-
Sensory function
sense changes in internal and external environment thru SENSORY receptors
-
Integrative function
Analyze SENSORY information, stores some aspects and makes decisions regarding behaviors
-
Motor function
respond to stimuli by initiating action
-
CNS
central nervous system: consists of brain and spinal cord
-
PNS
peripheral nervous system: consists of cranial & spinal nerves, contain
-
Somatic Nervous System
- voluntary
- Involves:
- neurons from sensory receptors to the CNS
- Motor neurons to the skeletal muscle tissue
-
Autonomic Nervous System
- involuntary
- Involves:
- neurons from visceral organs to the CNS
- motor neurons to the smooth & cardiac muscle
- -sympathetic division: fight or flight
- -parasympathetic division: rest & digest (essential for life)
-
Resting Membrane Potential
- -70mV - cell is polarized (more positive extracellular)
- involves more Na outside of cell and more K inside cell
- NEGATIVE ions INSIDE cell membrane..and POSITIVE ions OUTSIDE cell membrane
-
What happens during an action potential?
Voltage-gated Na and K channels open in sequence
-
Depolarization
- results from a chemical or mechanical stimulus
- Voltage-gated Na channels open and Na rushes into the cell
- -55mV (cell is more positive due to influx of Na)
- Positive feedback process
-
Repolarization
- K+ channels open
- -70mV (K releases from cell decreasing its positive charge)
- K channels opening is slower than Na influx
- Na flow influx starts once K channels finally open
-
Hyperpolarization
- Too much K+ is released from cell
- -90mV (need to put more K into the cell to go back to -70mV resting potential)
-
Refractory Period
involves when a neuron cannot operate another action potential
-
Absolute Refractory Period
when even a strong stimulus cannot begin another action potential
-
chemical vs electrical synapses
- Electrical: tissue --> nerve, can also synchronize groups of neurons
- Chemical: nerve --> nerve. Info transfer from presynaptic neuron to a postsynaptic neuron
-
Does strength of the stimulus relate to the speed of the nerve impulse?
No, the speed of the impulse is the SAME no matter what strength of stimulus
-
Chemical Synapses characteristics
- One-way info transfer
- Action potential reaches end bulb and voltage-gated Ca+2 channels open
- Ca+2 flows inward triggering release of neurotransmitter
- Neurotransmitters cross synaptic cleft and bind to receptors (the more neurotransmitters released the greater change in potential of postsynaptic cleft)
-
Result of Ca in BAD neurons
vasorestriction - LACK of blood supply to the area
-
Effects of Neurotransmitters
- Excitatory
- Inhibitory
- Both effects present in PNS and CNS
- Same neurons can be both excitatory and inhibitory
-
Excitatory effect on neurotransmitter
- occurs during depolarization, this postsynaptic potential is called EPSP
- results from opening of Na channels
- Postsynaptic cell MORE likely to reach threshold
-
Inhibitory effect on neurotransmitter
- results from opening of Cl- or K+ channels
- Causes postsynaptic cell to become more Hyperpolarized
- postsynaptic cell LESS likely to reach threshold
-
Summation
the release of neurotransmitters at the same time
-
Agonist
enhances neurotransmitter effects
-
Antagonist
blocks action of neurotransmitters, decreasing their effect
-
3 responses
- 1. Small ESPS occurs: potential reaches -56mV ONLY
- 2. impulse is generated: threshold reaches, membrane potential is AT LEAST -56mV
- 3. ISPS occurs: membrane is HYPERPOLARIZED, potential drops BELOW -70mV
-
Neural circuits
- network of neurons may contain thousands or millions of neurons
- These circuits are involved in many activities, including:
- breathing
- short-term memory
- waking up
-
Regeneration and Repair of Neurons
- PNS can repair damaged dendrites or axons, BUT mostly scar tissue forms instead
- CNS has NO possible form of repair, due to: lack of neurolemma and growth stimulating factors
- due to rapid formation of scar tissue
|
|
