Lecture Notes: Nervous System Flashcards
central nervous system
- Integration
- Brain
- Spinal Cord
Integration
association of stimuli with output
brain
integration of homeostasis, perception, movement, intellect and emotions
spinal cord
reflexes + transmits information from skin and muscles to brain
peripheral nervous system
- sensory (afferent)- mechanoreceptors linked to the CNS
2. motor (efferent)- CNS controlling effector cells
Voluntary (somatic)
- signals to skeletal muscles in response to stimuli
- reflexes and involuntary
Autonomic
- Involuntary
- Parasympathetic and Sympathetic
Parasympathetic
activities that gain and conserve energy
-slow heart beat, stimulate digestion
Sympathetic
activities that increase expenditure of energy
Neurons
transmission of electrical/chemical signals to conduct messages
- sensory, interneurons, motor
Sensory neurons
stimulated by receptors triggered by environmental stimuli
Interneurons
receive and transmit stimuli from and to other neurons
Motor neurons
transmit impulses from CNS to effector cells
Neuroglial cells
- do not conduct impulses
- support and orient
- protection
- insulation
- maintain ionic environment
- supply nutrients
types of neuroglial cells
- schwann cells (PNS)
- ogliodendrocytes (CNS)
- Astrocytes
Ogliodendrocytes
myelin sheath; electrical insulation
increase speed of impulse propagation
astrocytes
blood-brain barrier at brain capillaries
neurons are excitable cells
- 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)
Action Potentials
- 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
all or nothing principle
- 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
Resting Phase
- 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
phases of an AP
- depolarization
- threshold
- maximum depolarization
- repolarization
- hyperpolarization
Depolarization
- 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)`
Threshold
- 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.