communicate sensory information from sensory receptors to CNS
Somatic Nervous System
transmits electrical signals from CNS to skeletal muscles. Voluntary controlled movements
Autonomic Nervous System
transmits electrical signals from CNS to smooth muscle in viscera, cardiac muscle and glands. Involuntary control.
Sympathetic Nervous System
"fight or flight" dilates pupils, inhibits flow of saliva, dilates bronchi, accelerates heartbeat etc.
Parasympathetic Nervous System
"rest and digest" stimulates flow of saliva, slows heartbeat stimulates peristalsis and digestion
conduct action potentials. for highly complex connections with other neurons.
Support cells for neurons. 1:10 neuron to glial cell ratio
defined by the presence of the nucleus-contains DNA. Round, centrally located. Direct Cell's metabolism. Controls protein synthesis. Where general integration occurs
Input zone. Receives information from other neurons. Connections with many neurons. If enough inputs, the cell's Axon will generate an action potential.
Transmits neural signal away from cell body. One axon per cell. Two distinct parts: Axon- conducting zone and the Axon Terminal- output zone. Axon can branch out to reach out to many different places.
star shaped cell. regulate extracellular composition of brain fluid. sucker-like extensions attached to blood vessels.
specialized cells. Act as mobile macrophages. They remove debris from injured or dead cells and create a healthy environment
form extensions that wrap around portions of several axons, located in the CNS Schwann Cells, like oligo's in PNS, but can only wrap around a portion of one axon.
White fatty casing around axons. Acts as electrical insulator, increasing the speed of the neural signal. It is not present on all cells.
Depends on the movement of ions across the plasma membrane. Ions involved: Sodium, Potassium, Chloride, Organic Anions. Neurons have a resting membrane potential; different ions are concentrated on different sides of the membrane.
Movement of the action potential
Na+ influx depolarizes adjacent segments of the axon, opening new voltage-gated Na+ channels. The refractory period ensures the AP moves in one direction, down the axon towards the terminal region.
ensure the adjacent membrane will polarize and the action potential continues to move down the membrane. More efficient form of conduction is saltatory conduction
Myelination provides insulation that resists the flow of ionic current. Action potential occur at breaks in the myelination called Nodes of Ranvier.
Specialized junctions allowing communication between neuron and target cells. Chemical synapses use chemical signals called neurotransmitters for this communication
released by the presynaptic neuron, then diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane.
Post Synaptic Effects of Neurotransmitters
Neurotransmitters bind to receptors gates ion channels in two ways: Ionotropic Receptors and Metabotropic Receptors
Directly controls an ion channel. Fast, short-lived neurotransmission.
Activate G proteins that initiate intracellular signaling pathways. Slow sustained response to neurotransmitters.
Factors in Neurotoxicity
High metabolic rate of neurons. Blood Brain Barrier
Blood Brain Barrier
Tight endothelial capillary/ astrocyte junction increase resistance to passage of molecules. Only lipophilic molecules can pass rapidly into the brain without a transporter. Protective mechanism. Circumventricular organs are "leaky" regions
The blood Brain Brier is incomplete in these areas, hence "leaky". These organs monitor the composition of the blood and secrete various hormones and neurotransmitters.
Examples of Circumventricular Organs
Area Postrema: vomit center. Pineal Gland: regulates releases of melatonin; cardiac rhythms. Median Eminence: release of hormones to regulate the anterior pituitary gland.