -70 mV + ◦ Difference in ion distribution - - + - - ◦ Na+/K+ pump + + ◦ Leak channels +1 +4 Section 1: https://forms.gle/yJmeANHfbCD9sPsX8 Section 2: https://forms.gle/rbqeiDq3kgC6DAhM9 Question: Membrane potential Sensory receptors are part of which component of the nervous system? ◦ Afferent ◦ Motor neurons ◦ Central nervous system ◦ Autonomic How would the following situations change the membrane potential of a neuron? ◦ Opening of voltage-gated K+ channels ◦ Opening of Cl- channels to allow entrance into the cell ◦ Closing of Na+ leak channel ◦ Addition of more negatively charged proteins to the cytosol of a cell Graded potentials What is a graded potential? ◦ A small deviation from resting membrane potential (less or more negative) that occurs in dendrite and cell body ◦ Graded because the amplitude varies Depolarizing ◦ Makes the membrane potential less polarized Hyperpolarizing ◦ Makes the membrane potential more polarized Graded potential spreads out along dendrite and cell body, decreasing strength with distance Dendrites and cell body in blue Ion channels and graded potentials Graded potential occurs when Positive ions move in mechanically gated or ligand gated (depolarizing) channels open or close ◦ E.g. sensory neurons, dendrites Positive ions move in (depolarizing) Negative ions move in (hyperpolarizing) Stimulus strength The amplitude of a graded potential depends on the stimulus strength ◦ E.g. small knock vs. hard stubbing of toe Summation of graded potentials When two or more graded potentials add together Summated membrane potential Resting potential Stimulus 1 Stimulus 2 Action Potentials Neuron communicate cell to cell via action potentials ◦ Changes in the charges across membrane that travel down the axon Stronger than graded potentials ◦ All or nothing After-hyperpolarization Generation of the action potential Threshold must be reached ◦ Typically –55mV A stimulus must be strong enough to depolarize the membrane to threshold Subthreshold stimulus ◦ Not strong enough Suprathreshold stimulus ◦ Stronger than necessary ◦ Although action potential itself is all-or- none Depolarizing phase After a stimulus reaches the threshold (from graded potentials) The rising of phase of the action potential. This occurs until the membrane potential goes up to +30mV © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Repolarizing phase The falling of phase of the action potential. This occurs until the membrane potential gets back to rest –70mV Repolarizing phase © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. After-hyperpolarizing phase After resting membrane potential is reestablished, the undershoot that is observed. Typically goes down to –90mV © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Channels and ion flow during an action potential: Resting state Na+ Inside more Na+ Na+ Na+ negative than Na+ Na+ Voltage gated outside Voltage gated Na+ Channel K+ Channel Potential -70 mV Activation Activation Inactivation gate closed gate open K+ K+ gate closed K+ K+ K+ Channels and ion flow during an action potential: Depolarization Na+ Depolarization Na+ Na+ Na+ threshold reached Na+ Na+ (-55mV) Na+ channel opens Na+ rushes in, making cytosol more positive Membrane potential: +30 mV Activation gate closed K+ K+ K+ K+ K+ Channels and ion flow during an action potential: Repolarization Na+ channel Na+ inactivation gates close K+ channels open and K+ leaves cell Inside become more negative Na+ activation gate closes and inactivation gate opens Membrane potential returns to -70 mV Na+ Na+ Na+ K+ K+ Na+ Na+ K+ K+ K+ Action potential propagation Action potential moves down axon ◦ Maintains strength (unlike graded potential) Na+ ions flooding in cause adjacent ion channels to open Creates a ‘wave’ of depolarization that travels down the axon Why doesn’t an action potential undergo decremental conduction?  Conduction velocity – how fast an action potential moves down an axon Current flow through ECF between Nodes, opening Conduction velocity Na+ channels Saltatory conduction Kinda slow ◦ Myelinated axons – few ion channels under myelin ◦ Faster than continuous conduction ◦ More efficient (less ATP) Saltat = leaping Synapse The point at which one neuron communicates with another neuron or a target tissue Chemical Synapses: Neurotransmitter Release Action 1 An action potential depolarizes potential the axon terminal. Axon terminal 1 Postsynaptic cell Neurotransmitter Release 1 An action potential depolarizes the axon terminal. 2 The depolarization opens voltage- gated Ca2+ channels and Ca2+ enters the cell. Axon terminal 1 Voltage-gated Ca2+ Ca2+ Ca2+ channel 2 Postsynaptic cell Neurotransmitter Release 1 An action potential depolarizes the axon terminal. 2 The depolarization opens voltage- gated Ca2+ channels and Ca2+ enters the cell. Axon terminal Synaptic 3 Calcium entry triggers exocytosis vesicle of synaptic vesicle contents. Ca2+ Ca2+ 1 3 2 Docking protein Postsynaptic cell Neurotransmitter Release 1 An action potential depolarizes the axon terminal. 2 The depolarization opens voltage- gated Ca2+ channels and Ca2+ enters the cell. Axon terminal 3 Calcium entry triggers exocytosis of synaptic vesicle contents. 4 Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell. 1 3 2 4 Receptor Postsynaptic cell Neurotransmitter Release 1 An action potential depolarizes the axon terminal. 2 The depolarization opens voltage- gated Ca2+ channels and Ca2+ enters the cell. Axon terminal 3 Calcium entry triggers exocytosis of synaptic vesicle contents. 4 Neurotransmitter diffuses across the synaptic cleft and binds with chemically gated Na+ channel. 1 3 5 Na+ rushes in an depolarizes the membrane 2 4 Receptor Postsynaptic 5 Why are most chemical cell synapses one way information transfer?  Neuron Function Neurotransmitters released from presynaptic neuron may depolarize the postsynaptic neuron, generating an excitatory postsynaptic potential (EPSP). Some neurotransmitters may block depolarization, generating an inhibitory postsynaptic potential (IPSP). How? Why? AP EPSP 0 Membrane potential (EPSP) (IPSP) -55 IPSP -70 Neuron Function – Summation Types Demo - Summation Multiple EPSPs in the postsynaptic neuron may summate to a threshold level to generate an AP. Summation may be spatial or temporal, and takes into account the number of EPSPs versus IPSPs. If the net summation of EPSPs and IPSPs is a depolarization that reaches threshold, then an action potential occurs at the trigger zone of the postsynaptic neuron https://www.youtube.com/watch?v=Pd0IQ-Nx8dM Neurotransmitter Receptor Types Ionotropic receptors function as ligand-gated channels Metabotropic receptors function through a G-protein Same neurotransmitter can have excitatory or inhibitory effects depending on the ion channel Termination of the signal Neurotransmitters must be degraded or removed in order to terminate the signal transduction Diffusion: neurotransmitters can diffuse away from synaptic cleft Enzymatic degradation: enzymes can break down neurotransmitters (e.g., acetylcholinesterase) Uptake by cells: taken back up by the neuron that released them or passed to neighbouring neuroglia (neurotransmitter transporters) © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Regulation of neurotransmitter release Presynaptic modulation can regulate neurotransmitter release, leading to either increased or decreased release LESS neurotransmitter release MORE neurotransmitter release Neural circuits Revisiting the Learning Objectives Describe how membrane potential is produced and maintained Predict how a change in the system might impact membrane potential Recall the organization of the nervous system Differentiate the roles of different cells of the nervous system Describe how electrical signals in neurons are generated and propagated (graded and action potentials) Outline the process of signal transmission at synapses Identify the functions of neurotransmitters Distinguish the different neural circuits BIOL 1216 – Human Physiology DR. TREVOR KING ASSISTANT PROFESSOR, HEALTH AND PHYSICAL EDUCATION What is this course? Physiology - The study of the functions of an organism and its constituent parts Human Physiology – How does the body work? Some subdisciplines ◦ Neurophysiology ◦ Cardiovascular Physiology ◦ Respiratory ◦ Exercise Physiology ◦ Pathophysiology Who am I? Exercise Physiology Cardiovascular Health and Function Athletic Performance  Who are you? Answer these questions (anonymous) https://forms.gle/fvKJYKDUCbKRUZfLA Why is Physiology Important for Everybody? https://forms.gle/4m4SxG9VCA2jMs3V6 What are the details I need to know? Assessment Details Weight Lecture midterms (80 min each) midterm 1 – Oct 3 15% midterm 2 – Nov 7 20% Lecture questions Completed at the beginning of most classes 5% (D2L and Google forms) Lab PowerPoint presentation (5%) 35% lab exam 1 (10%) lab exam 2 (10%) quizzes (6%) post lab assignments (4%) Lecture final exam (2 hour) Exam period (dec 11-21) 25% TOTAL 100% Textbook Human Physiology (2019), Bryan H. Derrickson (2nd edition). Wiley. (ISBN: 9781119497783) ◦ Useful? (yes) ◦ Necessary? (depends on note-taking, background, or research abilities) ◦ Lab uses textbook (A copy available in the lab) ◦ 1 Copy on reserve at library Online resources: WileyPLUS ◦ Not required, but useful Class Overview: Lecture Online Assignments Review followed by small participation quiz at start of each class If you participate in 80% of quizzes = 100% If sick and missing a few classes, let me know Goal: to see whether the info stuck, or whether I need to revisit ◦ On your team Streaming Classes via Google Meet Stream classes – see how it works ◦ Won’t be a replacement for in-class, but could use if needed meet.google.com/anr-nvsi-mgb Contact Me Email: [email protected] Office: U243F Office hours: Tuesdays 1 to 2 pm or by Appointment (can be virtual) Class Overview: Labs Labs Start Next Week (Wednesday or Thursday) See myMRU for your schedule Labs run by the biology department ◦ Contact your instructor for lab questions ◦ Your lab has its own D2L site Lab instructors ◦ Karen Sheedy (Lab Coordinator): [email protected] ◦ Valentine Brussee-Bohn: [email protected] ◦ Jessica Eggleton: [email protected] Learning Objectives for Today Identify common methodologies, foundational principles, and practical applications of physiology as a science Recognize foundational physiology concepts acquired from previous studies (reviewing chapters 2, 3, and 4, typically covered in high school) including: ◦ Homeostasis ◦ Acids and bases ◦ ATP ◦ Macronutrients ◦ Metabolism ◦ Cellular respiration ◦ Enzymes ◦ Ligand-protein interaction ◦ Components of the cell Physiology as a Science (Lab 1) The process of acquiring knowledge about some aspect of the natural world in a systematic way is known as the scientific method Make an observation Formulate a hypothesis Design an experiment to test your hypothesis Interpret the data The Quantitative Scientific Method Observation and question ◦ E.g. Schrutes → low levels of CVD Hypothesis ◦ Nitrates in beets Experiment ◦ Give nitrate supplements Results interpretation ◦ Supported → theory ◦ Not supported → new question Key themes in physiology Homeostasis Maintenance of relatively stable conditions in the body’s internal environment. Integration When several components work together to accomplish a particular function. Mechanism of action Explain how the body works by indicating the mechanisms that are involved Communication Cells of the body must communicate with one another in order for the body to function  Homeostasis Maintenance of relatively stable internal environment Body has many controlled variables that it wants to keep stable What are some important variables to control? https://education.wiley.com/content/shared/media/anatomy/3D_Interactives/3d_interactive_homeostasis.html  Homeostasis Example Variable to maintain (controlled): Body temperature maintained at 37 degrees 3. Start to sweat 37 ֯C 6. Start to shiver 1. Running outside 5. Come inside to cold AC Homeostasis Via Feedback Feedback system most common way to maintain homeostasis in controlled variable Receptor: ◦ Senses change Feedback loop Control centre: ◦ Evaluates whether outside the set point ◦ Output when needed Effector ◦ Produces response to change the controlled variable Homeostasis Via Feedback Feedback loop is a cycle of events in which a parameter of the internal environment is monitored, evaluated, changed, re-monitored, re-evaluated Positive and negative feedback loops Feedback loop  STIMULUS Disrupts homeostasis by increasing Negative Feedback CONTROLLED CONDITION Blood pressure Reverses a change in a controlled RECEPTORS Baroreceptors in variable. certain blood vessels Input Action potentials CONTROL CENTER How most variables in the body are Brain controlled Return to homeostasis when the response brings blood pressure back to normal Action potentials Output EFFECTORS Heart Blood vessels RESPONSE A decrease in heart rate and the dilation (widening) of blood vessels cause blood pressure to decrease COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Contractions of the wall of the uterus force the baby's head or body into the cervix Increasing Positive feedback CONTROLLED CONDITION Stretching of cervix RECEPTORS Strengthens or reinforces a change in a Stretch- sensitive nerve cells in the controlled variable cervix Input Action potentials CONTROL CENTER Brain Increased stretching of the cervix Something external must disrupt cycle causes the release of more oxytocin, which results in more stretching of the cervix Brain interprets input and Output releases oxytocin Cervix EFFECTORS Muscles in the wall of the uterus Contract more forcefully RESPONSE Baby’s body stretches the cervix more Interruption of the cycle: The birth of the baby decreases stretching of the cervix, thus breaking the positive feedback cycle Positive feedback: https://education.wiley.com/content/shared/media/anatomy/3D_Interactives/3d_interactive_homeostasis.html Feedforward Events occur in anticipation of a change in a controlled variable. Ex. Mouth watering prior to a tasty meal Predictions Questions to figure out your background Reminder: Participation – if you answer 80% of in-class questions throughout the semester, you get 5% Correct answers not required to get the grade https://forms.gle/VNgkWo1g7zxiRX8T6 Only open when presented in class  https://forms.gle/VNgkWo1g7zxiRX8T6 Questions The pH of your blood is kept around 7.4. When you exercise really hard, your muscles release a bunch of hydrogen ions into the blood. What does this do to the pH of your blood? ◦ Lowers it (more acidic) ◦ Raises it (more basic) ◦ I don’t know Which of the following has the lowest 'set point' for pH? (i.e. where is the most acidic) ◦ Saliva ◦ Gastric Juice (Found in Stomach) ◦ Blood  Questions Which of the following statements regarding ATP is correct? ATP a) Releases energy when a phosphate bond splits b) consists of an adenine molecule, a ribose molecule, and three phosphate groups c) Is the energy currency of the cell d) All of these statements regarding ATP are correct. e) I don’t know Which of the following can the body break down to produce ATP? (select all) a) Carbohydrates b) Protein c) Fat d) Caffeine e) I don’t know Questions Catalysts function by: a) combining with other substances in a reaction to create a new product b) raising the amount of energy needed (making it more difficult) to start the reaction c) breaking themselves apart to provide energy for a reaction d) lowering the amount of energy needed (making it easier) to start the reaction e) I don’t know  Questions Place the following steps of the cellular respiration of glucose in the correct order: i) electron transport chain ii) glycolysis iii) Krebs cycle iv) formation of acetyl CoA a) ii; iv; iii; i b) ii; iii; iv; i c) i; ii; iii; iv d) iv; iii; ii; i e) I don’t know Questions The three main parts of a human cell include all of the following EXCEPT: a) a rigid, protective, nonliving outer cell wall b) a flexible plasma membrane separating the cell’s internal environment from the external environment c) the cytoplasm including the cytosol and organelles d) the nucleus that houses most of the cell’s DNA e) I don’t know For more detailed review See chapters 2, 3, 4 Won’t be tested on content from these chapters specifically, but they may help for understanding of future content The remaing slides give an idea of important content from chapters 2, 3, and 4  Acids and Bases For proper homeostasis, acid base balance must be maintained pH ~7.4 E.g. H+ and muscle function Video explainer Acids and Bases ATP: Our energy ‘currency’ Break apart bond on 3rd phosphate group to release energy Energy captured to do work in the body Energy Macronutrients Nutrients our body can use to provide ATP (energy) ◦ Carbohydrates ◦ Lipids ◦ Proteins Overview of cellular metabolism Anaerobic conditions Which steps require oxygen and which ones do not? Aerobic conditions COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Why is knowledge of nutrients and metabolism important for athletes? e.g. Carbohydrate loading ▪ Maximize glycogen storage ▪ Improve endurance performance e.g. fueling for exercise ▪ Fat, proteins, or carbohydrates?  Roles of protein Building materials Hormones Enzymes Acid-Base Balance Transporters Antibodies Provide glucose and energy Many Other ATP Video: Enzyme Functions and ATP Ligand–protein interaction ▪ Ligand ◦ Any molecule or ion that binds to a particular site on a protein through weak, noncovalent interactions ▪ Binding site ◦ The region of protein where the ligand binds COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. The three main components of the cell Plasma membrane ▪ Forms the cells outer surface Cytoplasm ▪ Consists of the cellular contents between the plasma membrane and nucleus Nucleus ▪ Large organelle that houses most of the cell’s DNA COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. The three main components of the cell Plasma membrane ▪ Forms the cells outer surface Cytoplasm ▪ Consists of the cellular contents between the plasma membrane and nucleus Nucleus ▪ Large organelle that houses most of the cell’s DNA COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Reminders Labs this week – Run by the biology department in the B-wing  STIMULUS Disrupts homeostasis by increasing CONTROLLED CONDITION Blood pressure Last Class RECEPTORS Baroreceptors in certain blood vessels Input Action potentials CONTROL CENTER Brain Homeostasis Return to homeostasis when the ◦ Negative feedback – returns to set point Action potentials response brings blood pressure back to normal Output ◦ Positive feedback – reinforces change EFFECTORS ◦ Feedforward – anticipates change Heart Blood vessels Acids and bases Feedback loop RESPONSE A decrease in heart rate and the dilation ATP (widening) of blood vessels cause blood pressure to decrease ◦ Macronutrients ◦ Aerobic and anaerobic ATP production Energy Last Class Proteins have many functions within the body ◦ Enzymes ◦ Transporters ◦ Structures Components of the cell Protein – ligand interactions Section 1: https://forms.gle/AZwvNP7yWbAr3u4k6 Section 2: https://forms.gle/YBZhhpQFtWodsUaR9 Review questions Blood glucose is regulated within a set point around 5 mm/L. If levels go up or down, the body acts to return to the set point. This is an example of: ◦ Positive feedback ◦ Negative Feedback ◦ Feedforward ◦ Negative feedforward When blood glucose increases, the pancreas releases more insulin. This insulin travels to the liver and tells the liver to take more glucose up from the blood. The liver is the: ◦ Receptor ◦ Control centre ◦ Effector ◦ Response Protein can do all except: ◦ Be used to produce ATP aerobically ◦ Be denatured (damaged) by acidic conditions ◦ Become an enzyme ◦ Be the main structural component of a cell membrane Transport Across Plasma Membranes WEEK 2 DR. TREVOR KING Learning Outcomes: Membrane Transport ▪ Explain why selective permeability of a plasma membrane occurs ▪ Differentiate between the different gradients across the plasma membrane ▪ Summarize the different mechanisms of passive and active transport ▪ Predict how changes in cellular conditions might affect transport processes. ▪ Utilize the principles of membrane transport to analyze practical instances, particularly focusing on epithelial transport as a key example. Transport across the Plasma Membrane When do we need to get things from outside of a cell to inside of a cell – or vice versa? Plasma membrane structure The lipid bilayer Two back-to-back layers made up of three types of lipid molecules Phospholipids Cholesterol Glycolipids  Selective permeability Permeable to Impermeable to Why? Small gaps created with natural movement Charged particles cannot cross Cholesterol in membrane reduces H2O permeability Less permeable to water But why do things move across the membrane? Gradients across the plasma membrane ◦ Concentration gradient ◦ Electrical gradient Solutes want to move DOWN a gradient Area A Area B Area A Area B + -- - + -- + - - + Concentration gradient + + - - - Electrical gradient + - + - + +  Concentration gradient Difference in the concentration of a chemical from one place to another ◦ E.g. Inside to the outside of a plasma membrane What direction is the concentration gradient of CO2?  Electrical gradient A difference in electrical charges between two regions, such as across the plasma membrane What is the direction of the electrical gradient for a positively charged ion (e.g. K+)? Electrochemical gradient Both electrical and chemical forces act on ions The Electrochemical gradient is a combination of both driving forces Classification of Membrane Transport Passive Substance moves across the plasma membrane without any energy input from the cell ◦ Down concentration or electrochemical gradient ◦ Downhill Active Cellular energy, such as ATP, is used to move a substance across the plasma membrane. ◦ Against concentration or electrochemical gradient ◦ uphill Image: kahn academy  Diffusion: A Type Of Passive Transport Random mixing of particles from one location to another because of the particles’ kinetic energy (energy of motion). COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Factors influencing diffusion Steepness of concentration gradient Temperature Mass of the diffusing particle Surface area Diffusion distance Diffusion rate can be calculated Fick’s law of diffusion COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Fick’s Law 𝐶1 − 𝐶2 ∗ 𝐴 ∗ 𝐷 𝐽= 𝑋 𝑤ℎ𝑒𝑟𝑒, 𝐽 = 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝑓𝑙𝑜𝑤, 𝐶1 = 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑛 𝑜𝑛𝑒 𝑠𝑖𝑑𝑒 𝐶2 = 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑛 𝑡ℎ𝑒 𝑜𝑡ℎ𝑒𝑟 𝑠𝑖𝑑𝑒 𝑋 = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝐴 = 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝐷 = 𝑑𝑖𝑓𝑓𝑢𝑠𝑖𝑜𝑛 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 𝐽 = 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝑓𝑙𝑜𝑤, 𝐶1 = 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑛 𝑜𝑛𝑒 𝑠𝑖𝑑𝑒 𝐶2 = 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑛 𝑡ℎ𝑒 𝑜𝑡ℎ𝑒𝑟 𝑠𝑖𝑑𝑒 𝑋 = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝐴 = 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝐷 = 𝑑𝑖𝑓𝑓𝑢𝑠𝑖𝑜𝑛 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 Fick’s Law Analogy 𝐶1 − 𝐶2 ∗ 𝐴 ∗ 𝐷 Analogy: People who want into festival 𝐽= C1-C2 = number of people wanting to get in 𝑋 A = the bigger the festival area, the more areas there are to get in D = Fence hopping ability, conditions for hopping X = height of the wall Types of passive diffusion ▪ Simple diffusion ▪ Facilitated diffusion ▪ Osmosis ❑ Special form of diffusion COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Simple versus facilitated diffusion COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED Simple diffusion Passive process solutes move freely through the lipid bilayer without the help of membrane transport proteins Dependent on concentration gradient. Larger the gradient… COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Facilitated diffusion: Channel mediated Solute moves down its concentration or electrochemical gradient across the lipid bilayer through a membrane channel Typically, ion channels (K+, Cl-, Na+, CA2+) Channels can be “gated” Why would channel mediated diffusion be slower than simple diffusion? COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Facilitated diffusion: Carrier mediated Used to move a solute down its concentration or electrochemical gradient across the plasma membrane ◦ Not a continuous pore ◦ Solute binds to carrier COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Carrier mediated transport ▪ Exhibits certain properties ❑ Specificity ❑ Affinity ❑ Saturation ❑ Competition COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Carrier mediated transport: Specificity and affinity Specificity: Solute shape must match the shape of the carrier protein Affinity is the strength that the solute binds to the protein site Certain proteins have higher affinity to certain molecules COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Carrier mediated transport: Saturation and Competition Saturation: limited number of transporters, therefore Transport maximum (Tm) maximum rate of transport Rate of transport Competition: Similar solutes may compete with one another for the same binding site, reducing rate of transport Reduced rate when competition occurs What would happen if you increased the number of transporters? What would happen if you reduced the Concentration gradient of solute affinity of the solute binding? COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Osmosis The net movement of solvent through a selectively permeable membrane ▪ In living systems the solvent is water Occurs via both: ▪ Aquaporins (water channels) ▪ Simple diffusion Area of low solute conc. to Solutes suck! COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. high solute conc.  Tonicity ▪ Affect that osmolarity has on cell shape ▪ Osmolarity: amount of dissolved particles pulling the water towards it What is the tonicity of your blood plasma? What would happen if you put a cell in salt water? Distilled water? COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Active Transport Remember: The movement of substances across a membrane against their concentration or electrochemical gradient COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Primary active transport Uses ATP to move solute against electrochemical gradient ▪ E.g. sodium-potassium pump 40% of energy use in a typical cell! COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Sodium-potassium pump The pump maintains an electrochemical gradient in the cell COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Secondary active transport ▪ Uses energy stored in the electrochemical gradient of an ion ▪ Drives other solute against electrochemical gradients. ◦ E.g. sodium-glucose transporters IMAGE: BIONINJA Secondary active transport COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Transepithelial transport ▪ Movement of solutes across epithelial cells. ▪ Tight junctions connect epithelial cells ▪ Absorption ◦ When a solute moves from the lumen of an organ into the bloodstream ▪ Secretion ◦ When a solute moves from the bloodstream into the lumen of an organ COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Application to practice: Multisource Carbohydrate Beverages Glucose: Epithelial cell Fast absorption (SGLT1) GLUCOSE GLUCOSE GLUT2 SGLT1 Fructose: Slow absorption (GLUT5) INTESTINAL LUMEN Combined: GLUT5 FRUCTOSE GLUT2 FRUCTOSE More total CHO absorption BLOODSTREAM Describe why this works using saturation or competition Summary: Membrane Transport Membranes are selectively permeable Electrochemical gradients determine motion of solutes Diffusion – down electrochemical gradient ◦ Simple ◦ Facilitated (proteins help) ◦ Osmosis Active transport (uses ATP) ◦ Primary ◦ Secondary Reminders Office hours ◦ Tuesdays 1 to 2 (let me know you’re coming) ◦ Or by appointment Last Class: Membrane Transport Membranes are selectively permeable Electrochemical gradients determine motion of solutes Diffusion – down electrochemical gradient ◦ Simple ◦ Facilitated (proteins help) ◦ Osmosis Active transport (uses ATP) ◦ Primary ◦ Secondary Last Class: Secondary active transport COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Transepithelial transport ▪ Movement of solutes across epithelial cells. ▪ Tight junctions connect epithelial cells ▪ Absorption ◦ When a solute moves from the lumen of an organ into the bloodstream ▪ Secretion ◦ When a solute moves from the bloodstream into the lumen of an organ COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Application to practice: Multisource Carbohydrate Beverages Glucose: Epithelial cell Fast absorption (SGLT1) GLUCOSE GLUCOSE GLUT2 SGLT1 Fructose: Slow absorption (GLUT5) INTESTINAL LUMEN Combined: GLUT5 FRUCTOSE GLUT2 FRUCTOSE More total CHO absorption Why? Describe why this works using saturation, competition, specificity, or affinity BLOODSTREAM Section 1 : https://forms.gle/pG5n47yH6qqGsEqu5 Section 2: https://forms.gle/BStWpfGCKzgQZUru9 Review Questions Fructose is transported into the epithelial cells using Glut5, which is a carrier protein. As a marathon runner, you want to maximize carbohydrate absorption to use as fuel. However, Trevor has advised you that one litre of Gatorade an hour is all you need. Why wouldn’t you want to drink 2 or 3 litres of Gatorade per hour (other than the fact that you would probably get some terrible gastrointestinal issues) ◦ Via competition, too much fructose would reduce your absorption of glucose ◦ Via saturation, 1 L of Gatorade already saturates your Glut5 proteins ◦ Too much Gatorade would reduce affinity of glut5 for fructose binding ◦ Glut 5 doesn’t have enough specificity to bind to fructose. Review Questions The sodium-potassium pump works via: ◦ Simple diffusion ◦ Facilitated diffusion ◦ Primary active transport ◦ Secondary active transport According to Fick’s law, an increase in diffusion distance has what impact on particle flow? ◦ Increase ◦ Decrease ◦ No change Cell Signaling CHAPTER 6 TREVOR KING Learning Objectives Recall the different types of cellular communication Predict how cellular communication would be impacted by changes in specificity, affinity, competition, and saturation Describe how extracellular chemical messengers can be used to transmit a signal Classify real examples of cellular communication Explain why signal transduction is used by cells Using your knowledge of extracellular chemical messengers, receptors, and signal transduction, predict how a disturbance in the system would impact the cellular response Why is cell signaling important? Cells must communicate with each other to coordinate body activities and maintain homeostasis E.g. Step on tack Oxygen levels decrease EPO  Types of cellular communication 1. Gap junctions 2. Cell-to-cell binding 3. Communication through extracellular chemical messengers COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Gap Junctions Membrane proteins called connexins form tunnels called connexons that connect neighboring cells. Allows for rapid diffusion and communication Connexon tunnel E.g., neuron, muscle cells Connexin What would cause the diffusion to occur? COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Cell-to-Cell Binding Surface molecules on two different cells bind to one another E.g., Leukocytes and immunity COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Extracellular Messengers Most common ▪ Provide a wide variety of responses Steps ▪ Binding of secreted chemical messenger onto downstream cell receptor ▪ Signal transduction ▪ Cellular response COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Extracellular Messengers 1. Receptor binding: extracellular messenger binds to a protein called a receptor. Target cell displays receptor on plasma membrane or in cell 2. Signal transduction: receptor binding is converted (transduced) into a target cell signal. Series of molecules causing a “chain reaction” 3. Cellular response: the response carried out by the target cells after the signal transduction pathway is complete COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Types of Extracellular Chemical Messengers 1. Hormones 2. Neurotransmitters 3. Local mediators COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Extracellular Chemical Messengers: Hormones Carried by the blood to distant target cells ▪ E.g. glucagon – pancreas to liver ❑ Release glucose COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Extracellular Chemical Messengers: Neurotransmitters Released from a neuron into a synapse to reach a nearby target cell ❑ Diffusion e.g. dopamine COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Local Mediators Also known as local regulators or local agents Signaling to nearby cells via diffusion Paracrine = neighboring cells Autocrine = same cell Checkpoint: Apply your knowledge Fill in the blanks: Insulin is a _______ that is released from the pancreas into the blood. It travels through the blood to the muscle cells, telling them the extract glucose from the blood. When insulin reaches the muscle, it attaches to a protein in the muscle cell wall called a ______. This starts a cascade of signals throughout the muscle cell (called signal _____) that result in the movement of glut 4 to the cell membrane (called the cellular ______). Based on last class, we know that glut 4 is a protein that uses ________ diffusion to allow glucose to enter the cell. Hormones in the Blood Most water-soluble extracellular messengers are in “free” form Most lipid soluble extracellular messengers are bound to a transport protein ◦ Increase solubility in blood ◦ Less likely to be filtered out by kidney ◦ Provides hormone reserve in blood  Remember: Receptors Extracellular chemicals exhibit their effects by binding to specific downstream cell receptors Messenger-receptor binding exhibits several properties ▪ Specificity ▪ Affinity ▪ Saturation Where have we seen ▪ Competition these properties? COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Specificity & Affinity Extracellular chemical messengers need specific receptor shape to bind to target cell Affinity: the strength at which the ligand binds to the receptor ▪ Stronger affinity=more likely to bind The extracellular messenger in this context is the ligand (i.e., molecule binding to a specific site of a protein) COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Saturation Limited number of receptors Maximum rate of binding Why doesn’t this figure show a linear increase with these two variables? COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Adenosine ZZZZZZZZ Competition Two molecules are competing Adenosine for the same receptor if both receptor are able to bind to the site E.g. In the brain, adenosine (agonist) and caffeine Adenosine caffeine (antagonist) compete for the same receptors What could be done to Adenosine increase the likelihood of one receptor molecule to bind? inhibited COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Receptor Location 1) Inside the target cell 2) on the target cell plasma membrane ◦ Lipid soluble ◦ Water Soluble Cannot pass through membrane Can pass through membrane Receptor Down Regulation Receptor Down-regulation When extracellular messengers are present in excess, the number of target cell receptors may decrease vesicle Two methods -Endocytosis - Reduces saturation level E.g. drug tolerance -Chemical modifications of the receptor - Reduces function or affinity Is this an example of negative or positive feedback? Receptor Up-Regulation When an extracellular messenger is deficient, the number of target cell receptors may increase Two methods -Exocytosis -Synthesis of receptors Checkpoint Draw a line on the graph to represent each situation: a) Ligand increases affinity b) Receptor down-regulation c) Receptor up-regulation d) Reduced competition Number Signal transduction What is signal transduction from a high level? Sequence of events 1) Begins with the binding of an extracellular messenger to a receptor 2) message is sent through relay proteins 3)Ends with the cellular response Why even have relay proteins?  Second Messengers and Protein Kinases Second messenger: generated Second messenger from binding to receptor (small Receptor Inactive relay molecule or ion)  protein Protein kinase: enzyme that Extracellular phosphorylates (adds phosphate chemical messenger ☺ Active relay (first messenger) group) to target protein protein (protein  Effector kinase) protein ◦ Can activate or inhibit ◦ Targets effector or other relay P protein ☺ Effector protein (phosphorylated) Kinases often named after what they phosphorylate e.g. tyrosine kinase (tyrosine), protein kinase G (cGMP) Cellular response To be continued… The Central Nervous System BIOL 1216 WK4 – L2 TREVOR KING Last class: Graded and Action Potentials Graded potential ◦ Receive information ◦ Dendrites and cell body – dissipates across cell Action potential ◦ Graded potential (cell body/dendrites) initiates action potential in axon if above threshold ◦ All or nothing ◦ Moves down axon Repolarization phase Myelination ◦ Faster and more efficient action potentials Nodes required to maintain signal Last class: Neuron communication Synapse ◦ Point of communication Neurotransmitter release ◦ EPSP and IPSP ◦ Spatial summation ◦ Multiple locations graded potentials ◦ Temporal Summation ◦ Repeated graded potentials at the same location Section 1: https://forms.gle/wbYWXkeThfakzyZK7 Section 2: https://forms.gle/bbHi2f8cU7UFWadd7 Question: Graded potentials How would the following situations would depolarize the soma of a neuron? ◦ Binding of a neurotransmitter to the post-synaptic cell that opens ligand-gated K+ channels ◦ An inhibitory post-synaptic potential (IPSP) ◦ Temporal summation of excitatory post-synaptic potentials (EPSPs) ◦ Spatial summation of excitatory post-synaptic potentials (EPSPs) Question Place the following steps on the graph: 2 A. Closing of sodium inactivation gate 3 B. Opening of voltage gated potassium gates C. Opening of voltage gated sodium gates D. Closing of potassium gates 1 4  Learning outcomes of this Lecture Set ▪ Identify the functions of neurotransmitters ▪ Distinguish the different neural circuits ▪ Identify the general structures and functions of the spinal cord ▪ Describe the general structures and functions of the brain ▪ Match the different areas of the cerebrum to their functions ▪ Recognize the various ways that the brain is protected ▪ Identify the roles of the sensory, motor, and association areas of the cerebral cortex COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Termination of the signal Neurotransmitters must be degraded or removed in order to terminate the signal transduction Diffusion: neurotransmitters can diffuse away from synaptic cleft Enzymatic degradation: enzymes can break down neurotransmitters (e.g., acetylcholinesterase) Uptake by cells: taken back up by the neuron that released them or passed to neighbouring neuroglia (neurotransmitter transporters) © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Regulation of neurotransmitter release Presynaptic modulation can regulate neurotransmitter release, leading to either increased or decreased release LESS neurotransmitter release MORE neurotransmitter release Neural circuits Remember: Organization of the Nervous System Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Spinal Cord: Protection Spinal cord is protected by Spinal cord vertebrae and meninges Meninges: Pia mater Arachnoid mater Meninges: Connective tissue Dura mater layers that surround the spinal cord ▪ 3 layers of meninges Vertebrae ❑ Pia mater ❑ Arachnoid mater ❑ Dura mater COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Spinal cord and spinal nerves Spinal nerves are connected to the spinal cord A total of 31 pairs Jobs ◦ Bring sensory information from receptors Spinal to the spinal cord nerves ◦ Bring motor information from spinal cord to muscles and glands Spinal cord and spinal nerves Ganglion: bundle Structure and formation of the spinal nerve of cell bodies Dorsal roots Roots - 2 bundles ◦ Dorsal root: sensory ◦ Ventral root: motor motor To remember: command Dorsal fin Sensory info Ventral roots Spinal cord and spinal nerves: Gray matter Grey matter: ◦ dendrites and cell bodies of neurons Dorsal gray horns ◦ unmyelinated axons Dorsal gray horns ◦ Cell bodies of interneurons ◦ Process sensory information Ventral gray horns ◦ Cell bodies of somatic motor neurons ◦ Send action potentials to skeletal muscle Ventral gray horns Spinal cord and spinal nerves: White matter White matter Lateral white column Dorsal white column ◦ Myelinated axons of neurons Subdivided into three sections ◦ Dorsal white columns ◦ Ventral white columns ◦ Lateral white columns Ascending Each contains bundles of axons Descending called tracts ◦ Ascending tracts – send signals toward the brain ◦ Descending tracts – send signals away from brain Ventral white column  Spinal cord: Reflexes Reflex arc components: 1. Sensory receptor ▪ Detects the stimulus 2. Sensory neuron ▪ Sends information to central nervous system 4. Motor neuron 3. Integrating center (interneurons) 3. Integrating centre (Interneurons) ▪ Brain or spinal cord 1. Receptor 5. Effector 4. Motor neuron (muscle) ▪ Sends out signal to effector organ 2. Sensory neuron 5. Effector ▪ Organ or gland that changes function in response to motor neuron COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. https://www.urmc.rochester.edu/MediaLibraries/URMCMedia/life-sciences-learning- center/documents/2013-14Neuroscience/HandOnHotStove-092513-teacher.pdf Spinal Cord: Reflexes (another example) COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Spinal cord: putting it together Trace the action potentials along their paths in the following situation: You’re in a dark room of a haunted house. You’re sitting still, and all of a sudden, something hairy rubs against your arm! All at once, you jump up, your heart races, and you pee yourself. Summary The Brain By the end of this part you will be able to… Explain the various ways that the brain is protected Discuss the functions of the different parts of the brain Identify the roles of the sensory, motor, and association areas of the cerebral cortex COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Brain: Protection Cranium Meninges Blood brain barrier Cerebral spinal fluid COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.  Brain: Protection Cranium ◦ Bony structure Cranium Meninges CRANIAL MENINGES: ◦ Dura mater Dura mater ◦ Arachnoid mater Arachnoid mater Pia mater ◦ Pia mater Brain  Endothelial cell of Tight brain capillary junction Brain: Protection Astrocyte process Blood-Brain barrier ◦ Specialized capillaries Structural component Transport ◦ Tight junctions proteins ◦ between endothelial cells ◦ Astrocytes ◦ Secrete chemicals to maintain “tightness” Functional component ◦ Specialized membrane transporters Brain tissue to allow only some water soluble substances through ◦ Very selective (b) Blood-brain barrier https://www.youtube.com/watch?v=sKG81gJuTLM&t=58s&ab_channel=STAT  ARACHNOID VILLUS SUBARACHNOID SPACE Brain: Protection Cerebrospinal Fluid ◦ Clear and colorless ◦ Continuously circulates through CHOROID PLEXUS various openings in the brain (Ventricles) and subarachnoid space ◦ Produced by choroid plexus Functions ◦ Mechanical protection Spinal cord ◦ Shock absorbing - damping ◦ Chemical protection SUBARACHNOID SPACE ◦ Optimal chemical environment ◦ Circulation ◦ Exchange of nutrients and waste Path of: CSF Venous blood Pathways of circulating cerebrospinal fluid Brain: Functions COPYRIGHT © 2019 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Areas of the Brain The brain is divided into the: ◦ cerebrum ◦ cerebellum ◦ diencephalon ◦ brainstem Cerebrum Diencephalon Cerebellum Brain Stem Midbrain Pons Medulla oblongata The Cerebrum I II The cerebrum III ◦ The cerebral cortex (outer layer) houses the conscious mind Layers of the cerebral cortex (gray matter) IV Dendrites ◦ left and right cortices (hemispheres) V ◦ deep areas under the cortex. VI Axon The cortexes Cerebral ◦ Divided into lobes white matter ◦ Brodmann areas - functional Cortex contains folds Cerebral cortex Cerebral white matter (d) Frontal section of cerebrum The Cerebrum - Lobes frontal Central sulcus parietal occipital temporal The Cerebrum – Brodmann Areas The most important Brodmann areas for movement: ◦ motor cortex and premotor cortex ◦ somatosensory cortex ◦ auditory cortex ◦ visual cortex. Frontal lobe ◦ Conscious thought and decision making Motor and Somatosensory cortex The motor and somatosensory cortexes can be mapped to correspond to body areas. ◦ Why are some areas larger than others? https://www.youtube.com/watch?v=APuiZCxDnTA Question Where would the motor command to grab an object come from? Which hand did this person grab with? C B D A