Homeostasis Endocrine System Nervous System 2004-2005
Regulation Why are hormones needed? chemical messages from one body part to another communication needed to coordinate whole body homeostasis & regulation metabolism growth development maturation reproduction 2004-2005 growth hormones
Regulation & Communication Animals rely on 2 systems for regulation endocrine system (video) ductless gland which secrete chemical signals directly into blood chemical travels to target tissue slow, long-lasting response nervous system system of neurons, central nerve system transmits electrical signal to target tissue fast, short-lasting response 2004-2005
Regulation by chemical messengers Neurotransmitters released by neurons Hormones release by endocrine glands Endocrine gland Axon Neurotransmitter Hormone carried by blood Receptor proteins Target cell 2004-2005
Classes of Hormones Protein-based hormones polypeptides small proteins: insulin, ADH glycoproteins large proteins carbohydrate: FSH, LH amines modified amino acids: epinephrine, melatonin Lipid-based hormones steroids modified cholesterol: sex hormones, aldosterone
How do hormones act on target cells Lipid-based hormones lipid-soluble diffuse across membrane & enter cells bind to receptor proteins in cytoplasm & then this hormone-receptor complex moves into nucleus bind to receptor proteins in nucleus Receptor protein hormone bind to DNA and stimulate transcription Transcription: making an RNA copy of DNA
Action of steroid (lipid) hormones Cytoplasm S 2 S Steroid hormone 1 Plasma membrane 1 Blood plasma S Protein carrier Steroid hormone (S) passes through plasma membrane. S 4 2 Inside target cell, the steroid hormone binds to a specific receptor protein in the cytoplasm or nucleus. DNA Nucleus 3 mrna 3 5 Protein 4 5 Hormone-receptor complex enters nucleus & binds to DNA, causing gene transcription Protein synthesis is induced. Protein is produced. 2004-2005
How do hormones act on target cells Protein-based hormones hydrophilic & not lipid soluble can t diffuse across membrane trigger secondary (2 ) messenger pathway transmit signal across membrane usually activates a series of 2 messengers activate cellular response enzyme action, uptake or secretion of molecules, etc. Signal molecule G protein Cell surface receptor enzyme ATP Nucleus camp Target protein Cytoplasm 2004-2005
Action of protein hormones 1 Protein hormone Receptor protein G protein 2 activates enzyme camp 3 Cytoplasm GTP ATP activates enzyme activates enzyme 4 protein messenger cascade Produces an action
Benefits of a 2 messenger system Signal molecule 1 Receptor protein Activated adenylyl cyclase 2 Amplification Not yet activated 4 Amplification GTP 3 G protein 5 camp Protein kinase 6 Amplification Amplification! 7 Amplification Enzyme Enzymatic product 2004-2005
Endocrine system Ductless glands release hormones into blood Duct glands = exocrine (tears, salivary) 2004-2005
Glands Pineal melatonin Pituitary many hormones: master gland Thyroid thyroxine Adrenal adrenaline Pancreas insulin, glucagon Ovary estrogen Testes testosterone
Major vertebrate hormones (1) 2004-2005
Major vertebrate hormones (2)
Endocrine & Nervous system links Hypothalamus = master control center nervous system receives information from nerves around body about internal conditions regulates release of hormones from pituitary Pituitary gland = master gland endocrine system secretes broad range of hormones regulating other glands 2004-2005
Hypothalamus Thyroid-stimulating Hormone (TSH) Thyroid gland Posterior pituitary Anterior pituitary Antidiuretic hormone (ADH) Kidney tubules Adrenal cortex Gonadotropic hormones: Folliclestimulating hormone (FSH) & luteinizing hormone (LH) Muscles of uterus Melanocyte in amphibian Bone and muscle Testis Ovary Mammary glands in mammals 2004-2005
Maintaining homeostasis (video) hormone 1 Feedback gland lowers body condition high specific body condition low raises body condition gland hormone 2
Negative Feedback Response to changed body condition if body is high or low from normal level signal tells body to make changes that will bring body back to normal level once body is back to normal level, signal is turned off gland hormone 1 lowers body condition high specific body condition
Endocrine System Control Regulation of Blood Sugar insulin Feedback pancreas body cells take up sugar from blood liver stores sugar reduces appetite high blood sugar level (90mg/100ml) low liver triggers hunger liver releases sugar pancreas liver glucagon
Female reproductive cycle Feedback ovary estrogen egg matures & is released (ovulation) builds up uterus lining corpus luteum progesterone FSH & LH pituitary gland maintains uterus lining pregnancy fertilized egg (zygote) yes HCG corpus luteum GnRH no progesterone hypothalamus corpus luteum breaks down progesterone drops menstruation maintains uterus lining
Any Questions??
Nervous System
signal direction Nervous system cells Neuron a nerve cell dendrites axon Structure fits function many entry points for signal one path out transmits signal signal direction cell body dendrite cell body axon synapse
Neuron
Cells: surrounded by charged ions Cells live in a sea of charged ions anions (negative ions ) more concentrated within the cell Cl-, charged amino acids cations (positive ions) more concentrated in the extracellular fluid Na channel leaks K K Na Na Na Na Na Na K Na Na Na Na Na K aa - Cl - Cl - Cl - Cl - K aa - aa - aa - K K aa - Cl - aa - Cl -
Resting Potential
Cells have voltage! Opposite charges on opposite sides of cell membrane membrane is polarized negative inside; positive outside charge gradient stored energy (like a battery)
How does a nerve impulse travel? Stimulus: nerve is stimulated open Na channels in cell membrane The 1st domino is down membrane becomes very permeable to Na Na ions diffuse into cell charges reverse at that point on neuron positive inside; negative outside cell becomes depolarized Na
How does a nerve impulse travel? Wave: nerve impulse travels down neuron change in charge opens other Na gates in next section of cell voltage-gated channels Na ions continue to move into cell wave moves down neuron = action potential The rest of the dominoes fall Na wave
How does a nerve impulse travel? Re-set: 2nd wave travels down neuron K channels open up slowly K ions diffuse out of cell charges reverse back at that point negative inside; positive outside Set dominoes back up quickly K Na wave
How does a nerve impulse travel? Ready for next time! Combined waves travel down neuron wave of opening ion channels moves down neuron signal moves in one direction flow of K out of cell stops activation of Na channels in wrong direction Na wave K
How does a nerve impulse travel? Action potential propagates wave = nerve impulse, or action potential brain finger tips in milliseconds! In the blink of an eye! K Na wave
Voltage-gated channels Ion channels open & close in response to changes in charge across membrane Na channels open quickly in response to depolarization & close slowly K channels open slowly in response to depolarization & close slowly Na wave K
How does the nerve re-set itself? After firing a neuron has to re-set itself Na needs to move back out K needs to move back in both are moving against concentration gradients need a pump!! A lot of work to do here! K Na K Na K Na Na K Na Na Na Na Na Na Na Na Na Na Na Na K K K K K K Na Na K wave K
How does the nerve re-set itself? Na / K pump active transport protein in membrane requires ATP 3 Na pumped out 2 K pumped in re-sets charge across membrane That s a lot of ATP! Feed me some sugar quick!
Action Potential
Measuring cell voltage unstimulated neuron = resting potential of -70mV
Action potential graph 1. Resting potential 2. Stimulus reaches threshold potential 3. Na channels open; K channels closed 4. Na channels close; K channels open 5. Undershoot: K channels close slowly
Synaptic terminal Chemicals stored in vesicles release neurotransmitters diffusion of chemical across synapse conducts the signal chemical signal across synapse stimulus for receptors on dendrites of next neuron We switched from an electrical signal to a chemical signal synaptic terminal neurotransmitter chemicals
Transmission Across a Synapse
Chemical synapse: follow the path action depolarizes membrane triggers influx of Ca vesicles fuse with membrane release neurotransmitter to cleft neurotransmitter bind with receptor neurotransmitter degraded / reabsorbed ion-gated channels
Nerve impulse in next neuron Post-synaptic neuron triggers nerve impulse in next nerve cell chemical signal opens ion-gated channels Na diffuses into cell K diffuses out of cell Here we go again! Na
Neurotransmitters Acetylcholine transmit signal to skeletal muscle Epinephrine (adrenaline) & norepinephrine fight-or-flight response Dopamine widespread in brain affects sleep, mood, attention & learning lack of dopamine in brain associated with Parkinson s disease excessive dopamine linked to schizophrenia Serotonin widespread in brain affects sleep, mood, attention & learning
Acetylcholinesterase Enzyme which breaks down neurotransmitter acetylcholine inhibitors = neurotoxins snake venom, sarin, insecticides neurotoxin in green active site in red acetylcholinesterase snake toxin blocking acetylcholinesterase active site