Organization of the nervous system

What are the two subdivisions of the nervous system?

CNS and PNS

What are cell bodies in the CNS called? PNS?

Nuclei for CNS and Ganglia for PNS

What are the functions of the somatic PNS?

Sensation(afferent) and Motor(efferent)

What are the functions of the somatic motor neurons?

What are the functions of the somatic motor neurons?

What are the three divisions of the autonomic PNS?

• Sympathetic

• Parasympathetic

• Enteric NS(GI)

What does the autonomic PNS sense?(afferent)

Sensation from visceral organs

What does the autonomic PNS do?(efferent)

What are 4 responses that the sympathetic nervous system elicits?

When is the sympathetic nervous system on?

It is constantly on.

• Tonic stimulation of blood vessels

• Active during respiratory cycle. - acts during inspiration to dilate airways.

What tissues does the sympathetic nervous system innervate

Every tissue in the body

What are 5 responses that the parasympathetic nervous system elicits?

What tissues does the parasympathetic nervous system innervate?

Innervates head, viscera, and external genitalia

What does the vagus nerve do?

• it makes up 75% of the parasympathetic nervous system

• provides parasympathetic input to most of the thoracic and abdominal viscera

Enteric neurons have no direct innervation from the….

CNS

How is the enteric NS organized?

microcircuits that contain intrinsic primary afferent neurons that can respond to local stimuli to integrate information and coordinate motor output

What are the different reflex pathways that control digestive function?

• muscle contraction/relaxation

• Secretion/absorption

• Blood flow

What are the functions of CSF?

• cushion the brain from impact

• speedy removal of waste from extracellular fluid

What are some important medical uses for CSF?

• Measuring CSF pressure

• Analyzing CSF for pathology

• Drug targeting for brain

• High contrast in digital scans

Is CSF creation regulated?

No, it is constantly made

Where does CSF exit?

Specialized out pocketings on the superior surface of the brain called arachnoid granules. It can enter venous blood here.

Where is the choroid plexus found?

• it is found as vascularized secretory tissue in every ventricle

  • It is highly organized tissue consisting of epithelial cells and surround a core of capillaries and connective tissue

What does the BBB regulate?

ion concentrations, fluid volume balance, pH, and immune cell activity

• via tight junctions

What is some pathology associated with a “leaky” BBB

BBB breakdown allows neurotoxic blood-borne molecules and cells (e.g. leukocytes) to enter the brain, which subsequently initiates neuroinflammatory as well as innate and adaptive immune responses (microglia and astrocytes)

• Also can lead to dysfunctional efflux and impaired clearance of metabolic waste

• Implicated in aging-related dementia (vascular dementia) and potentially some neuropsychiatric conditions such as depression (when associated with neuroinflammation)

What does the DL PFC control?

•Cognitive/executive processing and control: Higher executive thought, planning, intelligence.

•Governs behavior dealing with abstract, cognitive goals: ambition, future plans.

What does the OM PFC control?

•Emotional processing and control

•Governs behavior dealing with social behavior and social/emotional goals

What are the 3 divisions of the brainstem?

• Medulla Oblongota

• Pons

• Midbrain

What does the Medulla oblongota do?

Functions – sensory input for touch, pain and temperature. Motor control over throat and pharynx. Handles respiration, digestion, and circulation and reflexes such as swallowing, coughing, and sneezing.

What does the midbrain do?

Midbrain: Eye movements, motor control, reward systems, control over pain. Vision- and hearing- related reflexes. Massive tracts passing through

What does the Pons do?

Sensation and motor for the face, hearing, eye movements. Significant role in cerebellar motor processing. Continuation of medulla functions. Helps control breathing rhythms.

Sensory data flows into the ________ from the brainstem,

along with emotional, visceral, and other information from

different areas of the brain

Thalamus

What does the thalamus do?

The thalamus relays these messages to the appropriate
areas of the cerebral cortex
• Almost all axons going to the cortex synapse on neurons
in the thalamus
• The thalamus coordinates signaling, including timing

The hypothalamus is connect to what system?

Endorcrine

What are the 3 components of the limbic system?

• Amygdala

• Hippocampus

• Septum

What are the amygdala’s functions?

• the recognition of facial emotions, especially
fear
• learned fear pathways
• emotional memory formation
• It is thought of as the structure assigning
emotional valence (emotional value) to sensory
experiences.

Habit learning doesn’t require _______

Hippocampus

What are the things that inhibit hypothalamus?

Negative feedback

Hippocampus/frontal cortex

What brain area activates the HPA axis?

amygdala

What changes in the brain happen with PTSD?

Amygdala is hyperreactive to trauma-related stimuli
• Loss of hippocampal volume
• Loss of prefrontal cortex volume, hypoactivity
• Higher brain structures don’t dampen amygdala driven emotional responses

What do spinal cord layers I to VI do?

Dorsal horn: sensory processing

What do spinal cord layers VII do?

Intermediate zone: Some spinocerebellar info + sympathetic and

parasympathetic motor

What do spinal layers VIII and IX do?

ventral horn: motor neurons

What do spinal layers X do?

Central gray(interneurons)

What are the general steps the brain does once it receives sensory infromation?

1. Compares input with existing memories(new or not)

2. Integrate information from all sensory fields

3. The amygdala and memories are used to assign an
   emotional significance to the experience and the
   hippocampus records it. Limbic lobe.

   All this information is finally sent to the frontal lobes for processing

What is transductions?

Cells convert an external signal into membrane voltage difference

Explain the dorsal column lemniscal pathway

1st neuron starts from DRG and ascends to the brainstem where it synapses in caudal medulla

2nd neuron crosses the midline at the brainstem and ascends to the thalamus

3rd neuron goes straight up to the Primary somatosensory cortex(parietal lobe)

What does the DCML sense?

- carries touch / proprioceptive information
- dorsal columns (and dorsal column nuclei) organized somatotopically

What does the spinothalamic pathway sense?

- carries pain/temperature information
- also exhibits somatotopy
- sensory input crosses midline at spinal cord

Explain the spinothalamic pathway

1st neuron crosses over at the spinal cord level and synapses on the thalamus

2nd neuron goes from thalamus to primary somatosensory cortex

Explain the auditory pathway

spiral ganglion—>ventral cochlear nucleus—>superior olive—>inferior colliclus—>MGN—>Auditory cortex

How is the auditory cortex mapped?

tonotopically

What does tonotopic and somatotopy have in common

They are both plastic, can be changed

What are the first neurons that rods and cons synapse on?

Bipolar cells

What do bipolar cells synapse onto? Where do these neurons synapse?

retinal ganglion cell bodies, these synapse onto thalamic structure(LGN)

Lesions in LGN cause…

blindness in part or all of the visual field

What does the superior colliculus do?

It coordinate the orientation of the eyes and head in space during rapid , reflex eye movements

Ensures rapid reactions without cortical input

Explain cortical blindness

visual field deficits that include macular sparing (V-I)

Explain central color blindness

Color information can be detected by the retinas (retinal pigments, reactions and detection are OK), but color is perceived only as shades of gray. (V-II)

Explain visual discrimination disorders

Difficulties matching lines of different types, unfamiliar faces that have different emotional expressions and are viewed from different angles, discriminating overlapping figures, etc. (V-II)

Explain visual agnosias

Cannot identify person, place or thing, although might be able to identify if using touch or sound.

What is the difference between the dorsal and ventral vision pathways?

Dorsal pathway – processing of object motion, navigation, directing eye movements, motion perception
Ventral pathway – color and form perception, visual perception and visual memory