THE NEUROLOGIC SYSTEM
Two Divisions of Nervous System
 Central Nervous System (CNS)
 Peripheral Nervous System
 Somatic Nervous System
– Voluntary
 Autonomic Nervous System
Involuntary.. Responses to the internal responses, like going to the bathroom, divided into the two below
 Sympathetic Nervous
 Parasympathetic Nervous
 Efferent goes from CNS Toward the skeletal system.. Know the difference between the afferent and the efferent.. The
major nervous system
NEURON
• The functional unit of CNS tissue
• Parts: Cell body (soma)
•
dendrites; the extensions that vary the impulses into the cell body,
• axon; carry away from cell body..
• Axon hilloc. ..
The flow of information goes from dendrite, to soma, to axon, to the terminal button, then the synapse.. Impulses
are carried away from the cell body.. The conduction the depends on the size of the neuron
Three Types Neurons:
• Sensory neurons (afferent); in fingere tips, carry toward the CNS; brain and spinal cord
• Motor neurons (efferent); Carry impulses from CNS to site of stimulation
• Interneurons (intrinsic)Carry impulses from neuron to neuron; Sometimes carry impulses straight to motor neuron and
bypass brain.. Ex burning hand
MECHANISMS OF SIGNALING
• Neurons generate and conduct electrical and chemical impulses by releasing chemicals called neurotransmitters
• All-or-none response; resting membrane potential. Has to reach threshold
• Synapse; a region between neuron. The area were the signal is received is called the terminal button
• With inhibition you would have constant excitation…
NEUROTRANSMITTERS
• Acetylcholine; important in Alzheimer’s
• Norepinephrine, important for mood regulation and arousal
• Dopamine; used in Parkinson's disease
• Serotonin; involved in mood; depression mood, anxiety, decreased levels in schizophrenic.
• Many others
NERVOUS SYSTEM CELLS
• Two distinct classes
– Nerve cells or Neurons
– Neuroglial cells (CNS) and Schwann (PNS)
Provide structional support
• Mature nerve cells do not divide
• Nerve regeneration depends on: location of injury, type of injury, inflammatory responses and scarring
Repair of Peripheral nerves
 CNS nerves don regenerate
 Peripheral; have a better chance at regenerating the more further down the injury if undamaged , only applies to
myalinated fibers in the peripheral
GLIAL/SCHWANN CELLS:
• Don’t process info, they support and feed neurons
• 10 – 50 times more abundant than neurons
• One tenth the size of neurons
• Roles of support, protection, and provide nutrition to CNS/PNS
• The closer the injury to the cell body the more damaged the cell is.. crushed is repaired better than cut
CENTRAL NERVOUS SYSTEM
•
•
The body’s control center
The CNS consists of:
– The Brain
– The Spinal cord
– Enables a person to reason and function intelligently
– Memory, thinking , breathing, digestion, and elimination
CNS Protected by:
• Skull/Cranium…foramen, alows nerves to enter and exit the skull
• Vertebrae
• Cerebral Spinal fluid (CSF)
– Proteins glucose mineral and water… mainly for protection…
– Clear, colorless fluid similar to blood plasma
– Provides protection to intracranial and spinal cord structures
– Comes from blood , and continuously being reabsorbed and consumed
– 125-150 ml CSF float within ventricles and subarachnoid space
– Body produces ~600ml/day
• 3 membranes and there spaces (meninges)
 Epidural space: space between skull and dura mater, outside of dura mater..
– Dura mater: consists of two tough fibrous layers (outermost layer)
 Subdural space: space between dura mater and arachnoid membrane; most of injuries occurs here
– Arachnoid membrane: is a very thin fibrous layer (middle layer)
 Subarachnoid space: space between arachnoid membrane and pia mater (contains CSF) most serious, you don’t
want blood in the CSF
– Pia mater: continuous layer of connective tissue (surrounds the brain)
BRAIN:
• Cerebrum;
– Largest part of brain
– Controls sensory and motor activities and intelligence
– Two halves held together by corpus collosum (hemispheres)
– Dominance on left side of brain, right handed
– Non dominant side, resp for geometric musical function, visual pattern
– Outer and inner layer
– The cerebral cortex is the gray matter.. Because it has all the cells body’s of the neurons,
–
innerlayer– beneath the cortex
– Has 4 lobes and other parts
1. Frontal lobe- personality
 Voluntary muscle movement
 Speech (Broca’s area) expressive controls motor aspect of speech. Know what they want to say , but cant
get it out..
 Intellect, judgment, memory, problem solving, (higher executive function)
 Emotion
 Short-term or recall memory
2. Temporal lobe
 Taste
 Hearing mailnty
 Smell
 Interpretation of spoken language (Wernicke) damage to this is receptive aphasia. Thy understand
 Long-term memory
3. Parietal lobe
major area for symatic sensory input
 Coordinates and interprets sensory information from opposite sides of body
4. Occipital lobe
 Vision
 Thalamus; relay center of cerebrum, primitive emotional responses, distinguish pleasant vs. unpleasant
stimuli, and fear
 Hypothalamus; body temperature and endocrine and ANS functions, regulates emotional responses, appetite,
pleasure sensor, maintain homeostasis
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•
•
Cerebellum
– Lies beneath cerebrum at base of brain
– Coordinates and controls reflexive, involuntary motor movement

Posture

Equilibrium
Brain Stem
– Midbrain; form part of the brainstem and connectes it to the rest of the brain
• Reflex center
3rd and 4th cranial nerve
• Contains voluntary and involuntary
auditory and visual reflex centers
– Medulla; Oblongata
• Relay station for crossing motor tracts.
• Controls vital cardiac and respiratory functions
• Reflex activities, like vomiting, coughing, gagging, hiccup..
• Most important, is hart rate, respirations, blood pressure
– Pons
Transmits info from cerebellum to brain stem, and the between the 2 hemispheres
• Reflex center of 5th – 8th cranial nerves
• Chewing, taste, salivation, hearing and equilibrium
Corpus colusum.. Hold the 2 hemisphere of the brain together
RETICULAR ACTIVATING SYSTEM
• Large network of connected tissue nuclei located within the brainstem
• Regulates vital reflexes
– Cardiovascular function
– Respiration
• Maintains wakefulness, and consciousness..\
• Nerves can become over stimulated,, which fatigues it and you cant think as straight.. And it becomes less excitable
BRAIN VASCULATURE
• Formed by many communicating arteries extending to various brain structures
• Receives approximately 15% of the cardiac output/min and 20% OF BODIES O2 sup;ply
• CO2 ensures adequate cerebral blood supply (vasodialaton
• Circle of Willis provides collateral blood flow- bld flow leaves the via the jugular
BLOOD BRAIN BARRIER
• Selectively inhibits certain substances in the blood from entering the interstitial spaces of the brain or CSF
• Supporting cells & tight junctions between endothelial cells are
– Involved in the formation
– Responsible for impermeability
SPINAL CORD
• From the medulla oblongata to the level of the 1st or 2nd lumbar vertebra
• Many functions
– Functions as a two-way conductor pathway between the brain stem and PNS (Motor and sensory tracts)
– Motor and sensory tracts
– Controls body movement
Spinal cord Consists of:
• Vertebrae (33: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral and 4 coccygeal)
• Intervertebral Disks (shocks between vertebrae)
PERIPHERAL NERVOUS SYSTEM
PNS :
• Provides communication between CNS and the remote body
• Includes cranial and spinal nerves
• Consists of afferent (sensory) and efferent (motor) nerve pathways
PNS SUBDIVISIONS
1. Sensory-somatic nervous system:
• regulates voluntary motor control through our conscious awareness of the external environment
• 12 pairs of cranial nerves
• 31 pairs of spinal nerves
• Contains one single neuron that goes from spinal cord to the skeletal muscle
2. Autonomic nervous system:
• regulates body’s internal environment through involuntary control of organ systems
• Sensory neurons/Motor neurons: run between CNS and various internal organs (heart, lungs, glands)
• Contains two neurons that go from spinal cord to the target tissue (preganglionic neurons and postganglionic
neurons)
• Devided by a gangleon,,, there shoter
Two Subdivisions ANS:
1. Sympathetic nervous system: “fight or flight response”
• Nerves exit from 1st thoracic region to the 2nd lumbar region of the spinal cord
• Increased activation during stressful events
• Preganglionic neurons (short) release Ach which stimulates an action potential in the postganglionic neurons (long)
that release NE to trigger a response in the target organ
2. Parasympathetic nervous system: “rest and relax response”
• Arises from the craniosacral segments of the spinal cord
• Responsible for conservation of energy & restoration of routine body function
• Acetylcholine is released from every preganglionic neuron (long) and most postganglionic neurons (short)