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Body Systems – Part II Chemical Signals – CH 45 Nervous Signals– CH 48 Nervous System – CH 49 1 Chapter 45 Hormones and the Endocrine System 2 Hormone chemical excreted into body fluids - used for communication within an organism - helps maintain homeostasis - modified amino acids and steroids - carried by the circulatory system to target cells Target Cells equipped to respond to particular hormone; typically have membrane proteins that allow SPECIFIC hormones to bind **So this means that hormones in the blood can cause changes in SOME cells, and other cells will ignore them** 3 Nervous vs. Endocrine System Nervous System high speed signals; Ex. Jerking your hand away from a flame Endocrine System slower communication; Ex. Maturation of a butterfly; two parts: 4 Local Regulators Affects activity between neighbor cells; only uses LOCAL targets; there are 3 types: Growth Factors peptides/proteins stimulate cell growth and development in target cells; includes nerve growth factors Nitric Oxide (NO) a gas that has multiple functions including acting as a neurotransmitter (when secreted by neurons) and relaxing smooth muscle (when secreted by endothelial cells); it triggers a change in a target cell then breaks down quickly; it is also highly reactive and can be toxic Prostaglandins modified fatty acids first isolated in semen produced by prostrate; effect the female reproductive system (can cause smooth muscle contractions to help sperm reach egg; also induces uterine contraction in childbirth); aspirin and ibuprofen can inhibit the effects of PGs 5 Local Regulators divided into 2 groups: Paracrine act on cells NEAR the secreting cell Autocrine secreted regulators that act on the secreting cell itself! 6 Synaptic Signaling vs. Neuroendocrine Signaling Signaling neurons form specialized junctions called synapses with target cells, such as other neurons and muscle cells; at synapses, neurons secrete molecules called neurotransmitters, which diffuse a very short distance to bind to receptors on the target cell Synaptic Neuroendocrine Signaling specialized neurons called neurosecretory cells secrete chemical signals that diffuse from nerve cell endings into the bloodstream; these signals are a class of hormones called neurohormones (ex. ADH) - Endocrine – Ductless (secretes hormones into body fluids) - Exocrine – Uses ducts to send to specific locations (ex. sweat glands) 7 Signal Transduction Pathway 3 main Processes: - Reception signal binds to a receptor protein - Signal Transduction causes a change in the target cell - Response causes a change in the receptor cell’s behavior Different types of cells respond differently, so the SAME SIGNAL can bring about a DIFFERENT RESPONSE in various target cells. Only small amounts of regulators (ex. Hormones) are necessary because the pathway triggers enzyme cascades that can greatly amplify the signal. 8 The endocrine system and the nervous system are very closely related Several chemicals serve as both hormones of the endocrine system and signals in the nervous systems Ex. Epinephrine (This shows how the two systems are CHEMICALLY related) ○ Nervous system = neurotransmitter ○ Endocrine system = “fight or flight” hormone Each system affects the output of the other Ex. Breast feeding – uses interdependent nervous and hormonal signals: ○ Suckling = simulates sensory cells and nervous signals in the hypothalamus then trigger the release of oxytocin from the pituitary gland; this oxytocin cause the mammary cells to secrete milk 9 Tropic Hormones Tropic Hormone: have other endocrine glands as their targets 10 Feedback Feedback is COMMON TO BOTH THE ENDOCRINE AND THE NERVOUS SYSTEM!! Positive Feedback: causes a change in the same direction; ex. increasing milk release, labor during childbirth (oxytocin!) Negative Feedback: causes a change in the opposite direction; is responsible for the endocrine system’s ability to regulate homeostasis mechanisms; ex. sweating = cools the body 11 Pancreas Secretes bicarbonate ions to balance the pH from the acid chyme in the stomach Alpha cells secrete glucagon signals the liver to release glucose back into blood stream (increases blood sugar levels); used when someone has not eaten in a while and blood sugar levels are low Beta cells secrete insulin signals body cells to take up glucose from the blood (decreases blood sugar levels); used when someone just ate and blood sugar levels are high Exocrine (secrete into ducts) bicarbonate ions and digestive enzymes Endocrine (ductless) insulin/glucagon antagonists 12 **Insulin and Glucagon are not steroids…they are PROTEIN hormones made of AA’s** Glucagon and Insulin are antagonistic hormones and work together to regulate the blood sugar levels in the body (recall our other antagonistic hormones are calcitonin and PTH for calcium) 13 Diabetes Most common endocrine disorder = Diabetes caused by a deficiency in insulin or loss of response to insulin in target cells Type I diabetes autoimmune disorder; immune system attacks pancreas; occurs in childhood and causes kid to not be able to make insulin; treated with insulin injections or a pump Type II diabetes characterized by deficiency of insulin or reduced responsiveness in target cells; 90% of diabetics are type II; can usually be managed by diet and exercise; caused by genetics and obesity 14 Hypothalamus Integrates the endocrine and nervous systems A good example of how they are structurally related is the NEUROSECRETORY CELLS located in the hypothalamus It is part of the lower brain ** It is important in homeostatic regulation (ex. body’s thermostat, regulates hunger/thirst, role in sexual/mating behaviors) ** It regulates the Pituitary Gland ** The neurosecretory cells of the hypothalamus secrete two hormones: oxytocin and ADH 15 Pituitary Located at base of the brain Referred to as “Master Gland” because it regulates so many other endocrine functions It obeys orders from the hypothalamus Has 2 discrete parts: ○ Anterior Pituitary (front) ○ Posterior Pituitary (back) 16 Posterior Pituitary Posterior Pituitary Hormones made by hypothalamus but secreted by posterior pituitary; these hormones act on specific structures rather than affecting other endocrine glands Stores and secretes two hormones: 1. Oxytocin acts on muscles of uterus; induces contractions during childbirth and controls milk secretion during nursing 2. Antidiuretic Hormone (ADH) acts on the kidneys; causes kidneys to increase water retention thus decreasing urine volume; helps regulate the osmolarity of the blood 17 Anterior Pituitary Secretes hormones directly into blood Hypothalamus secretes two kinds of hormones: Releasing hormones makes anterior pituitary secrete its hormones Inhibiting hormones makes anterior pituitary STOP secreting hormones The anterior pituitary secretes many hormones… 18 Anterior Pituitary Hormones Growth Hormone (GH) promotes growth directly and also stimulates growth factors Human Growth disorders are related to GH production: Too much GH (hypersecretion) = gigantism Too little GH (hyposecretion) = pituitary dwarfism; this can be treated using growth hormones from cadavers Insulinlike Growth Factors (IGF) stimulate bone and cartilage growth Prolactin (PRL) similar to GH; produces a variety of effects in different vertebrates (so scientists think this is an ANCIENT HORMONE); mammals = stimulates mammary gland growth and milk synthesis; freshwater fish = salt and water balance 19 Anterior Pituitary Hormones Follicle-stimulating Hormone (FSH) stimulates production of ova and sperm Luteinizing Hormone (LH) stimulates ovaries and testes ** Gonadotropins = stimulate the activity of male and female gonads; FSH and LH are examples 20 Anterior Pituitary Hormones Thyroid Stimulating Hormone (TSH) stimulates the thyroid gland (releases thyroid hormone which increases metabolic rate, raising body temp) Adrenocorticotropic Hormone (ACTH) stimulates the production and secretion of steroid hormones by the adrenal cortex (part of the adrenal gland) Melanocyte-stimulating Hormone (MSH) regulates the activity of pigment-containing cells in the skin; has a role in fat metabolism Endorphins body’s natural opiates; inhibit the perception of pain 21 Consists of 2 lobes on the trachea Thyroid hormone increases the metabolic rate, increasing the body temperature Thyroid has a critical role in vertebrate development & maturation (ex. Human development), homeostasis (blood pressure, heart rate, muscle tone, digestion) The term “thyroid hormone” refers to two closely related hormones: Triiodothyronine (T3) causes changes to target cells Thyroxine (T4) thyroid secretes mainly T4, but the target cells convert it to T3; this hormone stimulates and maintains metabolic processes BOTH T3 and T4 affect metabolic processes; important in bioenergetics Calcitonin LOWERS calcium levels in blood (works antagonistically with PTH) Thyroid Gland 22 23 Thyroid Imbalances Include… Cretinism deficiency in development, retarded skeletal/mental growth, develops in infants from hypothyroidism Goiter deficiency of iodine in diet Hyperthyroidism Too much thyroid hormones; symptoms = weight loss, profuse sweating, high blood pressure Hypothyroidism Too little thyroid hormones; symptoms = weight gain, lethargy Cretinism Goiter 24 Parathyroid Found on the surface of the thyroid; function in homeostasis of calcium ions (very important to the normal functioning of all cells) Parathyroid Hormone (PTH) raises calcium levels in blood; VERY important! Calcitonin decreases calcium levels in the blood PTH and Calcitonin are antagonistic hormones and work together to regulate the calcium levels in the blood (example of homeostasis) 25 Adrenal Gland Adjacent to kidneys Two parts: Adrenal cortex (outside) Adrenal medulla (inside) 26 Close ties to the nervous system – FIGHT OR FLIGHT Catecholamines – secreted in response to positive or negative stress Norepinephrine sustaining blood pressure Epinephrine heart and metabolic rates (Epi pen for anaphylactic shock); also acts as a neurotransmitter; GOOD EXAMPLE of how the endocrine and nervous systems are chemically related Mechanism: *Adrenal medulla under control of nerve cells from sympathetic division *Nerve cells excited by stressful stimulus *Acetylcholine released in adrenal medulla, and combines with receptors to release epinephrine Adrenal Medulla (inside) 27 In contrast to the adrenal medulla, which reacts to nervous input, the adrenal cortex responds to endocrine signals. Corticosteroids include: Glucocorticoids glucose metabolism; increases glucose in blood; secreted in response to stress and promotes the synthesis of glucose from noncarbohydrate substrates (ex. fats and/or proteins) helps with long-term environmental issues Mineralocorticoids helps inflammatory conditions; effects salt and water balance in kidneys BOTH help the body deal with LONG TERM stress (whereas epinephrine and norepinephrine deal with SHORT TERM stress) Adrenal Cortex (outside) 28 Adrenal Medulla vs. Adrenal Cortex 29 Controlled by gonadotropins from the anterior pituitary gland Produced in both males and females (in different proportions); produced in testes in males and ovaries in females; general function = affect growth and development and also regulate reproductive cycles and sexual behavior 3 major types Gonadal Steroids 30 Types of Gonadal Steroids Androgens ex. testosterone; development and maintenance of male reproductive system; produced in an embryo to turn the fetus into a male instead of a female; produced during puberty to stimulate secondary sex characteristics (hair growth, low voice) Estrogens ex. estradiol; effects the female reproductive system and secondary sex characteristics in females Progestins ex. progesterone; prepares and maintains the uterus which supports the growth and development of an embryo 31 Pineal Gland Small mass of tissue near the center of the brain Secretes the hormone melatonin, which regulates functions related to light/dark and seasons marked by changes in day length; related to biological clock rhythms 32 Vertebrate Endocrine System 33 34 Chapter 48 Neurons, Synapses, and Signaling 35 Nervous System Neurons (functional unit of the nervous system) are nerve cells that transfer information within the body. Communication by neurons is based on two distinct types of signals: long-distance electrical signals short-distance chemical signals If an organism does NOT have an integration center, it would not be able to interpret stimuli. 36 -Axons Neurons (nerve cells) -Structural and functional unit of the nervous system -Has a cell body (contains the nucleus) and fiber-like extensions (dendrites and axons) -Dendrites -Short branched; many per cell body; receive INCOMING information and pass it to the cell body -Long; one per cell body; convey OUTGOING messages from the neuron to other cells -Axon hillock – part where the axon joins the cell body -Covered by myelin sheaths (insulated layer) -Synaptic terminals – specialized endings; relay signals from neuron to other cells by releasing chemical messengers called neurotransmitters -Site of contact between a synaptic terminal and a target cell is called a synapse -Presynaptic cell = transmitting cell -Postsynaptic cell = target cell 37 38 -Supporting Cells (called Glia) -Help support the nervous system and help it function properly -Originally thought to only have a structural role, but some synaptic interactions do occur between glia and neurons -In mature CNS, the glia are called astrocytes – they provide metabolic and structural support for neurons -Help form the blood-brain barrier restricts passage of most substances into the brain which controls the extracellular chemical environment of the CNS (FORMED BY TIGHT JUNCTIONS) -Oligodendrocytes (in CNS) and Schwann cells (in PNS) are glia that form myelin sheaths around the axons of neurons -Necessary b/c can’t use regular cell membranes b/c they are made of lipids which are poor conductors of electrical currents; the myelin works better 39 Overview -Nervous system is made up of living neurons -Neurons are specialized for the fast transmission of impulses -Three major overlapping functions: -Sensory Input sensory receptors take info from inside body and outside world and convey it to integrations centers -Integration carried out in the CNS (central nervous system; brain and spinal cord); input is interpreted and body responds appropriately; if there was no integration center, organisms wouldn’t be able to interpret stimuli -Motor Output conduction of signal from integration center to the effector cells (muscles or glands that carry out the signal) -Signals are conducted by nerves -PNS (peripheral nervous system) = nerves that communicate motor and sensory signals between the CNS and the rest of the body -Information is communicated by both electrical and chemical signals 40 Cerebrospinal Fluid Made in the brain by filtering the blood; fills the space in the brain and spinal cord 41 The Nature of Nerve Signals -Nerve signals are changes in voltage across the membrane due to movement of ions -Membrane Potential the potential charge difference between the cytoplasm and the extracellular fluid of a cell -Resting Potential membrane potential of an unstimulated neuron -Can measure membrane potential as a voltage; typical animal cell is – 50 to –100 mV (the negative means the inside of the cell is negative in charge w.r.t the outside)…in resting neurons, the membrane potential is more negative than the threshold potential The inside of the cell is NEGATIVELY charged in comparison to the outside of the cell 42 -Differences in membrane potential are sustained by the actions of the sodiumpotassium pump -Na+ pumped OUT (3 at a time) -K+ pumped IN (2 at a time) -THEREFORE…outside = positive; inside = negative -Goes against the gradient, so needs to use energy (ATP) active transport -Ion channels are selective for specific ions; so a membrane can have different permeability's to different ions -They determine WHAT can pass through, but not the RATE Sodium Potassium Pump 43 Gated Ion Channels Gated ion channels are specialized proteins that span the membrane, and allow ions to diffuse back and forth across the membrane according to their respective gradients. Chemically-gated ion channels respond to a chemical stimulus (ex. neurotransmitter) Voltage-gated ion channels respond to a change in membrane potential Allows only ONE kind of ion to pass through 44 -Graded Potentials magnitude of change depends on the strength of the stimulus (larger stimulus will open more channels) -Hyperpolarization – increase in voltage across the membrane -Open K+ channel; K+ flows out and causes the inside of the cell to become more negative -Depolarization – reduction in the voltage across the membrane -Open a Na+ channel; Na+ flows in and causes the inside of the cell to become more positive 45 -Action Potentials ALL OR NOTHING depolarization -DEPOLARIZATION causes an action potential -Triggered by graded potentials -When it reaches a certain point, the threshold potential (usually 15-20 mV more positive than the resting potential) it causes an action potential (NERVE IMPULSE!); all or none event SEE Fig. 48.11 -Occurs in the axons (not dendrites) pg. 1068 -HYPERPOLARIZATION does NOT cause action potentials explains everything -Action Potential Mechanism: perfectly… -Resting State – Na+ and K+ channels closed -Threshold – some stimulus opens Na+ channels; it reaches threshold potential, and therefore more Na+ channels open triggering an action potential -Depolarization - because Na+ channels are open and K+ channels are closed, the inside of the cell becomes more positive -Repolarization – Inactivation gates close the Na+ channels and the K+ channels open; K+ leaves the cell and the inside becomes more negative than the outside -Undershoot – K+ gates remain open because they are slow, but the Na+ gates are closed; resting state is restored very quickly (hyperpolarization happens for a millisecond) Action potentials arise because some ion channels in neurons are voltage-gated ion channels, opening or closing when the membrane potential passes a particular level 46 47 -Because both gates of the Na+ channel are closed, if another stimulus arrives during this period, it is unable to trigger a change (inactivation gates had not had time to open back up yet) called refractory period (neuron is insensitive to depolarization) -It is the number of action potentials per second, not their amplitude, that codes for a stimulus intensity in the nervous system -Action potentials propagate themselves along an axon (like tipping over the first of a long line of dominoes) -Factors that affect the speed of the action potentials (how fast they go along the axon): -Diameter of axon (larger diameter faster transmission) -Saltatory conduction action potentials that jump from node to node 48 Synapses -Communication between cells occurs at synapses -Synapses – unique cell junctions that control communication between a neuron and another cell; two types: electrical or chemical -Electrical Synapses -Allows action potentials to spread from presynaptic cell to postsynaptic cell via gap junctions -Not as common as chemical synapses -Chemical Synapses -Very common -Chemical synapses are called synaptic clefts; they separate presynaptic cell from postsynaptic cell -The cleft prevents an action potential from going directly from the pre to the postsynaptic cell -A series of events converts the electrical signal of the action potential arriving at the synaptic terminal into a chemical signal that travels across the synapse, where it is converted back into an electrical signal in the postsynaptic cell. (electrical signal chemical signal electrical signal) Fig. 48.16 pg. 1072… 49 ***A series of events converts the electrical signal of the action potential arriving at the synaptic terminal into a chemical signal that travels across the synapse, where it is converted back into an electrical signal in the postsynaptic cell. (electrical signal chemical signal electrical signal) 1. An action potential DEPOLARIZES the PRESYNAPTIC membrane 2. The depolarization opens voltage gated channels, allowing Ca 2+ to enter the cell (neuron). 3. Calcium causes synaptic vesicles to fuse with the pre-synaptic membrane 4. Neurotransmitters are released into the synaptic cleft 5. Neurotransmitters bind to the POSTSYNAPTIC membrane 6. Ion channels open, allowing Na+ and K+ ions to enter the postsynaptic cell 50 -Neurotransmitters (intracellular messengers) are held in the tip of the pre-synaptic axon -Action potential releases these neurotransmitter molecules into the synapse (the action potential depolarizes the membrane) -The postsynaptic membrane has special receptors for neurotransmitters -Neurotransmitter binds opens ion channels (chemically gated!) – postsynaptic membrane is either hyperpolarized or depolarized (depending on receptor) -Neurotransmitter is removed quickly (enzyme degradation) therefore the effect is brief and precise -NOTE: nerve impulses can only transmit ONE way Structure of a Chemical Synapse 51 -BOTH -Graded potentials -The electrical impact on the postsynaptic cell decreases with the distance away from the synapse -Excitatory EPSP -Allows Na+ in and K+ out (more permeable to Na+, so more of that is allowed in) -Inside of cell becomes positive = DEPOLARIZES the plasma membrane (gets it closer to the action potential) -Excitatory Postsynaptic Potential (EPSP) the name for the whole process that uses an excitatory synapse -Inhibitory NO ACTION POTENTIAL! IPSP -K+ out and Cl- in (higher permeability to K+) -Inside of cell becomes negative = HYPERPOLARIZE the plasma membrane -Inhibitory Postsynaptic Potential (IPSP) the name for the process that uses an inhibitory synapse Excitatory Synapse vs. Inhibitory Synapse 52 53 Summation -Several synaptic terminals working simultaneously on the same postsynaptic cell can have an additive effect summation! -Temporal Summation one or more synaptic terminals rapid fire with signals (voltage has no time to return to resting) -Spatial Summation several synaptic terminals (on DIFFERENT cells) all send signals to the same postsynaptic cell (additive effect) 54 Neurotransmitters -Same neurotransmitter can produce different effects on different types of cells (depends on the receptors) -Major neurotransmitters -Acetylocholine – most common; vital for nervous system functions that include muscle stimulation, memory formation, and learning; can be either inhibitory or excitatory -Biogenic Amines – derived from amino acids -Epinephrine & Norepinephrine (excite and inhibit) MORE ON THESE NEXT CHAPTER -Dopamine (generally excite) affect sleep, mood, attention, and learning -Serotonin (generally inhibit) affect sleep, mood, attention, and learning -Amino Acids – -GABA (gamma aminobutyric acid) – found at most inhibitory synapses; creates IPSP (increases Cl- permeability) no action potential -Neuropeptides – short chains of AA’s -Substance P – excite Signal; mediates perception of pain -Endorphins – decreases perception of pain; emotional effects 55 Gas signals of Nervous System -Nitric Oxide (NO) NO diffuses into neighboring target cells, produces a change, and is broken down within a few seconds; in its target cells, NO works like many hormones, stimulating an enzyme to synthesize a second messenger that directly affects cellular metabolism - Carbon Monoxide (CO) In the brain, CO regulates the release of hypothalamic hormones; in the PNS, it acts as an inhibitory neurotransmitter that hyperpolarizes intestinal smooth muscle cells -Gasses not stored; cells make them on demand - They are used as LOCAL regulators 56 Chapter 49 Nervous Systems 57 Evolution and Diversity of Nervous Systems -Great Diversity in organization of new systems -Lack nerve systems (sponges) -Nerve nets (cnidarians) -Cephalization (neurons clustered in head) -Nerve cords (planarians) -Clearly defined CNS….etc. 58 Glia and Blood Brain Barrier -The major types of glia (connective tissue of nervous system) nourish, support and regulate neurons. -Oligodendrocytes and Schwann cells function in axon myelination, a critical activity in the vertebrate nervous system. -Astrocytes induce cells that line the capillaries in the CNS to form tight junctions. The result is the blood-brain barrier, which controls the extracellular environment of the CNS by restricting the entry of substances from the blood. 59 The brain integrates the complex behavior of vertebrates. The spinal cord conveys information to and from the brain and generates basic patterns of locomotion. The spinal cord acts independently as part of the simple nerve circuits that produce reflexes, the body’s automatic responses to stimuli (ex. pulling hand away from hot stove.) Cerebrospinal fluid is formed in the brain by filtering blood. In mammals, it fills the spaces in the brain and the spinal cord. The function is to act as a shock absorber. The brain and the spinal cord contain gray and white matter. Gray matter consists of cell bodies, dendrites, and unmyelinated axons. White matter contains axons with myelin sheaths. Central Nervous System 60 Vertebrate Nervous System CNS brain and spinal cord PNS everything else! Parts of the peripheral nervous system: - Sensory (AFFERENT) division incoming neurons - Motor (EFFERENT) division outgoing neurons motor subdivides: - Somatic carries signals to SKELETAL muscles - Autonomic regulates internal environment autonomic subdivides: - Sympathetic ACTIVE (fight/flight) - Heart beats faster, arousal/energy Cerebrospinal Fluid = - Parasympathetic INACTIVE (rest/digest) made in the brain by filtering blood; fills the - Calming/conserving energy/ selfspaces in the brain maintenance and spinal cord - Enteric control the organs of the digestive, cardiovascular, excretory, and endocrine systems 61 Actions of two divisions of autonomic system 62 The Brain - The vertebrate brain has three major regions: the forebrain, midbrain, and hindbrain. - The FOREBRAIN activities include processing olfactory input (smell), regulation of sleep, learning, and any complex processing. Cerebrum, Diencephalons, Thalmus, Hypothalamus, Epithalmus - The MIDBRAIN coordinates routing of sensory input - The HINDBRAIN controls involuntary activities, such as blood circulation, and coordinates motor activities, such as locomotion. Pons, Medulla oblongata, Cerebellum 63 Brainstem (lower brain) - Major Functions: homeostasis, coordination of movement; conduction of information to higher brain centers - Consists of 3 parts - Medulla oblongata controls homeostatic functions (including breathing, swallowing, digestion, heart and circulation) - Pons also helps control automatic functions (“assists” medulla) - Midbrain acts as a projection center; sends coded sensory information to forebrain 64 65 Cerebellum Develops from the metencephalon (hindbrain) Functions in coordination; muscle actions; involved in learning and remembering motor responses Balance, hand-eye coordination 66 Thalamus/ Hypothalamus Develops from diencephalon (forebrain) Epithalamus – produces cerebrospinal fluid Thalamus – main input center for sensory information going to cerebrum and main output center for motor information leaving the cerebrum Hypothalamus – important in homeostatic regulation - Source of hormones - Regulates the pituitary gland - Body’s thermostat - Regulates hunger/thirst - Role in sexual/mating behaviors; fight or flight; pleasure/rage Circadian Rhythms - Regular, repeated rhythmic behaviors (sleep/ wake) - Hormone release and sex drive 67 Most HIGHLY DEVELOPED STRUCTURE of the mammalian brain Divided into left and right hemispheres; each hemisphere consists of: Gray matter (cerebral cortex) – covering White matter – internal part Basal nuclei – found deep within the white matter; important in planning and learning movement sequences Cerebral Cortex (“gray matter”) LARGEST and MOST COMPLEX part of the mammalian brain Evolved a lot through evolution Neocortex – 6 layers of tissue outside of the cortex; unique to mammals ○ Right half of brain controls the functions of the left side of the body; left half controls the right side Corpus callosum – part of the brain that communicates between the left and right hemispheres Cerebrum 68 Lobes of Cerebrum Frontal, Parietal, Temporal, Occipital Primary motor cortex and primary somatosensory cortex form the boundary between the frontal lobe and parietal lobe Motor Cortex sends commands to skeletal muscles Somatosensory Cortex gets and integrates signals from touch, pain, pressure and temp receptors throughout the body Frontal Lobe speech, motor cortex, emotions Parietal Lobe somatosensory cortex, taste, speech, reading, touch, pain, pressure, temp SIDES OF THE Temporal Lobe smell, hearing CEREBRUM Occipital Lobe vision Left Side adept at language, math, logic, serial sequences of information Right Side pattern recognition, space recognition, spatial relations, nonverbal, emotions 69 70 Reticular Formation Arousal and sleep are controlled in part by the reticular formation, a system of neurons that passes through the brainstem 71 Emotions Due to frontal lobe and limbic system Limbic System forms a ring around the brainstem; composed of hippocampus and the olfactory cortex Responsible for emotions (laughing, crying, feeding, aggression, sexuality) Amygdala nucleus in the temporal lobe; recognizes emotional content of facial expressions and emotional memories Interesting note: frontal lobotomies, which disrupt the frontal lobes and limbic system, used to be performed to treat severe emotional disorders 72 Language and Speech Processed by multiple areas of the cortex Broca’s area – frontal lobe controls the muscles in the face Wernicke’s area – temporal lobe controls the ability to comprehend speech but not the ability to speak 73 Memory and Learning Short term memory (frontal lobe) released if memory is irrelevant Long term memory (limbic system, hippocampus) if info is pertinent; goes from short term to long term with repetition (“practice makes permanent”…not always perfect!) Skill memory ex. walking, riding a bike, etc; once learned, it is hard to unlearn; learned by repetition (bad habits are hard to break!) practice makes permanent 74 Research for CNS Injuries CNS can’t repair itself Nerve Cell Development Neurons develop by cell to cell communication, control of gene expression, and genetic basis HARD TO REPLICATE!! Axons grow to target cells and use molecular signals to direct them (don’t grow in a straight line) Sequence and time of development are important – therefore, again, it is HARD TO REPLICATE Scientists are trying to get axons to regrow using different combinations of proteins Neural Stem Cells In adults, new cells are found in the hippocampus (memory/ learning) Function of the new stem cells = unclear! Issues with stem cell research what can we use as a source?!?! LOTS OF DEBATES OVER THIS!! 75 Relationship and similarities between nervous and endocrine systems * use chemical signals * response depends on action of receptor * chemical messengers produced by axons in parts of both 76