bio final Flashcards
(28 cards)
Structure of tough layers of transparent crystallin proteins that focuses light onto the retina
-Flexibility deteriorates with age
lens
Smooth muscles that stretch the lens to focus light.
-Produce Aqueous Humor
Ciliary
body
ciliary body
What are the 2 “humors” in the eye & where are they located?
Aqueous Humor: Fluid in the compartment in front of the lens that helps bend light and maintain
pressure.
Vitreous humor: Fluid filling the posterior compartment of the eye that also helps bend light and
maintain pressure.
Which tissues are affected by cataracts & glaucoma?
lens and muscle tissue
What is the difference between Myopia, Hyperopia, Astigmatism, and how is each corrected?
Myopia (Nearsightedness): Distant objects focus in front of retina, because the eye is longer than normal, cornea is too curved, or excessive amount of near-vision work.
-May be corrected with concave lenses (surface that curves inward)
Hyperopia (Farsightedness): The focal point of light from near objects is behind the retina because the eye is shorter than normal or the cornea has too little curvature.
Astigmatism: Irregularities exist in cornea or lens (ground lens)
What layer of the eye contains the blood vessels and pigment cells?
Choroid
What do the different photoreceptors detect?
Photoreceptors: The light detecting or “photosensitive” cells.
Rods: Cells very sensitive to light (allows vision in dim light).
Cones: Cells sensitive to color
What cells are involved in AMD and what happens to them?
AMD: Retina detaches and photoreceptors in the macula
degenerate, or vessels grow under the retina
Bipolar cells: Transmit action potential from photoreceptors to ganglion cells.
Ganglion cells: Neurons that form the innermost layer of the retina.
How do you say λ and what does it represent in waves?
λ( lambda) = wavelength
What are the 3 color opsins in humans?
blue green red
What wavelengths do insects see that we cannot?
Insect opsins can detect Ultraviolet wavelengths
Complex that detects dim light & consists of a transmembrane protein called Rod opsin and a
pigment retinal molecule
rhodopsin
Pigment molecule that detects light; acts like a light switch inside an opsin molecule.
11- cis retinal
Contain the photoreceptor discs.
Outer Segments of rods & cones.
Membrane-bound organelles in photoreceptors that contain light sensitive pigments
Photoreceptor discs
Precursor molecule of 11-cis retinal.
-Vitamin A deficiency can lead to night blindness and eventually blindness from hemorrhaging.
Vitamin A
Are photoreceptors depolarized or hyperpolarized in the dark?
Depolarized
order of light stimulation
- Light stimulation of rhodopsin allows GTP to bind its attached G protein (Transducin).
- G proteins (transducins) activate cGMP PDE (phosphodiesterase).
- PDE breaks down hundreds of cGMP, reducing its concentration and closing cGMP-gated Na+/Ca2+
4.Ion channels close in response to hyperpolarization. - The cell stops releasing glutamate. (Retinal Bipolar cells have a receptor that activates when glutamate is NOT present)
What are 4 muscle tissue functions?
- Many muscles resist movement
- Maintenance of posture
- Maintenance of blood pressure
- All muscles generate hea
What are the Sarcolemma, T-tubule, and Sarcoplasmic Reticulum?
Sarcolemma: Specialized muscle cell membrane.
T-tubule: Invaginations of the cell membrane in cardiac & skeletal muscle.
Sarcoplasmic Reticulum (SR): Specialized muscle cell Endoplasmic Reticulum.
What is the contractile unit of a Skeletal & Cardiac muscle?
sarcomere : which is The contractile unit of a Skeletal &
cardiac myofibril extending from one Z line to the
next
What are the 2 contractile proteins?
Myosin: Protein that forms thick filaments in muscle.
Actin: Protein that forms thin filaments in muscle.
Explain the steps of Muscle contraction using the diagram
- A motor neuron releases the neurotransmitter acetylcholine at the neuromuscular junction (NMJ).
- Acetylcholine binds receptor proteins on muscle that open Na+ channels.
- Action potential: Na+ rushes into the muscle cell depolarizing the membrane which opens a cascade
of ion channels along the muscle membrane. - Action potential passes into membrane
extensions called T-tubules (transverse tubules). - Impulse reaches the Sarcoplasmic reticulum
which opens calcium (Ca2+) channels. - Ca2+ binds Troponin, which moves Tropomyosin,
opening myosin binding sites on actin.
Troponin and Tropomyosin: Two inhibitor
proteins that surround actin filaments
preventing myosin from interacting. - Myosin heads bind actin to form cross-bridges.
-This shortens the sarcomere (i.e. muscle
contracts)
6-7
Stimulation causes contraction
Does ATP connect or release actin-myosin cross-bridges?
release
