PTI BLOCK 1: Nervous System B1L5

Types of Neurons (SAME)

(Sensory) Afferent - information carried towards the brain (Motor) Efferent - information carried away from the brain

Abnormal Respiratory Patterns

- Biots (rapid/deep with short pauses) - Cheyne-Stokes (gradual increases and decreases in respirations w/ pauses) Biot Causes: meningitis/head/CNS injury Cheyne. Causes: increase ICP/brainstem injury

parasympathetic nervous system responsibilities (recovery)

- Digestion - growth - healing - slow heart rate - decrease blood flow

Blood supply to and from the Brain

- Primary arterial supply to the brain = carotid arteries - primary venous return from the brain = jugular veins

What happens if the brainstem gets injured?

- become altered - vomit (increase ICP) - pupils dilate - pulse pressure widens - Decerebrate or decorticate posture - breathe abnormally - HR slows (brady) - systolic BP goes up

parasympathetic nervous system (body at rest)

- constricts pupils - heart beats more slowly - constricts airway - stimulates digestion - reduces blood flow to skeletal muscles

sympathetic nervous system (Fight or flight)

- dilates pupils - heart beats faster and stronger - relaxes airway, which lets you breathe more deeply - inhibits digestion - increases blood flow to skeletal muscles

Neuron Structure

1. Body (soma- contains nucleus) 2. Dendrites (branch like projections) 3. Axon (long tail projection) 4. Myelin (white matter- tissue around axon for protection and transfer impulses faster) 5. Axon terminal

Divisions of the Nervous System

1. CNS: (brain/spine: responsible for thoughts/perception/sensory/autonomic body functions) 2. PNS: (somatic/autonomic) Somatic: sensory + motor Autonomic breaks down to sympathetic (fight flight) and parasympathetic (rest digest)

Anatomy of Brain (4 areas)

1. Cerebrum 2. Diencephalon 3. Brainstem 4. Cerebellum

Main Functions of Nervous System

1. Monitor internal/external environment 2. Integrate sensory info 3. coordination of voluntary/involuntary response

Neuron Characteristics

1. sensitive to changes (O2/glucose) 2. high metabolic rate (uses O2/glucose in 10 sec) 3. neurons cannot store O2/glucose 4. does not require insulin 5. Neurons do not regenerate 6. capable of excitability and conductivity

Cranial Nerves (CN)

12 pairs of cranial nerves that arise from the base of the brain (4 of these nerves are associated with the parasymp system) Important CNs include: CN3- oculomotor nerve CN10- vagus nerve

Cerebrum Hemispheres

2 Hemispheres divided by white matter band called CORPUS CALLOSUM along the LONGITUDINAL FISSURE Each hemisphere controls the opposite side of the body

Peripheral Nervous System

31 pairs of spinal nerves and 12 pairs of cranial nerves Responsible for communication between CNS and rest of body 2 Divisions: Somatic & Visceral

Parasympathetic Neurotransmitter

Acetylcholine (causes resting HR/digest food)

How to check damage in spinal column

Ask Pt to wiggle fingers and toes

Spinal Nerves

Attaches to the spinal cord by two roots: posterior (dorsal) and anterior (ventral) Posterior: afferent sensory fibers Anterior: efferent moter fibers

Nervous System Receptors

Baroreceptors (detect changes in pressure) Chemoreceptors (changes in chemistries)

Phrenic Nerve

C3,4,5 (keeps the diaphragm alive)

Vagus Nerve

CN10: longest cranial nerve responsible for swallowing, gag reflex, parasympathetic innervation (90% of PNS) of the body Big 4 Nerve controls: 1. Chronotropy (HR rate) 2. Inotropy (contraction strength) 3. Conductility (AV conduction) 4. Irritability

Oculomotor Nerve

CN3: responsible for eye movement, upper eyelids, and regulation of pupil size Stimulation causes pupillary constriction Increased ICP causes pupillary dilation

Cerebral Perfusion Pressure

CPP = MAP - ICP Amount of perfusion the brain is receiving Can improve brain perfusion in field by increasing the MAP and decreasing ICP (reverse trendelenberg, prevent vomitting) MAP you want at least at 60, normal 80 Other factors interfereing with CPP: CO2 and Hypotension

Microglial Cells (CNS)

Clean up crew of the CNS/eat up bacteria and cell waste

Sympathetic System Adrenergic Receptors

Comes from the Catecholine- norepinephrine Alpha 1: vasoconstriction Alpha 2: smooth muscle contraction Beta 1: Found in the heart, increases HR Beta 2: Found in lungs, bronchial dilation

Central Nervous System

Composed of brain and spinal cord coordinates sensory information and motor responses Fragile- protected by bone, meninges, CSF, and blood brain barrier (filtration system) Spinal cord protected by vertebral column

Spinal Cord

Connects brain to the rest of the body via the spinal nerves Exits the skull through the foramen magnum and extends through the column

Brain Stem

Connects brain to the spinal cord responsible for essential functions body requires to survive contains specialized group of neurons called RETICULAR ACTIVATING SYSTEM (RAS) Stem is composed of: 1. midbrain 2. pons 3. medulla oblongata

Reticular Activating System (RAS)

Controls the level of consciousness responsible for specific motor movements Injury to area will produce ALOC

Meninges (3 layers)

Covering over the brain and spinal cord 1. Dura Mater (outermost - durable) 2. Arachnoid (middle) 3. Pia Mater (innermost)

Pia Mater

Delicate innermost layer lies directly over CNS and follows the contours of the brain + spinal Where meningitis occurs (inflammation of meninges)

Sympathetic Neurotransmitters

Epi/NorEpi/Dopamine (causes increased HR, vasoconstriction, contractility) Note these are catecholamines

Ependymal Cells (CNS)

Found in CNS Line the fluid filled cavities of the brain called ventricles Function: secrete and circulate CSF

Satellite cells (PNS)

Found in PNS Similar to astrocytes in CNS (feeder cells)

Astrocytes (CNS)

Found in the CNS (type of neuroglia) Provide nourishment to neurons recycles neurotransmitters

Occipital Lobe

Function: - origin of optic nerve - process visual info - color vision/spatial perception Dysfunction: - visual disturbances - visual field distances/blurred vision

Parietal Lobe

Function: - primary sensory cortex - sensory interpretation - process info - determine shapes/distances - process math/speech - body position (proprioception) Dysfunction: - abnormal sensory response - paresthesia

Neuron

Functioning unit of nervous system

Frontal Lobe

Functions: - higher cognitive function - voluntary motor function - memory - personality/emotion Dysfunction: - short term memory loss - personality changes - expressive aphasia (cant form sentences AKA brocas aphasia)

Temporal Lobe

Functions: - primary auditory cortex - process/perceives memories/sensations - speech comprehension Dysfunction: - hearing problem - warnakes area (receptive aphasia aka difficulty understanding) - long term memory loss

Medulla Oblongata

Inferior part of brainstem contains vital centers: 1. Cardiac center 2. vasomotor center 3. Respiratory center

Cerebrum

Largest part of the brain (3/4 its volume) Responsible for higher mental function/memory/reason Folded grey matter known as the cerebral cortex Divided into 4 lobes: 1. Frontal 2. Temporal 3. Parietal 4. Occipital

Pons

Middle portion of brainstem relay both afferent and efferent nerve fibers contains sleep and respiratory centers (controls breathing along with medulla)

Midbrain

Most superior portion of brainstem Reflex center for pupillary reflexes and eye movement Coordination of motor activity and muscle tone

Spinal Cord Injury: at or above T5

Neurogenic shock

Oligodendrocytes/Schwann cells

Oligo: found in the CNS, forms myelin sheaths around axons within brain/spine Schawnn: found in PNS, form myelin sheaths around axons in PNS

Autonomic Nervous System

Part of the PNS, breaks down into two main branches: 1. Sympathetic (fight or flight) 2. Parasympathetic (rest digest) Most structures are innervated by both symp and parasymp fibers except for the spleen and blood vessels which are only controlled by sympathetic fibers

Hypothalamus

Regulation of body temp, hunger, thirst, sleep, and sex development Regulates involuntary body function (cardiac/smooth musc.) Functions w/ endocrine system Vomiting reflex **in an infant, the hypothalamus is less effective in regulating body temp (infants dont shiver)**

Interneurons

Relay neurons that carry impulses from sensory to motor neurons (located in spine to prevent signal from going all the way to the brain and back)

Cerebellum

Second largest part of the brain (inferior to the occipital lobes) involved in fine/gross motor movement maintenance of equilibrium/balance

Arachnoid Mater

Second meningeal layer, very thin, delicate, web-like

Blood Brain Barrier

Semi-permeable protects brain from foreign substances + hormones Maintains a constant environment permitted molecules can pass through via diffusion or active transport - water/glucose pass easily - O2/CO2/alcohol diffuse easily

Neuroglia

Supporting cells of the nervous system Function: support structure, improve conduction, defend from pathogens, air in repair, regulate fluids

Dura Mater

Toughest/thickest layer. Made up of two layers parietal (closer to bone/outer) & visceral (closer to brain/inner) Bleeds below dura but before arachnoid are called sub dural (common)

Chemoreceptors

Two types: Central & Peripheral

Neurotransmitters are...

a chemical released from one nerve that crosses the synaptic cleft to reach a receptor on the next cell

Neurotransmitters

chemical messengers used to transmit signals (may excite or inhibit a response) Electrical synapses occur between cardiac muscle cells and smooth muscle cells

Cerebral Spinal fluid (CSF)

clear, watery fluid produced by choroid plexus in all 4 ventricles (155cc total volume in adults) - provides protection - delivers nutrients - eliminates wastes - homeostasis

Cerebellum Dysfunction

common cause of dysfunction: Alcohol and drugs/tumors/poor perfunsion/trauma/ hypoxia S/S of dysfunction: - ataxic gait - dysarthria - nystagmus

Vasomotor Center

controls smooth muscle tone of blood vessels Vasoconstriction: increased peripheral vascular resistance Vasodilation: Decreased peripheral vascular resistance

Action Potential

electrical impulse the cell use to create an effect

Diencephalon

located above the brainstem and between the two hemispheres Composed of: 1. epithalamus 2. thalamus 3. hypothalamus

Central Chemoreceptor

located in brainstem responds to CO2 levels in the CSF. Increased CO2 leads to increased RR and tidal volume (sometimes non functional in COPD)

Peripheral Chemoreceptor

located in the carotids and aorta responds to low O2 levels (hypoxic drive)

Repolarization

occurs with the turning on of the Na+/K+ pump (3 Na+ gets pumped out, and 2 K+ move into the cell)

Sympathetic and Parasympathetic systems have...

opposing effects on muscles

Spinal Cord Injury: At or below C7

paraplegia

Synapse

place where neurons connect and communicate (chemical and electrical synapse)

Baroreceptors

pressure sensitive cells located in the aortic arch and carotid sinus and kidneys measure the stretch in great vessels (that changes the BP) Info is then sent to vasomotor center and medulla Valsalva is the artificial stimulation of the baroreceptors resulting in vagal stimulation (drops BP/HR)

Spinal Cord Injury: Above C7

quadriplegia

Spinal Cord Injury: Above C5

respiratory impairment

Subarachnoid Space

space between arachnoid mater and the pia mater Very vascular and has network of veins/arteries (all vessels that feed to the brain)

Depolarization

stimulus causes Na+ channels to open, NA+ rushes in, making neuron more positive

Resting potential

the electrical charge at which a cell is in a resting state, the cell will have a negative charge (greater concentration of extracellular Na+ and intracellular K+; but negatively charged Cl- ion inside the cell makes cell more negative)