Lecture Notes: Nervous System

• Integration • Brain • Spinal Cord

association of stimuli with output

integration of homeostasis, perception, movement, intellect and emotions

reflexes + transmits information from skin and muscles to brain

• sensory (afferent)- mechanoreceptors linked to the CNS 2. motor (efferent)- CNS controlling effector cells

• signals to skeletal muscles in response to stimuli - reflexes and involuntary

• Involuntary - Parasympathetic and Sympathetic

activities that gain and conserve energy -slow heart beat, stimulate digestion

activities that increase expenditure of energy

transmission of electrical/chemical signals to conduct messages - sensory, interneurons, motor

stimulated by receptors triggered by environmental stimuli

receive and transmit stimuli from and to other neurons

transmit impulses from CNS to effector cells

• do not conduct impulses • support and orient • protection • insulation • maintain ionic environment • supply nutrients

• schwann cells (PNS) • ogliodendrocytes (CNS) • Astrocytes

myelin sheath; electrical insulation increase speed of impulse propagation

blood-brain barrier at brain capillaries

• sodium potassium pump maintains a membrane potential • neurons can change their membrane potential in response to stimuli • selective opening of gated channels (voltage or chemical)

• rapid (1-2ms) reversal in membrane potential that propagates throughout a cell membrane without changing it’s magnitude. • APs are only produced by depolarizing stimuli • “All or nothing principle” must reach threshold

• once a voltage threshold is reached the AP will occur • amplitude of AP not affected by intensity of stimulus • systems distinguishes between weak and strong stimuli based on frequency of AP

• Sodium Potassium Pump • Leak Potassium channels: always open • Voltage-gated K+ channels: closed • Voltage-gated Na+ channels: closed • large negatively charged molecules remain inside • membrane potential: about -70 mV

• depolarization • threshold • maximum depolarization • repolarization • hyperpolarization

• Voltage-gated K+ channels: closed • some voltage-gated Na+ channels opened • –activation gate:open • –inactivation gate:closed • influx of sodium, causing membrane potential to decrease ( becomes more positive)`

• influx of sodium causes voltage gated sodium channels to open, which then causes a membrane potential threshold to be reached • more voltage gated sodium channels open and there is more influx of sodium • rapid reversal in membrane potential (inside more positive than outside.