the nervous system
major control center, communication network, sense change
two main divisions
CNS, PNS
central nervous system (CNS)
brain and spinal cord
- command center
- interprets signals
- outputs info
peripheral nervous system (PNS)
nerves that extend from the CNS
- gathers info from inside and outside your body
- made up of nerves that extend from the brain and spinal cord
how the nervous system works
messages are transmitted through electrical impulses or charges
neurons
the basic building block of the nervous system. These are messengers and receivers of transmissions or stimuli
cell body
consists of a nucleus that receives and sends nerve impulses: the nucleus is contained within the cell membrane
dendrites
branching projections of the cell body: they receive and carry impulses toward the cell body
axon
branching projections of the cell body: they receive and carry impulses away the cell body
myelin sheath
insulates the nerve fiber which speeds up the transmission
sensory neurons
have specialized receptor ends that are located in the skin and other sensory organs
motor neurons
carry impulses from the CNS to the muscles and glands
interneurons
neurons within the brain and spinal cord that relays impulses from sensoring neurons
spinal cord
cylinder of nerve tissue, protects the vertebrae, protected by cerebrospinal fluid which acts like shock absorber & by 3 layers of connective membranes called the spinal meninges
brain
-receives and processes messages
-coordinates muscle movement
- weighs 3 lbs, makes up 2% of body weight
- uses 20% oxygen inhaled
- 20% of blood pumped through heart
protection of brain
protected by the 8 cranial bones that firm the skull and by three layers of membranes called cranial meninges
main divisions of the brain
Cerebrum, Cerebellum, Brain Stem
cerebrum
-largest & most complex part of the brain
- Site of most conscious & intelligent
activities
- divided into 2 halves called cerebral hemisphere
left hemisphere
-language
-logic
- arithmetic calc.
- analysis
- critical thinking
right hemisphere
-imagination
- visual thinking
- form
- artistic activities
- emotions
Frontal Lobe
controls voluntary movement and has a role in language
Parietal Lobe
sensory information
Temporal Lobe
senses of hearing & smell, along with memory, thought, & judgment
Cerebellum
- 2nd largest part part of the brain
- located beneath the the occipital lobes of the cerebrum
- main purpose- maintaining posture and balance, coordinating skeletal muscle movement
brain stem
3" long stalk of nerve cells and fibers that connects the spinal cord to the rest of the brain. controls breathing, heartbeat, eye reflexes.
3 main parts of brain stem
-Medulla Oblongata
- Pons
- Midbrain
Medulla oblongata
lowest part of the brain stem Contains vital control centers that regulate:
heartbeat
breathing
blood pressure
digestion
pons
just above the medulla, serves as a pathway for nerve impulses passing to and from the cerebrum
mid brain
shortest part of the brain stem, lies above the pons, controls eye movement- the size and reactions of the pupils
Thalamus
2 egged shaped loves above the midbrain, important relay center for incoming, sensory impulses
Hypothalamus
located behind the eyes and under the thalamus, controls various body processes & keeps body conditions balanced (body temp, appetite)
The PNS is broken down into two subdivisions
- autonomic nervous system
- somatic nervous system
Autonomic Nervous System
Responsible for controlling the involuntary functions of the body, such as body heat, heart rate, and digestion.
The ANS is further divided into
- sympathetic nervous system
- parasympathetic nervous system
Sympathetic Nervous System
Responds to the body's needs during increased activities and in emergencies
Parasympathetic Nervous System
opposes the actions of the sympathetic system by slowing body functions
slows down heartbeat
opens blood vessels
lowers blood pressure