WarmUp 1 Name the 2 main organs of
- Slides: 99
Warm-Up 1. Name the 2 main organs of the nervous system. 2. Draw and label the parts of a neuron.
Warm-Up • Label the parts of the neuron below. A D C B G E F
Warm-Up 1. One neuron transmits a nerve impulse at 40 m/s. Another conducts at the rate of 1 m/s. Which neuron has a myelinated axon? 2. List the following in order: A. K+ channels open and K+ floods out of cell B. Membrane is polarized (resting potential) C. Neurotransmitters are released from vesicles into synaptic cleft D. Na+ channels open and Na+ floods into cell E. Stimulus triggers membrane depolarization 3. What restores the resting potential of a neuron?
The Nervous System
Nervous System • Master controlling and communicating system
Basic Functions 1. Sensory input – gather information Sensory input 2. Integration – process and interpret sensory input 3. Motor output – response by muscles and glands Motor output
Organization A. Central Nervous System (CNS) ▫ Brain & spinal cord ▫ Integrative and control centers B. Peripheral Nervous System (PNS) ▫ Nerves (spinal nerves, cranial nerves) ▫ Communication lines between CNS and rest of body ▫ Two Divisions: 1. Sensory (afferent) Division: Sensory receptors Sensory (afferent) Division CNS 2. Motor (efferent) Division: CNS effectors Motor (efferent) Division (muscles & glands)
Motor Division • Somatic nervous system (voluntary) – control Somatic nervous system skeletal muscles • Autonomic nervous system (ANS) (involuntary) – regulate smooth muscles, cardiac, glands ▫ Subdivisions: sympathetic & sympathetic parasympathetic
Nervous Tissue 1. Neurons (nerve cells) - transmit message Anatomy: ▫ ▫ ▫ Cell body – contains nucleus; metabolic center Dendrite – fiber that conveys messages toward cell body Axon – conduct nerve impulses away from the cell body Axon terminals – end of axon; contain neurotransmitters & release them Synaptic cleft/synapse – gap between neurons
Nervous Tissue 2. Supporting cells (Neuroglia) Neuroglia CNS: astrocytes, microglia, ependymal cells, oligodendrocytes barrier between capillaries and neurons protect neurons immune/defense line brain and spinal cord cavities wrap nerve fibers produces myelin sheaths (covering) PNS: Schwann cells, satellite cells surround large neurons protect & cushion
• • Myelin: whitish, fatty material that covers nerve fibers to speed up nerve impulses Schwann cells: surround axons and form myelin sheath Myelin sheath: tight coil of wrapped membranes Nodes of Ranvier: gaps between Schwann cells Nodes of Ranvier
• • Ganglia: collections of cell bodies Ganglia Bundles of nerve fibers = tracts (CNS) or nerves (PNS) White matter: dense collections of myelinated fibers White matter Gray matter: unmyelinated fibers & cell bodies Gray matter
It’s a Mad, Mad Neuron
Classification of Neurons
1. Functional Classification: direction nerve impulse is traveling Sensory neurons Motor neurons Interneurons carry impulses from sensory receptors to CNS carry impulses from CNS to muscles & glands connect sensory & motor neurons Vision, hearing, equilibrium, taste, smell, pain, pressure, heat
2. Structural Classification: # processes extending from cell body Multipolar Bipolar Unipolar 1 axon, several dendrites 1 axon, 1 dendrite 1 process Rare Short with 2 branches (sensory, CNS) Most common (99%) Eg. Motor neurons, Eg. retina, nose, ear interneurons Eg. PNS ganglia
Nerve Impulses
Neuron Function 1. Irritability: ability to respond to stimulus & Irritability convert to nerve impulse 2. Conductivity: transmit impulse to other Conductivity neurons, muscles, or glands
Exciting a Neuron: • Cell membrane at rest = polarized ▫ Na+ outside cell, K+ inside cell ▫ Inside is (-) compared to outside • Stimulus excited neuron (Na+ rushes in) becomes depolarized • Depolarization activates neuron to transmit an action potential (nerve impulse) action potential ▫ All-or-none response ▫ Impulse conducts down entire axon • K+ diffuses out repolarization of membrane • Na+/K+ ion concentrations restored by sodiumpotassium pump (uses ATP) potassium pump
Resting membrane potential (-70 m. V)
Gated Ion Channels (Na+ and K+)
Depolarization
• Saltatory conduction: electrical signal jumps from Saltatory conduction node to node along myelinated axon (30 x faster!)
Multiple Sclerosis (MS) • Autoimmune disease • Myelin sheaths destroyed reduced to hardened lesions (scleroses) • Blindness, muscle weakness, speech disturbance, urinary incontinence • Treatment: interferons, glatiramer (hold off attacks)
Nerve Conduction • Action potential reaches axon terminal vesicles release neurotransmitters (NT) into synaptic cleft (NT) • NT diffuse across synapse bind to receptors of next neuron • Transmission of a nerve impulse = electrochemical event
Neuron Talk
Neurotransmitters • • 50+ identified Excitatory: cause depolarization Excitatory Inhibitory: reduce ability to cause action potential Inhibitory Eg. acetylcholine, serotonin, endorphins
Mouse Party
Neurotransmitters Neurotransmitter Action Affected by: Acetylcholine muscle contraction botulism, curare (paralytic), nicotine Dopamine “feeling good” cocaine, amphetamines Serotonin sleep, appetite, nausea, mood, migraines Prozac, LSD, ecstasy Endorphins inhibit pain morphine, heroin, methadone GABA main inhibitory NT alcohol, Valium, barbiturates
Reflexes • Rapid, predictable, involuntary responses to stimuli 1. Somatic Reflexes: stimulate skeletal muscles ▫ Eg. jerking away hand from hot object 2. Autonomic Reflexes: regulate smooth muscles, heart, glands ▫ Eg. salivation, digestion, blood pressure, sweating
Reflex Arc (neural pathway) Five elements: 1. Receptor – reacts to stimulus 2. Sensory neuron 3. CNS integration center 4. Motor neuron 5. Effector organ – muscle or gland
Reflex Activities Patellar (Knee-jerk) Reflex Pupillary Reflex
Patellar (Knee-jerk) Reflex • Stretch reflex • Tapping patellar ligament causes quadriceps to contract knee extends • Help maintain muscle tone, posture, & balance Pupillary Reflex • Optic nerve brain stem muscles constrict pupil • Useful for checking brain stem function and drug use
Flexor (withdrawal) reflex: painful stimulus withdrawal of threatened body part ▫ Pin prick Plantar reflex: draw object down sole of foot curling of toes ▫ Babinski’s sign: check to see if motor cortex or corticospinal tract is damaged
Voluntary Reactions • More neurons and synapses are involved longer response times Reflex = Involuntary Reaction Voluntary Reaction
Warm-Up 1. List and describe the 5 elements of a reflex arc. 2. List an example of a reflex. 3. What is the difference between a reflex and a voluntary reaction?
Human Brain
4 Major Regions 1. Cerebral Hemispheres 2. Diencephalon 3. Brain stem 4. Cerebellum
1. Cerebral Hemispheres (Cerebrum) L & R hemispheres Corpus callosum: large fiber tract; connects 2 hemispheres Lobes: major regions (named for cranial bones) Parietal, Parietal frontal, frontal occipital, occipital temporal Gyri (gyrus) = elevated ridges of tissue Sulci (sulcus) = shallow grooves Fissures = deeper grooves, separate large regions of brain Motor & sensory function: opposite hemispheres
• Grey matter. Cortex Cerebral • “Executive suite” conscious mind
Functions of the Major Lobes
2. main Diencephalon 3 structures: (interbrain) 1. Thalamus: relay station for incoming info 2. Hypothalamus: A. B. C. D. E. F. Autonomic control center (heart rate, BP, digestion) Emotional response (limbic system) Body temperature regulation Regulate food intake Sleep-wake cycles Control endocrine system pituitary gland at base 3. Epithalamus: pineal gland (sleep-wake cycle)
Diencephalon
3. Brain Stem • Programmed, automatic behaviors for survival • 3 regions: 1. Midbrain: vision, hearing, reflex 2. Pons: breathing 3. Medulla oblongata: heart rate, BP, breathing, swallowing, vomiting, coughing, sneezing
Brain Stem
4. Cerebellum • Balance, equilibrium, timing of skeletal muscle activity
Protection of CNS • Meninges: connective tissue covering CNS structures ▫ Dura mater (leathery outer), arachnoid mater (web-like middle), pia mater (surface of brain) ▫ Meningitis: inflammation of meninges; bacterial or viral infection • Cerebrospinal fluid (CSF): watery cushion to protect NS from trauma ▫ Lumbar (spinal) tap – test for infection, tumors, multiple sclerosis
Meningitis
Symptoms of Meningitis
Treatment for Meningitis • Bacterial antibiotics • Herpes meningitis antiviral meds • IV fluids • Prevention: vaccines for bacterial infections (Hi. B)
Blood-Brain Barrier: endothelial cells in capillaries prevent substances from crossing into brain NO: YES: • • • Urea Toxins Proteins White blood cells Bacteria Most drugs Water Glucose Amino acids Gases Fat-soluble substances • Some drugs: anesthetics, alcohol, nicotine
The Senses
Special senses • • • Smell Taste Sight Hearing “Touch” = temperature + pressure + pain of skin, muscles, & joints • Equilibrium (in the ear)
• Large complex organs (eyes, ears) Sensory Receptors • Localized clusters of receptors (taste buds, olfactory epithelium)
Vision Tests
Are the squares inside the blue and yellow squares all the same color?
Bezold effect The smaller squares inside the blue and yellow squares are all the same color. They seem different (magenta and orange) because a color is perceived differently depending on its relation to adjacent colors (here blue or yellow depending on the outer square).
Are the horizontal lines straight or crooked?
Café Wall Illusion The horizontal lines are straight, even though they do not seem straight. In this illusion, the vertical zigzag patterns disrupt our horizontal perception.
Does Lincoln’s face look normal?
Some neurons in the brain seem specialized in processing faces. Faces are usually seen upright. When presented upside down, the brain no longer recognizes a picture of a face as a face but rather as an object. Neurons processing objects are different from those processing faces and not as specialized. As a consequence these neurons do not respond to face distortions as well. This explains why we miss the weird eyes when the face is inverted.
Can you see a baby?
Illusory Contour The baby’s head is on the left, the baby’s feet are against the trunk of the tree on the right. Illusory Contour: a form of visual illusion where contours are perceived without a luminance or color change across the contour
How quickly can you say the color of the words below?
Taste Tests
Jellybean Test
Flavor = taste + smell
5 Types of Taste Receptors
Aging • After age 50, ability to smell and taste decrease • Membranes lining nose become thinner & drier olfactory nerve deteriorate • # taste buds decrease with age more difficult to detect sweet/salty foods taste more bitter • As people age, their food tastes more bland eat less possible malnutrition
Genetics of Taste
PTC = phenylthiocarbamide • Discovered in 1931 by when a Du. Pont chemist named Arthur Fox accidentally released a cloud of fine crystalline PTC in the lab. • A nearby colleague complained of the bitter taste, while Dr. Fox tasted nothing. • Fox continued to test the taste buds of family and friends, setting the groundwork for future genetic studies.
of PTC Tasting • Genetics Gene for tasting PTC (Tas 2 r 38) is located on Chromosome 7. • PAV = taster (T), AVI = nontaster (t), AAV = another allele ▫ PAV-PAV = TT = very bitter ▫ PAV-AVI = Tt = somewhat bitter TAS 2 R 38 ▫ AVI-AVI = tt = nontaster • General Population: 70% Tasters, 30% Nontasters
Bitter tastes = Result of selection pressures? • Thiocynate Compounds (bitter taste) found in broccoli, cauliflower, mustard family ▫ Tasters: avoid these foods in diet ▫ Nontasters: more varied diet, include green leafy veggies • Thiocynates might inhibit thyroid function tasters may have protection against thyroid diseases
Bitter tastes = Result of selection pressures? • Poisons = bitter taste ▫ Tasters: part of hunter-gatherer societies? • Genetic Drift ▫ Europeans: all 3 alleles (PAV, AVI, AAV) ▫ Asians: AAV allele rare ▫ Native Americans: 98% have PAV allele only
Denver Museum of Nature and Science • Expedition Health: Genetics of Taste Study • Purpose of Study: ▫ Is ability to taste bitter compounds related to what foods you eat, your % body fat, and BMI? ▫ Is your ability to taste bitter compounds related to your genetic ancestry?
Substances related to PTC • Thiourea (thiocarbamide) – very bitter!!! • Sodium benzoate – sweet, salty, bitter, no taste ▫ Food preservative
Family Pedigree • Tasters: ▫ Supertasters (TT) ▫ Tasters (Tt) • Non-tasters (tt)
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