BIOS 1710: Biological Sciences II, Week 2 Notes
BIOS 1710: Biological Sciences II, Week 2 Notes BIOS1710
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This 10 page Class Notes was uploaded by Sydney Jones on Friday September 2, 2016. The Class Notes belongs to BIOS1710 at Ohio University taught by Scott Moody in Fall 2017. Since its upload, it has received 90 views. For similar materials see Biological Sciences II: Ecology, Evolution, Animal Body Systems in Biology at Ohio University.
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Date Created: 09/02/16
Week 2 Aug 29-Sept 2 Ch 36 Sensory Systems Receptors- what allows us to sense the physical properties of the environment Receptors Sensory Recepors Sensory Organs protein neruon Sensory Transduction- conversion of physical or chemical stimuli into nerve impulses Types of Sensory Receptors: • Chemoreceptors- perceive specific molecules • Mechanoreceptors- respond to touch or pressure • Thermoreceptors- detect temperature changes • Nociceptors- sense pain or harmful stimuli • Photoreceptors- respond to wavelength of light • Electroreceptors detect electrical fields Effective Transduction Strength of signal - Intensity is not based on size of action potential but firing rate Firing rate- number of action potential fired over a period of time (spatial/temporal summation) Low intensity ▯ low firing rate High intensity ▯ high firing rate Continuous Stimuli - Allows us to ignore background ‘noise’ by adaptation Adaptation- receptors reducing their firing rate Locating the signal Lateral Inhibition- enhances the strength of a sensory signal locally but diminish it peripherally Mechanoreceptors Interneurons Olfactory-Smell • -Humans (and most mammals) have nearly 1,000 genes for expression olfactory receptors ▯ Meaning 5% of our genes are for smell o each neuron has one type of receptor o half (in humans) do not work because of mutations • receptors are coupled with G-proteins (molecular switches) which activate cAMP to open K and Na channels How: 1. Molecules/odorants bind to their receptors 2. Action potential is sent up the axon to the glomeruli in the olfactory bulb 3. Sent to interneurons 4. Integrate information then sent to brain Olfactory Bulb Glomeruli Gustation- Taste • Each taste bud ahs 100 taste cell and a 10 day life span • Humans have about 10,000 taste buds 5 basic tastes: 1. Sweet: they think there are 3 different receptors 2. Sour: protons; controlled by pH, lower pH= more sour 3. Bitter: 40-80 genes 4. Salty: from Na entering the channel creating action potential 5. Savory Sensing Gravity, Movement, and Sound Hair Cells- sense movement and vibration -When a pressure wave bends sterocillia it opens K channels Lateral Line System- where hair cells are in sharks and fish to detect motion and things nearby Gravity Sensing Organs Statocysts- organ found in most invertebrates; internal chamber lined by hair cells that project into the chamber Statolith- free to move around in the statocysts and propelled by gravity; when pressed up against hair cells it locates direction of gravity The Ear Hearing- ability to sense sound, which consists of waves of pressure in air or water Frequency- difference in pitch Humans- 20 Hz- 2,000Hz Dogs- up to 44,000 Hz Elephants- 1Hz Amplitude- determines loudness Important parts of the ear: • Pinna- enhances the reception of sound waves; outer ear • Tympanic Membrane (eardrum)- transmits sound into the ear; outer ear • Malleus, Incus, and Stapes- amplifies the waves; bones; middle ear • Oval Window- then membrane; attached the stapes and part of the cochlea, inner ear • Cochlea- a coiled chamber; contains hair cells; means snail in Latin; inner ear Vestibular System- organs that make up the inner ear -provide a sense of gravity and body orientation - has hair cells -sense angular motions of the head in three perpendicular planes (Allows us to hold a gaze while in movement) Process of hearing: 1. Outer ear pushes pressure waves into the ear canal and tympanic membrane at the same frequency 2. Amplified (30x) by the 3 bones of the middle ear 3. Vibrates against the oval window 4. Oval window generates the waves to the fluid of the cochlea where transduction takes place 5. Hair cells sense the waves The Cochlea -Contains the organ or corti - Has hari cells that are supported by the basilar membrane on the bottom (can move) Visual of Cochlea ‘rolled out’ with pressure waves Narrow- stiff and responds to high frequencies; 20,000 Hz These die off first Wide- flexible and responds to low frequencies YouTube video of cochlea animation https://www.youtube.com/watch?v=dyenMluFaUw Deafness Conduction Deafness- loss of function of the tympanic membrane or ossicles of the middle ear; ossicles stiffen with age causing loss of ability ot hear high frequency sounds Nerve Deafness- caused by inner ear or auditory pathway damage, including damage to hair cells Vision Electromagnetic Receptors- respond to electrical, magnetic, and light stimuli **Light-detecting photoreceptors are the most common and diverse Types of Eye Structures 1. Eyecups a. Flatworms have two on the dorsal surface b. Detect the direction ad intensity or light sources c. Pigmented epithelium blocks light so light is only received from above and in front 2. Compound eye a. Insects and crustaceans b. Some can see ultraviolet light c. Ommatidia- light-focusing, number in eye determines the resolution i. In a single ommatidia light is focused through a lens onto overlapping photoreceptors ii. Sensitive to about 1°-2° of light in visual field 3. Single-lens Eye a. Vertebrates and cephalopod mollusks b. Work like a camera c. Focus light rays on a particular region of photoreceptors d. Can detect objects by motion and shape e. Some spiders have this Anatomy of the Human Eye Sclera- tough, white outer layer, covers the eye, mucus production to keep the eye moist Choroid- carries blood vessels for nourishment Cornea- front of the eye, part of the sclera, transparent Pupil- light enters through this opening Convex Lens- light passes through ▯ close object= rounded, distant object= relaxed and flatten *If this becomes cloudy you get cataracts Ciliary Muscles- attached between sclera and lens, contraction/relation adjusts the lens to focus image Iris- opens and closes to adjust the amount of light, surrounds the pupil, gives eye color Aqueous Humor- interior region in front of lens, filled with clear water liquid that is produced and drained constantly by small ducts at base of eye ▯ blockage can increase pressure and can cause glaucoma possible blindness Vitreous Humor- large cavity behind lens, filled with a gel-like substance, makes up most of the eye’s volume Retina- initially process light stimuli thin tissue, contains photoreceptors, cornea and lens bend light and focuses them here, light rays cross: flip image up to down and left to right Why do we have two eyes?? For binocular vision allowing for depth and distance perception *ability to combine images form both eyes to produce one image Detecting Light Opsin- photosensitive protein, converts light energy into electrical signals, cylindrical groups in the plasma membrane of most photosensitive cells Retinal- derivative of vitamin A, absorbs light Rhodopsin- transmembrane protein found photosensitive cells of vertebrates, covalently bout to retinal -Photosensitive cells are modified neurons with leaky Na channels -Resting membrane potential (in the dark) is less negative about 34mV Steps: 1. Retinal absorbs light photo 2. Conformational change from sis to trans configuration 3. Causes Na channels to close 4. Cell membrane becomes hyperpolarized and neurotransmitter release is reduced -Photoreceptors do not fire action potential but inhibit the fire rate of other neurons in the eye when stimulated by light energy ▯ provides information about the intensity and pattern of light received ***In summery: when light photons hit a receptor it closes the Na channel NOT opens it; usually it is a ‘dark current’ for depolarization Color Vision -by photoreceptor cells that contain visual pigments sensitive to different wavelength of lights - Rods and cones have disks where opsin is Cone Cells- color-sensitive pigments, provide the sharpest vision, 6 million -Absorb light at blue (short), green (medium), or red (long) wavelengths -Color-blind people lack function in green and/or red cones * this is a sex linked gene their for it is more common in males Rod Cells- allow animals to see in low light more than cone cells, sensitive to light, detect shades from white to black, found periphery of the eye to detect motion in the periphery at night, 125 million **Rod and cone cells make up about 70% of all sensory receptors cells in the human body Why is it harder to see color at night? Cone cells have a low sensitivity to light Fovea- cone cells are most concentrated here, no rod cells, center of the visual field Color in Animals: -Depends on number of cones and particular opsin -Nocturnal animals have few cones but many rods -Some deep see fish have two opsin for blue -Birds, insect, and some mammals can see ultraviolet light -Rattlesnakes and pit vipers and infrared light to detect prey in the dark Cellular Organization -retina consist of five layers of neurons How: 1. Rods and cones synapse on to bipolar cells- do not fire action potential, adjust their release of neurotransmitter 2. Bipolar cells synapse onto ganglion cells- located on the front of the retina 3. If activated transmits action potential by the *optic nerve to the visual cortex *begins at the front of the retina and exits at the back; creates an area with out light-sensitive cells (Blind Spot) Horizontal Cells- communicate between neighboring airs of photoreceptors and bipolar cells ▯ enhances contrast to sharpen the image Amacrine Cells- communicate between neighboring bipolar cells and ganglion cells ▯ enhancing motion detection and adjusting for changes in illumination of surroundings Functional Studies of the Brain Brain Mapping • Electrical stimulation o You do not have pain receptors in the brain so you can have an awake brain surgery o They would stimulate parts of the brain and see what the reaction would be • fMRI • Lesion Studies o Broca’s Patient ▯ Found that the frontal area is where language was used ▯ Broca’s Area of the brain o HM ▯ Had sever epilepsy ▯ Removed the hippocampus ▯ When doing so he was no longer able to retain new memories o Phineas Gage ▯ Had a work related accident that ended with a pipe through his skull in the frontal lobe ▯ He survived but had impulse control and anger issues The Brain Major Regions 1. Forebrain a. Cerebral Cortex b. Thalamus c. Hypothalamus 2. Midbrain a. Part of the brain stem 3. Hindbrain a. Pons b. Medulla (part of the brainstem c. Cerebellum **Basic body functions and behaviors- hindbrain and midbrain Advanced cognitive functions- forebrain, particularly cerebral cortex ▯ much larger in mammals, especially humans Structures: Cerebellum- coordinates complex motor patters Brain Stem- autonomic center Thalamus- relays sensory information to the cerebrum Hypothalamus-controls homeostasis and releases hormones Cerebrum- cerebral cortex is the thin outer layer, bulk of the brain, divided into life and right hemispheres (each having 4 lobes) by a thick band of axons called the corpus callosum, involved in conscious thought and memory Limbic System- Part of the forebrain (medial temporal lobe); involved in drives, emotion, memory formation Hippocampus- part of the limbic system; long-term memory Amygdala- part of the limbic system, controls fear (fight or flight response) Four Lobes of the Brain - cerebral hemispheres are the larges structures of the mammalian brain and consists of a highly folded outer layer of gray matter (4mm thick) called the cortex Why is the cortex folded? To increase surface area to increase amount of neurons - Under the cortex is a white matter (myelinated axons) Sulcus- clear deep crevices that define the different lobes Frontal lobe- anterior region of the cerebral cortex; decision making, planning, emotional control, personality Parental lobe- two of them; posterior to the frontal lobe and separated by the central sulcus; body awareness (touch and temperature) and ability to preform complex task Temporal lobe- on the side below the parietal lobes; process sound, memory, and understanding speech Occipital lobe- behind the parietal lobe in the back of the brain; processes visual information from the eyes Primary Motor Cortex- part of the frontal lobe, ‘command’ neurons produce complex coordinated behaviors by controlling skeletal muscle movements Primary Somatosensory Cortex- part of the parietal lobe, integrates tactile information from specific body regions and sends it to the motor cortex ** both motor and somatosensory cortices makes connections to the opposite side of the body by sending axons that cross over in the brainstem and spinal cord ▯ right cortex controls the left side of the body and vice versa Topographic Maps - Brain mapping for part of the brain -Larger the body part on map the more space dedicated with axons Other types: • Auditory cortex- by pitch • Understanding language in left temporal lobe (Wernicke’s Area) • Speaking Language in left frontal lobe (Broca’s Area) • Spatial visualization and analysis on the right side • Occipital lobe maps visual information- maintained in midbrain centers and cortex Question The primary cortical area where the sensation of touch is processed in the 1. Occipital 2. Temporal 3. Parietal 4. Frontal Correct Answer: 3 Learning and Memory Cognition- ability to process and integrate complex source of information, interpret and remember past events, solve problems, reason, and from ideas Learning- enduring, adaptive change in behavior Memory- retention of learned information How: the hippocampus transforms reinforced short-term memories into long-term memories by respectively relaying information to regions of the cerebral cortex - Learning and memory involve long or short term structural/chemical changes at the synapses - Long-term memory involves change in gene expression Synaptic Plasticity- ability to adjust synaptic connections; LTP - Repeated release of a neurotransmitters stimulates the production of new receptors and dendrites Long-term Potentiation (LTP)-induced by high frequency stimulation - Discovered in the hippocampus - Best model for how learning and memory work - Found at synapses where glutamate is - Glutamate binds to NMDA and AMPA receptors
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