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Big Idea #4 AP Biology Definition Controlling the internal environment Maintenance of stable internal environment Negative Feedback Response produced opposes stimulus Homeostasis restored Positive Feedback Response produced reinforces stimulus Homeostasis not restored - disruption continues Rare Example – Childbirth Mechanism Disruption detected by receptors Homeostasis Control Center evaluates information & directs response Effector produces response that restores homeostasis Controlling Body Temperature Homeostasis Evaporative cooling Heat lost from skin Temperature receptors in skin & hypothalamus detect increase temperature Control Center Hypothalamus Sweat glands increase secretion Blood vessels in skin dilate Controlling Body Temperature Homeostasis Heat generated Heat conserved Temperature receptors in skin & hypothalamus detect decrease temperature Control Center Hypothalamus Muscles contract Shiver Blood vessels in skin constrict Maintaining glucose levels Controlling Blood Glucose Levels Blood glucose levels rise Homeostasis Normal Glucose Levels Beta cells in pancreas release insulin Cells take in glucose Blood glucose levels drop Controlling Blood Glucose Levels Blood glucose levels fall Homeostasis Normal Glucose Levels Alpha cells in pancreas release glucagon Breakdown of glycogen in liver & skeletal muscles Blood glucose levels increase You try Calcium, Osmolarity Controlling Blood Calcium Levels Blood calcium levels rise Homeostasis Normal Calcium Levels Thyroid releases calcitonin Ca2+ deposited in bone Kidneys reduce uptake of Ca2+ Blood Ca2+ levels drop Controlling Blood Calcium Levels Blood calcium levels fall Homeostasis Normal Calcium Levels Parathyroid releases parathyroid hormone (PTH) Ca2+ released from bone Kidneys increase uptake of Ca2+ Blood Ca2+ levels rise Positive Feedback Two Main Controls: Electrical and Chemical Nervous System Endocrine System Neuron Structure Nerve Impulse Transmission Resting potential More negative inside cell than outside Why? Large negatively charged proteins & nucleic acids Na+/K+ pumps maintain high [Na+] outside cell and high [K+] inside cell Nerve Impulse Transmission Resting potential Membrane potential = -70 mV Nerve Impulse Transmission Depolarization Stimulus causes Na+ gates to open Na+ rushes into cell Nerve Impulse Transmission Repolarization Na+ gates close & K+ gates open K+ rushes out of cell High [Na+] inside cell High [K+] outside cell Nerve Impulse Transmission Hyperpolarization K+ gates slow to close More K+ moved out than necessary Nerve Impulse Transmission Refractory period Na+/K+ pumps move Na+ out of cell K+ into cell Restores resting potential distribution of Na+ and K+ Transmission Across a Synapse Synapse Gap between neurons Transmission Across a Synapse Stimulus reaches synaptic end bulb Transmission Across a Synapse Ca2+ gates open Ca2+ enters end bulb Transmission Across a Synapse Vesicles with neurotransmitter migrate to presynaptic membrane Transmission Across a Synapse Vesicle fuses with presynaptic membrane Transmission Across a Synapse Neurotransmitter released into synaptic cleft Transmission Across a Synapse Neurotransmitter diffuses across cleft Transmission Across a Synapse Neurotransmitter binds to receptor protein Transmission Across a Synapse Postsynpatic neuron depolarizes CEPHALIZATION BRAIN PARTS! Sensory - detects environmental changes and sends info to brain Somatic – ttpp (touch, taste, pressure, pain) Special – rods, cones, sensory “hairs” in nose, ear and tongue BRAIN and SPINAL CORD Brain – main processor (control center) 3 main parts: cerebrum, cerebellum, brain stem CEREBRUM CEREBELLUM BRAIN STEM: Pons and Medulla Oblongata BRAIN STEM: Mid-Brain SPINAL CORD: Control Somatic – conscious control, skeletal muscles Autonomic – automatic control, smooth and cardiac muscles and glands Parasympathetic Sympathetic PNS - Somatic Motor cortex of cerebrum Down spinal cord Motor neurons to muscle Neuro-muscular junction Muscle Contraction Sliding filament model Muscle Contraction Sliding filament model Depolarization of muscle causes sarcoplasmic reticulum to release Ca2+ Muscle Contraction Sliding filament model Ca2+ exposes binding sites on actin Myosin heads bind to actin Cross bridges form Muscle Contraction Sliding filament model Myosin heads lose ADP + P Myosin heads change shape Actin pulled toward center of sarcomere Muscle contracts Muscle Contraction Sliding filament model ATP binds to myosin heads Cross bridges break Muscle relaxes Muscle Contraction Sliding filament model Works with nervous system to maintain physiological balance Hypothalamus Pituitary gland Endocrine glands- ductless Glands: A B C D E F G H Thyroid Pituitary Pineal Thymus Adrenal Pancreas Ovaries Testes Endocrine hormones Chemicals secreted into blood by glands Received by specific target cells and cause a specific reaction Steroids, peptides or amino acids Main Hormones to Know ACTH Androgens ADH Calcitonin Epinephrine Glucagon Glucocorticoids Insulin Melatonin Oxytocin Thyrosine Steroid Hormone Steroid hormone enters cell Steroid Hormone Steroid hormone enters cell Binds to receptor Steroid Hormone Steroid hormone enters cell Binds to receptor Hormonereceptor complex enters nucleus Causes transcription DNA transcribed RNA translated Protein Hormone Protein hormone too big to enter cell Protein Hormone Protein hormone too big to enter cell Binds to receptor Protein Hormone Protein hormone too big to enter cell Binds to receptor Activates enzyme Enzyme used to make cyclic AMP Protein Hormone Protein hormone too big to enter cell Binds to receptor Activates enzyme Enzyme used to make cyclic AMP Cyclic AMP targets cell responses Pituitary Gland – “master” gland Stores and releases hormones produced by hypothalamus Anterior region – attached to and extending from hypothalamus Posterior region – not attached directly to hypothalamus but very close proximity Anterior pituitary Pituitary (ADH) Tropic Hormones? Hormones that target other endocrine glands Negative Feedback Calcium levels Negative Feedback Glucose levels Antagonistic hormones Hormone Meet and Greet Party – HELLO, MY NAME IS … I am secreted by… I target…and cause it/them to… I am regulated by… Too much of me (hypersecretion) and …. Too little of me (hyposecretion) and… Nervous and Hormonal Control Sympathetic nervous system – triggers fight or flight by stimulating the release of certain hormones Adrenal Gland Adrenal medulla – nerves directly stimulate release of epinephrine, norepinephrine Adrenal cortex – releases corticosteroids due to ACTH released from ant. pituitary Fight or flight response Due to hormones released Epinephrine (adrenaline)– increases breathing, heart rate, dialates some vessels and constricts others Corticosteroids – open breathing passageways COMPARTMENTALIZATION Specialization and Regulation: Systems Gas exchange Circulation Digestion Excretion
