57 terms

The Nervous System

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The Nervous system
is communication network that controls and coordinates the body activities.

Every though, memory, emotion or sensation a person has and every action he or she carries out is reflection of the nervous system.

works unnoticed to regulate a multitude of internal events such as blood pressure, hear rate, and body temperature in order to maintain homeostasis.
General Components
1. Neuron
2. Three functions drive the nervous system
Neuron
*Nerve cell
*are unique in their ability to transmit electrical signals called nerve impulses at high speeds throughout the entire body in a split second.
Three functions drive the nervous system
i. sensory input
II. Processing/Integration Center
III. Motor Output
Sensory input
is provided by millions of sensory receptors that monitor changes /stimuli/ taking place inside and outside the body.
Processing/Integration Center
analyzes, stores, and collated sensory input and makes decisions about what actions should be taken.
Motor Output activates effectors
which are usually muscles or glands, that results in a response to the stimuli.
sensory input
1. SEEING A CHARGING ELEPHANT
processing and integration
MEANS DANGER
motor output
SO THE LEG MUSCLES ARE ACTIVATED TO EFFECT AN ESCAPE
Divisions of the Nervous System
a. Central Nervous System(CNS)
b. Peripheral Nervous System(PNS
Central Nervous System(CNS)
fulfills the function of processing and integration

Composed of :
i. Brain
ii. Spinal Cord
Peripheral Nervous System(PNS)
cable like nerves that are made of bundles of 2 types of neurons that may be CRANIAL NERVES and / or SPINAL NERVES:
i. Sensory neurons or Afferent Nerves
ii. Motor neurons or Efferent Nerves
Sensory neurons or Afferent Nerves
carry input from receptors to the CNS
Sensory neurons or Afferent Nerves
carry input from receptors to the CNS
a. Somatic
b. Visceral
Somatic
from skeletal muscles
Visceral
from cardiac, smooth muscle and glands
Motor neurons or Efferent Nerves
transmit motor output from the CNS to muscles and glands.
a. Somatic motor neurons are voluntary
b. Autonomic motor neurons are involuntary
Somatic motor neurons are voluntary
carry signals to skeletal muscles to make them move
Autonomic motor neurons are involuntary
control involuntary activities such as breathing rate, digestion, by activating glands, smooth muscle, and other organs.
i. Sympathetic
ii. parasympathetic
Sympathetic
excitatory
parasymlpathetic
inhibitory
Histology OF NERVOUS SYSTEM TISSUE / CELLS INVOLVED
A. Neuroglia
B. Cells found in the PNS:
Neuroglia
->nerve glue of the CNS
Neuroglia
->nerve glue of the CNS
Neurogla Function:
to support, protect and insulate neurons
Neuroglia
1. Astrocyte
2. Microgla
3. Ependymal
4. Olgodendocyte
Astrocyte
=star shaped; anchor neurons to capillaries
Microglia
=ovoid with long processes; macrophage activity
Ependymal
=ciliated; produce cerebral spinal fluid
Oligodendrocyte
=produce myelin for the CNS
Myelin
=protects neurons and causes rapid nerve impulses
Cells found in PNS
1. Schwann
2.Satelite
Schwann cells
=produce myelin for the PNS
satelite cells
=controls chemical environment of neurons
Neurons
=highly specialized nerve cells which carry electrical impulses to, from, and within the CNS.
Neurons characteristics
1. Extreme longevity, can live for 100years or more
2. Amitotic, do not divide
3. High metabolic rate, need a lot of oxygen and glucose
cell body
Cell Body, the following are found within the cell body

a. Nucleus with no centrioles
b. Ribosomes that are very active
c. Nissl Bodies=another name for the rough endoplasmic reticulum
d. Neurofibrils=intracellular transport
neuron processes
=cytoplasmic extensions of the cell body
a. Dendrites=
b. Axon
Dendrites
=conduct impulses towards the cell body
Axon
=conduct impulses away from the cell body
Classification of Neurons:
1. Structure
2. Function:
Structure of Neurons p.435
a. Multipolar
b. Bipolar
c. Unipolar
Multipolar
=more than one structure coming off of the cell body
bipolar cells
only two structures coming off of the cell body
unipolar neuron
only one structure, that usually bifurcates/divides into two structures later on, coming off the cell body.
Function of Neurons
a. Sensory
b. Motor
c. Mixed
Sensory
info from sensory receptors to CNS
motor neurons
info away form CNS to Effectors
What are stimuli?
Things that put our nervous system into action!
1. Temperature Receptors
2. Mechanical Receptors
3. Photo Receptors
4. Chemo Receptors
5. Nociceptors
temperature receptors
=sense temperature
mechanical receptors
=sense pressure, touch, movement
Photo receptors
=sense light
Chemo receptors
=sense the chemical environment in and outside our body
Nociceptors
=sense pain
NEUROPHYSIOLOGY
=One of the above stimuli will trigger a change in the membrane of a neuron. OR simply stimulation of a neuron.

1. A resting neuron is said to be POLARIZED. In this resting state there
is more sodium, Na, outside the cell than inside, and there is more potassium, K, inside than outside.

2. Then, the neuron encounters one or more of the 5 stimuli listed above!

3. The neuron is then said to be active and DEPOLARIZED. In this active state, sodium is actively pumped in and potassium is actively pumped out. Actively meaning that this takes ATP! So now there is more potassium on the outside of the cell membrane and more sodium on the inside of the cell membrane.
Synapse
=where two or more neurons come into close contact; they do not touch, but are separated at junctions called synapses.

When a neuron is stimulated a wave of electrical disturbance, nerve impulse, sweeps along at 300ft/sec. At the end/presynaptic terminal of the axon of the neuron is a swelling/synaptic knobs. When the impulse arrives here, it causes the release of neurotransmitter. It is here that a recipient nerve may be stimulated because its dendrites are in "contact" with that neurotransmitter and a nerve impulse is generated in this second nerve.