Flashcards in 211 -2 Deck (18)
Mwjor division of nervous System
Central nervous system
Central Nervous System (CNS) comprises the brain and the spinal cord
Peripheral nervous system
Peripheral Nervous System (PNS) consists of everything outside the skull and spinal column
Interacts with external environment
§ Afferent nerves
Carry sensory signals from eyes, ears, skin, etc TO CNS
§ Efferent nerves
Carry motor signals FROM CNS to skeletal muscles
afferent = toward
Regulates body’s internal environment
§ Afferent nerves
Carry sensory signals from internal organs TO CNS
§ Efferent nerves
Carry motor signals FROM CNS to internal organs
§ Afferent: Going towards (approach, advance)
§ Efferent: Going away (exit, escape)
Santiago Ramón y Cajal (1852 - 1934, a pioneer of neuroscience)
what did he do
Basic structure cf cell
cell body /Soma
has gaps in it!
3 types of neurons
integrates a lot -one process emirate soma
Multipolar neurons have one axon and many dendrites attached
to its soma. Several dendrites allow for integration of a great deal of information.
Bipolar neurons have two processes leaving the soma. At one end, there is a single dendritic tree. They transmit sensory information (e.g. vision, audition).
Unipolar neurons have one process extending from the soma; the axon then divides into two branches. They detect touch, temperature changes, pain and other sensory events that affect the skin.
Interneurons link sensory and motor neurons.
The synapse ?
the Soma is ?
surrounded ky permeable membrane
-rlidions take places within lit
DNA in nucleus
transcription = Copying dna
MRNA attaches tv ribosome
genome is protein or chromosome
neurons nigh metabolic rate at neurons means need supporting cells
Neuroglia (or Glial cells)
Glia surround the neuron and support the nervous system
1. Astrocyte is a glial cell that provides physical support and cleans up debris in the brain. They control chemical composition and nourish the neuron.
2. Oligodendrocytes provide support to the axon of the cell and produce the myelin sheath which forms a tube around the axon for insulation. The sheath is not continuous; it is a series of segments. The exposed axon is called the node of Ranvier.
3. Microglia are the smallest of the glial cells. They provide an immune system for the brain and protect the brain from invading microorganisms.
Blood brain barrier
Blood brain barrier functions ?
A semipermeable barrier between the blood and the fluid that surrounds the cells of the brain
Functions of the blood-brain barrier:
1. To provide a balance between substances within neurons and in the extracellular fluid. An imbalance can disrupt the transmission of messages thus affecting brain function.
2. Impedes the passage of toxic substances.
Note on drugs that designed to get pest it
neuron elletnied electrical potential
-derived from squid
-Huxley cut axon = still functional!
Lrnow brow it ii measured
1. A wire electrode is placed in the extracellular fluid; it is an electrical conductor that provides a path for the electricity to enter or leave the medium.
2. A fine glass microelectrode is inserted into the axon. This records activity of the neuron.
3. The oscilloscope, a sensitive voltmeter, turns electrical fluctuations into visible signals
The difference in the charge between the inside of the axon and the extracellular fluid is the membrane potential.
§ The neurons resting potential is when the steady membrane potential is -70mV. The inside of the axon is negative.
§ In its resting state, the neuron is polarized.
§ We can stimulate the neuron by passing a positive charge through another microelectrode. This changes the value of the membrane potential (towards zero). The neuron is now depolarized
The action potential is a rapid reversal of the membrane potential (i.e. the inside of the membrane becomes positive). It’s peak is +30 mV.
§ The membrane quickly restores to normal (within 2 msec), but first the potential overshoots the resting potential and becomes hyperpolarized (more negative).
§ The value of the membrane potential that must be reached to produce an action potential is called the threshold of excitation
threshold of excitation
The value of the membrane potential that must be reached to produce an action potential
§ A ion is a charged molecule. Cations are positive, and anions are negative.
(e.g. NaCl = Na+ cation; Cl ̄ anion).
§ Forces of
diffusion move ions from high concentration to low concentrations
§ Electrostatic pressure refers to the attractive or repulsive forces between the charged ions.
§ The membrane potential is maintained by the balance of diffusion and electrostatic forces. These forces are influenced by the concentration of the fluids inside the cell (intracellular) and outside of the cell (extracellular
the r-sfing potential
Four important ions produce the resting potential: an organic Anion (A ̄); Sodium (Na+); potassium (K+); Chloride (Cl ̄).
The cell membrane is semipermeable: it allows certain molecules to pass but not all of them
When resting it is generally -ve and potassiun high inside cell
High Nac1 outside dell
the potassium sodium transporter pump ?
§ The sodium-potassium pump continuously pushes Na+ ions out of the cell.
§ The membrane is not very permeable to Na+ .
§ Sodium-potassium transporters, energised by adenosine triphosphate (ATP) molecules produced by the mitochondria, exchange 3 Na+ ions for
What causes the Action Potential?
§ The action potential occurs when there is a sudden influx of positive Na+ ions into the cell.
§ This influx is caused by a transient increase in the permeability of the membrane to NA+ which is then followed by a transient permeability to K
§ This permeability is provided by ion channels that act as pores which open or close.Sibl 4 ft force
threhold at excitation must he reached
alter permeability charges polarity
see slide for diagram!