Glossary of 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
-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
-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.
-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
-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
-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.
-A microtubule-organizing center (MTOC)
-microtubules grow away from these to their + ends
-Function in the production of flagella and cilia, but are not necessary for microtubule production
-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
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
-Secrete fibrous proteins such as elastin and collagen that form a molecular network that holds tissue cells in place --> extracellular matrix
Extracellular Matrix
-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)
-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
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
-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)
-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
-In the brain, outnumber neurons
-Capable of cell division
-Schwann cells and oligodendrocytes make 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)
-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
-Transfer signals from neuron to neuron. 90% of neurons in the human body are interneurons
Motor Neurons (efferent)
-Carry signals to a muscle or gland called the effector
-Located ventrally in body
Central Nervous System (CNS)
-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)
-Handles the sensory and motor functions of the nervous system
-Divided into the somatic (voluntary) and autonomic nervous systems (involuntary)
Somatic Nervous System
-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
-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
Part of ANS, which is part of PNS: "Flight or Fight"
Part of ANS, which is part of PNS: "Rest or Digest"
-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
-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)
-Consists of the cerebrum or cerebral cortex (incapable of functioning without the lower brain)
-Acts to store memories and process thoughts.
Sensory Receptors
-Distinguish between different stimuli
-Transduce physical stimulus to neural signals
-Where light first strikes (and bends) onto the eye
-Nonvascular and made of collagen
-Acts as a converging lens
-Flattening the eye by relaxing the ciliary muscles make the lens less powerful (moves focal point away from lens)
-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
-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
1) outer ear
2) middle ear
3) inner ear
-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
-Inside the inner ear.
-They are responsible for balance, and detect movement in all directions.

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