Nervous System
Two Regulatory Systems Nervous System Fast! Short duration effect Electric (ionic) signals …but also chemicals (neurotransmitters) Affects nearby cells (local) Endocrine System Slower to start Longer duration effect Chemical signals (hormones) Affects any cell (long distance)
NS & ES are Related 1. Neurosecretory Cells In brain, but secrete hormones Ex: epinephrine as hormone & neurotransmitter 2. Each system affects outcome of other Ex: suckling…neurons…oxytocin…more milk Ex: chemoreceptors detect glucose in blood…pancreas secretes insulin/glucagon
NS & ES are Related 3. Feedback Mechanisms Positive Negative Ex: suckling/oxytocin Negative Ex: calcium levels/ PTH/calcitonin
Nervous System The Cellular Level Intro Video - Signaling
Neuron = Nerve Cell How does its structure fit its function? Axon Dendrite Myelin sheath
Gated Ion Channels open or close in response to 3 kinds of stimuli Stretch–gated - in cells that sense stretch; open when membrane mechanically deformed Ligand–gated - at synapses; open/close when specific neurotransmitter binds to channel Voltage–gated - in axons; open/close when membrane potential changes Gated ion channels are responsible for generating the signals of the nervous system
Membrane Potential the outside of the cell is more positive the difference in charge while it is not “firing” is called the “resting potential” Interactive Guide – Action Potential: http://brainu.org/files/movies/action_potential_cartoon.swf Video - Action Potential http://www.dnatube.com/video/1105/Understanding-Action-Potential-and-Nerve-Impulses Action Potential Cartoon –Self-Guided Action Potential Video
Voltage-Gated Ion Channels Resting state…more (+) outside than inside
Voltage-Gated Ion Channels Stimulus causes Na channels to open
Voltage-Gated Ion Channels Once enough Na+ moves in, membrane is “depolarized”
Voltage-Gated Ion Channels Next, K+ gates open to allow them to move out…just as Na+ gates close… ”repolarization”
Voltage-Gated Ion Channels
Propagation of the Action Potential How related to neuron? As Na+ ions move in, the potential “flip-flops” triggering K+ gates to open Meanwhile the Na+ ions diffuse over to next area causing the “flip-flop” in charge And it goes on and on…
Propagation of the Action Potential
Saltatory Conduction Action potentials can only be generated at nodes of Ranvier (myelin sheath blocks membrane)…message hops quickly
~ More Na+ outside…more K+ inside (salty banana) How do the Na/K concentrations return to resting state? …the Na-K Pump! ~ More Na+ outside…more K+ inside (salty banana) ~ K tends to leak out…leaving negative ions in ~ Na-K pump maintains this difference Video – Sodium-Potassium Pump http://www.youtube.com/watch?v=GTHWig1vOnY Video - Sodium-Potassium Pump
Na-K Pump (Active Transport) More Na+ outside…more K+ inside ATP allows movement of 3 Na out (uses 1 ATP) Then 2 K pulled in Video – Sodium-Potassium Pump http://www.youtube.com/watch?v=GTHWig1vOnY Video - Sodium-Potassium Pump
A Chemical Synapse Video - Synapse Video – Synapse http://www.dnatube.com/video/261/Synapse-The-place-of-information-exchanege Video - Synapse
A Chemical Synapse Depolarization triggers Ca-channels to let Ca ions enter Synaptic vesicles (w/ neurotransmitters) fuse with presynaptic membrane Receptors on post-synaptic membrane bind neurotransmitter Depolarization of gates carries message along
Integration of Multiple Synaptic Inputs Each neuron makes connections with many other neurons
The Organs & their Functions Nervous System The Organs & their Functions
Overview of the Vertebrate Nervous System
Overview of the Vertebrate Nervous System “Sensory receptor” – may be “special senses” - light (vision), chemicals (taste & smell), movement (hearing) Or…
Overview of Vertebrate Nervous System “Sensory receptor” – may be general senses - pressure, movement, temperature, chemicals, pain, location in space
Overview of Vertebrate Nervous System Effector = skeletal, smooth, or cardiac muscle or glands
Diversity in Nervous Systems Don’t need to memorize…just compare
Structural Divisions of the NS CNS Brain Spinal cord PNS Nerves
Functional Divisions of the PNS Sense Move Automatic Choice Rest & digest Rev you up!
Parasympathetic & Sympathetic
Embryonic Brain Development Don’t memorize…notice the pattern
Human Brain
Human Brain Cerebrum – “thinking”; conscious actions; all the fancy stuff Cerebellum – coordinates voluntary muscle movements Brainstem – basic life functions (involuntary stuff) Hypothalamus – homeostasis (hunger, thirst, etc)
Cerebrum – Functional Areas The brain integrates most functions but there is some centralization… Vision – hearing – higher though – motor/sensory – speech on left 35
Primary Motor/Somatosensory Areas of Cortex Which motor areas get the most attention? Why does that make sense?
Primary Motor/Somatosensory Areas of Cortex Which sensory areas get the most attention? Does that make sense? Is this the same as for the motor cortex?
The Limbic System Memory – emotion - … Note the association with the special senses
Reflexes Purpose – quickly respond to danger What selection pressure for this to develop?
The Reflex Arc Components Stimulus - signal detected by sensory neuron Sensory neuron carries msg to spinal cord Decision made …U-turn at the interneuron Motor neuron sends back reposnse Effector – completes response; muscle or gland
The End