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Function of the Nervous System
Coordinate and control multiple body functions through the integration and transmission of electrical signals throughout the body
Subdivisions of Nervous System
- 1. Central Nervous System
- 2. Peripheral Nervous System: Sensory Motor System and Automatic Nervous system-->sympathetic and pasrasympathetic nervous systm
Basic structural component of the Nervous System that transmits electrical signals
Tree like extentions from the cell body that recieve but do not conduct electrical signals. They generate local potentials but not action potentials.
Cell Body or Soma
Metabolic control center, houses nucleus, mitochondria and synthesizes signal transmitters. Signal reception and integration.
Specialized region of the cell between the Soma and Axon. Sums local signal potentials and produces an action potential which can travel down the axon.
A long thread like extension arising from the hillock area of the cell body. Transmits and action potential along its length.
The distal region of the axon subdivides into mutiple projections each of which is capped by a region of swelled cytoplasm called the terminal knob. Specialized for secretory activity.
Most common type of Neuron. Has multiple dendrite and a single axon, found in Central Nervous System. Muscle activator (motor neuron) of the Peripheral Nervous System.
Have one Axon and One Dendrite. The dendrite is part of a special sensory aparatus (eye, ear, etc.)
Only process (axon) extends from the cell body. This sends process in two direction and acts as a sensory neuron.
Type II Neurons
These cells have no axons. Used for local neuron to neuron integrations and communication within the central nervous system.
Electrical Property of Cells
Rely on movement of ions not electrons across cell membranes
"The Concentration Cell" Diffusion of K+ is resisted by charge attraction with impermiable CL-. Nernst Equation
Entrapment of Charged Molecules
At normal cell pH proteins usually display a negative charge. Proteins cannot pass the membrane they give inside of cell a negative charge. Force permeable ions to redistribute across membrane= Donan Equalibrium
Na+/K+ Exchange pump
Uses ATP to pump 2 Na+ ions out in exchange for moving 2 K+ ions into the cell. This tends to make the inside of the cell more negative than the outside.
Resting Membrane potential
Resembles to Equilibrium or Nernst Potential
Permeability of membranes and their electrical signaling properties are controlled by ion channels. Channels can be opened by a charge or chemical.
Various agents can change the resting membrane potential. On/Off Phenomenon.
An increase in cells negative charge
Decrease in cells negative charge towrds zero
depolarization of sufficient size to open gated Na+ channels
Increased Na+ permeability will allow ion movement across the membrane in response to:
Na Concentration gradient and internal negative charge
The local Positive (+) ion inflow will:
Open more voltage gated Na+ Channels, build up of internatal (+) opposes Na+ entry, K+ channels increase K+ Permeability
One Directional Transmission
The spike will travel down the length of the nerve cell membrane. Will activate neighboring Na+ channels.
Conduction Without Decrement
Homeostasis keeps K+ and Na+ constant, therefore the size of the ion flow along the axon is the same
Speed down the axon is increased by diameter of neuron, or an insulating fat sheath around the axon that cause rapid node to node jumping (myelination)
Signals are transmitted from cell to cell over specialized synapses
- 1. compose of Gap Junctions between cells
- 2. "pore" allows free flow of ions cell to cell and thus transfer of the signal between cells
- 3. Can send uni- or bidirectional signals
- 4. Seen in a few CNS cells and are the common link of smooth and cardiac Muscle Cells
Chemical Synapse Structure
- 1. compose of axon terminal knob and the adjoining region of the effector cell (nerve, muscle, gland)
- 2. terminal know contains many mitochondria and abundant vesicles
- 3. terminal knob membrane is called Presynaptic
- 4. Space between cells is called the Synaptic Cleft
- 5. The effector cell membrane is called Postsynaptic
Chemical Synapse Action
- 1. Signals reaching the axon terminal depolarize the knob memrane
- 2. depolarization opens voltage gate Ca++ channels
- 3. Ca++ influx into knob causes vesicles to fuse with the presynaptic memrane releasing contents (neurotransmitter) into the cleft
- 4. Neurotransmitters diffuse to the postsynaptic membrane
- 5. Neurotransmitters bind to Receptors on postsynaptic membrane opening lIGAN gate Channels there.
- 6. Ion inflow into effector cell changes its membrane potential--> signal is transmitted
- 7. Enzymes inactivate neurotransmitters turning the signal off
Complex Control Process
- 1. Multiple cell connection enable the contact of many other cells
- 2. Multiple transmitters: neurons produce transmitters for only certain cells, different transmitters can turn cell on or off
Determines strength importance and type of signal before deciding to take action
- 1. Can be either hyperpolarization (inactivating) or dpolarization (activating)
- 2. Can not activate neuron alone
- 3. Long duration and can spread across the neuron
- 4. Spartial Summation: two or more signals arriving at the same time but at different regions of the dendrite or cell body can be added together
- 5. Temporal Summation: Two or more signals arriving one right after the other can be added together.
- 6. Excitation vs. Inhibition: two or more signals having opposite membrane affects can be added together
- 7. If the summed electrical signals exceed the threshold value at the hillock that region will generate a new signal to be sent down the effector cell axon.
Basic functional component of Nervous System capable of receiving a stimulus and yielding a response
Physical Components of Reflex Arc
Rapid acting homeostatic controls
- 1. Sensory Receptor: initiate signal
- 2. Sensory Neuron: running in a peripheral nerve to transmit the impulse to the Central Nervous System
- 3. Interneuron in the CNS to pass the signal from the afferent to efferent neuron. These may also be connected to nerves in the spine and brain
- 4. Efferent or Motor Neuron: which passes thru the peripheral nerves to bring the signal to the effector organ
- 5. An effector organ which can respond to or correct for the senses problem
Recieves messages from the periphery via the dorsal sensroy roots and sends messages to the periphery via ventral motor roots. In communication with the brain.
Composed of Cerebrum and Diencephalon
divided into left and right hemipsheres as wells as section and lobes
anterior region believed to be the site of consciousness, learning, complex associations, motor complex
Anterior region housing Somatosensory area: touch, pain, pressure, sense
auditory and olfactory areas
Optic Vision Center
- 1. Thalamus Section: sensory relay station and participated in skeletol muscle control
- 2. Hypothalmus section : involved in most general body functions thru its control of the pituitary and the autonommic nervous system
Part of forebrain within the cerebrum and coordinates the activities of the cerebrum and diencephalon. Emotion and learning.
- 1. The midbrain and pons: are areas of dense nerve tracts that interconnect the body and medulla with the forebrain
- 2. Medulla Oblangata: contains many of the control and integration centers for major body systems
- 2. Reflector Formation: subpart of brainstem that coordinates function of the sections and communicates information coming from the body to the forebrain
The dorsal Projection off the brainstem under the cerebrum. Coordinates skeletol muscle movements, maintence of posture and balance. Learning especially physical tasks.
Peripheral Nervous System
Composed of nerves running to and from the brain and spinal cord
Nerves running to the CNS composed of sensory neurons
Nerves running ffrom the CNS. Motor neurons.
Nerves supplying the skin and skeletal muscles sensory fibers conduct impuses involved in touch, pain and pressure
nerves supplying internal body organs. Shares many sensory fibers with the somatic system. Independent of conscious efforts.
Cranial and Sacral nerves. Stimulation and maintenace of all necessary physiologic functions of a person at rest. Acetycholine.
Thoracic and Lumber Spinal nerves. Preparing the body for energy-expending, stressful for emergency situations. Noradrenaline.