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BIOLOGY 252 EXAM 1 LATEST 2025 ACCURATE
SUMMER TERM EXAM GRADED A+
What is homeostasis? how varied components of living things adjust to maintain a constant internal living environment. There is a balanced dynamic state! Diseases result from homeostatic imbalances (diabetes) What are the levels of organization? chemical - cellular - tissue - organ - organ system - organismal What is the nervous system made of? The Central nervous system (brain and spinal cord) and the peripheral nervous system (cranial nerves and spinal nerves). What is the big picture of the nervous system? What does this mean? Input - Processing - Output. Explain. Most of our wiring is. insulated. Neuron
Describe the soma, neurofibrils, Nissl bodies, dendrites, axon and axon hillock. Soma- body of the neuron cell. Neurofibrils- work with microtubules to compartmentalize rough ER into Nissl bodies. Nissl bodies- help identify neurons in tissue sections with mixed cell types Dendrites- primary site for receiving signals from other neurons axon hillock- nerve fiber where axon originates axon- conducs nerve signals to remote point from the soma. contains Varicosities secrete NTs. How are neurons classified? By number of processes extending from the soma. What is the difference in multipolar nerons, bipolar neurons, and anaxonic neurons? multipolar - one axon with multiple dendrites. Includes most neurons of the brain and spinal cord. bipolar- one axon and one dendrite. Anaxonic- multiple dendrites, no axon. Communicate through dendrites and produce no action. found in brain, retina, and adrenal medulla. What is axonal transport? two way passage of proteins, organelles, and other materials along the axon. What is anterograde and retrograde transport? anterograde- moves down the axon, away from the soma. retrograde- moves up the axon, towards the soma.
A whitish, fatty segmented sheath around most LONG (not all) axons. They increase the speed of nerve impulse transmission. It is formed by cells. The cell has concentric layers of membrane that make up the myelin sheath. What are neuroglia? glia cells that protect neurons by binging them together to provide a supportive framework for nervous tissue. Prevent neurons from contacting each other. What are the four neuroglia in the central nervous system? Astrocytes, Oligodendrocytes, Ependymal cells, and Microglia Astrocytes
- support and brace neurons
- control the chemical environment
- cover the brain and nonsynaptic regions of neurons
- supportive framework of CNS
- induce BBB
- influence synaptic signaling
- secrete growth factors
- removes K+ and some NTs from ECF of brain and spinal cord
- form scar tissue Oligodendrocytes
- insulators of the thick neurons of the CNS
- form myelin in brain and spinal cord
- bulbous shape w/ arms that wrap around it forming myelin sheath
Microglia
- The "immune cells" of the CNS
- phagocytize and destroy microorganisms, foreign matter, and dead nervous tissue. Become concentrated in areas affected by infection, trauma, or stroke. and induce the formation of the BBB. Astrocytes and Pericytes Ependymal cells
- Ciliated epithelial cells lining the central cavities of the brain and spinal column.
- Forming a permeable barrier between the CSF and nervous tissue
- beating cilia helps circulate the CSF
- secrete and circulate CSF Schwann Cells Form neurilemma around the PNS nerve fibers and myelin around majority of them. Aid in regeneration of damaged nerve fibers. Satellite Cells Surround somas of neurons in the ganglia, provide electrical insulation and regulate chemical environment of neurons (homeostasis?) What is hydrocephalus?
Although there are leakage channels, the sodium permeability is so low the change will be minor. Think about a lot of students outside a small door that wants to get in, but they cannot all get through at once. •Sodium has a positive reverse potential because it has to go against the chemical gradient. What is the RMP when both NA+ and K+ are present? Will it be somewhere in between?
- 70 mv. K+ has an mv of - 80 and NA+ has an mv of +60. It is not somewhere in between because of permeability. Potassium is much more permeable than sodium and there a more leakage channels for potassium. What creates the chemical gradient in the first place? The pump restores the chemical gradients and therefore maintains the resting MP. Without the Na+/K+ pump (3 sodium 2 potassium), the ions will reach equilibrium even without an electrical gradient, but simply by diffusion through the leak channels. Only a fraction of ions are actually involved (.006% of K+). A child eats a whole bottle of salt (NaCl) tablets. What effect does this have on the resting membrane potential? Just remember... The membrane is much more permeable to potassium than to sodium. The electrical gradient counteracts the chemical gradient, and the ions reach equilibrium. Chemically (ligand) gated channels a ligand binds to receptor causing a conformational change and opening the gate to the ions.
- can be specific or not specific (Ach at neural muscular junctions is permeable to all cations - noth Na and K).
Voltage gated channels
- ion selective Gates can open and close at different speeds Mechanically gated channels found in sensory receptors Is the membrane polarized or not? Yes it is polarized. To change membrane potential you have to depolarize or hyperpolarize the cell. Depolarize Making the cell less polarized (closer to zero). Sodium channels opening leads to depolarization -- the generation of a. Graded (local) potential. A short range change in membrane potential upon a stimulus. In two separate experiments, researchers increase sodium concentrations in the ECF. In cell 1 they increase it more than they do in cell 2. They stimulate sodium ligand gated channels to open up. Will local membrane potentials in cell 1 be identical 2 cell 2? Explain. The graded potential is increased with a stronger stimulus. More sodium channels will open up in cell 1 leading to more depolarization. Cell 1 should have a greater change in graded membrane potential. Explain a graded potential spreading locally.
Action potentials can only be generated and propagated in and. Neurons (only at the axon) and muscles. Why? channels are found mainly on the axon and axon hillock (trigger zone). Voltage gated channels Sodium voltage gated channels have two gates. Describe these. At resting state:
- Na+ activation gate: closed
- Na+ inactivation gate: open
- K+ inactivation gate: closed Upon depolarization the gates change their status.
- Na+ activation gate: Opens quickly
- Na+ inactivation gate closes slowly
- K+ gate opens slowly At the peak, Na+ channels close and slower K+ channels open. Hyperpolarization causes Na activation gate to close completely and K+ to open completely Voltage gated K+ channels close and returns to normal. At what point does an action potential become an all or none process? Upon reaching the threshold
What allows action potentials to continue and not die out? Voltage gated channels !! How do action potentials move through the cell? Formation of one AP in one site generates AP in the next site and so forth (domino effect) Absolute Refractory Period Na+ channels have not yet reset to the resting positions. A new AP CANNOT be generated. (before the peak) Relative refractory period Some Na+ channels have reset to their resting position, so if the stimulus in strong enough, a new AP can be generated. (after the peak) What is another function of the myelin sheath? It provides faster propagation aka saltatory conduction "leaps." What are the spaces in between the myelin sheath? The Nodes of Ranvier. They contain the voltage gated channels, leak channels, Na+/K+ pump, etc. Where does continuous conduction occur? Along unmyelinated axons
EPSP
Excitatory Post Synaptic Potential There are channels that allow sodium ions to move in the post synaptic neuron and this causes depolarization and a graded potential = EPSP. We have a - 70 RMP. The Na+ is going to depolarize it. There is no AP in the soma so the Na+ is going to go the trigger zone. We have an EPSP but since it does not reach threshold it is not sufficient enough to generate an AP. Spatial summation When the postsynaptic neuron is stimulated by a large number of terminals at the SAME TIME If there are enough sodium ions, there will be enough depolarization to reach the threshold and cause an action potentials. It needs to be close to the axon hillock. The further it is, the higher the chance of dying out. Temporal summation Presynaptic neurons transmit impulses in RAPID FIRE ORDER. What is the stimulus for an AP? A graded potential from the dendrites and the cell body, and voltage gated channels. APs result in synaptic activity and information processing What is an IPSP? Needed for regulation. Results in hyperpolarization and makes it harder to reach the threshold. (membrane may become more permeable to K+ and Cl- ions)
Where are inhibitory synapses?
- Inhibitory synapses will be mostly found at the cell body or close to the axon hillock
- IPSPs can also summate with EPSPs, canceling each other out NT's are commonly classified as excitatory or inhibitory. Use ACh as an example. ACh is stimulatory at neuromuscular junctions (skeletal) ACh is inhibitory at neuromuscular junction of the heart effect of the neurotransmitter on the postsynaptic membrane depends on the type of receptor, The human brain Not pictured: Cerebellum (near pons and medulla) Cerebrum (top of brain) The cerebral cortex is contralateral. What does this mean? Each hemisphere is responsible for the opposite side of the body. Left hemisphere sense right inputs, etc. Decussation causes this quality. Remember no single area acts alone. Conscious behavior involves the entire cortex. What are the three types of functional areas of the cerebral cortex? Motor areas: control voluntary movement (muscles or skeleton) Sensory areas: conscious awareness of sensation
Present in one hemisphere. Post central gyrus (primary somatosensory cortex) RECEIVES information from the skin and skeletal muscle. This area processes and analyzes sensory inputs from the primary sensory cortex. Difference in primary somatosensory cortex and somatosensory association area? PSC receives info from the skin and skeletal muscles while SSAA integrates sensory info and forms and understanding of the stimulus. Determines the size, texture, and relationship of parts.
- cortex (receive)
- association (analyze) Primary auditory cortex Receives information related to pitch, rhythm, and loudness Auditory association area Stores memories of sounds and permits perception of sounds Top - visual association area (damage causes visual agnosia) allows you to identify a shape or something you see Bottom - visual cortex (blindness)
allows you to see general shapes and shadows but no identification What are these sensory centers? Gustatory cortex, visceral sensory, and olfactory Gustatory: taste Olfactory: smell Visceral sensory: sends signals from the visceral (internal organs) Multimodal association areas
- Interacting with multiple areas
- Responsible for the high order or cognitive functions ex:
- Prefrontal cortex
- Language center The prefrontal cortex Responsible for intellect, learning, and personality Associated with working (short term) memory and emotions The prefrontal cortex is connected with many other regions in the brain. What happens if we cut these connections? Short term memory and things associated with certain regions may be forgotten.
Thinking present What are basal nuclei? located in the gray matter embedded within white matter. Basal nuclei is a cluster of cell bodies that determine the onset (beginning) and cessation (ending) of intentional movements. They coordinate control of antagonistic muscle pairs and contribute to a better motor plan. The diencephalon is composed of the. Thalamus, hypothalamus, and epithalamus. The thalamus is the of the brain. Sensory relay center. What does the thalamus do?
- Sensual afferent impulses converge and synapse in the thalamus
- Impulses of similar function are sorted out, edited, and relayed as a group
- Almost all inputs ascending to the cerebral cortex pass through the thalamus (not smell) ** Neurons synapse and the thalamus. Those impulses are sorted out.. The is the visceral control center of our body. Hypothalamus.
What are the functions of the hypothalamus?
- link between endocrine and nervous system
- controls drives (thirst, hunger, sex, etc)
- regulation of body temp
- regulation of autonomic nervous system The brain stem is the.. Midbrain, pons, and medulla oblongata. Structural framework, hosting ascending and descending neural fibers Nuclei responsible for our built-in, automatic system Substantia nigra nuclei in the midbrain, releasing dopamine to the basal nuclei. Dopamine inhibits basal nuclei by generating IPSP. What will happen if the cells of the substantia nigra degrade? There would be no control of beginning and ending or antagonistic muscles. They would be overactive. Resulting in Parkinson's disease. They overwork and you can't control mucles as well sensory receptors
- structures specialized to detect a sensory stimulus.
- fundamental purpose is transduction
- most sensory signals delivered to CNS produce no conscious sensation. They are filtered out in the brainstem by the RF or some do not require conscious awareness like pH or body temp.
