add discription of channels and functions architecture (#473)

Co-authored-by: simone@simoneslaptop <simone@simoneslaptop>

docs/tutorials/05_channel_and_synapse_models.ipynb

@@ -75,7 +75,9 @@
    "metadata": {},
    "source": [
     "### Your own channel\n",
-    "Below is how you can define your own channel. We will go into detail about individual parts of the code in the next couple of cells."
+    "Below is how you can define your own channel. We will go into detail about individual parts of the code in the next couple of cells.\n",
+    "\n",
+    "Note that a channel needs to have the functions `update_states` and `compute_currents` and `init_states` with all input arguments shown below. "
    ]
   },
   {
@@ -271,6 +273,8 @@
     "\n",
     "The parts below assume that you have already learned how to [build network simulations in `Jaxley`](https://jaxleyverse.github.io/jaxley/latest/tutorial/02_small_network/).\n",
     "\n",
+    "Note that again, a synapse needs to have the two functions `update_states` and `compute_current` with all input arguments shown below. \n",
+    "\n",
     "The below is an example of how to define your own synapse model in `Jaxley`:`"
    ]
   },