Brain and Cranial - Lecture Flashcards
1
Q
Name major divisions of brain + subsections
A
- Forebrain - cerebrum + diencephalon (thalamus, hypothalamus, epithalamus, third ventricle)
- Midbrain / Mesencephalon
- Hindbrain (cerebellum + pons + medulla oblongata)
brain stem -> midbrain (mesencephalon, pons, medulla oblongata).
2
Q
Describe Cerebrum
A
Function
Higher-order processing (sensory perception, voluntary movement, cognition, language).
Landmarks
- Lobes: Frontal, Parietal, Temporal, Occipital, Insula
- precentral gyrus: primary motor cortex (frontal lobe)
- postcentral gyrus: primary somatosensory cortex (parietal lobe)
- central sulcus: separates precentral and postcentral gyrus
- Lateral sulcus / sylvian fissure: separates temporal lobe from frontal/parietal
- Longitudinal fissure: separates the two hemispheres
- Transverse fissure: separates the cerebellum from cerebrum
- lateral ventricles
- corpus callosum: major commissural fiber connecting hemispheres (white matter)
organization
Cortex: Outer layer of gray matter – neuronal cell bodies.
White matter: Internal region – myelinated axon tracts.
Basal nuclei: Deep masses of gray matter – subcortical neuron clusters.
we don’t call the cerebral cortex “nuclei” because it’s layered, not clustered.
3
Q
Name primary, secondary brain vesicles and derived brain regions
A
Primary:
Prosencephalon,
Mesencephalon,
Rhombencephalon
Secondary:
Telencephalon, Diencephalon
Mesencephalon
Metencephalon, Mylencephalon
At Birth:
Cerebrum, Diencepyhalon
Midbrain
Cerebellum, Pons, Medulla oblongata
4
Q
Describe Diencephalon
A
Function
Sensory relay, autonomic control, hormone regulation.
Landmarks
- Thalamus: relay center for sensory input (except smell)
- Hypothalamus: regulates autonomic and endocrine functions
- Epithalamus: includes pineal gland (melatonin) - involved in circadian rhythm
- Third ventricle: between left and right thalamus
5
Q
Describe Physical layout of ventricular system
A
The ventricular system
is a continuous, interconnected network of cavities within the brain that are filled with cerebrospinal fluid (CSF) and lined with ependymal cells.
Lateral Ventricles: one in each cerebral hemisphere. Main portion in parietal lobe, each has an anterior horn extending into frontal lobe, a posterior horn extending into the occipital lobe, and inferior horn extending into the temporal lobe.
3rd ventricle: In the diencephalon (between thalami)
4th ventricle: In the hindbrain (between pons/medulla and cerebellum)
Lateral ventricles connect to the third ventricle via the interventricular foramen. Third ventricle connects to the 4th ventricle via the cerebral aqueduct. CSF exist the ventricular system via the median & lateral apertures
6
Q
Define Septum pellucidum
A
- thin, vertical membrane made of neural tissue.
- separates the anterior horns of the left and right lateral ventricles.
- Located between the corpus callosum (above) and the fornix (below)
7
Q
5 functions of CSF
A
The ventricular system’s main role is to support and protect the central nervous system through the production, circulation, and regulation of cerebrospinal fluid (CSF). Its functions include:
- Physical Protection
CSF acts as a cushion, absorbing shocks from impacts or sudden movements.
It creates a fluid buffer between the brain and the skull, reducing the risk of injury.
- Buoyancy
The brain weighs approximately 1,400 grams, but when suspended in CSF, its net weight is reduced to about 50 grams.
This buoyant support prevents the brain from compressing its own blood vessels or damaging lower structures due to its weight.
- Homeostasis and Chemical Stability
CSF helps regulate the chemical environment of the CNS by maintaining pH, electrolyte balance, and osmotic pressure.
It provides a stable environment necessary for proper neuronal function.
- Waste Removal
CSF removes metabolic waste, toxins, and excess neurotransmitters from the brain.
It facilitates exchange with the blood through structures like the arachnoid granulations and the glymphatic system.
- Nutrient Distribution
CSF helps distribute nutrients (such as glucose and ions) to brain tissues.
It also serves as a medium for the transport of hormones and signaling molecules.
8
Q
Describe CSF production
A
- Blood enters fenestrated capillaries in the choroid plexus (within all four ventricles).
- Plasma leaks out of these permeable capillaries into the surrounding connective tissue stroma.
- This plasma is then filtered and modified by a layer of specialized ependymal cells (choroid plexus epithelium), with tight junction at apical ventricle facing surface (blood-csf barrier)
cells actively transport ions (e.g., Na⁺, Cl⁻) into the ventricular space.
Water follows osmotically via aquaporins.
Glucose and other essential solutes are selectively transported.
The result is CSF, a clear fluid low in protein and cells, but rich in specific ions, secreted directly into the ventricular system.
9
Q
Define ependymal cells
A
A type of glial cell that lines the ventricles of the brain and the central canal of the spinal cord
Ciliated ependymal cells: help circulate cerebrospinal fluid (CSF)
Modified ependymal cells in the choroid plexus: produce CSF
10
Q
Define choroid plexus
A
The choroid plexus consists of modified ependymal cells surrounding a core of fenestrated capillaries and loose connective tissue.
Functions:
Produces cerebrospinal fluid (CSF)
Forms the blood–CSF barrier
Location
Present in all four ventricles
Cells
Composed of ependymal-derived, cuboidal, epithelial-like cells. Glial in origin, but function as epithelial cells. Unlike other ependymal cells, have tight junctions at the apical surface. estricts substance exchange into the cerebrospinal fluid (CSF).
11
Q
What are the 4 components that protect the brain?
A
- Bones of skull: prietal, frontal, temporal occipital
- Cranial Meninges: three connective tissue layers - Dura, arachnoid, pia
- Cerebrospinal fluid (CSF)
- Blood-brain barrier
12
Q
Describe the Cranial Meninges
A
Three connective tissue layers that surround and protect the brain, enclose the cerebrospinal fluid (CSF), and support blood vessels.
-
Dura layer: Thick, fibrous outer layer composed of two sublayers:
- periosteal layer: attaches to the skull
- meningeal layer: Lies adjacent to the arachnoid mater and continues into the spinal canal as spinal dura. - Arachnoid mater: Web-like middle layer. Separated from pia by subarachnoid space, which contains CSF and blood vessels. Connected to pia via arachnoid trabeculae. Anchors blood vessels. Continues into the spinal cord and maintains the subarachnoid space, which contains cerebrospinal fluid
- Pia matter: Thin, delicate inner layer. Adheres tightly to the brain surface, following contours (gyri and sulci). Helps anchor larger blood vessels of cerebrum. Also continues into the spinal cord.
13
Q
Describe Dural Venous Sinuses
A
venous channels located within the dura mater, formed either
- between the periosteal and meningeal layers of the dura (e.g., superior sagittal sinus)
- within folds of the meningeal layer alone, where the meningeal dura separates and creates a channel (e.g., inferior sagittal sinus, straight sinus).
the majority of arachnoid granulations are in the superior sagittal sinus, some in transverse, straigt, and occipital as well.
14
Q
Define and Name Dural Folds
A
Where the meningeal layer folds inward, away from the periosteal layer, it forms dural septa that partition and support the brain.
Falx cerebri – a vertical fold that separates the two cerebral hemispheres; attaches anteriorly to the crista galli and posteriorly merges with the tentorium cerebelli.
Tentorium cerebelli – a horizontal fold that separates the occipital lobes from the cerebellum.
Falx cerebelli – a small midline fold between the two cerebellar hemispheres.
Diaphragma sellae – a circular sheet covering the sella turcica, with a hole for the pituitary stalk (infundibulum).
15
Q
Arachnoid Granulation
A
small, tufted projections of the arachnoid mater that extend through the dura mater into the dural venous sinuses, primarily the superior sagittal sinus.
one-way valves that allow cerebrospinal fluid (CSF) to pass from the subarachnoid space into the venous blood, but prevent backflow. This is the primary mechanism by which CSF is reabsorbed into the bloodstream, maintaining normal CSF pressure and volume.
16
Q
Define Meningitis
A
Inflammation of the meninges
- caused by bacterial or viral invasion of the CNS by way of the nose and throat.
- Pia mater and arachnoid layer are most often affected
- Causes swelling of brain, enlargement of ventricles, hemorrhage
- signs include, high fever, stiff neck, drowsiness, headaches
- diagnosed by examining the CSF -> spinal tap
17
Q
Describe CSF circulation
A
- CSF is produced in the choroid plexus of the lateral ventricles from plasma filtered through fenestrated capillaries and processed by ependymal (choroid epithelial) cells.
- CSF flows through the interventricular foramina (of Monro) into the third ventricle, where additional CSF is produced, then through the cerebral aqueduct into the fourth ventricle, where more CSF is produced.
- From the fourth ventricle, CSF exits via the median aperture (foramen of Magendie) and lateral apertures (foramina of Luschka) into the subarachnoid space. A small amount continues into the central canal/sub arachnoid space of the spinal cord.
- CSF circulates in the subarachnoid space, bathing the brain and spinal cord, providing buoyancy, protection, nutrient transport, and waste removal.
- CSF is reabsorbed into venous blood through arachnoid granulations into the dural venous sinuses, mainly the superior sagittal sinus.
- It then drains from the venous sinuses into the internal jugular vein.
18
Q
Blood Brain Barrier
A
The blood-brain barrier (BBB) is a selective, protective barrier that regulates the passage of substances from the blood into the brain’s extracellular fluid, maintaining a stable environment for neural function.
Function
1. Protects the brain from toxins, pathogens, and fluctuations in plasma composition
- Maintains ionic and neurotransmitter balance for proper neuronal activity
- Restricts access of immune cells and antibodies, limiting inflammation in CNS
Structure
Formed by endothelial cells of brain capillaries connected by tight junctions, which prevent paracellular diffusion of most substances. Astrocyte end-feet (perivascular feet) surround the capillaries and signal to endothelial cells to maintain the tight junctions and barrier properties, and provide additional layer.
Selective Permeability
Lipid-soluble substances (e.g. oxygen, CO₂, alcohol, nicotine, anesthetics)
→ Cross easily by diffusion through endothelial membranes.
Water-soluble substances (e.g. glucose, amino acids, ions)
→ Require specific transport proteins to cross the barrier.
Large or charged molecules (e.g. most drugs, proteins, pathogens)
→ Blocked unless actively transported or unless BBB is disrupted.
• Small • Lipid-soluble (lipophilic) • Non-polar or weakly polar • Uncharged at physiological pH ⸻ Examples • Gases: • Oxygen (O₂) • Carbon dioxide (CO₂) • Nitric oxide (NO) • Lipid-soluble molecules: • Ethanol • Nicotine • Anesthetics (e.g., diethyl ether) • Barbiturates • Some steroid hormones (e.g., cortisol
19
Q
Circumventricular Organs
A
Specialized structures in the brain located around the third (diencephalon) and fourth (medulla) ventricles that lack a typical blood-brain barrier (BBB).
They contain fenestrated capillaries, allowing for free exchange between blood and brain tissue.
Function
1. Monitor the composition of the blood (e.g., osmolarity, hormones, toxins)
2. Secrete hormones directly into the bloodstream - neuroendocrine function
3. Initiate responses to systemic changes (e.g., vomiting, thirst, endocrine regulation)
Circumventricular Organs associated with hypothalamus
1. detect blood osmolarity -> thirst.
2. angiotensin -> blood pressure (the hypothalamus coordinates the automoic and endocrine response to BP. Medulla is more the “reflex” center)
Area in medulla
1. detects blood toxins -> vomiting reflex.
there are more areas but not related to others
20
Q
Location, Function, Major structures of Medulla Oblongata
A
- Location: Inferior part of brainstem, continuous with spinal cord; below the pons, anterior to the cerebellum.
-
Function:
- All ascending sensory and descending motor tracts pass through
- Regulates autonomic functions: BP, heart rate, respiration
- Contains relay nuclei for sensory and motor pathways
- Associated with visceral/autonomic control
-
Major Structures:
- Decussation of pyramids: Anterior motor tracts (corticospinal); site of motor fiber crossing
- Gracile & cuneate nuclei: Relay touch/proprioception via DCML pathway. Site of decussation.
- Trigeminal Sensory Pathway nuclei -> pain / temp face. Site of decussation.
- soliatary nuclus -> 2nd order neurons arise for taste (some fibers decussate, others do not) -> ventral nucleus hypothalamus
-
Olive: Lateral swelling
- Inferior olive: Cerebellar motor learning
- Superior olive: Auditory processing
- Cranial nerve nuclei: CN VIII–XII
21
Q
First-Order Neuron
A
The first neuron in a sensory pathway.
Carries sensory information from the periphery to the CNS.
Cell body: in a dorsal root ganglion (for body) or cranial nerve ganglion (for head).
Synapses in the spinal cord or brainstem, depending on the pathway.
22
Q
Second-Order Neuron
A
Receives input from the first-order neuron.
Located in the spinal cord (for pain/temp) or brainstem nuclei (for fine touch, proprioception).
Axons of second-order neurons cross (decussate) to the opposite side.
Most ascend to the thalamus and synapse in a thalamic nucleus.
23
Q
Third-Order Neuron
A
Located in the thalamus.
Projects from the thalamus to the primary somatosensory cortex of the cerebrum (postcentral gyrus).
Responsible for conscious perception of the sensation.
24
Q
gracile fasciculus cuneate fasciculus
A
-
Gracile fasciculus
→ Carries fine touch, vibration, proprioception from the lower body (below T6) -
Cuneate fasciculus
→ Carries same modalities from the upper body (above T6) - Both ascend in the dorsal columns of the spinal cord
- Synapse in the gracile and cuneate nuclei in the medulla oblongata
→ Together, they are part of the dorsal column–medial lemniscus (DCML) pathway.
25
Medial lemniscus
The medial lemniscus is an ascending sensory tract that carries fine touch, vibration, and conscious proprioception from the **contralateral side** of the body to the thalamus.
It is formed by the second-order neurons that originate in the **gracile and cuneate nuclei of the medulla oblongata**.
These axons decussate in the medullaand then ascend through the brainstem (medulla, pons, midbrain) to the ventral posterolateral (VPL) nucleus of the thalamus.
*gracile and cuneate fasciculus caryy sensory information to the gracile and cuneate nuclei*
26
Reflex centers of medulla oblongata
- coughing, vomiting, salivation, and swallowing -> primarily **parasympathetic** (via cranial nerves, especially **CN X**)
- **Cardiovascular reflexes** of medulla:
- **PNS** (e.g., vagus slows heart)
- **SNS** (e.g., baroreflex increases sympathetic tone to raise BP)
- Medulla controls **respiratory reflexes** via:
- **Dorsal respiratory group (DRG)** → inspiration
- **Ventral respiratory group (VRG)** → forced breathing
- Regulates reflexes like **coughing, sneezing, breath-holding**
- Responds to **CO₂, O₂, pH** via input from chemoreceptors
- Medulla coordinates these autonomic reflexes automatically, without cortical input
27
Location, Function of Pons
**Location**
Prominent bulge superior to medulla oblongata and anterior to cerebellum
**Major structures**
- reticular formation: contains nuclei concerned with sleep and posture
- sensory and motor nuclei of cranial nerves, V, VI, VII, and VIII (VII has nuclei in both pons and medulla - pontomedullary junction)
- Nuclei involved with involuntary control of breathing - antagonistic apneustic and pneumotaxic centers
- ascending sensory tracts (from the spinal cord to the brain), descending motor tracts and **transverse fibers** in and out of cerebellum
28
List Midbrain primary structures
1. **Corpora Quadrigemina** (posterior/dorsal)
- Superior colliculi – visual reflexes (tracking, quick eye reflexes, blinking, turning head and eye)
- Inferior colliculi – auditory reflexes (hearing and sound reflexes, flinching from sound, turning to sound)
2. **Substantia Nigra** (between tegmentum and peduncle)
- relays inhibitory signals to thalamus and basal nuclei. Prevents unwanted body movement, degeneration leads to Parkinson's.
3. **Superior Cerebral Peduncles**
- descending fibers of corticospinal pathway
4. **Cerebral Aqueduct / Aqueduct of Sylvius**
- Narrow channel connecting the third and fourth ventricles; runs through the midbrain
29
Reticular Formation
*6*
- **Diffuse network** of neurons (gray matter) extending through the **entire brainstem**:
1. **Regulation of consciousness & arousal**
- Maintains alertness via the **reticular activating system (RAS)**
- Involves midbrain and upper pons
2. **Filtering of sensory input**
- Prevents **sensory overload** by filtering irrelevant stimuli
- Allows **focus and attention** (RAS function)
3. **Autonomic control**
- Regulates **heart rate, blood pressure, and respiration**
- Centered in the **medulla and lower pons**
4. **Somatic motor coordination**
- Helps control **muscle tone, posture, and reflexes**
- Integrates motor signals with balance and gaze
- Distributed through pons and medulla
5. **Pain modulation**
- Inhibits or facilitates pain signals via **descending analgesic pathways**
- Originates primarily in the **medulla**
6. **Habituation**
- Suppresses repeated, non-meaningful stimuli (e.g., ignoring background noise)
- Involves **midbrain circuitry**
*La formación reticular*
30
Epithalamus
**Location**
- Single midline structure in posterior diencephalon
- composed of paired components: pineal gland, habenular nuclei
- Forms the roof of the third ventricle
**Function Pineal glands**
- Produces melatonin in response to absence of light, signaling the body to prepare for sleep.
- Regulates sleep-wake (day-night) cycles by increasing melatonin secretion at night.
- Light exposure suppresses melatonin production, reducing drowsiness during the day.
**Function habenular nuclei**
act as a relay between the limbic system and midbrain
*el epitálamo*
31
Thalamus Function
> The thalamus is the brain’s **central relay station** for **sensory, motor, emotional, and cognitive** processing.
>
**Function**
1. **Sensory relay** – Receives all sensory input (except smell) and sends it to the appropriate **cortical areas** for conscious perception
- **Filters and modulates** input, deciding what reaches awareness
2. **Motor relay** – Receives **modulatory motor signals** from the **cerebellum** and **basal nuclei**, relays them to the **motor cortex** to help coordinate movement
3. **Emotion & memory** – Involved in **emotional processing** and **memory** through connections with the **limbic system**
*smell: Olfactory tract → Primary olfactory cortex*
*el tálamo*
32
List nuclei of thalamus and functions
1. **Anterior nuclei** – Part of **limbic system** → involved in **memory** and **emotion**
2. **Medial nuclei** – Relay to prefrontal cortex (frontal lobe)→ modulate **awareness** and **emotion**
3. **Ventral nuclei** – Relay **somatosensory input** to **parietal lobe**; also carry motor related signals from cerebellum and basal nuclei to motor cortex
4. **Posterior nuclei** – Relay to **occipital lobe** → contribute to **visual processing**
5. **Lateral nuclei** – Modulate activity in **cingulate gyrus** → involved in **emotional tone** and **pain perception**
*Somesthetic output: Motor responses generated in reaction to somatic sensory input such as touch, pain, temperature, or body position; involves activation of skeletal muscles based on processed sensory information.*
```
"All My Very Powerful Lessons"
```
*núcleos del tálamo*
33
Hypothalamus Function
> The hypothalamus is the brain’s **autonomic and endocrine control center**, linking the nervous and hormonal systems while regulating survival behaviors.
- Regulates **autonomic functions**: heart rate, BP, respiration, digestion, body temperature
- Produces **ADH** and **oxytocin** → stored/released by **posterior pituitary**
- Controls **thirst** and **hunger** drives
- Coordinates **voluntary and autonomic** motor responses (When you're nervous and decide to stand up (voluntary), your body also raises heart rate and blood pressure (autonomic)
- Controls **circadian rhythms** (biological clock)
- Modulates **emotional and behavioral drives** (via limbic system)
- Influences **subconscious skeletal muscle activity** (e.g., facial expression)
*El hipotálamo*
34
Cerebellum - Function
The cerebellum refines movement, supports balance, and contributes to motor learning, timing, and limited cognitive and sensory evaluation.
**Structure**
- Two hemispheres connected by **vermis**
- gyri of cerebellar cortex know as **folia cerebelli**
**Function**
1. **Coordinates voluntary movement** – smooths and refines motor output
2. **Maintains balance & posture** – regulates equilibrium and muscle tone
3. **Motor learning** – adapts and fine-tunes skilled movements
4. **Timing & rhythm** – regulates precise timing of motor activity
5. **Cognitive roles (minor)** – involved in attention, language, and planning
6. **Evaluates sensory input** – compares textures, processes different views of same object
- (Sensory input primarily processed by somatosensory cortex; cerebellum assists)
*el cerebelo*
35
cerebellar cortex
**3 Layers (Superficial to Deep):**
1. **Molecular layer** – Stellate & basket cells, Purkinje dendrites, parallel fibers
2. **Purkinje cell layer** – Single row of large **Purkinje cells**; axons inhibit deep nuclei via **GABA**
3. **Granule layer** – Receives input from **mossy fibers**; sends signals to molecular layer via **parallel fibers**
**Cerebellar Input:**
- **Mossy fibers**: From spinal cord/brainstem → synapse on **granule cells**
- **Climbing fibers**: From **inferior olivary nucleus** → synapse **directly on Purkinje cells**
```
Pyramidal cells in motor cortex initiate voluntary movement
Send collateral signal -main signal goes to muscles to initiate movement, copy goes to the cerebellum (pons -> middle cerebellar peduncle).
Signal copy enter as mossy fibers → processed by Purkinje cells
Cerebellum compares intended movement with sensory input
Sends inhibitory signals to deep cerebellar nuclei
Cerebellar output pathways:
To motor cortex (via superior cerebellar peduncle → thalamus) → refines voluntary motor commands
To brainstem motor centers (red nucleus, vestibular nuclei, reticular formation) → adjusts posture, balance, reflexes
```
36
Arbor vitae
White matter of cerebellum
**Function**
- Connects cerebellar cortex with deep cerebellar nuclei and cerebellar peduncles
- Carries Purkinje cell output to deep nuclei
- Carries afferent input (from brainstem/spinal cord) to cerebellar cortex
Signals transmitted via Peduncles:
- Superior: Sends cerebellar output (from deep cerebellar nuclei) to midbrain/thalamus
- Middle: Brings input from cerebral cortex (via pons)
- Inferior: Brings input from spinal cord and medulla
37
Cerebellar peduncles
**superior**
connect cerebellum with the mesencephalon, diencephalon, and cerebrum.
Pathway by which most cerebelar output travles
**middle**
communicate between cerebellum and pons.
Pathway by which most input from the rest of the brain enters
**inferior**
connect cerebellum with medulla oblongata.
Pathway by which most most spinal input enters cerebellum
> Superior = **output**, Middle = **brain input**, Inferior = **spinal/brainstem input**
38
Cerebral Peduncles
**Location**
Midbrain of brain stem
**Function**
contain descending motor tracts from the cerebral cortex to the brainstem and spinal cord.
```
Motor pathway
Starts: Primary motor cortex
Passes through: Internal capsule
Then: Cerebral peduncles (midbrain)
Descends: Through pons → medulla
Decussation: At pyramids of medulla
Continues as: Lateral corticospinal tract in spinal cord
Terminates: Anterior horn of spinal cord (synapses with lower motor neurons)
```
39
Major Functions Frontal Lobe
- **Motor control**:
- **Primary motor cortex** → conscious control of skeletal muscles
- **Broca's area** → speech production (usually left hemisphere)
- **Higher cognition**:
- Abstract thought
- Foresight and planning
- Decision making
- Social judgment
- Motivation and mood regulation
- **Memory**:
- Involved in **explicit (declarative) memory**, **formation**, and **retrievel**, important for **working memory**. Directs search and recall. Memory is stored in other association areas -> episodic/semantic (explicit) -> temporal, procedura -> basal nuclei cerebellum, emotional -> amygdala / hippocampus
- Works with **hippocampus** during **event replay** and memory consolidation
40
Major 5 Functions Insula
1. **Taste perception** (gustatory cortex)
2. **Pain processing** – integrates sensory and emotional aspects of pain
3. **Visceral sensation** – awareness of internal organ states (e.g., heartbeat, stomach). **primary visceral cortex** -> recieves in put verom ventral nucleus of thalamus
4. **Emotion and empathy** – involved in emotional awareness, especially **disgust**, **empathy**, and **self-awareness** -> connected to amygdala
5. **Autonomic regulation** – contributes to **cardiovascular homeostasis** and other autonomic responses
6. **consciousness**: The insula contributes to consciousness by integrating visceral sensation with emotion and self-awareness, helping create the subjective experience of being
41
Major Functions Parietal Lobe
- **Somatic Sensory Processing**
1. **Somatic sensation** – touch, pressure, pain, temperature (primary somatosensory cortex)
2. **Taste perception** – integrates gustatory input . The insula is the primary gustatory cortex responsible for conscious taste perception, while the parietal lobe contains association areas that integrate taste with texture, temperature, and somatosensory input from the mouth.
3. **Sensory integration** – Somatosensory association area -> interprets and integrates sensory input (like touch, pressure, temperature, and proprioception) to give meaning to what is felt — such as recognizing objects by touch or understanding spatial relationships.
4. **Spatial Awareness & Visual Processing** - think integrating visual input with somatosensory input. **Spatial perception** – body position, depth, navigation
5. **Visual processing** – contributes to spatial and motion aspects of vision
- **Higher Cognitive Functions**
6. **Language processing and integration** – integrates input for understanding speech (Wernicke’s area, especially in left hemisphere)
7. **Numerical awareness** – involved in quantity recognition, estimation, and calculation
```
Wernicke's area:
Temporal = comprehension - understanding spoken and written language (meaning of words in a sentence)
Parietal = Integrates auditory, visual, and somatosensory language input -> helps map visual wordds to sounds and link words to meaning.
```
42
Major Function Occipital Lobe
1. Visual awareness – conscious perception of visual stimuli
2. Visual processing – analysis of visual input (color, shape, motion, depth, etc.)
43
Major functions temporal lobe
- **Sensory Processing**
1. **Hearing** – Conscious perception of sound -> **primary auditory corte**. Auditory association cortex (associated with Wernick's area).
2. **Smell** – conscious perception of smell -> **primary oflactory cortex**. *association area of smell in orbitofrontal cortex*
- **Language & Communication**
3. **Language comprehension** – Interpretation of spoken and written language (→ Wernicke’s area, typically in left hemisphere)
- **Emotion & Learning**
4. **Emotion** – Processes emotional content via connections to the **amygdala**
5. **Learning** – Involved in encoding new information
- **Memory**
- **Memory consolidation**: The **hippocampus** (medial temporal lobe) is critical for transferring short-term memories to long-term storage It does this by reactivating memory patterns to the frontal lobe.
- **Verbal memory**: Stored in the **left temporal lobe** (dominant hemisphere)
- **Visual & auditory memory**: Stored in **right temporal lobe** (non-dominant); includes recognizing sounds, faces, images
- **Long-term storage**: Distributed across **temporal association cortex**
44
Define Higher-order functions
- cognition, memory, emotion, sleep, sensation, motor control, language etc
- involve interactions between cerebral cortex and all other areas of the brain
- involve conscious and unconscious information processing
- subject to modifications and adjustments
45
Define cognition
The range of mental processes by which we **acquire and use knowledge** - sensory perception, thought, reasoning, judgement memory, imagination and intuition
Cognition "occurs" in the association areas of the cerebral cortex. **Association areas**
- constitute about **75% of all brain tissue**
- build on what you already know -> more complex association areas pull from many different association areas to make complex pictures.
Much of what we know about cognition come from studies of patients with brain lesions, cancer, stroke and trauma.
46
Function of Parietal lobe association areas
Clinical Syndromes:
**Somatosensory association** area
- Integrates tactile, proprioceptive, and pressure input
1. Allows recognition of objects by touch **stereognosis**
2. Builds a sense of body position and limb awareness
3. Supports sensorimotor coordination (e.g., reaching accurately)
Non-somatosensory association areas
- Integrates visual, auditory, taste, and language-related input
1. Supports spatial awareness and attention to environment
2. Helps determine relevance of sensory stimuli
3. Contributes to language processing, reading, and mathematical thinking
4. Builds an integrated body-in-space map
5. Receives taste input from insula and integrates it with somatosensory signals from the mouth to support flavor perception
Key clinical syndromes:
- **Contralateral neglect syndrome**:
→ Ignores stimuli on side opposite lesion (typically left side of space)
→ Caused by damage to the posterior parietal cortex, usually on the right
- **Astereognosis**:
→ Inability to identify objects on contralateral side by touch despite normal sensation
→ Caused by damage to the **somatosensory association area**
47
Frontal Lobe Association areas
- **Motor association area (premotor cortex and supplementary motor area)**
→ Plans and sequences voluntary movements; involved in learned motor patterns and coordination. Creates motor plan sent to primary motor cortex
- **Broca’s area**
→ Motor planning for speech production and language expression (dominant hemisphere)
- **Medial prefrontal cortex**
→ Involved in self-reflection, emotional regulation, motivation, and social cognition. Limbic system
- **Orbitofrontal cortex**
Evaluates rewards and consequences; integrates sensory input with emotional and social decision-making
- **Other prefrontal association areas (e.g., dorsolateral and ventrolateral)**
Support executive functions: working memory, attention, reasoning, planning, and impulse control
Damage effects:
- Impaired movement planning and execution
- Poor judgment, impulsivity, socially inappropriate behavior
- Personality changes and emotional instability
Example:
- Phineas Gage – damage to the prefrontal cortex caused emotional disinhibition and personality shift
48
Temporal Lobe association areas
Clinical
*Think identifying stimuli*
**Memory-related** association areas
(Location: medial temporal lobe – includes hippocampus and parahippocampal regions)
- Involved in forming, consolidating, and retrieving long-term explicit (declarative) memories
1. Hippocampus consolidates short-term → long-term memory
2. Surrounding cortex (entorhinal, perirhinal, parahippocampal) stores contextual and spatial memory
3. Temporal association cortex stores long-term verbal and visual memory
**Speech and language association areas**
- Wernicke’s area: Comprehends spoken and written language
1. Links words with meaning (semantic processing)
2. Connects to other language areas via arcuate fasciculus
**Auditory association area**
- Interprets and gives meaning to sound
1. Distinguishes speech, music, environmental sounds
2. Helps recognize voices and tone
**General multimodal integration**
(Location: lateral and inferior temporal cortex)
- Integrates auditory, visual, and semantic information
1. Recognizes faces, objects, and scenes
2. Supports language comprehension and association
3. Links sensory input to memory and emotional tone (via limbic connections
**Visual agnosia**
cannot recognize objects -> lesions Inferior temporal cortex
**Auditory agnosia**
Can't recognize or interpret sounds -> superior temporal gyrus
**visual object agnosia**
Inability to recognize objects by sight, despite normal vision. -> Lesion in the inferior temporal cortex
*astereognosis -> inability to recognize objects by touch*
**anomic aphasia**
Damage to Wernick's area (parietal or temporal) -> can recognize object but cannot recall the word.
**prosopagnosia**
- person cannot remember familiar faces -> lesion to right fusiform gyrus (temporal lobe)
49
Limbic system
- A network of interconnected brain structures that regulate **emotion, motivation, memory, and behavior**
- Links **higher cognitive functions** with **emotional and autonomic responses**
---
**Core Structures & Their Roles:**
1. **Cingulate gyrus** – Emotion regulation, attention, pain processing, motivation
2. **Medial prefrontal cortex** – Decision-making, social behavior, emotional control, self-awareness
3. **nucleus accumbens - basal nuclei** – links emotion, motivation, and reward to behavior
4. **Amygdala** – Emotional memory, especially fear/aversion; links conscious thought to autonomic responses. Temporal lobe.
5. **Fornix** – White matter tract connecting hippocampus to hypothalamus (memory relay)
6. **Hippocampus** – Learning and memory formation (in temporal lobe)
---
50
Patient HM
- H.M. underwent surgery for epilepsy → **bilateral removal of medial temporal lobes**:
→ Nearly entire **hippocampus** removed
→ Partial **amygdala** removal
**Clinical Findings:**
1. **Severe anterograde amnesia** – Could not form new long-term **declarative (explicit)** memories
2. **Partial retrograde amnesia** – Lost some recent past memories; older childhood memories intact
3. **Preserved procedural memory** – Could learn motor skills (e.g., mirror drawing) without remembering the learning itself
4. **Normal intelligence, language, attention, and perception**
5. **Short-term (working) memory** remained intact
**Conclusion:**
> The **hippocampus** is essential for forming new long-term **declarative memories**, but **not needed for short-term memory or procedural learning**.
51
Function of Hippocampus
- Essential for **forming new long-term declarative (explicit) memories**
- Consolidates **sensory and cognitive information** into unified memories
- During an experience:
→ **Hippocampus actively processes input** while sensory events are happening. memories are not permanently stored there, but the hippocampus binds together the sensory, spatial, emotional, and contextual details. organizes the “scenes” — what happened, where, when, and in what order
- After the experience:
→ It "replays" memory traces to the **cerebral cortex**, which gradually encodes them into **long-term storage**.
→ This process is called **memory consolidation**
**Note**:
> The hippocampus is crucial for **forming and organizing new memories**, but **long-term storage occurs in the cerebral cortex**
| **Type of Memory** | **Primary Storage Area** |
52
Where are long term memories stored?
- **Temporal lobe** (primary site for declarative memory storage):
- **Left temporal lobe** → Verbal, language-based memories
- **Right temporal lobe** → Visual and spatial memories
- **Medial/anterior temporal regions** → Semantic memory (facts, concepts)
- **Frontal lobe**:
→ Involved in **retrieval**, **organization**, and **executive control** of memory
→ Stores some **episodic memory details**, especially sequencing and context
- **Parietal lobe**:
→ Supports **attention to memory**, **spatial context**, and **numerical memory**
- **Occipital lobe**:
→ Stores **visual elements** of long-term memories
- **Procedural memory** (skills, habits):
→ Stored in **basal nuclei**, **cerebellum**, and **premotor cortex**
→ Does **not** depend on the hippocampus
53
Amygdala role in emotion
- Receives input from multiple sensory systems (visual, auditory, olfactory, somatosensory)
- **Integrates sensory signals** and generates **emotional responses** (e.g., to a threatening face, pleasant music, or disgusting odor)
---
**Key Functions:**
1. **Fear & Threat Detection** – Detects danger; triggers defensive behaviors (e.g., freezing, fleeing)
2. **Food Intake & Aversion** – Assigns emotional value to food; can cause aversions after trauma
3. **Sexual Behavior & Social Emotion** – Guides emotional learning in social and reproductive contexts
4. **Emotional Attention** – Prioritizes emotionally significant stimuli in perception
---
**Output Pathways:**
- **To Hypothalamus**
→ Regulates **autonomic and endocrine responses** (e.g., heart rate, BP, nausea)
→ Key role in the **fight-or-flight** response
- **To Prefrontal Cortex**
→ Supports **regulation and expression of emotion**
→ Helps balance instinctive feelings with **socially appropriate behavior**
54
Parts of Brain involved in controlling sleep rhythm
1. **Cerebral cortex**
→ Final target of sleep-related signaling; involved in **conscious awareness** and enters reduced activity during sleep
2. **Thalamus**
→ Acts as a **sensory gate** during sleep; reduces sensory input to allow sleep
→ Helps regulate **sleep spindles** during non-REM sleep
3. **Hypothalamus**
→ Contains the **suprachiasmatic nucleus (SCN)** – the body's **master circadian clock**
→ Also regulates **melatonin release**, body temperature, and hormone rhythms
--> Releases **orexin** -> promotes wakefulness
4. **Reticular formation** (brainstem)
→ Contains the **reticular activating system (RAS)**
→ Promotes **wakefulness** and arousal by activating the cortex
---
**Summary:**
> Sleep-wake rhythms are coordinated by the **SCN in the hypothalamus**, gated by the **thalamus**, and promoted or suppressed via the **reticular formation** and **cortical activity**.
55
brain waves and discuss their relationship to mental states
- **Alpha waves (8–13 Hz)**
→ Awake and relaxed with eyes closed; suppressed when eyes open or during mental activity
- **Beta waves (14–30 Hz)**
→ Alert and focused; seen with eyes open and during mental tasks or sensory stimulation
- **Theta waves (4–7 Hz)**
→ Seen in drowsy or sleeping adults; may appear in awake individuals under emotional stress
- **Delta waves (<3.5 Hz, high amplitude)**
→ Present during deep sleep in adults
56
stages of sleep, their relationship to the brain waves, and the neural mechanisms of sleep
- **Non rem sleep**: is the non-dreaming, slow-wave phase of sleep that includes light (theta) to deep stages (delta), supporting restoration and memory
- **REM Sleep**: Rapid eye movement, vivid dreams, increased brain activity; EEG resembles **beta waves (14–30 Hz)**. Sleeper is harder to arouse than during any other stage. Sleep paraylsis si strong. Parasympathetic activation causes penile/clitoral erection and constriction of pupiles.
**Memory**
- non-REM: declarative memory consolidation and synaptic homeostasis
- REM: emotional memory processing and stress regulation
- **Neural mechanisms**:
→ **Suprachiasmatic nucleus (SCN)** of hypothalamus controls circadian rhythm
→ **Pineal gland** releases melatonin
→ **Reticular formation** and **hypothalamus** regulate sleep-wake transitions
→ **Orexin** from hypothalamus promotes wakefulness; loss → narcolepsy
57
Describe the development of brain regions from embryonic vesicles and their associated ventricle
- **Forebrain (prosencephalon)**
→ Telencephalon → Cerebrum → Lateral ventricles
→ Diencephalon → Diencephalon → Third ventricle
- **Midbrain (mesencephalon)**
→ Mesencephalon → Midbrain → Cerebral aqueduct
- **Hindbrain (rhombencephalon)**
→ Metencephalon → Cerebellum and Pons → Fourth ventricle
→ Myelencephalon → Medulla oblongata → Fourth ventricle
- **Spinal cord**
→ Hollow portion becomes the **central canal**
58
Suprachiasmatic nucleus
**Location:**
In the hypothalamus, directly above the optic chiasm
**Function:**
Acts as the master biological clock
Synchronizes circadian rhythms with the light–dark cycle (external cues)
**Pathway**
1. Retinal ganglion cells activated by light -> active SCN
2. SCN inhibits pineal gland suppressing melatonin secretion -> promotes wakefulness and alertness
3. When light is absent SCN is not active, does not suppress pineal gland -> melatonin secreted.
59
Orexins
- Neuropeptides produced by neurons in the lateral hypothalamus
- Promote wakefulness, alertness, and appetite
- Stimulate the reticular formation and cerebral cortex to maintain arousal
- Loss of orexin → **narcolepsy** with cataplexy
Regulation and light/dark connection:
- The suprachiasmatic nucleus (SCN) indirectly regulates orexin neurons
- In light (daytime), SCN promotes arousal → orexin activity increases
- In darkness (night), SCN reduces arousal → orexin activity decreases
- Orexin levels are also influenced by energy balance, stress, and sleep need
Reticular formation:
- Orexin activates the reticular formation, a brainstem network that regulates wakefulness, consciousness, and muscle tone
60
Adenosine
- A **neuromodulator** and **byproduct of ATP metabolism**
- Builds up in the brain during **wakefulness** as a result of **cellular activity**
---
**Functions:**
1. Promotes **sleep pressure** – increases the drive to sleep the longer you're awake
2. Binds to **adenosine receptors** (A1, A2A), especially in the **basal forebrain**
3. **Inhibits arousal systems** and activates sleep-promoting regions
4. **Cleared during sleep** – adenosine levels fall, helping restore alertness
---
**Clinical Insight:**
- **Caffeine** is an **adenosine receptor antagonist**
→ Blocks adenosine's action, preventing inhibition of wake-promoting neurons
→ Temporarily promotes alertness
61
Cerebral White Matter Tracts
1. **Projection tracts**
- Extend **vertically** between the cerebral cortex and **lower brain regions**, brainstem, or spinal cord
- Only tracts that **leave or enter the cortex**
- Involved in **motor output** (e.g., corticospinal tract) and **sensory input**
- **Neurons**: Primarily **pyramidal neurons** in the motor cortex and ascending sensory neurons
2. **Commissural tracts**
- Connect **left and right hemispheres** to allow interhemispheric communication
- Cross through structures like the **corpus callosum** (largest), anterior and posterior commissures
- **Neurons**: Pyramidal neurons
3. **Association tracts**
- Connect different regions **within the same hemisphere**
- Pyramidal neurons (long fibers) + stellate/interneurons (short fibers)
-
- Support intra-hemispheric integration of sensory, motor, and cognitive information
- **Neurons**: Interneurons coordinating signals within one hemisphere
62
Sites of neural integration in cerebrum
- All **neural integration** occurs in **gray matter**
- Gray matter in the cerebrum is found in three main locations:
1. **Cerebral cortex**
→ The outer layer of the cerebrum
→ 90% is **neocortex** – a six-layered structure with a relatively recent evolutionary origin
→ Primary site for conscious perception, thought, and decision-making
2. **Basal nuclei**
→ Deep gray matter involved in **motor control**, **habit formation**, and **emotional regulation**
3. **Limbic system**
→ Involved in **emotion**, **memory**, and **motivation**
→ Includes structures like the hippocampus and amygdala
63
Principle cells in cerebral cortex
1. **Stellate cells**
- Small, star-shaped cells with dendrites projecting in all directions
- Function: **Receive and process sensory input locally**
- Do **not** send signals out of the cortex
- Important in **association tracts** (within the same hemisphere)
2. **Pyramidal cells**
- Large, cone-shaped neurons with long apical dendrites and many spiny branches
- Function: Serve as **output neurons** of the cerebral cortex
- The **only cortical neurons that send axons to other parts of the CNS**
- Involved in **projection tracts** (to brainstem/spinal cord) and **commissural tracts** (to opposite hemisphere)
64
Sematotopy
There is a point-for-point correspondence between an area of body and an area of CNS
65
Sensory Relay Through Spinal Cord
- Sensory information from the body travels to the brain via **ascending tracts** in the spinal cord. Also called **somatosensory tracts**
- Different tracts carry **specific types of sensation**
---
**Examples of Afferent Tracts:**
- **Posterior column** (gracile & cuneate fasciculi): fine touch, vibration, proprioception
- **Anterolateral system** (spinothalamic tract): pain, temperature, crude touch
- **Spinocerebellar tracts**: unconscious proprioception → cerebellum
---
**Decussation (Crossing Over):**
- Most sensory axons **cross sides** in the CNS
- **Posterior column**: decussates in the **medulla oblongata**
- **Spinothalamic tract**: decussates in the **spinal cord**
→ Explains why lesions often cause **contralateral sensory loss**
---
**Three-Order Neuron Pathway:**
1. **First-order**: receptor → spinal cord or brainstem
2. **Second-order**: crosses midline → thalamus
3. **Third-order**: thalamus → **primary somatosensory cortex**
66
Motor Output
1. **Motor intention** begins in the **motor association areas** of the frontal lobe
2. These regions generate a **motor plan**
→ Specifies the sequence and strength of muscle contractions
3. The motor plan is sent to **pyramidal cells** in the **primary motor cortex (precentral gyrus)**
→ These are **upper motor neurons**
→ Axons descend through the brainstem; most **decussate in the medulla** and form the **lateral corticospinal tracts**
4. Upper motor neurons **synapse with lower motor neurons** in the **anterior horn** of the spinal cord
5. **Lower motor neurons** send axons to **skeletal muscles**, producing voluntary movement
---
**Modulation of Movement:**
- The basal nuclei, cerebellum, and substantia nigra fine-tune motor signals
→ Ensure movements are smooth, coordinated, and appropriately scaled. Substantia nigra is essential for scaling, initiating, and modulating movement — particularly through dopaminergic control of basal nuclei output.
```
Dorsal horn (posterior)
Receives sensory input from afferent (incoming) fibers
Contains interneurons that process touch, pain, temperature, proprioception
Ventral horn (anterior)
Contains somatic motor neurons
Sends efferent fibers to skeletal muscles (voluntary motor control)
Lateral horn (only in T1–L2 and S2–S4)
Contains autonomic motor neurons:
T1–L2 → sympathetic preganglionic neurons\
S2–S4 → parasympathetic preganglionic neurons
```
67
Role of Basal nuclei in movement
major components involved in movement:
- **Caudate nucleus**
- **Putamen**
- **Globus pallidus**
→ Together, these regulate motor output via direct and indirect pathways
Key functions:
1. Initiate and terminate intentional movements
2. Involved in automatic, learned motor patterns (e.g., walking, typing)
3. Part of a feedback loop: cerebrum → basal nuclei → thalamus → back to cerebrum
→ Helps refine motor output and suppress unwanted movement
Substantia nigra (midbrain) → functionally part of basal nuclei circuitry
- Releases dopamine to modulate striatal activity
- Degeneration → Parkinson’s disease
clinical note – dyskinesias:
- Movement disorders from basal nuclei damage -> **dyskinesias**
→ Involuntary movements, tremors, or impaired initiation
68
Basal Nuclei
- Masses of gray matter embedded in white matter of the cerebrum
- Located inferior to the lateral ventricles and lateral to the thalami
---
**Motor-related basal nuclei**
(Mainly involved in movement and habit formation)
- **Caudate nucleus**
- **Putamen**
- **Globus pallidus**
Functions:
- Initiate and terminate voluntary movements
- Regulate skeletal muscle tone and subconscious motor control
- Coordinate learned movement patterns (e.g., walking, writing)
- Contribute to learning new motor skills through practice and repetition
- Integrate and relay motor signals from the cerebral cortex
- Communicate with the substantia nigra (midbrain) and motor cortex
- Putamen plays a key role in the later stages of habit formation, when behaviors become automatic
---
**Limbic-related basal nucleus**
(Links motivation and emotion to action)
- **Nucleus accumbens** (part of the ventral striatum)
Functions:
- Involved in reward, motivation, and goal-directed behavior
- Active during early stages of habit formation, driven by reward and reinforcement
- Receives input from the amygdala, hippocampus, and orbitofrontal cortex
- Considered a **limbic–motor interface**
---
Summary:
The **caudate, putamen, and globus pallidus** support motor control and habit execution,
while the **nucleus accumbens** integrates **reward and emotion** to drive behavior.
69
Role of Cerebellum in movement
1. Maintains **motor coordination** and timing
2. Aids in **learning motor skills** (e.g., playing an instrument, riding a bike)
3. Regulates **muscle tone** and **posture** (RA and basal nuclei also involved)
4. **Smooths muscle contractions** for fluid motion
5. Coordinates **eye and body movements**
6. Synchronizes movements across **multiple joints**
---
**Ataxia**
- Poor coordination, balance, and timing of movements
- Movements are clumsy, unsteady, or inaccurate
70
Association Areas for language
1. **Wernicke’s area** – Left temporal and parietal lobes
- Permits **recognition of spoken and written language**
- Creates a **plan of speech**
2. **Broca’s area** – Left lateral frontal lobe
- Generates **motor program** for speech muscles
- Sends instructions to **primary motor cortex** for execution
3. **Right hemisphere counterparts**
- Mirror Wernicke’s and Broca’s areas
- Process **emotional tone** and **affective meaning** of speech
---
**Clinical Notes:**
- **Wernicke’s aphasia**: Fluent but meaningless speech; poor comprehension
- **Broca’s aphasia**: Slow, effortful speech; difficulty forming words. comprehension is generally preserved. Difficulty with complex grammar, especially syntactically demanding sentences
- **Anomic aphasia**: Normal comprehension and speech; impaired object naming. Anomic aphasia is usually caused by damage to the left temporal or parietal lobes, especially areas involved in word retrieval like the angular gyrus -> associated with Wernicke's area
71
Cerebral Lateralization
Difference in the structure and function of the cerebral hemispheres
**Left Hemisphere**
- usually the categorical hemisphere: specializes in spoken and written language, sequential and analytical reasoning, breaks information into fragments and analyzes it
**Right Hemisphere**
- Usually the representational hemisphere. Perceives information in a more integrated way. Seat of imagination and insight, musical and artistic skill, perception of patterns and spatial relationships, comparison of sights, sounds, smells and taste
72
Cranial Nerve 1
- olfactory
- sensory
- Origin: Olfactory epithelium
- Function: Smell
- Damage: Loss of smell
73
Cranial Nerve 2
**Optic Nerve**
*El nervio óptico*
- Sensory
- Origin: Retina
- Function: Vision
- Damage: blindness in part or all of visual field
74
Cranial Nerve 3
**Oculomotor**
*El nervio oculomotor*
- Motor
- Origin: Midbrain
- Function: Controls muscles of the eye
- Damage: Dropping eyelid, dilated pupil, double vision, difficulty focusing, inability to move eye in certain directions
```
levator palpebrae superioris (lifts upper eyelid)
parasympathetic fibers to the pupil (constriction) and lens (accommodation).
superior rectus,
inferior rectus,
inferior oblique,
medial rectus
```
75
Cranial Nerve 4
**Trochlear Nerve**
*El nervio troclear*
- Motor
- Origin: Midbrain
- Function: Controls the superior oblique muscle
→ Moves the eye downward and inward rotation (internal rotation)
- Damage: Causes double vision and difficulty moving the eye down and inward (especially when reading or going downstairs)
76
Cranial Nerve 5
**Trigeminal Nerve**
*El nervio trigémino*
- Mixed
- Origin: Pons, Mouth
- Function:
Sensory: touch, temperature, pain on face
Motor: muscles of jaw
Most important sensory nerve of the face. Has three divisions
77
Cranial Nerve 6
**Abducens**
*El nervio abducens*
- Motor
- Origin: Pons
- Function: Muscles of the eyeball - lateral rectus
- Damage - inability to rotate eye laterally, and at rest, eye rotate medially
*The abducens nerve emerges from the brainstem at the junction of the pons and medulla oblongata, specifically: Medially, between the pyramids (medial) and the pons (superior)*
78
Cranial Nerve 7
**Facial Nerve**
*El nervio facial*
- Mixed
- Origin: Taste buds, pons
Sensory Function: Taste (anterior 2/3rds of tongue)
Motor Function: Facial muscles, facial expressions, salivary, tear, nasal and palatine glands
- Damage: saggy muscles and disturbed sense of taste - no sweet and salty
79
Cranial Nerve 8
**Vestibulocochlear**
*El nervio vestibulococlear*
- Sensory
- Origin: Inner ear
- Function: Hearing and equilibrium
- Damage: Deafness, dizziness, nausea, loss of balance, nystagmus (involuntary rhythmic oscillation of eyes)
*cochlear -> cóclea -> caracol*
80
Cranial Nerve 9
**Glossopharyngeal**
- Mixed
- Origin: Tongue, medulla
- Sensory Function: Tongue sensations, including taste buds (posterior 1/3 of tongue)
- Motor: Swallowing, salivary glands
- Damage results in loss of bitter and sour taste, impaired swallowing
```
"Glosso-" means tongue (from Greek glossa)
"Pharyngeal" refers to the pharynx (throat)
```
81
Cranial Nerve 10
**Vagus Nerve**
*el nervios vago*
- Mixed
- Origin: Medulla
- Sensory Function: pharynx, internal viscera
- Motor function: Involuntary motor functions of heart, lungs, digestive tract etc.
- Major role in autonomic nervous system -> control of cardiac, pulmonary, digestive and urinary function. Swallowing, speech, regulation of viscera
- Damage: hoarseness of loss of voice, impaired swallowing. Fatal if damage to both
82
Cranial Nerve 11
**Accessory Nerve**
*El nervio accesorio / el undécimo par craneal*
- Motor
- Origin: Upper spinal cord
- Function: Swallowing head, neck, and shoulder movement
- Damage: impaired head, neck and shoulder movement - head will turn towards injured side
83
Cranial Nerve 12
**Hypoglossal**
- Motor
- Origin: Medulla
- Function: Tongue movements for speech, food manipulation, and swallowing
-Damage: if one side is damaged, tongue deviates towards injured side. If both are damaged, then cannot protrude tongue.
*The hypoglossal nerve (CN XII) emerges anterior to the vagus nerve (CN X) in relation to the olive.*
84
To throw a ball
1. **Intention and planning**
- **Prefrontal cortex**: decides to throw; selects goal and strategy
- **Premotor cortex & SMA**: plan the sequence, muscle groups, and timing
2. **Motor command initiation**
- **Primary motor cortex**: sends motor signals via corticospinal tract to activate hand and arm muscles
3. **Postural control and movement stabilization**
- **Basal nuclei**: initiate movement and suppress unwanted activity
- **Reticular formation**: maintains posture and balance during the throw
4. **Coordination and timing**
- **Cerebellum**: adjusts force, timing, and smoothness of movement
5. **Sensory feedback and correction**
- **Somatosensory cortex**: monitors arm position through proprioceptive input
- **Cerebellum**: compares actual vs intended movement and makes real-time adjustments
85
To catch a ball
1. **Visual detection and tracking**
- **Primary visual cortex** (occipital lobe): detects the ball in motion
- **Dorsal visual stream** (parietal lobe): tracks the ball’s location, speed, and direction
2. **Spatial awareness and prediction**
- **Posterior parietal cortex**: integrates visual input with spatial awareness and predicts hand placement
- **Cerebellum**: times muscle activation to intercept the ball precisely
3. **Motor planning**
- **Premotor cortex & SMA**: prepare reaching and grasping motion based on predicted trajectory
4. **Motor execution**
- **Primary motor cortex**: sends motor commands to activate arm and hand muscles
- **Spinal cord and peripheral nerves**: carry out muscle activation for movement
5. **Grip and sensory feedback**
- **Somatosensory cortex**: detects contact and pressure from the ball
- **Cerebellum & basal nuclei**: adjust grip strength and coordinate motor refinement during the catch
86
Comissures
- **Corpus callosum**:
→ Largest commissure; connects left and right cerebral cortices
→ Transfers motor, sensory, and cognitive information
→ Coordinates bilateral motor activity, language, and perception
→ **Damage**: disconnection syndromes (e.g., split-brain); left and right hemispheres cannot share information → may cause inability to name objects seen in the left visual field
- **Anterior commissure**:
→ Connects temporal lobes, especially amygdalae and olfactory cortices
→ Transfers olfactory, limbic, and emotional pain-related information
→ **Damage**: subtle deficits in olfaction and emotional memory; reduced pain-related emotional response
- **Posterior commissure**:
→ Connects pretectal areas of the midbrain
→ Mediates the pupillary light reflex between eyes (consensual response)
→ **Damage**: loss of consensual pupillary light reflex; pupils may not constrict together
- **Hippocampal commissure** (commissure of the fornix):
→ Connects the left and right hippocampi
→ Supports memory consolidation and bilateral memory integration
→ **Damage**: impaired coordination of memory across hemispheres; may affect spatial and episodic memory formation
87
Compare movement regulation
- **Reticular formation**:
Maintains baseline **muscle tone** and controls **automatic posture and gross motor coordination** via reticulospinal tracts
- **Substantia nigra**:
Modulates **basal nuclei activity** through dopamine release; influences **muscle tone** and **movement initiation**
- **Basal nuclei**:
Plan, initiate, and **suppress unwanted movement**; regulate **muscle tone** and contribute to **habitual motor patterns**
- **Cerebellum**:
Coordinates **timing, force, and precision** of movements; regulates **muscle tone** and maintains **balance and posture**
