Create app.py

app.py

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+# -*- coding: utf-8 -*-
+import streamlit as st
+import numpy as np
+import matplotlib.pyplot as plt
+
+st.set_page_config(page_title="Homeostasis Explorer", layout="centered")
+
+# -----------------------------
+# Systems with disturbance-specific roles
+# -----------------------------
+SYSTEMS = {
+    "Glucose": {
+        "setpoint": 90.0,
+        "units": "mg/dL",
+        "events": {
+            "Meal (carbs) – hyperglycemia": {
+                "disturbance_magnitude": +40.0,
+                "roles": {
+                    "Sensor": "Pancreatic β-cells (detect ↑ glucose)",
+                    "Control Center": "Pancreatic β-cells (insulin secretion)",
+                    "Effector(s)": "Insulin → liver (↑glycogenesis, ↓gluconeogenesis), muscle/adipose (↑GLUT4 uptake)"
+                },
+                "note": "Hyperglycemia evokes insulin to lower glucose."
+            },
+            "Light exercise / fasting – hypoglycemia": {
+                "disturbance_magnitude": -20.0,
+                "roles": {
+                    "Sensor": "Pancreatic α-cells (detect ↓ glucose)",
+                    "Control Center": "Pancreatic α-cells (glucagon secretion)",
+                    "Effector(s)": "Glucagon → liver (↑glycogenolysis, ↑gluconeogenesis); adipose (↑lipolysis)"
+                },
+                "note": "Hypoglycemia evokes glucagon and counter-regulatory hormones to raise glucose."
+            }
+        },
+        "k_time_constant": 6.0,
+        "feedback_gain": 0.35
+    },
+
+    "Temperature": {
+        "setpoint": 37.0,
+        "units": "°C",
+        "events": {
+            "Cold exposure (↓T)": {
+                "disturbance_magnitude": -5.0,
+                "roles": {
+                    "Sensor": "Peripheral & central thermoreceptors (detect ↓temp)",
+                    "Control Center": "Hypothalamus (thermoregulatory center)",
+                    "Effector(s)": "Shivering, cutaneous vasoconstriction, (± brown fat thermogenesis)"
+                },
+                "note": "Cold evokes heat production & conservation."
+            },
+            "Heat exposure (↑T)": {
+                "disturbance_magnitude": +2.5,
+                "roles": {
+                    "Sensor": "Peripheral & central thermoreceptors (detect ↑temp)",
+                    "Control Center": "Hypothalamus",
+                    "Effector(s)": "Sweating, cutaneous vasodilation"
+                },
+                "note": "Heat evokes heat dissipation."
+            }
+        },
+        "k_time_constant": 5.0,
+        "feedback_gain": 0.40
+    },
+
+    "Blood Pressure (MAP)": {
+        "setpoint": 95.0,
+        "units": "mmHg (~MAP)",
+        "events": {
+            "Standing quickly (orthostatic ↓MAP)": {
+                "disturbance_magnitude": -15.0,
+                "roles": {
+                    "Sensor": "Baroreceptors (carotid sinus, aortic arch) sense ↓ stretch",
+                    "Control Center": "Medullary cardiovascular centers",
+                    "Effector(s)": "↑HR, ↑contractility, arteriolar vasoconstriction, venoconstriction"
+                },
+                "note": "Baroreflex counters an acute drop in MAP."
+            },
+            "Pain/startle (↑MAP surge)": {
+                "disturbance_magnitude": +10.0,
+                "roles": {
+                    "Sensor": "Baroreceptors sense ↑ stretch",
+                    "Control Center": "Medullary cardiovascular centers",
+                    "Effector(s)": "↑Vagal tone/↓sympathetic tone → ↓HR, ↓contractility, vasodilation"
+                },
+                "note": "Baroreflex counters an acute rise in MAP."
+            }
+        },
+        "k_time_constant": 4.5,
+        "feedback_gain": 0.45
+    },
+
+    "pH": {
+        "setpoint": 7.40,
+        "units": "pH",
+        "events": {
+            "Hypoventilation (resp. acidosis tendency)": {
+                "disturbance_magnitude": -0.10,
+                "roles": {
+                    "Sensor": "Central & peripheral chemoreceptors (↑CO₂/H⁺)",
+                    "Control Center": "Medullary respiratory centers",
+                    "Effector(s)": "↑Ventilation (↑RR and/or tidal volume) to blow off CO₂"
+                },
+                "note": "Ventilation rapidly raises pH back toward 7.4."
+            },
+            "Hyperventilation (resp. alkalosis tendency)": {
+                "disturbance_magnitude": +0.10,
+                "roles": {
+                    "Sensor": "Central & peripheral chemoreceptors (↓CO₂/H⁺)",
+                    "Control Center": "Medullary respiratory centers",
+                    "Effector(s)": "↓Ventilation (↓RR and/or tidal volume) to retain CO₂"
+                },
+                "note": "Ventilation lowers pH back toward 7.4."
+            }
+        },
+        "k_time_constant": 3.5,
+        "feedback_gain": 0.50
+    }
+}
+
+# -----------------------------------
+# Simple negative-feedback model
+# x' = D(t) - k*(x - set) - g*(x - set)
+# -----------------------------------
+def simulate(system_name, event_name, duration=60.0, dt=0.1):
+    sys = SYSTEMS[system_name]
+    setpoint = sys["setpoint"]
+    k = 1.0 / sys["k_time_constant"]
+    g = sys["feedback_gain"]
+
+    t = np.arange(0.0, duration + dt, dt)
+    x = np.ones_like(t) * setpoint
+
+    D = np.zeros_like(t)
+    mag = sys["events"][event_name]["disturbance_magnitude"]
+    D[(t >= 5.0) & (t < 15.0)] = mag
+
+    for i in range(1, len(t)):
+        error = x[i-1] - setpoint
+        feedback = -g * error
+        dxdt = D[i-1] - k*error + feedback
+        x[i] = x[i-1] + dxdt * dt
+
+    return t, x, setpoint, sys["units"]
+
+# -----------------------------
+# Streamlit UI
+# -----------------------------
+st.title("Homeostasis Explorer: Negative Feedback")
+st.markdown(
+    """Select a **System** and a **Disturbance**, then click **Run Simulation**.
+Roles update based on the disturbance; the plot shows the variable returning toward its set point."""
+)
+
+# Controls
+system = st.selectbox("System", list(SYSTEMS.keys()), index=0)
+event = st.selectbox("Disturbance", list(SYSTEMS[system]["events"].keys()), index=0)
+
+# Run button with initial auto-render
+if "init" not in st.session_state:
+    st.session_state.init = True
+
+run = st.button("Run Simulation")
+if st.session_state.init or run:
+    st.session_state.init = False
+
+    t, x, setpoint, units = simulate(system, event, duration=60.0, dt=0.1)
+
+    fig, ax = plt.subplots(figsize=(8, 4))
+    ax.plot(t, x, label="Observed variable")
+    ax.axhline(setpoint, linestyle="--", label=f"Set point = {setpoint} {units}")
+    ax.axvspan(5.0, 15.0, alpha=0.1, label="Disturbance window")
+    ax.set_xlabel("Time (a.u.)")
+    ax.set_ylabel(f"{system} ({units})")
+    ax.set_title(f"{system} response to: {event}")
+    ax.legend(loc="best")
+    st.pyplot(fig)
+
+    roles = SYSTEMS[system]["events"][event]["roles"]
+    note = SYSTEMS[system]["events"][event]["note"]
+
+    st.subheader(f"Feedback Roles — _{event}_")
+    st.markdown(
+        f"- **Sensor:** {roles['Sensor']}\n"
+        f"- **Control Center:** {roles['Control Center']}\n"
+        f"- **Effector(s):** {roles['Effector(s)']}"
+    )
+    st.caption(f"*Note:* {note}")
+
+st.info("Tip: Adjust the selections and click **Run Simulation** again to compare responses.")