lab exam 3 Flashcards
visual signal transduction (light)
- absorption of light by rhodopsin triggers a change in retinal (from 11-cis to all-trans)
- change in retinal produces a series of reactions that close the sodium channels in rod
- calcium channels in synaptic cleft close
- no neurotransmitter released
- bipolar cell remains depolarised
- neurotransmitter released at synaptic cleft of bipolar cell
- ganglion cell depolarised
- action potential along optic nerve
Rods
- Most numerous
- Operate in dim light
- Do not discriminate color
- Many rods feed single ganglion cell (fuzzy and indistinct images)
- Rod-shaped
Cones
- Less numerous
- Operate in bright light
- Discriminate colors (red, green, blue)
- One cone feeds one ganglion cell (detailed and high resolution vision)
- Cone-shaped
Process of light being absorbed and transferring into a neural signal
- In the dark, all-trans retinal converts back to its 11-cis form
- Sodium moves into rods through ligand-gated calcium channels
- Calcium moves into rod through voltage-gated calcium channels
- Influx of calcium causes the release of neurotransmitter
- Binding of neurotransmitter to bipolar cell causes hyperpolarization
- No neurotransmitter released at synaptic cleft of bipolar cell
- No depolarization of ganglion cell
- No action potential along optic nerve
trace pathway of light from eye to retina
- through the cornea
- through our anterior chamber
- light goes through the pupil
- light passes through the lens
- moves through posterior cavity
- comes down to the retina
3 chambers of cochlea
- scala vestibuli
- scala tympani
- scala media
Structures of ear and brief functions
Pinna - protections, directs sound waves into ear
External auditory canal - produce earwax, transmission of soundwaves
Tympanic membrane - transfers and amplifies sound waves for ossicles
Ossicles (malleus, incus, stapes) - transmit vibrations from tympanic membrane to oval window
Oval window - vibrations at oval window causes movement of fluid in cochlea
Round window - allows fluid in the cochlea to move
Semicircular canals - house equilibrium receptors
Vestivule - house equilibrium receptors
Cochlea - houses organ of corti, receptor for hearing
Pathway of vibrations through the ear
- soundwaves directed into pinna
- through external acoustic meatus
- hits the tympanic membrane
- passes vibrations onto ossicles
- vibration of stapes passes on to oval window
- oval window causes movement of fluid within canals of cochlea
Static Equilibrium
Occurs when the body is motionless or moving in a straight line i.e., jumping up and down or driving on a straight road in a car
receptors for static equilibrium located in vesitbule (utricle and saccule)
Macula of utricle detect linear movement in the horizontal plane
Macula of saccule detects linear movement in the vertical plane
Dynamic equilibrium
Occurs when the body is moving in a rotational or angular direction i.e., spinning around in a circle or swinging on a swing
receptor for dynamic equilibrium located in the semicircular canals
Crista located in each of the three semicircular canals detect rotation in the three planes (transverse, sagittal and coronal)
Tastebuds or Gustatory cells
Microvilli or gustatory hairs that project taste pore
Found on tongue and soft palate
Basal cells replace old tastebuds
Structures of the olfactory system
Olfactory mucosa
- located on roof of nasal cavity
- made up of lamina propria and olfactory epithelium
Lamina propria
-contains glands which secrete mucus
Olfactory epithelium
- made up of olfactory receptors, supporting cells and basal cells
structures of nose and functions
Olfactory receptor cells - receptors for smell
Basal cells - differentiate to replaced old olfactory receptor cells
Supporting cells - provide physical support, nourishment and electrical insulation
Mucus - protects olfactory receptor cells which contain binding site for odourants
Olfactory transduction process
- odourant must be in a gaseous state and dissolved in mucus
- Odourant binds to cilia on olfactory receptor (sits within mucus)
- Binding of odourant causes g-protein mediated production of cAMP
- cAMP binds to ligand-gated sodium channels
- Sodium enters sensory neuron causing depolarisation
- Action potential generated along axon of olfactory nerve
differences between skeletal and smooth muscle contraction
skeletal is voluntary
smooth is involuntary
smooth muscles has row of varicosities
skeletal contraction occurs through binding of calcium to troponin
smooth contraction occurs through the binding of calcium to calmodulin
Compare the characteristics of the three different types of muscle
Skeletal muscle – the specialised tissue that is attached to bones and allows movement. Skeletal muscles are under our conscious control which is why they are also known as voluntary muscles
Characteristics
- Voluntary
- Striated
- Not branched
- Multinucleated
Smooth muscle – Located in various internal structures including the digestive tract, uterus, and blood vessels such as arteries. It is arranged in layered sheers that contract in waves along the length of the structure. Also known as involuntary muscle as motion of smooth muscle happens without our conscious awareness
Cardiac muscle – the muscle specific to the heart. The heart contracts and relaxes without our conscious awareness
Characteristics
- Involuntary and intrinsically controlled
- Striated
- Branched
- Single nucleated
Describe the gross and microscopic anatomy of muscle
Skeletal muscle
- Proteins are organized into sarcomeres and then bundled into myofibrils
- Myofibrils are bundled into skeletal muscle cells that are contained by a cell membrane known as the sarcolemma
- On top of the skeletal muscle cell is the endomysium. Many of these skeletal muscle cells covered by their individual endomysium are bundled into a fascicle
- The fascicle is covered with perimysium. Many fascicles are bundled together to create a whole skeletal muscle
- This skeletal muscle is then covered with epimysium
Endomysium – fine sheath of connective tissue composed of reticular fibers surrounding each individual muscle fiber
Perimysium – fibrous connective tissue that surrounds groups of muscle fibers called fascicles
Epimysium – fascicles surrounded in another sheet that surrounds the whole muscle
Muscle twitch – the brief contraction of all muscle fibers innervated by a motor unit, in response to a single action potential
Each muscle supplied with
- One nerve – innervation
- One artery – supplies O2 and nutrients
- One (+) veins – removes wastes and CO2
Each muscle fibre is a long, cylindrical cell with multiple nuclei
Sarcoplasm
- Glycosomes – contains glycolytic enzymes for glycolysis
- Myoglobin – pigment that stores O2 needed for muscle activity
Myofibrils
- Aligned repeating series of dark and light bands
- Composed of myofilaments
- Contractile elements
- Responsible for skeletal muscle fibre contraction
- Contains sarcomere – the smallest functional unit of muscle fibre, region of a myofibril between two successive Z discs
- Myofilament – proteins called actin and myosin
Myosin
- Composed of the protein myosin
- Thick filaments
- Tails – heavy polypeptide chains – interwoven
- Heads – act as cross bridges during contraction
- Binding sites for Actin and ATP
Actin
- Thin filaments
- Actin – globular subunits – G actin
- Tropomyosin – long orange band, covers the active binding sites and stiffen the actin
- Troponin – holds the tropomyosin strand in place, changes shape when calcium binds
Sarcolemma – plasma membrane of the muscle cell, an excitable membrane
Sarcoplasmic reticulum
- Runs longitudinally
- Surrounds each myofibril
- Regulates intracellular ionic Ca2+
- Stores and releases Ca2+
Terminal cisternae
- Are enlarged areas of the SR surrounding the T-Tubules
- Ensure rapid calcium delivery
Transverse tubule
- Have membranes with large concentration of ion channels, transporters and pumps
- Rapid transmission of action potential into deepest region of muscle cell
Triad
- SR, terminal cisternae (paired) and T Tubules
Describe the process of muscle contraction (from neuromuscular junction to cross bridge cycling)
For a muscle to contract
- Be stimulated by a nerve ending
- Propagate an action potential along its sarcolemma
- Have a rise in intracellular Ca2+ levels
Part 1
- Passing the message from brain to the muscle
- Linking the electrical signal to the contraction is excitation-contraction coupling
Phase 1 : Activation
- The fiber must be activated
- Must generate an action potential
Phase 2: Excitation-contraction coupling
- The AP is automatically propagated along the sarcolemma
- Intracellular calcium levels must rise briefly
Part 2
- Contracting the muscle (sarcomere)
- Cross bridge cycling
Neuromuscular junction
- Formed by axonal endings – synaptic vesicles – Ach
- Motor end plate – Ach receptors
- Synaptic cleft
Cross bridge cycling
- The active site on actin is exposed as Ca2+ binds troponin
- The myosin head forms a cross-bridge with actin
- During the power stroke, the myosin head bends and ADP and phosphate are released
- A new molecule of ATP attaches to the myosin head, causing the cross-bridge to detach
- ATP hydrolyzes to ADP and phosphate, which returns the myosin to the “cocked” position
Sliding filament theory
- Contraction – the activation of the myosin’s cross bridges
- Relaxation – cross bridges become inactive and the tension generated declines
- SFT – thin filaments slide past the thick filaments – occurs simultaneously in sarcomeres through out the cell
Understand what is required for myosin heads to detach from actin
Rest
- ATP binding causes myosin head to detach from the actin
- Troponin/tropomyosin blocks binding
- Ca2+ stored in end sacs of SR
three phases of muscle twitch
- Latent period
- Contraction period
- Relaxation period
Describe the factors that influence the force of muscle contraction
factors that increase the force of skeletal muscle contraction
- Large number of muscle fibers recruited
- Large muscle fibers
- High frequency of stimulation (wave summation and tetanus)
- Muscle and sarcomere stretched to slightly over 100% of resting length
Graded muscle responses are
- Variations in the degree of muscle contraction
- Required for proper control for skeletal movement
Responses are graded by
- Changing the frequency of stimulation
- Changing the strength of the stimulus
Stimulus intensity
- Threshold stimulus – the stimulus strength at which the first observable muscle contraction occurs
- Recruitment
Wave summation
- If stimuli delivered to a muscle in close succession the second twitch will be stronger
Muscles generate more force when stretched beyond their resting length
Multiple action potentials summate together for 1 larger contraction
Briefly describe the characteristics of the three different types of skeletal muscle fibres
Slow oxidative fibers (type 1) - have a slow speed of contraction and a high resistance to fatigue. Increased concentration of myoglobin which has an increased capacity to transport oxygen. Numerous mitochondria
Fast oxidative-glycolytic fibers - have fast contractions and primarily use aerobic respiration but because they may switch to anaerobic respiration (glycolysis) can fatigue more quickly than slow oxidative fibers
Fast glycolytic fibers - have a slow supply of oxygen and therefore very little mitochondria. contain very few myoglobin molecules. the muscle fibers have a large diameter and therefore produce large contractile force. break down ATP quickly and therefore contract quickly
Describe the different types of muscle contraction (isotonic, isometric)
Isotonic – contraction involving muscle shortening (concentric) or lengthening (eccentric)
Isometric – contraction without a change in muscle length
Define the terms agonist, antagonist, synergist, and muscle tone
Agonist – the contracting or shortening muscle
Antagonist – the relaxing or lengthening muscle
Synergist – assists the agonist muscle
Muscle tone – continuous and partial contraction of muscle
Briefly describe the three energy systems used for muscle contraction
ATP-CP
- High energy molecule stored in muscles
- Regenerates ATP
- Creatine phosphate + ADP -> creatine ATP
Anaerobic glycolysis
- When muscle contractile activity reaches 70% of maximum
- Bulging muscles compress blood vessels
- Oxygen delivery is impaired
- Glucose undergoes glycolysis liberating 2 ATP and forms pyruvic acid
- Anaerobic – 400m – up to 30-60 seconds
Aerobic
- At rest and light-moderate exercise
- 95% of all ATP produced by this process
- 36 ATP molecules are produced from fatty acids, amino acids and glycogen
- Aerobic – marathon – until fuel stores are depleted
Identify and provide a function for the accessory structures of the eye
Eyelid - provide protection, support and lubrication for the eyeball
Eyelashes - provide protection via their sensitivity causing blinking
Eyebrows - provide protection from sunlight and sweat
Lacrimal caruncle - produces tears important for lubrication and protection
Conjunctiva - provides protection and lubrication
Identify and provide a function for the structures of the eye
Posterior cavity - contains vitreous humour which maintains round shape of eye
Anterior cavity - contains aqueous humour which maintains intraocular pressure
Sclera - provides protection and acts as an anchor for extrinsic eye muscles
Choroid - contains extensive capillary network supplying retina and sclera
Retina - transmits visual information via photoreceptors
Cornea - provides a window for light to enter the eye
Iris - contains blood vessels, pigment and smooth muscle
Pupil - opening in centre of iris that regulates amount of light entering eye
ciliary body - includes ciliary muscle which holds lens in place
Leans - focusses the light that passes through it onto the retina
Macula - yellow spot in centre of retina
Fovea - contains highest concentration of cone for high resolution vision
Optic disc - where optic nerve leaves the eye (blind spot)
Describe how the lens changes with far and near vision
Accommodation - the ability of the eye to change its focus from distant to near objects (and vice versa). this is achieved by the lens changing its shape
