Study Guide for Physiology PDF

**[Chapter 1]** 1. Define physiology. Study of the normal functioning of a living organism and its component parts 2. List the levels of organization from atoms through organism. Atoms → Molecules → Cells → Tissues → Organs → Organ Systems → Organism 3. Define homeostasis. Wh...

**[Chapter 1]** 1. Define physiology. Study of the normal functioning of a living organism and its component parts 2. List the levels of organization from atoms through organism. Atoms → Molecules → Cells → Tissues → Organs → Organ Systems → Organism 3. Define homeostasis. What happens when homeostasis fails? The maintenance of a relatively stable internal environment despite changes in the internal and/or external environment; disease & sickness occur when homeostasis is disturbed for prolonged periods; homeostasis is a dynamic steady state, not equilibrium 4. Compare negative feedback, positive feedback, and feedforward control. Give an example of each. Negative feedback: A process that reverses a change to bring a system back to its set point. Helps maintain homeostasis **[Chapter 5]** 1. Explain how the body can be in osmotic equilibrium but electrical and chemical disequilibrium. 2. Create a map to compare simple diffusion, protein-mediated transport, and vesicular transport across membranes. A diagram of a protein medicated - **Simple Diffusion**: - Mechanism: Passive; molecules move down their concentration gradient. - Example: Oxygen and carbon dioxide crossing the lipid bilayer. - No energy or proteins required. - **Protein-Mediated Transport**: can be active or passive - Includes facilitated diffusion, active transport, and ion channels. - Facilitated Diffusion: Passive; uses carrier proteins (e.g., glucose transporters). - Active Transport: Requires energy (ATP); moves molecules against their gradient (e.g., Na⁺/K⁺ pump); can be direct (primary) or indirect (secondary) - Channels: Allow specific ions to pass (e.g., voltage-gated Na⁺ channels). Passive due to electrochemical gradient, not ATP - **Vesicular Transport**: - Mechanism: Active; involves vesicles. - Types: Exocytosis (e.g., neurotransmitter release), endocytosis (e.g., LDL uptake), and phagocytosis. - Energy required for vesicle formation and movement. 3. Compare movement through channels to movement on facilitated diffusion and active transport carriers. a. Passive movement of ions or water. b. Selectivity based on size and charge. c. Fast, allowing many ions to pass simultaneously. d. Passive; binds specific molecules. e. Slower than channels; undergoes conformational changes for each molecule. f. Example: GLUT transporters. g. Requires ATP or another energy source h. Moves molecules against their gradient. i. Example: Na⁺/K⁺ ATPase pump. (3 Na+ out, 2 K+ in)  A diagram of a transport carrier Description automatically generated 4. Apply the principles of specificity, competition, and saturation to carrier-mediated transport. 5. Explain how changes in ion permeability change membrane potential, giving examples. - **Membrane Potential**: Determined by the permeability of ions and their concentration gradients; potential difference = difference between ICF and ECF - **Increased Na⁺ Permeability**: Depolarizes the membrane (e.g., during the action potential's rising phase). Cell becomes more positive as Na+ rushes in - **Increased K⁺ Permeability**: Repolarizes the membrane (e.g., during the action potential's falling phase). Cell becomes more negative (K+ rushes OUT of the cell) - **Decreased Cl⁻ Permeability**: May depolarize the membrane if chloride\'s equilibrium potential is more negative than the resting potential. (Cl- rushing in would hyperpolarize, so decreased permeability would promote more positive inside the cell)  A diagram of a cell membrane Description automatically generatedATP closes K channel leading to depolarization; Ca2+ open; Ca2+ signal = insulin secretion **[Chapter 6]** 1. Describe three forms of local communication and two forms of long-distance communication. **The distinction between local and long-distance is a concept people seem to be forgetting as the semester goes on.** - **Local Communication**: 1. **Gap Junctions**: Direct cytoplasmic connections between adjacent cells that allow ions and small molecules to pass (e.g., cardiac muscle cells). 2. **Contact dependent signals:** require cell-to-cell contact; cell adhesion molecules (CAMs) 3. **Diffusing chemicals:** - Paracrine Signaling: Chemical signals released by a cell affect nearby cells (e.g., histamine during inflammation). - Autocrine Signaling: A cell releases a chemical that acts on itself (e.g., immune cells releasing interleukins). - **Long-Distance Communication**: 4. **Blood Transport** - **Endocrine System**: Hormones released into the bloodstream act on distant targets (e.g., insulin regulating glucose levels). 5. **Neurochemicals** - Neurotransmitters: released by neuron into synaptic cleft - Neuromodulators: modulate other neurons - Neurohormones: neuron releases hormone into blood  A diagram of a cell Description automatically generated 2. Explain the general sequence of events that follow lipophilic ligand binding to intracellular receptors. Slower response related to changes in gene activity 3. Describe the general sequence of events that follow lipophobic ligand binding to a cell surface receptor. Rapid cellular response  4. Name and describe four major groups of cell surface receptors. 5. Apply the concepts of specificity, competition, affinity, and saturation to receptors and their ligands. Note: receptor type depends on location - **Alpha receptors**: bind epi; found in intestinal blood vessels and cause vasoconstriction - **Beta receptors**: bind epi; found in skeletal muscle of blood vessels and cause vasodilation 6. List the seven steps of a reflex control pathway in the order in which they occur. 7. Compare the speed, specificity, types of signals, and duration of action in neural and endocrine reflexes. How is stimulus intensity coded in each type of reflex? - **Neural Reflexes**: - **Speed**: Very fast (milliseconds). - **Specificity**: Highly specific; targets specific cells. - **Signals**: Electrical (along neurons) and chemical (neurotransmitters). - **Duration**: Short-lived. - **Stimulus Intensity Coding**: Frequency of action potentials (increased) - **Endocrine Reflexes**: - **Speed**: Slower (minutes to hours). - **Specificity**: Broad; hormones affect all cells with appropriate receptors. - **Signals**: Chemical (hormones in the bloodstream). - **Duration**: Longer-lasting. - **Stimulus Intensity Coding**: Hormone concentration (increased) NOTE: these are mediated by the nervous system OR endocrine, NOT both; neuroendocrine is complex and is mediated by both A diagram of a brain process Description automatically generated  **[Chapter 7]** 1. Explain the four criteria that make a chemical signal a hormone. Chemicals secreted by a cell into the blood for transport to a distant target where, at very low concentrations, it affects growth, development, homeostasis, or metabolism 2. Compare endocrine cells' synthesis, storage, and release of peptide and steroid hormones. A diagram of a structure Description automatically generated - **Peptide Hormones**: - **Synthesis**: Made in advance as preprohormones; cleaved to active hormones. - **Storage**: Stored in secretory vesicles. - **Release**: Released by exocytosis when triggered (e.g., insulin). - **Steroid Hormones**: - **Synthesis**: Synthesized on demand from cholesterol. - **Storage**: Not stored; diffuse out of the cell immediately after synthesis. - **Release**: Diffuse through the cell membrane (e.g., cortisol). 3. Compare the location of hormone receptors and the cellular mechanisms of action of peptide and steroid hormones.  A diagram of a cell membrane Description automatically generated - **Peptide Hormones**: - **Receptors**: Located on the cell surface. - **Mechanism**: Activate second messenger pathways, leading to rapid responses (e.g., insulin). - **Steroid Hormones**: - **Receptors**: Located in the cytoplasm or nucleus. - **Mechanism**: Regulate gene expression, leading to slower but longer-lasting effects (e.g., testosterone). 4. Compare the three main groups of amine hormones. (**Amino-acid derived**) a. **Catecholamines**: i. Derived from single tyrosine. ii. Act like peptide hormones (e.g., epinephrine, norepinephrine). b. **Thyroid Hormones**: iii. Derived from two tyrosine molecules. iv. Act like steroid hormones (e.g., thyroxine \[T4\], triiodothyronine \[T3\]). c. **Melatonin**: v. Derived from tryptophan. vi. Regulates circadian rhythms. 5. Describe the role of the nervous system in endocrine reflexes. **(\*\*\*WEAK**) The nervous system integrates with the endocrine system through neurohormones and control pathways: - **Hypothalamus**: Produces neurohormones that regulate the pituitary gland. - **Neuroendocrine Reflexes**: Electrical signals trigger hormone release (e.g., oxytocin during childbirth). - **Feedback Loops**: Coordinates hormonal and neural responses for homeostasis. 6. List \[full spellings and abbreviations\] the six anterior pituitary hormones, the hormones that control their release, and their primary targets.  A screenshot of a medical form Description automatically generated \*\*\* These 6 are all peptide hormones 1. **Prolactin (PRL)**: - **Control**: Prolactin-releasing factors and dopamine. - **Target**: Mammary glands. 2. **Thyroid-Stimulating Hormone (TSH)**: - **Control**: Thyrotropin-releasing hormone (TRH). - **Target**: Thyroid gland. 3. **Adrenocorticotropic Hormone (ACTH)**: - **Control**: Corticotropin-releasing hormone (CRH). - **Target**: Adrenal cortex. 4. **Growth Hormone (GH)**: - **Control**: Growth hormone-releasing hormone (GHRH) and somatostatin. - **Target**: Liver and other tissues. 5. **Follicle-Stimulating Hormone (FSH)**: - **Control**: Gonadotropin-releasing hormone (GnRH). - **Target**: Gonads. 6. **Luteinizing Hormone (LH)**: - **Control**: Gonadotropin-releasing hormone (GnRH). - **Target**: Gonads. 7. Compare long-loop negative feedback for anterior pituitary hormones to the negative feedback loops for insulin and parathyroid hormone.  - **Long-Loop Negative Feedback**: - Hormones from target endocrine glands (e.g., cortisol) inhibit the anterior pituitary and hypothalamus. - **Insulin Feedback**: - High blood glucose stimulates insulin release, which lowers blood glucose, reducing the stimulus. - **Parathyroid Hormone Feedback**: - Low calcium levels stimulate parathyroid hormone release, which increases calcium, reducing further hormone release. - Long-loop negative feedback - Peripheral endocrine gland produces hormone that suppresses secretion of anterior pituitary and hypothalamic trophic hormones - Most dominant feedback mechanism - Short-loop negative feedback - Pituitary hormone suppresses hypothalamic trophic hormone production - Secondary feedback mechanism - Ultra-short-loop negative feedback (not depicted in figure above) - Occurs in hypothalamus and pituitary - Autocrine or paracrine signals to regulate secretion 8. Explain permissiveness, synergism, and functional antagonism as they apply to hormones. 9. Name the three most common types of endocrine pathologies. - **Hypersecretion**: Excess hormone production (e.g., hyperthyroidism); produces exaggerated effect - **Hyposecretion**: Deficient hormone production (e.g., hypothyroidism); absence of negative feedback leads to overproduction of trophic hormones - **Abnormal Target Response (Receptor/second messenger problems)** : Target cells fail to respond appropriately (e.g., type 2 diabetes). 10. Explain how negative feedback can be used to determine the location of a problem with one gland in a two- or three-gland pathway. (\*\*\* **NOT SURE)** Think above answers this as well **[Chapter 8]** 1. Map the organization of the nervous system in detail. A diagram of a human brain Description automatically generated - **Central Nervous System (CNS):** Brain and spinal cord; processes information and coordinates activity. - **Peripheral Nervous System (PNS):** - **Afferent Division:** Sensory input from receptors to the CNS. - **Efferent Division:** Motor output from the CNS to effectors, further divided into: - **Somatic Nervous System (SNS):** Controls voluntary movements (skeletal muscles). \*\*\* Usually voluntary, but not always - **Autonomic Nervous System (ANS):** Controls involuntary activities (smooth muscle, cardiac muscle, glands), divided into: - **Sympathetic Division:** \"Fight or flight\" response. - **Parasympathetic Division:** \"Rest and digest\" response. - **Enteric Nervous System (ENS):** Network of neurons in the gastrointestinal tract. 2. Name the types and functions of glial cells.  - **In the CNS:** - **Astrocytes:** Maintain the blood-brain barrier, provide structural support, and regulate ion and neurotransmitter concentrations. - **Oligodendrocytes:** Myelinate CNS axons to increase signal transmission speed. - **Microglia:** Act as immune cells; remove debris and pathogens. - **Ependymal Cells:** One source of neural stem cells - **In the PNS:** - **Schwann Cells:** Myelinate PNS axons and aid in repair after injury. - **Satellite Cells:** Surround neuronal cell bodies in ganglia, providing support and nutrient exchange. 3. Compare and contrast graded potentials and action potentials.  A diagram of potential Description automatically generated 4. Explain the changes in ion permeability and ion flow that take place during an action potential. (Must know specifics with activation and inactivation gates)  A diagram of a voltage gated number Description automatically generated 5. Describe and compare absolute and relative refractory periods.  - **Absolute Refractory Period:** - No new action potential can be initiated. - Na⁺ channels are inactivated, preventing depolarization. - **Relative Refractory Period:** - A new action potential can occur with a stronger-than-normal stimulus. - Some Na⁺ channels are reset, but K⁺ channels remain open. 6. Describe the role of the following in synaptic communication: ionotropic and metabotropic receptors, neurotransmitters and neuromodulators, fast and slow synaptic potentials, excitatory and inhibitory postsynaptic potentials. A diagram of a cell membrane Description automatically generated  A diagram of synapse and neuronal neurons Description automatically generated 7. Explain the mechanism of long-term potentiation mediated by AMPA and NMDA receptors.  - **LTP Process:** - **Initial Signal:** Glutamate is the key, it binds to AMPA and NMDA receptors. - **AMPA Activation:** Na⁺ influx through AMPA receptors causes depolarization. - **NMDA Activation:** Depolarization removes Mg²⁺ block from NMDA receptors, allowing Ca²⁺ influx. - **Calcium Role:** Ca²⁺ activates intracellular signaling pathways, leading to: - Activation of second messenger pathways - Paracrine release from postsynaptic cell which enhances glutamate release - **Result:** Enhanced synaptic transmission, a cellular basis for learning and memory. **[Chapter 9]** 1. Explain the formation, distribution, and functions of cerebrospinal fluid. - **Formation:** - Produced by the **choroid plexus** in the ventricles (mainly lateral ventricles). - Formed via selective filtration of plasma through ependymal cells. - **Distribution:** - Flows from the lateral ventricles → third ventricle → cerebral aqueduct → fourth ventricle. - Enters the subarachnoid space via the **median and lateral apertures**. - Circulates around the brain and spinal cord; between arachnoid membrane and pia mater - Reabsorbed into venous circulation through the **arachnoid villi** in the dural sinuses. - **Functions: chemical and physical protection** 2. Describe the structure and functions of the blood-brain barrier. - **Structure:** - **Endothelial cells of capillaries:** Joined by tight junctions to limit permeability. - **Astrocytic end-feet:** Astrocytes surround capillaries and support the barrier. - **Basement membrane:** Provides structural support to the barrier. - **Functions:** \*\*\* Protects the brain from toxic water-soluble compounds and pathogens; Small lipid soluble molecules cross the blood-brain barrier 3. Name the major subdivisions of the cerebrum, cerebellum, diencephalon, and brain stem. Explain their anatomical relationships, and give their major functions. a. **Subdivisions:** Two hemispheres connected by corpus callosum b. **Functions:** Higher functions like sensory processing, motor control, language, memory, and decision-making. c. Grey matter (outside) and white matter (inside) d. Grey Matter: i. Cerebral cortex ii. Basal ganglia: controls movement iii. Limbic system: link between cognitive functions and emotions 1. Amygdala: emotion and memory 2. Hippocampus: learning and memory e. **Subdivisions:** Two hemispheres f. **Functions:** Coordination of voluntary movements, posture, balance, and motor learning. g. **Subdivisions:** Thalamus, hypothalamus, pituitary gland, pineal gland h. **Anatomical Relationships:** Located between the cerebrum and brainstem. i. **Functions:** iv. **Thalamus:** Relay center for sensory and motor signals. v. **Hypothalamus:** Regulates homeostasis (temperature, hunger, endocrine functions). vi. **Pituitary gland:** Hormone secretion vii. **Pineal gland:** Melatonin secretion j. **Subdivisions:** Midbrain, pons, medulla oblongata. k. **Functions:** viii. **Midbrain:** Visual and auditory reflexes. ix. **Pons:** Relays information between the cerebrum and cerebellum; regulates respiration. x. **Medulla Oblongata:** Controls autonomic (involuntary) functions like heartbeat and breathing. 4. Name the four lobes of the cerebral cortex, and explain which sensory, motor, or association areas are associated with each lobe. A diagram of a brain Description automatically generated - **Frontal Lobe:** motor cortex, association area - **Primary Motor Cortex:** Controls voluntary movements. - **Broca's Area:** Speech production (left hemisphere). - **Association Areas:** Planning, decision-making, personality, and reasoning. - **Parietal Lobe:** sensory cortex, association area - **Primary Somatosensory Cortex (postcentral gyrus):** Processes tactile information (touch, pressure, pain, temperature). - **Association Areas:** Spatial awareness, integration of sensory input. - **Occipital Lobe:** sensory cortex, association area - **Primary Visual Cortex:** Processes visual information. - **Visual Association Areas:** Interprets visual stimuli (recognition of objects, colors). - **Temporal Lobe:** sensory cortex, association area - **Primary Auditory Cortex:** Processes sound. - **Wernicke's Area:** Language comprehension (left hemisphere). - **Association Areas:** Memory (hippocampus), emotion, facial recognition. Sensory areas Motor areas Association areas **[Chapter 10]** 1. Explain how receptors convert physical stimuli into electrical signals using the following terms: transduction, threshold, adequate stimulus, receptive field, receptor potential. a. The process by which sensory receptors convert a physical stimulus (e.g., light, pressure, temperature) into an electrical signal. b. This involves opening or closing ion channels, leading to changes in membrane potential. c. The minimum stimulus strength required to generate a detectable response in a receptor. d. If the stimulus doesn't reach the threshold, no action potential will be initiated. e. The specific physical area where a stimulus activates a sensory neuron. f. Smaller receptive fields result in greater sensory acuity. g. A graded potential produced in the sensory receptor in response to a stimulus. h. If the receptor potential reaches threshold, it triggers action potentials in the sensory neuron.  2. Explain how the central nervous system is able to determine modality, location, intensity, and duration of a stimulus. i. Which sensory neurons are activated and where neurons terminate in brain j. Which receptive fields are activated k. Lateral inhibition and population coding l. Number of receptors activated and frequency coding m. Stronger stimuli recruit more sensory neurons. a. Determined by how long action potentials continue to be generated in response to a stimulus. b. Receptor adaptation can alter the perception of duration. A diagram of a structure Description automatically generated  3. Explain how tonic and phasic receptors adapt to a continuous stimulus. n. Slowly adapting receptors that continue to generate action potentials as long as the stimulus is present. o. Example: Pain receptors, which help in the continuous perception of injury. p. Rapidly adapting receptors that respond only at the beginning (onset) and end of a stimulus. q. Example: Receptors that detect changes in pressure, like wearing a watch. A diagram of a normal pulse Description automatically generated with medium confidence 4. Explain how pain and itch are mediated by nociceptors. - **Nociceptors:** - Specialized sensory neurons that detect harmful stimuli. - Stimulated by mechanical, thermal, or chemical signals that indicate tissue damage. - NOT found in CNS - **Pain:** - Transmitted via two main types of fibers: - Fast, sharp, localized pain. - Slow, dull, burning, or aching pain. - Neurotransmitters like substance P and glutamate relay pain signals in the spinal cord. - **Itch:** - Mediated by skin nociceptors - Often triggered by histamine released during inflammation or by certain chemicals. **[Chapter 11]** 1. Describe the ~~structure and~~ secretions of the adrenal medulla. **People have been confusing epinephrine from the adrenal medulla with norepinephrine from sympathetic neurons.**  - **Structure:** - The adrenal medulla is the **inner region** of the adrenal glands, located atop each kidney. - It is composed of **chromaffin cells**, which are modified postganglionic sympathetic neurons. - The adrenal medulla is part of the **sympathetic division** of the autonomic nervous system. - **Secretions:** - **Epinephrine (90%):** The primary hormone secreted by chromaffin cells in response to stress (fight-or-flight). - **Norepinephrine (10%):** Also secreted but in smaller amounts. - Both hormones are released directly into the bloodstream, acting as neurohormones. - **Key Distinction:** - Epinephrine (adrenal medulla): Hormone; systemic effects via blood circulation. - Norepinephrine (sympathetic neurons): Neurotransmitter; acts locally at synapses. 2. Describe the structure of the neuromuscular junction.  - **Components:** 1. **Presynaptic Terminal:** - Located on the axon terminal of a somatic motor neuron. - Contains **synaptic vesicles** filled with acetylcholine (ACh). 2. **Synaptic Cleft:** - The space between the presynaptic terminal and the muscle fiber. - Contains enzymes like **acetylcholinesterase** to break down ACh. 3. **Postsynaptic Membrane (Motor End Plate):** - Specialized region of the sarcolemma (muscle cell membrane). - Contains **nicotinic acetylcholine receptors (nAChRs)** that bind ACh. - **Function:** 1. An action potential in the motor neuron triggers ACh release. 2. ACh binds to receptors on the muscle, opening ion channels and initiating muscle contraction. 3. Compare the anatomy, neurotransmitters and receptors of the somatic motor, sympathetic, and parasympathetic divisions. (**WEAK)** **Comparison of the Somatic Motor, Sympathetic, and Parasympathetic Divisions** **Feature** **Somatic Motor** **Sympathetic Division** **Parasympathetic Division** ----------------------- --------------------------------------- ---------------------------------------------------------------------------------- ----------------------------------------------------------------------- **Function** Voluntary control of skeletal muscles Involuntary control (fight-or-flight) Involuntary control (rest-and-digest) **Anatomy** Single neuron from CNS to target Two neurons: preganglionic and postganglionic Two neurons: preganglionic and postganglionic **Ganglia** None Close to spinal cord (sympathetic chain ganglia) Near or within target organs **Neurotransmitters** Acetylcholine (ACh) ACh (preganglionic) and norepinephrine (NE, postganglionic) ACh (both preganglionic and postganglionic) **Receptors** Nicotinic (nAChRs) Preganglionic: Nicotinic (nAChRs) Postganglionic: Adrenergic (α and β receptors) Preganglionic: Nicotinic (nAChRs) Postganglionic: Muscarinic (mAChRs)  A diagram of a path to acetylcholine Description automatically generated **[Chapter 12]** 1. Diagram the molecular events of excitation-contraction coupling and the contractile cycle.  A diagram of a cell membrane Description automatically generated - **Excitation-Contraction Coupling:** 1. **Action Potential:** A neural signal triggers an action potential in the muscle fiber. 2. **Calcium Release:** The action potential travels down the **T-tubules**, causing the **sarcoplasmic reticulum (SR)** to release **Ca²⁺**. 3. **Troponin Binding:** Calcium binds to **troponin**, causing a conformational change that moves **tropomyosin** and exposes binding sites on actin. - **Contractile Cycle:** 4. **Cross-Bridge Formation:** Myosin heads bind to actin, forming cross-bridges. 5. **Power Stroke:** Myosin heads pivot, pulling actin filaments toward the center of the sarcomere. **ADP and Pi** are released. 6. **Release:** A new **ATP** molecule binds to myosin, causing it to detach from actin. 7. **Resetting:** ATP is hydrolyzed, re-cocking the myosin head for the next cycle. 8. **Cycle Repeats:** As long as **Ca²⁺** and ATP are present, the cycle continues. 2. Explain how muscle length influences force of contraction.  - **Length-Tension Relationship:** - The force a muscle can produce depends on its initial length: - **Optimal Length (Lo):** Sarcomeres have the ideal overlap of actin and myosin filaments, producing maximal tension. - **Overstretched:** Little overlap between actin and myosin leads to reduced cross-bridge formation and weak contraction. - **Overly Shortened:** Excessive overlap causes interference among filaments, reducing tension. - **Practical Application:** Muscles operate most efficiently near their optimal length in physiological conditions. 3. Define a motor unit, and explain how skeletal muscles use them to create graded contractions. A diagram of a motor neuron Description automatically generated - **Definition of a Motor Unit:** - A motor unit consists of a single somatic motor neuron and all the muscle fibers it innervates. - **Graded Contractions in Skeletal Muscles:** 4. Diagram smooth muscle contraction and relaxation. (REVIEW NOTES, MUST BE THOROUGH) - **Contraction:** 1. **Calcium Entry:** Ca²⁺ enters the cell from the extracellular fluid then additional Ca2+ is released from the SR. 2. **Calcium Binding:** Ca²⁺ binds to **calmodulin** (CaM). 3. **Activation of MLCK:** The Ca²⁺-CaM complex activates **myosin light chain kinase (MLCK)**. 4. **Phosphorylation:** MLCK phosphorylates myosin light chains and increases myosin ATPase activity 5. **Power Stroke:** Myosin heads interact with actin to generate contraction. - **Relaxation:** 6. **Calcium Removal:** Ca²⁺ is pumped out of the cell or back into the SR. 7. **MLCP Activation:** **Myosin light chain phosphatase (MLCP)** dephosphorylates myosin, reducing cross-bridge cycling. 8. **Return to Resting State:** Smooth muscle relaxes as cross-bridge activity decreases.  A diagram of a smooth Description automatically generated  **[Chapter 13]** 1. List four ways to classify neural reflex pathways. a. By the **efferent division** of the nervous system that controls the response i. Somatic reflexes vs. autonomic reflexes b. By the **CNS location** where the reflex is **integrated** ii. Spinal reflexes vs. cranial reflexes c. By whether the reflex **is innate or learned** iii. Innate reflexes vs. learned reflexes (conditioned reflexes) d. By the **number of neurons** in the reflex pathway iv. Monosynaptic reflexes vs. polysynaptic reflexes 2. Diagram a stretch reflex. A diagram of a stretcher Description automatically generated **A stretch reflex involves a direct pathway:** - **Stimulus: Stretch of the muscle spindle.** - **Pathway: Sensory neuron → Spinal cord → efferent output through Motor neuron → Contraction of the stretched muscle** - **Response: Contraction of the stretched muscle.** 3. Use the following terms to explain the patellar tendon reflex: monosynaptic stretch reflex, reciprocal inhibition, myotatic unit.  - **Monosynaptic Stretch Reflex:** - **The reflex arc consists of a single synapse. Tapping the patellar tendon stretches the quadriceps muscle, activating muscle spindles. The sensory neurons synapse directly with motor neurons in the spinal cord, causing the quadriceps to contract.** - **Reciprocal Inhibition:** - **While the quadriceps contract, inhibitory interneurons prevent contraction of the antagonist muscle (hamstrings). This ensures smooth movement.** - **Myotatic Unit:** - **The myotatic unit includes all muscles (agonists and antagonists) involved in the reflex response. For the patellar reflex, this includes the quadriceps (agonist) and hamstrings (antagonist).** 4. Diagram a flexion reflex and its associated crossed-extensor reflex. AKA Withdrawal reflex A diagram of the muscles of the leg Description automatically generated - **Flexion Reflex:** - Stimulus: Painful stimulus (e.g., stepping on a sharp object). - Response: Withdrawal of the affected limb (flexion of the knee). - **Crossed-Extensor Reflex:** - While one limb withdraws, the opposite limb extends to maintain balance. - Pathway involves interneurons that cross to the opposite side of the spinal cord. 1. Top of Form