Biology: Lecture 4: The Eukaryotic Cell; The Nervous System
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- Receptor Mediated Endocytosis
- -Specific uptake of macromolecules such as hormones and nutrients
- Autolysis
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-Lysosomes rupture and release their contents into the cytosol killing the cell
-Useful in the formation of certain organs and tissues (EX: destruction of tissue btwn digits of a human fetus) - Smooth ER
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-Contains glucose 6-phosphatase, the enzyme used in the liver, intestinal epithelial cells, and renal tubule epithelial cells, to hydrolize glucose 6-phosphate to glucose (production of glucose from glycogen)
-Produces triglycerides
-Cholesterol formation
-Lipid formation on cytosol side of membrane
-Important for detoxing - Where do lysosomes come from?
- They bud off from the golgi.
- Peroxisomes
- -Self-replicating vesicles that inactivate toxic substances (have water as a product) and produce/breakdown H2O2
- The cytoskeleton is made up of _______ and ________.
- microtubules and microfilaments
- Microtubles
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-Larger than microfilaments
-Made from a protein called tubulin, which may polymerize into long straight filaments
-Makes up mitotic spindle, flagella and cilia - In humans, where are cilia usually found?
- In the fallopian tubes and the respiratory tract
- Axoneme
- -The major portion of each flagellum and cilium, which contains nine pairs of microtubules forming a circle around two lone microtubules (9+2 arrangement). The protein dynein makes the cross-bridges.
- Centrosome
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-A microtubule-organizing center (MTOC)
-microtubules grow away from these to their + ends - Centrioles
- -Function in the production of flagella and cilia, but are not necessary for microtubule production
- Microfilaments
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-Smaller than microtubules
-The polymerized protein actin forms a major component of these
-Squeeze the membrane together in phagocytosis and cytokinesis
-Contractile force in microvilli and muscle - Gap Junctions
- -Small tunnels connecting cells. They allow small molecules and ions to move btwn cells (EX: In cardiac muscle to provide spread of AP)
- T or F: Mitochondria have their own ribosomes
- True.
- Membrane of Mitochondria
- -Two phospholipid bilayers. The inner membrane invaginates to form cristae (electron transport chain). Btwn inner and outer membrane is the intermembrane space
- Fibroblasts
- -Secrete fibrous proteins such as elastin and collagen that form a molecular network that holds tissue cells in place --> extracellular matrix
- Extracellular Matrix
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-May provide structural support, help to determine the cell shape and motility, and affect cell growth
-Surrounds the cell and is formed by cell itself - Paracrine System
- -Local mediators are released by a variety of cells into the interstitial fluid and act on neighboring cells
- Local Mediators
- -May be proteins, other amino acid derivatives, or even fatty acids (EX: prostaglandins are fatty acid derivative local mediators that affect inflammation and smooth muscle contraction)
- Neuron
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-Functional unit of the nervous system
-Can't divide
-Almost entirely dependent on glucose for energy; uses facilitated diffusion to move glucose into cytosol from blood
-Has low stores of glycogen and oxygen, must rely on blood - T or F: The cytosol of the neuron is highly conductive
- True
- Resting Potential
- -Established by a balance between passive diffusion and Na+/K+ pump. A cell has a negative resting potential.
- Na+/K+ pump
- -Moves 3 Na+ out, 2 K+ in
- Electrical Synapses
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-Composed of gap junctions btwn cardiac muscle, visceral smooth muscle, etc.
-Transmit signals fast and in both directions - What happens if a neurotransmitter remains in the synaptic cleft?
- The cell may be stimulated over and over. To compensate, the neurotransmitter is destroyed/removed.
- Second Messenger System
- -When neurotransmitter attaches, the receptor may activate another molecule inside the cell to make changes (EX: prolonged changes like memory involve this)
- G-Proteins
- -Commonly initiate second messenger systems. Usually attached to the receptor protein. When receptor is stimulated, the a-subunit of the G-Protein breaks off and may activate: more ion channels, a second messenger (cAMP or cGMP), enzymes, or gene transcription
- T or F: The chemical synapse is the fastest step in the transfer of a nervous signal
- False: It is the slowest step
- Support Cells
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-In the brain, outnumber neurons
-Capable of cell division
-Schwann cells and oligodendrocytes make myelin - Myelin
- -Wraps around axons, increases the rate at which an axon can transmit signals (signal jumps from one node of Ranvier to the next)
- White Matter
- Myelinated axons appear white
- Gray Matter
- Neuronal cell bodies appear gray
- Sensory Neurons (afferent)
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-Receive signals from a receptor cell that interacts with its environment. It then transfers this signal to other neurons
-Located dorsally in body
-99% of sensory input is discarded by the brain - Interneurons
- -Transfer signals from neuron to neuron. 90% of neurons in the human body are interneurons
- Motor Neurons (efferent)
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-Carry signals to a muscle or gland called the effector
-Located ventrally in body - Central Nervous System (CNS)
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-Consists of the interneurons and support tissue within the brain and spinal cord
-Function is to integrate nervous signals between sensory and motor neurons - Peripheral Nervous System (PNS)
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-Handles the sensory and motor functions of the nervous system
-Divided into the somatic (voluntary) and autonomic nervous systems (involuntary) - Somatic Nervous System
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-Designed to respond to external environment (voluntary)
-Contains sensory and motor neurons, the motor neurons innervate skeletal muscle
-Synapse directly on their effectors and use ACH - Autonomic Nervous System
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-The sensory portion receives signals from organs inside ventral body cavity (involuntary)
-Innervates smooth muscle, cardiac muscle, and glands
-Motor portion subdivided into sympathetic and parasympathetic - Sympathetic
- Part of ANS, which is part of PNS: "Flight or Fight"
- Parasympathetic
- Part of ANS, which is part of PNS: "Rest or Digest"
- Acetylcholine
- -The neurotransmitter used by all preganglionic neurons in the ANS and by postganglionic neurons in the parasympathetic system
- Epinephrine/Norepinephrine in the nervous system
- -The neurotransmitter used by the postganglionic neurons of the sympathetic nervous system
- The Spinal Cord
- -Acts mainly as a conduit for nerves to reach the brain, but it controls walking reflexes, leg stiffening, and limb withdrawal from pain
- The Lower Brain
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-Consists of the medulla, hypothalamus, thalamus, cerebellum, and basal ganglia.
-Integrates subconcious activities such as the respiratory system, arterial pressure, salivation, emotions, and reaction to pain and pleasure. - The Higher Brain (cortical brain)
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-Consists of the cerebrum or cerebral cortex (incapable of functioning without the lower brain)
-Acts to store memories and process thoughts. - Sensory Receptors
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-Distinguish between different stimuli
-Transduce physical stimulus to neural signals - Cornea
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-Where light first strikes (and bends) onto the eye
-Nonvascular and made of collagen - Lens
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-Acts as a converging lens
-Flattening the eye by relaxing the ciliary muscles make the lens less powerful (moves focal point away from lens) - Retina
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-Covers the inside of the back of the eye.
-Contains light sensitive cells called rods and cones (only cones make out colors)
-Vitamin A is a precursor to all the pigments in rods and cones - Iris
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-Colored portion of the eye that creates the opening called the pupil.
-In the dark, the sympathetic nervous system contracts the iris, dilating the pupil. - The Three Parts of the Ear
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1) outer ear
2) middle ear
3) inner ear - Cochlea
- -Part of the inner ear. Allows the sound pressure to be detected by the hair cells of the organ of Corti, and transduced into neural signals.
- Semicircular Canals
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-Inside the inner ear.
-They are responsible for balance, and detect movement in all directions.