neuro exam 1

Dorsal, ventral, caudal, rostral on the brain

superior, inferior, medial, lateral

Exterior Views of the Brain

Superior - you are superior and looking down on the brain

Inferior - you are inferior and looking up at the brain

Lateral- side view of the brain

Medial- toward the midline

sagittal (midsagittal), coronal, horizontal, and transverse planes

Neurons

Brain cells that send signals to create all of our experiences 

Three main components of neurons

The three main parts of a neuron are the dendrites, the cell body (soma), and the axon.

Direction of information flow for neurons

Dendrites → Cell body → Axon → Axon terminals

(Dustin Calls Anna Auntie Today)

Myelin Sheath

a protective, fatty-protein layer that wraps around the long fibers of nerve cells.

protects axons

Nodes of Ranvier

segments in the myelin sheath

 message can jump from node to node very quickly

What does myelin do?

Myelin sheath allows action potentials to jump from one node of Ranvier to the next. It's faster and more efficient and necessary for long motor neurons.

• Damaged myelin impairs nerve conduction (as in multiple sclerosis)

• Damaged neuron/myelin= distorted messages

What happens at the synapse?

At the synapse, one neuron passes a signal to another neuron.

Efferent vs Afferent Neurons

Outgoing MOTOR response- EFFERENT NEURONS

Incoming SENSORY response- AFFERENT NEURONS

Grey matter vs. white matter

Grey matter- neuron cell bodies, generate signals

White matter- neuron cell axons, carry signals

-In the brain, grey matter outside and white matter inside

-In the spinal cord, white matter outside and grey matter inside

The CNS has about the same amount of…

glial cells and neurons

Lateralization of somatosensory and motor function

Motor and sensory functions are controlled contralaterally.

Right side of brain → controls left side of body

Left side of brain → controls right side of body

Somatotopy with overlap (i.e., motor homunculus)

About 90% of motor and sensory fibers cross/decussate at the brainstem in the medulla

Laterality of brain organization (left hemisphere versus right functions)

Left hemisphere → language

Right hemisphere → emotions, visuospatial skills, musical skills, paralinguistic functions, and attention

Sensorimotor control is contralateral.

• Everything below the neck is controlled by the opposite side of the brain.

Each Brodmann area has a unique…

cytoarchitecture and function

Important Brodmann’s Areas

BA01 - Primary somatosensory cortex (S1)

BA02 - Secondary somatosensory cortex (S2)

BA03 - Tertiary somatosensory cortex (S3)

BA04 - Primary motor cortex (M1)

BA17 - Primary visual cortex (V1)

BA18 - Secondary visual cortex (V2)

BA41 - Primary auditory cortex (A1)

BA42 - Secondary auditory cortex (A2)

BA 22 - Wenicke's area

BA 44 - Broca's

major gyri and sulci and their FUNCTIONS

??? Come back later

If a given lobe, gyri, Brodmann area is damaged, what will the symptoms be?

Frontal lobe damage → problems with executive functions, personality, planning, impulse control, or motor function

Precentral gyrus / BA 4 damage → motor problems

Left inferior frontal gyrus / BA 44 damage → problems with speech production, associated with Broca's aphasia

Parietal lobe damage → sensory/perceptual problems and possible visuospatial problems

Postcentral gyrus / BA 1, 2, 3 → sensory problems

Right parietal damage → possible left neglect

Temporal lobe damage → auditory, language, memory, or olfactory problems

BA 41/42 damage → auditory processing problems

Left BA 22/Wernicke's area damage → problems with language comprehension/auditory word recognition

Right temporal damage → can cause problems such as amusia

Occipital lobe damage → visual problems

Difference between CNS and PNS and their subsystems

CNS = Central Nervous System

• Brain

• Spinal cord

PNS = Peripheral Nervous System

• All neurons/fibers outside the CNS

• Includes nerves that exit the brainstem and spinal cord

Commisural fibers

connects the 2 hemispheres of the brain

• between hemispheres= INTERHEMISPHERIC

• most interhemispheric connections are between homotopic areas

association fibers

connect cortical areas in the same hemisphere of the brain *** (ex right frontal lobe connected to right temporal lobe)

• Confined within hemisphere= INTRAHEMISPHERIC

• short - bend around a sulcus, connect adjacent gyri

• long - connect more distant cortical areas

main commisural fibers

Corpus callosum → association cortices ↔ opposite hemisphere

Anterior commissure → olfactory + part of limbic system

Hippocampal/posterior commissure → part of limbic system.

main Association fibers:

Superior longitudinal fasciculus (SLF) → all four lobes within each hemisphere

Arcuate fasciculus → Broca's ↔ Wernicke's

Inferior longitudinal fasciculus (ILF) → temporal ↔ occipital

Uncinate fasciculus → anterior temporal ↔ VPFC

Cingulum → medial frontal/parietal ↔ temporal

Superior Longitudinal Fasciculus (SLF)*

Inferior Longitudinal Fasciculus (ILF)

Arculate fasciculus (connects broca’s and wernicke’s)

Uncinate fasciculus

Cingulum

split brain syndrome

What: No communication between the left and right hemispheres

Cause: Complete sectioning of the corpus callosum

Symptoms: Usually normal cognitive function and behavior; problems mainly appear during specific tests or actions. Some people may have difficulty naming or identifying something that is presented to only one side of the body/visual field.

alien hand conflict

What: A hand seems to act on its own, as if it has a mind of its own.

Cause: Damage/disruption to brain areas involved in voluntary movement and communication between brain regions.

Symptoms: The person feels they cannot control the hand. The hand may perform actions without the person's intention, and the person may describe the hand's actions as if someone else is controlling it.

how are alien hand and split brain different?

Split-brain: The two brain hemispheres cannot communicate normally because the corpus callosum has been cut. Symptoms show up mainly during certain tasks.

Alien hand: A hand seems to act on its own, and the person feels like they cannot control it.

Main difference: Split-brain is about loss of communication between the hemispheres, while alien hand is about uncontrolled, seemingly independent hand movement

amygdala

Emotions, especially fear and emotional responses

Basal Ganglia:

Movement control and coordination of voluntary movement

Central sulcus:

Separates the frontal and parietal lobes; separates motor and sensory areas

Cerebellum:

Balance, coordination, and fine motor control

Cingulate gyrus:

part of the limbic system.

Emotion, motivation, and behavior

Hypothalamus:

Homeostasis; regulates hunger, thirst, body temperature, sleep, and hormones

Insula:

Taste, body sensations, and awareness of internal body states

Limbic system:

Emotion, memory, and motivation

Lateral sulcus:

Separates the temporal lobe from the frontal and parietal lobes

Lateral ventricles:

CSF-filled spaces in the brain

Longitudinal fissure:

Separates the left and right cerebral hemispheres

Thalamus:

Relays sensory information to the cerebral cortex

left hemisphere functions

• Processing speech sounds

• Basic langauge comprehension

• Motor speech

• Facial recognition

• Motor control for the right side of the body

right hemisphere functions

• Visuoapatial processing

• Emotion

• Supralinguistics (sarcasm, humor, tone)

• Music

left neglect- what’s involved, why more common than right neglect?

Left neglect: Not paying attention to or being unaware of things on the left side of space.

Brain area: Usually caused by damage to the right parietal lobe.

Why more common than right neglect? The right hemisphere pays attention to both sides of space, while the left hemisphere mainly attends to the right side. So right-hemisphere damage can cause left neglect, but left-hemisphere damage is less likely to cause right neglect.

glial cells

• Support cells that provide

  •  Structure

  •  Protection 

  • Waste management

• There are approximately the same number of neurons as glial cells in the CNS

what does myelin do?

Myelin acts as a protective, insulating layer around nerve fibers that speeds up electrical signals in the nervous system

electrical vs chemical gradients

Electrical signals (action potential) - within the neuron

Chemical signals (neurotransmitters) - between neurons in the synaptic space

Which ions are in greater/lesser concentration inside vs. outside cell for a neuron at rest?

More sodium (Na+) and calcium (Ca2+) outside the cell

More potassium (K+) inside the cell

What happens to the ions inside/outside the neuron from rest, to stimulation, during firing, and then during the absolute and relative refractory periods?

• At rest, Na⁺ and Ca²⁺ are higher outside and K⁺ is higher inside.

• During depolarization, Na⁺ moves into the neuron.

• During repolarization, K⁺ moves out.

• During hyperpolarization, K⁺ continues to leave briefly, making the inside more negative.

• The Na⁺/K⁺ pump then helps restore the resting ion gradients.

What are the channels and pumps doing?

Na⁺ channels open → Na⁺ enters

K⁺ channels open → K⁺ leaves

Na⁺/K⁺ pump → restores Na⁺ and K⁺ gradients

diagram of the action potential

resting membrane potential

The inside of the cell is negatively charged compared to the outside when the neuron is at rest.

hyperpolarization

• The difference in electrical charge between the inside and outside of the cell becomes greater as the inside of the cell becomes more negative, thus increasing the polarization.

polarization

Inside is more negative than outside.

depolarization

• the difference in electrical charge between the inside and outside of the cell becomes smaller (and may disappear altogether or reverse) as the inside of the cell becomes more positive, thus decreasing the polarization

• aka Inside becomes less negative/more positive.

repolarization

• The process by which the resting (baseline) electrical polarization of a neuron is re-established.

All or nothing principle of action potential  

An action potential either happens completely or does not happen. The neuron must reach threshold to fire.

What are the absolute and relative refractory periods?

• Absolute refractory period: Neuron cannot fire again.

• Relative refractory period: Neuron can fire again, but needs a stronger stimulus.

• ARP is about 3–4 ms; RRP follows and lasts about 5–10 ms.

What role does the sodium-potassium pump play?  

Uses ATP to move Na⁺ out and K⁺ in, helping restore the resting ion gradients

Signal Propagation

The action potential travels down the axon by activating one section after another. In myelinated axons, it jumps from node to node. Larger axons and myelinated axons are faster.

What happens at the synapse?

Action potential arrives → Ca²⁺ enters → neurotransmitter is released → neurotransmitter binds to the next neuron → next neuron is excited or inhibited.

Craniectomy vs craniotomy

Craniotomy: A piece of the skull is temporarily removed and then put back.

Craniectomy: A piece of the skull is removed and not immediately put back.

Parkinson’s Disease

Degeneration of the substantia nigra → dopamine insufficiency.

Symptoms: resting tremor, too much or too little movement, masked face, progressive disorder.

Multiple Sclerosis:

Autoimmune disease that damages myelin, slowing or blocking signals.

Symptoms: walking difficulties, cognitive changes, vision issues, and possible swallowing/speech problems.

Myasthenia Gravis:

Autoimmune disruption of acetylcholine (ACh) receptors → not enough receptors open.

Causes progressive muscle weakness with activity that improves with rest.

Frontal Lobe- (movement, planning, decision-making, speech)

• Precentral gyrus — Gyri — voluntary movement

• Superior frontal gyrus — Gyri — executive functions

• Middle frontal gyrus — Gyri — planning/executive functions

• Inferior frontal gyrus — Gyri — speech (Broca’s area)

• Central sulcus — Sulci — separates frontal and parietal lobes

• Precentral sulcus — Sulci — separates motor areas

Parietal lobe — (sensation, spatial awareness, sensory processing)

• Postcentral gyrus — Gyri — sensation

• Superior parietal gyrus — Gyri — visuospatial processing

• Inferior parietal gyrus — Gyri — higher-level processing

• Supramarginal gyrus — Gyri — memory and language

• Angular gyrus — Gyri — reading and writing

• Intraparietal sulcus — Sulci — separates superior/inferior parietal areas

Corpus callosum

Connects the left and right cerebral hemispheres.

Thalamus

Relays sensory information to the cerebral cortex.

Hypothalamus

Controls homeostasis, hormones, and basic drives.

Midbrain

Controls movement and processes visual and auditory reflexes.

Pons

Regulates breathing and sleep, and relays information within the brain.

Medulla

Controls vital autonomic functions like breathing and heart rate.

Cerebellum

Controls balance, coordination, and smooth voluntary movement.

parietal, frontal, occipital, temporal

Frontal lobe

Brain region responsible for voluntary movement, planning, decision-making, and speech.

parietal lobe

Brain region responsible for sensation, spatial awareness, and sensory processing.

Temporal lobe

Brain region responsible for hearing, language processing, and memory.

Occipital lobe

Brain region responsible for visual processing and vision.