Honors Biology Powerpoint #3 Unit 8 – Chapter 35 The Senses Activities

 Brain  Spinal Cord  Peripheral Nerves: Neurons

 Coordinates the body’s response to changes in its internal and external environments.

 Relays messages, processes information and analyzes information.  Includes: ◦ Brain ◦ Spinal Cord

 Sensory Division: transmits impulses from sense organs to central nervous system. ◦ What are sense organs?  Organs designed to pick up stimuli.  (ie eyes, ears, nose, skin)

 Motor Division: transmits impulses from the central nervous system to muscles.  Network of Neurons makes up the peripheral Nervous System.

1. Sensory Input triggered by stimuli conduction of signals to brain 2. Integration interpretation of sensory signals by brain 3. Motor output conduction of signals to effector cells (i.e. muscles, gland cells) sensory receptor (sensory input)  integration  (motor output)  effector

 Sensory neuroninterneuronmotor neuron  Without brain processing reflex arc pdf

 Dendrite - conducts “signal” toward the cell body -- [input zone] ◦ often short, numerous & highly branched ◦ signal comes from sensory cell or neighboring neuron  Axon - usually a single fiber -- [conducting zone] ◦ conducts signal away from cell body to another neuron or effector cell  Axon Ending ◦ a cluster of branches (100’s to 1000’s) ◦ relays signal to next neuron / effector cell

1) Resting - The neuron is POLARIZED (-70mV) There is a slightly negative charge on the inside, and a positive charge on the outside ◦ This balance is maintained by the sodium-potassium pump ◦ Pumps Na+ (sodium) outside ◦ Pumps K+ (potassium) inside ◦ Some K+ sneaks back out through channels How a nerve impulse is transmitted

2) Action Potential - stimulus causes opening of Na + gates, allowing Na+ to rush in This changes the neuron from polarized to de-polarized This is all-or-none, meaning a stimulus must exceed a threshold for the action potential to occur How a nerve impulse is transmitted

2) Action Potential - stimulus causes opening of Na + gates, allowing Na+ to rush in Intensity of the stimulus is based on the number of neurons that exhibit action potential. Speed on impulse based on diameter of axon & amount of myelination. How a nerve impulse is transmitted

3) Repolarization – K+ moves outside, Na+ stays inside ◦ After inside flooded with NA+, K+ gates open and let K+ Out (while NA+ gates close) How a nerve impulse is transmitted

4) Refractory period – When the Na+/K+ balance returns to normal (K+ on inside and Na+ outside) During this time the neuron will not respond to new impulses

Neurons DON’T touch The gap between the axon of one neuron, and the dendrites of another is called the SYNAPSE 1.Action potential happens 2.Neurotransmitter is released by axon ending 1.Neurotransmitter is a chemical that sends a signal 3.Neurotransmitter binds to dendrite membrane of next neuron 4.Excitation or inhibition of the membrane occurs 5.Neurotransmitter is ‘recycled’

 Resembles chain of beads  Allows signal to travel faster because impulse “jumps” from node of Ranvier to node of Ranvier (with myelin sheath (225 mph / without 11 mph)