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The Nervous System Part 1-4 Notes

Terms in this set (70)

The Nervous System
- consists of the brain, spinal cord, nerves, and sensory receptors
- it controls all body actions
- it receives and monitors all information (stimuli) from inside and outside the body
- it processes and interprets this information (sensory input) and makes decisions about what should be done at each moment which is a process called interrogation
- nerve impulses (and hormones) send information to body structures, increasing or decreasing their activity
- it is the master of communication and control system of the body
Anatomy of the Nervous System
- Central nervous system
- Peripheral nervous system
- autonomic nervous system
- somatic nervous system
central nervous system
- includes the brain and spinal cord
- directs the activity of the entire nervous system
- damage to the brain or spinal cord can be life threatening
peripheral nervous system
- includes all nerves outside the brain and spinal cord
- also includes specialized nerve endings called sensory receptors, which respond to stimuli such as pain, pressure, touch and temperature
automatic nervous system
- a division of the peripheral nervous system
- regulates body's involuntary or automatic functions such as ... the heart, smooth muscle, and glands
- Two parts: sympathetic and parasympathetic
The somatic nervous system
- a second division of the peripheral nervous system
- sends efferent (motor) impulses to activate the skeletal (voluntary) muscles
Types of Neurons
afferent, efferent, interneurons
afferent neurons (sensory)
transmit impulses from all parts of the body to the spinal cord and brain, providing information about external and internal environments
efferent neurons (motor)
transmit impulses away from the brain and spinal cord to muscle and granular tissue, directing body actions
interneurons (central neurons)
conduct impulses from sensory to motor neurons
Nervous tissue
neurons and neuroglia
Neurons
- specialized cells that transmit messages (impulses) from one part of the body to another
- the nervous system is made up of billions of nerve cells
- there are over 100 billion nerve cells in the brain alone
- axons (the branched ends of neurons) do not actually touch other neurons or muscle the gap is called a synapse
Axon
the branch end of neurons
synapse
the gap between a axon and other neurons or muscle
neuroglia
- do not transmit impulses; rather, they support neurons
- Four types:
1. astrocytes
2. microglia
3. ependymal cells
4. oligodendrocytes
astrocytes
link nutrients supplying capillaries to neurons; protect neurons from harmful substances in blood
microglia
absorb and dispose of dead cells and pathogens
ependymal cells
form protective covering around the spinal cord and central cavities of brain
oligodendrocytes
wrap nerve fibers and produce an insulating material called myelin
reflexes
- rapid, predictable, programmed, involuntary responses to stimuli
- they occur over neural pathways called reflex arcs
Types of reflexes
somatic and autonomic
Somatic
reflexes that stimulate the skeletal muscles

Examples: pulling your hand away from a flame

- sensory neuron stimulates a motor neuron, by way of an interneuron in the spinal cord
- the signal travels incredibly fast because it did not have to travel to the brain and back
autonomic
reflexes that send involuntary stimuli to the cardiac muscle of the heart and the smooth muscles of internal organs

examples: secretion of saliva, changes in the size of pupils, digestion, elimination, and blood pressure
elements of a reflex arc
- sensory receptor
- sensory afferent neuron
- central element
- motor efferent neuron
- effector organ
sensory receptors
reacts to a stimulus
sensory afferent neuron
carries message
central element
the synapse between the sensory and motor neurons
motor efferent neuron
carries response
effector neuron
muscle or gland eventually stimulated as a response to the stimulus
brainstem
- oldest most primitive part of our brain, we share it with reptiles and other mammals
- controls all automatic functions that keep us alive
structures of the brainstem
- midbrain
- pons
- medulla oblongata
midbrain
a relay station for sensory and motor impulses: information concerning vision, hearing, sleep and wake cycles, motor activity, alertness, and temperature regulation
pons
helps regulate breathing
medulla oblongata
regulates heart rate, blood pressure, and breathing; controls reflexes for vomiting, coughing, and sneezing
diencephalon
located between the brainstem and cerebral hemisphere

made up of the:
1. thalamus
2.hypothalamus
3. epithalamus
thalamus
regulates body's states of alertness including sleep, wakefulness, and high-alert consciousness
hypothalamus
regulates metabolism, heart rate, blood pressure, thirst, hunger, and body temperature. contains centers for sex, pain and pleasure
epithalamus
includes the pineal gland and helps regulate the sleep cycle hormone it releases: melatonin
cerebellum
- latin for "little brain"
- refines and coordinates muscle movement; body movements are smooth and synchronized
- receives information from the equilibrium apparatus of the inner ear, eyes, and sensory receptors of skeletal muscles and tendons
- aids in balance and equilibrium
cerebrum
- largest and most obvious part of the brain, divide into cerebral hemispheres
- the learning center
- it separates us from all other animals (we are smarter)
cerebral cortex
outer surface of the cerebrum, made up of non-myelinated gray matter (internal tissue is myelinated white matter)
Gyri
curved "hills" of cerebrum
Sulci
grooves between Gyri
divide the brain into four regions called lobes
fissures
the uniformly positioned, deep grooves in the brain
median longitudinal fissure
divides the brain into left and right hemisphere
parts of the cerebrum
cerebral cortex, gyri, sulci, fissures, median longitude fissure
lobes of the cerebrum
frontal, parietal, temporal, occipital
frontal
primary motor area (movement of skeletal muscles), higher intellectually reasoning (thinking) decision making, planning, learning, emotions, speaking (Broca's area), writing and memory
parietal
sensory area (pain, touch, temperature ect.) determining shapes, sizes, distance of objects, forming words from letters, and forming thoughts from words
temporal
hearing, smell, emotions, interpretation of speech, interpreting language, memory
occipital
informal related to vision
The Autonomic Nervous System
- the motor subdivision of the PNS that controls body activity automatically
- made up of a specialized group of neurons that regulate: cardiac muscle, smooth muscle found in walls of visceral organs and blood vessels, and glands
- Although all organ systems contribute to homeostasis, the stability of our internal environment deepens largely on the workings of the ANS
At any given moment the autonomic nervous system can...
- blood flow may be shunted from one area to make "needy" areas
- heart and breathing rates may be increased or decreased
- blood pressure may be adjusted
- stomach secretions may be increased or decreased
- our pupils may constrict or dilate
at every moment ( the autonomic nervous system)
signals from body organs flood the CNS, and the autonomic nerves make the necessary adjustments to best support body activities (most of the fine-tuning occurs without us even knowing)
ANS
involuntary nervous system
divisions of autonomic nervous system
sympathetic and parasympathetic
similarities between sympathetic and parasympathetic
- both serve the same organs but cause essentially the opposite effects
- they counteract each other's activities to keep up the body systems running smoothly
the sympathetic division
- often referred to as the "fight-o-flight" system
- its activity is evident when we are excited or are in threatening or stressful situations
- a pounding heart, rapid deep breathing, cold sweaty skin, a prickly scalp, and dilated pupils are sure signs of sympathetic nervous system activity
- the sympathetic nervous system works at full speed when you are physically stressed as well as emotionally stressed
- during these times, the adrenal glands pump out two hormones, epinephrine (adrenaline) and norepinephrine (noradrenaline) to stimulate action of organs
the parasympathetic division
- most active when body is at rest and not threatened
- sometimes called the "resting-and-digesting" system
- chiefly concerned with promoting normal digestion, eliminating feces and urine, and conserving body energy (mostly by decreasing demands on the cardiovascular system)
examples of parasympathetic nervous system
- blood pressure and heart and breathing rates are kept at low normal levels
- digestive tract actively digests food
- skin is warm
- pupils are constricted to protect retinas
- the parasympathetic division is the "housekeeping" system of the body
Final thoughts on the ANS
- the sympathetic and parasympathetic divisions rarely operate in an "all-or-none" fashion
- both continually make fine adjustments, maintaining ad dynamic balance
protection of the central nervous system
- nervous tissue is very soft and delicate, irreplaceable neurons are injured by even the slightest pressure
What is one awesome way nature protects the brain and spinal cord?
cranial/ skull and vertebral column/ spinal cord
meninges
the three connective tissue membranes covering and protecting the CNS structures
Dura Mater ("tough mother")
a double layered membrane beneath the cranium that surrounds the brain
Arachnoid Mater ("Weblike mother")
has a cob-web-like appearance beneath it is a cushioning fluid
Pia Mater ("gentle mother")
a delicate membrane that clings tightly to the surface of the brain
cerebrospinal fluid (CSF)
surrounds the brain and spinal cord and acts as a shock absorber
hydrocephalus ("water on the brain")
the accumulation of CSF, which exerts pressure on the brain. More serious in adults then children.
concussion
- a traumatic brain injury caused by a blow to the head, a fall, or other injury that shakes the brain inside the skull
- normally, your soft brain is protected by CSF, which cushions the brain and prevents it from banging into your skull
- if the head is hit hard, the brain can crash into the skull and be injured
- most concussions are mild
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