- General function: reception and processing of sensory information (internal and external environment)
- 2 systems work together
Central NS: brain & spinal cord
. Brain protected by the skull
. Brain has direct connection with spinal cord (protected by vertebral column)
Peripheral NS: nerves (lie outside of CNS)
- Figure
Black: how CNS communicates with somatic NS and autonomic NS
Red: how CNS receives sensory info
- 3 specific functions
1. Receiving sensory input
. Via receptors in skin and other organs
. Generates nerve signals: from PNS -> CNS
2. Information processing and integration (CNS)
. Reviews, stores information as memories
. Creates appropriate motor response
3. CNS generates motor output
. Nerve signals: CNS -> PNS -> muscles/glands
Nervous tissue
- Has 2 types of cells
Neurons
. Function: transmission of nerve impulses between parts of NS
Neuroglia/glial cells
. Function: supporting and nourishing neurons
. Way more neuroglia than neurons in brain
. Myeline formed from membranes of tightly spiraled neuroglia
Shwann cells (PNS): gaps between = node of Ranvier
Oligodendrocytes (CNS)
. Microglia: phagocytic cells that help remove bacteria
. Astrocytes: metabolic and structural support directly to neurons
- Figure -> B) in CNS, some interneurons have a short axon that is not covered by myeline
Neuron anatomy
- 1. Sensory neurons
Function: signals from receptor to CNS
Sensory receptors: see change in environment
- 2. Interneurons
Function: sum up all the info received and communicates with motor neuron
Signals from sensory neurons or other interneurons
Lies within the CNS
- 3. Motor neurons
Function: takes nerve impulses away from the CNS to effector (muscle/organ/gland)
Effectors: carry out our responses to environmental changes
- Structure
Cell body: nucleus and organelles
Dendrites: receives signal from sensory neurons/receptors
Axon: conducts nerves signals/impulses received from the dendrites
. Nerve fiber: individual axon -> collectively: nerve
. Sensory neurons
Long axon carries signals from dendrites associated with sensory receptor to CNS
Axon interrupted by cell body
. Interneurons/motor neurons
1
, Zelfstudie
Multiple dendrites carry signals to cell body
Then axon conducts nerve signals away from the cell body
- Myeline around axons
Myeline: shwann or oligod. Wrap their membranes around axon
. Not all axons have myeline (shorts ones don’t have any)
Nodes of Ranvier: free spots without myeline
Function: transmissions peed, insulator, nerve regeneration PNS (new fiber growth when axon breaks)
. MS (multiple sclerosis): myeline breaks down -> difficulty with transmitting signals
Gray matter in CNS: no myeline
White matter in CNS: a lot of myeline
Neuron physiology
- In the past: only excised (taken from the body) neurons could be studied
Resting Potential (see doc for foto)
- Like a battery: energy by separating positive and negative ions
Potential energy: used for work
- Resting potential: resting neuron has potential energy because plasma membrane is polarized
Polarizing: positive ions outside the cell, negative ions in the cell
- During action potential: Cell reaches threshold -> depolarisation -> repolarisation
- Positive outside (Na+)
Rest: membrane permeable to K+, not to Na+
K+ goes from inside the cell to the outside -> even more positive outside now
- Negative outside
Negative proteins and other molecules -> to big to diffuse
Action Potential
- Energy measured in volt (V) -> normally a cells has 0.070 V or 70 millivolts (mV)
Is a negative number (comparing negative inside to positive outside)
- Neurons must maintain their resting potential to work
By pushing Na+ out (more positive outside) of the cell and K+ into the cell (less positive outside)
- Action potential: conduction of nerve signals
In the axons of neurons
All or nothing event with threshold, only takes 3-4 ms
Ex: pushing a needle in your arm
. Pushing harder will not make the action potential stronger
. But! There will be more action potentials -> pain perceived as more intense
- Voltage-gated channels (protein channels)
Specific for Na ions
In plasma membrane of axon
- Action potential: Na+ gate opens -> Na+ into the cell -> inside more positive than outside (depolarisation: -70 mV
-55 mV -35 mV) -> Na+ gate closes -> K+ gate opens -> K+ to the outside of the cell -> inside becomes
negative again (repolarisation: ) -> sodium-potassium pomp: K+ to the inside & Na+ to the outside (completion)
Propagation of an Action Potential
- Unmyelinated fibers: slow action potential (1 m/s, small fibers)
Each axon must be stimulated
Action potential stimulates adjacent part of the axon membrane
- Myelinated fibers: fast action potential (100 m/s, thick fibers) = salutatory condition
Jumps from one node of Ranvier to the other
- Self-propagating: each AP generates another AP along the entire length of the axon
Conduction is all or nothing event
Intensity: how many AP in a given time
- Refractory period after conducting and AP -> ensures one-way direction
2
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller PsychologieStudent1303. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $4.06. You're not tied to anything after your purchase.