SHS 300 - Nervous System

organization of the nervous system

central nervous system:

• brain

• spinal cord

peripheral nervous system:

• cranial nerves

• spinal nerves

subdivisions of the PNS:

• somatic

• autonomic

  • sympathetic division

  • parasympathetic division

3 main functions of the nervous system

• gather sensory information (through the PNS)

• synthesize information (in the CNS)

• respond to stimuli (CNS sends to PNS)

white matter

bundle of myelinated axons

gray matter

cluster of cell bodies

nuclei

cluster of cell bodes in the CNS

tract

bundle of axons in the CNS

nerves

bundle of axons in the PNS

ganglia

cluster of cell bodies in the PNS

afferent pathways

sensory input

efferent pathways

motor output

neurons

definition: specialized cells that transmit electrochemical signals

respond to stimuli by processing and conducting impulses to other neurons and cells (communication between parts)

macroglia (type of glial cell)

Oligodendrocyte and Schwann Cell:

• Oligodendrocyte - found only in the CNS

• Schwann Cell - found only in the PNS

• both produce myelin and surround the axon to provide the axon with it

Astrocyte:

• scaffolding: connects to the neuron and promotes neuronal migration (when A moves, N moves too)

• neuronal survival: connects the neurons to blood vessels, where the neurons will receive the nutrients they need to survive

• synapse: determines how many synapses a neuron can have

• formation of the blood-brain barrier

• maintains neuronal homeostasis (e.g., extracellular fluid, energy, etc)

microglia (type of glial cell)

• “immune cells” of the CNS —> release cytokines in response to injury; remove debris

• neuronal support —> programmed cell death for malformed neurons, etc

• homeostasis

• disease processes —> releases debris/harmful substances in small amounts to help the brain in developing an immune response (can release too much, which results in inflammation and neurodegeneration)

labeled neuron

see image

synaptic process

• synaptic vesicles located in the presynaptic membrane house neurotransmitters

• when triggered by an action potential, the neurotransmitters are released and bind to receptors in the post-synaptic membrane

• the type of receptor on the post-synaptic membrane will dictate which ions enter —> results in either an excitatory effect (+ ion) or inhibitory effect (- ion)

action potential

• a neuron is stimulated:

  • strong enough: threshold is met (-55mV) and there will be a large and fast influx of Na+ ions that results in depolarization (+40mV)

  • NOT strong enough: some depolarization but does not meet the threshold (failed initiations)

• at the peak of the action potential (+55mV), K+-gated channels open which results in an outflux of K+ = repolarization

• outflux of K+ and closing of Na+-gated channels causes the neuron’s potential to be more negative than the threshold (refractory period)

• neuron eventually returns to its resting state (-70mV)

organization of the central nervous system

brain:

• cerebrum (cortex)

• cerebellum

• brainstem

  • midbrain

  • pons

  • medulla

spinal cord

name of the fissure that divides the cerebral hemispheres into right and left

longitudinal fissure

function of the corpus callosum

communication point between the left and right hemispheres

frontal lobe - function

motor planning, decision-making, and language production

parietal lobe - function

sensory integration to touch, pressure, and pain

temporal lobe - function

auditory processing and language comprehension

occipital lobe - function

primary visual processing

functions of the insula

• emotions - compassion, empathy, self-awareness

• hunger and thirst

• pain and fatigue

• risk and reward

basal ganglia - identify and function

• motor control of voluntary movements

• cognition: reward, motivation (habit)

thalamus

relays sensory and motor information

hypothalamus

regulates body temperature, hunger/thirst, and circadian rhythm

amygdala

processes emotions, especially fear and aggression

hippocampus

• formation of new memories; consolidation of memories

• spatial navigation

limbic system - structures and functions

overall, the limbic system is involved in emotional processing, motivation, memory, and autonomic processes

• cingulate gyrus - learning

• hippocampus - memories

• amygdala - emotions

• hypothalamus - autonomic

• basal ganglia - motor movement

function of the cerebellum

movement coordination

brainstem - identify and functions

• consciousness

• basic vegetative functions (e.g., breathing, heartbeat)

• houses cranial nerve nuclei (and where cranial nerves exit)

3 layers of tissue protecting the brain (meninges)

dura mater - most superficial layer

arachnoid mater - intermediate layer (CSF)

pia mater - deepest layer

how the arrangement of the Circle of Willis is beneficial to the brain

definition: anterior and posterior circulation come together to form a circular blood supply

if damage to the brain occurs, the other arteries located within it will compensate for the damaged parts (not a permanent solution)

CN I function

olfactory nerve

responsible for the sense of smell

CN II function

optic nerve

responsible for vision

CN III function

oculomotor nerve

responsible for eye movements, pupillary constriction, and innervation of the muscle of the upper eyelid

CN IV function

trochlear nerve

responsible for vertical eye movements

CN V function

trigeminal nerve

responsible for:

• sensation of the face, teeth, gum, and anterior 2/3 of the tongue

• innervating the muscles of the jaw

***important for speech and swallowing

CN VI function

abducens nerve

responsible for lateral eye movement

CN VII function

facial nerve

responsible for:

• taste for anterior 2/3 of tongue

• innervation of the muscles of facial expression; innervation of the salivary glands

***important for speech and swallowing

CN VIII function

vestibulocochlear nerve

responsible for hearing and balance

CN IX function

glossopharyngeal nerve

responsible for:

• sensation of the posterior 1/3 of tongue; taste for posterior 1/3 of tongue

• innervations of the salivary gland (carotid gland)

***important for speech and swallowing

CN X function

vagus nerve

responsible for:

• sensation of the pharynx and larynx

• innervation of the muscles of the vocal folds and swallowing; also involved in autonomic functions (e.g., heart, lungs, etc)

***important for speech and swallowing

CN XI function

accessory nerve

responsible for:

• innervation of the muscles of the shoulders and neck

***important for speech and swallowing

CN XII function

hypoglossal nerve

responsible for the innervation of the muscles of the tongue

***important for speech and swallowing

spinal nerves that form the cervical plexus

C1, C2, C3, C4

spinal nerves that form the phrenic plexus

C3, C4, C5

5 neurological diseases that may affect communication or swallowing

Parkinson’s disease

Amyotrophic lateral sclerosis (ALS)

Huntington’s disease

Multiple sclerosis

Stroke/TBI