PSL 250 UNIT THREE QUESTIONS WITH VERIFIED ANSWERS LATEST UPDATE 2026

PSL 250 UNIT THREE QUESTIONS WITH VERIFIED ANSWERS LATEST UPDATE 2026 Identify and describe the four functional neuron segments - Answers Receptive segment (receives information) Initial segment (axon hillock) Conductive segment (axon, myelin sheath, neural impulse) Transmissive segment (axon terminals, synaptic knobs, release neurotransmitters) Distinguish between a pump and a channel - Answers Channels: protein pores in the membrane that allows ions to move down their concentration gradient. Pumps: membrane proteins that maintain a concentration gradient by moving substances against their concentration gradient. Require ATP Identify three types of channels - Answers - Leak channels (always open) - Chemical gated channels (open when a neurotransmitter binds) - Voltage gated channels (open when membrane potential changes) Describe the three specific states of a voltage-gated Na+ channel - Answers Have two gates (inactivation gate and activation gate) Resting (closed): inactivation gate is open, activation gate is closed (-70mv) Activation (open): Inactivation gate and activation gate open (-55mv) Inactivation (closed): Inactivation gate closed, activation gate open (+30mv) List the channels and pumps that are located along the entire neuron - Answers Entire plasma membrane of neuron - Leak channels (mainly K+) - Na+/K+ Pumps - Maintain resting membrane potential List the channels and pumps that are located in the receptive segment of the neuron - Answers Receptive segment - Chemically gated ion channels (cation, K+, Cl-) List the channels and pumps that are located in the initial segment of the neuron - Answers Initial segment -Voltage gated ion channels (Na+ open first, then K+) List the channels and pumps that are located in the conductive segment of the neuron - Answers Conductive segment: - Voltage gated ion channels (Na+ goes inside, K+ goes outside) List the channels and pumps that are located in the transmissive segment of the neuron - Answers Transmissive segment: - Voltage gated calcium channels and pumps (channel lets Ca+2 in, pumps bring Ca+2 out) Briefly describe the physiological events that occur at the different segments of the neuron - Answers Receptive segment: binding of neurotransmitter released from presynaptic neurons; production of graded potentials Initial segment: Summation of graded potentials, initiation of action potential Conductive segment: propagation of action potential Transmissive segment: action potential causes release of neurotransmitter Describe the features of an excitatory post-synaptic potential and how it is generated - Answers - Neurotransmitter binds to ligand-gated ion channel -Open a non-specific ion channels, lets Na+ in and K+ out (preferential to Na+) - Moves the membrane potential closer to the threshold (depolarization) - Small in amplitude (1mv-4mv) and lasts 15ms-20ms - Referred to as graded potential and can vary in amplitude Describe the features of an inhibitory post-synaptic potential and how it is generated - Answers - Neurotransmitter binds to ligand-gated ion channel - Opens a Cl- channel; Cl- enters the cell and the cell becomes more negative - Moves the membrane potential away from the threshold (polarization) - Small in amplitude (1mv-4mv) and lasts 15ms-20ms - Referred to as graded potential and can vary in amplitude Describe the general arrangement of pre-synaptic inhibitory and excitatory neurons and how they influence the activity of the neuron - Answers Several presynaptic neurons with a postsynaptic neuron Describe how spatial and temporal stimulation occur - Answers - Spatial: Many synapses sum to bring the membrane potential to threshold - Temporal: One synapse occurs rapidly to bring the membrane potential to threshold - Any individual EPSP would not bring the membrane to potential threshold Describe what happens in the initial segment during an action potential (All or none law) - Answers - If threshold reached, action potential generated and propagated down axon without any loss in intensity - If threshold not reached, voltage-gated channels stay closed; no action potential - The axon shows the same intensity of response to values greater than threshold Describe what happens in the conductive segment during an action potential - Answers - Axon conducts action potentials - Depolarization is gain of positive charge as Na+ enters through voltage-gated Na+ channels - Depolarization is return to negative potential as K+ exits through voltage gated K+ channels -Action potential is propagated down axon to synaptic knob Describe the seven steps of an action potential - Answers 1. Membrane potential is at -70mv 2. Membrane reaches threshold (-55mv) which causes the voltage gated Na+ channels to open 3. Na+ flows into the neurons. Depolarization. Membranes potential is +30mv 4. At +30mv, the Na+ inactivation gate closes, Na+ movement stops 5. Voltage gated K+ channels open; K+ exits the cell; repolarization 6. K+ continues to exit cell; hyperpolarization 7. Voltage gated K+ channels close; Na+/K+ pumps and leak channels restore resting membrane potential Define the refractory period and explain the difference between the absolute and the relative refractory periods associated with transmitting an action potential - Answers Absolute refractory period: during depolarization and repolarization. An action potential cannot be produced Relative refractory period: during hyperpolarization. An action potential can only be produced with a strong stimulus Explain propagation of an action potential in both unmyelinated and myelinated axons - Answers Unmyelinated: - Continuous conduction - Channels and pumps not concentrated - Slow Myelinated: - Saltatory conduction - Channels and pumps are concentrated at nodes (diffusion is faster) - Fast Describe the events that occur when an action potential reaches the transmissive segment - Answers - Action potential reaches synaptic knob - Voltage gated Ca+2 channels open - Ca+2 enters the cell and binds with proteins associated with synaptic vesicles - Synaptic vesicles fuse with the synaptic knob plasma membrane and neurotransmitter is exocytosed - Neurotransmitter diffuses across synaptic cleft and attaches to receptors on a muscle or receptors of a neuron/gland Describe the general role of calcium in neurotransmitter release - Answers Ca+2 triggers fusion of the synaptic vesicle with the membrane and exocytosis of the neurotransmitter Describe how botox inhibits neurotransmission - Answers Inhibits the production and release of acetylcholine Distinguish the difference between acetylcholine acting directly and indirectly on effectors - Answers Direct -Nicotinic receptor -Acetylcholine attaches and Na+ diffuses into the neuron to cause EPSP Indirect - Muscarinic receptor - Acetylcholine attaches and a second messenger detaches to cause EPSP or IPSP Describe the relationship between action potential velocity and axon size - Answers Action potential velocity increases as axon size increases due to lower resistance Describe the anatomical features of the brain - Answers - The adult brain is about the size of a grapefruit and weighs about three pounds - Gyri (ridges) and sulci (depressions between ridges) - cerebrum is separated into two hemispheres and has five lobes (frontal, parietal, temporal, occipital, insula) Describe the relationship between brain activity and brain blood flow - Answers Increased activity in the brain results in increased flow of blood to the brain to support the increased neural activity Describe the general functions of the frontal lobe - Answers - Primary motor cortex: in pre central gyrus, voluntary motor control of skeletal muscles - Motor speech area (Broca area) - Prefrontal cortex: decision making and planning, personality, higher intellectual functioning Describe the general functions of the parietal lobe - Answers - Somatosensory cortex: post-central gyrus, cutaneous and muscular sensing - Understanding speech and formulating words to express thoughts and emotions -Interpretation of textures and shapes Describe the general functions of the temporal lobe - Answers - Interpretation of auditory sensations - Storage (memory) of auditory and some visual experiences Describe the general functions of the occipital lobe - Answers - Integration of movements in focusing the eye - Conscious perception of vision - Storing visual memory Describe the general functions of the insulates - Answers - Memory -Interpretation of taste - Sensory (mainly pain) and visceral integration Describe the composition of gray and white matter and compare the distribution of gray and white matter throughout the brain divisions - Answers Gray matter - Made of neuron cell bodies, dendrites, and unmyelinated axons - Cerebral cortex (gray matter surface of cerebrum) - Cerebral nuclei (regions of gray matter found in cerebrum) White matter - Consists of myelinated axons - inner parts of cerebrum On average, how many hours of sleep does the average adult need? - Answers 7 hours Identify the four major regions of the brain - Answers 1. Cerebrum: largest region 2. Diencephalon: deep into the cerebrum 3. Brainstem: inferior to the diencephalon 4. Cerebellum: second largest region of the brain State some important things that happen during sleep - Answers - Consolidate memory - Resynthesize glycogen - Grow muscle - Repair tissue - Synthesize hormones State some of the negative consequences of sleep deprivation - Answers - Impaired cognition - Higher levels of anxiety - Increases symptoms of depression How does brain activity vary from REM and the different stages of sleep - Answers Stages 1-4 are good for memory, synthesizing hormones, growth, repairing tissue, resynthesizing glycogen How does the amount of sleep we get change during the lifecycle? - Answers As age increases, sleep decreases Describe the anatomical features of the cerebrum - Answers - Consists of hemispheres