Neuroanatomy & Physiology Exam 1

What 2 systems make up the nervous system?

Central Nervous System/CNS & Peripheral Nervous System/PNS

What structures make up the CNS?

Brain: receives and processes sensory info; plans & initiates motor responses; regulates systems; analyzes & stores memory

Spinal Cord: conducts signals to & from the brain; controls certain reflexes

What systems makes up the PNS?

Motor & Sensory Neurons,

Autonomic & Somatic Nervous Systems,

Sympathetic & Parasympathetic Nervous Systems

What is the function of a Motor Neuron?

• Transmits efferent info from the CNS → Muscles & Glands

• Enables movement and bodily action

What is the function of a Sensory Neuron?

• Transmits afferent info from the sensory receptors → CNS

• Allows us to perceive the world around us

What is the function of the Somatic Nervous System?

• Controls voluntary muscle contractions & movements

• Innervates skeletal muscles

What is the function of the Autonomic Nervous System?

• Directs & Regulates subconscious, involuntary functions of the body

• Helps maintain homeostasis (equilibrium)

What is the function of the Sympathetic Nervous System?

“Fight or Flight” = Expends Energy

• Function: Increases cardiovascular & respiratory activity, slows digestive peristalsis, increases blood glucose levels, dilates bronchi in lungs and pupils of eye, and arousal

• Structure: Nerve fibers arise from the thoracic and lumbar spinal cord; innervates organs, glands, and structures of head via cranial nerves

What is the function and structure of the Parasympathetic Nervous System?

“Rest and Digest” = Conserves Energy

• Function: Decreases cardiovascular & respiratory activity, increases digestive peristalsis, decreases blood glucose levels, constrict bronchi in lungs and pupils of eye, and maintains homeostasis

• Structure: Nerve fibers arise from brainstem and sacral spinal cord; innervates organs, glands, and structures of head via cranial nerves

Define Afferent

AKA Sensory Neurons

These nerve cells transmit electrical impulses from sensory receptors (in the skin, organs, eyes, and muscles) toward the CNS

Define Efferent

AKA Motor Neurons

These nerve cells transmit electrical signals away from the CNS to the PNS

What makes up the Cerebrum?

• Outer Layer: Cerebral Cortex & Gray matter

• Inner Layer: White matter

• Left & Right Hemisphere

*Largest and most prominent part of the brain

What structures make up the brainstem?

Medulla Oblongata, Pons, Midbrain

*Controls vegetative functions: respiration, cough & gag reflex, pupillary response, swallow reflex

Where is the Pons located & what is its function?

• Caudal to Midbrain & Rostral to Medulla

• Relay system among spinal cord, cerebellum & cerebrum;
  Controls unconscious motor information for things like balance and precise
  coordination

Where is the Medulla located & what is its function?

• Caudal to Pons

• Sensory and motor messages between cerebrum and spinal cord

• Contains ANS centers for
  • BP
  • HR
  • Respiration
  • Vasoconstriction and dilation
  • Reflex functions: vomiting, coughing, sneezing, swallowing
  
  

What is the little brain and what are its traditional functions?

The Cerebellum is made up of 2 hemispheres, a cerebellar cortex with gray and white matter, and 3 lobes

Traditional Function:

• Proprioception

• Unconsciously adjusts body for coordinated, precise control of movement and balance

Other Functions:

• attention shifting, practice-related learning, spatial
  organization, memory

• timing and fluidity of speech
  
  

  
  
  

Where does the spinal cord begin?

Foramen Magnum

Where does the spinal cord ends?

Conus Medullaris

What is the most caudal tip of the spinal cord called? 

Conus Medullaris

Why is the spinal cord shorter than the vertebral column? 

The bony spine grows much faster and longer than the spinal cord during fetal development

What is Cauda Equina?

A bundle of nerve roots that extend from the bottom of the spinal cord inside the lower back. They are spinal nerves that have not yet exited the vertebral column 

Are the Cervical Spinal Nerves named according to the vertebra they exit above or below?

Are nerves named according to the vertebra they exit ABOVE

Name the Spinal Nerve that does not have a corresponding vertebra

Cervical Spinal Nerve 8

C8 nerve exits between C7 & T1 because there is NO C8 vertebrae

Are the Thoracic Spinal Nerves named according to the vertebra they exit above or below?

Are nerves named according to the vertebra they exit BELOW

Where are the enlargements of the spinal cord?

The Cervical & Lumbar sections of the spinal cord

Why are these areas larger than other areas of the spinal cord?

• The cervical enlargement is due to the brachial plexus, a network of spinal nerves from C5 to T1 that extend from the cervical vertebrae to the upper extremities

• The lumbar enlargement is due to the lumbar plexus, a network of spinal nerves from L1 to S3 that extend from the lumbar vertebrae to the lower extremities

What are the functions of the Cranial Nerves?

• carry sensory information

• carry motor commands

• Or they carry both sensory and motor
  information

Name the 12 Cranial Nerves

1. Olfactory

2. Optic

3. Oculomotor

4. Trochlear

5. Trigeminal

6. Abducens

7. Facial

8. Vestibulocochlear

9. Glossopharyngeal

10. Vagus

11. Accessory

12. Hypoglossal

Which nerves are considered only sensory?

Olfactory, Optic, & Vestibulocochlear (I, II, VIII)

Which nerves are considered only motor?

Oculomotor, Trochlear, Abducens, Accessory, Hypoglossal (III, IV, VI, XI, XII)

Which nerves are both sensory and motor?

Trigeminal, Facial, Glossopharyngeal, Vagus (V, VII, IX, X)

What are the functions of the Olfactory Nerve?

• Carries the sense of smell from the nasal cavity to the brain.

• Lesion: Anosmia – lack of sense of smell; often caused by head injury.

What are the functions of the Optic Nerve?

• Transmits visual information from the retina to the brain

• Responsible for visual acuity

• Forms the optic chiasm, where fibers partially cross sides

What 3 CN help with eye movement?

Oculomotor, Trochlear, Abducens

What are the functions of the Oculomotor Nerve?

• moves eye up, down, medially, laterally, and downward

• raises the eyelid

• constricts the pupil

What are the functions of the Trochlear Nerve?

• Controls the superior oblique muscle — turns the eye down and in

What are the functions of the Trigeminal Nerve?

• largest cranial nerve

• relays sensory information from the
  face, head, cornea and oral cavity

What are the functions of the Abducens Nerve?

Controls the lateral rectus muscle — turns the eye outward

What are the functions of the Facial Nerves?

• Motor - innervates the muscles of facial expression

• Sensory – innervates taste receptors on tongue

What is the function of the Vestibulocochlear Nerve?

• Cochlear branch - audition

• Vestibular branch – balance, equilibrium, and position of the
  head in space

What is the function of the Glossopharyngeal Nerve?

• Sensory: taste from the posterior aspect of the tongue

• Motor: swallowing

What is the function of the Vagus Nerve?

• Sensory: taste information from the palate and epiglottis

• Motor: carries parasympathetic info to and from the heart,
  pulmonary system, esophogus, and GI tract

What is the function of the Accessory Nerve?

Motor: Controls the trapezius and sternocleidomastoid muscles — shrugging the shoulders and turning the head

What is the function of the Hypoglossal Nerve?

Motor: Controls the muscles of the tongue — essential for speech and swallowing

SAME DAVE (you don't have to know this, but it is helpful)

Sensory = Afferent

Motor = Efferent

Dorsal = Afferent

Ventral = Efferent

What do Neurons even do girl?

• Transmits info throughout the body

• Communicate with each other through junctions (synapses) → allows complex processing and control of bodily functions

What is a Soma and why is it essential?

• Cell body

• Contains nucleus & other organelles essential for neuron’s metabolic processes

What is a Dendrite and what’s its purpose?

• Branched extensions of neuron

• Receives signals from other neurons

• Acts as input pathways for the neurons

What is an Axon and what does it do?

• Single, long extension of the neuron

• Serves as output pathway

• Transmits signals to other neurons, muscles, or glands

• Transmits Action Potentials from Soma → Terminal Boutons

• Ends at Synaptic Terminals where neurotransmitters are released to
  communicate with other cells

Why is the Axon Hillock important?

• a crucial transition zone for signal processing that connects the soma to the axon

• acts as a junction between cells ( & in some cases it acts as an impermeable barrier)

• AP is (typically) initiated here

• a key decision making point for the neuron

What is the composition, function, and impact of the Myelin (Sheath)?

• composed of lipids & proteins → forms multi layered sheath around axons

• acts as insulator for axon

• increases the speed of nerve conduction

• the more sheath an axon has → faster conduction rate (enables rapid neural communication)

What 2 cells make up the Myelin Sheath?

Glial Cells

• Schwann Cells

-PNS

-CAN Regenerate

• Oligodendrocytes

-CNS

-CANNOT Regenerate

What are the Node of Ranvier?

• gaps between segments of myelin sheath along the axon

• in these gaps, the axon is exposed and contains high concentration of ion channels

• nerve signals jump from one gap to the next

What is an Axon Collateral?

• they project from the main axon structure

• they serve to transmit nerve signals to several parts of the nervous system simultaneously

What are Terminal Boutons?

*Interchangeable names include: Axon Terminal, Synaptic Terminal, Synaptic Boutons

emerge from the end branches of the axon and contain neurotransmitter substance

What is the Synaptic Cleft?

• is the space between a presynaptic neuron’s terminal boutons and a postsynaptic neuron’s dendrites

• the terminal boutons release their neurotransmitter substances into said space

What is a Neurotransmitter?

• a chemical stored in the terminal boutons

• it is released into the synaptic cleft to transmit messages to another neuron

What is a Presynaptic Neuron?

• first order neuron

• releases its neurotransmitter in the synaptic cleft

What is a Postsynaptic Neuron?

• second order neuron

• receives the presynaptic neuron’s neurotransmitter substance from the synaptic cleft—but only if the neurotransmitter possesses the specific molecules that can bind to the postsynaptic neuron’s receptor sites

What is Action Potential/AP?

• an electrical signal that travels down the axon to the axon terminal

• causes vesicles at the axon terminal to fuse to the presynaptic membrane

What happens during Synaptic Transmission?

• Vesicles release neurotransmitter into synaptic cleft

• Neurotransmitter diffuses across synaptic cleft until it reaches the dendrites on the postsynaptic neuron

• Neurotransmitter binds to receptors on postsynaptic dendrites—each neurotransmitter has its own receptors

• Neurotransmitter is then removed from the synaptic cleft in 1 of 3 ways
  (must be removed to make room for more neurotransmitters when the
  next AP arrives)

During Synaptic Transmission, Receptors cause the postsynaptic neuron to be what?

• more likely or less likely to fire a new action potential
  -Excitatory receptor – more likely
  -Inhibitory receptor – less likely

What are the 3 ways Neurotransmitters are removed from the synaptic cleft?

• Reuptake transporter: take neurotransmitters back into the presynaptic cell

• Glial cells: absorb the neurotransmitter

• Enzymes: proteins that break down the neurotransmitter while in the synaptic
  cleft
  
  

Entire process is very, very fast

What are some Neurological Disorders that occur due to a disruption in neuron function?

• Alzheimer's disease

• Parkinson's
  disease

• Epilepsy

…to name a few

What is another name for the Postcentral Gyrus?

Primary Somatosensory Cortex or SS1

What is the Somatosensory Cortex responsible for?

Detection of incoming somatosensory information from the periphery

• Tactile

• Pain/temp

• Proprioception

• Kinesthesia

• Vibration

Does NOT interpret the information

Where must info travel through, before it travels to the SS1?

Thalamus

Where is the somatosensory homunculus located?

Postcentral Gyrus

What is the somatosensory homunculus?

• Cortical representation of every body part’s somatosensation

• Somatotopical organization of body sensation from the contralateral side of the body

• Related to the motor homunculus in the precentral gyrus

• Face, hands, mouth have large representation

• Not a permanent organization

• Plasticity available should injury or disease occur. (e.g., people who read braille: the finger used has a very large cortical representation)

What makes Primary Somatosensory Cortex Lesions unique?

• loss of sensation is contralateral

• determined by the part of the homunculus that is damaged

What does the Secondary Somatosensory Area/SS2 do?

• interprets info

• attaches meaning to the somatosensation

• just posterior to SS1

What happens when there is a Lesion at the SS2?

Tactile agnosia – inability to attach meaning to sensation

• Astereognosis

• 2-point discrimination disorder

• Agraphesthesia

• Extinction of simultaneous stimulation
  
  

An impaired SS1 comes with what types of risks?

• Contralateral sensory loss to limbs and trunk

• At risk for decubitus ulcers

• At risk for burns

Examples of an impaired SS2

• Unable to locate an object by touch only

• Left somatosensory neglect syndrome – may drop objects in left hand

What does the Primary Visual Cortex do & also what is the result of a lesion here?

• Detects visual input but doesn’t interpret it

• Most posterior region of the occipital lobe

• Lesions: loss of sight even though visual anatomy intact
  
  

What is the role of the Visual Association Areas?

• Interprets the visual input & attaches meaning

• 30+ specialized areas

• Development appears to be dependent upon experiences (e.g., color vision, geometric patterns, form discrimination)

What are the results of Visual Deficits?

• Loss of visual field

• Overcompensation for loss of visual field

• Aware of loss

• Inability to differentiate characteristics

• Significant difficulties perceiving, processing, and interpreting visual stimuli→affecting all daily activities and safety

What is the role of the Primary Auditory Cortex?

• temporal lobe

• detects sound

• sends info to auditory association areas for interpretation

What would be the result of an Auditory Cortex lesion?

• Unilateral deafness/bilateral deafness

• May still have the ability to process the information

What is the role of the Auditory Association Areas?

to interpret auditory data

What would be the result of an Auditory Association Area lesion?

auditory agnosia – inability to attach meaning to specific sounds

What would Broca’s Area lesions lead to?

• Expressive aphasia/non fluent speech

• able to understand what is spoken

• unable to form meaningful sentences

What is Broca’s Area?

• Only in L Hemisphere

• Responsible for verbal expression of language

What is Wernicke’s Area?

• Only in L hemisphere

• Comprehends the spoken word

What would Wernicke’s Area lesions lead to?

• Receptive aphasia

• Able to form understandable sentence

What are the Auditory Deficits that result due to the lesion?

• Impaired auditory reception (what we think of as hearing loss)

• May miss environmental stimuli (phone, doorbell, someone speaking)

• Inability to attach meaning to sounds