Welcome back to our systems talks! Today will be about nervous system.
The nervous system is tasked with controlling all our movements, thoughts, and processes. Major organs include the brain, spinal cord, nerves, and blood vessels, and neurons, or nerve cells which are their functional units. Neurons are organized into nerve nets, and in complex organisms, nerves, which are bundles of fiber extensions of neurons. The brain and the longitudinal nerve cord, or our spine, consists of the central nervous system (CNS). The ventral nerve cords, ganglia, and nerves compose the peripheral nervous system (PNS) in more complex organisms.
Sensory neurons transmit information picked up by sensors that detect light, touch, sound, taste, and smell. The information is sent to the CNS inter-neurons that analyze it and send the response to motor neurons that communicate with effector cells. The actions by the response is called a reflex.
All cells have an electric potential voltage across their cellular membrane, and this is called membrane potential. When a neuron is not transmitting signals it is a resting potential. Action potential is the signal conducted by axons. Hyperpolarization causes an increase in the membrane potential and depolarizations decrease. Thresholds are the limits to the polarizations. If a stimulus is strong enough to reach a threshold to trigger a response, the response is an action potential.
The resting potential depends on ions and their gradients across the cell membrane. In mammals sodium-potassium pumps maintain resting potential. The diffusion of potassium and sodium creates the resting potential from ion channels that are ungated. Gated ion channels open according to 3 different stimuli. Stretch-gated ion channels in cells that sense stretch and open at a deformed membrane. Ligand-gated ion channels are found in synapses that open to a neurotransmitter that binds to a receptor. Voltage-gated ion channels are in axons that open at a change membrane potential.
Lastly, we will discuss neurotransmitters. Neurotransmitters bind to receptors to open pathways and cause certain responses or send specific signals.
Thank you and keep reading!
Written by Neil 6/1/2019