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130 Cards in this Set
- Front
- Back
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Electromagnetic receptors
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Respond to electrical, magnetic, and light stimuli - light detecting stimuli are the most common and diverse
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While animals have evolved different light sensing organs, all rely on the same _________________ to convert light energy into a nervous signal
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Light-sensitive photopigment
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This shared light-sensitive photopigment suggests...
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A common evolutionary origin that diverged during the Cambrian period
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Opsin
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Converts the energy of light photons into electrical signals in the receptor cell - photosensitive protein, common to all eyes and light-sensitive organs
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Pax6
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Regulates eye development in fruit flies, flatworms, and mice - transcription factor
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Rhodopsin
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Specific transmembrane protein found in the photosensitive cells of vertebrates - covalently bound to retinal, made of opsin
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Resting membrane potential of opsin molecules
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-35 mV
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How hyperpolarization occurs in opsin
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Opsin absorbs a light photon and undergoes a conformational change from a cis to trans configuration - Na+ channels close - decrease in firing rate indicates information about the stimulus
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Eyecups
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Used by flatworms, detect direction and intesity of light so flatworm can move away
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Image-forming eyes
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Compound eyes and single-lens eyes
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Ommatidia
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Individual light-focusing elements in compound eyes - number of ommatidia determines the resolution of the image
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Advantage of compound eyes
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They are good at detecting motion and rapid flashes of light; some even detect UV light
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Advantages of single lens eyes
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Can focus light rays on a particular region of photoreceptors, improving both image quality and light sensitivity
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Sclera
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Tough white outer layer of the eye
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Cornea
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Portion of the sclera in front of the eye, it is transparent so light may pass through
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Pupil
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Opening through which light enters the eye and then passes through a convex lens
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Iris
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Opens and closes to adjust the amount of light that enters the pupil
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Aqueous humor
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Clear, watery liquid in the interior region in front of the lens - continuously drained by small ducts at the base of the eye
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Disease that results if the aqueous humor is not sufficiently drained
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Glaucoma
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Vitreous humor
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Gel-like substance in the cavity behind the lens - makes up most of the eye's volume
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Retina
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Where incoming light is focused by the cornea and lens - contains photoreceptors and other nerve cells that sense and process the light stimuli
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How light is focused onto the retina
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The ciliary muscles contract to round the lens and bend the light rays more when focusing on an object nearby ; the ciliary muscles relax when looking at an object far away
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Advantages of 2 eyes
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Binocular depth cues, wider field of vision
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Cone cells
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Have color sensitive pigments
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Rod cells
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Sensitive to light but not color - more rod cells than cone cells
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Together, rod and cone cells are _____% of all sensory receptor cells in the human body
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70
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Fovea
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Area of the retina where cone cells are most concentrated
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Bipolar cells
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Cells onto which rods and cones synapse
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Ganglion cells
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Cells onto which bipolar cells synapse
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Optic nerve
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Where ganglion cells transmit action potentials, leads to the visual cortex
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Horizontal cells
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Communicate between neighboring pairs of photoreceptors and bipolar cells to enhance contrasts through lateral inhibition
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Amacrine cells
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Communicate between neighboring bipolar cells and ganglion cells to enhance motion detection and adjust for changes in illumination
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Hindbrain and midbrain functions
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Control basic body functions and behaviors
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Cerebral cortex
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Governs more advanced cognitive functions
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Hindbrain develops into the...
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Cerebellum and a portion of the brainstem (rest develops from the midbrain)
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Cerebellum functions
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Coordinates complex motor tasks
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Brainstem is made up of...
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Medulla, pons, and midbrain - basic functions controlled by
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Thalamus
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Relay station for sensory information
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Hypothalamus
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Physiological state controlled - interacts with endocrine and autonomic systems
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Limbic system
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Controls physiological drives, instincts, emotions, and motivation
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Hippocampus
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Long term memory formation
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Gray matter
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Cortex - made up of densely packed neuron cell bodies and their dendrites
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White matter
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Deep inside the cortex - contains axons of cortical neurons - fatty myelin
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Sulci
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Deep crevices of the brain
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Frontal lobe functions
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Decision making and planning
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Parietal lobes
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Body awareness and ability to perform complex tasks
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Temporal lobes
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Involved in processing sound, language, reading center, object identification, naming
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Occipital lobe
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Involved in processing visual information from the eyes
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Primary somatosensory cortex
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Integrates tactile information from specific body regions and relays information to the motor cortex
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Primary motor cortex
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Produces complex coordinated behaviors, controlling skeletal muscle movements
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Larger area of cortex correlates with
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Fine motor movements
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Muscles cells are also called...
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Muscle fibers
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Striated muscles
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Striped under a light microscope, includes skeletal muscles and cardiac muscles
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Muscle proteins
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Actin and myosin - used to contract and generate force, organized into filaments
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Skeletal muscle fiber characteristics
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Each is elongated and multinucleated, contains several long rod-like structures called myofibrils that contain parallel arrays of the actin and myosin filaments that cause muscle contraction
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Thick filament
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Myosin molecules arranged in parallel
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Thin filament
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Two actin filaments helically arranged
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Tropomyosin
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Runs in the grooves of actin helices
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Z discs
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Protein backbones to which thin filaments are attached
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Sarcomere
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Region from one Z disc to another - shortening of thousands of sarcomeres leads to muscle shortening
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Titin
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Links the myosin filaments to the Z discs at the ends of the sarcomere
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Sliding filament model of muscle contraction
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Muscles produce force and change their length by the sliding of actin filaments relative to myosin filaments
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Sarcomere length
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Vertebrates: 2.3 micrometers
Invertebrates: Varies but can be as short as 1.3 micrometers |
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Cross bridge cycle
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1. Myosin head binds ATP, allowing the myosin to detach from actin
2. Myosin hydrolyzes ATP to ADP and Pi - results in conformational change where myosin head is cocked back, ADP and Pi are held, keeping myosin head in a high energy state 3. Myosin head binds actin, forming a cross bridge 4. Release of ADP and Pi - power stroke in which myosin head pivots forward and generates force causing the myosin and actin filaments to slide relative to each other - actin filaments are pulled toward the sarcomere midline |
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Myosin molecules with higher rates of ATP hydrolysis results in...
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Faster muscle contractions
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What makes muscle fibers contract?
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They are electrically excitable - when action potentials arrive at the neuromuscular junction, acetylcholine is released into the synaptic cleft, ac binds to receptors at the motor endplate, triggering Na+ channel opening - leads to a change in troponin's configuration which moves tropomyosin from myosin so that cross bridge cycle may occur
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Pathway of depolarizaton
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Motor endplate -> sarcoplasmic reticulum through the T-tubule system -> SR releases Ca 2+ ions that reach troponin and cause the conformational change
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Excitation-contraction coupling
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Muscle cell excitation is coupled with muscle contraction
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How are smooth muscles activated and relaxed?
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By the binding of calmodulin with Ca 2+ released from the SR or through the cell's membrane - activates enzyme myosin-kinase which phosphorylates smooth muscle myosin heads - cross bridge cycle begins
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SR of smooth muscle cells difference
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Fewer calcium pumps so calcium is more slowly returned to the SR - longer periods of contraction
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Force that a muscle produces depends on
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Contraction length and speed of contraction
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Why intermediate action-myosin overlap is good
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Too much overlap results in myosin filaments running into Z discs, too little overlap results in little muscle contraction
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Isometric force
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Muscle is contracting, but not shortening
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Lengthening contraction
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When muscles are stretched when external load against which they contract exceeds their force output
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Most force in
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Lengthening contraction
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Antagonist muscles
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Pull in opposite directions
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Agonists
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Muscles that combine to produce similar motions - 3 heads of the triceps
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Force exerted by a muscle depends on...
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Frequency of stimulation by the motor nerve - more frequent results in increased calcium released for cross bridge formation
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Twitch contraction
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Caused by a single action potential
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Tetanus
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Muscles contraction of sustained force - high stimulation frequency
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Motor unit
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Motor neuron and the population of muscle fibers it innervates
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Slow twitch fibers
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Red, control posture and slow movements - obtain energy through oxidative phosphorylation
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Fast-twitch fibers
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White, generate force quickly - obtain energy through glycolysis
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What gives slow twitch muscles their red appearance?
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The presence of myoglobin which facilitates oxygen delivery to the mitochondria
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Which fibers are responsible for endurance?
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Slow twitch, oxidative fibers
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Hydrostatic skeleton
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Evolved early in multicellular animals - fluid contained within a body cavity serves as the supportive component of the skeleton
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2 sets of muscles involved in hydrostatic skeleton
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Circular (change diameter) and longitudinal (change length)
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Hydrostatic skeletons are well adapted for which uses?
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Jet-propelled locomotion, octopus tentacles, elephant's control over its trunk, tongues
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Hydrostatic elements in vertebrates
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Intervertebral discs - sandwiched between vertebrae all have a wall with connective tissue surrounding jelly-like fluid - allow backbone to twist and bend, cartilage - fluid filled tissue that forms joint surfaces
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When did endoskeletons evolve?
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Cambrian explosion, 500 mya
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Tendons
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Attach muscle to bone, transmit muscle forces
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Axial and appendicular regions
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Axial: skull, ribs, vertebrae - came first evolutionarily
Appendicular: Limb bones, including shoulder and pelvis |
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Skeletal tissues primarily comprised of...
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Extensive cellular matrix secreted by specialized cells - bone, tooth enamel, cartilage
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Osteoblasts
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Bone tissue forming cells, synthesize and secrete calcium phosphate and hydroxapatite mineral crystals in close association with collagen
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Composition of bone
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2/3 hydroapatite mineral, 1/3 type I collagen protein
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Articular cartilage composition
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70% water, 15% type II collagen, 15% other, usually lasts an individual's lifetime
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Endochondral ossification
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Undergone by most bones besides the skull - initially, the future bone is formed from cartilage by chondroblasts, bone starts to form where blood vessels penetrate, new cartilage continues to be added at the growth plate causing the bone to grow in length
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Compact bone
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Forms the walls of the bone's shaft
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Osteocytes
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Bone cells of dense mineralized bone tissue - comprises compact bone
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Spongy bone
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Has small plates and rods called trabeculae, with spaces in between them - found at ends of limb bones
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Bone marrow
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Fatty tissue between trabeculae, contains blood forming cells, stem cells, immune system cells
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Growth plate
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Adds new cartilage to the bone's diaphysis, at maturity, growth plate fuses as bone
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Osteoclasts
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Remove bone from marrow cavity
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Great advantage of endoskeletons over exoskeletons
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Can be repaired by osteoclasts and osteoblasts
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Torque =
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F x r (Force x axis of rotation)
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Tradeoff between...
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Force and velocity
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Hormones
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Chemical signals released into the bloodstream and circulate through the body
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Pituitary gland
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Located beneath the brain - produces growth hormone - tumors result in gigantism or dwarfism
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How are bloog glucose and calcium levels kept within a certain range?
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Negative feedback loop of hormones
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Loop that occurs when BGL is high
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Beta cells of the pancreas secrete insulin, which circulates in the blood, in response to insulin muscle and liver cells take up glucose from the blood and convert it to a storage from called glycogen
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Loop that occurs when BGL is low
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Alpha cells secrete glucagon which stimulates breakdown of glycogen into glucose and its release from muscle and liver cells
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Oxytocin feedback loop
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In response to uterine contractions, oxytocin is released from the pituitary gland, the oxytocin stimulates uterine muscles to contract even more forcefully and frequently - positive feedback loop
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3 main classes of hormones
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1. Peptide hormones - hydrophilic
2. Amine hormones - hydrophilic 3. Steroid hormones - hydrophobic |
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Peptide vs. amine hormones
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Both are derived from amino acids, peptide hormones are short chains of amino acids while amine hormones are derived from a single aromatic amino acid
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Can steroid hormones evolve?
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Not themselves, but their receptors may change along with the responses they trigger
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Peptide hormone examples
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Growth hormone, insulin, glucagon, gastrin, cholecystokin
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Amine hormone examples
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Epinephrine and norepinephrine
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Steroid hormone examples
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Sex hormones - estrogen, progesterone, testosterone, cortisol (mediates stress responses, inflammation control)
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Endocrine axes
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Hormonal signaling pathways between endocrine glands and tissues
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Releasing factors
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Peptide hormones that are initially released by the hypothalamus that signal to the anterior pituitary gland to release more associated hormones
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Many peptides originally found to act as hormones have also been found to act as...
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Neurotransmitters - oxytocin
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Pathway of sensory signals to endocrine system
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Signals processed in the brain -> transmitted to endocrine system, mainly hypothalamus -> pituitary gland -> target tissue cells in the body
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Anterior pituitary gland communication
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Neurosecretory cells communicate with the anterior pituitary gland by secreting releasing factors that travel to the anterior pituitary causing it to release hormones
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Posterior pituitary gland communication
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Contains axons of neurosecretory cells whose cell bodies are at the hypothalamus, axons release hormones directly into the bloodstream
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Anterior pituitary hormones
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Thyroid stimulating hormone, follicle stimulating hormone (FSH), luteinizing hormone (LH), adrenocorticotropic hormone (ACTH)
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Posterior pituitary hormones
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Oxytocin, antidiuretic hormone
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Tropic hormones
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Hormones that control the release of other hormones
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Parathyroid gland
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Secretes PTH - bone cell regulation
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Pineal gland
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Secretes melatonin - affects the wakefulness of the animal
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Adrenal medulla
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Secretes epinephrine and norepinephrine - fight or flight response
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